JPH0522614B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is equipped with a hydraulic continuously variable transmission device, and a foot pedal for changing the speed of the continuously variable transmission device is biased to return to a neutral position. It concerns work vehicles.

[Conventional technology]

Regarding the above work vehicle, the present applicant has previously filed an application for the following technology.

That is, in the above-mentioned work vehicle, there is provided a friction holding mechanism that frictionally fixes the manual operation lever, which can be interlocked with the foot pedal and can be freely disengaged from the foot pedal, at any operating position, and a friction holding mechanism that locks the manual operation lever, which can be interlocked with the foot pedal and can be released from the interlocking, at any operating position; The company previously applied for a technology for a working vehicle that is equipped with a linking means for releasing the frictional hold of the holding mechanism. This work vehicle is equipped with a manual operation lever for a pedal lock that frictionally fixes the foot pedal at an arbitrary position, and by operating this lever, it resists the biasing force to return to the gear shift neutral position. Previous technology was devised so that a constant speed running state could be obtained without feeling fatigued (for example,
Compared to the agricultural vehicle (described in Publication No. 102438), constant speed driving can be achieved directly by operating the manual lever, so after setting the speed with the foot pedal, the speed is fixed by locking the pedal with the manual lever. It has features such as not having to go through the troublesome steps of doing so.

[Problem that the invention seeks to solve]

In the work vehicle according to the previous application, the frictional holding force for the manual operation lever is set to be almost constant over the entire range of acceleration/deceleration, so that the operator does not feel confused when operating the manual lever. It was hot. In other words, as the hydraulic continuously variable transmission is operated to increase speed, the reaction force causes the shift operation shaft (the swash plate support shaft, commonly called the trunnion shaft) to return to the shift neutral position. Because of the characteristic that the bias acts strongly, the operation force of the manual lever appears as a resultant force with the friction holding force, and the lever operation becomes heavier as the speed increases. As a result, for example, when women, girls, or beginners operate the manual lever for constant speed driving, they may feel confused because they cannot predict the operating force that will gradually increase, and may find it difficult to shift gears, or the resistance may become lighter. There were operational problems in that the vehicle would sometimes slow down too much.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a work vehicle that can maintain a constant operating force when operating a speed change lever within the speed change operation range.

[Means for solving problems]

In order to achieve the above object, the work vehicle according to the present invention is equipped with a hydraulic continuously variable traveling speed device,
The foot pedal for gear shifting of this continuously variable transmission is biased to return to the neutral gear position via a spring, and the manual operating lever is fixed by friction to a manual operating lever that can be interlocked with and disengaged from the foot pedal. a friction retention mechanism, and
The friction holding mechanism includes a lever-side friction member that operates integrally with the lever, a fixed-side friction member supported by a fixed portion so as to be in sliding contact with the lever over the entire shift operation range, and the fixed-side friction member as described above. Consists of a spring that presses and biases the lever side friction member,
Furthermore, in a work vehicle provided with a linking means for releasing friction retention of the friction retention mechanism in conjunction with a braking operation of a traveling brake operating tool, the hydraulic Against the biasing force of the continuously variable transmission itself to return to the neutral position,
The friction holding force of the friction holding mechanism decreases as the return urging force increases, so that the friction holding force due to the biasing action of the spring of the friction holding mechanism is increased on the deceleration side of the shift operation range of the lever. The characteristic configuration is that the speed is set to be smaller as the speed increases.

The functions and effects of this characteristic configuration are as follows.

[Effect]

In other words, the friction holding mechanism that frictionally fixes the manual operating lever is comprised of a lever-side friction member that operates integrally with the lever, and a stationary-side friction member that is supported by a fixed part so as to be in sliding contact over the entire shift operation range of the lever. , the fixed side friction member is constituted by a spring that presses and biases the lever side friction member, and the hydraulic continuously variable transmission itself shifts to a neutral position which increases with the speed change operation to the speed increasing side. With respect to the return urging force, as the return urging force increases, the friction holding force of the friction holding mechanism decreases.
The friction holding force due to the biasing action of the spring of the friction holding mechanism is set to be large in the deceleration side of the speed change operation range of the lever, and to be small in the speed increase side, so that In this case, the operating force, which is the resultant force of the biasing force for returning to the shift neutral position and the friction holding force, is set to a state where there is no large change over the operating range.

〔Effect of the invention〕

Therefore, the operating force of the manual operating lever does not change significantly throughout the entire shift operation range, so even beginners can perform accurate shift operations without being confused by the shift operation feeling.
We were able to resolve the problem of the vehicle running at an unreasonable speed.

〔Example〕

In this embodiment, a four-wheel drive agricultural tractor, which is an example of a working vehicle, will be described. See Figures 2 and 5. This tractor T transmits power from an engine E mounted at the front to the rear via an axial plunger type hydraulic continuously variable transmission H configured by hydraulically connecting a cylinder pump and a cylinder motor. The driving force is transmitted to the transmission case M, and the driving force is transmitted from the transmission case M to the front and rear tires 1 and 2. The hydraulic continuously variable transmission H
The pump is configured to change the speed by adjusting the discharge amount of the cylinder type pump by changing the angle of the swash plate, and a cam plate 4, which will be described later, is fixed to the end of the support shaft 3 of the swash plate that protrudes outside the housing. This cam plate 4 and tractor T
Shift operation pedal 6 attached to the side of the frame 5
Connect the triangular bracket 7 on the side with the rod 8,
The configuration is such that when the speed change pedal 6 is depressed forward or backward, a forward speed change state F and a reverse speed change state R can be obtained steplessly from the neutral position N.
The lower end side of the cam plate 4 is formed into an inverted V-shaped cam surface 4a when viewed from the side, and is pivoted about the horizontal axis X below the cam surface 4a, and is supported by a spring 14 on the side of the cam surface 4a. A lever arm 15 is provided which is biased to move, and a roller 16 attached to the free end of the lever arm 15 is brought into contact with the cam surface 4a, so that when no operating force is applied to the shift operation pedal 6, the swash plate is moved. The support shaft 3 is urged back to the neutral position N. Further, between the triangular bracket 7 and the frame 5 of the tractor T, there is provided a buffer damper 2 for preventing sudden depression of the speed change operation pedal 6.
3 has been erected.

In addition, in the illustrated tractor T, the lifting operation valve V of the lift arm 9 is fixed under the fender 10, so that the lift arm 9 at the rear of the fuselage can be raised and lowered from either the front or the rear of the fuselage. A first lever 11a and a second lever 11b near the steering handle are connected to the valve V via rods, respectively.

Tractor T with the above basic configuration,
In order to facilitate running at a constant speed, the following configuration has been added. See Figures 1 to 4.

The overall structure consists of a manual operating lever 12 that can be linked to and released from the shift pedal 6, a friction holding mechanism 13 that frictionally fixes the manual operating lever 12 at any operating position, and a brake operating tool for driving. It consists of a linking means 18 that releases the friction holding action of the friction holding mechanism 13 in conjunction with a braking operation by depressing a certain brake pedal 17, and each part thereof will be described in detail below.

The manual operation lever 12 is attached to a first pin shaft 19a supported by a frame 19.
A sleeve 12a inserted through the sleeve 9a, and a lever swing shaft 12b attached at right angles to this sleeve.
This allows for vertical and horizontal rocking displacement operations in the drawing of FIG. 4. Further, a triangular bracket 7 on the side of the speed change operation pedal 6 is attached to the first pin shaft 19a.
A gear shift operation piece 21 is connected to the manual operation lever 1 via a rod 20 and has a U-shaped groove for engaging and disengaging the manual operation lever 12.
It is inserted and supported so that it can swing relative to 2.
Reference numeral 12c in the drawings indicates a coil spring for biasing the manual operation lever 12 away from the shift operation piece 21, and reference numeral 22 indicates the engagement state between the manual operation lever 12 and the shift operation piece 21. This is a gear change guide plate that guides the manual operating lever 12 while holding the manual lever 12. When the manual lever 12 is operated along the groove 22a of this guide plate 22, the operating force is transmitted to the triangular bracket 7 and moves forward and backward. It has a configuration that allows the advancement speed to be obtained steplessly.

The friction holding mechanism 13 includes a manual operation lever 12
an arm member 13a fixed to the sleeve 12a to which the arm member 13a is attached;
A friction member 13b as a lever-side friction member is attached replaceably to the lever side, and a friction member 13b is swingable around a second pin shaft 19b supported by the frame 19, and is biased to move toward the friction member 13b by a spring 13c. The friction plate 13d as a stationary side friction member is provided with a substantially arc-shaped friction plate 13d attached thereto. Therefore, with this configuration, the manual operation lever 12
is held by friction at any shift operation position, and the speed can be set by manual operation against the holding force.

Further, the linking means 18 includes an L-shaped link 18a.
and two rod members 18b and 18c arranged via this link 18a, connecting the brake pedal 17 and the friction plate 13d. With this configuration, when the brake pedal 17 is depressed for braking, the friction plate 13d swings around the second pin shaft 19b and separates from the friction member 13b, and as a result,
The manual operation lever 12, whose friction holding effect has been released at the shift position, returns to the neutral position N in FIG. As a result, the engagement with the shift operation piece 21 is also disengaged.

Among the above configurations, the friction holding mechanism 13 is
Based on the technical means of the present invention, the following configuration is particularly provided. See Figure 1. That is, the friction plate 13d is shaped into an arcuate surface that substantially follows a radius of curvature r that is smaller and larger than the arcuate trajectory drawn by the tip of the friction member 13b that rotates together with the manual operation lever 12, and this friction plate The second pin shaft 19b serving as the pivot center of the friction member 13d
It is set near the above-mentioned locus. As a result, for example, as the manual operation lever 12 is operated to the speed increasing side (to the right in the drawing of FIG. 1), the spring 13c is contracted, and its biasing force is weakened, so that the friction member 13b The frictional holding force between the friction plate 13d and the friction plate 13d also becomes weaker as the vehicle is operated in the speed increasing direction. As already explained, due to this effect, the operating resistance of the manual operation lever 12 becomes substantially constant over the entire shift operation range. In addition, the first
In the figure, reference numeral 13e indicates an elongated hole that prevents the swinging motion of the friction plate 13d for the above-mentioned action from being restricted by the brake pedal 17, and the release of the friction retention by depressing the brake pedal 17 This is done by raising the area of the elongated hole 13e.

[Another example]

In the above-mentioned embodiment, the friction plate 13d is shaped to have a curvature that is almost the same as the arcuate trajectory drawn by the tip of the friction member 13b, and the shape when unfolded corresponds to the speed increasing side as shown in FIG. 6 of the drawings. The plate width may be formed to be narrower toward the accelerating side so that the frictional holding force becomes smaller toward the speed increasing side. Note that in this configuration, the long hole 13e described above is unnecessary.

[Brief explanation of the drawing]

The drawings show an embodiment of the working vehicle according to the present invention, in which FIG. 1 is a side view of the friction holding mechanism, FIG. 2 is a side view of the speed change operation section, FIG. 3 is a rear view of FIG. 1, and FIG. 4 is a side view of the friction holding mechanism. 1 is a plan view of FIG. 1, FIG. 5 is an overall side view of the tractor, and FIG. 6 is a conceptual diagram showing another embodiment. 6... Foot pedal, 12... Manual operation lever, 13... Friction holding mechanism, 17... Brake operating tool, 18... Linking means, H... Continuously variable transmission,
N...Shift neutral position.

Claims (1)

[Scope of Claims] 1. A hydraulic continuously variable traveling speed transmission device H is provided, and a foot pedal 6 for changing the speed of the continuously variable transmission device H is biased to return to a neutral gear position N via a spring 14. , a manual operation lever 12 that can be interlocked with and released from the foot pedal 6, and a friction holding mechanism 13 that frictionally fixes the manual operation lever 12, and the friction holding mechanism 13 is connected to the lever 12.
a lever-side friction member 13b that operates integrally with the lever 12, and a fixed-side friction member 13d supported by a fixed portion so as to be in sliding contact with the entire shift operation range of the lever 12;
This fixed side friction member 13d is composed of a spring 13c that presses and biases the lever side friction member 13b, and furthermore, the friction retention of the friction retention mechanism 13 is released in conjunction with the braking operation of the traveling brake operating tool 17. In a work vehicle equipped with a linking means 18 that The friction holding force due to the biasing action of the spring 13c of the friction holding mechanism 13 is applied to the deceleration side of the speed change operation range of the lever 12 so that the friction holding force of the friction holding mechanism 13 decreases as the force increases. A work vehicle that is set to have a larger effect and a smaller effect as the speed increases.