JPH06100278B2 - Shifting structure of work vehicle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to the structure of a gear shift operation system in a work vehicle equipped with a hydrostatic continuously variable transmission for traveling.

[Conventional technology]

As described above, in the work vehicle equipped with the hydrostatic stepless transmission, the operation shaft for changing the swash plate angle of the hydrostatic stepless transmission and the speed change pedal are mechanically linked directly by a rod or the like. There are many things. In this case, the swash plate of the hydrostatic continuously variable transmission is subjected to the force of returning to the neutral position due to the discharge reaction force of the hydraulic pump, and therefore the shift pedal must be operated against this force. The operation is relatively heavy.

Therefore, there has been proposed a linkage mechanism configured to electrically detect the operation position of the shift pedal with a potentiometer or the like, and change the swash plate angle of the hydrostatic continuously variable transmission by the motor based on the detected position. .

[Problems to be Solved by the Invention]

A work vehicle such as an agricultural tractor travels and performs work under adverse conditions such as an unpaved road or a weak field, so that mud, soil, water, and the like tend to adhere to the suspension. Therefore, under such a bad condition, it is difficult to say that the electric linkage mechanism as described above has sufficient reliability and durability, and the malfunction probability is often relatively high.

The present invention provides a linkage mechanism which can easily change the swash plate angle of a hydrostatic stepless transmission in a gearshift operation structure of a work vehicle equipped with a hydrostatic stepless transmission for traveling, with reliability and durability. It is intended to be composed of high ones.

[Means for Solving the Problems]

The feature of the present invention resides in the following structure in the shift operation structure of the work vehicle as described above.

The operation arm is fixed to the operation shaft for changing the swash plate angle in the hydrostatic continuously variable transmission for traveling, the cylinder case of the hydraulic cylinder is directly linked to the operation arm, and the piston rod is projected from both sides of the cylinder case. Then, both ends of the piston rod are connected and fixed to the casing of the hydrostatic continuously variable transmission, and the control valve for supplying and discharging hydraulic oil to and from the hydraulic cylinder has a spool axis parallel to the piston rod axis. Is fixed to the cylinder case, and the spool of the control valve and the manual operation tool are interlockingly connected so that the cylinder case moves along the piston rod so as to follow the displacement of the spool.

[Work]

(I) When configured as in the present invention, as shown in, for example, FIGS. 1 and 2, the control valve (15) is operated by the operation of the manual operation tool (17).
When the spool (16) is operated, hydraulic oil is supplied to and discharged from the hydraulic cylinder (11) based on the operation, and the spool (16) is operated along the fixed piston rod (14). Then, the cylinder case (12) follows and moves, and the operation shaft (9) of the hydrostatic continuously variable transmission (6) is operated via the operation arm (10).

(Ii) In the structure of the present invention, as shown in FIG. 1, for example, since both ends of the piston rod (14) are connected and fixed to the casing (5), the piston cylinder (11) is used by the piston rod (14). The cylinder case (12), the control valve (15), and the like are supported. As a result, the piston rod (14) is also used as a supporting member for the hydraulic cylinder (11) and the like for the casing (5), and the hydraulic cylinder (11).
A dedicated support member such as is unnecessary.

(Iii) In the present invention, as shown in FIGS. 1 and 3, for example, the operation arm (10) of the hydrostatic continuously variable transmission (6) is directly attached to the cylinder case (12) of the hydraulic cylinder (11). Since it is linked to the cylinder case (12), a dedicated linking member such as a linking rod or a wire for linking the cylinder case (12) and the operating arm (10) of the hydrostatic continuously variable transmission (6) is unnecessary.

〔The invention's effect〕

As described above, by using the hydraulic linkage mechanism as the linkage mechanism between the manual operation tool such as the operation pedal and the operation shaft of the hydrostatic continuously variable transmission, compared to the electrical linkage mechanism, It was possible to improve the reliability and durability of the gear shift operation structure.

By using the piston rod as a supporting member such as a hydraulic cylinder for the casing, a dedicated supporting member such as a hydraulic cylinder becomes unnecessary, and the operating arm of the hydrostatic continuously variable transmission is directly attached to the cylinder case. Since a dedicated linking member is not required by linking with, the structure can be simplified and the weight can be reduced.

〔Example〕

Hereinafter, an agricultural tractor which is one of the embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 4, an engine (3) is provided at the front of the airframe supported by front wheels (1) and rear wheels (2), a control section (4) is provided at the center of the airframe, and a mission case (5) is provided at the rear of the airframe. ) (Corresponding to a casing) is arranged to constitute a four-wheel drive type agricultural tractor.

Next, the mission case (5) will be described. Fourth
As shown in the drawings and FIG. 1, a front wheel transmission (not shown)
Front case (5a) for housing the interior, middle case (5b) for housing the hydrostatic stepless transmission (6), rear case for housing the gear type auxiliary transmission and differential mechanism (above, not shown) The mission case (5) is configured by connecting (5c) in order from the front side of the airframe.

The power from the engine (3) is transmitted from the first transmission shaft (7) to the hydrostatic stepless transmission (6) in the middle case (5b), and is transferred from the hydrostatic stepless transmission (6) to the rear case. It is transmitted to the rear wheel (2) via the auxiliary transmission in (5c). The power branched from the subtransmission is transmitted to the front wheel transmission in the front case (5a) for gear change operation, and is transmitted to the front wheels (1) via the second transmission shaft (13).

Next, the structure of the operation system of the hydrostatic continuously variable transmission (6) will be described. As shown in FIGS. 1 and 3, the operating shaft (9) projects laterally from the swash plate (8) of the hydrostatic continuously variable transmission (6), and the plate material is attached to the operating shaft (9). A bent bifurcated operation arm (10) is fixed. A hydraulic cylinder (11) is provided for the operation arm (10), and the hydraulic cylinder (11) includes a cylinder case (12) having a first oil chamber (12a) and a second oil chamber (12b), It is composed of a piston rod (14). The piston rod (14) projects from both ends of the cylinder case (12), and both ends of the piston rod (14) are connected to the side walls of the front case (5a) and the middle case (5b) with bolts (24). ,
The front end of the operation arm (10) is inserted between two convex portions (12c) provided on each of the front and back side wall portions of the cylinder case (12).

At the bottom of the cylinder case (12) spool type control valve (1
5) is in the axial direction of the spool (16) and the piston rod (1
It is integrally formed so that the axial direction of 4) is parallel to it, and the spool (16) and the speed change pedal (17) (corresponding to a manual operation tool) are mechanically connected via a linkage mechanism (18). They are linked together.

Next, operations of the speed change pedal (17), the control valve (15) and the hydraulic cylinder (11) will be described. As shown in FIG. 1, the hydraulic oil branched from the charge pump (19) for replenishing the insufficient hydraulic oil in the hydrostatic continuously variable transmission (6) is the pump port (20) of the control valve (15). Is being supplied to. First
When the transmission pedal (17) is stepped forward from the neutral stop state as shown in FIG. 2, the spool (16) of the control valve (15) is pulled out forward through the linkage mechanism (18). In such a state, the pump port (20) and the first port (21) communicate with each other, the working oil is supplied to the first oil chamber (12a) of the cylinder case (12), and the second oil chamber (12b). ) Is drained from the 2nd port (22) through the drain port (23), and the cylinder case (12) and control valve (15) move to the right in the drawing. , The operating shaft (9) and the swash plate (8) are operated toward the forward acceleration side.

Conversely, when the speed change pedal (17) is stepped backward, the spool (16) is pushed into the control valve (15), the pump port (20) and the second port (22) are in communication with each other, and the hydraulic oil is transferred to the cylinder. It is supplied to the second oil chamber (12b) of the case (12),
The hydraulic oil in the first oil chamber (12a) flows from the first port (21) to the internal oil passage (16a) of the spool (16) and the drain port (2
3) The oil is drained through. As a result, the cylinder case (12) and the control valve (15) move to the left side of the paper surface of FIG. 1, and the operation shaft (9) and the swash plate (8) are operated to the backward speed increasing side. Of.

With the above structure, the bolt (24) connecting the piston rod (14) of the hydraulic cylinder (11) to the front case (5a) and the middle case (5b) is removed, and the spool (16) of the control valve (15) is removed. ) And the linkage mechanism (18) are disconnected, and the control valve (15)
The hydraulic cylinder (11) and control valve (15) can be easily removed as one unit by removing the pipes (25) and (26) connected to the pump port (20) and the drain port (23) of be able to.

In this case, the operation arm (10) on the side of the hydrostatic continuously variable transmission (6) and the cylinder case (12) are arranged between the pair of convex portions (12c) of the cylinder case (12). Since the tip of the cylinder is inserted, the operation arm (10) can be connected to the cylinder case (1
2) can be easily removed. Further, when the hydraulic cylinder (11) and the control valve (15) are removed as one unit as described above, the operation shaft (9) and the speed change pedal (17) of the hydrostatic continuously variable transmission (6) are It becomes relatively easy to change to a mechanically directly coupled type.

It should be noted that reference numerals are added to the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

The drawings show an embodiment of a shift operation structure for a work vehicle according to the present invention. Fig. 1 is a vertical sectional side view showing structures of a hydraulic cylinder and a control valve in a neutral stop state, and Fig. 2 is a state shown in Fig. 1. Is a vertical sectional side view showing the state of the hydraulic cylinder and the control valve when the transmission pedal is stepped forward from the front, FIG. 3 is a vertical sectional front view near the swash plate in the hydrostatic stepless transmission, and FIG. It is the whole side view. (5) …… Casing, (6) …… Hydraulic hydraulic type continuously variable transmission, (9) …… Operating shaft, (10) …… Operating arm, (11)
…… Hydraulic cylinder, (12) …… Cylinder case, (14)
...... Piston rod, (15) …… Control valve, (16) …… Spool.

Claims (1)

[Claims] 1. An operating arm (10) on an operating shaft (9) for changing a swash plate angle in a hydrostatic continuously variable transmission (6) for traveling.
Secure the cylinder case (1) of the hydraulic cylinder (11).
2) is directly linked to the operation arm (10), the piston rod (14) is projected from both sides of the cylinder case (12), and both ends of the piston rod (14) are connected to the hydrostatic stepless. A control valve (15) for connecting and fixing to a casing (5) of a transmission (6) and for supplying / discharging hydraulic oil to / from the hydraulic cylinder (11) has a shaft center of a spool (16) connected to the piston rod (14). ) Is fixed to the cylinder case (12) so that it is parallel to the shaft center, and the spool (16) of the control valve (15) and the manual operation tool (17) are interlockingly connected to each other to form the spool (1
6) Cylinder case (12) to follow the displacement of 6)
Is a work vehicle gear shift operation structure configured to move along the piston rod (14).