JPH04307174A - Work vehicle travel linkage device - Google Patents

Abstract

PURPOSE:To secure a proper hydrostatic braking action at all times by resetting and energizing a trunnion shaft of a hydrostatic continuously variable transmission (HST) to a neutral position by means of an elastic member, while linking it up with accelerator operation, thereby changing neutral reset-energizing force in the elastic member. CONSTITUTION:This device is provided with a neutral resetting mechanism T which acts on a trunnion shaft 6 and resets a hydrostatic type continuously variable transmission (HST) 3 to its neutral position. In brief, this neutral resetting mechanism T is composed of a cam plate 8 attached to the trunnion shaft 6, a rocker arm 10 with a roller 9 coming into contact with the surface of a recessed rail 8a of this cam plate 8 and a return spring 11. At this time, there is provided a linking mechanism A, interlocking with the operation of a hand accelerator lever 12 and adjusting tensile length of the return spring 11. That is, a rocking piece 13 and a crank 15 being free of rocking motion around a horizontal shaft center P are connected to each other with a connecting rod 16. In succession, when the rocking piece 13 is rocked counterclockwise, by way of example, engine speed is heightened, while the crank 15 is depressed, thereby tensing the return spring 11.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to a work vehicle such as a tractor or a transport vehicle that is equipped with a hydrostatic continuously variable transmission (hereinafter abbreviated as HST) for driving. It is related to making the ingredients work together.

0002

[Prior Art] The speed regulating operation of an HST is performed by changing the swash plate angle of the slant plate in the hydraulic pump section.Due to its structure, the operation required to rotate the trunnion shaft to change the swash plate angle The force has the property of changing depending on the engine speed. Then, when the stepping operation of the speed governor pedal that operates the trunnion shaft is released in order to stop traveling, a comprehensive restoration is achieved by the operation reaction force generated on the trunnion shaft due to the hydraulic reaction force acting on the inclined plate and the neutral return force of the neutral return mechanism. The force automatically returns the trunnion shaft to the neutral position, but the reaction force changes depending on the engine speed, so the degree of return when the governor pedal is stopped depends on the setting of the accelerator operating tool. It changed depending on the situation.

0003

[Problem to be Solved by the Invention] Therefore, due to the HST (hereinafter referred to as return hand HST) characteristic in which the neutral return force becomes stronger as the amount of depression of the governor pedal increases, it is difficult to stop the vehicle while moving at a relatively high speed. Then, the HST's neutral return operation is performed quickly, resulting in a large deceleration acceleration, resulting in a large and unpleasant deceleration shock, or when a stop operation is performed while driving at a relatively low speed, the HST's neutral return operation becomes slow, and the HST Braking action due to reverse drive of H
There was a phenomenon where the ST brake did not work as expected. In addition, from the viewpoint of reducing operating effort, an HST (hereinafter referred to as a forward movement HST) is configured such that the neutral return force becomes weaker as the amount of depression of the governor pedal increases, which is the opposite of the above case. , not much HS when driving at high speed.
This results in undesirable phenomena such as the T brake not being effective and the HST brake being too effective when driving at low speeds. An object of the present invention is to improve the driving feeling by allowing the HST brake to act in a manner appropriate to the speed, regardless of whether the driving speed is high or low due to a change in engine speed.

0004

[Means for Solving the Problems] To achieve the above object, the present invention includes a neutral return mechanism that urges the trunnion shaft of the HST to return to the neutral position by the elastic force of an elastic member, and also The present invention is characterized by being provided with an interlocking mechanism that interlocks with the force of the elastic member to change the neutral return biasing force.

[0005]

[Operation] By providing the above-mentioned linkage mechanism, it becomes possible to change and adjust the speed of the neutral return operation when the speed governor pedal is released and the vehicle is stopped in accordance with the difference in the amount of accelerator operation. Therefore, in the case of the returning hand HST, if the neutral return force is configured to become weaker as the accelerator operating tool is operated to the higher speed side, it will be able to compensate for the HST operation reaction force that becomes stronger as the engine speed increases. The effectiveness of the HST brake is set to match the driving speed, such as by keeping the total restoring force due to the resultant force always at a constant value, or by slightly increasing the total restoring force as the engine speed increases. It becomes possible to do so. In addition, in the case of forward-handling HST, by configuring the neutral return force to become stronger as the accelerator operating tool is operated to the higher speed side, it is possible to produce the same HST braking action as in the case of return-handling HST. .

[0006]

[Effects of the Invention] As a result, by using relatively simple modification means, the driving feeling can be improved by applying the HST brake with an appropriate strength corresponding to the speed, regardless of whether the driving speed is high or low due to a change in engine speed. We were able to provide a travel linkage device for work vehicles with improved performance.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A case where an embodiment of the present invention is applied to a tractor, which is an example of a working vehicle, will be described below with reference to the drawings. The tractor shown in FIG. 3 has a configuration in which power from an engine E is transmitted to drive wheels 2 by changing speed through a transmission 1 mounted at the rear of the body, and an HST 3 is integrally installed at the front end of the transmission 1. This HST 3 is located just below the floor 5 of the control section 4, and has a speed regulating pedal 7 directly attached to its trunnion shaft 6.

As shown in FIGS. 1 and 2, the trunnion shaft 6
A neutral return mechanism T is provided for self-returning the HST 3 to the neutral position N by acting on the neutral position N. That is, the cam plate 8 attached to the trunnion shaft 6, the recessed rail surface 8a of this cam plate 8
A swinging arm 10 having a roller 9 in contact with the neutral return mechanism T from a return spring (corresponding to an elastic member) 11
is constructed such that a neutral restoring force is always exerted by the biasing force of the return spring 11 to return the roller 9 to the neutral position N where it settles to the valley position of the recessed rail surface 8a. be. The HST 3 is configured to be a progressive type in which the reaction force acting on the trunnion shaft 6 becomes weaker as the amount of depression of the speed governor pedal 7 increases, so that the HST 3 is of a progressive type in which the rotational operation reaction force acting on the trunnion shaft 6 becomes weaker as the amount of depression of the speed governor pedal 7 increases. It is designed for easy operation. Further, reference numeral 12 designates a hand accelerator lever, and an adjustment rod 14 of a governor mechanism (not shown) is connected to a swinging piece 13 that is brought into contact with and operated by an operating piece 12a attached to the lower end of the hand accelerator lever. This tractor is provided with a linkage mechanism A that adjusts the tension length of the return spring 11 in conjunction with the operation of the hand accelerator lever 12. Next, the structure of the linkage mechanism A will be explained.

As shown in FIG. 1, the swing piece 13 and the crank 15, which is swingable around the horizontal axis P, are connected by a connecting rod 16.
A return spring 11 is secured to the tip end of the crank 15. To explain the operation, when the hand accelerator lever 12 is operated and the swinging piece 13 in the figure swings counterclockwise, the engine speed increases, and the connecting rod 16 pushes down the crank 15, causing the return spring to move. Pull and operate 11. In other words, the neutral restoring force by the neutral returning mechanism T becomes stronger. Conversely, when the hand accelerator lever 12 is operated to the side that lowers the engine speed, the connecting rod 16 is moved to the crank 15.
is pulled up, the upper support position of the return spring 11 moves downward, and its biasing force becomes weaker. In other words,
This weakens the neutral restoring force provided by the neutral return mechanism T. Therefore, the total restoring force, which is the result of the neutral restoring force and the operation reaction force acting on the trunnion shaft 6, always acts at a nearly constant strength regardless of the operating position of the hand accelerator lever, and the speed control This means that the deceleration and acceleration during the stop operation after the pedal 7 is released does not change much.

[Another Embodiment] In the case of the return-hand HST 3, as shown in FIG. Good.

[0011] Note that although reference numerals are written in the claims for convenience of comparison with the drawings, the present invention is not limited to the structure of the accompanying drawings by such entry.

[Brief explanation of drawings]

[Figure 1] Side view showing the structure of the travel linkage device

[Figure 2] Front view showing the structure near the trunnion shaft

[Figure 3] Side view of the tractor

[Fig. 4] Side view showing another structure of the traveling linkage device

[Explanation of symbols]

3 Hydrostatic continuously variable transmission 6 Trunnion shaft 11 Elastic member 12 Accelerator operation tool A Linkage mechanism T Neutral return mechanism

Claims (1)

[Claims] 1. A neutral return mechanism (T) is provided which urges the trunnion shaft (6) of the hydrostatic continuously variable transmission (3) to return to the neutral position by the elastic force of an elastic member (11), and A travel linkage device for a working vehicle, which is provided with a linkage mechanism (A) that changes the neutral return biasing force of the elastic member (11) in conjunction with the operation of an operating tool (12).