JPH09229002A - Hydraulic mechanism of running vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lighten abrasion of a brake and sudden stop feeling due to braking during running drive by a negative brake additively provided along a hydraulic motor, and avoid spin turn at high speed running, in a HST drive type running vehicle (crawler tractor and the like). SOLUTION: This transmission mechanism is provided so that the movable swash plate of a running hydraulic pump P is returned to the neutral position by step operation of a brake pedal 9, an orifice Ba is interposed on the oil returning circuit B of a brake valve V1 controlling pressure oil supply to the negative brake NB of a running hydraulic motor M, and the restriction quantity of the orifice Ba is set so that the negative brake NB is operated to brake after the movable swash plate is returned to the neutral position. When a handle 8 is operated to turn over a fixed turning operation quantity, a low-high speed changeover valve V2 is changed over, and the low-high speed changeover valve V3 of the running hydraulic motor M is set on the low speed position.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to left and right independent HSTs.
The present invention relates to a hydraulic mechanism in a traveling vehicle traveling by a drive type traveling device, for example, a crawler traveling device, and target traveling vehicles include a combine and a crawler tractor.

[0002]

2. Description of the Related Art Conventionally, a traveling vehicle having an HST drive type traveling device such as a crawler traveling device independently on the left and right has been known as disclosed in Japanese Patent Laid-Open No. 5-254456. Among the hydraulic mechanisms, first, a hydraulic motor equipped with a negative type brake device for applying a load to the rotation of an axle transmission system for braking is known, and further, a brake device of such a type is known. Japanese Patent Application Laid-Open No. 7-293499 discloses a configuration in which a braking force from the brake device is gradually applied in order to avoid the damage.

Some crawler traveling devices are provided with a spin turn mechanism for independently driving the drive wheels driven by hydraulic motors in opposite directions. That is, the directions of pressure oil discharge from the hydraulic pumps for the left and right traveling devices are opposite to each other. Further, a structure in which the left and right HST drive type traveling devices are operated and turned by a single steering device is also found in a combine, for example. this is,
When a single steering device (lever) is tilted to the side where it is about to turn, the driving wheels of the crawler traveling device on the turning side stop driving, and the driving wheels on the anti-turning side are driven. Then, such a steering device is provided with a spin turn switch, and when the switch is turned on, the drive wheel on the turning side is rotated in the reverse direction and the drive wheel on the anti-turning side is rotated in the normal direction to perform a spin turn. Is also known.

Conventionally, a traveling hydraulic pump in an HST drive type traveling vehicle is directly connected to the output shaft side of the engine, or the input shaft of the hydraulic pump is gear-engaged with the output shaft. Was.

Further, the tractor or the like has a hydraulic drive device such as a lifting device for a working machine. Since the case of this hydraulic drive device is conventionally located at a high position at the rear part of the vehicle body, the PTO shaft is also provided so as to project. The hydraulic oil of the hydraulic drive is circulated in both cases by sharing it with the lubricating oil of the transmission.

[0006]

In the above-mentioned prior art, first of all, the present invention is an invention relating to low-speed automatic switching at the time of turning and braking of a traveling vehicle and shock prevention. HS
As described above, the negative brake device provided in the hydraulic motor of the T drive type traveling vehicle is provided with the mechanism for gradually applying the braking force, but the hydraulic oil supply system from the hydraulic pump to the hydraulic motor and the operation of the brake are provided. It is completely independent of the above, and the brake operation can be performed during traveling driving, that is, even while the pressure oil is being discharged from the hydraulic pump. If the brake is operated at such a time, the rotational force of the axle transmission system of the hydraulic motor is very strong against the braking load of the brake device, so that the brake wear is accelerated and it cannot be used for a long period of time. Become.

Further, the spin-turn mechanism is provided with a turning operation amount of an operating device (a tilting angle in the case of a lever. In the case of a round handle,
There was no configuration to interlock with the steering wheel turning amount), and a cumbersome switch operation was required. And, the spin turn is the operation device (or other operation device for shifting),
Since the running speed is the same as when the switch is not turned on, the operator may be confused by a sudden turn. There has never been a mechanism that naturally reduces the running speed when the spin turn setting is set.

In the conventional hydraulic pump arrangement, the output of the hydraulic motor is limited because the pump shaft of the hydraulic pump can be driven only at the same rotational speed as the engine rotational speed. Further, recently, in order to reduce vibration and noise, vibration-proof support of the engine has been attempted. However, if a hydraulic pump is connected to the engine, it will be integrated into the engine, and the vibration-proof support target will become heavy and long. Therefore, the anti-vibration support structure requires higher rigidity. Further, when the hydraulic pump integrated with the engine is vibration-isolated and supported, the pipe distance between the hydraulic motor and the hydraulic motor mounted on the traveling device fluctuates with each vibration. Therefore, the hydraulic piping between the hydraulic pump and the hydraulic motor must be flexible, such as a rubber hose,
Such piping is vulnerable to foreign matter buffer and is easily damaged, so that replacement work has been frequently performed.

Further, if the construction is such that the hydraulic oil is circulated in the case of the hydraulic drive and the transmission case as in the conventional case, the circulation amount of the hydraulic oil in both cases increases, and the gears in the transmission are agitated accordingly. The resistance increased, causing a drop in drive efficiency and an increase in oil temperature. Further, wear powder of gears is generated in the transmission, but since this wear powder is mixed in the hydraulic oil of the hydraulic drive device, it is necessary to separately provide a filter.

[0010]

In order to solve the above problems, the present invention uses the following means. First of all, in an operating mechanism of a negative brake device that applies a load to the rotation of an axle attached to a hydraulic motor in an HST-driven traveling vehicle to brake, the hydraulic pump moves in conjunction with the braking operation by the operating mechanism. A mechanism is provided for moving the swash plate to the neutral position, and a mechanism for braking the negative brake device after the time required for the movable swash plate to reach the neutral position has elapsed.

Second, the two traveling devices independently of the HST
Equipped with, the discharge and discharge stop of the hydraulic pump of each traveling device HST by the turning operation of one steering device, and control of the discharge direction, when the turning operation amount of the steering device is a certain amount or more, In a hydraulic mechanism having a mechanism in which the discharge directions from both hydraulic pumps are opposite to each other, when the steering operation amount of the steering device is such that the discharge directions from the respective hydraulic pumps are opposite directions, the variable capacity type in both HSTs A mechanism is provided to switch the hydraulic motor to low speed drive.

Thirdly, in an HST drive type traveling vehicle, a traveling hydraulic pump is connected to a front portion of a transmission case arranged from an engine output shaft via a transmission shaft.

Fourthly, in a traveling vehicle having a hydraulic drive device, the case of the hydraulic drive device is arranged above the transmission case, and a partition wall is provided between both cases.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A traveling vehicle according to an embodiment of the present invention is a crawler tractor, and its hydraulic mechanism will be described with reference to the accompanying drawings. 1 is an overall side view of the crawler tractor, FIG. 2 is a side view showing a hydraulic drive system and a frame structure, FIG. 3 is a plan view of the same, and FIG. 4 is a side view of the hydraulic drive system.
FIG. 5 is a side view showing the steering and brake link mechanism, FIG. 6 is a front view of the same, FIG. 7 is a plan view of the steering gear box SB, FIG. 8 is a hydraulic travel drive system circuit diagram, and FIG. 9 is a hydraulic lift drive system circuit. FIG. 10, FIG. 10 is a plan view showing a piping structure for the traveling hydraulic motor M, FIG. 11 is a side view of the same, FIG. 12 is a front view of the same, and FIG. 13 is an operation of the traveling hydraulic pump P, the hydraulic valve V, and the hydraulic case 14. FIG. 14 is a plan view showing the oil supply pipe, and FIG. 14 is a side view of the same.

First, a schematic structure of a crawler tractor as an embodiment of the present invention will be described with reference to FIG. The main frame 1 is formed by combining the left and right main frames 1L and 1R.
Crawler frames 1La and 1Ra (collectively referred to as crawler frames 1a) are vertically supported below the respective 1Rs, and drive wheels equipped with traveling hydraulic motors ML and MR are provided at the front ends of the left and right crawler frames 1La and 1Ra, respectively. 2L
・ Suspending 2R, each crawler frame 1La ・ 1
In addition, a roller or an idler is suspended on Ra, and the crawler 3
Is wound around to form left and right crawler traveling devices.

On the other hand, the vehicle body portion is a tractor vehicle body, in which the bonnet 5 and the cabin 6 are arranged from the front portion, and the hydraulic lift 14a is projectingly provided from the rear end of the cabin 6, inside the cabin 6. A front column 7 is disposed in the front part, and a round handle 8 is projectingly provided at the upper rear of the front column 7, and the brake pedal 9 and the clutch are rotatably rotatable forward and backward at the left and right positions thereof. The pedal 10 is suspended.

A seat base 11 is arranged at the rear of the cabin 6 and a seat 12 is mounted on the seat base 11. On the side of the seat 12, an operation panel having a main gear shift lever 13 and the like is formed. There is. Further, inside the seat base 11, a transmission case TM and a hydraulic case 14 including a hydraulic lift 14a are provided. Lift adjustment lever 14
b is for adjusting the angle of the hydraulic lift 14a.
Further, the fenders 15 and 15 are provided on both sides of the seat base 11.
The fuel tank FT shown in FIG. 4 is provided inside the right fender 15, and the hydraulic oil tank LT is also provided inside the left fender 15. The bonnet 5 and the engine E and the like installed therein are the engine frame 4
The engine frame 4 and the side surface of the engine E are fixedly mounted on the main frame 1 and are vibration-proof supported to the main frame 1 via a vibration-proof rubber 16 or the like.

The drive system of this crawler tractor will be described with reference to FIGS. An engine E is arranged in the bonnet 5, a flywheel housing Ea is formed on the output side at the rear end, and an output shaft 17 protruding from the flywheel housing is connected to a transmission shaft 18 via a universal joint. The front end is connected and the rear end is connected to the input shaft 19 of the transmission case TM arranged near the rear end between the main frames 1L and 1R by a universal joint. As shown in FIG. 3, both sides of the transmission case TM have left and right main frames 1L and 1R.
Is screwed to. The hydraulic case 14 is disposed on the transmission case TM.

The front end of the transmission case TM is connected to a traveling hydraulic pump P in front of it. A pump shaft 20 of the hydraulic pump P is supported by a gear meshing with the input shaft 19 in the transmission case TM. A steering gear box SB is disposed below the output shaft of the engine E and in front of the traveling hydraulic pump P. The steering gear box SB is provided with the steering wheel 8 and other operating devices. And a connecting mechanism for connecting the link mechanism to the traveling hydraulic pump P.

The traveling hydraulic pump P is formed by connecting two independent traveling hydraulic pumps PL and PR in front and back, and as shown in FIGS. 10 to 12, the traveling hydraulic pump left from the front traveling hydraulic pump PL. Two drive hydraulic pipes 43La for ML
43Lb is provided with two drive hydraulic pipes 43Ra and 43Rb from the rear traveling hydraulic pump PR to the right hydraulic motor MR to form an HST for independently driving the left and right crawler traveling devices. (When the left and right HSTs are generically referred to, the drive hydraulic pipe 43a is referred to as the traveling hydraulic pump P.
-43b shall be connected to the traveling hydraulic motor M.
Further, the drive hydraulic pipes 43a and 43b are collectively referred to as the drive hydraulic pipe 43. )

Here, the pipe protection structure of the drive hydraulic pipe 43 will be described. First, the drive hydraulic pipe 43 is made of a steel pipe. Steel pipes are strong against obstacles and high pressure. However, it is not as flexible as a rubber hose. Conventionally, since the traveling hydraulic pump P is mounted on the engine side, the pipe distance fluctuates between the traveling hydraulic motor mounted on the main frame that supports the engine in a vibration-proof manner. It was necessary to pipe a flexible rubber hose, but the crawler tractor of this embodiment
From the traveling hydraulic pump P integrally connected to the transmission case TM that is screwed and fixed to the main frame 1, the traveling hydraulic motor M that is also fixed to the main frame 1 is used.
Since there is no need for flexible piping, it is not necessary to use flexible piping. Therefore, the drive hydraulic pipe 43 of a steel pipe having high strength can be provided.

Furthermore, in the case of a steel pipe, since slack does not occur, it is possible to pipe in a straight line, and the portion to be routed to the hydraulic port can also be bent without being bent. In the present embodiment, the drive hydraulic pipe 43 is bent at the upper rear part of the traveling hydraulic motor M and is linearly connected to the hydraulic port. Therefore, in the vicinity of the traveling hydraulic motor M, the drive hydraulic pipe 43 is externally connected. It does not stick out, and the ground clearance of the piping for the hydraulic port is also high, providing high protection from obstacles.

Further, the drive hydraulic pipe 43 from the rear traveling hydraulic pump P to the front traveling hydraulic motor M is provided along the inner side of the main frame 1 (1L / 1R).
Piping can be protected without providing a separate protective cover. Since there is no hydraulic piping from the traveling hydraulic pump P to the traveling hydraulic motor M between the left and right main frames 1L and 1R, the minimum ground clearance is the height of the lower end of the drive system member from the engine E to the transmission case TM. Even on rough terrain that has been lifted up to this point, you can run without worrying about contact with hydraulic pipes.

Further, the traveling hydraulic motor M is a variable displacement motor, as can be seen from the hydraulic circuit diagram of FIG. 8, and has a hydraulic low speed switching valve V3 installed therein. Further, a negative brake NB that brakes by pressure contact with the drive wheels 3 is provided internally, and the negative brake NB is
It is hydraulically operated. On the other hand, a hydraulic valve V is arranged above the steering gear box SB, which has a brake valve V1 on the upper part and a low / high speed switching control valve V2 (a pilot pressure oil on the low / high speed switching valve V3). The valve that supplies the.) Further, a hydraulic pipe is a steel pipe from the hydraulic valve V to the traveling hydraulic motor M, and a hydraulic pipe not shown from the brake valve V1 (this is not a steel pipe).
From the low / high speed switching control valve V2,
As shown in FIG. 1, the low-high speed switching hydraulic pipe 46 is extended forward, and the right main frame 1R is located above the traveling hydraulic motor M.
The branch port 4 is connected to the branch port 44 arranged above.
4 to the left and right traveling hydraulic motors ML and MR, as shown in FIGS. 10 to 12, vertical in side view, horizontal in plan view,
Then, the negative brake NB is bent into an L-shape when viewed from the front, and the negative brake NB is provided with a brake hydraulic pipe 45 so as not to protrude outside.
L / 45R and low / high speed switching valve V3 are provided with low / high speed switching hydraulic pipes 46L / 46R. Similarly, a steel pipe is used to connect the left and right traveling hydraulic motors ML and MR from the hydraulic pump P through the branch port 44 to the lubricating oil pipes 47 and 47L.
47R is also piped. These hydraulic pipes 45L ・ 45
R, 46 / 46L / 46R, and lubricating oil pipe 47/47
The L / 47R is also a steel pipe and its bent structure, and since it is located above the main frame 1 at the piping position, it has the same protection structure as the drive hydraulic pipe 43 (43L / 43R).

Another hydraulic piping structure will be described.
As shown in FIG. 14, from the hydraulic oil tank LT, the oil supply pipe 48
Is connected to a hydraulic case 14 for driving the hydraulic lift 14a to supply hydraulic oil as lubricating oil into the hydraulic case 14. Inside the hydraulic case 14, a hydraulic cylinder CY for driving the hydraulic lift 14a and a hydraulic valve V4 for controlling the hydraulic cylinder CY are internally provided.
In the conventional structure, the hydraulic valve V4 is disposed so as to be fitted into the transmission case TM disposed below the hydraulic valve V4 from above, and the lubricating oil in the transmission case TM and the hydraulic valve V4 are connected to the hydraulic valve V4. The hydraulic oil was shared. However, in this structure, the hydraulic pressure in the transmission case TM is increased by the amount supplied to the hydraulic valve V4. In the transmission case TM,
As described above, the transmission system gear mechanism from the input shaft 19 to the pump shaft 20 is provided, and the PTO shaft 21 from the input shaft 19 is provided.
A transmission gear mechanism is also provided, and if the lubricating oil pressure is high, the rotation efficiency of the gear deteriorates due to stirring resistance. Also,
Friction powder of gears is also liable to be generated, and these are hydraulic valves V4.
There is a risk that it may affect the operation of the hydraulic cylinder CY, that is, the operation of the hydraulic case 14a.

Therefore, in this embodiment, as shown in FIG. 4, the hydraulic case 14 is provided above the transmission case TM.
Is provided with a partition wall 42 that isolates it from the lower end of
The partition wall 42 is provided with a bent portion 42a so as to isolate the hydraulic valve V4 protruding toward the transmission case TM side.
Is formed. Then, by filling only the exclusive lubricating oil into the transmission case TM,
Since the hydraulic pressure is lowered and the gear efficiency is increased, clean hydraulic oil without friction powder mixed therein is supplied to the hydraulic case 14, so that the hydraulic valve V4 and the hydraulic cylinder CY are normally driven. is there.

As described above, the hydraulic oil CY is used to drive the hydraulic lift 14a in the hydraulic case 14 separated from the transmission case TM (see FIG. 9).
13 and 14, a suction pipe 49 is piped forward from the inside of the hydraulic case 14 along the left main frame 1L as shown in FIGS. 13 and 14.
In the above, the HS arranged opposite to the branch port 44
It is connected to the T charge pump P1 and the hydraulic lift charge pump P2.

From the hydraulic lift charge pump P2, the discharge pipe 50 is turned back and the discharge pipe 50 is connected to the hydraulic case 14 to supply pressure oil into the hydraulic case 14. On the other hand, HST
The discharge pipe 51 is connected to the oil filter F from the vehicle charge pump P1, the oil supply pipe 52 is connected to the traveling hydraulic pump P from the oil filter F, and the low / high speed switching control valve V2 of the hydraulic valve V (specifically, The oil supply pipe 53 is connected to the hydraulic pilot valve V2b) of FIG. In the hydraulic valve V, the brake valve V1 receives pressure oil from the low / high speed switching control valve V2.
It is branched and supplied through the branch supply path A shown in FIG. 8, and the brake valve V1 is supplied to the low / high speed switching control valve V2.
The oil is returned through an oil return passage B having an orifice Ba. A return oil pipe 54 is connected to an oil cooler C provided in the hood 4 in front of the main frame 1 from the low / high speed switching control valve V2 of the hydraulic valve V, and the return oil pipe 55 is supplied from the oil cooler C.
Is connected to the hydraulic oil tank LT.

The structure of the hydraulic circuit based on the above hydraulic system members and hydraulic pipes is shown in FIGS. 8 and 9.

In the crawler tractor of this embodiment having the above hydraulic mechanism, the interlocking mechanism of the negative brake will be described with reference to FIGS. The negative brake NB provided in the traveling hydraulic motor M is operated by depressing a brake pedal 9 provided in the front column 7. In this embodiment, the movable swash plate of the traveling hydraulic pump P is interlocked with the depression operation of the brake pedal 9 so that the negative brake NB is applied after the traveling hydraulic motor M is in the neutral state.

The brake pedal 9 has a boss 9a formed at the upper end on the right side of the front column 7 (left side when viewed from the front as shown in FIG. 6), and is pivotally supported on the rotating shaft 22 so as to be rotatable back and forth. And is urged by the spring 23 to the initial position X in FIG. The left side (right side in Fig. 6)
The clutch pedal 10 is suspended from the clutch pedal 10. The operation interlocking mechanism of the negative brake NB by depressing the brake pedal 9 will be described. The brake pedal 9
A wire connecting plate 9c is projectingly provided in the middle of the above, and the brake wire 24 is connected to the brake valve V1 of the hydraulic valve V from the wire connecting plate 9c. In FIG. 5, the play range of the brake pedal 9 is from the X position to the Y position, the brake wire 24 starts to be pushed from the Y position, and the brake pedal reaches the limit pedaling position Z.
The brake wire 24 continues to be pushed until the position is reached.

On the other hand, the operating state of the brake valve V2 by depressing the brake pedal 9 will be described with reference to FIG. Until the brake pedal 9 moves from the X position to the Y position, pressure oil is sent to both the negative brakes NB of the left and right traveling hydraulic motors ML and MR, and the negative brakes NB are disengaged against the springs biased to the braking side. Hold in braking position. Then, when the brake pedal 9 is stepped from the Y position to the Z position, the brake valve V2 is set to the negative brake N.
Remove the pressure oil from B and use the spring force to negative brake N
Although B is pressed to the drive wheel 2 to operate to a braking position, an orifice Ba is provided in the return oil passage B from the brake valve V2 so that the brake pedal 9 reaches the Z position for a while. The process of draining oil from the negative brake NB continues, and the braking state is not immediately established. That is, even if the brake pedal 9 is suddenly depressed to the Z position, the braking is not immediately performed.

Next, the interlocking mechanism of the movable swash plate of the hydraulic pump P by depressing the brake pedal 9 will be described.
Pivot portion 9 protruding from the boss portion 9a of the brake pedal 9.
The upper end of the brake connecting rod 25 is pivotally connected to b. A lower end of the brake connecting rod 25 has a horizontal rotary shaft 26.
It is pivotally connected to the upper end of the brake link 26 pivotally supported by a, and the lower end of the brake link 26 is pivotally supported in the two long holes 27a and 27a of the two sliding links 27 and 27. doing. On the other hand, from the base end of the main transmission lever 13 pivotally supported in the rear part of the cabin 6 (side of the seat 12) so as to be rotatable back and forth, to the hydraulic pump operation lever 28 pivotally supported by the steering gear box SB, The main transmission lever operation link 29 is pivotally connected so that the hydraulic pump operation lever 28 is interlocked with the rotation operation of the main transmission lever 13.

The left and right traveling hydraulic pumps PL and PR of the traveling hydraulic pump P are respectively provided with swash plate operating hydraulic valves V4L and V4R shown in FIG. 8 in order to positionally operate the movable swash plate. ing. Movable swash plate operation levers 33L and 33R are attached to the swash plate operation hydraulic valves V4L and V4R, respectively, and the valve control of the swash plate operation hydraulic valves V4L and V4R is performed by the rotation operation thereof. It is supposed to be done. By the rotation, the links 30 and 31 are pivotally connected to the left and right at the rear end of the steering gear box SB as shown in FIGS.
From 31, operation rods 32L and 32R (generally 32) are connected to movable swash plate operation levers 33L and 33R (generally 33) in the traveling hydraulic pump P, respectively. In this way, when the main shift lever 13 is rotated,
The movable swash plate operation lever 3 is linked with the links 30 to 32.
Rotate 3L / 33R to drive each traveling hydraulic pump PL / P
Set the R movable swash plate to the position set by the main shift lever 13 (for example, high speed forward position or low speed reverse position)
It is.

The other ends of the two sliding links 27, 27 are pivotally connected to both ends of the hydraulic pump operating lever 28, respectively. When the brake pedal 9 is depressed from the Y position to the Z position, both sliding links 27, 27 move via the brake connecting rod 24 and the brake link 26,
As a result, the hydraulic pump operating lever 28 rotates. By rotating the hydraulic pump operating lever 28 based on the stepping operation of the brake pedal 9, the left and right links 30.
1 rotates and pushes and pulls the left and right operation rods 32L and 32R to bring both movable swash plate operation levers 33L and 33R to the neutral position, that is, the movable swash plate to the neutral position.
On the other hand, even if the main speed change lever 13 is manually operated to move the main speed change lever operation link 29 and the hydraulic pump operation lever 28, due to the configuration of the elongated holes 27a of the both sliding links 27, The sliding link 27 only slides, and the brake link 26 and the brake connecting rod 25 do not operate, that is, the brake pedal 9 also does not operate. Therefore, there is no problem that the negative brake NB is applied by manual operation of the main transmission lever 13.

With the above configuration, when the brake pedal 9 is stepped on, the traveling hydraulic motor M is forcibly controlled to a low speed by the movement of the movable swash plate of the traveling hydraulic pump P (for example, the traveling hydraulic motor). If M is in the normal rotation state, the movable swash plate moves to the reverse rotation side, and if it is in the reverse rotation state, the movable swash plate moves to the forward rotation side.) That is, the brake is applied by the rotation control of the traveling hydraulic motor M. Then, after the traveling hydraulic motor M is in a neutral state, that is, a state in which there is no rotational force, the negative brake NB is braked. Since the negative brake NB is applied in this state, the wear of the brake is greatly reduced.

Finally, a low speed control mechanism during the spin turn of the steering mechanism will be described with reference to FIGS. 5 to 9. In the crawler tractor of this embodiment, the traveling portion is a crawler traveling device, which is rotated by a single round handle 8. The steering mechanism will be described. First, the steering shaft 3 extending from the steering wheel 8 is provided.
4 is connected to the steering transmission shafts 35 and 36 in the front column 7 via a universal joint, and the steering transmission shaft 36 is inserted into the steering gear box SB, and depending on its rotational position, Among the left and right traveling hydraulic pumps PL, PR, the movable swash plate for supplying pressure oil to the traveling hydraulic motor M on the turning side is moved to the traveling hydraulic pump P so as to move to the deceleration side in inverse proportion to the steering angle. The link mechanisms 30, 31, 32 are operated.
For example, when turning right, the movable swash plate of the right hydraulic pump PL is moved to the deceleration side. Then, when a certain turning angle is reached (in the present embodiment, the entire turning angle of the handle is set to 360 ° and the turning angle is set to around 180 °), the vehicle is in the neutral position, and when turning right, The hydraulic pump PL is stopped, and only the left drive wheel is driven to turn.

The spin turn further rotates the traveling hydraulic motor M on the turning side in the reverse direction.
Conventionally, the spin turn was selected by operating the switch that was attached to the steering operation device, but the running hydraulic motor on the turning side naturally rotates in reverse due to the turning angle of the steering wheel The movable swash plate of the hydraulic pump is controlled in posture. In the present embodiment, 180 (the turning side hydraulic motor M is in a neutral state).
° If the handle is turned over, the movable swash plate of the traveling hydraulic pump that supplies pressure oil to the traveling hydraulic motor on the side that is turned is set to the reverse rotation position. At this steering wheel turning angle, the movable swash plate of the variable displacement traveling hydraulic motor M is simultaneously switched to the low speed drive position, that is, the low / high speed switching valve V3 shown in FIG. 8 is switched to the low speed position. In addition, the handle 8 is set to the spin turn setting angle (1
80 °) or more and still turning, the amount of pressure oil supplied to the hydraulic motor M on the turning side that rotates in reverse increases in proportion to the increase in the cutting angle, that is, the reverse rotation speed on the turning side. Is increasing.

As described above, the switching control of the low / high speed switching valve V3 is performed by the low / high speed switching control valve V2 of the hydraulic valve V. The low / high speed switching control valve V2 is an electromagnetic valve V2.
a and the hydraulic pilot valve V2b, the hydraulic pilot valve V2a is switched by switching the electromagnetic valve V2a.
b pilot pressure oil switching control is performed to control the hydraulic pipes 19 and 19L from the hydraulic pilot valve V2b to the low and high speed switching valves V3 and V3 of the left and right traveling hydraulic pumps ML and MR.
The direction of pressure oil circulation of 19R is switched. The state of the hydraulic circuit shown in FIG. 8 is when the electromagnetic valve V2a is OFF, and the hydraulic pilot valve V2b is in a state where no pilot pressure is applied to the hydraulic pipes 19, 19L, 19R.
Pilot pressure oil is drained from the
3. V3 is in the low speed state, and the movable swash plates of the left and right traveling hydraulic motors ML and MR are in the low speed position. If the electromagnetic valve V2a is turned on, the hydraulic pilot valve V
The pilot pressure is applied to 2b and the low / high speed switching valves V3 and V3, and the movable swash plates of the left and right traveling hydraulic motors ML and MR are set to the high speed position.

Therefore, regarding the relationship between the handle 8 and the electromagnetic valve V2a, when the handle turning angle is less than the spin turn set angle (180 °), the electromagnetic valve V2a is turned on.
In this state, the electromagnetic valve V2a is set to the OFF state when the cut angle becomes equal to or larger than the spin turn set angle. Electromagnetic valve V2a that works with this steering angle
The switching control mechanism will be described with reference to FIGS. 5 to 9.

On the upper surface of the steering gear box SB,
As shown in FIG. 7, the low speed switching control valve V2 (electromagnetic valve V2a / hydraulic pilot valve V2b) below the hydraulic valve V is disposed on the right side. In the center of the upper surface of the steering gear box SB, a bearing 38 into which the steering transmission shaft 36 is fitted is loosely fitted in a hole at the center of the cam 39. A half circumference of the center hole of the cam 39 is expanded to form a groove 39c between the outer circumference of the bearing 38 and the steering transmission shaft 36 in the groove 39c.
The pin 37 fixed to the above is inserted. Also, the cam 39
In the outer peripheral portion, half is a short diameter outer peripheral portion 39a and the other half is a long diameter outer peripheral portion 39b. Further, a switch 41 for switching the electromagnetic valve V2a is arranged near the cam 39 on the upper surface of the steering gear box SB, and a switch pusher protruding from the switch 41 for expansion and contraction. Connect the end of 41a to the end of the link 40,
A rotation fulcrum 40a is provided at the other end of the link 40. The cam roller 4 is provided in the middle of the link 40.
0b is pivotally supported and pressed against the outer peripheral portion of the cam 39 by a spring force.

In such a cam structure, when the steering wheel turning angle is less than the spin turn setting angle, the pin 37 protruding from the steering transmission shaft 36 has the groove 37.
9c is freely moved, and the cam 39 is in a state in which the short diameter outer peripheral portion 39a is pressed against the cam roller 40b, and the switch pressing member 41a of the switch 41 is in the contracted state and the electromagnetic valve. V2a is in the ON state. That is,
The low / high speed switching valve V3 of the traveling hydraulic motor M is fixed at the high speed position.

When the cutting angle reaches the spin turn setting angle of 180 °, the pin 37 presses against the end of the groove 39c, and when the handle 8 is further cut, the pin 3
7, the cam 39 is pushed and rotated, and the long diameter outer peripheral portion 39b comes into contact with the cam roller 40b. In this state, the link 40 provided with the cam roller 40b is pushed and rotated by the long diameter outer peripheral portion 39b, and the switch pusher 41a of the switch 41 is pulled to be in an extended state. Therefore, the electromagnetic valve V2a is turned off, and the low / high speed switching valve V3 of the traveling hydraulic motor M is fixed at the low speed position.

In this way, the crawler tractor of this embodiment naturally has a spin-turn state when the steering wheel has a large turning angle, which enables a small turn, and a low-speed state which improves the turning stability. Is there.

[0045]

Since the present invention is constructed as described above for the hydraulic mechanism of the traveling vehicle, it has the following effects. First, since the negative brake is constructed as described in claim 1, the negative brake is braked after the pressure oil supply from the hydraulic pump to the hydraulic motor in the HST is stopped, that is, there is no axle rotation force. Since the negative brake is applied in this state, it is possible to reduce the wear of the brake plate and secure a brake device having long-term durability. Also, until the negative brake is applied, the hydraulic motor is rotated to the deceleration side by the pressure oil supply from the hydraulic pump to control the braking in advance, so the braking feeling is good and there is no old braking feeling. Wear can be further reduced.

Further, since it is configured as described in claim 2,
When the spin-turning state naturally occurs only by turning the steering device, the traveling speed becomes low, and turning stability can be secured without the need for complicated switch operation.

Further, as described in claim 3, by connecting the hydraulic pump to the transmission case instead of the engine output side, the hydraulic pump is integrated with the transmission case fixed to the frame, and the hydraulic motor is fixed to the frame. Since it is installed, the piping distance from the hydraulic pump to the hydraulic motor does not change. Therefore, the hydraulic pipe from the hydraulic pump to the hydraulic motor does not need to be flexible, and a steel pipe with high strength can be used. It can be used, the piping height can be increased, the minimum ground clearance of the vehicle can be increased, and it can run on rough terrain. Further, since the hydraulic pump is arranged in the front part of the transmission case, the piping distance to the hydraulic motor can be made relatively short.

Further, according to the present invention, the lubricating oil in the transmission case can be made independent of the hydraulic oil supplied into the case of the hydraulic drive system.
In the transmission case, low pressure of lubricating oil can be realized, gear stirring resistance can be reduced, gear efficiency can be improved, and in the hydraulic drive device, gear abrasion powder generated in the transmission case does not enter. ,
Good hydraulic drive can be secured.

[Brief description of drawings]

FIG. 1 is an overall side view of a crawler tractor.

FIG. 2 is a side view showing a hydraulic drive system and a frame structure.

FIG. 3 is a plan view of the same.

FIG. 4 is a side view of a hydraulic drive system.

FIG. 5 is a side view showing a link mechanism for steering and a brake.

FIG. 6 is a front view of the same.

FIG. 7 is a plan view of a steering gear box SB.

FIG. 8 is a hydraulic traveling drive system circuit diagram.

FIG. 9 is a circuit diagram of a hydraulic lift drive system.

10 is a plan view showing a piping structure for a traveling hydraulic motor M. FIG.

FIG. 11 is a side view of the same.

FIG. 12 is a front view of the same.

FIG. 13 is a plan view showing a traveling hydraulic pump P, a hydraulic valve V, and piping for supplying hydraulic oil to the hydraulic case 14.

FIG. 14 is a side view of the same.

[Explanation of symbols]

 P Travel hydraulic pump M Travel hydraulic motor NB Negative brake TM Transmission case SB Steering gear box V Hydraulic valve V1 Brake valve V2 Low / high speed switching control valve V2a Electromagnetic valve V2b Hydraulic pilot valve V3 Low / high speed switching valve V4 Swash plate operating hydraulic valve LT Hydraulic oil tank 8 Handle 9 Brake pedal 13 Main shift lever 14 Hydraulic case 14a Hydraulic lift 24 Brake wire 25 Brake connecting rod 26 Brake link 27 Sliding link 27a Long hole 28 Hydraulic pump operating lever 29 Main shift lever operating link 32 Operation Rod 33 Movable swash plate operation lever 36 Steering shaft 37 Pin 39 Cam 40 Link 40b Cam roller 41 Changeover switch 42 Partition wall 43 Drive hydraulic pipe 45L・ 45R hydraulic pipe for brake 46 ・ 46L ・ 46R low speed hydraulic pipe for switching

Claims (4)

[Claims] 1. An operating mechanism of a negative type brake device for applying a load to an axle rotation attached to a hydraulic motor in an HST drive type traveling vehicle to brake the hydraulic pump, in association with a braking operation by the operating mechanism. A hydraulic mechanism for a traveling vehicle, comprising: a mechanism for moving the swash plate to a neutral position; and a mechanism for causing the negative brake device to perform a braking operation after the time required for the movable swash plate to reach the neutral position has elapsed. . 2. The two traveling devices are independently equipped with the HST, and the HST for each traveling device is provided by the turning operation of one steering device.
In the hydraulic mechanism having a mechanism for controlling the discharge of the hydraulic pump, stopping the discharge, and controlling the discharge direction, and making the discharge directions from the two hydraulic pumps opposite to each other when the turning operation amount of the steering device is equal to or more than a certain amount. , When the turning operation amount of the steering device is such that the discharge direction from each hydraulic pump is the opposite direction, both H
A hydraulic mechanism for a traveling vehicle, which is provided with a mechanism for switching a variable displacement hydraulic motor in ST to a low speed drive. 3. An HST drive type traveling vehicle, wherein a traveling hydraulic pump is connected to a front portion of a transmission case arranged from an engine output shaft via a transmission shaft, in a traveling vehicle hydraulic mechanism. . 4. A traveling vehicle hydraulic system having a hydraulic drive device, wherein a case of the hydraulic drive device is disposed above a transmission case, and a partition wall is provided between both cases.