JPH01210658A - Clutch changing-over circuit for continuously variable transmission - Google Patents

Abstract

PURPOSE:To prevent a clutch from slips and damages while maintaining a overriding property satisfactorily by providing throttle flow paths for affording communication between relief valves interposed in oil paths to respective stage clutches in valve opening positions of the relief valves. CONSTITUTION:Oil pressure in an oil supply path 200 is transmitted through throttle flow paths 311-341 of corresponding relief valves 211-241 to clutches C1-C4 already operated in changing over the clutches. When the next stage clutch is operated by electromagnetic valves 114-144 and clutch change-over valves 113-143 in speed change, even if total pressure in the corresponding relief valves 211-241 is lower than the set pressure in the relief valve of previous stage clutch to close said relief valve, only leak flow from the throttle flow paths 311-341 flows to the clutch side so that no slip takes place in the clutch. Thus, the relief valve having a satisfactory overriding property is used while the clutch can be prevented from slips and damages.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a clutch switching circuit for a continuously variable transmission, and is suitable for application to a multistage hydrostatic mechanical continuously variable transmission, and relates to an improvement in a latch switching circuit. .

[Conventional technology]

A multi-stage hydrostatic mechanical continuously variable transmission having the configuration shown in FIG. 2 is known. This is from input shaft 1 to output shaft 2.
2-speed mechanical input deceleration planetary gear device P1, composite planetary gear device P2 of mechanical drive system and hydraulic drive system for 2nd and 4th speeds, and planetary gear device P2 for 1st, 2nd, 3rd, and 4th speeds. A mechanical drive system and a hydraulic drive system are connected by a synthetic planetary gear system P3. In addition, a pump 3 with a variable discharge volume driven by a gear 5, 6, 7 and a morph 4 with a fixed discharge volume driven by this pump 3 are connected to the input shaft 1, and the output of the pump 3 is controlled by a gear 5, 6, 7. 8.9.10 to the sun gear of the synthetic planetary gear set P2, and via gear 8.9.11.12 to the sun gear of the synthetic planetary gear set P3. Clutches are attached to these transmissions to switch the speed stages, and the first speed clutch CI, which intermittents rotation of the ring gear of the synthetic planetary gear device P3 on the output shaft 2 side, is connected to the clutch CI for the first speed, which connects the planetary gear device Pi on the input shaft 1 side. A second-speed clutch C2 is installed for intermittent rotation of the ring gear. Furthermore, a synthetic planetary gear device P2 and a synthetic planetary gear device P
A 3rd speed clutch C3 for intermittent transmission of rotation from the input shaft 1 is connected to the shaft member connecting the ring gear No. 3, and a 3rd speed clutch C3 is connected to the arm connecting the planetary gears of the planetary gear unit P1 and the composite planetary gear unit P2. A 4-speed clutch C4 is attached to each of them to interrupt rotation transmission from the input shaft 1.

In the above-mentioned transmission, the speed is changed at a point where the relative speed difference in the next stage clutch section disappears, so the speed stage can be changed without a clutch switching shock.

Also, for this reason, the gears are always shifted in the order of adjacent gears,
There is no need to skip any intermediate gears.

By the way, the clutch CI for the above transmission.

In order to switch C2, C3, and C4, a hydraulic circuit as shown in Fig. 3 is used (Utility Application No. 59-1511).
No. 93). In this circuit, oil passages to each clutch CI, C2, C3, and C4 are provided in parallel to the hydraulic pump 101, and pressure regulating valves 111, 121, 131, and 14 are connected to the oil passages from the upstream side.
1. A pressure reducing valve 112.122.132.142 and a clutch switching valve 113.123.133.143 are arranged, and the clutch switching valve is a solenoid valve 114.12.
4.134.144 for opening and closing operations. Hydraulic pressure acts on each solenoid valve 114, 124, 134, 144 from the hydraulic pump 101 via the pressure reducing valve 102 as a pilot valve, and when the solenoid valve is turned ON, the clutch switching valve works, and the corresponding clutch is activated. ing. Note that the hydraulic oil from the hydraulic pump 101 is supplied to the pressure regulating valve 1.
It is designed to be returned to the tank via 03.

According to such a hydraulic circuit, each clutch CI.

Pressure regulating valve 111.121 in the oil line leading to C2, C3, C4
．． 131 and 141, it is possible to prevent a pressure drop in the current clutch until the next-stage clutch is engaged during a gear shift, and there is an advantage that the clutch engagement time can be minimized with respect to the hydraulic pump flow rate. Therefore, when attempting to engage the C2 clutch from the currently engaged state of the CI clutch, when the oil passage to the C2 clutch is opened, the oil placed in the supply oil passage 200 from the hydraulic pump 101 The pressure regulating valve 103 closes due to the decrease in circuit pressure, but the pressure regulating valve 121 works and the pressure in the supply oil passage 200 is reduced by the pressure regulating valve 121.
The pressure of the C1 clutch is also maintained at the set pressure of the pressure regulating valve 121.

[Problems to be Solved by the Invention] However, according to the conventional clutch switching circuit described above, by installing the pressure regulating valves 111, 121, 131, and 141, the pressure in the supply oil passage 200 cannot exceed the set pressure of the pressure regulating valve. However, there was a problem due to the good override characteristics of the pressure regulating valve. For example, C1, C
When attempting to perform a switching operation between two clutches, the fourth
As shown in the figure, the pressure regulating valve 111.12
1, and the pressure gradient of the pressure regulating valve 103 disposed in the supply oil path 200 is small, and the set pressure of the clutch side pressure regulating valve 111, 121 deviates up and down as shown in the figure due to manufacturing errors etc. (Set pressure Pill>P121 ). In this case 0
When two clutches are operated, even if the hydraulic pump 101 has a full flow, the supply pressure only increases to the total pressure Pg of the pressure regulating valve 121, and does not reach the set pressure of the pressure regulating valve 111 on the CI clutch side. In such a case, hydraulic oil does not flow to the CI clutch, and there is usually an oil leak on the downstream side of the pressure regulating valve, so pressure does not build up, and this clutch pressure decreases, causing clutch slippage and eventually leading to clutch failure. There was a problem. For this reason, conventionally 1. Fifth
As shown in the figure, it is necessary to actively use a pressure regulating valve with poor override characteristics. The pressure characteristics of the pressure regulating valves on the operating clutch side intersect, and the pipe pressure acts on the already operating clutch, so even if there is a leak, the clutch will not be damaged.

As described above, in the past, it was not possible to use a pressure regulating valve with good override characteristics, and on the contrary, a pressure regulating valve with poor override characteristics had to be actively used, which was a serious problem. In addition, in response to the poor characteristics, the supply oil path 200
It is also necessary to increase the set pressure of the pressure regulating valve 103 provided in the hydraulic pump 103, and therefore there is also the problem that the capacity of the hydraulic pump 101 must also be increased.

The present invention focuses on the above-mentioned conventional problems, and provides a continuously variable transmission that can use a pressure regulating valve with good characteristics, and does not have problems such as clutch breakage due to the good characteristics even if hydraulic oil leaks. The purpose of the present invention is to provide a clutch switching circuit.

[Means to solve the problem]

In order to achieve the above object, a clutch switching circuit for a continuously variable transmission according to the present invention is used in a multi-stage hydrostatic mechanical continuously variable transmission and includes at least a pressure regulating valve in the oil path from the pump to each stage clutch. In the interposed clutch switching circuit, a throttle flow path is provided that communicates with the pressure regulating valve at its closed position.

[Effect]

According to the above configuration, when switching the clutch, even if the pressure regulating valve is closed because the full pressure of the pressure regulating valve after switching is lower than the pressure regulating valve set pressure before switching, the throttle flow path is provided in this and the pressure regulating valve is closed. Since only the amount of leakage flow is allowed to flow to the clutch side, pipe pressure acts on the clutch, preventing it from slipping or breaking. Therefore, a pressure regulating valve with excellent override characteristics can be used.

(Example) Below, an example of the clutch switching circuit for a continuously variable transmission according to the present invention will be described in detail with reference to the drawings.The same components as shown in FIG. will be added and the explanation will be omitted.

FIG. 1 is a configuration diagram of a clutch switching circuit of a continuously variable transmission according to an embodiment, and is a hydraulic circuit used in the transmission shown in FIG. 2. As shown in this figure, the circuit operates from a hydraulic pump 101 to each clutch CI, C2, C3, C4 in order to apply hydraulic pressure to each clutch CI, C2, C3, C4.
, C4 are provided in parallel from the supply oil path 200. Such oil passages 201, 202, . . . to each clutch CI, C2, C3, C4.
203.204 has a pressure regulating valve 211.22 on the most upstream side.
1.231.241 is arranged, and this pressure regulating valve is said to form a throttle passage 311.321.331.341 through which hydraulic oil flows to the clutch side especially when the valve is closed. This is the pressure regulating valve 211.221.231.
Any oil that can flow an amount that compensates for the amount of oil leaking from constituent members downstream of 241 may be sufficient. This throttle flow path 311.321.331.341 is connected to the pressure regulating valve 211.2.
It can be easily provided by forming it on the valve body of No. 21, 231, and 241.

Note that the clutch C1 is connected to the downstream side of the pressure regulating valve 211.221.231.241 via a pressure reducing valve and a clutch switching valve.
, C2, C3, and C4 are connected, and the clutch switching operation is performed by a solenoid valve, as in the conventional case.

According to such an embodiment, when switching the clutch,
Clutches C1, C2, C3, and C4 that are already in operation are supplied with the supply oil passage 20 through the throttle passage 311.321.331.341 of the corresponding pressure regulating valve 211.221.231.241.
0 oil pressure is being transmitted, and when the next stage clutch is operated during gear shifting, the corresponding pressure regulating valves 211, 221.
Even if the total pressure of 231 and 241 is lower than the set pressure of the pressure regulating valve of the front stage clutch, slippage of the clutch can be prevented. Therefore, the pressure regulating valve 211.221.231.2
The disadvantages caused by the good characteristics of 41 are improved.
Moreover, for this reason, the set pressure of the pressure regulating valve 103 installed in the supply oil path 200 can also be lowered, and thus the hydraulic pump 101
It is possible to reduce the horsepower consumption of the clutch switching circuit for a continuously variable transmission with less power loss.

(Effects of the Invention) As explained above, according to the present invention, since the pressure regulating valve is provided with a throttle passage through which hydraulic oil flows when the valve is closed, the pressure regulating valve with good override characteristics is used, and the clutch This has the effect of preventing slipping and damage.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a clutch switching circuit of a continuously variable transmission according to an embodiment, Figure 2 is a configuration diagram of a multistage hydrostatic mechanical continuously variable transmission, and Part 3 is a diagram of a conventional continuously variable transmission clutch. The configuration diagram of the switching circuit, FIG. 4, and FIG. 5 are explanatory diagrams of override characteristics, respectively. 101...Hydraulic pump, 211.221.23
1.241...Pressure regulating valve, 311.321.33
1.341... Throttle channel. Agent Patent Attorney Oka 1) Kazuki Figure 1 Figure 2 Figure 3 Whistle 4 Figure pressure (kg 1cm Figure 5 7゛Flow tl/n1□

Claims (1)

[Claims] In a clutch switching circuit used in a multistage hydrostatic mechanical continuously variable transmission and having at least a pressure regulating valve interposed in an oil path from a pump to each stage clutch, the valve is communicated with the pressure regulating valve at its closed position. A clutch switching circuit for a continuously variable transmission characterized by providing a throttle flow path.