JP2020002990A - Hydraulic system of work machine - Google Patents

Abstract

To easily warm up oil passages by a braking operation valve and a shifting operation valve.SOLUTION: A hydraulic system of a work machine includes: a hydraulic pump P1; a brake mechanism 30 performing braking of a traveling device 36 and releasing of the braking on the basis of a pressure of a hydraulic fluid; a transmission mechanism for changing a speed of the traveling device on the basis of the pressure of the hydraulic fluid; a braking operation valve 80a controlling the hydraulic oil supplied to the brake mechanism; a shifting operation valve 81a controlling the hydraulic oil supplied to the transmission mechanism; a first oil passage 61 connecting the brake mechanism and the braking operation valve; a second oil passage 62 connecting the transmission mechanism and the shifting operation valve; a third oil passage 63 connecting the first oil passage and the second oil passage; a first discharge oil passage 66 communicated with the brake operation valve to discharge the hydraulic fluid passed through the braking operation valve; and a second discharge oil passage 67 communicated with the shifting operation valve to discharge the hydraulic fluid passed through the shifting operation valve. A braking set pressure of the hydraulic fluid set in the braking operation valve is higher than a shifting set pressure of the hydraulic fluid set in the shifting operation valve.SELECTED DRAWING: Figure 2A

Description

  The present invention relates to a hydraulic system for a working machine such as a skid steer loader, a compact truck loader, and a backhoe.

2. Description of the Related Art Conventionally, there is a technology disclosed in Patent Document 1 as a technique for warming up a working machine.
The work machine of Patent Document 1 includes a pilot pressure control valve that controls the pressure of pilot oil discharged from a pump and sent to a supply target, and a valve body in which the pilot pressure control valve is incorporated. In Patent Literature 1, a heat-up oil passage for allowing pilot oil discharged from a pump to flow into a valve body is provided, and the pilot oil flowing into the heat-up oil passage is caused to flow to a hydraulic oil tank via a relief valve or a throttle. This heats up the valve body.

Japanese Patent No. 5809544

In the working machine of Patent Literature 1, the valve body has to be machined for warming up, and a hydraulic oil passage connecting the relief valve or the throttle must be formed in the valve body.
SUMMARY OF THE INVENTION The present invention has been made to solve such a problem of the related art, and provides a working machine hydraulic system capable of easily warming up an oil passage by a brake operation valve and a shift operation valve. Aim.

The technical measures taken by the present invention to solve the technical problem are as follows.
The hydraulic system of the work machine includes a hydraulic pump that discharges hydraulic oil, a brake mechanism that brakes and releases the traveling device based on the pressure of the hydraulic oil, and a brake device that controls the traveling device based on the pressure of the hydraulic oil. A speed change mechanism for changing speed, a brake operation valve for controlling hydraulic oil supplied to the brake mechanism, a speed change operation valve for controlling hydraulic oil supplied to the speed change mechanism, the brake mechanism and the brake operation valve, A first oil path to be connected, a second oil path to connect the transmission mechanism and the shift operation valve, a third oil path to connect the first oil path to the second oil path, and the brake operation A first discharge oil passage communicating with a valve and discharging hydraulic oil passing through the brake operation valve; and a second discharge oil passage communicating with the shift operation valve and discharging hydraulic oil passing through the shift operation valve. And the brake actuation valve The brake set pressure of the hydraulic fluid constant to be higher than the speed set pressure of the hydraulic fluid to be set in the shift actuating valve.

The brake actuation valve sets the brake set pressure to a release pressure at which the brake mechanism releases the braking, the shift actuation valve sets the shift set pressure, and the speed change mechanism sets the speed of the traveling device. Set the deceleration pressure to decrease.
The brake operation valve is configured to switch between a first position in which the brake setting pressure is set to a braking pressure at which the brake mechanism performs the braking and a second position in which the brake setting pressure is set to the release pressure. It is a valve.

The shift operation valve switches between a first position in which the shift setting pressure is set to the deceleration pressure and a second position in which the shift mechanism sets the speed of the traveling device higher than a predetermined speed by the transmission mechanism. This is a possible gearshift switching valve.
The brake actuation valve is a brake proportional valve that can change the brake set pressure from a brake pressure at which the brake mechanism performs the braking to the release pressure.

The shift operation valve is a brake proportional valve that can change the shift setting pressure from an increased pressure at which the speed change mechanism makes the speed of the traveling device faster than a predetermined speed to the deceleration pressure.
The hydraulic system of the work machine includes a throttle provided in the third oil passage.
The hydraulic system of the working machine includes a first bypass oil passage connected to the third oil passage, and a hydraulic oil provided in the first bypass oil passage and allowing hydraulic oil from the second oil passage to the first oil passage. And a first check valve for restricting hydraulic oil from the first oil passage to the second oil passage.

  According to the present invention, the oil passage can be easily warmed up by the brake operation valve and the speed change operation valve.

It is a figure showing a hydraulic system (hydraulic oilway) of a work machine in a 1st embodiment. It is the elements on larger scale of the hydraulic system of the traveling system of a working machine. It is a figure which shows the 1st modification of FIG. 2A. It is a figure which shows the 2nd modification of FIG. 2B. It is a figure which shows the 3rd modification of FIG. 2A. It is a side view which shows the track loader which is an example of a working machine.

Hereinafter, an embodiment of the hydraulic system of the work machine 1 according to the present invention will be described with reference to the drawings as appropriate.
FIG. 3 shows a side view of the working machine 1 according to the present invention. FIG. 3 shows a compact truck loader as an example of the work machine 1. However, the working machine 1 according to the present invention is not limited to a compact truck loader, and may be another type of loader working machine such as a skid steer loader. Further, the work machine 1 other than the loader work machine may be used.

As shown in FIG. 3, the working machine 1 includes a body 2, a cabin 3, a working device 4, and a traveling device 5.
In the embodiment of the present invention, the front side (left side in FIG. 3) of the driver sitting on the driver's seat 8 of the work machine 1 is forward, the rear side (right side in FIG. 3) of the driver is rearward, and the left side of the driver (FIG. 3). 3 is described as left and the right side of the driver (rear side in FIG. 3) as right. In addition, a horizontal direction that is a direction orthogonal to the front and rear directions will be described as a body width direction. The direction from the center of the body 2 to the right or left will be described as the outside of the body. In other words, the outside of the body is the direction of the body width and the direction away from the body 2. The direction opposite to the outside of the aircraft will be described as the interior of the aircraft. In other words, the inside of the airframe is the width direction of the airframe and the direction approaching the airframe 2.

The cabin 3 is mounted on the body 2. The cabin 3 is provided with a driver's seat 8. The working device 4 is mounted on the machine body 2. The traveling device 5 is provided outside the body 2. A prime mover 32 is mounted at the rear of the body.
The working device 4 includes a boom 10, a work implement 11, a lift link 12, a control link 13, a boom cylinder 14, and a bucket cylinder 15.

  The boom 10 is provided on the right and left sides of the cabin 3 so as to be vertically swingable. The work implement 11 is, for example, a bucket, and the bucket 11 is provided at the front end (front end) of the boom 10 so as to be vertically swingable. The lift link 12 and the control link 13 support a base (rear part) of the boom 10 so that the boom 10 can swing up and down. The boom cylinder 14 moves the boom 10 up and down by expanding and contracting. The bucket cylinder 15 swings the bucket 11 by expanding and contracting.

The lift link 12, the control link 13, and the boom cylinder 14 are provided on the left and right sides of the body 2 corresponding to the left and right booms 10, respectively.
The lift link 12 is provided at the rear of the base of each boom 10 in a vertical direction. The upper part (one end side) of the lift link 12 is rotatably supported around a horizontal axis via a pivot 16 (first pivot) near a rear portion of the base of each boom 10. Further, a lower portion (the other end side) of the lift link 12 is rotatably supported around a horizontal axis via a pivot 17 (second pivot) near a rear portion of the body 2. The second pivot 17 is provided below the first pivot 16.

  The upper part of the boom cylinder 14 is rotatably supported about a horizontal axis via a pivot 18 (third pivot). The third pivot 18 is provided at the base of each boom 10 and at the front of the base. The lower part of the boom cylinder 14 is rotatably supported around a horizontal axis via a pivot 19 (a fourth pivot). The fourth pivot 19 is provided near the lower rear of the body 2 and below the third pivot 18.

  The control link 13 is provided in front of the lift link 12. One end of the control link 13 is rotatably supported around a horizontal axis via a pivot 20 (fifth pivot). The fifth pivot 20 is the body 2 and is provided at a position corresponding to the front of the lift link 12. The other end of the control link 13 is rotatably supported around a horizontal axis via a pivot 21 (sixth pivot). The sixth pivot 21 is the boom 10 and is provided in front of the second pivot 17 and above the second pivot 17.

  By expanding and contracting the boom cylinder 14, each boom 10 swings up and down around the first pivot shaft 16 while the base of each boom 10 is supported by the lift link 12 and the control link 13. Goes up and down. The control link 13 swings up and down around the fifth pivot 20 as each boom 10 swings up and down. The lift link 12 swings back and forth around the second pivot 17 with the vertical swing of the control link 13.

At the front of the boom 10, another work tool 11 can be mounted instead of the bucket 11. As another working tool 11, there is an attachment (preliminary attachment) such as a hydraulic crusher, a hydraulic breaker, an angle bloom, an earth auger, a pallet fork, a sweeper, a mower, and a snow blower.
A connection member 50 is provided at a front portion of the left boom 10. The connection member 50 is a device that connects a hydraulic device mounted on the preliminary attachment and a first pipe material such as a pipe provided on the boom 10. Specifically, a first pipe member can be connected to one end of the connection member 50, and a second pipe member connected to a hydraulic device of the preliminary attachment can be connected to the other end. Thereby, the hydraulic oil flowing through the first pipe material is supplied to the hydraulic equipment through the second pipe material.

The bucket cylinders 15 are respectively arranged near the front portions of the respective booms 10. The bucket 11 is swung by expanding and contracting the bucket cylinder 15.
In the present embodiment, the traveling devices 5 of the crawler type (including the semi-crawler type) are employed as the traveling devices 5 on the left and right sides. Note that a wheel-type traveling device 5 having a front wheel and a rear wheel may be employed.

Next, a hydraulic system of the work machine 1 according to the present invention will be described. The hydraulic system of the working machine 1 has a traveling hydraulic system and a working hydraulic system.
As shown in FIG. 1, the traveling-system hydraulic system is a traveling-system hydraulic system that drives the traveling device 5, and includes a motor 32, a first hydraulic pump (hydraulic pump) P <b> 1, and a first traveling system. A motor mechanism 31L, a second traveling motor mechanism 31R, and a traveling drive circuit 34 are provided.

  The prime mover 32 includes an electric motor, an engine, and the like. In this embodiment, the prime mover 32 is an engine. The first hydraulic pump P1 is a pump driven by the power of the prime mover 32, and is configured by a constant displacement gear pump. The first hydraulic pump P1 is capable of discharging the hydraulic oil stored in a tank (hydraulic oil tank) 22. On the discharge side of the first hydraulic pump P1, a discharge oil passage 40 through which hydraulic oil flows is provided. A filter 35 is provided in the middle of the discharge oil passage 40. The discharge side of the hydraulic oil in the discharge oil passage 40 is branched into a plurality. A first charge oil passage 41 is connected to the discharge side of the discharge oil passage 40. The first charge oil passage 41 reaches the traveling drive mechanism 34. Of the hydraulic oil discharged from the first hydraulic pump P1, the hydraulic oil used for control may be called pilot oil, and the pressure of the pilot oil may be called pilot pressure.

The travel drive mechanism 34 is a mechanism that drives the first travel motor mechanism 31L and the second travel motor mechanism 31R, and includes a drive circuit (left drive circuit) 34L for driving the first travel motor mechanism 31L and a second travel motor. And a drive circuit (right drive circuit) 34R for driving the motor mechanism 31R.
The drive circuits 34L and 34R have HST pumps (traveling pumps) 52L and 52R, shift oil passages 57h and 57i, and a second charge oil passage 42, respectively. The shift oil passages 57h and 57i are oil passages that connect the HST pumps 52L and 52R and the HST motor 36. The second charge oil passage 42 is connected to the shift oil passages 57h and 57i, and is an oil passage for replenishing the hydraulic oil from the first hydraulic pump P1 to the shift oil passages 57h and 57i. The HST pumps 52L and 52R are swash plate type variable displacement axial pumps driven by the power of the prime mover 32. The HST pumps 52L and 52R have a forward pressure receiving portion 52a and a reverse pressure receiving portion 52b on which pilot pressure acts, and the angle of the swash plate is changed by the pilot pressure acting on the pressure receiving portions 52a and 52b. The output of the HST pumps 52L and 52R (discharge amount of hydraulic oil) and the discharge direction of hydraulic oil can be changed by changing the angle of the swash plate. In other words, the HST pumps 52L and 52R change the driving force output to the traveling device 5 by changing the angle of the swash plate.

The first traveling motor mechanism 31L is a mechanism that transmits power to a drive shaft of the traveling device 5 provided on the left side of the body 2. The second traveling motor mechanism 31R is a mechanism that transmits power to a drive shaft of the traveling device 5 provided on the right side of the body 2. The first travel motor mechanism 31L has an HST motor (travel motor) 36 and a speed change mechanism.
The HST motor 36 is a swash plate type variable displacement axial motor that can change the vehicle speed (rotation) to first speed or second speed. In other words, the HST motor 36 is a motor that can change the propulsion force of the work implement 1.

  The transmission mechanism includes a swash plate switching cylinder 38a and a travel switching valve 38b. The swash plate switching cylinder 38a is a cylinder that changes the angle of the swash plate of the HST motor 36 by expansion and contraction. The traveling switching valve 38b is a valve that expands and contracts the swash plate switching cylinder 38a to one side or the other side, and is a two-position switching valve that switches between a first position 39a and a second position 39b. The switching of the travel switching valve 38b is performed by the shift switching valve 81a. The speed changeover switching valve 81a is connected to the discharge oil passage 40 and is connected to the traveling switching valve 38b of the first traveling motor mechanism 31L and the traveling switching valve 38b of the second traveling motor mechanism 31R. The speed change switching valve 81a is a two-position switching valve that can switch between a first position 81a1 and a second position 81a2. When the shift changeover valve 81a is set to the first position 81a1, the pressure of the hydraulic oil applied to the traveling changeover valve 38b of the transmission mechanism is set to a pressure (deceleration pressure) corresponding to a predetermined speed (for example, first speed). Further, when the shift switching valve 81a is set to the second position 81a2, the pressure of the hydraulic oil applied to the travel switching valve 38b is increased to a pressure (increased pressure) corresponding to the speed (second speed) faster than a predetermined speed (first speed). Set to. Therefore, when the speed changeover switching valve 81a is at the first position 81a1, the travel switching valve 38b is at the first position 39a, and accordingly, the swash plate switching cylinder 38a is contracted, and the HST motor 36 is set to the first speed. it can. When the shift switching valve 81a is at the second position 81a2, the traveling switching valve 38b is at the second position 39b, and accordingly, the swash plate switching cylinder 38a is extended, and the HST motor 36 is set to the second speed. it can. The HST motor 36 shifts to the first or second speed under the control of the control device 90. For example, the control device 90 is provided with an operation member 58 such as a switch (speed change switch). When the operation member 58 is switched to the first speed, the control device 90 outputs a control signal for demagnetizing the solenoid of the shift switching valve 81a to set the shift switching valve 81a to the first position 81a1. When the operating member 58 is switched to the second speed, the control device 90 outputs a control signal for exciting the solenoid of the shift switching valve 81a to set the shift switching valve 81a to the second position 81a2.

  The first traveling motor mechanism 31L has a brake mechanism 30. The brake mechanism 30 can stop the braking of the right traveling device 5, that is, the rotation of the HST motor 36 or the rotation of the output shaft that rotates with the rotation of the HST motor 36. The brake mechanism 30 changes to an operation state of braking the traveling motor mechanism 31 or an operation state of releasing the braking by the pilot oil (hydraulic oil) discharged from the first hydraulic pump P1. For example, the brake mechanism 30 includes a first disk provided on an output shaft of the traveling motor mechanism 31, a movable second disk, and a spring that biases the second disk toward a side where the second disk contacts the first disk. ing. Further, the brake mechanism 30 includes a housing portion (housing case) 59 for housing the first disk, the second disk, and the spring. The portion of the housing portion 59 in which the second disk is stored and the brake switching valve 80a are connected via an oil passage as described later. The brake switching valve 80a is an electromagnetic valve that performs braking and release of braking (braking release) in the brake mechanism 30, and is a two-position switching valve that can be switched between a first position 80a1 and a second position 80a2. When in the first position 80a1, the brake switching valve 80a sets the pressure of the hydraulic oil applied to the brake mechanism 30 (the pressure applied to the housing portion 59) to the pressure (braking pressure) at which the brake mechanism 30 performs braking. When the brake switching valve 80a is at the second position 80a2, the pressure of the hydraulic oil is set to be equal to or higher than the pressure at which braking is released (release pressure). The switching of the brake switching valve 80a is performed under the control of the control device 90. For example, the control device 90 outputs a control signal for demagnetizing the solenoid of the brake switching valve 80a to set the brake switching valve 80a to the first position 80a1. Further, the control device 90 outputs a control signal for exciting the solenoid of the brake switching valve 80a to set the brake switching valve 80a to the second position 80a2. Further, the output of the control signal from the control device 90 to the brake switching valve 80a may be performed, for example, by providing a switch and manually operating the switch. The judgment may be performed automatically.

  Therefore, when the brake control switching valve 80a is at the first position 80a1, the pilot oil in the storage section of the storage section 59 is discharged, the second disk moves in the direction of braking, and the brake mechanism 30 can perform braking. When the brake control switching valve 80a is at the second position 80a2, the pilot oil is supplied to the storage portion of the storage portion 59, and the second disk is turned on the opposite side to braking (opposite to the biasing direction of the spring). Movement and braking release in the brake mechanism 30 can be performed. The second traveling motor mechanism 31R has the same configuration as the first traveling motor mechanism 31L, and the configuration shown by the first traveling motor mechanism 31L may be replaced with the second traveling motor mechanism 31R. Is omitted.

As shown in FIG. 1, the work machine 1 includes an operation device 53. The operating device 53 is a device that operates the traveling device 5, that is, the first traveling motor mechanism 31L, the second traveling motor mechanism 31R, and the traveling drive circuit 34. The operating device 53 has a first operating member 54 and a plurality of operating valves 55 (55a, 55b, 55c, 55d).
The first operation member 54 is an operation member that is supported by the operation valve 55 and swings in the left-right direction (machine body width direction) or the front-back direction. The plurality of operation valves 55 are operated in common, that is, by one first operation member 54. The plurality of operation valves 55 operate based on the swing of the first operation member 54. Hydraulic oil (pilot oil) from the first hydraulic pump P1 can be supplied to the plurality of operation valves 55 via the discharge oil passage 40. The plurality of operation valves 55 are an operation valve 55a, an operation valve 55b, an operation valve 55c, and an operation valve 55d.

  The plurality of operation valves 55 and the travel drive mechanism 34 (travel pumps 52L and 52R) of the travel system are connected by a travel oil path 45. The traveling oil passage 45 has a first traveling oil passage 45a, a second traveling oil passage 45b, a third traveling oil passage 45c, a fourth traveling oil passage 45d, and a fifth traveling oil passage 45e. The first traveling oil passage 45a is an oil passage connected to the forward pressure receiving portion 52a of the traveling pump 52L. The second traveling oil passage 45b is an oil passage connected to the reverse pressure receiving portion 52b of the traveling pump 52L. The third traveling oil passage 45c is an oil passage connected to the forward pressure receiving portion 52a of the traveling pump 52R. The fourth traveling oil passage 45d is an oil passage connected to the reverse pressure receiving portion 52b of the traveling pump 52R. The fifth traveling oil passage 45e is an oil passage that connects the operation valve 55, the first traveling oil passage 45a, the second traveling oil passage 45b, the third traveling oil passage 45c, and the fourth traveling oil passage 45d. The fifth traveling oil passage 45e connects the plurality of shuttle valves 46 and the plurality of operation valves 55 (55a, 55b, 55c, 55d).

  When the first operating member 54 is swung forward (in the direction indicated by the arrow A1 in FIG. 1), the operating valve 55a is operated to output a pilot pressure from the operating valve 55a, and the output shaft of the traveling motor 36 is operated by the first operating member. The work implement 1 rotates forward (forward rotation) at a speed proportional to the swing amount of the member 54, and the work machine 1 moves straight forward. When the first operation member 54 is swung rearward (in the direction indicated by the arrow A2 in FIG. 1), the operation valve 55b is operated to output a pilot pressure from the operation valve 55b, and the output shaft of the traveling motor 36 is moved to the second position. The reverse rotation (reverse rotation) at a speed proportional to the swing amount of the one operation member 54 causes the work machine 1 to move straight back.

  When the first operation member 54 is swung to the right (in the direction indicated by the arrow A3 in FIG. 1), the operation valve 55c is operated, and the pilot pressure is output from the operation valve 55c. The shaft rotates forward and the output shaft of the traveling motor 36 on the right rotates in reverse, and the work machine 1 turns to the right. When the first operating member 54 is swung to the left (in the direction indicated by the arrow A4 in FIG. 1), the operating valve 55d is operated, the pilot pressure is output from the operating valve 55d, and the output shaft of the left traveling motor 36 is driven. The work machine 1 rotates in the reverse direction and the output shaft of the traveling motor 36 on the right rotates forward, and the work machine 1 turns to the left.

When the first operating member 54 is swung in an oblique direction, the output pressure of the left traveling motor 36 and the output shaft of the right traveling motor 36 is increased by the differential pressure between the pilot pressure acting on the pressure receiving portion 52a and the pressure receiving portion 52b. The rotation direction and the rotation speed are determined, and the work machine 1 turns right or left while moving forward or backward.
By the way, the hydraulic system of the work machine 1 connects the first hydraulic path connected to the first hydraulic apparatus and the second hydraulic path connected to the second hydraulic apparatus by the third hydraulic path, and supplies the first hydraulic path to the first hydraulic apparatus. By connecting the first discharge oil passage to a first working valve that controls the working oil to be operated, and by connecting the second discharge oil passage to a second working valve that controls the working oil supplied to the second hydraulic device, It is easy to warm up. In this embodiment, the first hydraulic device is the brake mechanism 30, and the second hydraulic device is a transmission mechanism. Further, the first operating valve is a brake switching valve 80a which is one of the brake operating valves for controlling the operating oil supplied to the brake mechanism 30, and the second operating valve is a shifting operation for controlling the operating oil supplied to the transmission mechanism. This is a shift switching valve 81a that is a valve.

Hereinafter, the first oil passage, the second oil passage, and the third oil passage will be described.
As shown in FIGS. 1 and 2A, the first oil passage 61 is provided with a first hydraulic device (the brake mechanism 30) and a first hydraulic valve (a hydraulic valve) that controls hydraulic oil supplied to the first hydraulic device (the brake mechanism 30). Brake switching valve) 80a. In this embodiment, the first oil passage 61 includes a first brake oil passage 61a and a second brake oil passage 61b. The first brake oil passage 61a is an oil passage that connects the brake mechanism 30 of the first traveling motor mechanism 31L and the brake switching valve (first operating valve) 80a. The second brake oil passage 61b is an oil passage that connects the brake mechanism 30 of the second traveling motor mechanism 31R and the brake switching valve (first operating valve) 80a. The first brake oil passage 61a and the second brake oil passage 61b join on the way, and the joined oil passage (the dual use oil passage for the first brake oil passage 61a and the second brake oil passage 61b) is braked. It is connected to the switching valve 80a. A throttle portion 74 for reducing the flow rate of the hydraulic oil is provided in the dual-purpose oil passage 61c. In other words, in the first oil passage 61, the constricted portion 74 is formed by a connection portion (a junction 64 described later) where the third oil passage 63 connects to the first oil passage 61 and a connection portion connected to the brake switching valve 80 a. It is provided in the section.

A first discharge oil passage 66 is connected to a discharge port of the brake switching valve 80a. The first discharge oil passage 66 can discharge the hydraulic oil that has passed through the brake switching valve 80a, that is, the hydraulic oil of the first oil passage 61 (the first brake oil passage 61a and the second brake oil passage 61b). The first discharge oil passage 66 is connected to a suction portion of the hydraulic pump, the hydraulic oil tank 22, and the like.
The second oil passage 62 is an oil passage that connects a second hydraulic device (transmission mechanism) and a second operating valve (transmission switching valve) 81a that controls hydraulic oil supplied to the second hydraulic device (transmission mechanism). is there. In this embodiment, the second oil passage 62 includes a first transmission oil passage 62a and a second transmission oil passage 62b. The first transmission oil passage 62a is an oil passage that connects the traveling switching valve 38b of the transmission mechanism in the first traveling motor mechanism 31L and the transmission switching valve (second operating valve) 81a. The second transmission oil passage 62b is an oil passage that connects the traveling switching valve 38b of the transmission mechanism in the second traveling motor mechanism 31R and the transmission switching valve (second operating valve) 81a.

  The first transmission oil passage 62a and the second transmission oil passage 62b join on the way, and the joined oil passage is connected to the shift switching valve 81a. A second discharge oil passage 67 is connected to a discharge port of the shift switching valve 81a. The second discharge oil passage 67 can discharge the hydraulic oil that has passed through the shift switching valve 81a, that is, the hydraulic oil of the second oil passage 62 (the first shift oil passage 62a and the second shift oil passage 62b). The second discharge oil passage 67 is connected to a suction portion of the hydraulic pump, the hydraulic oil tank 22, and the like.

The third oil passage 63 is an oil passage that connects the first oil passage 61 and the second oil passage 62. The third oil passage 63 includes a junction 64 where the first brake oil passage 61a and the second brake oil passage 61b join, and a junction 65 where the first transmission oil passage 62a and the second transmission oil passage 62b join. Are connected. The third oil passage 63 is provided with a throttle portion 73 for reducing the flow rate of the working oil.
The control device 90 includes a brake set pressure (first set pressure) PV1 set by the brake switching valve (first operating valve) 80a and a shift set pressure (second set pressure) set by the second operating valve (shift switching valve) 81a. 2 Set pressure) Set the differential pressure with PV2. The brake set pressure PV1 is, for example, the pressure at the output port 100 of the brake switching valve 80a. In other words, the first set pressure PV1 is a pressure that acts on the first oil passage 61 (the first brake oil passage 61a and the second brake oil passage 61b).

The second set pressure (shift setting pressure) PV2 is, for example, the pressure at the output port 101 of the shift switching valve 81a. In other words, the second set pressure PV2 is a pressure that acts on the second oil passage 62 (the first transmission oil passage 62a and the second transmission oil passage 62b).
The control device 90 controls the brake switching valve 80a and the shift switching valve 81a such that a differential pressure between the first set pressure PV1 and the second set pressure PV2 is generated. The control device 90 sets the brake set pressure PV1 of the brake switch valve 80a higher than the shift set pressure PV2 of the shift switch valve 81a, for example, in a warm-up mode for performing warm-up. Specifically, in the warm-up mode, the control device 90 sets the brake set pressure PV1 to be equal to or higher than the release pressure at which the brake mechanism 30 releases the brake by setting the brake switching valve 80a to the second position 80a2. Further, in the warm-up mode, the control device 90 sets the shift setting pressure PV2 to a deceleration pressure at which the shift mechanism decelerates by setting the shift switching valve 81a to the first position 81a1. That is, when the brake switching valve 80a is in the braking release state and the transmission mechanism is in the deceleration state, the brake setting pressure PV1> the transmission setting pressure PV2, and the brake setting pressure PV1 of the working oil set by the brake switching valve 80a. Is higher than the shift setting pressure PV2 of the hydraulic oil set by the shift switching valve 81a.

  As shown by the arrow A10 in FIG. 2A, when the brake set pressure PV1> the shift set pressure PV2, the hydraulic oil that has passed through the brake switching valve 80a passes through the first oil passage 61 and the third oil passage 63, and passes through the second oil passage 63. The oil flows into the oil passage 62 and is discharged from the discharge port of the shift switching valve 81a to the second discharge oil passage 67. This makes it possible to warm up the first oil passage (brake oil passage) and the second oil passage (speed-change oil passage). In the warm-up mode, for example, a mode switch 95 that can be switched ON / OFF is connected to the control device 90. When the mode switch 95 is ON, the warm-up mode is set and the mode switch 95 is turned OFF. If, the warm-up mode is canceled. When the mode switch 95 is OFF, the shift can be performed by operating the operation member 58, and the braking and the release of the braking can be performed automatically or manually.

  In the above-described embodiment, the brake setting pressure PV1 of the brake switching valve 80a is set higher than the shift setting pressure PV2 of the shift switching valve 81a. However, instead of this, the shift setting pressure PV2 of the shift switching valve 81a is increased. It may be higher than the brake set pressure PV1 of the brake switching valve 80a. Specifically, in the warm-up mode, the control device 90 sets the brake set pressure PV1 to the braking pressure at which the brake mechanism 30 performs braking by setting the brake switching valve 80a to the first position 80a1. Further, in the warm-up mode, the control device 90 sets the shift setting pressure PV2 to the speed increasing pressure at which the speed change mechanism increases the speed by setting the shift switching valve 81a to the second position 81a2. That is, when the brake switching valve 80a is in the braking state and the speed change mechanism is in the speed increasing state, the brake setting pressure PV1 <the shift setting pressure PV2, and the shift setting pressure PV2 of the working oil set by the shift switching valve 81a. Becomes higher than the brake set pressure PV1 of the hydraulic oil set by the brake switching valve 80a.

  As shown by the arrow A11 in FIG. 2A, when the brake set pressure PV1 <the shift set pressure PV2, the hydraulic oil that has passed through the shift switching valve 81a passes through the second oil passage 62 and the third oil passage 63, and then passes through the first oil passage 63. The oil flows into the oil passage 61 and is discharged from the discharge port of the brake switching valve 80a to the first discharge oil passage 66. This makes it possible to warm up the first oil passage (brake oil passage) and the second oil passage (speed-change oil passage).

  FIG. 2B is a diagram showing a first modification of FIG. 2A. 2B shows the oil passages (the first brake oil passage 61a and the first transmission oil passage 62a) on the first traveling motor mechanism 31L side for convenience of explanation, but the oil on the second traveling motor mechanism 31R side. The roads (the second brake oil passage 61b and the second transmission oil passage 62b) are omitted, and the present invention is also applicable to the oil passage on the second traveling motor mechanism 31R side.

As shown in FIG. 2B, the first modified example is an example in which the shift operation valve (second operation valve) is changed to a shift proportional valve 81b configured by an electromagnetic proportional valve.
The speed change proportional valve 81b has a primary port (pump port) 81b1 and a secondary port 81b2. The primary port 81b1 of the shift proportional valve 81b is connected to the discharge oil passage 40. The secondary port 81b2 of the shift proportional valve 81b is connected to the second oil passage 62 (the first shift oil passage 62a and the second shift oil passage 62b). The discharge port 81b3 of the shift proportional valve 81b is connected to the hydraulic oil tank 22 via the second discharge oil passage 67. In the shift proportional valve 81b, the second set pressure PV2 is the pressure of the secondary port 81b2.

  In the first modification, the control device 90 sets the brake switching valve 80a to the second position 80a2 and sets the opening of the speed change proportional valve 81b to a minimum, for example, the opening corresponding to the first speed, in the warm-up mode. Set every time. That is, in the warm-up mode, the controller 90 sets the brake set pressure PV1 of the brake switching valve 80a to the release pressure or more and sets the shift set pressure PV2 of the shift proportional valve 81b to a deceleration pressure at which the speed change mechanism decelerates.

  Therefore, even when the shift switching valve 81a is changed to the shift proportional valve 81b, it is possible to set the brake setting pressure PV1> the shift setting pressure PV2 by setting the opening of the shift proportional valve 81b. Also in this case, the hydraulic oil that has passed through the brake switching valve 80a flows through the first oil passage 61 and the third oil passage 63 to the second oil passage 62, and from the discharge port 81b3 of the speed change proportional valve 81b to the second oil discharge. It can be discharged to the road 67.

  In the first modified example, when the control device 90 is in the warm-up mode, the control device 90 sets the brake switching valve 80a to the first position 80a1 and sets the shift proportional valve 81b to the maximum, for example, the opening corresponding to the second speed. May be set. That is, in the warm-up mode, the control device 90 sets the brake set pressure PV1 of the brake switching valve 80a to the braking pressure, and sets the shift set pressure PV2 of the shift proportional valve 81b to the speed increasing pressure at which the speed change mechanism increases the speed. According to this, by setting the opening of the shift proportional valve 81b, it is possible to set the brake set pressure PV1 <the shift set pressure PV2. In this case, the hydraulic oil that has passed through the shift proportional valve 81b flows through the second oil passage 62 and the third oil passage 63 to the first oil passage 61, and from the discharge port of the brake switching valve 80a to the first discharge oil passage 66. Can be discharged.

  In the first modified example, in the warm-up mode, the shift setting pressure PV2 is determined by setting the opening of the shift proportional valve 81b to the maximum and the minimum. It may be changed arbitrarily. For example, in the warm-up mode, the magnitude of the differential pressure between the brake set pressure PV1 and the shift set pressure PV2 can be changed by arbitrarily changing the opening of the shift proportional valve 81b.

  The control device 90 is connected to a temperature detection device 91 for detecting the temperature of the hydraulic oil, and the differential pressure (the brake setting pressure PV1 and the shift setting pressure PV2 is changed according to the temperature detected by the temperature detection device 91). May be set. Control device 90 increases the differential pressure when the detected temperature detected by temperature detecting device 91 is lower than a predetermined set temperature. Specifically, the control device 90 increases the opening of the shift proportional valve 81b when the detected temperature is below the freezing point and the viscosity of the hydraulic oil is high, and when the detected temperature is not below the freezing point, the control device 90 controls the shift proportional valve 81b. Reduce the opening.

  As shown in FIG. 2B, a first bypass oil passage 68 may be connected to the third oil passage 63. The first bypass oil passage 68 is provided with a first check valve 71. The first check valve 71 allows hydraulic oil from the second oil passage 62 to the first oil passage 61, and prevents the hydraulic oil from flowing from the first oil passage 61 to the second oil passage 62. It is. In the first oil passage 61, a second bypass oil passage 69 may be provided between the brake switching valve 80a and the third oil passage 63. A second check valve 72 is provided in the second bypass oil passage 69. The second check valve 72 allows the operating oil from the connection between the first oil passage 61 and the third oil passage 63 to the brake switching valve 80a, and the hydraulic oil flows from the brake switching valve 80a toward the connection. It is a valve that prevents flow.

As described above, when the first bypass oil passage 68 and the second bypass oil passage 69 are provided, the hydraulic oil in the second oil passage 62 is supplied to the first bypass oil passage 68 and the second bypass oil passage during warm-up. The oil can be passed through the oil passage 69 and discharged from the first discharge oil passage 66 of the brake switching valve 80a.
Although the first bypass oil passage 68 and the first check valve 71 are provided in the third oil passage 63, the first bypass oil passage 68 and the first check valve 71 may not be provided. Further, although the second bypass oil passage 69 and the second check valve 72 are provided in the first oil passage 61, the second bypass oil passage 69 and the second check valve 72 may not be provided. Alternatively, the hydraulic system of the work machine may include one of the first bypass oil passage 68 and the first check valve 71 and the second bypass oil passage 69 and the second check valve 72.

  FIG. 2C shows a second modification of FIG. 2B. In the second modification, as shown in FIG. 2C, the brake operation valve is changed to an electromagnetic proportional valve (brake switching valve) 80b. The brake proportional valve 80b has a primary port (pump port) 80b1 and a secondary port 80b2. A primary port 80b1 of the brake proportional valve 80b is connected to the discharge oil passage 40. The secondary port 80b2 of the brake proportional valve 80b is connected to the first oil passage 61. The discharge port 80b3 of the brake proportional valve 80b is connected to the hydraulic oil tank 22 via the first discharge oil passage 66. In the brake proportional valve 80b, the first set pressure PV1 is the pressure of the secondary port 80b2. In FIG. 2C, the first bypass oil passage 68 is provided with a throttle portion 76.

  In the second modification, the control device 90 sets the opening of the brake proportional valve 80b to the maximum so as to be equal to or higher than the release pressure at which the brake mechanism 30 releases the braking in the warm-up mode, while changing the gear ratio. The opening of the valve 81b is set to the minimum (the opening corresponding to the first speed). That is, in the warm-up mode, the control device 90 sets the shift set pressure PV2 of the shift proportional valve 81b to a deceleration pressure at which the shift mechanism decelerates the brake set pressure PV1 of the brake proportional valve 80b to the release pressure or more.

  Therefore, even when the brake switching valve 80a is changed to the brake proportional valve 80b, the brake set pressure PV1> the shift set pressure PV2 is set by setting the opening of the brake proportional valve 80b and the shift proportional valve 81b. be able to. Also in this case, the hydraulic oil that has passed through the brake proportional valve 80b flows through the first oil passage 61 and the third oil passage 63 to the second oil passage 62, and from the discharge port 81b3 of the speed change proportional valve 81b to the second oil discharge. It can be discharged to the road 67.

  In the first modified example, the control device 90 minimizes the opening of the brake proportional valve 80b so that the braking pressure is controlled by the brake mechanism 30 in the warm-up mode, while the shift proportional valve 81b May be set to the maximum (opening degree corresponding to the second speed). That is, in the warm-up mode, the control device 90 sets the brake set pressure PV1 of the brake proportional valve 80b to the braking pressure, and sets the shift set pressure PV2 of the shift proportional valve 81b to the speed increasing pressure at which the speed change mechanism increases the speed. According to this, by setting the opening of the brake proportional valve 80b and the shift proportional valve 81b, it is possible to set the brake set pressure PV1 <the shift set pressure PV2. In this case, the hydraulic oil that has passed through the shift proportional valve 81b flows through the second oil passage 62 and the third oil passage 63 to the first oil passage 61, and from the discharge port 80b3 of the brake proportional valve 80b to the first discharge oil passage. 66 can be discharged.

  In the second modified example, in the warm-up mode, the brake set pressure PV1 is determined by setting the opening of the brake proportional valve 80b to the maximum and the minimum. It may be changed arbitrarily. For example, in the warm-up mode, the magnitude of the differential pressure between the brake set pressure PV1 and the shift set pressure PV2 can be changed by arbitrarily changing the opening of the brake proportional valve 80b. Also, in the case of the second modification, similarly to the first modification, the control device 90 may change the opening of the brake proportional valve 80b based on the temperature detected by the temperature detection device 91. Further, in the second modification, as shown in FIG. 2C, a third check valve 75 may be provided in the third oil passage 63. The third check valve 75 allows the operating oil from the second oil passage 62 to the first oil passage 61 and limits the operating oil from the first oil passage 61 to the second oil passage 62.

  FIG. 2D shows a third modification of FIG. 2A. In the third modification, in a hydraulic circuit provided with a brake switching valve 80a and a shift switching valve 81a, a throttle portion 73 is provided in a third oil passage 63, and a first bypass oil passage 68 is provided at both ends of the throttle portion 73. A first check valve 71 is provided in the first bypass oil passage 68. In the second oil passage 62, a throttle portion 83 is provided in a section between the shift switching valve 81 a and the junction 65. In such a case, the control device 90 performs the braking by the brake mechanism 30 and switches the shift switching valve 81a to the second position 81a2, so that the operating oil in the second oil passage 62 is transferred to the first bypass oil passage 68 to the first bypass oil passage 68. It can be discharged to the first discharge oil passage 66 of the brake switching valve 80a via the one check valve 71.

  In the above-described embodiment, a first measurement valve capable of measuring a first set pressure (brake set pressure) PV1 set by a first operation valve, that is, a brake operation valve (a brake switching valve 80a, a brake proportional valve 80b). , A second operating valve, that is, a second measuring device capable of measuring a second set pressure (shift setting pressure) PV2 set by the shift operating valves (the shift switching valve 81a and the shift proportional valve 81b). In the case of the machine mode, the control device 90 controls the first operating valve and the second operating valve so that the brake setting pressure PV1> the shift setting pressure PV2 or the brake setting pressure PV1 <the shift setting pressure PV2. Good. The control device 90 estimates the first set pressure (brake set pressure) PV1 and the second set pressure (gear set pressure) PV2 from the drive (discharge pressure, rotation speed, etc.) of the first hydraulic pump P1, the rotation speed of the prime mover, and the like. Thus, the first operating valve and the second operating valve may be controlled.

  Although the present invention has been described above, the embodiments disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. The first operating valve may be a valve other than the brake operating valve that controls the operating oil supplied to the brake mechanism 30. The second operation valve may be a valve other than the speed change operation valve that controls the operation oil supplied to the speed change mechanism.

  The transmission mechanism may be any mechanism that can change the speed of the traveling device 5, and may be HST pumps (traveling pumps) 52L and 52R, or other hydraulic devices. The shift operation valve may be any valve that changes the hydraulic oil supplied to the transmission mechanism. A valve that controls the swash plates of the HST pumps (traveling pumps) 52L and 52R by supplying the hydraulic oil (HST pump proportional valve) ), A valve (anti-stall proportional valve) that can change the hydraulic oil supplied to the HST pumps (traveling pumps) 52L and 52R via the operation valve 55 may be used.

REFERENCE SIGNS LIST 1 work machine 7 traveling device 30 brake mechanism 61 first oil passage 62 second oil passage 63 third oil passage 66 first discharge oil passage 67 second discharge oil passage 68 first bypass oil passage 71 first check valve 80a brake Operating valve 81a Variable speed operating valve P1 Hydraulic pump

Claims (8)

A hydraulic pump that discharges hydraulic oil,
A brake mechanism that performs braking of the traveling device and release of the braking based on the pressure of the hydraulic oil,
A transmission mechanism that changes the speed of the traveling device based on the pressure of the hydraulic oil,
A brake actuation valve for controlling the hydraulic oil supplied to the brake mechanism,
A shift operating valve that controls operating oil supplied to the shift mechanism;
A first oil passage connecting the brake mechanism and the brake actuation valve;
A second oil passage connecting the speed change mechanism and the speed change operation valve;
A third oil passage connecting the first oil passage and the second oil passage,
A first discharge oil passage communicating with the brake operation valve and discharging hydraulic oil passing through the brake operation valve;
A second discharge oil passage communicating with the shift operation valve and discharging hydraulic oil passing through the shift operation valve;
With
A hydraulic system for a working machine, wherein a brake set pressure of hydraulic oil set by the brake operating valve is higher than a shift set pressure of hydraulic oil set by the shift operating valve. The brake actuating valve sets the brake set pressure to a release pressure at which the brake mechanism releases the braking,
The hydraulic system for a working machine according to claim 1, wherein the shift operation valve sets the shift setting pressure to a deceleration pressure at which the speed change mechanism reduces the speed of the traveling device.   The brake operation valve is configured to switch between a first position in which the brake setting pressure is set to a braking pressure at which the brake mechanism performs the braking and a second position in which the brake setting pressure is set to the release pressure. The hydraulic system for a working machine according to claim 2, which is a valve.   The shift operation valve switches between a first position at which the shift setting pressure is set to the deceleration pressure and a second position at which the shift mechanism sets the speed of the traveling device higher than a predetermined speed by the transmission mechanism. The hydraulic system for a working machine according to claim 2, wherein the hydraulic system is a possible gearshift valve.   The hydraulic system according to claim 2, wherein the brake actuating valve is a brake proportional valve capable of changing the brake set pressure from a braking pressure at which the brake mechanism performs the braking to the release pressure.   3. The brake shift valve according to claim 2, wherein the shift operation valve is a brake proportional valve that can change the shift setting pressure from an increased pressure at which the speed change mechanism makes the speed of the traveling device faster than a predetermined speed to the deceleration pressure. 4. Working machine hydraulic system.   The hydraulic system for a working machine according to any one of claims 1 to 6, further comprising a throttle portion provided in the third oil passage. A first bypass oil passage connected to the third oil passage;
A first reverse provided in the first bypass oil passage and allowing the hydraulic oil from the second oil passage to the first oil passage and restricting the hydraulic oil from the first oil passage to the second oil passage. The hydraulic system for a working machine according to any one of claims 1 to 6, further comprising a stop valve.

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