JPH0246350A - Transmission gear for working vehicle - Google Patents

Abstract

PURPOSE:To enable to correspond to the increase in the running load by providing an alternative switching clutch between the first and second transmission states, an automatic switching means for operating the switching clutch and an artificial switching preventing means for preventing the automatic switching operation. CONSTITUTION:When a speed change operating means 22 is operated to the low speed side, the second transmission state is automatically obtained and the direct motive power is supplied to the traveling group from a hydraulic pump P so that the output corresponding to the load can be obtained. Moreover, as a means B for preventing an automatic switching means A from operating at the time of normal load running is provided, the speed change operating means 22 is not switched to the second transmission state even in operating the means 22 to the low speed side. The fine speed change operation can be thus obtained by a static-pressure type continuously variable transmission as a main transmission gear and a sub-transmission gear while the first transmission state is maintained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a transmission device for a working vehicle mounted on an agricultural tractor or the like, which is a hydrostatic continuously variable transmission device consisting of a hydraulic pump and a hydraulic motor. The present invention relates to a transmission device for a work vehicle equipped with the device.

[Conventional technology]

In the transmission of this type of work vehicle, the hydraulic motor output shaft is simply connected to the travel transmission system.

[Problem to be solved by the invention]

In devices employing such a traveling transmission transmission device, when working in wet fields or the like, the traveling load becomes large and the vehicle may become unable to travel.

In other words, when the running load exceeds the set value, the high pressure relief valve (16) of the hydrostatic continuously variable transmission (3) shown in Fig. 3 operates to relieve hydraulic fluid from the high pressure side to the low pressure side.
The structure is designed to protect closed circuits. Therefore, the hydraulic motor (!Wakawara) could not obtain sufficient output, and it was not possible to escape from the wet field.

An object of the present invention is to effectively utilize an existing transmission system to provide a vehicle that can cope with an increase in running load.

[Means to solve the problem]

The characteristic configuration according to the present invention is as follows: (1) A standard first transmission state in which the hydraulic motor output shaft of the hydrostatic continuously variable transmission as the main transmission is transmission connected to the traveling transmission system, and a hydraulic pressure of the hydrostatic continuously variable transmission. A switching clutch is selectively provided in a second transmission state in which the pump output shaft is transmission connected to the traveling transmission system and the hydraulic motor output shaft is disconnected from the traveling transmission system; (1) An automatic switching means is provided that operates a switching clutch to bring about the second transmission state when a gear shift operating tool for the transmission is operated to a low speed side; The switching prevention means is provided, and its effects are as follows.

[For production]

As shown in characteristic configuration (2), when the vehicle is unable to travel due to wet fields or the like, the second transmission state is automatically entered by operating the speed change operating tool to the low speed side.

Therefore, since power is directly supplied to the travel system from the hydraulic pump, an output corresponding to the load can be obtained.

Moreover, since a means is provided to prevent the automatic switching means from operating during normal load running, even if the gear shift operating tool is operated to the low speed side, the transmission state is not switched to the second transmission state, but instead of being switched to the standard first transmission state. While maintaining the same state, fine gear shifting operations can be performed using the hydrostatic continuously variable transmission as the main transmission and the auxiliary transmission.

〔Effect of the invention〕

As a result, even if it becomes impossible to drive in wet fields, etc., it can be pulled out relatively easily than before, and when high-load driving is required, such as when high-pressure relief is activated, artificial If the drag operation of the switching prevention means is prevented, the second transmission state can be obtained simply by switching the speed change operating tool to the low speed side, resulting in good operability.

〔Example〕

This article provides an overview of the transmission system for agricultural tractors used as working vehicles.

As shown in Figure 2, the engine (1) and main clutch (
The power from 2) is the hydraulic motor 0 of the hydrostatic continuously variable transmission (hereinafter referred to as H3T) as the main transmission (3).
1) Transmission is transmitted from the output shaft (7) to the rear wheel differential mechanism (5) via a gear transmission as an auxiliary transmission (4) that can shift between high, medium and low three speeds, and
) is transmitted to the front wheel transmission shaft (6) from this side, while H
3T (3) hydraulic pump (P) output shaft (8) to PTO
It is transmitted to the rear PTo shaft (11) via the first gear transmission mechanism (10), and the second gear transmission mechanism. (
12) to the mid PTO shaft (13).

Note that the front wheel transmission shaft (6) is equipped with a front wheel transmission device (15).
The front wheel rotational speed can be switched between a high speed state faster than the rear wheel rotational speed and a substantially constant speed state, thereby reducing roughness of the field when turning.

Next, HST (3) will be explained. As shown in Fig. 3, a closed circuit is formed between the variable displacement hydraulic pump (P) and the fixed hydraulic motor (), and a high pressure relief valve (16) provides relief from the high pressure side to the low pressure side.
(16) and a charge pump (17) for replenishing hydraulic oil into the closed circuit. The charge circuit connected to the closed circuit by the charge pump (17) is branched off and connected to a hydraulic oil circuit of a servo operating mechanism (18) for the swash plate of the variable displacement hydraulic pump (P).

Therefore, the charge oil from the charge pump (17) is used as hydraulic oil for the servo operating mechanism (18),
The charge pump (17), which is always in operation, can also be used as a hydraulic pump for the servo operating mechanism (18).

A device used during high running loads such as in wet fields will be explained. As shown in FIG. 1, a switching clutch (19) is provided in the transmission system from the hydraulic motor (7) of the H3T (3) to the sub-transmission (4). 19) has a function of switching between a first transmission state and a second transmission state, which will be described later. In other words, this switching clutch (
19) is a clutch in which a hydraulic friction multi-disc clutch (19A) and a multi-generation clutch (19B) are integrated,
It is attached to the input shaft (20) of the sub-transmission device (4). Here, the piston (19a) of the hydraulic friction multi-disc clutch (19A) and the clutch piece (
19b) are integrated, and both clutches (19A) and (19B) are selectively activated by hydraulic pressure and a return spring. Therefore, when the heavy duty clutch (19B) is operated greatly, the standard first transmission state in which power is transmitted from the hydraulic motor (M) output shaft (7) to the sub-transmission device (4) is established, and the heavy duty clutch (19B) is activated. When the clutch (19B) is disengaged and the friction multi-plate clutch (19A) is activated, H3
A second hydraulic pump (P) whose power is transmitted from the output shaft (8) to the auxiliary transmission (4) via the PTC transmission (9).
A transmission state appears.

Next, the automatic switching means (A) for this switching clutch (19) will be explained. As shown in FIG. 3, a branch circuit (a) is provided to supply pressure oil from the charge pump (17) as hydraulic oil to the friction multi-disc clutch (19A), and this branch circuit (a)
) is equipped with a two-position electromagnetic switching valve (21). On the other hand, the shift operating tool (22) for the sub-transmission device (4) is provided with a limit switch (23) that senses when the shifting operating tool (22) is operated to the low speed side. ) is interposed in the operating circuit for the electromagnetic switching valve (21). Therefore, when the speed change operating tool (22) is operated to the low speed side, the limit switch (22)
3) is turned ON, pressure oil is supplied to the friction multi-disc clutch (19A), and the second transmission state is established. Such a limit switch (23), electromagnetic switching valve (21), etc. are referred to as automatic switching means (A).

Further, a manually operated switch (24) is connected in series with the limit switch (23) to the operating circuit for the electromagnetic switching valve (21).
The structure is such that the automatic switching operation of the automatic switching means (A) is prevented when the circuit is open. In other words, the speed change operation tool (2
Even if 2) is operated to the low speed side, the second transmission state will not appear. Herein, the manually operated switch (24) is referred to as an artificial switching prevention means (B) [Another embodiment] ■ The automatic switching means (A) includes a device that prevents the speed change operation tool (22) from being operated to the low speed side. Other contact and non-contact sensors may be used as a means for sensing that the limit switch is used, and is not limited to limit switches.

■ The clutch that provides both transmission states may be a friction multi-disc clutch or a multi-disc clutch, or the friction multi-disc clutch may not be a hydraulic type, but may be a dry type in which a piston is actuated by an actuator. good.

(2) The sub-transmission device (4) may be of two stages, high and low, or may include a super-reduction device used when digging trenches, etc.

(2) The above embodiments can also be applied to agricultural machinery other than agricultural tractors, transport vehicles, construction machinery, etc.

Incidentally, although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structure shown in the accompanying drawings.

[Brief explanation of the drawing]

Drawings Showing an embodiment of the transmission system for a working vehicle according to the present invention, FIG. 1 is a longitudinal sectional view showing a switching clutch, FIG. 2 is a configuration diagram showing the entire transmission system, and FIG. 3 is a hydraulic circuit and automatic switching means. ,
FIG. 3 is a configuration diagram showing an artificial switching prevention means. (3)... Hydrostatic continuously variable transmission, (4)...
...Sub-transmission device, (7) ...Hydraulic motor output shaft, (8) ...Hydraulic pump output shaft, (19)
......Switching clutch, (22)...Speed change operation tool, (A)...Automatic switching means, (B)...
...Artificial switching prevention means, ()A) ...Hydraulic motor, (P) ...Hydraulic pump.

Claims (1)

[Claims] The standard first transmission state in which the hydraulic motor (M) output shaft (7) of the hydrostatic continuously variable transmission (3) as the main transmission is transmission connected to the traveling transmission system, and the hydrostatic continuously variable transmission ( 3)
Alternatively, the hydraulic pump (P) output shaft (8) of the hydraulic pump (P) is transmission connected to the travel transmission system, and the hydraulic motor (M) is placed in a second transmission state in which the output shaft (7) and the travel transmission system are disconnected. A switching clutch (19) that can be switched between
automatic switching means (19) for operating a switching clutch (19) to bring about the second transmission state when the
A) and an artificial switching prevention means (B) for preventing the automatic switching operation of the automatic switching means (A).