Hydraulic drive device

Abstract

The present invention provides a hydraulic drive device capable of suppressing a decrease in the operating speed of an attachment / detachment actuator when a travel motor and the attachment / detachment actuator are operated at the same time. This hydraulic drive device supplies a hydraulic fluid to a travel motor and a loading / unloading actuator, and is provided with: a hydraulic pump that is connected to a pump passage and discharges the hydraulic fluid to the pump passage; a travel system hydraulic circuit connected to a first passage connected to the pump passage and controlling the flow of the hydraulic fluid to the travel motor; a handling system hydraulic circuit connected to a second passage connected to the pump passage and controlling the flow of the working fluid to the handling actuator; a flow rate control valve which is provided in the first passage and which changes the opening degree in accordance with the opening degree signal; and a control device for controlling the opening degree of the flow rate control valve by outputting the opening degree signal to the flow rate control valve.

Description

Technical Field

[0001] The present invention relates to a hydraulic drive device for supplying working fluid to a travel motor and a loading and unloading actuator. Background Art

[0002] In practice, a single pump system is provided in which the hydraulic source of the travel motor and the loading and unloading actuator of the construction machinery is a single pump. As a hydraulic drive device of the single pump system, for example, a hydraulic circuit such as Patent Document 1 is known. In the hydraulic circuit of Patent Document 1, the pump is connected to the travel motor and the loading and unloading actuator via a first pump line and a second pump line, respectively. A priority valve is 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 reduces the opening of the second pump line. As a result, the pressure oil flows to the travel motor preferentially.

[0003] Prior art literature: Patent Literature: Patent document 1: Japanese Patent Application Publication No. 2020-026828. Summary of the invention

[0004] Problems to be solved by the invention: In the hydraulic circuit of Patent Document 1, when the travel motor and the loading and unloading actuator are operated simultaneously, the priority valve is throttled to allow the working fluid to flow to the travel motor first, thereby ensuring the amount of working fluid supplied to the travel motor. On the other hand, the flow rate of the working fluid flowing in the loading and unloading actuator is reduced. Therefore, the operating speed of the loading and unloading actuator may be reduced.

[0005] Therefore, an object of the present invention is to provide a hydraulic drive device that can suppress a decrease in the operating speed of the loading and unloading actuator when a travel motor and the loading and unloading actuator are operated simultaneously.

[0006] Means of solving the problem: The hydraulic drive device of the present invention is a hydraulic drive device that supplies working fluid to a travel motor and a loading and unloading actuator, and comprises: a hydraulic pump connected to a pump passage to discharge working fluid to the pump passage; a travel system hydraulic circuit connected to a first passage connected to the pump passage to control the flow of working fluid to the travel motor; a loading and unloading system hydraulic circuit connected to a second passage connected to the pump passage to control the flow of working fluid to the loading and unloading actuator; a flow control valve disposed in the first passage to change the opening according to an opening signal; and a control device that controls the opening of the flow control valve by outputting an opening signal to the flow control valve.

[0007] According to the present invention, the control device controls the opening of the flow control valve by outputting an opening signal to the flow control valve. Therefore, the control device reduces the opening of the flow control valve by outputting an opening signal to the flow control valve, thereby enabling the working fluid to flow preferentially to the hydraulic circuit of the loading and unloading system. Thus, the reduction in the action speed of the loading and unloading actuator can be suppressed.

[0008] Effect of the invention: According to the present invention, when the travel motor and the loading and unloading actuator are operated simultaneously, it is possible to suppress a decrease in the operating speed of the loading and unloading actuator. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a circuit diagram showing the structure of a hydraulic drive device according to an embodiment of the present invention; Figure 2 It is shown Figure 1 A block diagram of a control block of a control device of a hydraulic drive device; Explanation of symbols: 1Hydraulic drive device 21st travel motor (travel motor) 3 Second travel motor (travel motor) 4 Boom cylinder (loading and unloading actuator) 5 Stick cylinder (loading and unloading actuator) 6 Bucket cylinder (loading and unloading actuator) 11Hydraulic pump 12 Travel system hydraulic circuit 13Hydraulic circuit of loading and unloading system 14Flow control valve 15 Discharge pressure sensor 16 Driving side pressure sensor 17 Boom pressure sensor (loading and unloading side pressure sensor) 18 Arm pressure sensor (loading and unloading side pressure sensor) 19 Bucket pressure sensor (loading and unloading side pressure sensor) 20 Control device 25 Pump access 26 First Passage 27 Second Passage 31 First travel directional control valve 32 Second travel directional control valve 33 First pressure compensation valve 34 Second pressure compensation valve 41 Directional control valve for boom (direction control valve for loading and unloading) 42 Directional control valve for bucket arm (direction control valve for loading and unloading) 43 Directional control valve for bucket (directional control valve for loading and unloading). DETAILED DESCRIPTION

[0010] Hereinafter, a hydraulic drive device 1 according to an embodiment of the present invention will be described with reference to the above-mentioned drawings. In addition, the directional concepts used in the following description are used only for the convenience of description, and the structural orientation of the invention is not limited to the directions. Furthermore, the hydraulic drive device 1 described below is only an embodiment of the present invention. Therefore, the present invention is not limited to the embodiment, and additions, deletions, and changes can be made within the scope of the main purpose of the invention.

[0011] Figure 1 The hydraulic drive device 1 shown is provided in a work vehicle (not shown) including travel motors 2 and 3 and loading and unloading actuators 4 to 6. The work vehicle is, for example, a construction vehicle such as a hydraulic excavator and a hydraulic crane, and an industrial vehicle such as a lift. In the present embodiment, the hydraulic drive device 1 is provided in a hydraulic excavator as an example of a work vehicle. The hydraulic excavator includes a vehicle body and a work machine in addition to the hydraulic drive device 1.

[0012] The vehicle body is, for example, a track-type device, including a pair of left and right tracks (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 tracks. In addition, the vehicle body can also be a wheeled device, as long as it is a travelable device. The travel motors 2, 3 are hydraulic motors and drive the left and right tracks respectively. In more detail, the travel motors 2, 3 have two supply and discharge ports 2a, 2b, 3a, 3b respectively. The travel motors 2, 3 rotate forward when the working fluid is supplied to the supply and discharge ports 2a, 3a on one side, and reverse when the working fluid is supplied to the supply and discharge ports 2b, 3b on the other side.

[0013] The working machine is rotatably mounted on the vehicle body. The working machine includes a boom, an arm, a bucket (none of which is shown in the figure) and a plurality of hydraulic cylinders 4 to 6. The hydraulic cylinders 4 to 6 as an example of a loading and unloading actuator are, for example, a boom cylinder 4, an arm cylinder 5 and a bucket cylinder 6, which are respectively mounted on the boom, the arm and the bucket. The working machine moves the boom, the arm and the bucket respectively by extending and retracting the three hydraulic cylinders 4 to 6. Thus, the working machine can perform various operations.

[0014] <Hydraulic drive unit> The hydraulic drive device 1 includes a hydraulic pump 11, a travel system hydraulic circuit 12, a loading and unloading system hydraulic circuit 13, a flow control valve 14, a discharge pressure sensor 15, a travel side pressure sensor 16, and a control device 20. In more detail, the hydraulic drive device 1 also includes loading and unloading side pressure sensors 17 to 19, a travel system operating device 21, and a loading and unloading system operating device 22.

[0015] The hydraulic drive device 1 is a so-called single pump system, and a hydraulic pump 11 supplies working fluid to the travel motors 2, 3 and three hydraulic cylinders 4 to 6. The hydraulic drive device 1 supplies working fluid to the first travel motor 2 and the second travel motor 3, respectively, to operate the crawlers corresponding to the travel motors 2 and 3. Thus, the hydraulic drive device 1 can drive the hydraulic excavator. Furthermore, the hydraulic drive device 1 supplies working fluid to the hydraulic cylinders 4 to 6, thereby operating the corresponding booms, arms and buckets. Thus, the hydraulic drive device 1 can enable the hydraulic excavator to perform various operations.

[0016] <Hydraulic pump> The hydraulic pump 11 discharges working fluid. To explain in more detail, the hydraulic pump 11 is connected to a driving source (e.g., an engine and a motor) not shown in the figure. The hydraulic pump 11 is connected to a pump passage 25. The hydraulic pump 11 is driven to rotate by the driving source, thereby discharging working fluid to the pump passage 25. The pump passage 25 is connected to a first passage 26 and a second passage 27, respectively.

[0017] <Travel system hydraulic circuit> The travel system hydraulic circuit 12 is connected to the first passage 26. In addition, the travel system hydraulic circuit 12 is connected to the two travel motors 2 and 3. The travel system hydraulic circuit 12 controls the flow of the working fluid to the travel motors 2 and 3. In more detail, the travel system hydraulic circuit 12 supplies the working fluid that flows (in the present embodiment, the flow direction and flow rate) in accordance with the input first travel command signal and the second travel command signal to the first travel motor 2 and the second travel motor 3. The travel system hydraulic circuit 12 includes a first travel directional control valve 31 and a second travel directional control valve 32. In addition, the travel system hydraulic circuit 12 also includes a first pressure compensation valve 33 and a second pressure compensation valve 34.

[0018] The first travel directional control valve 31 has a first travel valve core 31a. The first travel directional control valve 31 controls the flow of the working fluid to the first travel motor 2. In more detail, the first travel directional 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 valve core 31a performs a stroke according to the input first travel command signal. As a result, the connection destinations of the supply and discharge ports 2a and 2b are switched to the first passage 26 and the tank 28, respectively. The first travel valve core 31a changes the opening degree by the stroke. That is, the first travel valve core 31a changes the opening degree according to the first travel command signal. Therefore, the working fluid of the direction and flow rate corresponding to the first travel command signal is supplied from the first travel directional control valve 31 to the first travel motor 2. As a result, the first travel directional control valve 31 rotates the first travel motor 2 forward and reverse according to the first travel command signal, and rotates the first travel motor 2 at a speed corresponding to the first travel command signal. In the present embodiment, the first travel directional control valve 31 is an electrically controlled directional control valve.

[0019] The second travel directional control valve 32 has a second travel valve core 32a. The second travel directional control valve 32 controls the flow of the working fluid to the second travel motor 3. To explain in more detail, the second travel directional control valve 32 is connected to the first passage 26 in parallel with the first travel directional control valve 31. In addition, the second travel directional control valve 32 is connected to the tank 28 and the two supply and discharge ports 3a and 3b of the second travel motor 3. The second travel valve core 32a performs a stroke according to the input second travel operation command signal. As a result, the connection destinations of the supply and discharge ports 3a and 3b are respectively switched to the first passage 26 and the tank 28. The second travel valve core 32a changes the opening by the stroke. That is, the second travel valve core 32a changes the opening according to the second travel command signal. Therefore, the working fluid of the direction and flow rate corresponding to the second travel command signal is supplied from the second travel directional control valve 32 to the second travel motor 3. Thus, the second travel directional control valve 32 rotates the second travel motor 3 forward and reverse according to the second travel command signal and rotates the second travel motor 3 at a speed corresponding to the second travel command signal. In this embodiment, the second travel directional control valve 32 is an electrically controlled directional control valve.

[0020] The first pressure compensation valve 33 maintains the front-rear differential pressure of the first travel directional control valve 31 at a predetermined pressure. The first pressure compensation valve 33 includes a valve core 33a and a spring 33b. The valve core 33a changes its opening according to its position. In addition, the first upstream pressure and the first downstream pressure of the first travel directional control valve 31 act in directions opposing each other. The first upstream pressure is the hydraulic pressure of the working fluid introduced from the first passage 26 to the first travel directional control valve 31, and the first downstream pressure is the hydraulic pressure of the working fluid supplied from the first travel directional control valve 31 to the first travel motor 2. The spring 33b urges the valve core 33a in a direction opposing the first upstream pressure. Therefore, the first travel directional control valve 31 moves the valve core 33a in such a manner that the front-rear differential pressure of the first travel directional control valve 31 becomes a predetermined pressure corresponding to the urging force of the spring 33b. As a result, the front-rear differential pressure of the first travel directional control valve 31 becomes a predetermined pressure corresponding to the urging force of the spring 33b. Therefore, the flow rate of the hydraulic fluid supplied to the first travel motor 2 is controlled to a flow rate according to the opening degree of the first travel directional control valve 31 .

[0021] The second pressure compensation valve 34 maintains the front-rear differential pressure of the second travel directional control valve 32 at a predetermined pressure. The second pressure compensation valve 34 includes a valve core 34a and a spring 34b. The valve core 34a adjusts the opening according to its position. In addition, the second upstream pressure and the second downstream pressure of the second travel directional control valve 32 act in directions opposing each other. The second upstream pressure is the hydraulic pressure of the working fluid introduced from the first passage 26 to the second travel directional control valve 32, and the second downstream pressure is the hydraulic pressure of the working fluid supplied from the second travel directional control valve 32 to the second travel motor 3. The spring 34b urges the valve core 34a in the direction opposing the second upstream pressure. Therefore, the second travel directional control valve 32 moves the valve core 34a in such a manner that the front-rear differential pressure of the second travel directional control valve 32 becomes a predetermined pressure corresponding to the urging force of the spring 34b. As a result, the front-rear differential pressure of the second travel directional control valve 32 becomes a predetermined pressure. Therefore, the flow rate of the working fluid supplied to the second travel motor 3 is controlled to a flow rate corresponding to the opening of the second travel directional control valve 32.

[0022] <Hydraulic circuit of loading and unloading system> The loading and unloading system hydraulic circuit 13 is connected to the second passage 27 and the three hydraulic cylinders 4 to 6. The loading and unloading system hydraulic circuit 13 supplies working fluid to the three hydraulic cylinders 4 to 6, respectively. The loading and unloading system hydraulic circuit 13 controls the flow of working fluid to each hydraulic cylinder 4 to 6 according to the loading and unloading operation signal (in the present embodiment, the boom command signal, the dipper arm command signal, and the bucket command signal described in detail later). In more detail, the loading and unloading system hydraulic circuit 13 supplies working fluid that flows (in the present embodiment, the flow direction and flow rate) in accordance with the input loading and unloading operation signal to the three hydraulic cylinders 4 to 6. The loading and unloading system hydraulic circuit 13 includes a plurality of loading and unloading directional control valves 41 to 43. In the present embodiment, the loading and unloading system hydraulic circuit 13 includes three loading and unloading directional control valves 41 to 43, such as a boom directional control valve 41, an arm directional control valve 42, and a bucket directional control valve 43.

[0023] Each loading and unloading directional control valve 41 to 43 corresponds to each hydraulic cylinder 4 to 6. Moreover, each loading and unloading directional control valve 41 to 43 controls the flow rate of the working fluid supplied to the corresponding hydraulic cylinder 4 to 6 by changing the opening. That is, the boom directional control valve 41 controls the flow of the working fluid to the boom cylinder 4. The arm directional control valve 42 controls the flow of the working fluid to the arm cylinder 5. The bucket directional control valve 43 controls the flow of the working fluid to the bucket cylinder 6. Each loading and unloading directional control valve 41 to 43 is connected to the second passage 27 in parallel with each other. In addition, each loading and unloading directional control valve 41 to 43 is connected to the tank 28, the rod side ports 4a, 5a, 6a and the head side ports 4b, 5b, 6b of the corresponding hydraulic cylinders 4 to 6, respectively.

[0024] To explain in more detail, each loading and unloading directional control valve 41 to 43 has a loading and unloading valve core 41a to 43a. Each loading and unloading valve core 41a to 43a performs a stroke according to a boom command signal, a dipper arm command signal, and a bucket command signal, which are examples of loading and unloading operation signals. As a result, the connection destinations of the rod side ports 4a to 6a and the head side ports 4b to 6b are respectively switched to the second passage 27 and the tank 28. In addition, each loading and unloading valve core 41a to 43a changes the opening by the stroke. That is, the loading and unloading valve core 41a to 43a changes the opening according to the loading and unloading operation signal. Therefore, the working fluid of the direction and flow rate corresponding to each command signal is supplied from each loading and unloading directional control valve 41 to 43 to the corresponding hydraulic cylinder 4 to 6. As a result, the loading and unloading directional control valve 41 to 43 can cause the corresponding hydraulic cylinder 4 to 6 to expand and contract at a speed corresponding to each command signal. In addition, in the present embodiment, the loading and unloading directional control valves 41 to 43 are also electrically controlled directional control valves.

[0025] <Flow Control Valve> The flow control valve 14 is an electrically controlled valve. The flow control valve 14 is, for example, an electrically controlled slide valve, and includes a control valve core 14a. The flow control valve 14 is interposed between the pump passage 25 and the first passage 26. In other words, the pump passage 25 is connected to the first passage 26 via the flow control valve 14. The flow control valve 14 changes the opening according to the input opening signal. In more detail, the flow control valve 14 throttles the flow of the working fluid flowing in the first passage 26 according to the input opening signal. As a result, the working fluid preferentially flows into the loading and unloading system hydraulic circuit 13.

[0026] <Discharge pressure sensor> The discharge pressure sensor 15 detects the hydraulic pressure of the working fluid discharged from the hydraulic pump 11, that is, the discharge pressure. In more detail, the discharge pressure sensor 15 is provided in the pump passage 25. That is, the discharge pressure sensor 15 is provided on the upstream side of the flow control valve 14. And the discharge pressure sensor 15 detects the hydraulic pressure of the working fluid flowing in the pump passage 25.

[0027] <Driving side pressure sensor> The travel side pressure sensor 16 detects the travel side supply pressure which is the hydraulic pressure of the working fluid flowing in the first passage 26. In other words, the travel side pressure sensor 16 detects the hydraulic pressure of the working fluid supplied to the travel system hydraulic circuit 12. In more detail, the travel side pressure sensor 16 is provided in the first passage 26. That is, the travel side pressure sensor 16 is provided on the downstream side of the flow control valve 14.

[0028] <Loading and unloading side pressure sensor> The loading and unloading side pressure sensors 17 to 19 correspond to the hydraulic cylinders 4 to 6. Moreover, the loading and unloading side pressure sensors 17 to 19 detect the loading and unloading side supply pressure as the supply pressure to the corresponding hydraulic cylinders 4 to 6. In more detail, the loading and unloading side pressure sensors 17 to 19 are, for example, a boom pressure sensor 17, an arm pressure sensor 18, and a bucket pressure sensor 19, respectively, and detect the supply pressure supplied to the boom cylinder 4, the arm cylinder 5, and the bucket cylinder 6, respectively. The loading and unloading side pressure sensors 17 to 19 are arranged on the downstream side of each directional control valve 41 to 43. In the present embodiment, the loading and unloading side pressure sensors 17 to 19 are connected to the rod side ports 4a to 6a and the head side ports 4b to 6b of the hydraulic cylinders 4 to 6, respectively. Moreover, the loading and unloading side pressure sensors 17 to 19 detect the hydraulic pressure of the working fluid supplied to the rod side ports 4a to 6a and the head side ports 4b to 6b of the hydraulic cylinders 4 to 6.

[0029] <Travel system operating device> The travel system operating device 21 is a device used by the driver to operate the travel motors 2 and 3. The travel system operating device 21 is, for example, travel pedals 21a and 21b as operating tools. The travel pedals 21a and 21b can be tilted respectively. Each travel pedal 21a and 21b can be tilted in one direction and the other direction (for example, forward and backward) of a specified direction, for example. The travel system operating device 21 outputs a travel operation instruction corresponding to the operation direction and the operation amount (in this embodiment, the tilt direction and the tilt amount). In addition, the operating tool provided by the travel system operating device 21 can also be in other forms such as an operating lever, an operating panel, etc., and its form does not matter.

[0030] <Loading and unloading system operating device> The loading and unloading system operating device 22 is a device used by the driver to operate the accessory (in the present embodiment, the bucket). To explain in more detail, the operating tools of the loading and unloading system operating device 22 include loading and unloading operating levers 22a, 22b. Each loading and unloading operating lever 22a, 22b can be tilted. In the present embodiment, each loading and unloading operating lever 22a, 22b can be tilted in the front, rear, left and right directions, for example. The loading and unloading system operating device 22 outputs loading and unloading operation instructions corresponding to the operation direction and operation amount (in the present embodiment, the tilt direction and tilt amount). In addition, the operating tools of the loading and unloading system operating device 22 are not limited to the loading and unloading operating levers 22a, 22b, but can also be other forms such as an operating panel.

[0031] <Control device> The control device 20 controls the operation of the travel system hydraulic circuit 12 according to the travel operation command. In more detail, the control device 20 obtains the travel operation command output from the travel system operating device 21. Then, the control device 20 controls the movement of each of the travel direction control valves 31 and 32 (that is, the position of each valve core 31a and 32a) according to the travel operation command. In this embodiment, the control device 20 outputs the first and second travel command signals respectively according to the travel operation command. Then, the travel motors 2 and 3 rotate in the direction and rotation speed corresponding to the travel operation command, so that the hydraulic excavator can be moved in the direction and speed corresponding to the travel operation command.

[0032] Furthermore, the control device 20 controls the operation of the loading and unloading system hydraulic circuit 13 according to the loading and unloading operation instructions. To explain in more detail, the control device 20 obtains the loading and unloading operation instructions output from the loading and unloading system operating device 22. Then, the control device 20 controls the movement of each loading and unloading directional control valve 41 to 43 (that is, the position of each valve core 41a to 43a) according to the loading and unloading operation instructions. In the present embodiment, the control device 20 outputs a boom command signal, a dipper arm command signal, and a bucket command signal according to the loading and unloading operation instructions. Then, the hydraulic cylinders 4 to 6 extend and retract at a speed corresponding to the loading and unloading operation instructions. As a result, the bucket can be moved in a direction and at a speed corresponding to the loading and unloading operation instructions, so that the hydraulic excavator can perform the desired operation.

[0033] In addition, the control device 20 controls the opening of the flow control valve 14 by outputting an opening signal to the flow control valve 14. In more detail, the control device 20 controls the opening of the first passage 26 by outputting an opening signal corresponding to the travel operation command and the loading and unloading operation command. In addition, the control device 20 outputs an opening signal based on the hydraulic pressure detected by each pressure sensor 15 to 19, thereby supplying the working fluid of the flow rate corresponding to the travel operation command and the loading and unloading operation command to the travel system hydraulic circuit 12 and the loading and unloading system hydraulic circuit 13 with higher accuracy.

[0034] <About the operation of the hydraulic drive unit> In the hydraulic drive device 1, when the travel pedals 21a and 21b of the travel system operating device 21 are operated individually, the travel operation command is output from the travel system operating device 21. In addition, the individual operation refers to the independent operation of the travel pedals 21a and 21b and the loading and unloading operating levers 22a and 22b. In addition, the individual operation includes the simultaneous operation of the travel pedals 21a and 21b and the simultaneous operation of the loading and unloading operating levers 22a and 22b. When the travel operation command is output, the control device 20 opens the flow control valve 14. In this embodiment, the control device 20 outputs an opening signal to make the opening of the flow control valve 14 the maximum opening. On the other hand, the control device 20 closes the connection between the hydraulic pump 11 and the hydraulic cylinders 4 to 6 through the loading and unloading hydraulic circuit 13. That is, the control device 20 closes the connection between the first passage 26 and the hydraulic cylinders 4 to 6 through the loading and unloading directional control valves 41 to 43. In addition, the control device 20 opens the connection between the hydraulic pump 11 and the travel motors 2 and 3 through the travel system hydraulic circuit 12.

[0035] In more detail, the control device 20 is as follows: Figure 2As shown, the target flow rates of the travel motors supplied to the travel motors 2 and 3 are calculated based on the travel operation command. Furthermore, the control device 20 outputs the first and second travel command signals corresponding to the target flow rates of the travel motors. Then, the first travel directional control valve 31 and the second travel directional control valve 32 control the flow of the working fluid relative to the travel motors 2 and 3 to the flow (in this embodiment, the flow direction and flow rate) corresponding to the travel operation command.

[0036] Specifically, the pressure differentials before and after the two travel directional control valves 31 and 32 are the same due to the pressure compensation valves 33 and 34. Therefore, the flow rate of the hydraulic fluid supplied to each travel motor 2 and 3 is a flow rate corresponding to the opening of each travel directional control valve 31 and 32. Therefore, the control device 20 calculates the opening of the first and second travel directional control valves 31 and 32 according to the target flow rate of each travel motor 2 and 3, and outputs the first and second travel command signals corresponding to the calculated openings. As a result, the hydraulic fluid of the flow rate corresponding to the travel operation command (more specifically, the operation amount of the travel pedals 21a and 21b) can be supplied to the travel motors 2 and 3. Therefore, the control device 20 can make the hydraulic excavator perform a travel action corresponding to the operation of the travel pedals 21a and 21b.

[0037] In the hydraulic drive device 1, when the loading and unloading operating levers 22a and 22b of the loading and unloading system operating device 22 are operated individually, the loading and unloading operation command is output from the loading and unloading system operating device 22. Then, the control device 20 throttles the flow control valve 14. In more detail, the control device 20 outputs an opening signal to make the opening of the flow control valve 14 the minimum opening. In addition, the control device 20 Figure 2 As shown in FIG. 1 , the target flow rate of loading and unloading supplied to each hydraulic cylinder 4 to 6 is calculated based on the loading and unloading operation command. In addition, the control device 20 estimates the flow rate (actual flow rate) of the working fluid supplied to each hydraulic cylinder 4 to 6 based on the detected discharge pressure and each loading and unloading side supply pressure. In more detail, the control device 20 estimates the flow rate of the working fluid flowing in each loading and unloading directional control valve 41 to 43 as the flow rate of the working fluid supplied to each hydraulic cylinder 4 to 6 based on the front and rear pressures of each loading and unloading directional control valve 41 to 43, that is, the discharge pressure and each loading and unloading side supply pressure. The control device 20 calculates the opening of each loading and unloading directional control valve 41 to 43 in such a way that the estimated actual flow rate becomes the loading and unloading target flow rate. In addition, the control device 20 outputs the boom command signal, the dipper arm command signal, and the bucket command signal corresponding to each calculated opening. Therefore, the flow of the working fluid relative to the hydraulic cylinder 4 to 6 is controlled to be a flow (in this embodiment, the flow direction and flow rate) corresponding to the loading and unloading operation command through each loading and unloading directional control valve 41 to 43. Thus, the control device 20 can cause the bucket to move in accordance with the operation of the loading and unloading operating levers 22a, 22b.

[0038] When the travel pedals 21a, 21b and the loading and unloading operating levers 22a, 22b are operated simultaneously, the hydraulic drive device 1 operates as follows. That is, the travel operation command is output from the travel system operating device 21, and the loading and unloading operation command is output from the loading and unloading system operating device 22. Figure 2 As shown, the target flow rate of the travel motor is calculated based on the travel operation command. In addition, the control device 20 estimates the flow rate of the working fluid supplied to the travel system hydraulic circuit 12, that is, the actual flow rate on the travel side (that is, equivalent to the total flow rate of the working fluid supplied to the two travel motors 2 and 3) based on the detected discharge pressure and the travel side supply pressure. Moreover, the control device 20 controls the opening of the flow control valve 14 in the form of the actual flow rate on the travel side becoming the target flow rate on the travel side. In addition, the travel side target flow rate is the total flow rate of the travel motor target flow rates of the two travel motors 2 and 3, and is also the flow rate to be supplied to the travel system hydraulic circuit 12.

[0039] Furthermore, in the present embodiment, the control device 20 outputs an opening signal according to the loading and unloading target flow rate and the loading and unloading actual flow rate of each hydraulic cylinder 4 to 6 in addition to the actual flow rate on the travel side and the target flow rate on the travel side. To explain in more detail, the control device 20 calculates the loading and unloading target flow rate of each hydraulic cylinder 4 to 6 based on the loading and unloading operation instruction. Furthermore, the control device 20 estimates the loading and unloading actual flow rate of each hydraulic cylinder 4 to 6 based on the detected discharge pressure and the supply pressure on each loading and unloading side. Moreover, the control device 20 controls the opening of the flow control valve 14 in such a manner that the actual flow rate on the travel side becomes the target flow rate on the travel side and each loading and unloading target flow rate is consistent with each loading and unloading actual flow rate.

[0040] Furthermore, when the control device 20 is operated simultaneously, the travel system hydraulic circuit 12 is controlled as follows. That is, the control device 20 calculates the opening of each travel directional control valve 31, 32 according to the target flow rate of each travel motor 2, 3. In more detail, the front-rear pressure difference of each travel directional control valve 31, 32 is maintained at a predetermined pressure by the pressure compensation valve 33, 34 as described above. Therefore, the control device 20 controls the opening of each travel directional control valve 31, 32 at the same ratio as the target flow rate of each travel motor 2, 3, so that the flow rate introduced into the travel system hydraulic circuit 12 can be supplied to each travel motor 2, 3 at a distribution amount corresponding to the target flow rate of each travel motor 2, 3. Therefore, the control device 20 makes the opening of each travel directional control valve 31, 32 the same opening (in this embodiment, both are the maximum opening) when the target flow rates of each travel motor 2, 3 are the same. On the other hand, when the target flow rate of the first travel motor 2 is half of the target flow rate of the second travel motor 3, the control device 20 makes the opening of the first travel directional control valve 31 half of the opening (in this embodiment, the maximum opening) of the second travel directional control valve 32. The control device 20 controls the opening of each travel directional control valve 31, 32 by outputting the first and second travel command signals corresponding to the calculated openings, respectively. As a result, the flow rate introduced into the travel system hydraulic circuit 12 can be supplied to each travel motor 2, 3 in a distribution amount corresponding to the target flow rate of each travel motor 2, 3. As a result, even when the operation is performed simultaneously, the excavator can be driven in accordance with the operation of the travel pedals 21a, 21b.

[0041] In addition, when the control device 20 is operated simultaneously, the loading and unloading system hydraulic circuit 13 is controlled as follows. That is, the control device 20 outputs a boom command signal, a dipper arm command signal, and a bucket command signal corresponding to the loading and unloading target flow rate of each hydraulic cylinder 4 to 6. In more detail, the control device 20 controls the opening of each loading and unloading directional control valve 41 to 43 based on the loading and unloading target flow rate and the actual flow rate of each hydraulic cylinder 4 to 6. In the present embodiment, the control device 20 controls the opening of each loading and unloading directional control valve 41 to 43 in a form that the actual flow rate of each hydraulic cylinder 4 to 6 becomes each loading and unloading target flow rate. As a result, the control device 20 can supply the working fluid of the flow rate corresponding to the operation of the travel pedals 21a and 21b to each travel motor 2 and 3 with higher accuracy, and can supply the working fluid of the flow rate corresponding to the operation of each loading and unloading operating lever 22a and 22b to each hydraulic cylinder 4 to 6 with higher accuracy.

[0042] In the hydraulic drive device 1 of the present embodiment, the control device 20 controls the opening of the flow control valve 14 by outputting an opening signal to the flow control valve 14. Therefore, the control device 20 can make the working fluid flow preferentially into the loading and unloading system hydraulic circuit 13 by outputting an opening signal to the flow control valve 14 and reducing the opening of the flow control valve 14. As a result, the reduction in the operating speed of the hydraulic cylinders 4 to 6 can be suppressed.

[0043] In the hydraulic drive device 1 of the present embodiment, the control device 20 outputs an opening signal to the flow control valve 14 according to the travel side target flow rate and the travel side actual flow rate flowing in the travel system hydraulic circuit 12. Therefore, the opening of the flow control valve 14 can be controlled in such a way that the travel side actual flow rate becomes the travel side target flow rate. As a result, while the working fluid is preferentially flowed into the loading and unloading system hydraulic circuit 13, the working fluid of the flow rate corresponding to the travel side target flow rate can be flowed into the travel system hydraulic circuit 12. As a result, the travel motors 2 and 3 can be moved at the desired motion speed.

[0044] In the hydraulic drive device 1 of the present embodiment, the control device 20 closes the connection between the hydraulic pump 11 and the hydraulic cylinders 4 to 6 through the loading and unloading system hydraulic circuit 13, and opens the connection between the hydraulic pump 11 and the travel motors 2 and 3 through the travel system hydraulic circuit 12. Thus, the total amount of the working fluid discharged from the hydraulic pump 11 can be introduced into the travel motors 2 and 3 through the travel system hydraulic circuit 12. Thus, only the travel motors 2 and 3 can be moved.

[0045] In the hydraulic drive device 1 of the present embodiment, the first pressure compensation valve 33 maintains the front-rear pressure difference of the first travel directional control valve 31, and the second pressure compensation valve 34 maintains the front-rear pressure difference of the second travel directional control valve 32. In addition, the control device 20 outputs the first travel instruction signal to the first travel directional control valve 31 whose opening is changed according to the first travel instruction signal, and also outputs the second travel instruction signal to the second travel directional control valve 32 whose opening is changed according to the second travel instruction signal. Therefore, the control device 20 can supply the working fluid of the flow rate corresponding to the first travel instruction signal to the first travel motor 2, and supply the working fluid of the flow rate corresponding to the second travel instruction signal to the second travel motor 3. Thus, the control device 20 can control the distribution amount of the flow introduced into the travel system hydraulic circuit 12 to each travel motor 2, 3 according to each travel instruction signal. Therefore, each travel motor 2, 3 can be moved at a desired motion speed.

[0046] In the hydraulic drive device 1 of this embodiment, the control device 20 outputs an opening signal corresponding to the target flow rate of loading and unloading flowing in each hydraulic cylinder 4 to 6 to the flow control valve 14. Therefore, by reducing the opening of the flow control valve 14, the hydraulic cylinders 4 to 6 of the working fluid of the target flow rate of the loading and unloading system can flow in. As a result, each hydraulic cylinder can be moved at a desired speed.

[0047] In the hydraulic drive device 1 of the present embodiment, the control device 20 estimates each actual flow rate of loading and unloading based on the discharge pressure and the supply pressure of each loading and unloading side, and further outputs an opening signal to the flow control valve according to each loading and unloading target flow rate and each loading and unloading flow rate. The control device 20 can flow the working fluid of the driving system target flow rate into the driving system hydraulic circuit 12 with higher accuracy, so it can also flow the working fluid of the loading and unloading system target flow rate into each hydraulic cylinder 4 to 6 with higher accuracy. As a result, each hydraulic cylinder 4 to 6 can be moved at a desired speed.

[0048] [Other embodiments] In the hydraulic drive device 1 of the present embodiment, the number of travel motors 2 and 3 supplied by the travel system hydraulic circuit 12 is two, but it can also be one, and the number does not matter. Moreover, the number of loading and unloading actuators 4 to 6 supplied by the loading and unloading system hydraulic circuit 13 is also irrelevant. In addition, the loading and unloading actuators 4 to 6 supplied by the loading and unloading system hydraulic circuit 13 are not limited to hydraulic cylinders, but can also be hydraulic motors. That is, the loading and unloading system hydraulic circuit 13 can also include, for example, a rotary motor and an optional cylinder. Moreover, the valve core 31a, 32a, 41a to 43a included in each control valve 31, 32, 41 to 43 does not necessarily have to be one. Each control valve 31, 32, 41 to 43 can also include, for example, two valve cores to independently control the inlet flow rate and the outlet flow rate.

[0049] Furthermore, the travel system hydraulic circuit 12 and the loading and unloading system hydraulic circuit 13 in the hydraulic drive device 1 of the present embodiment are not limited to the aforementioned structures. The travel system hydraulic circuit 12 and the loading and unloading system hydraulic circuit 13 can be circuits that can supply working fluid to the travel motors 2, 3 and the hydraulic cylinders 4 to 6. In addition, in the hydraulic drive device 1, the control device 20 can operate the travel motors 2, 3 and the hydraulic cylinders 4 to 6 according to a pre-stored program. The control device 20 directly obtains the hydraulic pressure from the discharge pressure sensor 15, the travel side pressure sensor 16 and the loading and unloading side pressure sensors 17 to 19, but it can also be obtained indirectly through a device not shown in the figure.

[0050] In addition, in the hydraulic drive device 1 of the present embodiment, the first passage 26 and the second passage 27 are connected to the pump passage 25 in a mutually branched form, but they may be connected as follows. That is, the first passage 26 may be connected to the second passage 27 via the flow control valve 14, and may be connected to the pump passage 25 via the flow control valve 14 and the second passage 27. That is, the first passage 26 and the second passage 27 may also be connected in series with the pump passage 25. The hydraulic drive device of such an embodiment also exerts the same effects as the hydraulic drive device 1 of the present embodiment.

[0051] In addition, in the hydraulic drive device 1 of the present embodiment, the control device 20 outputs an opening signal corresponding to the estimated actual travel flow rate and the travel target flow rate to the flow control valve 14, but it is also possible to output an opening signal corresponding to the travel operation instruction and the loading and unloading operation instruction to the flow control valve 14. In more detail, the control device 20 obtains the operation type of the travel pedals 21a, 21b and the loading and unloading operation levers 22a, 22b based on the acquired travel operation instruction and the loading and unloading operation instruction. Here, the operation type refers to the combination of the operation direction and the operation amount of each of the travel pedals 21a, 21b and the loading and unloading operation levers 22a, 22b when each is operated. The control device 20 stores the relationship between the operation type and the opening signal, for example, through a map. The control device 20 selects the opening signal based on the acquired operation type and the map, and outputs the selected opening signal to the flow control valve 14.

[0052] In this way, the control device 20 outputs an opening signal corresponding to the travel operation command and the loading and unloading operation command to the flow control valve 14. Therefore, the opening of the flow control valve can be controlled in such a way that the actual flow rate on the travel side becomes the flow rate corresponding to the travel operation command. As a result, while the working fluid flows preferentially into the loading and unloading system hydraulic circuit, the working fluid of the flow rate corresponding to the travel side target flow rate can flow into the travel system hydraulic circuit. As a result, the travel motor can be moved at the desired motion speed.

[0053] The hydraulic drive device of the first aspect is a hydraulic drive device that supplies working fluid to a travel motor and a loading and unloading actuator, and comprises: a hydraulic pump connected to a pump passage to discharge working fluid to the pump passage; a travel system hydraulic circuit connected to a first passage connected to the pump passage to control the flow of working fluid to the travel motor; a loading and unloading system hydraulic circuit connected to a second passage connected to the pump passage to control the flow of working fluid to the loading and unloading actuator; a flow control valve disposed in the first passage to change the opening according to an opening signal; and a control device that controls the opening of the flow control valve by outputting an opening signal to the flow control valve.

[0054] According to the above aspect, the control device controls the opening of the flow control valve by outputting the opening signal to the flow control valve. Therefore, the control device reduces the opening of the flow control valve by outputting the opening signal to the flow control valve, thereby enabling the working fluid to flow preferentially to the loading and unloading system hydraulic circuit. Thus, the reduction in the action speed of the loading and unloading actuator can be suppressed.

[0055] The hydraulic drive device of the second aspect is further provided with: a discharge pressure sensor for detecting the discharge pressure of the hydraulic pump; and a travel side pressure sensor for detecting the travel side supply pressure of the hydraulic pressure of the working fluid flowing in the first passage; the control device estimates the actual travel side flow rate flowing in the travel system hydraulic circuit based on the discharge pressure and the travel side supply pressure, and outputs an opening signal corresponding to the travel side target flow rate and the travel side actual flow rate flowing in the travel system hydraulic circuit to the flow control valve.

[0056] According to the above aspect, the control device outputs an opening signal to the flow control valve according to the target flow rate on the travel side and the actual flow rate on the travel side flowing in the travel system hydraulic circuit. Therefore, the opening of the flow control valve can be controlled in such a way that the actual flow rate on the travel side becomes the target flow rate on the travel side. As a result, the working fluid can flow into the loading and unloading system hydraulic circuit preferentially, and at the same time, the working fluid with a flow rate corresponding to the target flow rate on the travel side flows into the travel system hydraulic circuit. As a result, the travel motor can be moved at a desired motion speed.

[0057] In the hydraulic drive device of the third aspect, in the hydraulic drive device of the second aspect, the loading and unloading system hydraulic circuit controls the flow of working fluid to the loading and unloading actuator by adjusting the opening between the hydraulic pump and the loading and unloading actuator, and the traveling system hydraulic circuit controls the flow of working fluid to the traveling motor by adjusting the opening between the hydraulic pump and the traveling motor, and the control device closes the connection between the hydraulic pump and the loading and unloading actuator through the loading and unloading system hydraulic circuit, and opens the connection between the hydraulic pump and the traveling motor through the traveling system hydraulic circuit.

[0058] According to the above aspect, the control device closes the connection between the hydraulic pump and the loading and unloading actuator through the loading and unloading system hydraulic circuit, and opens the connection between the hydraulic pump and the traveling motor through the traveling system hydraulic circuit. As a result, the total amount of the working fluid discharged from the hydraulic pump can be introduced into the traveling motor through the traveling system hydraulic circuit. As a result, only the traveling motor can be moved.

[0059] In the hydraulic drive device of the fourth aspect, in the hydraulic drive device of any one of the first to third aspects, the control device controls the action of the hydraulic circuit of the driving system based on the driving operation instruction and controls the action of the hydraulic circuit of the loading and unloading system based on the loading and unloading operation instruction, and outputs an opening signal corresponding to the driving operation instruction and the loading and unloading operation instruction to the flow control valve.

[0060] According to the above aspect, the control device outputs the opening signal corresponding to the driving operation command and the loading and unloading operation command to the flow control valve. Therefore, the opening of the flow control valve can be controlled in such a way that the actual flow rate on the driving side becomes the flow rate corresponding to the driving operation command. As a result, the working fluid can flow into the loading and unloading system hydraulic circuit preferentially, while the working fluid with a flow rate corresponding to the driving side target flow rate flows into the driving system hydraulic circuit. As a result, the driving motor can be moved at the desired action speed.

[0061] In the hydraulic drive device of the fifth aspect, in the hydraulic drive device of any one of the first to fourth aspects, the travel system hydraulic circuit includes: a first travel directional control valve connected to the first travel motor serving as the travel motor and the first passage; a second travel directional control valve connected to the second travel motor and the first passage; a first pressure compensation valve for maintaining the front and rear pressure difference of the first travel directional control valve; and a second pressure compensation valve for maintaining the front and rear pressure difference of the second travel directional control valve.

[0062] According to the above aspect, the first pressure compensation valve maintains the front-rear pressure difference of the first travel directional control valve, and the second pressure compensation valve maintains the front-rear pressure difference of the second travel directional control valve. Therefore, the first travel motor can be supplied with a working fluid of a flow rate corresponding to the opening of the first travel directional control valve, and the second travel motor can be supplied with a working fluid of a flow rate corresponding to the opening of the second travel directional control valve. Thus, the control device can adjust the distribution amount of the flow introduced into the travel system hydraulic circuit to each travel motor by the opening of each directional control valve. Therefore, each travel motor can be moved at a desired motion speed.

[0063] The hydraulic drive device of the sixth aspect is further provided with a plurality of loading and unloading side pressure sensors in the hydraulic drive device of the second aspect, and the hydraulic circuit of the loading and unloading system includes a plurality of loading and unloading directional control valves, which respectively correspond to a plurality of loading and unloading actuators including the loading and unloading actuators, and control the flow rate of the working fluid supplied to the corresponding loading and unloading actuators by changing the opening degree, and each of the loading and unloading side pressure sensors corresponds to each of the loading and unloading actuators, and detects the loading and unloading side supply pressure to the corresponding loading and unloading actuator, and the control device estimates the actual loading and unloading flow rate flowing in each of the loading and unloading actuators based on the discharge pressure and each loading and unloading side supply pressure, and further outputs an opening signal to the flow control valve according to each loading and unloading target flow rate and each loading and unloading actual flow rate flowing in each of the loading and unloading actuators.

[0064] According to the above aspect, the control device estimates each loading and unloading flow rate based on the discharge pressure and each loading and unloading side supply pressure, and further outputs an opening signal to the flow control valve according to each loading and unloading target flow rate and each loading and unloading flow rate. The control device can flow the working fluid of the driving side target flow rate into the driving system hydraulic circuit with higher accuracy, so it can also flow the working fluid of the loading and unloading target flow rate into each loading and unloading actuator with higher accuracy. As a result, each loading and unloading actuator can be moved at a desired speed.

Claims

1. A hydraulic drive device, characterized in that: This is a hydraulic drive device that supplies working fluid to the travel motor and loading and unloading actuator. It has: a hydraulic pump connected to the pump passage and discharging working fluid into the pump passage; a travel system hydraulic circuit connected to the first passage connected to the pump passage and controlling the flow of the working fluid to the travel motor; a loading and unloading system hydraulic circuit connected to a second passage connected to the pump passage and controlling the flow of working fluid to the loading and unloading actuator; a flow control valve disposed in the first passage and changing its opening according to an opening signal; and A control device controls the opening degree of the flow control valve by outputting an opening degree signal to the flow control valve.

2. The hydraulic drive device according to claim 1, characterized in that: The device further comprises: a discharge pressure sensor for detecting a discharge pressure of the hydraulic pump; and a travel side pressure sensor for detecting a travel side supply pressure as a hydraulic pressure of the working fluid flowing in the first passage; The control device estimates an actual flow rate of the traveling hydraulic circuit based on the discharge pressure and the traveling supply pressure, and outputs an opening signal corresponding to the traveling target flow rate and the actual flow rate of the traveling hydraulic circuit to the flow control valve.

3. The hydraulic drive device according to claim 2, characterized in that: The hydraulic circuit of the loading and unloading system controls the flow of the working fluid to the loading and unloading actuator by adjusting the opening between the hydraulic pump and the loading and unloading actuator; The travel system hydraulic circuit controls the flow of working fluid to the travel motor by adjusting the opening between the hydraulic pump and the travel motor; The control device closes the connection between the hydraulic pump and the loading and unloading actuator through the loading and unloading system hydraulic circuit, and opens the connection between the hydraulic pump and the traveling motor through the traveling system hydraulic circuit.

4. The hydraulic drive device according to claim 1, characterized in that: The control device controls the operation of the travel system hydraulic circuit based on a travel operation command and controls the operation of the loading and unloading system hydraulic circuit based on a loading and unloading operation command, and outputs an opening signal corresponding to the travel operation command and the loading and unloading operation command to the flow control valve.

5. The hydraulic drive device according to claim 1, characterized in that: The travel system hydraulic circuit includes: a first travel directional control valve connected to a first travel motor serving as the travel motor and the first passage; a second travel directional control valve connected to a second travel motor and the first passage; a first pressure compensation valve for maintaining a front-rear pressure difference of the first travel directional control valve; and a second pressure compensation valve for maintaining a front-rear pressure difference of the second travel directional control valve.

6. The hydraulic drive device according to claim 2, characterized in that: It also has multiple loading and unloading side pressure sensors; The loading and unloading system hydraulic circuit includes a plurality of loading and unloading directional control valves, which respectively correspond to a plurality of loading and unloading actuators including the loading and unloading actuator, and control the flow rate of the working fluid supplied to the corresponding loading and unloading actuator by changing the opening degree; Each of the loading and unloading side pressure sensors corresponds to each of the loading and unloading actuators, and detects a loading and unloading side supply pressure to the corresponding loading and unloading actuator; The control device estimates actual loading and unloading flow rates flowing in each loading and unloading actuator based on the discharge pressure and each loading and unloading side supply pressure, and further outputs an opening signal to the flow control valve according to each loading and unloading target flow rate and each loading and unloading actual flow rate flowing in each loading and unloading actuator.

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