JPH03186659A - Pressure oil supply structure of speed changing hydraulic clutch - Google Patents

Abstract

PURPOSE:To make a prompt speed change operation possible with a transmitting shock moderated, at the time of clutch meet, by connecting, in parallel to a boost control valve, a pressure reducing valve, which permits passing of pressure oil only at a preset pressure or less a little lower than a meet pressure at the time of starting contact of a hydraulic piston with a transmitting friction plate. CONSTITUTION:A pressure reducing valve 21, which permits passing of pressure oil only at a preset pressure or less a little lower than a meet pressure at the time of starting contact of a hydraulic piston of a hydraulic clutch B with a transmitting friction plate, is parallelly connected to a boost control valve F. Thus, even in the case of setting the boost control valve F to start boost action from a relatively low pressure, when the clutch is in connecting action, pressure oil is supplied to the hydrau lic clutch B through the pressure reducing valve 21 almost without draining during the time until a clutch pressure is increased to the preset pressure. Consequently, the initial charge of the pressure oil of the hydraulic clutch B is quickly performed. Also, when the clutch pressure exceeds the preset pressure, the pressure reducing valve 21 is closing-actuated with a smooth boost control by the boost control valve F executed, and a rapid rise of the clutch pressure, at the time of meet, can be relaxed.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a pressure oil supply structure for a hydraulic clutch for changing gears installed in agricultural tractors, etc. A hydraulic clutch for shifting that is equipped with a friction-type hydraulic clutch that engages and disengages, and a step-up control valve that gradually increases the supply pressure when the clutch engages in the pressure oil supply path to the hydraulic clutch. Regarding the pressure oil supply structure.

[Conventional technology]

In the above-mentioned pressure oil supply structure, for example, there is a structure previously filed by the present applicant (Japanese Patent Application No. 1-26423).In other words, the pressure in the oil passage on the downstream side of the supply and the internal spring are A pressure reducing valve type pressure increasing control valve is interposed in the pressure oil supply path to release the pressure in the oil path to the tank while balancing the pressure.

[Problem to be solved by the invention]

The above-mentioned conventional structure is designed to obtain a smooth pressure increase characteristic of the clutch pressure from a relatively low pressure.

However, in the conventional structure described above, if the pressure is set to start rising from a low pressure in order to reduce the transmission shock caused by pressure contact of the hydraulic clutch during gear shifting at low speeds with large shaft torque, the pressure rise will start from a low pressure, as shown in Fig. 5. In addition, the initial pressure oil filling time (T,) from the clutch disengaged state until the hydraulic piston of the hydraulic clutch meets (contacts) the friction plate becomes longer. In other words, as a result of the pressure increase control valve being configured as a pressure reduction valve, the differential pressure between the pressure on the output side of the hydraulic valve and the pressure in the clutch oil chamber becomes small, and the amount of pressure oil supplied decreases. Therefore, there is a drawback that the wasted time in the gear shifting operation becomes long and the operation takes a long time.

The present invention aims to solve the above-mentioned problems by making reasonable improvements.

[Means to solve the problem]

A feature of the present invention is that, in the pressure oil supply structure of the hydraulic clutch for transmission described at the beginning, only a pressure equal to or lower than the set pressure that is slightly lower than the meet pressure at which the hydraulic piston in the hydraulic clutch starts contacting the transmission friction plate is provided. A pressure reducing valve that allows passage of pressure oil is connected in parallel with the pressure increasing control valve.

[For production]

Even if the boost control valve is set to start pressure boost operation from a relatively low pressure, when the clutch is engaged, most of the pressure oil will flow through the pressure reducing valve while the clutch pressure rises to the set pressure. Since the oil is supplied to the hydraulic clutch without being drained, initial pressure oil filling in the hydraulic clutch can be quickly performed. Furthermore, when the clutch pressure exceeds the set pressure, the pressure reducing valve closes and the pressure increasing control valve performs smooth pressure increasing control, thereby making it possible to alleviate the sudden increase in clutch pressure at the time of meeting.

〔Effect of the invention〕

Therefore, according to the present invention, it is possible to reduce the initial pressure oil filling time from the clutch disengaged state to the clutch engaged state while effectively alleviating the transmission shock at the time of clutch engagement, thereby enabling quick gear shifting operations. It became possible to do it.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

As shown in Fig. 4, the power from the engine (1) is transmitted through the main clutch (2) to the main transmission (A), the multi-disc hydraulic clutch (B), the forward/reverse switching device (C), and the auxiliary transmission. Transmission (
D), ultra-reduction gear (E), and the transmission power is sequentially transmitted to the front and rear wheels (3) and (4) to the differential gear (3a) of each of the front and rear wheels.
), (4a), and a working transmission system to transmit the power from the main clutch (2) to the external power output shaft (6) via the transmission mechanism (5). A system is formed to constitute a drive system of a four-wheel drive agricultural tractor.

The main transmission (A) is equipped with two synchronized mesh gear transmission mechanisms and can be shifted to four speeds, and the forward/reverse switching device (C) and the auxiliary transmission (D) are both synchronized. The main transmission (A) has two hydraulic cylinders (TI).

(T2), the auxiliary transmission (D) is a single hydraulic cylinder (
) to change gears, and forward/reverse switching device (C).
) is configured to perform a manual speed change operation, and furthermore, in this agricultural tractor, when these three types of speed change operations are performed, the hydraulic clutch (B) is disengaged at the start of the speed change operation, and the speed change operation is performed. A hydraulic control system is provided for shifting the gear without disengaging the main clutch (2) by engaging the hydraulic clutch (B) at the time of completion.

That is, the hydraulic control system is configured as shown in FIG. 1, and in this system, a pressure oil supply path (8) for supplying pressure oil from a hydraulic pump (7) to a hydraulic clutch (B), Boost control valve (F) and pilot pressure operated switching valve (9)
), and the three hydraulic cylinders (TI
), ('rz), and (TI), and a pilot oil passage (11) for obtaining pilot pressure for operating the switching valve (9>).
) are arranged in branches.

Note that the hydraulic cylinders (T r ), (T2), (
A check valve (12) that operates to open and close is connected to each of the operating systems of the forward/reverse switching device (C).
The pilot pressure applied to the switching valve (9) is changed to operate the hydraulic clutch (B) on and off as described above.

The pressure increase control valve (F) is configured to suppress a sudden increase in clutch pressure and increase the clutch pressure with predetermined characteristics when the switching valve (9) is turned on.

As shown in FIG. 3, the boost control valve (F) includes a spool-type valve body (24), a plunger (25) that is partially inserted into the valve body (24), First spring (2
6) and has an orifice (27) in the center; a piston (29) operated by pressure oil from this valve member (28);
9) and the second spring (24) disposed between the valve body (24)
30) A pilot oil line system (32) is constructed by installing each of them in a casing (31) and supplying pressure oil from a valve body (24).
) is a back pressure chamber (25a) of the plunger (25) and a first hydraulic chamber (28a) in which the valve member (28) is housed.
The hydraulic clutch (B) communicates with the hydraulic clutch (B) via the intermediate oil passage (8a).

Then, by operating the switching valve (9), the hydraulic clutch (
When the supply of pressure oil to B) is started, the plunger (
25) applies pressure in the closing direction to the valve body (24), and at the same time, pressure in the opening direction accompanying the movement of the piston (29) is applied to the valve body (24) via the second spring (30).
Pressure oil is supplied in a state where the respective pressures are balanced.

On the other hand, a hydraulic chamber (33) housing the piston (29)
An oil passage (33a) is formed in a more horizontal direction, and a dedicated oil drainage passage (34) is provided to drain the pressure oil in the hydraulic chamber (33) through the oil passage (33a). Road (3
4) is provided with a pilot type two-position switching valve (35) as a switching mechanism for draining pressure oil from the hydraulic chamber (33).

Further, a hydraulic pilot type accumulator (16) is connected to the hydraulic chamber (33), and its pilot oil path (1
7) to the sub-transmission device (D) switching operation hydraulic cylinder (
It is connected to the high-speed side operating oil passage (18) of T3).In this way, when the shaft torque is large, the accumulator (16) functions to moderate the pressure increase characteristic and reduce the shock when the clutch is engaged. It is set as.

The hydraulic piston (1) in the hydraulic clutch (B)
A pressure reducing valve (21) that allows pressure oil to pass only below a set pressure that is slightly lower than the meet pressure when the transmission friction plate (20) starts contacting the transmission friction plate (20) is installed in parallel with the pressure increase control valve (F). The hydraulic clutch (B) is connected to the hydraulic clutch (B) so as to shorten the initial pressure oil filling time until the contact pressure is reached.

Providing the pressure reducing valve (21) in this manner makes it possible to reduce the initial pressure oil filling from the clutch disengaged state to the clutch engaged state, as shown in Fig. The time (T,) has been shortened, and the time from the start of the shift operation to the half-clutch state has been shortened, making it possible to perform a speed shift operation quickly.

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 drawings]

1 to 4 show an embodiment of a pressure oil supply structure for a hydraulic clutch for shifting according to the present invention, and FIG. 1 is a hydraulic circuit diagram;
FIG. 2 shows clutch pressure increase characteristic data, FIG. 3 is a sectional view of the pressure increase control valve, and FIG. 4 is a transmission system diagram. And the fifth
The figure shows clutch pressure increase characteristic data of a conventional example. (8)... Pressure oil supply path, (19)...
Pressing piston, (20)...Friction plate, (21)
...Pressure reducing valve, (B) ... Hydraulic clutch, (F) ... Pressure increase control valve.

Claims (1)

[Scope of Claims] A friction type hydraulic clutch (B) which is turned on and off by sequence control in accordance with the gear change operation is installed in the traveling transmission system, and a pressure oil supply path (8) to the hydraulic clutch (B) is provided. , a pressure oil supply structure for a hydraulic clutch for transmission, which is equipped with a pressure increase control valve (F) that gradually increases the supply pressure when the clutch is engaged, the hydraulic piston (19) in the hydraulic clutch (B) )
A pressure reducing valve (21) that allows pressure oil to pass only below a set pressure that is slightly lower than the meet pressure when the oil starts coming into contact with the transmission friction plate (20) is arranged in parallel with the pressure increasing control valve (F). Pressure oil supply structure for the connected transmission hydraulic clutch.