KR20200135275A - Hydraulic circuit of the working vehicle - Google Patents

Abstract

The hydraulic circuit 100 includes a first actuator 11, a second actuator 12, a hydraulic pump 13, a first directional valve 15, a second directional valve 16, and a pilot pump 14. , A first operating device 17, a second operating device 18, an electronic pressure reducing valve 19 for controlling the primary pressure of the pilot hydraulic oil supplied to the second operating device 18, and an ECU 10. And, while the first operation device 17 is being operated, the ECU 10 sends a first command to the electronic pressure reducing valve 19 to reduce and maintain the primary pressure from the reference pressure to the first command pressure. When the second operation device 18 is operated from the state in which the first operation device 17 is operated, the first pressure is gradually increased from the first command pressure to the second command pressure with respect to the electronic pressure reducing valve 19. The second command is sent.

Description

Hydraulic circuit of the working vehicle

The present invention relates to a hydraulic circuit for a work vehicle.

In the following Patent Document 1, in a construction machine equipped with a hydraulic control circuit for driving a plurality of hydraulic actuators including a traveling actuator, when transitioning from a single motion of a traveling actuator to a combined motion of a traveling actuator and another actuator This is a technology that prevents a sudden decrease in travel speed due to a decrease in the flow rate of the hydraulic oil supplied from the hydraulic pump to the driving actuator.When the driving actuator is in operation and complex operation with other actuators is performed, flow rate control The opening speed of the spool when the pilot pressure acts on the pilot pressure receiving unit on the inlet side of the directional valve by compressing the pilot pressure oil return oil acting on the pilot pressure receiving unit on the return side of the directional valve A technology for preventing a sudden decrease in the flow rate of the hydraulic oil supplied to the traveling actuator by slowing down the pressure oil amount of the other actuator is disclosed.

In the following Patent Document 2, as a technique for preventing adverse effects such as deterioration of operability while securing a buffering action during sudden operation, the secondary pressure according to the amount of operation is used as the pilot pressure and supplied to the pilot line leading to the pilot port of the control valve. In a hydraulic circuit of a construction machine including a pressure reducing valve and a pilot oil pressure source as a primary pressure source of the pressure reducing valve, a bleed off line is formed on the primary side of the pressure reducing valve to communicate the first throttle and the pilot line to the tank. And, a technique of installing a second throttle on the bleed off line is disclosed.

Japanese Patent Laid-Open Publication No. 2005-121155 Japanese Unexamined Patent Publication No. 2006-125627

However, in Patent Document 1, since a flow control valve is provided in the return flow path of the pilot pressure oil acting on the pilot pressure receiving portion on the return side of the directional valve to compress the return oil, an actuator intended to control the flow rate during a combined operation. There is a problem in that it is necessary to install a flow control valve for each remote control valve that controls the control valve, thereby increasing the cost. In addition, in Patent Document 2, since the first throttle is disposed on the primary side of the pressure reducing valve for suppressing the absolute value of the pilot pressure, it is necessary to arrange a means for compressing the pilot pressure oil for each pressure receiving portion of the directional valve. However, since the bleed-off line with a second throttle for smoothing the rise of the pilot pressure is arranged on the secondary side of the pressure reducing valve, it is necessary to arrange the bleed-off line for each pressure receiving part of the directional valve. There is a problem that the cost rises.

Therefore, in view of the above problems, the present invention is a flow rate generated when transitioning from a single operation of driving one hydraulic actuator to a complex operation of driving a plurality of hydraulic actuators in a work vehicle equipped with a plurality of hydraulic actuators. It is an object of the present invention to provide a hydraulic circuit of a working vehicle capable of preventing a shock due to a sudden drop of the vehicle in an inexpensive configuration.

The hydraulic circuit of the work vehicle of the present invention switches the direction of the first actuator, the second actuator, the hydraulic pump supplying hydraulic oil to the first actuator and the second actuator, and the hydraulic oil supplied to the first actuator. A first directional valve for controlling the flow rate, a second directional valve for controlling the flow rate by switching the direction of the pressure oil supplied to the second actuator, and the first directional valve and the second directional valve A pilot pump for supplying pilot hydraulic oil, a first operation device capable of switching the direction and pressure of the pilot hydraulic oil supplied to the first directional valve according to the operation to adjust, and the pilot hydraulic oil supplied to the second directional valve A second operation device that can be adjusted by switching direction and pressure according to an operation, and is formed in a flow path between the second operation device and the pilot pump, and controls the primary pressure of the pilot hydraulic oil supplied to the second operation device. A pressure control device and a control command sending device for sending a control command to the pressure control device,

The control command transmission device transmits a first command to the pressure control device to reduce and maintain the primary pressure from a reference pressure to a first command pressure while the first operating device is being operated,

When the second operating device is operated from the state in which the first operating device is operated, a second command is sent to the pressure control device to increase the primary pressure from the first command pressure to a second command pressure. .

In the present invention, the control command transmission device, when the second operating device is not operated while the first operating device is operated, the first pressure is applied to the pressure control device to the second command pressure. It may be to transmit a command for decrementing by the first command pressure.

In the present invention, the first actuator may be a first hydraulic motor for travel, and the second actuator may be a hydraulic actuator for work.

In the present invention, the first circuit system comprising a first hydraulic pump for supplying hydraulic oil to the first hydraulic motor for travel and the first hydraulic motor for travel, the hydraulic actuator for work, and the second hydraulic motor for travel, And a second circuit system including a second hydraulic pump supplying hydraulic oil to the hydraulic actuator for work and the second traveling hydraulic motor, and a confluence of the hydraulic oil of the first circuit system and the hydraulic oil of the second circuit system. It may be provided with a switching valve.

According to the present invention, when shifting from a single operation of driving only the first actuator to a combined operation of simultaneously driving the first and second actuators, the pressure of the pilot hydraulic oil supplied to the second operation device corresponding to the second actuator Since the pressure is increased from the first command pressure to the second command pressure, it is possible to prevent shock due to a sudden decrease in the flow rate of the hydraulic oil supplied to the first actuator. Moreover, since the control of the present invention can be put into a plurality of actuators by simply providing a branch path leading to a plurality of operating devices on the downstream side of the pressure control device, a hydraulic circuit can be provided in an inexpensive configuration.

1 is a diagram showing a hydraulic circuit of a work vehicle according to a first embodiment.
Fig. 2 is a diagram showing a mode of controlling the primary pressure of pilot hydraulic oil supplied to a second remote control valve.
3 is a side view showing the work vehicle according to the second embodiment.
4 is a diagram showing a hydraulic circuit of the work vehicle according to the second embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First embodiment>

1 shows a hydraulic circuit 100 according to a first embodiment. The hydraulic circuit 100 includes a first actuator 11, a second actuator 12, a hydraulic pump 13, a pilot pump 14, a first directional valve 15, and a second direction. A switching valve 16, a first operating device 17, and a second operating device 18 are provided.

The first actuator 11 is a hydraulic motor driven by hydraulic oil supplied from the hydraulic pump 13. The second actuator 12 is a hydraulic cylinder driven by hydraulic oil supplied from the hydraulic pump 13. However, the first actuator 11 may be a hydraulic cylinder, and the second actuator 12 may be a hydraulic motor.

The hydraulic pump 13 is driven by an engine not shown, and discharges hydraulic oil. The hydraulic oil discharged from the hydraulic pump 13 is supplied to the first direction switching valve 15 and the second direction switching valve 16 through the flow path 13a and the flow path 13b. In addition, in FIG. 1, the flow path of the hydraulic oil supplied from the hydraulic pump 13 to the 1st actuator 11 and the 2nd actuator 12 is shown with a solid line.

The first directional valve 15 is a pilot type directional valve capable of adjusting the flow rate by switching the direction of the hydraulic oil supplied to the first actuator 11. The second directional valve 16 is a pilot type directional valve capable of adjusting the flow rate by switching the direction of the hydraulic oil supplied to the second actuator 12.

The pilot pump 14 discharges pilot pressure oil as a command input to the first direction switching valve 15 and the second direction switching valve 16. In addition, in FIG. 1, the flow path of the pilot pressure oil supplied from the pilot pump 14 to the first direction switching valve 15 and the second direction switching valve 16 is indicated by a broken line. The pilot pump 14 generates a pilot pressure applied to the first and second directional valves 15 and 16. The pilot pump 14 is driven by an engine not shown and discharges hydraulic oil to generate a pilot pressure in the flow path 14a. The flow path 14a branches into flow paths 14b, 14c, 14d, and 14e.

The first direction switching valve 15 can be switched to a plurality of positions by sliding the spool. When the pilot pressure is not applied to either of the pilot port 15a and the pilot port 15b of the first directional valve 15, the first directional valve 15 is in the neutral position due to the elastic force of the spring. maintain. When the first direction switching valve 15 is in the neutral position, the hydraulic oil is not supplied to the first actuator 11 from the flow path 13b.

On the other hand, when the pilot pressure is applied to the pilot port 15a or the pilot port 15b of the first directional valve 15, the first directional valve 15 is switched from the neutral position to another position, and the hydraulic oil is , It is supplied to the first actuator 11 through the flow path 11a or the flow path 11b. By the hydraulic oil supplied through the flow path 11a or the flow path 11b, the first actuator 11 is rotationally driven in the forward or reverse direction.

The second direction switching valve 16 can be switched to a plurality of positions by sliding the spool. When the pilot pressure is not applied to either of the pilot port 16a and the pilot port 16b of the second directional valve 16, the second directional valve 16 is in the neutral position due to the elastic force of the spring. maintain. When the second direction switching valve 16 is in the neutral position, the hydraulic oil is not supplied to the second actuator 12 from the flow path 13a.

On the other hand, when the pilot pressure is applied to the pilot port 16a or the pilot port 16b of the second directional valve 16, the second directional valve 16 is switched from the neutral position to another position, and the hydraulic oil is , It is supplied to the second actuator 12 through the flow path 12a or the flow path 12b. The second actuator 12 expands and contracts by the hydraulic oil supplied through the flow path 12a or the flow path 12b.

In the first direction switching valve 15, a first detection direction switching valve 15c is incorporated. The first detection direction switching valve 15c can be switched to a plurality of positions by sliding the spool. When the first direction switching valve 15 is held in the neutral position, the first detection direction switching valve 15c is also held in the neutral position. When the first direction switching valve 15 is switched from the neutral position to another position, the first detection direction switching valve 15c is also switched from the neutral position to another position in connection with this.

When the first detection direction switching valve 15c is in the neutral position, the first detection direction switching valve 15c does not close the flow path 14b. Therefore, the hydraulic oil can flow through the flow path 14b through the first detection direction switching valve 15c. On the other hand, when the first detection direction switching valve 15c is in a position other than the neutral position, the first detection direction switching valve 15c closes the flow path 14b.

The first pressure switch 141 is connected to the flow path 14b. The first operation device 17 is operated so that the first detection direction switching valve 15c is in a position other than the neutral position from the neutral position, thereby closing the flow path 14b, and pressure is applied to the downstream portion of the throttle of the flow path 14b. Generated, and this pressure is configured to be detected by the first pressure switch 141. The first pressure switch 141 detects that the first operation device 17 has been operated, and outputs this detection signal to the ECU 10 described later.

In the second direction switching valve 16, a second detection direction switching valve 16c is incorporated. The second detection direction switching valve 16c can be switched to a plurality of positions by sliding the spool. When the second direction switching valve 16 is held in the neutral position, the second detection direction switching valve 16c is also held in the neutral position. When the second direction selector valve 16 is switched from the neutral position to another position, the second detection direction selector valve 16c is also switched from the neutral position to another position in connection with this.

When the second detection direction switching valve 16c is in the neutral position, the second detection direction switching valve 16c does not close the flow path 14c. Therefore, the hydraulic oil can flow through the flow path 14c through the second detection direction switching valve 16c. On the other hand, when the second detection direction switching valve 16c is in a position other than the neutral position, the second detection direction switching valve 16c closes the flow path 14c.

The second pressure switch 142 is connected to the flow path 14c. The second operation device 18 is operated so that the second detection directional valve 16c is in a position other than the neutral position from the neutral position, thereby closing the flow path 14c, and pressure is applied to the throttle downstream of the flow path 14c. Generated, and this pressure is configured to be detected by the second pressure switch 142. The second pressure switch 142 detects that the second operation device 18 has been operated, and outputs this detection signal to the ECU 10 described later.

The first operation device 17 has a first remote control valve 170 for switching the direction and pressure of the pilot hydraulic oil supplied to the first direction switching valve 15. The first remote control valve 170 is connected to the flow path 14d. Moreover, the 1st remote control valve 170 is connected to the pilot port 15a and the pilot port 15b of the 1st direction switching valve 15 via the flow path 17a and the flow path 17b, respectively. The first remote control valve 170 supplies the hydraulic oil supplied from the pilot pump 14 via the flow path 14d to the first direction switching valve 15 as pilot hydraulic oil. By operating the first operation device 17, the first direction switching valve 15 is switched, the direction of the pressure oil supplied to the first actuator 11 can be switched to adjust the flow rate.

The second operation device 18 has a second remote control valve 180 for switching the direction and pressure of the pilot hydraulic oil supplied to the second directional valve 16. The second remote control valve 180 is connected to the flow path 14e. Moreover, the 2nd remote control valve 180 is connected to the pilot port 16a and the pilot port 16b of the 2nd direction switching valve 16 via the flow path 18a and the flow path 18b, respectively. The second remote control valve 180 supplies the hydraulic oil supplied from the pilot pump 14 via the flow path 14e to the second direction switching valve 16 as pilot hydraulic oil. By operating the second operation device 18, the second direction switching valve 16 is switched, the direction of the hydraulic oil supplied to the second actuator 12 can be switched, and the flow rate can be adjusted.

In the flow passage 14e between the second remote control valve 180 and the pilot pump 14, an electromagnetic pressure reducing valve 19 (an example of a pressure control device) is formed. The electronic pressure reducing valve 19 can control the primary pressure of the pilot hydraulic oil discharged from the pilot pump 14 and supplied to the second remote control valve 180. The electronic pressure reducing valve 19 can control the pressure according to the magnitude of the input current.

The hydraulic circuit 100 includes an ECU 10 (an example of a control command transmission device) that transmits a control command to the electronic pressure reducing valve 19. The ECU 10 transmits a control command according to the operation of the first operation device 17 and the second operation device 18. The ECU 10 determines that the first operation device 17 is being operated by receiving a detection signal from the first pressure switch 141, and receives the detection signal from the second pressure switch 142 to obtain a second It can be determined that the operating device 18 is being operated.

Next, the control of the electronic pressure reducing valve 19 by the ECU 10 will be described with reference to FIG. 2. FIG. 2 shows a mode of controlling the primary pressure of the pilot hydraulic oil supplied to the second remote control valve 180.

When the first operation device 17 is operated (time A in FIG. 2), the ECU 10 reduces the primary pressure of the pilot pressure oil from the reference pressure to the first command pressure with respect to the electronic pressure reducing valve 19, While the first operating device 17 is being operated (times A to B in Fig. 2), a first command is sent to the electronic pressure reducing valve 19 to maintain the primary pressure of the pilot pressure oil at the first command pressure. do. In addition, the reference pressure is the pressure of the hydraulic oil discharged from the pilot pump 14.

Subsequently, when the second operating device 18 is operated from the state in which the first operating device 17 has been operated (time B in FIG. 2), the ECU 10 receives 1 of the pilot pressure oil with respect to the electronic pressure reducing valve 19. A second command for increasing the differential pressure from the first command pressure to the second command pressure is issued. The second command pressure is higher than the first command pressure and lower than the reference pressure. The ratio of the reference pressure, the first command pressure, and the second command pressure is appropriately set. In addition, the time (times B to C in Fig. 2) to gradually increase from the first command pressure to the second command pressure is set appropriately.

Thereafter, while the first operating device 17 and the second operating device 18 are being operated (times C to D in FIG. 2 ), the primary pressure of the pilot pressure oil is applied to the electromagnetic pressure reducing valve 19. 2 Sends the command to be maintained at the command pressure. Thereby, when shifting from the single operation of driving only the first actuator 11 to the combined operation of simultaneously driving the first actuator 11 and the second actuator 12, the second remote control valve 180 is Since the pilot pressure applied to the directional control valve 16 is gradually increased from the first command pressure to the second command pressure, the hydraulic oil from the hydraulic pump 13 is not rapidly supplied to the second actuator 12. 1 It is possible to prevent a shock due to a sudden drop in the flow rate of the hydraulic oil supplied to the actuator 11.

Subsequently, the ECU 10 is piloted with respect to the electronic pressure reducing valve 19 when the second operating device 18 is not operated while the first operating device 17 is operated (time D in FIG. 2). A command is issued to decrease the primary pressure of the hydraulic oil from the second command pressure to the first command pressure. Thereafter, while only the first operating device 17 is being operated (times E to F in FIG. 2 ), a command for maintaining the primary pressure of the pilot pressure oil at the first command pressure is given to the electronic pressure reducing valve 19. Send.

In addition, when the first operation device 17 is not operated (time F in FIG. 2), the ECU 10 adjusts the primary pressure from the pilot pump 14 to the electronic pressure reducing valve 19 as a first command value. The command to increase and maintain the pressure to the standard value is transmitted from.

<2nd embodiment>

[Structure of work vehicle]

First, a schematic structure of a hydraulic excavator 1 as an example of a work vehicle is described with reference to FIG. 3. However, the work vehicle is not limited to the hydraulic excavator 1, and other vehicles such as a wheel loader may be used. The hydraulic excavator 1 includes a traveling device 2, a working device 3, and a turning device 4.

The traveling device 2 drives the hydraulic excavator 1 by receiving power from the engine 42. The traveling apparatus 2 includes a pair of left and right crawlers 21 and 21 and a pair of left and right traveling motors 22L and 22R. The left and right travel motors 22L and 22R, which are hydraulic motors, drive the left and right crawlers 21 and 21, respectively, thereby enabling the hydraulic excavator 1 to move forward and backward. Further, the traveling device 2 is provided with a blade cylinder 24 which is a hydraulic actuator for rotating the blade 23 and the blade 23 in the vertical direction.

The working device 3 is driven by receiving power from the engine 42 and performing excavation work such as soil and sand. The work apparatus 3 is provided with the boom 31, the arm 32, and the bucket 33, and makes excavation work possible by driving these independently. The boom 31, the arm 32, and the bucket 33 each correspond to a working part, and the hydraulic excavator 1 has a plurality of working parts.

The boom 31 is rotated by the boom cylinder 31a which is supported at one end by the whole of the turning device 4 and movable so as to expand and contract freely. Moreover, the arm 32 is rotated by the arm cylinder 32a which moves so that one end is supported by the other end of the boom 31, and freely expands and contracts. And the bucket 33 is rotated by the bucket cylinder 33a which moves so that one end part is supported by the other end of the arm 32, and freely expands and contracts. The boom cylinder 31a, the arm cylinder 32a, and the bucket cylinder 33a correspond to hydraulic actuators that drive the working part.

The turning device 4 turns the work device 3. In the turning device 4, a control unit 41, an engine 42, a turning table 43, a turning motor 44, and the like are disposed. The turning motor 44 which is a hydraulic motor drives the turning table 43 to turn the work device 3. In addition, a plurality of hydraulic pumps (not shown in FIG. 3) driven by the engine 42 are disposed in the turning device 4. These hydraulic pumps supply hydraulic oil to the boom cylinder 31a, the arm cylinder 32a, the bucket cylinder 33a, and the like.

The cockpit 411 is disposed in the control unit 41. A pair of work operation levers 412L and 412R are arranged on the left and right of the cockpit 411, and a pair of travel levers 413L and 413R are arranged in front. The operator seats in the cockpit 411 and operates the operation control levers 412L and 412R, travel levers 413L and 413R, and the like, thereby controlling the engine 42, each hydraulic motor, each hydraulic actuator, and the like, You can run, turn, and work.

[Composition of hydraulic circuit]

The hydraulic circuit 5 of the hydraulic excavator 1 will be described with reference to FIG. 4. The hydraulic circuit 5 includes first to third hydraulic actuators 121, 122, 123 (boom cylinder 31a, arm cylinder 32a, bucket cylinder 33a), left travel motor 22L, right travel The motor 22R, the swing motor 44, the first hydraulic pump 51, the second hydraulic pump 52, the directional valve 53, the pilot pump 54, and the remote control valve 55 Has. In addition, in FIG. 4, circuits related to the blade cylinder 24 and the like are omitted for convenience of explanation.

In the second embodiment, the first hydraulic pump 51 mainly supplies hydraulic oil to the right travel motor 22R, the third hydraulic actuator 123 and the turning motor 44. The second hydraulic pump 52 mainly supplies hydraulic oil to the first hydraulic actuator 121, the second hydraulic actuator 122, and the left travel motor 22L.

The directional valve 53 is formed corresponding to each hydraulic actuator, and is configured to be able to switch the direction and flow rate of the hydraulic oil supplied to the hydraulic actuator from the first hydraulic pump 51 and the second hydraulic pump 52 Has been. The plurality of directional valves 53 are collectively referred to as a control valve. Specifically, in the second embodiment, the first hydraulic actuator directional switching valve 53a corresponding to the first hydraulic actuator 121 and the second hydraulic actuator directional switching corresponding to the second hydraulic actuator 122 The valve 53b, the direction switching valve 53c for the left travel motor corresponding to the left travel motor 22L, the direction switching valve 53d for the right travel motor corresponding to the right travel motor 22R, and a third A third hydraulic actuator directional selector valve 53e corresponding to the hydraulic actuator 123 and a swing directional valve 5f corresponding to the swing motor 44 are provided. Since the structure of the directional valve 53 is the same as that of the first directional valve 15 and the second directional valve 16 of the first embodiment, detailed descriptions are omitted.

In the direction switching valve 53, a detection direction switching valve is incorporated. The detection direction switching valves respectively formed in the left travel motor direction switching valve 53c and the right travel motor direction switching valve 53d close or open the flow path 54a from the pilot pump 54. Further, detection formed in the first hydraulic actuator directional valve 53a, the second hydraulic actuator directional valve 53b, the third hydraulic actuator directional valve 53e, and the turning directional valve 5f The direction switching valve for use closes or opens the flow path 54b from the pilot pump 54. Since the structure of the detection direction switching valve is the same as that of the first detection direction control valve 15c and the second detection direction control valve 16c of the first embodiment, detailed descriptions are omitted.

The first pressure switch 141 is connected to the flow path 54a. The travel levers 413L and 413R are operated so that the detection directional valve of the left travel motor direction selector valve 53c or the right travel motor direction selector valve 53d becomes a position other than the neutral position from the neutral position, The flow path 54a is closed, and pressure is generated in the downstream portion of the throttle of the flow path 54a, and this pressure is detected by the first pressure switch 141. The first pressure switch 141 detects that the travel levers 413L and 413R have been operated, and outputs this detection signal to the ECU 10.

The second pressure switch 142 is connected to the flow path 54b. The operation operation lever 412R is operated so that the detection direction switching valve of the first hydraulic actuator direction switching valve 53a becomes a position other than the neutral position from the neutral position, so that the flow path 54b is closed and the flow path 54b A pressure is generated in the downstream portion of the throttle, and this pressure is detected by the second pressure switch 142. The second pressure switch 142 detects that the work operation lever 412R has been operated, and outputs this detection signal to the ECU 10.

The pilot pump 54 discharges pilot pressure oil as a command input to the directional valve 53 (53a, 53b, 53c, 53d, 53e, 53f). In addition, in FIG. 4, the flow path between the pilot pump 54 and the direction switching valve 53 is partially omitted.

The remote control valve 55 is configured to be capable of switching and adjusting the direction of the pilot pressure oil input to the directional valve 53 in accordance with the operation of the operation operation levers 412L and 412R and the travel levers 413L and 413R. The remote control valve 55 is formed for each hydraulic actuator and corresponding direction switching valve 53. For example, as shown in FIG. 4, the first hydraulic actuator remote control valve 55a corresponding to the work operation lever 412R for expanding and contracting the first hydraulic actuator 121 is formed, and the first hydraulic actuator The remote control valve 55a switches the direction of pilot pressure oil as a command to be supplied to the first hydraulic actuator direction switching valve 53a. Further, a left travel motor remote control valve 55b corresponding to a travel lever 413L for rotating the left travel motor 22L is formed, and the left travel motor remote control valve 55b is directed toward the left travel motor. The direction of the pilot pressure oil as a command to be supplied to the switching valve 53c is switched. Similarly, the remote control valve 55c for the right travel motor corresponding to the travel lever 413R for rotating the right travel motor 22R is formed, and the remote control valve 55c for the right travel motor is for the right travel motor. The direction of the pilot pressure oil as a command to be supplied to the direction switching valve 53d is switched. Although not shown in FIG. 4, the remote control valve 55 corresponding to the other direction switching valves 53b, 53e, 53f is formed.

An electromagnetic pressure reducing valve 19 is formed in a flow path between the first hydraulic actuator remote control valve 55a and the pilot pump 54. The electromagnetic pressure reducing valve 19 can control the primary pressure of the pilot hydraulic oil discharged from the pilot pump 14 and supplied to the first hydraulic actuator remote control valve 55a.

The hydraulic circuit 5 is provided with the ECU 10 which transmits a control command to the electromagnetic pressure reducing valve 19. The ECU 10 transmits a control command according to the operation of the work operation levers 412L and 412R and the travel levers 413L and 413R.

The hydraulic circuit 5 is provided with the confluence switching valve 56. The confluence switching valve 56 is a pilot type directional switching valve capable of merging the hydraulic oil discharged from the first hydraulic pump 51 and the second hydraulic pump 52. The confluence switching valve 56 can be switched to the position 56X or the position 56Y by sliding the spool. When pilot pressure is applied to the pilot port 56a and the pilot port 56b of the confluence switching valve 56, the confluence switching valve 56 is switched to the position 56Y. When the pilot pressure is not applied to the pilot port 56a or the pilot port 56b of the confluence switching valve 56, the confluence switching valve 56 is held at the position 56X by the elastic force of the spring. A flow path from the remote control valve 55c for the right travel motor is connected to the pilot port 56a, and a flow path from the remote control valve 55b for a left travel motor is connected to the pilot port 56b. Thereby, when the left and right travel levers 413L and 413R are operated simultaneously, that is, when a travel operation is performed, the merge switching valve 56 is switched to the position 56Y.

When the confluence switching valve 56 is in the position 56X, the hydraulic oil discharged from the first hydraulic pump 51 and the second hydraulic pump 52 divides and flows without being joined, and the first hydraulic pump 51 The hydraulic oil discharged from is supplied to the right travel motor direction switching valve 53d, the third hydraulic actuator direction switching valve 53e, and the turning direction switching valve 5f, and the second hydraulic pump 52 The hydraulic oil discharged from is supplied to the first hydraulic actuator direction switching valve 53a, the second hydraulic actuator direction switching valve 53b, and the left travel motor direction switching valve 53c.

When the confluence switching valve 56 is in the position 56Y, the hydraulic oil discharged from the first hydraulic pump 51 and the second hydraulic pump 52 merges.

When the travel levers 413L and 413R are operated, the ECU 10 reduces the primary pressure of the pilot pressure oil from the reference pressure to the first command pressure with respect to the electronic pressure reducing valve 19, and the travel levers 413L and 413R While is being operated, a first command is sent to the electromagnetic pressure reducing valve 19 to maintain the primary pressure of the pilot hydraulic oil at the first command pressure.

Subsequently, when the work operation lever 412R is operated from the state in which the travel levers 413L and 413R are operated, the ECU 10 adjusts the primary pressure of the pilot pressure oil to the electronic pressure reducing valve 19 from the first command pressure. Sends a second command that increases gradually with the second command pressure. Thereafter, while the travel levers 413L and 413R and the work operation lever 412R are being operated, a command for maintaining the primary pressure of the pilot pressure oil at the second command pressure is transmitted to the electromagnetic pressure reducing valve 19. In this way, when the first hydraulic actuator 121 is driven during travel, the pilot pressure applied to the first hydraulic actuator direction switching valve 53a is increased from the first command pressure to the second command pressure. There is no case where the hydraulic oil from the pump 51 and the second hydraulic pump 52 is rapidly supplied to the first hydraulic actuator 121, and thus travel due to a sudden decrease in the flow rate of the hydraulic oil supplied to the travel motors 22L and 22R. You can prevent a sudden drop in speed. Further, in the second embodiment, since the hydraulic oil discharged from the first hydraulic pump 51 and the second hydraulic pump 52 is joined by the confluence switching valve 56 during travel, the travel motors 22L and 22R It is possible to effectively prevent a rapid decrease in the flow rate of the supplied pressure oil.

Subsequently, when the operation control lever 412R is not operated while the travel levers 413L and 413R are operated, the ECU 10 adjusts the primary pressure of the pilot hydraulic oil to the electronic pressure reducing valve 19 to the second. Sends a command that decreases from the command pressure to the first command pressure. Thereafter, while only the travel levers 413L and 413R are being operated, a command for maintaining the primary pressure of the pilot pressure oil at the first command pressure is transmitted to the electromagnetic pressure reducing valve 19.

In addition, when the travel levers 413L and 413R are not operated, the ECU 10 increases and maintains the primary pressure from the pilot pump 54 with respect to the electronic pressure reducing valve 19 from the first command value to the reference value. Send a command.

In the second embodiment, since the control of the present invention can be applied to a plurality of actuators corresponding to a plurality of operation devices simply by providing a branch path leading to a plurality of operation devices on the downstream side of the electromagnetic pressure reducing valve 19. , A plurality of electromagnetic proportional valves for controlling the secondary pressure of the operating device are not required, and a hydraulic circuit can be provided in an inexpensive configuration.

As mentioned above, although the embodiment of this invention was demonstrated based on drawings, it should be considered that a specific structure is not limited to these embodiments. The scope of the present invention is indicated not only by the description of the above-described embodiments, but also by the claims, and includes the meanings equivalent to the claims and all changes within the scope.

100: hydraulic circuit
10: ECU
11: first actuator
12: second actuator
13: hydraulic pump
14: pilot pump
15: first directional valve
16: second directional valve
17: first operation device
18: second operation device
19: electronic pressure reducing valve
5: hydraulic circuit
51: first hydraulic pump
52: second hydraulic pump
53: directional valve
54: pilot pump
55: remote control valve
56: confluence switching valve

Claims (4)

A first actuator, a second actuator, a hydraulic pump that supplies hydraulic oil to the first actuator and the second actuator, and a first directional valve that adjusts the flow rate by changing the direction of the hydraulic oil supplied to the first actuator And, a second directional valve for adjusting a flow rate by changing a direction of the hydraulic oil supplied to the second actuator, a pilot pump for supplying pilot hydraulic oil to the first directional valve and the second directional valve, and the A first operation device capable of changing the direction and pressure of the pilot hydraulic oil supplied to the first directional valve according to the operation and adjusting the direction and pressure of the pilot hydraulic oil supplied to the second directional valve according to the operation A pressure control device that is formed in a flow path between the second operating device and the pilot pump and controls a primary pressure of the pilot hydraulic oil supplied to the second operating device, and the pressure control device A control command issuing device for sending a control command,
The control command transmission device transmits a first command to the pressure control device to reduce and maintain the primary pressure from a reference pressure to a first command pressure while the first operating device is being operated,
When the second operating device is operated from the state in which the first operating device is operated, sending a second command to the pressure control device to increase the primary pressure from the first command pressure to a second command pressure, Hydraulic circuit of the working vehicle. The method of claim 1,
When the second operating device is not operated while the first operating device is operated, the control command sending device applies the primary pressure to the pressure control device from the second command pressure to the first command. The hydraulic circuit of the work vehicle that sends a command to decrease by pressure. The method according to claim 1 or 2,
The first actuator is a first traveling hydraulic motor, and the second actuator is a working hydraulic actuator. The method of claim 3,
A first circuit system including a first hydraulic pump for supplying hydraulic oil to the first hydraulic motor for travel and the first hydraulic motor for travel,
A second circuit system comprising a hydraulic actuator for work, a hydraulic motor for travel, and a second hydraulic pump for supplying hydraulic oil to the hydraulic actuator for work and the hydraulic motor for travel,
A hydraulic circuit of a work vehicle, comprising: a confluence switching valve for joining the hydraulic oil of the first circuit system and the hydraulic oil of the second circuit system.

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