JP7329924B2 - work machine - Google Patents

Description

The present invention relates to working machines.

It has an engine, a variable displacement hydraulic pump to which the power of the engine is input, and a variable displacement or constant displacement hydraulic motor connected to the hydraulic pump by a pair of driving oil passages, and propels the power of the engine forward. 2. Description of the Related Art There is a working machine provided with a hydrostatic continuously variable transmission that converts power into reverse power and outputs it, and a traveling device that is driven by the output of the continuously variable transmission. As a work machine of this type, there is a tractor provided with front wheels and rear wheels as a traveling device, as disclosed in Patent Document 1, for example.
In equipment equipped with a hydrostatic continuously variable transmission, when the driving load of the traveling device increases beyond the set value, the motor displacement is increased by operating the motor swash plate with pressure oil in the driving oil passage of the continuously variable transmission. In some cases, a load-sensitive speed reduction mechanism is configured to increase speed and increase speed reduction and output torque. This type of device is disclosed in, for example, Patent Document 2. The one disclosed in Patent Document 2 is provided with a load control mechanism that tilts the swash plate of the hydraulic motor to the deceleration side by operating the hydraulic servo mechanism of the hydraulic motor. When the continuously variable transmission is moving forward, the hydraulic pressure in the main oil passage, which is the high-pressure side of the pair of main oil passages connecting the hydraulic pump and the hydraulic motor, is used as pressure oil to operate the swash plate for load control. mechanism, and when the continuously variable transmission is in reverse, the hydraulic pressure of the main oil passage, which is the high pressure side of the pair of main oil passages connecting the hydraulic pump and the hydraulic motor, operates the swash plate. is introduced into the load control mechanism as pressure oil for performing

JP 2012-77763 A Japanese Unexamined Patent Application Publication No. 2007-92807

When the conventional technology is adopted, the swash plate is decelerated from the driving oil passage, which is on the high pressure side when the continuously variable transmission is in the forward drive state, out of the pair of driving oil passages connecting the hydraulic pump and the hydraulic motor. and a pair of drive oil passages connecting the hydraulic pump and the hydraulic motor, which are on the high pressure side when the continuously variable transmission is in the reverse driving state. Since a take-out oil passage for extracting hydraulic pressure for decelerating the swash plate is required, the oil passage structure becomes complicated and the continuously variable transmission becomes large.

The present invention detects a change in the drive load of the traveling device by a change in the oil pressure of the drive oil passage during both forward and reverse travel, and decelerates the swash plate by using the oil pressure of the drive oil passage as a deceleration operation force. To provide a work machine capable of suppressing an increase in the size of a continuously variable transmission while maintaining the

A work machine according to the present invention includes:
engine and
A variable displacement hydraulic pump to which the power of the engine is input, and a variable displacement hydraulic motor connected to the hydraulic pump by a pair of driving oil passages, wherein the power of the engine is forward power and reverse power. A hydrostatic continuously variable transmission that converts and outputs to
a traveling device driven by the output of the continuously variable transmission;
a load sensitive speed reduction mechanism that reduces speed of the continuously variable transmission by pressure oil in the driving oil passage when the driving load of the traveling device increases to a set value or more;
The load sensitive deceleration mechanism is
a resistance mechanism that applies resistance to tilting of the swash plate of the hydraulic motor toward the deceleration side;
a hydraulic actuator capable of tilting the swash plate to the deceleration side against the resistance mechanism;
When the continuously variable transmission is in a forward driving state, hydraulic pressure is taken into the hydraulic actuator from the high-pressure side drive oil passage of the pair of drive oil passages, and the taken-in hydraulic pressure pushes the hydraulic actuator against the resistance mechanism. When the continuously variable transmission is in the reverse driving state, hydraulic pressure is taken into the hydraulic actuator from the low pressure side driving oil passage of the pair of driving oil passages, and the hydraulic actuator is driven by the hydraulic pressure taken in. and a deceleration operation oil passage for driving against the mechanism,
A first relief circuit connected to one of the pair of drive oil passages, which is connected to the drive oil passage that is on the high pressure side when the continuously variable transmission is in the forward driving state; a second relief circuit connected to the drive oil passage that becomes a high pressure side when the continuously variable transmission is in a reverse drive state;
the relief pressure of the second relief circuit is set lower than the relief pressure of the first relief circuit ;
The moment acting on the swash plate due to the operation of the piston of the hydraulic motor is a moment in the direction opposite to the direction of tilting the swash plate toward the speed reduction side in the forward drive state of the continuously variable transmission. When the transmission is in the reverse drive state, the moment is in the same direction as the direction of tilting the swash plate toward the deceleration side. The continuously variable transmission is decelerated by the load sensitive deceleration mechanism when the drive load is lower than the load.

According to this configuration, since the traveling device is switched between forward drive and reverse drive by the continuously variable transmission, the continuously variable transmission is used only for outputting forward power, and forward power output by the continuously variable transmission is used as reverse power. The gear mechanism can be omitted compared to adopting a gear mechanism that converts to and transmits to the traveling device. A drive circuit to which the hydraulic actuator receives hydraulic pressure for operating the swash plate to the deceleration side in the forward drive state of the continuously variable transmission, and hydraulic pressure to operate the swash plate to the deceleration side in the reverse drive state of the continuously variable transmission. is the same drive oil passage as the drive oil passage into which is incorporated into the hydraulic actuator, and the deceleration operation oil passage is shared for forward and reverse travel, simplifying the hydraulic structure. structure. Therefore, the work machine can be downsized.

In the present invention, it is preferable that the resistance mechanism is a spring.

According to this configuration, a compact resistance mechanism can be obtained, so that an increase in the size of the continuously variable transmission can be further suppressed.

In the present invention, it is preferable that the hydraulic actuator is a hydraulic piston, and the hydraulic piston and the spring are arranged in a direction along the swinging direction of the swash plate with an operation portion of the swash plate interposed therebetween. .

According to this configuration, since the hydraulic piston and the spring can be compactly installed together, it is possible to further suppress an increase in the size of the continuously variable transmission.

It is a side view showing the whole ride-on mower. It is a hydraulic circuit diagram of a continuously variable transmission. FIG. 4 is an explanatory diagram showing the moment acting on the swash plate of the hydraulic motor in the forward drive state of the continuously variable transmission; FIG. 4 is an explanatory diagram showing the moment acting on the swash plate of the hydraulic motor in the reverse driving state of the continuously variable transmission; FIG. 5 is an explanatory diagram showing test results of the load sensitive mechanism in the forward drive state of the continuously variable transmission; FIG. 10 is an explanatory diagram showing test results of the load sensitive mechanism in the reverse driving state of the continuously variable transmission;

An embodiment, which is an example of the present invention, will be described below with reference to the drawings.
In the following description, regarding the vehicle body of the riding lawn mower, the direction of arrow F shown in FIG. The direction of the arrow D is defined as "bottom of the vehicle body", the direction toward the front side of the paper is defined as "left side of the vehicle body", and the direction toward the back side of the paper is defined as "right side of the vehicle body".

[Regarding the entire riding lawn mower]
As shown in FIG. 1, the riding mower is equipped with a pair of left and right front wheels 1 as a traveling device that can be swung and steered, and a pair of left and right rear wheels 2 as a traveling device that can be driven. , a driver's seat 3 , and a driving section 5 having a steering wheel 4 for steering the front wheels 1 . A driving portion 7 having an engine 6 is formed in the front portion of the vehicle body. The power of the engine 6 is input to the rear part of the vehicle body. It is equipped with a mission 9 that transmits to Between the front wheels 1 and the rear wheels 2, a mowing device 10 for mowing grass and lawn is provided. The mowing device 10 is supported by the vehicle body via a link mechanism 11 extending from the vehicle body so as to be able to swing vertically. The mowing device 10 is moved up and down between a lowered working state and a raised non-working state by the swing motion of the link mechanism 11 . A grass collecting container 12 is supported on the rear part of the vehicle body. A conveying duct 13 is provided across the mowing device 10 and the grass container 12 to convey the cut grass and grass clippings obtained by the mowing device 10 to the grass collecting container 12 . The conveying duct 13 is provided so as to pass in the front-rear direction between the left and right rear wheels 2 below the vehicle body. The grass collection container 12 includes a support frame 14 erected at the rear part of the vehicle body, and a pair of left and right links extending rearward from the support frame 14 to both lateral sides of the grass collection container 12 so as to be vertically swingable. It is supported by the rear part of the vehicle body via the mechanism 14A. The grass collection container 12 is moved up and down through a downward storage state in which the grass clippings and grass clippings are stored and an ascending discharge state in which the stored grass clippings and grass clippings are discharged by the rocking motion of the left and right link mechanisms 14A.

[Structure of continuously variable transmission]
The continuously variable transmission 8, as shown in FIG. and a variable displacement hydraulic motor 17 connected by oil passages 16a and 16b and driven by hydraulic pressure supplied from the hydraulic pump 15 through a pair of driving oil passages 16a and 16b. The continuously variable transmission 8 is configured as a hydrostatic continuously variable transmission. The power of a motor shaft 17 a (see FIG. 3) of the hydraulic motor 17 is input to the transmission 9 . A hydraulic motor 17 drives the left and right rear wheels 2 via a transmission 9 . As shown in FIG. 2, a shift operation tool 19 is linked to the swash plate 15a of the hydraulic pump 15. As shown in FIG.
A load sensitive speed reduction mechanism 20 is linked to the hydraulic motor 17 .

In the continuously variable transmission 8, when the speed change operation tool 19 is operated from the neutral position to the forward position, the swash plate 15a is tilted forward, and the hydraulic pump 15 is connected to one of the pair of drive oil passages 16a and 16b. Hydraulic oil is supplied to the hydraulic motor 17 through one of the driving oil passages 16a, and from the hydraulic motor 17 to the hydraulic pump 15 through the other driving oil passage 16b of the pair of driving oil passages 16a and 16b. is returned, and the hydraulic motor 17 is driven forward at a rotational speed corresponding to the operating position of the shift operation tool 19 . That is, the continuously variable transmission 8 shifts to the forward drive side gear shift state corresponding to the operating position of the gear shift operation tool 19, converts the power from the engine 6 into forward drive power, and outputs the power from the hydraulic motor 17 so that the rear wheels 2 to the forward direction at a rotational speed corresponding to the operating position (forward position) of the shift operation tool 19 . At this time, one drive oil passage 16a of the pair of drive oil passages 16a and 16b is the high pressure side drive oil passage, and the other of the pair of drive oil passages 16a and 16b is the low pressure side drive oil passage 16b. It becomes a drive oil passage.

In the continuously variable transmission 8, when the speed change operation tool 19 is operated from the neutral position to the reverse position, the swash plate 15a is tilted to the reverse direction, and the hydraulic pump 15 is connected to one of the pair of drive oil passages 16a and 16b. Hydraulic oil is supplied to the hydraulic motor 17 through the other drive oil passage 16b, and the hydraulic oil is supplied from the hydraulic motor 17 to the hydraulic pump 15 through one of the pair of drive oil passages 16a and 16b. is returned, and the hydraulic motor 17 is driven backward at a rotational speed corresponding to the operating position of the shift operation tool 19 . That is, the continuously variable transmission 8 shifts to the reverse drive side shift state corresponding to the operating position of the speed change operation tool 19 , converts the power from the engine 6 into reverse drive power, and outputs the power from the hydraulic motor 17 . is driven to the reverse side at a rotational speed corresponding to the operation position (reverse position) of the shift operating tool 19 . At this time, the other drive oil passage 16b of the pair of drive oil passages 16a and 16b is the high pressure side drive oil passage, and one of the pair of drive oil passages 16a and 16b is the low pressure side drive oil passage. It becomes a drive oil passage.

[Regarding the configuration of the load sensitive deceleration mechanism]
The load sensitive speed reduction mechanism 20 increases the capacity of the motor when the drive load on the rear wheels 2 increases to a set value or more during both forward and reverse travel, thereby increasing the torque that can be output at the same pressure. increase.

Specifically, as shown in FIG. 3, the load sensitive speed reduction mechanism 20 includes a spring 23 as a resistance mechanism against the swash plate 17b of the hydraulic motor 17 and a hydraulic pressure for tilting the swash plate 17b in the deceleration side tilting direction. It has a hydraulic piston 25 as an actuator, and a reduction operation oil passage 27 connected to an oil chamber 26 formed in a casing 21 of the continuously variable transmission 8 . The oil chamber 26 is formed in the port block portion 21 a of the casing 21 . The springs 23 and the hydraulic pistons 25 are arranged in a direction along the swinging direction of the swash plate 17b with the operating portion 17c of the swash plate 17b interposed therebetween. The axial center 23c of the spring 23 and the axial center 25c of the hydraulic piston 25 are close to each other and are substantially coaxial. A configuration in which the axial center 23c of the spring 23 and the axial center 25c of the hydraulic piston 25 are coaxial may be adopted.

A spring chamber 22 is formed in a portion of the casing 21 opposite to the side where the piston 17d of the hydraulic motor 17 is located with respect to the swash plate 17b. The spring 23 is provided in the spring chamber 22 so as to be positioned between a swash plate pushing member 28 slidably provided on the swash plate side portion of the spring chamber 22 and the back wall portion 22a of the spring chamber 22. . The spring 23 is interposed between the swash plate pressing member 28 and the inner wall portion 22a while being elastically deformed at an initial stage. The swash plate pressing member 28 is slidably biased by the spring 23 to the side coming out of the spring chamber 22 and is pressed against the operating portion 17c. The spring 23 biases the swash plate 17b toward the acceleration side. The swash plate 17b is tilted while being resisted by the spring 23 when tilted to the deceleration side.

In this embodiment, the spring 23 is fitted to a small-diameter spring 23a having one end inside the swash-plate pushing member 28 and the outer peripheral side of the small-diameter spring 23a so that one end comes into contact with the end of the swash-plate pushing member 28. and a large-diameter spring 23b in contact. However, the spring 23 can be provided with only one spring, or with three or more springs.

A support portion 24 is provided inside the casing 21 on the opposite side of the swash plate 17b to the spring 23 (the same side as the piston 17d). The support portion 24 extends from the port block portion 21a toward the swash plate 17b. The hydraulic piston 25 is slidably supported by the distal end portion of the support portion 24 . The hydraulic piston 25 is configured such that when the hydraulic piston 25 is slid to the side extending from the support portion 24 , the distal end portion of the hydraulic piston 25 pushes the operating portion 17 c against the spring 23 . The hydraulic piston 25 can tilt the swash plate 17b against the spring 23 toward the deceleration side.

As shown in FIGS. 2 and 3, the deceleration operation oil passage 27 connects the oil chamber 26 and the drive oil passage 16a of the pair of drive oil passages 16a and 16b. The drive oil passage 16a is the drive oil passage on the high pressure side when the continuously variable transmission 8 is in the forward drive state, and is the drive oil passage on the low pressure side when the continuously variable transmission 8 is in the reverse drive state. This is the drive oil passage. As shown in FIG. 3 , an oil passage 29 connecting the oil chamber 26 and the inside of the hydraulic piston 25 is formed inside the support portion 24 . The hydraulic pressure of the drive oil passage 16a is introduced into the oil chamber 26 through the speed reduction operation oil passage 27, and the introduced oil pressure enters the hydraulic piston 25 through the oil passage 29, whereby the oil pressure of the drive oil passage 16a is transferred to the speed reduction operation oil passage. 27 into the hydraulic piston 25 . When hydraulic pressure is applied to the hydraulic piston 25, depending on the strength of the hydraulic pressure, the hydraulic piston 25 is slid to the side extending from the support portion 24 against the spring 23, and presses the operating portion 17c. The swash plate 17b is tilted to the deceleration side.

3 and 4 are explanatory diagrams showing the moment acting on the swash plate 17b of the hydraulic motor 17 in the driving state of the continuously variable transmission 8. FIG. 3 and 4, the swash plate 17b of the hydraulic motor 17 is tilted in the tilting direction (clockwise direction) indicated by the arrow Z, thereby tilting to the deceleration side.

FIG. 3 is an explanatory diagram showing the moment acting on the swash plate 17b of the hydraulic motor 17 in the forward driving state of the continuously variable transmission 8. As shown in FIG. A moment M1 shown in FIG. 3 is a moment acting on the swash plate 17b due to the pushing operation of the operation portion 17c by the spring 23, and is a moment in the direction opposite to the direction of tilting the swash plate 17b toward the deceleration side. The moment M2 shown in FIG. 3 is the moment acting on the swash plate 17b due to the operation of the hydraulic piston 25, that is, the moment caused by the hydraulic pressure in the drive oil passage 16a, and is the moment in the direction of tilting the swash plate 17b toward the deceleration side. . Moment M3 shown in FIG. 3 is the moment acting on the swash plate 17b due to the operation of the piston 17d of the hydraulic motor 17, that is, the moment due to forward driving of the hydraulic motor 17, and tilts the swash plate 17b toward the deceleration side. It is the moment in the opposite direction.

FIG. 4 is an explanatory diagram showing the moment acting on the swash plate 17b of the hydraulic motor 17 when the continuously variable transmission 8 is in the reverse driving state. The moment M1 shown in FIG. 4 is the moment acting on the swash plate 17b due to the pushing operation of the operating portion 17c by the spring 23, and both the direction and the strength are the same as the moment M1 in the forward driving state of the continuously variable transmission 8. Same moment. The moment M4 shown in FIG. 4 is the moment acting on the swash plate 17b due to the operation of the hydraulic piston 25, that is, the moment due to the hydraulic pressure in the drive oil passage 16a, and is the moment in the direction of tilting the swash plate 17b toward the deceleration side. . The moment M5 shown in FIG. 4 is the moment acting on the swash plate 17b due to the operation of the piston 17d of the hydraulic motor 17, that is, the moment due to the backward driving of the hydraulic motor 17, and is in the direction of tilting the swash plate 17b toward the deceleration side. Moment. The direction of the moment M3 in the forward drive state of the continuously variable transmission 8 and the direction of the moment M5 in the reverse drive state of the continuously variable transmission 8 are opposite.

Moment M2 when the driving load of the rear wheel 2 (output torque of the continuously variable transmission 8) reaches the set value R1 (see FIG. 5) in the forward driving state of the continuously variable transmission 8, forward driving of the continuously variable transmission 8 Moment M3 when the driving load on the rear wheels 2 reaches the set value R1 (see FIG. 5) in the state of FIG. and a moment M5 when the drive load of the rear wheels 2 reaches a set value R2 (see FIG. 6) in the reverse drive state of the continuously variable transmission 8, and the detected moments M2, M3, Based on M4 and M5, when the driving load of the rear wheel 2 becomes equal to or greater than the set value R1 during forward and backward travel, the swash plate 17b is tilted toward the deceleration side. 23 set load (initial elastic deformation in the assembled state) is calculated. The spring 23 is provided with the calculated spring constant and the calculated initial elastic deformation (set load).

5 and 6 are explanatory diagrams showing test results of the load sensitive deceleration mechanism 20 in this embodiment. FIG. 5 is an explanatory diagram showing the test results in the forward drive state of the continuously variable transmission 8. In this test, the input speed of the continuously variable transmission 8 was set to 1500 [rpm], 8 is set as the maximum forward speed. FIG. 6 is an explanatory diagram showing the test results in the reverse driving state of the continuously variable transmission 8. In this test, the input rotation speed of the continuously variable transmission 8 was set to 1500 [rpm], and the continuously variable transmission 8 is set as the maximum reverse speed. The relief pressure of the relief circuit 30 (first relief circuit, see FIG. 2) of the drive oil passage 16a, which is on the high pressure side in the forward drive state, is set at 24.5 MPa, and is on the high pressure side in the reverse drive state. The relief pressure of the relief circuit 31 (second relief circuit, see FIG. 2) of the drive oil passage 16b is set to 20.6 [MPa]. The vertical axis on the left side in FIGS. 5 and 6 indicates the driving load R of the rear wheel 2, and the higher the load, the higher the load. The vertical axis on the right side in FIGS. 5 and 6 indicates the swash plate angle K of the hydraulic motor 17, and the higher the swash plate angle, the lower the speed. The horizontal axis in FIG. 5 represents the effective pressure P (pressure in the oil passage 16a−pressure in the oil passage 16b) effective for swash plate operation, and the horizontal axis in FIG. pressure). A line X shown in FIGS. 5 and 6 indicates changes in the swash plate angle K, and a line Y indicates changes in the drive load R. As shown in FIG.

As shown in FIG. 5, in the forward driving state, when the drive load R becomes equal to or greater than the set value R1, the effective pressure P becomes equal to or greater than P1 {8 [MPa]}, and when the effective pressure P becomes equal to or greater than P1, the swash plate Angle K is changing to the deceleration side. As shown in FIG. 6, in the reverse drive state, when the drive load R becomes equal to or greater than the set value R2, the effective pressure P becomes equal to or greater than P2 {6 [MPa]}, and when the effective pressure P becomes equal to or greater than P2, the swash plate Angle K is changing to the deceleration side.

In the load sensitive deceleration mechanism 20, the hydraulic pressure in the driving oil passage 16a, which is one of the pair of driving oil passages 16a and 16b and becomes the high pressure side during forward movement and the low pressure side during reverse movement, and the hydraulic pressure in the piston of the hydraulic motor 17, , changes in the driving load of the rear wheels 2 during forward and backward travel are detected, and when moving forward, the hydraulic pressure of the driving oil passage 16a is used as a deceleration operation force, and when reversing, the hydraulic pressure of the driving oil passage 16a and the hydraulic motor are detected. The swash plate 17b of the hydraulic motor 17 is tilted to the deceleration side by using the hydraulic pressure in the piston 17 as a deceleration operation force.

That is, in the forward drive state of the continuously variable transmission 8 , the oil pressure of the drive oil passage 16 a , which is on the high pressure side of the pair of drive oil passages 16 a and 16 b, is taken into the hydraulic piston 25 through the deceleration operation oil passage 27 . In the reverse drive state of the continuously variable transmission 8 , the oil pressure of the drive oil passage 16 a , which is on the low pressure side of the pair of drive oil passages 16 a and 16 b, is taken into the hydraulic piston 25 through the speed reduction operation oil passage 27 . When driving forward, when the driving load R of the rear wheels 2 becomes equal to or greater than the set value R1, the moment M2 shown in FIG. , the swash plate 17b is tilted to the deceleration side. On the other hand, when the driving load R of the rear wheels 2 becomes equal to or greater than the set value R2, the sum of the moment M4 and the moment M5 shown in FIG. As a result, the swash plate 17b is tilted toward the deceleration side.

[Another embodiment]
(1) In the above-described embodiment, an example in which the spring 23 is employed as the resistance mechanism is shown, but it is not limited to the spring 23, and various elastic members such as rubber can be employed. Also, although two springs 23a and 23b are employed, it is possible to employ only one or three or more springs.

(2) In the described embodiment, only the rear wheels 2 out of the front wheels 1 and the rear wheels 2 are driven. may be configured as follows. Alternatively, only the front wheels 1 out of the front wheels 1 and the rear wheels 2 may be driven.

(3) In the above-described embodiment, only the hydraulic piston 25 is used as the hydraulic actuator. However, the present invention is not limited to this. A combination of and may be adopted.

(4) In the above-described embodiment, an example provided with the front wheels 1 and the rear wheels 2 was shown, but a crawler traveling device or a wheel and a semi-crawler may be provided.

The present invention is applicable not only to ride-on mowers, but also to various working machines such as tractors and trucks.

6 engine 15 hydraulic pump 17 hydraulic motor 17b swash plate 17c operation part 23 resistance mechanism (spring)
25 hydraulic actuator (hydraulic piston)
27 deceleration operation oil passage 30 relief circuit (first relief circuit)
31 relief circuit (second relief circuit)
M3 moment
M5 moment

Claims (3)

engine and
A variable displacement hydraulic pump to which the power of the engine is input, and a variable displacement hydraulic motor connected to the hydraulic pump by a pair of driving oil passages, wherein the power of the engine is forward power and reverse power. A hydrostatic continuously variable transmission that converts and outputs to
a traveling device driven by the output of the continuously variable transmission;
a load sensitive speed reduction mechanism that reduces speed of the continuously variable transmission by pressure oil in the driving oil passage when the driving load of the traveling device increases to a set value or more;
The load sensitive deceleration mechanism is
a resistance mechanism that applies resistance to tilting of the swash plate of the hydraulic motor toward the deceleration side;
a hydraulic actuator capable of tilting the swash plate to the deceleration side against the resistance mechanism;
When the continuously variable transmission is in a forward driving state, hydraulic pressure is taken into the hydraulic actuator from the high-pressure side drive oil passage of the pair of drive oil passages, and the taken-in hydraulic pressure pushes the hydraulic actuator against the resistance mechanism. When the continuously variable transmission is in the reverse driving state, hydraulic pressure is taken into the hydraulic actuator from the low pressure side driving oil passage of the pair of driving oil passages, and the hydraulic actuator is driven by the hydraulic pressure taken in. and a deceleration operation oil passage for driving against the mechanism,
A first relief circuit connected to one of the pair of drive oil passages, which is connected to the drive oil passage that is on the high pressure side when the continuously variable transmission is in the forward driving state; a second relief circuit connected to the drive oil passage that becomes a high pressure side when the continuously variable transmission is in a reverse drive state;
the relief pressure of the second relief circuit is set lower than the relief pressure of the first relief circuit ;
The moment acting on the swash plate due to the operation of the piston of the hydraulic motor is a moment in the direction opposite to the direction of tilting the swash plate toward the speed reduction side in the forward drive state of the continuously variable transmission. When the transmission is in the reverse drive state, the moment is in the same direction as the direction of tilting the swash plate toward the deceleration side. a work machine in which the continuously variable transmission is operated to reduce speed by the load sensitive speed reduction mechanism in a state where the drive load is lower than the load. The working machine according to claim 1, wherein the resistance mechanism is a spring. the hydraulic actuator is a hydraulic piston,
3. A working machine according to claim 2, wherein said hydraulic piston and said spring are arranged in a direction along the swinging direction of said swash plate with an operation portion of said swash plate interposed therebetween.

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