JPH03189472A - Hydraulic structure for shifting - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic structure for changing gears installed on, for example, agricultural tractors, and more specifically, the present invention relates to a hydraulic structure for changing gears installed on, for example, an agricultural tractor. The present invention relates to a hydraulic structure for shifting, in which a clutch is configured to engage and disengage under hydraulic sequence control in conjunction with a shifting operation.

[Conventional technology]

As the above-mentioned hydraulic structure for shifting, there is a structure previously filed by the present applicant (Japanese Patent Application No. 1-26277). In other words, a pressure regulation mechanism is installed in the supply path to the hydraulic clutch that gradually increases the pressure, and as the pressure in the oil path increases beyond the spring pressure, the pressure in the oil path is released to the tank side. It was configured as a pressure reducing valve type, and was configured to increase the spring pressure as the pressure in the oil passage increased.

[Problem to be solved by the invention]

The conventional structure described above is designed to smoothly increase the hydraulic clutch pressure through the balance between the oil passage pressure and the spring force, thereby alleviating the transmission shock that accompanies sudden latch engagement.

Considering the operation of a hydraulic clutch, when the clutch is switched from the clutch disengaged state to the clutch engaged state, pressure oil flows into the oil chamber of the hydraulic clutch, and the hydraulic piston meets (contacts) the transmission friction plate. ) Then, the flow of pressure oil ends, and after that, only the pressure increases. However, although the pressure regulating mechanism described above has a smooth pressure increase characteristic due to the balance with the spring force, as mentioned above, there is a difference in the pressure increase characteristic of the clutch pressure between when pressure oil is flowing in and after the pressure oil has stopped flowing. will occur (see Figure 4). In other words, when pressure oil flows in, a pressure loss occurs in the hydraulic piping and the pressure rise in the hydraulic clutch becomes small, but when the pressure oil stops flowing when the hydraulic piston meets (see point (P) in Figure 4), , there will be no pressure loss and the pressure will rise rapidly to the set pressure of the pressure regulating mechanism. As a result, there is a risk that a certain amount of transmission shock will occur when the clutch engages, resulting in deterioration of ride comfort, which is particularly noticeable during low-speed driving with large shaft torque.

One possible way to solve the above problem is to set the pressure increase characteristic of the pressure regulating mechanism to increase the pressure extremely slowly, but if you do this, the operation time required for gear shifting will be longer and the operation will be slower. There is a negative effect.

The present invention allows quick gear shifting operations, and
In addition to suppressing the shock at clutch engagement to the smallest possible level, the above-mentioned shock suppression can always be maintained regardless of fluctuations in the amount of pressurized oil supplied due to fluctuations in engine speed (or changes in oil temperature, etc.). It is intended to.

[Means to solve the problem]

A characteristic configuration of the present invention is that, in the hydraulic structure for shifting described at the beginning, (1) the pressure oil supply path from the engine-driven pump to the hydraulic clutch has a supply pressure at a predetermined level near the clutch meet pressure at a location on the upper side of the clutch; A hydraulic pilot type pressure relief valve is connected to drain part of the supplied pressure oil from the point only when the pressure is within the specified range; A first orifice is provided to limit the amount of oil drained, and a second orifice is provided in the oil drain path by the pressure relief valve to limit the amount of oil drained to a predetermined amount.

[For production]

(B) Due to the characteristic configuration (■) above, even when the pressure oil supply amount is set to a large value in order to shorten the initial pressure oil filling time from the disengaged state of the hydraulic clutch to the time of clutch engagement, the supply pressure is When the pressure increases to near the clutch meet pressure, a portion of the supplied pressure oil is drained via the pressure relief valve, thereby alleviating the sudden increase in clutch operating pressure. Furthermore, when the clutch is engaged, the clutch operating pressure increases, so oil draining from the pressure relief valve is stopped.

(B) From the above characteristic structure (■), even if the amount of pressure oil supplied increases due to fluctuations in engine speed or rise in oil temperature, the flow rate is limited by the first orifice, so the hydraulic clutch It is possible to suppress a sudden increase in clutch operating pressure at the time of clutch engagement due to excessive hydraulic oil being supplied during initial filling of the clutch. Furthermore, by providing the second orifice, it is possible to prevent hydraulic oil in excess of the set type from being discharged at the time of clutch engagement, and the operation of the hydraulic sequence control is not inhibited.

〔Effect of the invention〕

As a result, the above effect (a) reduces the entire pressure oil supply amount, thereby reducing the shock at clutch engagement without causing adverse effects such as prolonging wasted time or not being able to obtain sufficient latch operating pressure. It became possible to relax as much as possible.

Furthermore, with (0), as described above, while effectively alleviating the shock at the time of latch meeting, an increase in the amount of supplied pressure oil due to fluctuations in engine speed is suppressed, and the exhaust from the pressure relief valve is suppressed. Prevents variations in oil amount,
Moreover, the amount of oil discharged itself can be suppressed to a predetermined amount, making it possible to prevent excessive oil discharge. As a result, it is possible to maintain stable hydraulic clutch operation at all times while reducing the shock caused by clutch engagement.

〔Example〕

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

As shown in Fig. 3, power from the engine (1) is transmitted via the main clutch (2) to the main transmission (A), the multi-disc hydraulic clutch (B), the forward/reverse switching device (C), and the sub Gearbox (
D) and super reduction gear (E), and transmits the shifting power to the front and rear wheels (3) and (4) differential gears (3a) respectively.
, (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). This constitutes the drive system of a four-wheel drive agricultural tractor.

The main transmission (A) is composed of two synchromesh type gear transmission mechanisms, and is capable of shifting into four stages. The main transmission (A) has two hydraulic cylinders (TI).

(T2), the auxiliary transmission (D) is a single hydraulic cylinder (
Tl) to perform gear shifting operations, 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 by engaging the hydraulic clutch (B) at the time of completion without having to disengage the main clutch (2).

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), Gradual pressure increase mechanism (F) and pilot pressure operated switching valve (
9) and the three hydraulic cylinders (T,
), (T2), and (Tl), 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 (Tl), (T2), (Tl
) and the forward/reverse switching operation (C) are each linked with an open/close operation type check valve (12). During a gear shift operation, the switching valve (9) is opened/closed by opening/closing each of the check valves. ) to operate the hydraulic clutch (B) on and off as described above.

Incidentally, the gradual pressure increase mechanism (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 and operated. In addition, the oil drain path (13) from the gradual pressure increase mechanism CF)
A two-position switching valve (1, 4) operated by the pilot pressure of the pilot oil passage (11) is interposed therein.

The engine (1) is connected to the hydraulic clutch (B).
) The pressure oil supply path (8) from the drive pump (7) is supplied to the clutch upper side portion (8a) only when the supply pressure at the portion (8a) is within a predetermined range near the clutch meet pressure. A hydraulic pilot type pressure relief valve (15) is connected from (8a) to drain a part of the supplied pressure oil. To be more specific, the pressure relief valve (15) is interposed in an oil drain path (16) formed between the clutch upstream portion (8a) and the tank (T), and is located at both blocking positions. (n+),
(nz) and a central communication position (d). Then, one of the first pilot oil passages (17
) is connected to the valve upper side of the oil drain path (■6), and the second pilot oil path (18) on the other side is connected to the high-speed operation side oil of the hydraulic cylinder (T, ) for operating the auxiliary transmission ([)). (19). Further, it is biased by a spring (20) toward the operating direction side by the second pilot oil passage (18).

The pressure relief valve (15) is operated when the sub-transmission (D) is switched to the low speed side, that is, when the second pilot oil path (
18) is in the oil drain state, when the supply pressure increase operation by the gradual pressure increase mechanism (F) is started, the predetermined pressure near the clutch meet pressure in the pressure increase characteristic (see point Q in Figure 2) The communication position (d) is set only in the vicinity, and a portion of the supplied pressure oil is drained. In this way, it is possible to suppress a sudden increase in the supply pressure at the time of clutch engagement (see FIG. 2).

Furthermore, when the sub-transmission device (D) is operated to a high speed state, the second pilot oil passage (18) rises to the pump pressure, so the pressure relief valve (15) is not switched to the communication position (d). , it is possible to obtain efficient pressurization characteristics without leakage of pressure oil. This is because in high-speed running conditions, the shaft torque is small and no shock occurs when the clutch engages.

A first orifice (21) for limiting the flow rate of hydraulic oil to the hydraulic clutch (B) to a predetermined amount is provided in the pressure oil supply path (8) on the upper side of the gradual pressure increase mechanism (F), and The maximum inflow rate for F) is limited. or,
A second orifice (22) is provided in the oil drain path (16) of the pressure relief valve (15) to limit the amount of oil drained to a predetermined amount. A third orifice (23) having the same function as the first orifice (21) is also provided in the pressure oil supply path (8) in the gradual pressure increase mechanism (F).

One side biasing spring (20) in the pressure relief valve (15)
) The range of oil drain state setting pressure can be changed and adjusted by adjusting the spring force of ). The switching valve (9) is configured to be biased toward the shutoff position by a spring (24),
This prevents unexpected switching operations caused by a drop in pilot oil pressure due to the operation of the pressure relief valve (15).

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 3 show an embodiment of the hydraulic structure for shifting according to the present invention, in which FIG. 1 is a hydraulic circuit diagram, FIG. 2 is clutch pressure increase characteristic data, and FIG. 3 is a transmission system diagram. and,
FIG. 4 shows clutch pressure increase characteristic data of a conventional example. (1)...Engine, (7)...Pump, (8)...Pressure oil supply path, (8a)...
...Upper side location, (15)...Pressure relief valve, (
16)... Oil drain path, (21)... First
Orifice, (22)...Second orifice, (
B)...Hydraulic clutch.

Claims (1)

[Claims] This is a hydraulic structure for gear shifting, in which a friction type hydraulic clutch (B) is interposed in the traveling transmission system, and the hydraulic clutch (B) is configured to be turned on and off by hydraulic sequence control in accordance with gear shifting operations. and a pressure oil supply path (8) from the engine (1) drive pump (7) to the hydraulic clutch (B).
) on the upper side of the clutch (8a), the relevant location (8a)
A hydraulic pilot type pressure relief valve (15) is connected which drains a part of the supplied pressure oil from the point (8a) only when the supply pressure at the point (8a) is within a predetermined range near the clutch meet pressure. A first orifice (21) is provided in the oil supply path (8) to limit the flow rate of hydraulic oil to a predetermined amount or less, and a predetermined amount of drained oil is provided in the oil drain path (16) by the pressure relief valve (15). A hydraulic structure for shifting, which is provided with a second orifice (22) that limits the speed.