JPH01303372A - Speed change structure for working vehicle - Google Patents

Abstract

PURPOSE:To enable a smooth speed change operation in the title speed change structure by forcibly delaying the timing of a lock-up operation when the lock-up operation is performed together with the 'in' operation of a hydraulic clutch. CONSTITUTION:When a forward/backward changeover switch 21 is switched into the forward side F so as to turn in the hydraulic clutch 15a on the forward side, a lock-up switch is pushed, so as to generate an operational signal after an elapse of a set time (t) from the timing (a2) of the push operation, thereby obtaining the lock-up state of a torque converter T. Thus, even if the turning in operation of the hydraulic clutch 15a is abraptly performed, there occurs slippage in the torque convertor, so that it is possible to soften the shock so as to obtain a smooth speed change operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of a traveling transmission system for a working vehicle, and particularly to one equipped with a torque converter and a hydraulic clutch for shifting.

[Conventional technology]

An example of a device equipped with a torque converter and a hydraulic clutch for shifting as described above is disclosed in Japanese Patent Application Laid-open No. 58-3672, for example.
As disclosed in Japanese Patent Application No. 7, there is a device that is equipped with a hydraulic clutch for gear shifting on the downstream side of the torque converter.

[Problem to be solved by the invention]

For agricultural tractors, which are a type of work vehicle, it has been proposed to equip the torque converter with a lock-up mechanism in order to perform high-load, low-speed driving during towing work, etc. When the hydraulic clutch is brought into the engaged state by quickly increasing the operating pressure for engaging the hydraulic clutch on the downstream side, power may be suddenly transmitted to the downstream side, causing a shock.

The present invention has been developed with attention to the above-mentioned situation, and an object of the present invention is to suppress the occurrence of shock during a gear shift operation associated with a lock-up operation of a torque converter.

[Means to solve the problem]

A feature of the present invention is that the transmission structure for a work vehicle as described above is provided with a torque converter having a lock-up mechanism, a hydraulic clutch for transmission, and pressure increasing means for engaging the hydraulic clutch, and an operation for engaging the hydraulic clutch. The present invention is provided with a control means that allows the lock-up operation of the torque converter only after a set time has elapsed from the time when the oil pressure starts to rise, and its functions and effects are as follows.

[For production]

With the configuration described above, when the operating pressure to the hydraulic clutch is suddenly increased to perform a quick gear change operation such as during towing work, even if the hydraulic clutch suddenly starts to engage, the torque converter remains in the lock-up state. Because there is no torque converter, slip occurs in the torque converter and the shock is alleviated.

〔Effect of the invention〕

As described above, even if the hydraulic clutch for traveling gear shifting is engaged and operated at the same time as the lock-up operation, by forcibly delaying the timing of the lock-up operation, the shock can be alleviated and smooth gear shifting operations can be performed. became.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

Figure 2 shows the running power transmission system of an agricultural tractor, which is one of the working vehicles.A flywheel (2) is connected to the crankshaft (1) of an engine (not shown). A torque converter (T) is attached. This torque converter (T) is a front cover (
Oil is sealed in a casing formed by the back cover (6a) and the back cover (6b).
) side, a turbine liner (8) that converts the oil flow into rotational force, a stator (9) that guides the oil flow, a lock-up clutch (11), etc. There is.

Power from the crankshaft (1) is transferred to the pump impeller (7)
The oil is transmitted to the turbine liner (8) via oil, and is transmitted from the first cylindrical shaft (3) to the downstream side, and the lock-up clutch (11) is connected to the front cover (6a) by the hydraulic actuator (10). The first cylindrical shaft (3) can be directly connected to the front cover (6a) by pressing against the inner surface, and this state is a lock-up state.

As shown in Fig. 2, a hydraulic piston (13) is housed in one casing (12) on the downstream side of the torque converter (T).
a), (13b) and friction plates (14a), (14b
) consisting of two sets of hydraulic clutches (15a) and (15b
) is provided, and when one hydraulic clutch (15a) is engaged, the first cylindrical shaft (3) and the second cylindrical shaft (4) are directly connected, and power is transmitted to the downstream side in the normal rotation state (forward state). It will be transmitted. Also, the other hydraulic clutch (1
5b), the power from the first cylindrical shaft (3) is transmitted to the first transmission gear (16), the idle gear (not shown), the second transmission gear (18), the transmission shaft (17), and the third transmission gear. gear(
19), the power is transmitted to the second cylindrical shaft (4) through the fourth transmission gear (20) in a reverse state (reverse state). Also, a torque converter (T) that is directly connected to the flywheel (2) and passes through the first and second cylindrical shafts (3) and (4) transmits power to a working device (not shown). This is the PTO axis (5).

Next, we will discuss the lock-up operation system of the torque converter (T) and the important operation systems of the hydraulic clutches (15a) and (15b).
(21), Momentary type lock-up switch (23) for lock-up operation of the torque converter (T)
, an electromagnetically operated control valve (25) for the hydraulic actuator (10), and a hydraulic piston (1) in the two sets of hydraulic clutches (15a) and (15b).
3a), (13b), an electromagnetically operated switching valve (26), and both hydraulic pistons (13a).

Electromagnetic proportional pressure reducing valves (27a) and (27b) are provided for controlling the pressure of hydraulic oil relative to (13b).

Next, based on the signals from each switch (21>, (23)), answer (25), (26), (27a), (2
To explain in detail the flow of control in the control device (24) that issues an operation signal to the vehicle (7b), as shown in FIG. ) is operated to the forward side hydraulic clutch (15a) hydraulic oil supply side, and the electromagnetic proportional pressure reducing valve (27a)
The pressure at which the hydraulic clutch (15a) is engaged (
The pressure is increased by a vacuum as shown in the figure over a set time (1) until Pl), and the hydraulic clutch (15a) on the forward side is brought into the engaged state.

In that case, the next time point (a2) after the time point (a,) when the forward/reverse selector switch (21) is switched to the forward side (F)
), press and operate the lock-up switch (23) (signal (
bl)) Then, the lock-up lamp (22) that indicates the lock-up state to the operator lights up at the same time, but no operation signal is issued to the control valve (25) for lock-up simulation.
After the set time (1) has elapsed from the time (a2) of the signal (bl), an operation signal is issued, and the torque converter (T
) becomes locked up.

In addition, when the lock-up switch (23) is pressed and operated (signal (b2>) while moving forward in the lock-up state, the lock-up is released and the lock-up lamp (22) goes out, and the hydraulic clutch (15a) on the forward side is engaged. If the lock-up switch (23) is pressed again (signal (b3)) during this state, the lock-up lamp (22) lights up and a lock-up operation signal is immediately issued.

Then, the forward/reverse selector switch (21) is in the neutral position (N).
Or, when the reverse side (R) is operated, press the lock-up switch (23) (signal (b4),
signal (b5)), no lock-up signal is generated.

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]

The drawings show an embodiment of the transmission structure for a work vehicle according to the present invention,
Figure 1 is a time chart showing the operation signal to the hydraulic clutch and its boost characteristics, the signal from the lock-up switch, the characteristics of the lock-up operation signal, and the lighting state of the lock-up lamp, and Figure 2 is the torque converter, hydraulic clutch, etc. FIG. 3 is a sectional view showing the transmission system of the present invention, and FIG. 3 is a schematic circuit diagram of each operation valve and each switch. (15a), (15b)...hydraulic clutch,
(24)...Control fJL (T)...
Torque converter, (al)... Time at which the pressure of hydraulic oil to the hydraulic clutch starts to increase, (1)... Setting time.

Claims (1)

[Claims] A torque converter (T) having a lock-up mechanism, hydraulic clutches (15a), (15b) for shifting, and pressure increasing means for engaging the hydraulic clutches (15a), (15b), and the hydraulic clutch (15a) , (1
5b) and the start of increasing the pressure of the hydraulic oil (a_1)
A transmission structure for a work vehicle, comprising a control means (24) that allows lock-up operation of a torque converter (T) only after a set time (t) from .