Hydraulic Drive Unit

Abstract

To provide a liquid pressure drive device capable of improving a degree of freedom in control relating to opening of a passage connected to a travel motor.SOLUTION: A liquid pressure drive device for supplying working fluid to each of a travel motor and a cargo handling actuator includes: a liquid pressure pump discharging the working liquid; a flow dividing valve for dividing a pump passage connected to the liquid pressure pump into a first passage and a second passage, and changing openings of the first passage and the second passage according to an input opening signal; a travel system liquid pressure circuit connected to the first passage and controlling flow of the working liquid to the travel motor; a cargo handling system liquid pressure circuit connected to the second passage and controlling flow of the working liquid to the cargo handling actuator; a travel-side pressure sensor detecting a travel-side supply pressure as a supply pressure to the travel motor; and a control device controlling the opening of the first passage and the opening of the second passage according to the travel-side supply pressure detected by the travel-side pressure sensor by outputting the opening signal to the flow dividing valve.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydraulic drive system that supplies hydraulic fluid to a travel motor and a load-handling actuator. [Background technology]

[0002] One-pump systems in which a single pump serves as the hydraulic pressure source for the travel motor and the load-handling actuator of a construction machine are in practical use. A hydraulic circuit such as that disclosed in Patent Document 1 is known as a hydraulic drive device for a one-pump system. In the hydraulic circuit of Patent Document 1, the pump is connected to the travel motor and the load-handling actuator via a first pump line and a second pump line, respectively. A priority valve is also provided on the second pump line. The supply pressure of the travel motor acts on the priority valve. Therefore, when the supply pressure of the travel motor increases, the priority valve preferentially allows pressurized oil to flow to the travel motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-026828 Summary of the Invention [Problem to be solved by the invention]

[0004] In the hydraulic circuit of Patent Document 1, the priority valve throttles the aperture of the second pump line depending on the applied supply pressure. Therefore, the priority valve determines a one-to-one relationship between the supply pressure and the aperture of the second pump line. Therefore, the priority valve has a low degree of freedom in controlling the aperture of the second pump line.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a hydraulic drive system that can improve the degree of freedom in controlling the opening degree of a passage connected to a cargo handling actuator. [Means for solving the problem]

[0006] The hydraulic drive device of the present invention supplies hydraulic fluid to a travel motor and a cargo handling actuator, respectively, and includes a hydraulic pump that discharges hydraulic fluid, a diverter valve that branches a pump passage connected to the hydraulic pump into a first passage and a second passage and changes the aperture of each of the first passage and the second passage in response to an input aperture signal, a travel system hydraulic circuit connected to the first passage and controlling the flow of hydraulic fluid to the travel motor, a cargo system hydraulic circuit connected to the second passage and controlling the flow of hydraulic fluid to the cargo handling actuator, a travel side pressure sensor that detects a travel side supply pressure that is the supply pressure to the travel motor, and a control device that outputs an aperture signal to the diverter valve to control the aperture of the first passage and the aperture of the second passage in response to the travel side supply pressure detected by the travel side pressure sensor.

[0007] According to the present invention, the control device controls the aperture of the first passage and the aperture of the second passage in response to the travel-side supply pressure by outputting an aperture signal to the dividing valve. Therefore, by changing the control logic of the control device, the aperture of the first passage and the aperture of the second passage that are opened in response to the travel-side supply pressure can be easily adjusted. This improves the degree of freedom in control of the aperture of the second passage connected to the cargo-handling actuator. [Effects of the Invention]

[0008] According to the present invention, it is possible to improve the degree of freedom in controlling the opening degree of the passage leading to the cargo handling actuator. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a circuit diagram showing the configuration of a hydraulic drive device according to a first embodiment of the present invention. [Figure 2] FIG. 4 is a circuit diagram showing the configuration of a hydraulic drive device according to a second embodiment of the present invention. [Figure 3] FIG. 10 is a circuit diagram showing a traveling system hydraulic circuit of a hydraulic drive system according to a third embodiment of the present invention. [Figure 4] FIG. 10 is a circuit diagram showing a travel system hydraulic circuit of a hydraulic drive system according to another embodiment of the present invention. [Figure 5] FIG. 10 is a circuit diagram showing a travel system hydraulic circuit of a hydraulic drive system according to still another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, hydraulic drive units 1, 1A, and 1B according to first to third embodiments of the present invention will be described with reference to the drawings mentioned above. Note that the concepts of directions used in the following description are used for convenience of explanation and do not limit the orientation of the configuration of the invention to those directions. Furthermore, the hydraulic drive units 1, 1A, and 1B described below are merely one embodiment of the present invention. Therefore, the present invention is not limited to the embodiments, and additions, deletions, and modifications are possible within the scope of the invention.

[0011] [First embodiment] The hydraulic drive system 1 shown in Fig. 1 is provided on a work vehicle (not shown) that includes travel motors 2 and 3 and cargo handling actuators 4 to 6. Work vehicles include, for example, construction vehicles such as hydraulic excavators and hydraulic cranes, and industrial vehicles such as lifts. In this embodiment, the hydraulic drive system 1 is provided on a hydraulic excavator, which is an example of a work vehicle. In addition to the hydraulic drive system 1, the hydraulic excavator also includes a vehicle body and a work machine.

[0012] The vehicle body is, for example, a tracked device, and includes, for example, a pair of left and right crawlers (not shown), and a pair of left and right travel motors 2, 3. The vehicle body travels by operating the pair of left and right crawlers. The vehicle body may be a wheeled device, or any other device that can travel. The travel motors 2, 3 are hydraulic motors that drive the left and right crawlers, respectively. More specifically, the travel motors 2, 3 each have two supply / discharge ports 2a, 2b, 3a, 3b. The travel motors 2, 3 rotate in the forward direction when hydraulic fluid is supplied to one of the supply / discharge ports 2a, 3a, and rotate in the reverse direction when hydraulic fluid is supplied to the other supply / discharge port 2b, 3b.

[0013] The work machine includes a boom, an arm, a bucket (none of which are shown), and a plurality of load-handling actuators 4-6. The work machine is rotatably mounted on the vehicle body. In this embodiment, the load-handling actuators 4-6 are hydraulic cylinders 4-6. The hydraulic cylinders 4-6 are respectively mounted on the boom, arm, and bucket. The work machine moves the boom, arm, and bucket by extending and retracting the three hydraulic cylinders 4-6. This enables the work machine to perform a variety of tasks.

[0014] <Hydraulic drive unit> The hydraulic drive system 1 includes a hydraulic pump 11, a flow dividing valve 12, a traveling system hydraulic circuit 13, a cargo handling system hydraulic circuit 14, traveling side pressure sensors 15 and 16, and a control device 17. More specifically, the hydraulic drive system 1 further includes cargo handling side pressure sensors 18-20, a traveling system operating device 21, and a cargo handling system operating device 22. The hydraulic drive system 1 is a so-called one-pump system, in which one hydraulic pump 11 supplies hydraulic fluid to the traveling motors 2 and 3 and three hydraulic cylinders 4-6. The hydraulic drive system 1 supplies hydraulic fluid to the first traveling motor 2 and the second traveling motor 3, respectively, thereby operating the crawlers corresponding to the traveling motors 2 and 3. This allows the hydraulic drive system 1 to travel the hydraulic excavator. The hydraulic drive system 1 supplies hydraulic fluid to the hydraulic cylinders 4-6, thereby operating the corresponding boom, arm, and bucket. This allows the hydraulic drive system 1 to cause the hydraulic excavator to perform a variety of tasks.

[0015] <Hydraulic pump> The hydraulic pump 11 discharges hydraulic fluid. More specifically, the hydraulic pump 11 is connected to a drive source (e.g., an engine and an electric motor) not shown. The hydraulic pump 11 is connected to a pump passage 25. The hydraulic pump 11 is driven to rotate by the drive source, thereby discharging hydraulic fluid into the pump passage 25.

[0016] <Flow dividing valve> The flow dividing valve 12 is an electrically controlled valve. The flow dividing valve 12 is, for example, an electrically controlled spool valve and includes a flow dividing spool 12a. The flow dividing valve 12 branches the pump passage 25 into a first passage 26 and a second passage 27. That is, the flow dividing valve 12 divides the hydraulic fluid discharged from the hydraulic pump 11. The flow dividing valve 12 changes the aperture of each of the first passage 26 and the second passage 27 in response to an input aperture signal. As a result, the flow dividing valve 12 changes the flow rate of the hydraulic fluid flowing through each of the first passage 26 and the second passage 27 in response to the input aperture signal. In this embodiment, the hydraulic drive unit 1 is provided with one flow dividing valve 12 for each hydraulic pump 11. In the hydraulic drive unit 1, the flow rate of the hydraulic fluid flowing through each of the first passage 26 and the second passage 27 can be changed by one flow dividing valve 12.

[0017] The flow dividing spool 12a can move to a first position A1 or a second position A2 in response to an input opening signal. The flow dividing valve 12 includes an electromagnetic proportional valve 12b and a spring 12c. The electromagnetic proportional valve 12b outputs a pilot pressure to the flow dividing spool 12a in response to the opening signal. The spring 12c acts on the flow dividing spool 12a so as to resist the pilot pressure of the electromagnetic proportional valve 12b. Therefore, the flow dividing spool 12a moves to the first position A1 or the second position A2 in response to the pilot pressure output from the electromagnetic proportional valve 12b.

[0018] The diversion spool 12a reduces the opening of the first passage 26 at the first position A1 and reduces the opening of the second passage 27 at the second position A2. More specifically, the diversion spool 12a reduces the opening of the first passage 26 and opens the second passage 27 at the first position A1. On the other hand, the diversion spool 12a reduces the opening of the second passage 27 and opens the first passage 26 at the second position A2. The diversion spool 12a is held in the first position A1 by the spring 12c when no pilot pressure is output. When pilot pressure is output, the diversion spool 12a moves to the second position A2.

[0019] The diversion spool 12a moves by a stroke amount corresponding to the opening signal. The diversion spool 12a changes the opening of each passage 26, 27 depending on the stroke amount at the first position A1 and the second position A2. More specifically, the diversion spool 12a opens the opening of the first passage 26 as it moves from the first position A1 toward the second position A2, and opens the opening of the second passage 27 as it moves from the second position A2 toward the first position A1.

[0020] <Traction system hydraulic circuit> The travel system hydraulic circuit 13 includes a first travel directional control valve 31 and a second travel directional control valve 32. The travel system hydraulic circuit 13 is connected to the first passage 26 and the first and second travel motors 2 and 3. The travel system hydraulic circuit 13 supplies hydraulic fluid to each of the first and second travel motors 2 and 3. The travel system hydraulic circuit 13 controls the flow of hydraulic fluid to each of the first and second travel motors 2 and 3. More specifically, the travel system hydraulic circuit 13 supplies hydraulic fluid to the first and second travel motors 2 and 3 in a flow (flow direction and flow rate in this embodiment) that corresponds to the input first and second travel commands.

[0021] The first travel direction control valve 31 has a first travel spool 31a. The first travel direction control valve 31 controls the flow of hydraulic fluid to the first travel motor 2. More specifically, the first travel direction control valve 31 is connected to the first passage 26, the tank 28, and the two supply and discharge ports 2a and 2b of the first travel motor 2. The first travel spool 31a moves in response to an input first travel command. This switches the connection destinations of the supply and discharge ports 2a and 2b to the first passage 26 and the tank 28, respectively. The first travel spool 31a changes its opening depending on its position. Therefore, hydraulic fluid is supplied from the first travel direction control valve 31 to the first travel motor 2 in a direction and at a flow rate corresponding to the first travel command. As a result, the first travel direction control valve 31 rotates the first travel motor 2 forward and reverse in response to the first travel command, and rotates the first travel motor 2 at a speed corresponding to the first travel command. In this embodiment, the first traveling directional control valve 31 is an electrically controlled directional control valve.

[0022] The second travel direction control valve 32 has a second travel spool 32a. The second travel direction control valve 32 controls the flow of hydraulic fluid to the second travel motor 3. More specifically, the second travel direction control valve 32 is connected to the first passage 26 in parallel with the first travel direction control valve 31. The second travel direction control valve 32 is also connected to the tank 28 and two supply / discharge ports 3a and 3b of the second travel motor 3. The second travel spool 32a moves in response to an input second travel command. This switches the connection destinations of the supply / discharge ports 3a and 3b to the first passage 26 and the tank 28, respectively. The second travel spool 32a changes its opening depending on its position. Therefore, hydraulic fluid is supplied from the second travel direction control valve 32 to the second travel motor 3 in a direction and at a flow rate that corresponds to the second travel command. As a result, the second traveling direction control valve 32 rotates the second traveling motor 3 in the forward or reverse direction in response to the second traveling command, and rotates the second traveling motor 3 at a speed in accordance with the second traveling command. In this embodiment, the second traveling direction control valve 32 is an electrically controlled directional control valve.

[0023] <Cargo handling hydraulic circuit> The cargo handling hydraulic circuit 14 includes a plurality of cargo handling directional control valves 41-43. In this embodiment, the cargo handling hydraulic circuit 14 includes three cargo handling directional control valves 41-43. The three cargo handling directional control valves 41-43 are a boom directional control valve 41, an arm directional control valve 42, and a bucket directional control valve 43. The cargo handling hydraulic circuit 14 is connected to the second passage 27 and the three hydraulic cylinders 4-6. The cargo handling hydraulic circuit 14 supplies hydraulic fluid to each of the three hydraulic cylinders 4-6. The cargo handling hydraulic circuit 14 controls the flow of hydraulic fluid to each of the hydraulic cylinders 4-6. More specifically, the cargo handling hydraulic circuit 14 supplies hydraulic fluid to the three hydraulic cylinders 4-6 in a flow (flow direction and flow rate in this embodiment) that corresponds to the input cargo handling command.

[0024] The three load-handling directional control valves 41-43 have load-handling spools 41a-43a, respectively. The three load-handling directional control valves 41-43 control the flow of hydraulic fluid to the corresponding hydraulic cylinders 4-6. That is, the boom-handling directional control valve 41 controls the flow of hydraulic fluid to the boom cylinder 4. The arm-handling directional control valve 42 controls the flow of hydraulic fluid to the arm cylinder 5. The bucket-handling directional control valve 43 controls the flow of hydraulic fluid to the bucket cylinder 6. The three load-handling directional control valves 41-43 are connected to the second passage 27 in parallel with one another. Furthermore, the three load-handling directional control valves 41-43 are connected to the tank 28 and the rod-side ports 4a, 5a, 6a and head-side ports 4b, 5b, 6b of each hydraulic cylinder 4-6, respectively. The load-handling spools 41a-43a move in response to a boom command, an arm command, and a bucket command, respectively. As a result, the connections of the rod-side ports 4a-6a and the head-side ports 4b-6b are switched to the second passage 27 and the tank 28, respectively. The cargo-handling spools 41a-43a change their opening depending on their positions. Therefore, hydraulic fluid is supplied from each of the cargo-handling directional control valves 41-43 to each of the hydraulic cylinders 4-6 in a direction and at a flow rate corresponding to each command. As a result, the cargo-handling directional control valves 41-43 can extend or retract the corresponding hydraulic cylinders 4-6 at a speed corresponding to each command. In this embodiment, the cargo-handling directional control valves 41-43 are also electrically controlled directional control valves.

[0025] <First driving side pressure sensor> The first traveling side pressure sensor 15 detects the first traveling side supply pressure, which is the pressure supplied to the first traveling motor 2. More specifically, the first traveling side pressure sensor 15 detects the hydraulic pressure of the hydraulic fluid supplied from the first traveling directional control valve 31 to the first traveling motor 2. In this embodiment, the first traveling side pressure sensors 15 are provided in the supply and discharge ports 2a, 2b of the first traveling motor 2. The first traveling side pressure sensor 15 outputs the hydraulic pressure detected at the supply and discharge ports 2a, 2b of the first traveling motor 2.

[0026] <Second driving side pressure sensor> Second traveling-side pressure sensor 16 is a sensor separate from first traveling-side pressure sensor 15, and detects second traveling-side supply pressure, which is the pressure supplied to second traveling motor 3. More specifically, second traveling-side pressure sensor 16 detects the hydraulic pressure of the hydraulic fluid supplied from second traveling directional control valve 32 to second traveling motor 3. In this embodiment, second traveling-side pressure sensor 16 is connected to each of supply and discharge ports 3a, 3b of second traveling motor 3. Second traveling-side pressure sensor 16 outputs the hydraulic pressure detected at supply and discharge ports 3a, 3b of second traveling motor 3.

[0027] <Loading side pressure sensor> The cargo-side pressure sensors 18-20 detect the cargo-side supply pressure, which is the pressure supplied to the hydraulic cylinders 4-6. More specifically, each of the cargo-side pressure sensors 18-20 detects the supply pressure supplied to the boom cylinder 4, the arm cylinder 5, and the bucket cylinder 6. In this embodiment, the cargo-side pressure sensors 18-20 are connected to the rod-side ports 4a-6a and the head-side ports 4b-6b of the hydraulic cylinders 4-6, respectively. The cargo-side pressure sensors 18-20 output the hydraulic pressure detected at the rod-side ports 4a-6a and the head-side ports 4b-6b of the hydraulic cylinders 4-6.

[0028] <Traveling system operating device> The traveling system operation device 21 is a device that allows the driver to operate the traveling motors 2, 3. The traveling system operation device 21 includes, for example, a traveling operation lever 21a, which is an operating tool. The traveling operation lever 21a can be tilted. In this embodiment, the traveling operation lever 21a can be tilted, for example, in all directions. The traveling system operation device 21 outputs a traveling operation command according to the tilt direction and tilt amount. The operating tool provided in the traveling system operation device 21 may be an operation pedal, and its form is not limited.

[0029] <Cargo handling operation device> The cargo handling system operation device 22 is a device that allows the driver to operate an attachment (a bucket in this embodiment). More specifically, the operating tools of the cargo handling system operation device 22 include a cargo handling operation lever 22a. The cargo handling operation lever 22a can be tilted. In this embodiment, the cargo handling operation lever 22a can be tilted, for example, in the forward and backward directions. The cargo handling system operation device 22 outputs a cargo handling operation command according to the tilt direction and tilt amount. Note that the operating tool provided in the cargo handling system operation device 22 is not limited to the cargo handling operation lever 22a, and may be in other forms such as an operation panel.

[0030] <Control device> The control device 17 controls the operation of the traveling system hydraulic circuit 13. More specifically, the control device 17 acquires a traveling operation command output from the traveling system operating device 21. In response to this, the control device 17 controls the movement of the first traveling direction control valve 31 and the second traveling direction control valve 32 (i.e., the positions of the spools 31a, 32a) in accordance with the traveling operation command. In this embodiment, the control device 17 outputs a first traveling command and a second traveling command in accordance with the traveling operation command. In response to this, the first traveling motor 2 and the second traveling motor 3 rotate in a direction and at a rotational speed in accordance with the traveling operation command, and the hydraulic excavator moves in a direction and at a speed in accordance with the traveling operation command.

[0031] The control device 17 controls the operation of the cargo handling hydraulic circuit 14. More specifically, the control device 17 acquires cargo handling operation commands output from the cargo handling operation device 22. In response to the cargo handling operation commands, the control device 17 controls the movement of the cargo handling directional control valves 41-43 (i.e., the positions of the spools 41a-43a). In this embodiment, the control device 17 outputs a boom command, an arm command, and a bucket command in response to the cargo handling operation commands. In response to the cargo handling operation commands, the hydraulic cylinders 4-6 extend and retract at a speed in accordance with the cargo handling operation commands. This allows the bucket to move in a direction and at a speed in accordance with the cargo handling operation commands, allowing the hydraulic excavator to perform the desired work.

[0032] The control device 17 outputs an opening degree signal to the flow dividing valve 12. As a result, the control device 17 controls the opening degree of the first passage 26 and the opening degree of the second passage 27 in accordance with the travel-side supply pressure detected by the travel-side pressure sensors 15 and 16 and the loading-side supply pressure detected by the loading-side pressure sensors 18-20. More specifically, the control device 17 acquires the travel-side supply pressure and the loading-side supply pressure. In this embodiment, the control device 17 selects the first travel-side supply pressure and the second travel-side supply pressure from the hydraulic pressures detected by the travel-side pressure sensors 15 and 16. The control device 17 estimates, for example, which of the supply / discharge ports 2a, 2b, 3a, and 3b will be the supply side based on the travel operation command. The control device 17 acquires the hydraulic pressures of the supply-side ports as the first travel-side supply pressure and the second travel-side supply pressure. In a similar manner, the control device 17 selects the loading-side supply pressure for each of the hydraulic cylinders 4-6 from the hydraulic pressures detected by the loading-side pressure sensors 18-20. Furthermore, the control device 17 outputs an opening signal in accordance with the acquired first traveling-side supply pressure, second traveling-side supply pressure, and loading-side supply pressure for each of the hydraulic cylinders 4-6. This causes the flow-dividing spool 12a to move to a position in accordance with the first traveling-side supply pressure, second traveling-side supply pressure, and loading-side supply pressure for each of the hydraulic cylinders 4-6. Therefore, the opening of the first passage 26 and the opening of the second passage 27 are controlled in accordance with the first traveling-side supply pressure, second traveling-side supply pressure, and loading-side supply pressure.

[0033] For example, when the maximum value of the two travel-side supply pressures is equal to or greater than a predetermined travel-side threshold, the control device 17 reduces the opening degree of the second passage 27. When the maximum value of the two travel-side supply pressures is less than the travel-side threshold and the maximum value of the three loading-side supply pressures is equal to or greater than the loading-side threshold, the control device 17 reduces the opening degree of the first passage 26. When the maximum value of the three loading-side supply pressures is less than the loading-side threshold, the control device 17 reduces the opening degree of the second passage 27. The travel-side threshold and the loading-side threshold are set in advance in the control device 17. The travel-side threshold and the loading-side threshold are set to be adjustable, for example.

[0034] Furthermore, the control device 17 changes the position of the diverter spool 12a in response to the first traveling-side supply pressure, the second traveling-side supply pressure, and the three loading-side supply pressures based on a preset program or the like. This controls the opening degrees of the passages 26, 27 to correspond to the first traveling-side supply pressure, the second traveling-side supply pressure, and the three loading-side supply pressures. The control device 17 can change the opening degrees of the passages 26, 27 that are opened in response to the first traveling-side supply pressure, the second traveling-side supply pressure, and the loading-side supply pressures of the hydraulic cylinders 4-6. More specifically, the control device 17 adjusts the command values ​​of the commands output in response to the first traveling-side supply pressure, the second traveling-side supply pressure, and the loading-side supply pressures of the hydraulic cylinders 4-6. This allows, for example, the opening degrees of the passages 26, 27 that are opened in response to the first traveling-side supply pressure and the second traveling-side supply pressure to be adjusted in response to the loading-side supply pressures.

[0035] <Operation of the hydraulic drive unit> In the hydraulic drive system 1, when the travel operation lever 21a of the travel system operation device 21 is operated independently, a travel operation command is output from the travel system operation device 21. In response, the control device 17 actuates the travel direction control valves 31, 32 and controls the flow of hydraulic fluid to the travel motors 2, 3 to a flow (flow direction and flow rate in this embodiment) according to the travel operation command. This allows the control device 17 to cause the hydraulic excavator to perform a travel operation according to the operation of the travel operation lever 21a. Note that when the maximum values ​​of the first travel-side supply pressure and the second travel-side supply pressure become equal to or greater than the travel-side threshold value due to the supply of hydraulic fluid to the travel motors 2, 3, the diversion spool 12a of the flow diverter valve 12 moves to the second position A2. This opens the first passage 26 and reduces the aperture of the second passage 27.

[0036] Next, in the hydraulic drive system 1, when the cargo handling operation lever 22a of the cargo handling system operation device 22 is operated independently, a cargo handling operation command is output from the cargo handling system operation device 22. In response, the control device 17 operates the cargo handling directional control valves 41-43 to control the flow of hydraulic fluid to the hydraulic cylinders 4-6 to a flow (flow direction and flow rate in this embodiment) according to the cargo handling operation command. This allows the control device 17 to cause the bucket to operate in accordance with the operation of the cargo handling operation lever 22a. Note that when the maximum values ​​of the first traveling-side supply pressure and the second traveling-side supply pressure are less than the traveling-side threshold value and the maximum value of the three cargo handling-side supply pressures is equal to or greater than a predetermined cargo handling-side threshold value, the flow dividing spool 12a of the flow dividing valve 12 is held in the first position A1. This opens the second passage 27 and reduces the aperture of the first passage 26.

[0037] Furthermore, when the travel operation lever 21a and the load operation lever 22a are operated simultaneously, the hydraulic drive unit 1 operates as follows. That is, the control device 17 operates the flow diverter valve 12 based on the acquired travel-side supply pressure and load-side supply pressure. For example, if the maximum value of the two travel-side supply pressures is equal to or greater than the travel-side threshold value, the control device 17 moves the flow diverter spool 12a of the flow diverter valve 12 to the second position A2. This opens the first passage 26 and reduces the aperture of the second passage 27. This prevents a shortage of hydraulic fluid supplied to the travel motors 2 and 3. The aperture of the second passage 27 is controlled to an aperture corresponding to the travel-side supply pressure and the load-side supply pressure. This allows an appropriate amount of hydraulic fluid to flow through the load-side hydraulic circuit 14. On the other hand, when the maximum value of the two travel-side supply pressures is less than the travel-side threshold value and the maximum value of the loading-side supply pressure is equal to or greater than the loading-side threshold value, the control device 17 holds the flow dividing spool 12a of the flow dividing valve 12 in the first position A1. This opens the second passage 27 and reduces the opening of the first passage 26, thereby preventing a shortage of the supply of hydraulic fluid to the hydraulic cylinders 4 to 6.

[0038] In the hydraulic drive unit 1 of the first embodiment, the control device 17 outputs an opening degree signal to the diverter valve 12 to control the opening degrees of the first passage 26 and the second passage 27 in response to the travel-side supply pressure. Therefore, by changing the control logic of the control device 17, the opening degrees of the first passage 26 and the second passage 27 that are opened in response to the travel-side supply pressure can be easily adjusted. For example, the control device 17 can easily adjust the travel-side threshold value and the loading-side threshold value, or adjust the opening degree to be opened in response to the travel-side supply pressure. Therefore, the degree of freedom in control of the opening degree of the first passage 26 can be improved.

[0039] In the hydraulic drive unit 1 of the first embodiment, the control device 17 controls the opening degree of the first passage 26 and the opening degree of the second passage 27 in accordance with the travel-side supply pressure and the load-handling-side supply pressure. Therefore, the control device 17 can adjust the opening degree of the first passage 26 and the opening degree of the second passage 27, which are throttled in response to the travel-side supply pressure, in accordance with the load-handling-side supply pressure. This makes it possible to adjust the flow rate of hydraulic fluid flowing through the travel-system hydraulic circuit 13 in accordance with the status of the load-handling actuators 4 to 6.

[0040] In the hydraulic drive unit 1 of the first embodiment, the opening degree of the first passage 26 and the opening degree of the second passage 27 can be narrowed by moving the flow dividing spool 12a. Therefore, the opening degrees of the first passage 26 and the second passage 27 can be easily controlled.

[0041] In the hydraulic drive unit 1 of the first embodiment, the control device 17 controls the opening degree of the first passage 26 and the opening degree of the second passage 27 in accordance with the first traveling-side supply pressure and the second traveling-side supply pressure. Therefore, even when the traveling system hydraulic circuit 13 supplies hydraulic fluid to two traveling motors 2, 3, the degree of freedom in control of the opening degree of the first passage 26 connected to the traveling motors 2, 3 can be improved.

[0042] In the hydraulic drive system 1 of the first embodiment, the first traveling-side pressure sensor 15 detects the pressure of the hydraulic fluid supplied from the first traveling directional control valve 31 to the first traveling motor 2. The second traveling-side pressure sensor 16 detects the pressure of the hydraulic fluid supplied from the second traveling directional control valve 32 to the second traveling motor 3. Therefore, the supply pressure of the hydraulic fluid supplied to each traveling motor 2, 3 can be easily obtained.

[0043] In the hydraulic drive unit 1 of the first embodiment, the control device 17 controls the aperture of the first passage 26 and the aperture of the second passage 27 in accordance with the travel-side supply pressure and a plurality of cargo-side supply pressures. Therefore, the control device 17 controls the aperture of the first passage 26 and the aperture of the second passage 27 in accordance with the travel-side supply pressure and three cargo-side supply pressures. Therefore, the control device 17 can adjust the aperture of the first passage 26 and the aperture of the second passage 27, which are throttled back in response to the travel-side supply pressure, in accordance with the plurality of cargo-side supply pressures. This makes it possible to adjust the flow rate of hydraulic fluid flowing through the travel-system hydraulic circuit 13 in accordance with the status of each of the cargo-side actuators 4 to 6.

[0044] In the hydraulic drive system 1 of the first embodiment, each of the multiple load-handling side pressure sensors 18-20 detects the supply pressure of the hydraulic fluid supplied from the corresponding load-handling directional control valves 41-43 to the hydraulic cylinders 4-6. Therefore, the supply pressure of the hydraulic fluid supplied to each of the hydraulic cylinders 4-6 can be easily obtained.

[0045] In the hydraulic drive system 1 of the first embodiment, the control device 17 operates the flow dividing valve 12 based on the maximum value of the multiple load-side supply pressures and the maximum values ​​of the first and second travel-side supply pressures. Therefore, the control device 17 can adjust the aperture of the first passage 26 and the second passage 27 in accordance with the highest supply pressure to the travel motors 2, 3 and the hydraulic cylinders 4-6. Therefore, the control device 17 can adjust the aperture of the first passage 26 and the second passage 27, which are throttled against the travel-side supply pressure, in accordance with the maximum pressure of the three load-side supply pressures. This makes it possible to adjust the flow rate of hydraulic fluid flowing through the travel-system hydraulic circuit 13 in accordance with the largest load acting on the load actuators 4-6.

[0046] [Second embodiment] The hydraulic drive system 1A of the second embodiment is similar in configuration to the hydraulic drive system 1 of the first embodiment. Therefore, the configuration of the hydraulic drive system 1A of the second embodiment will be mainly described in terms of differences from the hydraulic drive system 1 of the first embodiment, and the same components will be assigned the same reference numerals and descriptions thereof will be omitted. The same applies to the hydraulic drive system 1B of the third embodiment described later.

[0047] As shown in Fig. 2, the hydraulic drive system 1A of the second embodiment includes a hydraulic pump 11, a flow dividing valve 12A, a traveling system hydraulic circuit 13, a cargo handling system hydraulic circuit 14, traveling side pressure sensors 15 and 16, and a control device 17. More specifically, the hydraulic drive system 1A further includes cargo side pressure sensors 18-20, a traveling system operating device 21, and a cargo handling system operating device 22. The flow dividing valve 12A includes a flow dividing spool 12Aa. The flow dividing spool 12Aa moves to a third position A3 in addition to a first position A1 and a second position A2 in response to an input opening signal. In the third position A3, the flow dividing spool 12Aa opens both the first passage 26 and the second passage 27. More specifically, the flow dividing spool 12Aa moves from the first position A1 to the second position A2 via the third position A3, and then from the second position A2 to the third position A3 and back to the first position A1.

[0048] The opening degree of the first passage 26 is maximum between the second position A2 and the third position A3. While the diversion spool 12Aa is moving from the third position A3 to the first position A1, the opening degree of the first passage 26 is narrowed according to the stroke amount of the diversion spool 12Aa. Meanwhile, the opening degree of the second passage 27 is maximum between the first position A1 and the third position A3. While the diversion spool 12Aa is moving from the third position A3 to the second position A2, the opening degree of the second passage 27 is narrowed according to the stroke amount of the diversion spool 12Aa. That is, the diversion spool 12Aa opens the first passage 26 and the second passage 27 to their maximum opening degrees when in the third position A3.

[0049] In the hydraulic drive unit 1A of the second embodiment, by moving the flow dividing spool 12Aa to the third position A3, the opening degrees of each of the first passage 26 and the second passage 27 are increased. Therefore, the pressure loss in the flow dividing valve 12 can be reduced.

[0050] In addition, the hydraulic drive system 1A of the second embodiment has the same effects as those of the hydraulic drive system 1 of the first embodiment.

[0051] [Third embodiment] The hydraulic drive system 1B of the third embodiment includes a hydraulic pump 11, a flow dividing valve 12, a traveling system hydraulic circuit 13B, a cargo handling system hydraulic circuit 14, a supply pressure selection circuit 30, a traveling side pressure sensor 15B, and a control device 17B. More specifically, the hydraulic drive system 1B further includes cargo handling side pressure sensors 18-20, a traveling system operating device 21, and a cargo handling system operating device 22. The traveling system hydraulic circuit 13B includes a first traveling directional control valve 31B and a second traveling directional control valve 32B.

[0052] The first traveling directional control valve 31B is connected to the first inner passage 34. The first inner passage 34 is connected to the first passage 26 via the first traveling directional control valve 31B. The first traveling directional control valve 31B controls the opening between the first inner passage 34 and the first passage 26 depending on the position of the first traveling spool 31a. Therefore, the first traveling-side supply pressure is output to the first inner passage 34. In addition, the first inner passage 34, together with the first passage 26, is connected to one of the two supply / discharge ports 2a, 2b of the first traveling motor 2. More specifically, the first inner passage 34 is connected to one of the supply / discharge ports 2a, 2b depending on the position of the first traveling spool 31a. The other of the supply / discharge ports 2a, 2b is connected to the tank 28.

[0053] The second traveling directional control valve 32B is connected to the second inner passage 35. The second inner passage 35 is connected to the first passage 26 via the second traveling directional control valve 32B. The second traveling directional control valve 32B controls the opening between the second inner passage 35 and the first passage 26 depending on the position of the second traveling spool 32a. Therefore, the second traveling-side supply pressure is output to the second inner passage 35. The second inner passage 35, together with the first passage 26, is connected to one of the two supply / discharge ports 3a, 3b of the second traveling motor 3. More specifically, the second inner passage 35 is connected to one of the supply / discharge ports 3a, 3b depending on the position of the second traveling spool 32a. The other of the supply / discharge ports 3a, 3b is connected to the tank 28.

[0054] The supply pressure selection circuit 30 has two check valves 30a, 30b. The supply pressure selection circuit 30 is connected to a first intermediate passage 34 and a second intermediate passage 35. The supply pressure selection circuit 30 acquires the first traveling side supply pressure and the second traveling side supply pressure from the intermediate passages 34, 35. The supply pressure selection circuit 30 selects and outputs the higher of the first traveling side supply pressure and the second traveling side supply pressure.

[0055] One check valve 30a is connected to the first intermediate passage 34, and the other check valve 30b is connected to the second intermediate passage 35. The two check valves 30a, 30b are connected to each other downstream. Each of the two check valves 30a, 30b allows hydraulic fluid to flow in one direction from the intermediate passages 34, 35 to the junction and prevents hydraulic fluid from flowing in the opposite direction. Therefore, the supply pressure selection circuit 30 selects and outputs the higher of the first travel-side supply pressure and the second travel-side supply pressure through the two check valves 30a, 30b.

[0056] The first running-side pressure sensor 15B is connected to the supply pressure selection circuit 30. The higher of the first running-side supply pressure and the second running-side supply pressure is output to the first running-side pressure sensor 15B from the supply pressure selection circuit 30. Therefore, the first running-side pressure sensor 15B detects the higher of the first running-side supply pressure and the second running-side supply pressure based on the supply pressure output from the supply pressure selection circuit 30.

[0057] The control device 17B controls the operation of the traveling system hydraulic circuit 13B and the cargo handling system circuit 14, similarly to the control device 17. The control device 17B outputs an opening signal to the flow diverter valve 12 in accordance with the traveling side supply pressure detected by the traveling side pressure sensor 15B and the cargo handling side supply pressure detected by the cargo handling side pressure sensors 18-20. Therefore, the flow diverter spool 12a moves to a position in accordance with the traveling side supply pressure detected by the traveling side pressure sensor 15B and the cargo handling side supply pressure detected by the cargo handling side pressure sensors 18-20.

[0058] The hydraulic drive system 1B of the third embodiment operates in the same manner as the hydraulic drive system 1 of the first embodiment.

[0059] In the hydraulic drive unit 1B of the third embodiment, the supply pressure selection circuit 30 selects the higher of the first running-side supply pressure and the second running-side supply pressure and outputs it to the running-side pressure sensor 15A, which allows the number of running-side pressure sensors 15A to be reduced.

[0060] In addition, the hydraulic drive unit 1B of the third embodiment has the same functions and effects as the first embodiment.

[0061] [Other embodiments] In the hydraulic drive systems 1, 1A, and 1B of the first to third embodiments, the traveling system hydraulic circuit 13 supplies two traveling motors 2 and 3, but the number may be one, and any number is acceptable. Similarly, the number of cargo handling actuators supplied by the cargo handling system hydraulic circuit 14 is also not important. Furthermore, the cargo handling actuators supplied by the cargo handling system hydraulic circuit 14 are not limited to hydraulic cylinders, and may be hydraulic motors.

[0062] Furthermore, the travel system hydraulic circuits 13, 13B and the cargo handling system hydraulic circuit 14 in the hydraulic drive systems 1, 1A, 1B of the first to third embodiments are not limited to the structures described above. The travel system hydraulic circuits 13, 13B and the cargo handling system hydraulic circuit 14 may be circuits that can supply hydraulic fluid to the travel motors 2, 3 and the hydraulic cylinders 4-6. Furthermore, in the hydraulic drive systems 1, 1A, 1B, the control devices 17, 17B may operate the travel motors 2, 3 and the cargo handling actuators 4-6 according to a pre-stored program. The control devices 17, 17B obtain hydraulic pressure directly from the travel side pressure sensors 15, 16, 15B and the cargo handling side pressure sensors 18-20, but may obtain hydraulic pressure indirectly, for example, via a device not shown.

[0063] The hydraulic drive systems 1C and 1D may be configured as follows: That is, in the hydraulic drive system 1C, travel-side pressure sensors 15 and 16 may be connected to the middle passages 34 and 35, respectively, as shown in FIG.

[0064] 5, in the hydraulic drive unit 1D, in the travel system hydraulic circuit 12D, supply pressure detection ports 31b, 32b may be formed in each of the first travel direction control valve 31D and the second directional control valve 32D instead of the middle passages 34, 35. In this case, the supply pressure selection circuit 30 is connected to each of the supply pressure detection ports 31b, 32b, and acquires the first travel-side supply pressure and the second travel-side supply pressure from each of the supply pressure detection ports 31b, 32b. Note that in the hydraulic drive unit 1D, travel-side pressure sensors 15, 16 may be connected to each of the supply pressure detection ports 31b, 32b. [Explanation of symbols]

[0065] 1, 1A~1D Hydraulic drive unit 2. First traction motor 3. Second traction motor 4 Hydraulic cylinder (load handling actuator) 5 Hydraulic cylinder (load handling actuator) 6 Hydraulic cylinder (load handling actuator) 11 Hydraulic pump 12,12A Diverter Valve 12a, 12Aa shunt spool 13. Traveling system hydraulic circuit 14 Cargo handling hydraulic circuit 15, 15B First travel side pressure sensor 16 Second travel side pressure sensor 17 Control device 18 Loading side pressure sensor 19 Loading side pressure sensor 20 Loading side pressure sensor 25 Pump passage 26 1st aisle 27 2nd aisle 30 Supply pressure selection circuit 31, 31B, 31C First travel direction control valve 32, 32B, 32C Second travel direction control valve 41 Directional control valve for cargo handling 42 Directional control valve for cargo handling 43 Directional control valve for cargo handling A1 1st position A2 2nd position A3 3rd position

Claims

1. A hydraulic drive device that supplies hydraulic fluid to each of a traveling motor and a cargo handling actuator, a hydraulic pump that discharges hydraulic fluid; a flow dividing valve that divides a pump passage connected to the hydraulic pump into a first passage and a second passage and changes the opening degree of each of the first passage and the second passage in response to an input opening degree signal; a travel system hydraulic circuit connected to the first passage and controlling the flow of hydraulic fluid to the travel motor; a cargo handling hydraulic circuit connected to the second passage and controlling the flow of hydraulic fluid to the cargo handling actuator; a travel-side pressure sensor that detects a travel-side supply pressure that is a supply pressure to the travel motor; a control device that outputs an opening degree signal to the flow dividing valve to control the opening degree of the first passage and the opening degree of the second passage in accordance with the traveling-side supply pressure detected by the traveling-side pressure sensor; a cargo-handling-side pressure sensor that detects a cargo-handling-side supply pressure that is a supply pressure to the cargo-handling actuator; The control device outputs an opening degree signal to the diverter valve to control the opening degree of the first passage and the opening degree of the second passage in accordance with the traveling-side supply pressure detected by the traveling-side pressure sensor and the loading-side supply pressure detected by the loading-side pressure sensor.

2. the flow diverter valve includes a flow diverter spool; 2. The hydraulic drive unit according to claim 1, wherein the flow dividing spool moves to a first position where the flow dividing spool reduces the opening of the first passage and a second position where the flow dividing spool reduces the opening of the second passage.

3. 3. The hydraulic drive system according to claim 2, wherein the flow dividing spool is moved to a third position that opens both the first passage and the second passage.

4. The travel-side pressure sensors include a first travel-side pressure sensor and a second travel-side pressure sensor, the travel system hydraulic circuit supplies hydraulic fluid to the first travel motor and the second travel motor, which are the travel motors; the first travel-side pressure sensor detects a first travel-side supply pressure that is a supply pressure to the first travel motor; the second travel-side pressure sensor detects a second travel-side supply pressure that is a supply pressure to the second travel motor; 4. The hydraulic drive system according to claim 1, wherein the control device controls the opening degree of the first passage and the opening degree of the second passage in response to a first traveling side supply pressure detected by the first traveling side pressure sensor and a second traveling side supply pressure detected by the second traveling side pressure sensor.

5. the traveling system hydraulic circuit includes a first traveling directional control valve that controls the flow of hydraulic fluid to the first traveling motor, and a second traveling directional control valve that controls the flow of hydraulic fluid to the second traveling motor, the first travel-side pressure sensor detects the hydraulic pressure of hydraulic fluid supplied from the first travel directional control valve to the first travel motor; 5. The hydraulic drive system according to claim 4, wherein the second travel-side pressure sensor detects the hydraulic pressure of the hydraulic fluid supplied from the second travel direction control valve to the second travel motor.

6. A hydraulic drive device that supplies hydraulic fluid to a first travel motor, a second travel motor, and a cargo handling actuator, a hydraulic pump that discharges hydraulic fluid; a flow dividing valve that divides a pump passage connected to the hydraulic pump into a first passage and a second passage and changes the opening degree of each of the first passage and the second passage in response to an input opening degree signal; a travel system hydraulic circuit connected to the first passage and controlling the flow of hydraulic fluid to the first travel motor and the second travel motor; a cargo handling hydraulic circuit connected to the second passage and controlling the flow of hydraulic fluid to the cargo handling actuator; a travel-side pressure sensor for detecting a travel-side supply pressure; a supply pressure selection circuit that outputs the higher of a first running-side supply pressure that is a supply pressure to the first traveling motor and a second running-side supply pressure that is a supply pressure to the second traveling motor as the running-side supply pressure to the running-side pressure sensor; a control device that outputs an opening degree signal to the flow dividing valve to control the opening degree of the first passage and the opening degree of the second passage in accordance with the traveling-side supply pressure detected by the traveling-side pressure sensor.

7. Further comprising a plurality of load-side pressure sensors; the cargo handling hydraulic circuit supplies hydraulic fluid to each of a plurality of cargo handling actuators including the cargo handling actuator; each of the plurality of cargo-side pressure sensors detects a supply pressure to each of the plurality of cargo-side actuators; 7. The hydraulic drive system according to claim 1, wherein the control device controls the opening degree of the first passage and the opening degree of the second passage in response to a traveling-side supply pressure detected by the traveling-side pressure sensor and a plurality of loading-side supply pressures detected by the plurality of loading-side pressure sensors.

8. the cargo handling hydraulic circuit includes a plurality of cargo handling directional control valves, the plurality of cargo handling directional control valves control the flow of hydraulic fluid supplied to each of the plurality of cargo handling actuators; 8. The hydraulic drive system according to claim 7, wherein each of the plurality of cargo-side pressure sensors detects a supply pressure of hydraulic fluid supplied from a corresponding cargo-handling directional control valve to the cargo-handling actuator.

9. 9. The hydraulic drive system according to claim 7, wherein the control device operates the flow dividing valve based on a maximum value among a plurality of loading-side supply pressures and a maximum value among first and second traveling-side supply pressures.

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