JP2593751Y2 - Shifting structure of work vehicle - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a hydrostatic stepless transmission in which a cylinder case of a hydraulic cylinder is interlocked to a shift operation shaft of a traveling hydrostatic continuously variable transmission, and a piston rod of the hydraulic cylinder is connected to a hydrostatic stepless transmission. The control valve for the hydraulic cylinder is fixed to the cylinder case so that the spool axis is parallel to the cylinder axis, and the cylinder case follows the hydraulic operation with the displacement of the spool. The present invention relates to a shift operation structure of a work vehicle configured to be displaced.

[0002]

2. Description of the Related Art Conventionally, in the above-described shift operation structure of a working vehicle, both sides of a piston rod are conventionally connected and fixed to a casing of a hydrostatic continuously variable transmission as shown in Japanese Utility Model Laid-Open No. 3-7570. In addition, there has been a configuration in which a cylinder case is interlockedly connected to a shift operation shaft, and a spring for returning a neutral position to the shift operation shaft is interposed in the middle of a link mechanism between the operation pedal and the spool.

[0003]

However, in the above-mentioned conventional structure, when, for example, an abnormality occurs in the hydraulic system and the pressure oil is not supplied, the neutral position return spring operates the spool of the control valve. Since the system is interposed in the system, the spool is restored to the neutral control position, but the hydraulic cylinder is not driven.Therefore, the gearshift operating shaft cannot be restored to the neutral position, resulting in an unstable state. is there. Also, since the spring is configured to be exposed to the outside,
There is a possibility that mud or the like may be scattered and solidified during the operation and hinder smooth operation, and there is room for improvement. The purpose of the present invention is to eliminate the above-mentioned disadvantages.

[0004]

The characteristic structure of the present invention is that a cylinder case of a hydraulic cylinder is interlocked to a shift operation shaft of a hydrostatic continuously variable transmission for traveling, and a piston rod of the hydraulic cylinder is statically moved. The control valve for the hydraulic cylinder is fixed to the cylinder case so that the spool axis is parallel to the cylinder axis, and the cylinder case is hydraulically operated with the displacement of the spool. In the shift operation structure of the working vehicle configured to be displaced by following, the restoring coil spring for returning the shift operation shaft of the hydrostatic continuously variable transmission to the neutral position is fitted to the shaft end of the piston rod. A spring receiving member that receives one end of the coil spring and a spring receiving member that receives the other end of the coil spring are disposed inside the cylinder case, and extend the coil spring. Relative to the shaft end so as to be relatively slidable in the direction in which the coil spring is reduced, and both spring receiving members are relatively immovable in the direction in which the coil spring extends, and A neutral return mechanism that biases the cylinder case and the piston rod to return to a predetermined relative position is constructed by mounting the cylinder case and the piston rod to a predetermined relative position by being housed in the cylinder case so as to be relatively slidable in the reduction direction of the coil spring. That is, a special color member is interposed between the case and the case.

[0005]

Since the neutral restoring spring is interposed between the cylinder case and the piston rod, and the piston rod is connected and fixed to the casing of the hydrostatic continuously variable transmission,
Even if pressure oil is not supplied due to an abnormality in the hydraulic system, the cylinder case, that is, the speed change operation shaft is always restored to the neutral position by the biasing force of the spring. or,
Since the spring is structured to be installed inside the cylinder case, mud and the like do not scatter and accumulate.

A neutral return mechanism for restoring the shift operation shaft to a neutral position is provided by disposing spring receiving members positioned at both ends of a coil spring externally fitted to the piston rod, respectively, at the piston rod and the cylinder case. With this configuration, a function of returning to a predetermined position positioned by the two spring receiving members, that is, a position where the speed change operation shaft is neutralized, regardless of whether the piston rod is operated in any axial direction. Since this means is configured by fitting the coil spring to the piston rod, it can be installed in the cylinder case in a compact space-saving state.

Further, since the coil spring for restoring the neutral position is positioned on the cylinder case via not only the spring receiving members at both ends but also the collar member, the size of the spring receiving portion inside the case is strictly set. There is no need to adjust the size of the collar member and set it. Therefore, flexibility is effective in the cylinder case shape, and
Normal dimensional accuracy can be used, and the length can be freely adjusted by replacing a collar member or the like, and the neutral position can be changed.

[0008]

Therefore, even if an abnormality occurs in the hydraulic system and the operation of the hydraulic cylinder becomes impossible, the shift operation shaft is always returned to the neutral position, which is contrary to the intention of the operator. As a result, adverse effects such as the hydrostatic stepless transmission maintaining the traveling speed change state are eliminated, and the spring for returning to neutral can maintain smooth operation for a long period of time. In addition, the neutral return mechanism can be made compact at the piston rod end by a simple and inexpensive means of interposing a separate collar member, and the neutral position can be securely changed without changing the neutral position, and the neutral position can be adjusted. There is an advantage that the object can be achieved while allowing the user to freely perform settings and changes.

[0009]

Embodiments will be described below with reference to the drawings. FIG.
Fig. 2 shows a shift operation system of a combine equipped with a hydrostatic continuously variable transmission. In this speed change operation system, a hydrostatic stepless transmission H is interposed in the traveling system of the fuselage.
Is configured to rotate the trunnion shaft 1 [shift operation shaft] via a hydraulic servo mechanism to change the vehicle running speed.

More specifically, a turning end of an operating arm 2 connected to the trunnion shaft 1 so as to be rotatable integrally is engaged with an intermediate portion of a front and rear locking member 4 formed on a cylinder case 3a of the operating hydraulic cylinder 3. The operation arm 2 is linked so as to rotate in conjunction with the movement of the cylinder case 3a in the axial direction. One end of the piston rod 3b of the hydraulic cylinder 3 is fixed to the casing 5 of the continuously variable transmission H and is supported in a cantilever manner. The valve body 6a of the control valve 6 of the hydraulic cylinder 3 is integrally connected and fixed to the cylinder case 3a so that its spool axis is parallel to the cylinder axis. The case 3a is configured to follow and displace.

That is, as shown in FIG.
Is slid from the neutral position N to the forward side F or the reverse side R by the operation of the operation lever 7 provided in the aircraft control section, and accordingly, the continuously variable transmission supplied from the pressure oil port P1 of the control valve 6 The pressure oil from the charge pump 8 to the device H is supplied to either the left or right hydraulic chamber R of the hydraulic cylinder 3.
1 and R2, and the cylinder case 3a is relatively driven to move toward the pressure oil supply oil chamber.

The oil from the other oil chamber to which the pressure oil is not supplied is drained into the casing 5 of the continuously variable transmission H through the drain ports P2 and P3. The hydraulic piping is designed to be short. In addition, the spool 6b of the control valve 6 is configured to always return to the neutral control position by the coil spring 9 interposed between the spool 6b and the valve body 6a.

As shown in FIG. 3, a connection support member 10 for connecting the piston rod 3b to the casing 5 is fixedly connected to the casing 5 by a screw portion 11 and a lock nut 12, and is biased with respect to the screw portion 11. The end of the piston rod 3b is inserted into the shaft portion 13 having the centered shaft core so as to prevent the piston rod 3b from coming off, and is connected thereto. Then, loosen the lock nut 12 and rotate the hexagonal shaft portion 14 with a tool,
The lock nut 12 is tightened and fixed again, so that the piston rod 3b can be finely adjusted to a neutral position in the axial direction.

As shown in FIG. 1, the restoring coil spring 15 for returning the trunnion shaft 1 to the neutral position is connected to the cylinder case 3a.
The cylinder case 3a and the piston rod 3
b are interposed along the direction of relative sliding movement. That is, a small-diameter shaft (an example of a shaft end) 16 is formed on the free end side of the piston rod 3b, and a spring 15 is externally fitted to the small-diameter shaft 16, and one end of the spring 15 is connected to the piston rod 3b. The free end side shaft end is received and supported by a spring receiving member 18 which is prevented from coming off by a stopper 17, and the other end is received and supported by a shaft step 19 via a washer (an example of a spring receiving member) 20. is there. The washer 20 is externally slidably fitted to the small diameter shaft portion 16, and the washer 20 and the oil chamber forming boss 2 of the cylinder case 3 a are provided.
A collar member 23 slidably fitted to the large-diameter shaft portion 22 of the piston rod 3b is interposed therebetween.

That is, by providing the coil spring 15 and the collar member 23 which is fitted over the piston rod 3b so as to limit the range of action in which the coil spring 15 biases the cylinder case 3a toward the neutral position, etc. A neutral return mechanism for urging the cylinder case 3a and the piston rod 3b to return to a predetermined relative position is configured.

The structure of the neutral return mechanism will be described in more detail. A spring receiving member 18 for receiving the left end of the coil spring 15 and a washer 20 for receiving the right end thereof are provided with a stopper 17 and a step portion 19 in the extending direction of the coil spring 15. Relative to the shaft end 16 so as to be relatively slidable in the direction in which the coil spring 15 is reduced, and the spring receiving member 18 and the washer 20 cannot be relatively moved in the direction in which the coil spring 15 extends, In addition, by being slidably mounted in the cylinder case 3a relative to the reduction direction of the coil spring 15,
The cylinder case 3a and the piston rod 3b are urged to return to a predetermined relative position. A dedicated collar member 23 is interposed between the washer 20 and the cylinder case 3a.

Therefore, in FIG.
When a moves relatively to the right from the neutral position with respect to the piston rod 3b, the coil spring 15 is retracted by the step portion 19 and the stopper 17, and when it moves to the left, the oil chamber of the cylinder case 3a is formed. The boss 21 is retracted by the washer 20 pressed by the collar member 23 via the collar member 23 and the stopper 17, and an urging force is always applied to return to the neutral state. In addition, the coil spring 15 always maintains the neutral restoring force on the trunnion shaft 1 even when the hydraulic oil is not supplied to the hydraulic cylinder 3.

In the claims of the utility model registration, reference numerals are written in order to facilitate comparison with the drawings, but the present invention is not limited to the configuration of the attached drawings by the entry.

[Brief description of the drawings]

FIG. 1 is a sectional view of a hydraulic cylinder and a control valve.

FIG. 2 is a side view of a speed change operation system.

FIG. 3 is a cross-sectional view of a connection support portion.

FIG. 4 is a hydraulic circuit diagram

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Speed change operation shaft 3 Hydraulic cylinder 3a Cylinder case 3b Piston rod 5 Casing 6 Control valve 6b Spool 15 Spring 16 Shaft end 18, 20 Spring receiving member 23 Collar member H Hydrostatic continuously variable transmission

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-214557 (JP, A) JP-A-1-156138 (JP, A) JP-A-2-31079 (JP, A) Jpn. 92501 (JP, U) Japanese Utility Model Hei 2-16852 (JP, U) Japanese Utility Model Hei 3-7570 (JP, U) Japanese Utility Model Sho 63-200690 (JP, U) Japanese Utility Model Sho 59-16549 (JP, Y2) (58) Field surveyed (Int. Cl. ⁶ , DB name) F16H 61/38-61/46

Claims (1)

(57) [Scope of request for utility model registration] 1. A hydraulic cylinder (3) having a cylinder case (3a) of a hydraulic cylinder (3) interlockingly connected to a shift operation shaft (1) of a hydrostatic continuously variable transmission (H) for traveling. The piston rod (3b) is connected and fixed to the casing (5) of the hydrostatic continuously variable transmission (H),
A control valve (6) for the hydraulic cylinder (3) is fixed to a cylinder case (3a) so that its spool axis is parallel to the cylinder axis, and the cylinder case (3a) is moved with the displacement of the spool (6b). Is a shift operation structure of a working vehicle configured to be displaced by hydraulic operation, comprising: a coil spring (15) for restoring the shift operation shaft (1) of the hydrostatic continuously variable transmission (H) to a neutral position. A spring receiving member which is disposed inside the cylinder case (3a) in a state of being fitted over the shaft end (16) of the piston rod (3b) and receiving one end of the coil spring (15).
(18) and the other end of the coil spring (15) is received.
A spring receiving member (20) is connected to the coil spring (15).
Cannot move relative to the extension direction, and
The shaft end is slidable relatively in the reduction direction of the shaft (15).
(16) and the two spring receiving members
(18) and (20) are extended by extending the coil spring (15).
The coil spring
(15) The syringe is slidable relative to the reduction direction.
By mounting the cylinder in the case (3a),
Predetermine the case (3a) and the piston rod (3b)
A neutral return mechanism that urges return to the relative position of
Further, one of the spring receiving member (20) and the cylinder
An exclusive collar member (23) is interposed between the case and the case (3a).
The gearshift operation structure of the mounted work vehicle.