technical field

[0001] The present invention relates to a hydraulic drive system for work machinery, specifically to a hydraulic drive system for work machinery such as hydraulic excavators with a regeneration circuit, wherein the regeneration circuit reuses (regenerates) hydraulic oil discharged from a hydraulic actuator to drive other actuators through the inertia energy of the driven component (such as the boom) such as its own weight falling.

Background technology

[0002] A hydraulic drive system for a work machine is known, which has a regeneration circuit such as an arm cylinder for regenerating hydraulic oil discharged from a slave arm cylinder through the self weight of the boom. This example is described in Patent Documents I and 2. In the hydraulic drive system described in Patent Document I, when the discharge oil from the bottom oil chamber of the automatic arm cylinder is regenerated to the arm cylinder in the future, the discharge flow rate of the hydraulic cylinder supplying hydraulic oil to the arm cylinder is correspondingly reduced, in order to improve the fuel efficiency of the engine.

[0003] In addition, in the hydraulic drive system described in Patent Document 2, after determining that the predetermined conditions are met, the discharged oil from the cylinder bottom side oil chamber of the automatic arm cylinder is regenerated to the arm cylinder through the intermediate bypass oil passage, thereby avoiding the enlargement and complexity of the hydraulic circuit.

summary of the invention

[0008] In the hydraulic drive system of Patent Document I, the regeneration of hydraulic oil from the cylinder bottom side oil chamber of the boom cylinder to the arm cylinder is correspondingly reduced to improve fuel efficiency by reducing the discharge flow rate of the hydraulic cylinder, thus achieving energy conservation. However, there is a problem of deteriorating installation performance and increasing production costs for the operating machinery due to the need to control the electromagnetic proportional valves of the regeneration valve and the outlet throttle valve.

On the other hand, in the hydraulic drive system of Patent Document 2, since it is composed of an electromagnetic proportional valve, such a problem does not arise.

[0010] However, in the hydraulic drive system of Patent Document 2, when the prescribed conditions are not met and regeneration is not performed, the flow rate of the discharged oil from the cylinder bottom side oil chamber of the boom cylinder is adjusted through a flow control valve. On the other hand, when the conditions are met, the discharged oil from the cylinder bottom side oil chamber of the boom cylinder is supplied to the intermediate bypass oil passage through other flow control valves in addition to the aforementioned flow control valve. Therefore, in the case of regeneration, compared to the case without regeneration, the flow rate of discharged oil increases, and the piston rod speed of the boom cylinder may increase. The increase in piston rod speed of the boom cylinder may cause a sense of operational inconsistency between the situation where regeneration is performed and the situation where regeneration is not performed for the operator.

[0011] The present invention is developed based on the above situation, and its purpose is to provide a hydraulic drive system for a work machine, which is composed of an electromagnetic proportional valve (electric drive device) for a regeneration circuit, and can ensure the same actuator speed when regenerating hydraulic oil discharged from the hydraulic actuator to the drive of other hydraulic actuators and when not regenerating.

[0012] In order to achieve the above objectives, the first invention is a hydraulic drive system for a work machine, comprising: a hydraulic chestnut device; The I-th hydraulic actuator is driven by hydraulic oil supplied from the aforementioned hydraulic chestnut device to drive the I-th driven body; The second hydraulic actuator is driven by hydraulic oil supplied from the aforementioned hydraulic cylinder device to drive the second driven body; An I-th flow control device that controls the flow of hydraulic oil supplied from the hydraulic chestnut device to the I-th hydraulic actuator; A second flow control device that controls the flow of hydraulic oil supplied from the hydraulic cylinder device to the second hydraulic actuator; Output an operation signal indicating the action of the I-th driven body and switch the I-th operation device of the I-th flow adjustment device; A second operating device that outputs an operation signal indicating the action of the second driven body and switches the second flow control device, wherein the first hydraulic actuator is a hydraulic cylinder that discharges hydraulic oil from the cylinder bottom side oil chamber and sucks hydraulic oil from the piston rod side oil chamber through the self weight of the first driven body when operating the first operating device in the self weight direction of the first driven body. In the hydraulic drive system of the working machine, there is a regeneration passage that connects the cylinder bottom side oil chamber of the hydraulic cylinder between the hydraulic cylinder and the second hydraulic actuator; A regeneration flow adjustment device that supplies at least a portion of the hydraulic oil discharged from the cylinder bottom side oil chamber of the hydraulic cylinder through the regeneration passage after adjusting the flow rate to between the hydraulic cylinder device and the second hydraulic actuator; A discharge flow adjustment device that discharges at least a portion of the hydraulic oil discharged from the bottom side oil chamber of the hydraulic cylinder to the oil tank after adjusting the flow rate; An electrical drive device that simultaneously controls the regeneration flow adjustment device and the discharge flow adjustment device; And the control device, regardless of the amount of regeneration flow adjusted by the regeneration flow adjustment device, outputs control commands to the electrical drive device in such a way that the falling speed of the I-th driven body becomes the same.

[0013] Invention Effect

[0014] According to the present invention, it is possible to ensure the same actuator speed when regenerating the hydraulic oil discharged from the hydraulic actuator to the drive of other hydraulic actuators and without regeneration, and an electromagnetic proportional valve (electric drive device) for the regeneration circuit can be composed of an electromagnetic proportional valve. As a result, good operability can be achieved, and cost reduction and installation improvement can be achieved.

Specific implementation method

[0024] Below, the embodiments of the hydraulic drive system of the working machine of the present invention will be illustrated using the accompanying drawings.

[0025] Example 1

[0026] Figure 1 is a schematic diagram showing the control system of the hydraulic drive system of the first embodiment of the working machine of the present invention.

[0027] In Figure 1, the hydraulic drive system of this embodiment includes a chestnut device 50 including a main hydraulic chestnut I and a pilot chestnut 3; The boom cylinder 4 (I-th hydraulic actuator) of the boom 205 (refer to Figure 2) of the hydraulic excavator, which is driven by hydraulic oil supplied from the hydraulic cylinder I and serves as the I-th driven body; The arm cylinder 8 (second hydraulic actuator) of the arm 206 (refer to Figure 2) of the hydraulic excavator, which is driven by hydraulic oil supplied from the hydraulic cylinder I and serves as the second driven body; Control valve 5 (I-th flow control device) that controls the flow (flow rate and direction) of hydraulic oil supplied from hydraulic cylinder I to boom cylinder 4; Control valve 9 (second flow control device) that controls the flow (flow rate and direction) of hydraulic oil supplied from hydraulic cylinder I to arm cylinder 8; Output the action command of the boom and switch the I-th operating device 6 of the control valve 5; The second operating device 10 that outputs the action command of the boom and switches the control valve 9. The hydraulic cylinder I is also connected to a control valve (not shown) in order to supply hydraulic oil to other actuators (not shown), but this circuit part is omitted.

[0028] The hydraulic cylinder I is a variable capacity type with a regulator la. The regulator la is controlled by a control signal from controller 27 (described later), thereby controlling the tilt angle (capacity) of the hydraulic cylinder I and controlling the discharge flow rate. In addition, although not shown, the regulator Ia has a torque control unit that, as is well known, derives the discharge pressure of the hydraulic cylinder I and limits the tilt angle (capacity) of the hydraulic cylinder I so that the absorbed torque of the hydraulic cylinder I does not exceed a predetermined maximum torque. Hydraulic cylinder I is connected to control valves 5 and 9 through hydraulic oil supply lines 7a and IIa, and the discharge oil of hydraulic cylinder I is supplied to control valves 5 and 9.

[0029] As flow control devices, control valves 5 and 9 are connected to the cylinder bottom side oil chambers or piston rod side oil chambers of boom cylinder 4 and stick cylinder 8 through cylinder bottom side pipelines 15 and 20 or piston rod side pipelines 13 and 21, respectively. According to the switching position of control valves 5 and 9, the discharged oil of hydraulic cylinder I is supplied from control valves 5 and 9 to the cylinder bottom side oil chambers or piston rod side oil chambers of boom cylinder 4 and stick cylinder 8 through cylinder bottom side pipelines 15 and 20 or piston rod side pipelines 13 and 21. At least a portion of the hydraulic oil discharged from the boom cylinder 4 flows back to the oil tank through the oil tank pipeline 7b from the control valve 5. All hydraulic oil discharged from stick cylinder 8 flows back to the tank through control valve 9 via tank line Ilb.

[0030] In addition, in this embodiment, the flow control device for controlling the flow (flow rate and direction) of hydraulic oil supplied from hydraulic cylinder I to each hydraulic actuator 4, 8 is illustrated as an example, but it is not limited to this. The flow adjustment device can be a structure that supplies through multiple valves, or a structure that supplies and discharges through different valves.

[OO3 Z6;] The first and second operating devices 6, 10 have operating rods 6a, 1a and pilot valves 6b, 10b, respectively. The pilot valves 6b, 1b are connected to the operating parts 5a, 5b of the control valve 5 and the operating parts 9a, 9b of the control valve 9 through pilot pipelines 6c, 6d and 10c, 1d, respectively.

[0032] When the operating rod 6a is operated in the boom lifting direction BU (to the left in the figure), the pilot valve 6b generates an operating pilot pressure Pbu corresponding to the operation amount of the operating rod 6a. This operating pilot pressure Pbu is transmitted to the operating part 5a of the control valve 5 through the pilot pipeline 6c, and the control valve 5 is switched to the boom lifting direction (to the right in the figure). When the operating rod 6a is operated in the direction of boom descent BD (to the right in the figure), the pilot valve 6b generates an operating pilot pressure Pbd corresponding to the amount of operation of the operating rod 6a. This operating pilot pressure Pbd is transmitted to the operating part 5b of the control valve 5 through the pilot pipeline 6d, and the control valve 5 is switched to the direction of boom descent (to the left in the figure).

[0033] When the operating rod 1a is operated in the direction of arm recovery AC (to the right in the figure), the pilot valve 1b generates an operating pilot pressure Pac corresponding to the amount of operation of the operating rod 1a. This operating pilot pressure Pac is transmitted to the operating part 9a of the control valve 9 through the pilot pipeline 1c, and the control valve 9 is switched to the direction of arm recovery (to the left in the figure). When the operating rod 1a is operated in the direction AD (left side in the figure) of the arm release, the pilot valve 1b generates an operating pilot pressure Pad corresponding to the operation amount of the operating rod 1a. This operating pilot pressure Pad is transmitted to the operating part 9b of the control valve 9 through the pilot pipeline 1d, and the control valve 9 is switched to the arm release direction (position on the right side in the figure).

[0034] Compensated overload relief valves 12 and 19 are respectively connected between the cylinder bottom side pipeline 15 and the piston rod side pipeline 13 of the boom cylinder 4, and between the cylinder bottom side pipeline 20 and the piston rod side pipeline 21 of the stick cylinder 8. The overload relief valves 12 and 19 with compensation have the function of preventing damage to hydraulic circuit equipment caused by excessive pressure in the cylinder bottom side pipelines 15 and 20 and the piston rod side pipelines 13 and 21, and reducing the work of cavitation caused by negative pressure in the cylinder bottom side pipelines 15 and 20 and the piston rod side pipelines 13 and 21.

[0035] In addition, this embodiment is a case where the chestnut device 50 includes one main chestnut (hydraulic chestnut I), but it is also possible that the chestnut device 50 includes multiple (e.g. two) main chestnuts, and each main chestnut is connected to control valves 5 and 9, supplying hydraulic oil from each main chestnut to the boom cylinder 4 and the arm cylinder 8.

[0036] Figure 2 is a side view of a hydraulic excavator according to the first embodiment of the hydraulic drive system equipped with the working machine of the present invention.

[0037] The hydraulic excavator has a lower traveling body 201, an upper rotating body 202, and a front working machine 203. The lower traveling body 201 has left and right track type traveling devices 201a, 201a (only one side is shown), which are driven by left and right traveling motors 201b, 201b (only one side is shown). The upper rotating body 202 is mounted on the lower traveling body 201 in a rotatable manner and is driven to rotate by a rotary motor 202A. The front work machine 203 can be installed in a pitching manner at the front of the upper rotating body 202. On the upper rotating body 202, there is an operating chamber (driver's cab) 20.2, in which the aforementioned first and second operating devices 6 and 10, as well as an operating pedal device for travel (not shown) and other operating devices are arranged.

[0038] The front working machine 203 is a multi joint structure with a boom 205 (the first driven body), an arm 206 (the second driven body), and a bucket 207. The boom 205 rotates in the up-down direction relative to the upper rotating body 202 through the extension and contraction of the boom cylinder 4, the arm 206 rotates in the up-down and front back directions relative to the boom 205 through the extension and contraction of the arm cylinder 8, and the bucket 207 rotates in the up-down and front back directions relative to the boom 206 through the extension and contraction of the arm cylinder 208.

[0039] In Figure 1, the circuit parts related to hydraulic actuators such as the left and right travel motors 201b and 201b, the rotary motor 202A, and the bucket cylinder 208 are omitted and shown.

[0040] Here, boom cylinder 4 is a hydraulic cylinder that discharges hydraulic oil from the cylinder bottom side oil chamber and sucks hydraulic oil from the piston rod side oil chamber when operating the operating rod 6a of the I-th operating device 6 in the direction of boom descent (the self weight descent direction of the I-th driven body) BD based on the self weight of the front working machine 203, including the boom 205.

[0041] Returning to Figure 1, the hydraulic drive system of the present invention further includes a two position three-way regeneration control valve 17, which is configured on the cylinder bottom side pipeline 15 of the boom cylinder 4 and can adjust the flow distribution of hydraulic oil discharged from the cylinder bottom side oil chamber of the boom cylinder 4 to the control valve 5 side (tank side) and the hydraulic oil supply pipeline Ila side (regeneration passage side) of the arm cylinder 8, based on the above structural elements; Regeneration passage 18, one end of which is connected to an outlet port of regeneration control valve 17 and the other end of which is connected to hydraulic oil supply line IIa; Connect passage 14, which branches off from the cylinder bottom side pipeline 15 and the piston rod side pipeline 13 of the boom cylinder 4, and connects the cylinder bottom side pipeline 15 and the piston rod side pipeline 13; The communication control valve 16 is configured on the communication passage 14 and opens based on the operation pilot pressure Pbd (operation signal) of the boom lowering direction BD of the first operating device 6. It supplies a portion of the discharged oil from the cylinder bottom side oil chamber of the boom cylinder 4 to the piston rod side oil chamber of the boom cylinder 4 in a regenerative manner, and communicates the cylinder bottom side oil chamber of the boom cylinder 4 with the piston rod side oil chamber, thereby preventing negative pressure from being generated in the piston rod side oil chamber; Electromagnetic proportional valve 22; Pressure sensors 23, 24, 25, 26; And controller 27.

[0042] Regeneration control valve 17 has a tank side passage (first throttle valve) and a regeneration side passage (second throttle valve) in order to allow the discharged oil from the cylinder bottom side oil chamber of boom cylinder 4 to flow towards the tank side (control valve 5 side) and the regeneration passage 18 side. The stroke of regeneration control valve 17 is controlled by an electromagnetic proportional valve 22 (electric drive device). The other outlet port of regeneration control valve 17 is connected to the port of control valve 5. In this embodiment, the regeneration control valve 17 constitutes a regeneration flow rate adjustment device and a discharge flow rate adjustment device, wherein the regeneration flow rate adjustment device supplies at least a part of the hydraulic oil discharged from the cylinder bottom side oil chamber of the boom cylinder 4 through the regeneration passage 18 after adjusting its flow rate to between the hydraulic cylinder I and the arm cylinder 8, and the discharge flow rate adjustment device discharges at least a part of the hydraulic oil discharged from the cylinder bottom side oil chamber of the boom cylinder 4 to the oil tank after adjusting its flow rate.

[0043] The communication control valve 16 has an operating part 16a, which opens the valve by transmitting the operation pilot pressure Pbd of the boom lowering direction BD of the I-th operating device 6 to the operating part 16a.

[0044] Pressure sensor 23 is connected to pilot line 6d to detect the operation pilot pressure Pbd of the boom lowering direction BD of the I-th operating device 6. Pressure sensor 25 is connected to the cylinder bottom side pipeline 15 of boom cylinder 4 to detect the pressure in the cylinder bottom side oil chamber of boom cylinder 4. Pressure sensor 26 is connected to the hydraulic oil supply pipeline Ila on the arm cylinder 8 side to detect the discharge pressure of hydraulic cylinder I. The pressure sensor 24 is connected to the pilot line 1d of the second operating device 10 to detect the operation pilot pressure Pad in the direction of releasing the arm of the second operating device 10.

[0045] Controller 27 inputs detection signals 123, 124, 125, 126 from pressure sensors 23, 24, 25, 26, performs prescribed operations based on these signals, and outputs control commands to electromagnetic proportional valve 22 and regulator Ia.

[0046] As an electrical driving device, the electromagnetic proportional valve 22 operates according to control instructions from the controller 27. The electromagnetic proportional valve 22 converts the primary pressure of the hydraulic oil supplied from the pilot cylinder 3 as the pilot hydraulic source into the desired pressure (secondary pressure) and outputs it to the operating unit 17a of the regeneration control valve 17, controlling the stroke of the regeneration control valve 17 and thus controlling the opening degree (opening area).

[0047] Figure 3 is a characteristic diagram showing the opening area characteristics of the regeneration control valve of the hydraulic drive system constituting the first embodiment of the working machine of the present invention. The horizontal axis of Figure 3 shows the slide stroke of regeneration control valve 17, and the vertical axis shows the opening area.

[0048] In Figure 3, when the slide valve stroke is minimized (in the original position), the oil tank side passage is open with the largest opening area, and the regeneration side passage is closed with zero opening area. As the stroke gradually increases, the opening area of the fuel tank side passage gradually decreases, while the regeneration side passage opens and the opening area gradually increases. When the stroke is further increased, the fuel tank side passage is closed (the opening area becomes zero), and the opening area of the regeneration side passage is further increased. The result of this configuration is that, in the case where the slide valve stroke is minimized, the hydraulic oil discharged from the bottom side oil chamber of the boom cylinder 4 will not regenerate and will flow entirely into the control valve 5 side. As the stroke gradually moves to the right, a portion of the hydraulic oil discharged from the bottom side oil chamber of the boom cylinder 4 will flow into the regeneration passage 18. In addition, by adjusting the stroke, the opening area of the fuel tank side passage and the regeneration side passage 18 can be changed, thereby controlling the regeneration flow rate.

[0049] Next, an overview of the action when only the boom is lowered will be explained.

[0050] In Figure 1, when the operating rod 6a of the I-th operating device 6 is operated in the downward direction BD of the boom, the operating pilot pressure Pbd generated from the pilot valve 6b of the I-th operating device 6 is input to the operating portion 5b of the control valve 5 and the operating portion 16a of the communication control valve 16. As a result, the control valve 5 is switched to the left position shown in the diagram, and the cylinder bottom pipeline 15 is connected to the oil tank pipeline 7b. As a result, hydraulic oil is discharged from the cylinder bottom side oil chamber of the boom cylinder 4 to the oil tank, and the piston rod of the boom cylinder 4 performs a shortening action (boom lowering action). At this point, cut off the piston rod side pipeline 13 from the hydraulic oil supply pipeline Ila.

[0051] Furthermore, by switching the communication control valve 14 to the communication position on the lower side of the diagram, the cylinder bottom side pipeline 15 of the boom cylinder 4 is connected to the piston rod side pipeline 13, and a portion of the discharged oil from the cylinder bottom side oil chamber of the boom cylinder 4 is supplied to the piston rod side oil chamber of the boom cylinder 4. Therefore, by preventing negative pressure from being generated in the piston rod side oil chamber and cutting off the supply of hydraulic oil from hydraulic cylinder I to the piston rod side oil chamber of boom cylinder 4 through the switching of control valve 5, the output of hydraulic cylinder I is suppressed and fuel consumption can be reduced.

[0052] Next, we will provide an overview of the actions taken when simultaneously lowering the boom and driving the boom. In addition, since the principle is the same when releasing the boom and when recycling, the boom release action will be taken as an example for explanation.

[0053] When the operating rod 6a of the I-th operating device 6 is operated in the boom lowering direction BD and the operating rod Ioa of the second operating device 1 is operated in the arm releasing direction AD, the operating pilot pressure Pbd generated from the pilot valve 6b of the I-th operating device 6 is input to the operating portion 5b of the control valve 5 and the operating portion 16a of the communication control valve 16. As a result, the control valve 5 is switched to the left position shown in the diagram, and the cylinder bottom pipeline 15 is connected to the oil tank pipeline 7b. As a result, hydraulic oil is discharged from the cylinder bottom side oil chamber of the boom cylinder 4 to the oil tank, and the piston rod of the boom cylinder 4 performs a shortening action (boom lowering action).

[0054] The operation pilot pressure Pad generated from the pilot valve 1b of the second operating device 10 is input to the operating section 9b of the control valve 9. As a result, the control valve 9 is switched, and the cylinder bottom pipeline 20 is connected to the oil tank pipeline Ilb, and the piston rod pipeline 21 is connected to the hydraulic oil supply pipeline 11a. Therefore, the hydraulic oil in the cylinder bottom side oil chamber of the arm cylinder 8 is discharged to the oil tank, and the discharged oil from the hydraulic cylinder I is supplied to the piston rod side oil chamber of the arm cylinder 8. As a result, the piston rod of stick cylinder 8 undergoes a shortening action.

[0055] Detection signals 123, 124, 125, and 126 from pressure sensors 23, 24, 25, and 26 are input into controller 27. Through the control logic described later, control commands are output to electromagnetic proportional valve 22 and regulator Ia of hydraulic cylinder I.

[0056] The electromagnetic proportional valve 22 generates a control pressure (secondary pressure) corresponding to the control command, and controls the regeneration control valve 17 through this control pressure. Part or all of the hydraulic oil discharged from the cylinder bottom side oil chamber of the boom cylinder 4 is supplied to the boom cylinder 8 through the regeneration control valve 17 in a regenerative manner.

[0057] The regulator Ia of the hydraulic cylinder I controls the tilt angle of the hydraulic cylinder I based on control commands and appropriately controls the flow rate of the cylinder in a way that maintains the target speed of the arm cylinder 8.

[0058] Next, the control function of controller 27 will be explained. Controller 27 roughly has the following two functions.

[0059] Firstly, when the controller 27 operates the I-th operating device 6 towards the self weight falling direction of the boom 205 (I-th driven body), i.e., the boom lowering direction BD, and simultaneously operates the second operating device 10, and the pressure in the cylinder bottom side oil chamber of the boom cylinder 4 is higher than the pressure in the hydraulic oil supply line Ila between the hydraulic cylinder I and the arm cylinder 8, the regeneration control valve 17 is switched from its original position, thereby regenerating the discharged oil from the cylinder bottom side oil chamber of the automatic arm cylinder 4 to the piston rod side oil chamber of the arm cylinder. At this time, calculate the differential pressure between the pressure in the bottom oil chamber of the boom cylinder 4 and the pressure in the hydraulic oil supply line Ila between the hydraulic cylinder I and the arm cylinder 8, and control the opening of the regeneration control valve 17 based on this differential pressure.

Specifically, when the differential pressure is low, reducing the stroke of regeneration control valve 17 reduces the opening area of the regeneration side passage and expands the opening area of the fuel tank side passage. As the differential pressure increases, expand the opening area of the regeneration side passage and reduce the opening area of the fuel tank side passage. Control is carried out by setting the opening area of the regeneration side passage to the maximum value and closing the opening on the fuel tank side when the differential pressure is greater than the fixed value. By controlling in this way, the switching shock of regeneration control valve 17 can be suppressed.

[0061] When both the boom descent operation and the stick drive are performed simultaneously, the differential pressure is small at the beginning of the action, but increases over time. Therefore, by gradually increasing the opening area of the regeneration side passage based on differential pressure, it is possible to suppress switching shock and achieve good operability.

Moreover, in the case of small differential pressure, even if the regeneration side opening is expanded, the regeneration flow rate is also small, so the speed of the piston rod of the boom cylinder may sometimes slow down. Therefore, in the case of a small differential pressure, the control is carried out by increasing the opening area of the oil tank side passage to increase the discharge flow rate from the bottom side oil chamber of the cylinder and to make the speed of the piston rod of the boom cylinder the desired speed by the operator. On the other hand, in the case of large differential pressure, the regeneration flow rate is sufficiently increased. Therefore, by reducing the opening of the oil tank side passage, the speed of the piston rod of the boom cylinder is prevented from becoming too fast.

[0063] In addition, the controller 27 controls in the following way: when controlling the regeneration control valve 17 to supply hydraulic oil from the cylinder bottom side oil chamber of the boom cylinder 4 to the hydraulic oil supply line Ila between the hydraulic cylinder I and the arm cylinder 8, the capacity of the hydraulic cylinder I is reduced correspondingly to the regeneration flow rate supplied from the cylinder bottom side oil chamber of the boom cylinder 4 to the hydraulic oil supply line IIa.

[0064] Therefore, regardless of the regeneration flow rate of the hydraulic oil, the same actuator speed (piston rod speed of boom cylinder 4) can be ensured when regenerating the hydraulic oil discharged from the hydraulic actuator to drive other hydraulic actuators and when not regenerating. The result is that the same boom descent speed can be achieved in any situation.

[0065] Figure 4 is a block diagram of the controller of the first embodiment of the hydraulic drive system constituting the working machine of the present invention.

[0066] As shown in Figure 4, controller 27 has adder 130, function generator 131, function generator 133, function generator 134, function generator 135, multiplier 136, multiplier 138, function generator 139, multiplier 140, multiplier 142, adder 144, and output conversion unit 146.

[0067] In Figure 4, detection signal 123 is a signal detected by pressure sensor 23 for the operation pilot pressure Pbd of the boom lowering direction of the operating rod 6a of the first operating device 6 (rod operation signal), detection signal 124 is a signal detected by pressure sensor 24 for the operation pilot pressure Pad of the arm releasing direction of the operating rod 1a of the second operating device 10 (rod operation signal), detection signal 125 is a signal detected by pressure sensor 25 for the pressure of the cylinder bottom side oil chamber of the boom cylinder 4 (pressure of the cylinder bottom side pipeline 15), and detection signal 126 is a signal detected by pressure sensor 26 for the discharge pressure of hydraulic cylinder I (hydraulic oil supply pipeline IIa). The signal detected by the pressure (chestnut pressure signal).

[0068] Input cylinder bottom pressure signal 125 and chestnut pressure signal 126 to adder 130 to calculate the deviation between cylinder bottom pressure signal 125 and chestnut pressure signal 126 (the differential pressure between the pressure in the bottom side oil chamber of boom cylinder 4 and the discharge pressure of hydraulic chestnut I), and input the differential pressure signal to function generator 131 and function generator 132.

[0069] Function generator 131 calculates the opening area of the regeneration side passage of regeneration control valve 17 corresponding to the differential pressure signal obtained by adder 130, and sets the characteristics based on the opening area characteristics of regeneration control valve 17 shown in Figure 3. Specifically, in the case of a small differential pressure, reducing the stroke of regeneration control valve 17 reduces the opening area of the regeneration side passage and expands the opening area of the fuel tank side passage. On the other hand, in the case of a large differential pressure, the control is carried out by expanding the opening area of the regeneration passage and maximizing the opening area of the regeneration passage when the differential pressure reaches a fixed value, and closing the opening of the fuel tank side passage.

[0070] Function generator 133 calculates the reduced flow rate of hydraulic cylinder I corresponding to the differential pressure signal obtained by adder 130 (hereinafter referred to as cylinder reduced flow rate). According to the characteristics of function generator 131, the larger the differential pressure, the larger the opening area of the regeneration side passage, and the higher the regeneration flow rate. Therefore, the larger the differential pressure, the more the flow rate of the chestnut is reduced.

[0071] The function generator 134 calculates the coefficients used by the multiplier based on the lever operation signal 123 of the I-th operating device 6. When the lever operation signal 123 is O, it outputs a minimum value of 0. As the lever operation signal 123 increases, the output increases and outputs I as the maximum value.

[0072] The multiplier 136 inputs the opening area calculated by the function generator 131 and the value calculated by the function generator 134, and outputs the product as the opening area. Here, in the case where the rod operation signal 123 of the I-th operating device 6 is small, it is necessary to slow down the piston rod speed of the boom cylinder 4, so it is required to also reduce the regeneration flow rate. Therefore, function generator 134 outputs smaller values from the range above O and below I, and makes the opening area calculated by function generator 131 a smaller value and outputs it.

On the other hand, in the case where the rod operation signal 123 of the I-th operating device 6 is large, it is necessary to accelerate the piston rod speed of the boom cylinder 4, thus also increasing the regeneration flow rate. Therefore, function generator 134 outputs larger values from the range above O and below I, reducing the decrease in opening area calculated by function generator 131 and outputting larger values of opening area.

[0074] The multiplier 138 inputs the reduced flow rate calculated by the function generator 133 and the value calculated by the function generator 134, and outputs the product as the reduced flow rate. Here, in the case where the lever operation signal 123 of the I-th operating device 6 is small, the regeneration flow rate is also small, so it is required to set the chestnut reduction flow rate to be small. Therefore, function generator 134 outputs smaller values from the range above O and below I, so that the reduced flow rate calculated by function generator 133 becomes a smaller value and is output.

On the other hand, when the lever operation signal 123 of the I-th operating device 6 is large, the regeneration flow rate increases, and it is necessary to also set the chestnut reduction flow rate to be large. Therefore, function generator 134 outputs larger values from the range above O and below I, reducing the decrease in flow rate calculated by function generator 133 and outputting larger values of flow rate reduction.

[0076] The function generator 135 calculates the coefficients used in the multiplier based on the lever operation signal 124 of the second operating device 10. When the lever operation signal 124 is O, it outputs a minimum value of 0. As the lever operation signal 124 increases, the output increases and outputs I as the maximum value.

[0077] The multiplier 140 inputs the aperture area calculated by the multiplier 136 and the value calculated by the function generator 135, and outputs the product as the aperture area. Here, in the case where the rod operation signal 124 of the second operating device 10 is small, it is necessary to slow down the piston rod speed of the stick cylinder 4, so it is required to also reduce the regeneration flow rate. Therefore, the function generator 135 outputs smaller values from the range above O and below I, so that the aperture area corrected by the multiplier 136 becomes a smaller value and outputs it.

On the other hand, in the case where the rod operation signal 124 of the second operating device 10 is large, it is necessary to accelerate the piston rod speed of the stick cylinder 4, thus also increasing the regeneration flow rate. Therefore, function generator 135 outputs larger values from the range above O and below I, reducing the decrease in aperture area corrected by multiplier 136 and outputting larger aperture area values.

[0079] The multiplier 142 inputs the reduced flow rate calculated by the multiplier 138 and the value calculated by the function generator 135, and outputs the product as the reduced flow rate. Here, in the case where the lever operation signal 124 of the second operating device 10 is small, the regeneration flow rate is also small, so it is required to set the chestnut reduction flow rate to be small. Therefore, the function generator 135 outputs smaller values from the range above O and below I, so that the reduced flow rate corrected by the multiplier 138 becomes a smaller value and outputs it.

On the other hand, when the lever operation signal 124 of the second operating device 10 is large, the regeneration flow rate increases, and it is necessary to also set the chestnut reduction flow rate to be large. Therefore, function generator 135 outputs larger values from the range above O and below I, reducing the decrease in flow rate corrected by multiplier 138, and outputting larger values of flow rate reduction.

[0081] In addition, it is expected to adjust the setting tables of function generators 131, 133, 134, and 135 in a way that the piston rod speed of boom cylinder 4 will not significantly change in the case where the discharged oil from the cylinder bottom side oil chamber of automatic arm cylinder 4 is regenerated for the driving of arm cylinder 8 in the future or not regenerated. In addition, due to the fact that the discharge oil from the bottom side oil chamber of the automatic arm cylinder 4 will be regenerated in the horizontal traction action of the arm cylinder 8 in the future, the pressure of the bottom side oil chamber of the boom cylinder 4 and the pressure of the piston rod side oil chamber of the arm cylinder 8 at this time will become values with a certain degree of certainty. Therefore, as long as the pressure of each part during the horizontal traction action is collected to analyze the pressure waveform and adjust the setting table of the above function generator, the opening area of the regeneration control valve 17 can be set to the optimal value.

[0082] The function generator 139 calculates the required flow rate based on the lever operation signal 124 of the second operating device 10. Set the characteristic of outputting the minimum flow rate from hydraulic cylinder I when the lever operation signal 124 is O. The purpose is to improve the responsiveness when operating the operating rod 1a of the second operating device 10 and prevent hydraulic cylinder I from burning. In addition, with the increase of the lever operation signal 124, the discharge flow rate of the hydraulic cylinder I increases, which increases the flow rate of hydraulic oil flowing into the arm cylinder 8. Thus, the piston rod speed of the stick cylinder 8 corresponding to the operation amount is achieved.

[0083] Input the chestnut reduced flow calculated by multiplier 142 and the chestnut required flow calculated by function generator 139 to adder 144, and subtract the chestnut reduced flow from the chestnut required flow to calculate the target chestnut flow.

[0084] Input the output from multiplier 140 and the output from adder 144 to output conversion unit 146, and output solenoid valve command 222 to solenoid proportional valve 22 and tilt command 201 to regulator Ia of hydraulic cylinder I, respectively.

[0085] As a result, the electromagnetic proportional valve 22 converts the primary pressure of the hydraulic oil supplied from the pilot shaft 3 into the desired pressure (secondary pressure) and outputs it to the operating part 17a of the regeneration control valve 17 to control the stroke of the regeneration control valve 17, thereby controlling the opening degree (opening area). In addition, the discharge flow rate is controlled by adjusting the tilt angle (capacity) of hydraulic cylinder I through regulator Ia. As a result, the hydraulic cylinder I is controlled to reduce its capacity in accordance with the regeneration flow rate supplied to the hydraulic oil supply line Ila on the bottom side of the slave arm cylinder 4.

[0086] Next, we will explain the operation of controller 27.

[0087] The signal of the operation pilot pressure Pbd detected by the pressure sensor 23 by operating the operating rod 6a of the I-th operating device 6 in the downward direction BD of the boom is input to the controller 27 as the rod operation signal 123. The signal of the operation pilot pressure Pad detected by the pressure sensor 24 by operating the operating rod 1a of the second operating device 10 in the direction AD of the arm release is input to the controller 27 as the rod operation signal 124. In addition, the signals of the pressure in the bottom side oil chamber of the boom cylinder 4 and the discharge pressure of the hydraulic cylinder I detected by the pressure sensors 25 and 26 are input to the controller 27 as the cylinder bottom pressure signal 125 and the cylinder pressure signal 126.

[0088] Input the cylinder bottom pressure signal 125 and the chestnut pressure signal 126 into the adder 130 to calculate the differential pressure signal. Input the differential pressure signal into function generator 131 and function generator 133, and calculate the opening area and flow rate of the regeneration side passage of regeneration control valve 17, respectively.

[0089] Input the lever operation signal 123 into the function generator 134, which calculates the correction signal corresponding to the lever operation amount and outputs it to the multiplier 136 and the multiplier 138. The multiplier 136 corrects the opening area of the regeneration side path output from the function generator 131, and the multiplier 138 corrects the reduced flow rate output from the function generator 133.

When the lever operation signal 124 is also input into the function generator 135, the function generator 135 calculates a correction signal corresponding to the lever operation amount and outputs it to the multiplier 140 and the multiplier 142. The multiplier 140 further corrects the opening area of the corrected regeneration side path output from the multiplier 136 and outputs it to the output conversion unit 146. The multiplier 142 further corrects the corrected chestnut reduction flow output from the multiplier 138 and outputs it to the adder 144.

[0091] The output conversion unit 146 converts the corrected opening area of the regeneration side passage into an electromagnetic valve command 222 and outputs it to the electromagnetic proportional valve 22. This controls the stroke of regeneration control valve 17. As a result, the regeneration control valve 17 is set to an opening area corresponding to the differential pressure between the pressure in the cylinder bottom side oil chamber of the boom cylinder 4 and the discharge pressure of the hydraulic cylinder I, and the discharge oil from the cylinder bottom side oil chamber of the boom cylinder 4 will be regenerated to the boom cylinder 8 in the future.

[0092] Input the lever operation signal 124 into the function generator 139, which calculates the required flow rate corresponding to the lever operation amount and outputs it to the adder 144.

[0093] The calculated chestnut demand flow rate and chestnut reduction flow rate are input to the adder 144, and the target chestnut flow rate is calculated by subtracting the chestnut reduction flow rate, which is the regeneration flow rate, from the chestnut demand flow rate, and output to the output conversion unit 146.

[0094] The output conversion unit 146 converts the target chestnut flow rate into a tilt command 201 for hydraulic chestnut I and outputs it to the regulator Ia. Thus, by controlling the arm cylinder 8 to a desired speed corresponding to the operation signal (operation pilot pressure Pad) of the second operating device 10, and reducing the discharge flow rate of the hydraulic cylinder I in accordance with the regeneration flow rate, it is possible to reduce the fuel consumption of the engine driving the hydraulic cylinder I and achieve energy conservation.

[0095] Through the above actions, the regeneration control valve 17 gradually increases the opening area of the regeneration side passage based on the pressure difference between the cylinder bottom oil chamber of the boom cylinder 4 and the discharge pressure of the hydraulic cylinder I, thereby suppressing switching shock and achieving good operability. In addition, when the differential pressure, the operating amount of the first operating device 6, and the operating amount of the second operating device 10 are all small, the opening area of the regeneration side passage of the regeneration control valve 17 is set small, and the opening area of the tank side passage is set large. Therefore, even if the regeneration flow rate is small, the tank side flow rate will increase. Thus, it is possible to ensure the piston rod speed of the boom cylinder that the operator expects.

On the other hand, when the differential pressure, the operating amount of the first operating device 6, and the operating amount of the second operating device 10 are large, the opening area of the regeneration side passage of the regeneration control valve 17 is set to be large, and the opening area of the oil tank side passage is set to be small. Therefore, it is possible to suppress the piston rod speed of the boom cylinder from being too fast and ensure the desired piston rod speed of the boom cylinder by the operator. In addition, by reducing the discharge flow of hydraulic cylinder I based on the regeneration flow rate, the piston rod speed of bucket cylinder 8 can also be ensured to meet the operator's desired speed.

[0097] Therefore, regardless of the regeneration flow rate of the hydraulic oil, the same actuator speed (piston rod speed of boom cylinder 4) can be ensured when regenerating the hydraulic oil discharged from the hydraulic actuator to drive other hydraulic actuators and when not regenerating. The result is that the same boom descent speed can be achieved in any situation.

[0098] According to the first embodiment of the hydraulic drive system for the working machine of the present invention described above, it is possible to ensure the same actuator speed when regenerating the hydraulic oil discharged from the hydraulic actuator 4 for driving other hydraulic actuators 8 and when not regenerating. The electromagnetic proportional valve 22 (electrical drive device) for the regeneration circuit can be composed of one electromagnetic proportional valve. As a result, good operability can be achieved, and cost reduction and installation improvement can be sought.

[0099] Example 2

Below [0100], the second embodiment of the hydraulic drive system of the working machine of the present invention will be illustrated using the accompanying drawings. Figure 5 is a schematic diagram showing the control system of the hydraulic drive system of the working machine according to the second embodiment of the present invention, Figure 6 is a characteristic diagram showing the opening area characteristics of the oil tank side control valve constituting the hydraulic drive system of the working machine according to the second embodiment of the present invention, and Figure 7 is a characteristic diagram showing the opening area characteristics of the regeneration side control valve constituting the hydraulic drive system of the working machine according to the second embodiment of the present invention. In Figures 5 to 7, the parts with the same reference numerals as those shown in Figures 1 to 4 are the same, so their detailed explanations are omitted.

In the second embodiment of the hydraulic drive system for the working machine of the present invention, the oil tank side control valve 41 as a discharge flow rate adjusting device and the regeneration side control valve 40 as a regeneration flow rate adjusting device are respectively provided on the cylinder bottom side pipeline 15 instead of the regeneration control valve 17 shown in Figure 1, which is different from the first embodiment. The stroke of the fuel tank side control valve 41 and the stroke of the regeneration side control valve 40 are controlled by an electromagnetic proportional valve 22.

[0102] As an electrical driving device, the electromagnetic proportional valve 22 operates according to control instructions from the controller 27. The electromagnetic proportional valve 22 converts the primary pressure of the hydraulic oil supplied from the pilot shaft 3 into the desired pressure (secondary pressure) and outputs it to the operating portion 41a of the tank side control valve 41 and the operating portion 40a of the regeneration side control valve 40 to control the stroke of the tank side control valve 41 and the stroke of the regeneration side control valve 40, thereby controlling the opening degree (opening area) of each valve.

[0103] Figure 6 shows the opening area characteristics of the fuel tank side control valve 41, and Figure 7 shows the opening area characteristics of the regeneration side control valve 40. The horizontal axis of these figures shows the slide stroke of each valve, and the vertical axis shows the opening area. These characteristics are formed equally with the separated parts on the tank side and regeneration side in the regeneration control valve 17 in the first embodiment shown in Figure 3.

In this embodiment, since the opening area of the regeneration side passage and the opening area of the fuel tank side passage can be independently controlled, it is possible to further improve fuel efficiency.

According to the second embodiment of the hydraulic drive system for the working machine of the present invention, the same effect as the first embodiment can be obtained.

In addition, according to the second embodiment of the hydraulic drive system for the working machine of the present invention described above, the degree of freedom in design for the opening area of the regeneration side passage and the opening area of the oil tank side passage is increased, allowing for more detailed matching settings. The result is that it can further improve the fuel consumption reduction effect.

[0107] Implementation Example 3

[0108] Below, the third embodiment of the hydraulic drive system of the working machine of the present invention will be illustrated using the accompanying drawings. Figure 8 is a schematic diagram showing the control system of the hydraulic drive system of the working machine according to the third embodiment of the present invention. In Figure 8, the parts with the same reference numerals as those shown in Figures 1 to 7 are the same, so their detailed explanations are omitted.

[0109] In the third embodiment of the hydraulic drive system for the working machine of the present invention, the aspect of providing a regeneration control valve 42 composed of an electromagnetic proportional valve having a valve portion 42b and an electromagnetic coil portion 42a instead of the regeneration control valve 17 shown in Figure 1 is different from the first embodiment, wherein the valve portion 42b has the same structure as the valve portion of the regeneration control valve 17, such as a slide valve, and the electromagnetic coil portion 42a is incorporated into the valve portion 42b and directly controlled by the controller 27. In this embodiment, the electrical driving device is equivalent to the electromagnetic coil portion 42a. In addition, the regeneration flow adjustment device and the discharge flow adjustment device are composed of a regeneration control valve 42.

In this embodiment, since there is no need to configure the electromagnetic proportional valve 22, it is possible to further improve the installation performance

According to the third embodiment of the hydraulic drive system for the working machine of the present invention, the same effect as the first embodiment can be obtained.

[0112] Example 4

[0113] The fourth embodiment of the hydraulic drive system of the working machine of the present invention will be illustrated using the accompanying drawings. Figure 9 is a schematic diagram showing the control system of the hydraulic drive system of the working machine according to the fourth embodiment of the present invention. In Figure 9, the parts with the same reference numerals as those shown in Figures 1 to 8 are the same, so their detailed explanations are omitted.

[0114] In the fourth embodiment of the hydraulic drive system for the working machine of the present invention, there is a difference from the first embodiment in that a control valve 43 is provided on the cylinder bottom side pipeline 15 between the regeneration control valve 17 shown in Figure 1 and the cylinder bottom side oil chamber of the boom cylinder 4, which can discharge the discharged oil from the cylinder bottom side oil chamber of the boom cylinder 4 to the oil tank. In this embodiment, the regeneration flow adjustment device is composed of a regeneration control valve 17, and the discharge flow adjustment device is composed of a regeneration control valve 17 and a control valve 43.

[0115] The control valve 43 has an operating part 43a, which opens the valve by transmitting the operation pilot pressure Pbd of the boom lowering direction BD of the I-th operating device 6 to the operating part 43a, thereby discharging the discharged oil from the bottom side oil chamber of the automatic arm cylinder 4 to the oil tank. The opening area of control valve 43 is set to be sufficiently small compared to the opening area connected to the fuel tank pipeline 7b of control valve 5.

By configuring as in this embodiment, for example, in the single action of lowering the boom with control valve 9 closed, in the event that regeneration control valve 17 accidentally switches due to a malfunction of controller 27 or the like, causing the discharge location of the cylinder bottom oil chamber to disappear, it can still be discharged from control valve 43, thus preventing the boom from suddenly stopping.

In addition, the control valve used to supply hydraulic oil during the lifting action of the boom cylinder 4 is usually composed of two or more control valves. Therefore, it can also be configured such that one of the two or more control valves has the same function as the control valve 43 mentioned above. In this case, there is no need to add control valve 43 to the circuit, and the control valve with the previous configuration can be used.

According to the fourth embodiment of the hydraulic drive system for the working machine of the present invention, the same effect as the first embodiment can be obtained.

[0119] In addition, according to the fourth embodiment of the hydraulic drive system for the working machine of the present invention, even in the event of a controller failure or the like, the hydraulic drive system of the working machine can operate stably.

[0120] In addition, the present invention is not limited to the above embodiments, and includes various modifications within the scope of its essence. For example, in the above embodiments, the case where the present invention is applied to a hydraulic excavator has been described, but the present invention can also be applied to other work machines such as hydraulic cranes and wheel loaders as long as they have a hydraulic cylinder that discharges hydraulic oil from the bottom side of the cylinder and sucks hydraulic oil from the piston rod side by the self weight of the I-driven body when operating the I-operating device in the self weight direction of the I-driven body.