JPH0350146B2 - - Google Patents

Description

Detailed Description of the Invention The present invention relates to a hydraulic servo motor for driving a directly coupled control valve in a hydraulic continuously variable transmission, and particularly to a directly coupled control valve for directly controlling a hydraulic motor and a hydraulic pump in a hydraulic continuously variable transmission. A pilot valve in which a servo piston with a front end connected to the piston is slidably fitted into a cylinder hole of a servo cylinder, the rear end wall of the servo cylinder is slidably penetrated, and an oil passage switching groove is formed on the outer periphery. The present invention relates to a hydraulic servo motor which is slidably fitted into a blind valve hole of the servo piston having an annular oil passage and a land on the inner periphery.

In such a servo motor, if the pilot valve moves backward or overshifts excessively with respect to the servo piston, there is a problem in that the oil passage switching groove does not accurately switch the oil passage.

Furthermore, in a servo motor, if the pilot valve's oil passage switching groove is an annular groove, when the pilot valve is operated, the edge of the annular groove will catch on the edge of the annular oil passage of the valve hole due to a slight inclination of the valve. This prevents smooth sliding of the pilot valve and causes a failure in the hydraulic drive of the servo piston.

The present invention has been proposed in view of the above, and uses a common stopper mechanism that can be easily disposed within the servo piston without being obstructed by the direct control valve, and is easy to assemble. It can be used both as a regulating means and as a means for preventing the pilot valve from coming off from the servo cylinder, and also effectively prevents the pilot valve from falling against the valve hole and from getting caught between the edges of the oil passage switching groove and the annular oil passage. It is an object of the present invention to provide a hydraulic servo motor for driving a directly coupled control valve in a hydraulic continuously variable transmission, which has a simple structure and solves the above problem by allowing the valve to always slide smoothly.

In order to achieve this object, the present invention provides a servo piston with a direct connection control valve connected to the front end for direct connection control between the hydraulic motor and the hydraulic pump of a hydraulic continuously variable transmission, in the cylinder hole of a servo cylinder. A pilot valve that is slidably fitted and slidably passes through the rear end wall of the servo cylinder and has an oil passage switching groove formed on the outer periphery is connected to the annular oil passage and land of the servo piston on the inner periphery. In a hydraulic servo motor for driving a directly coupled control valve in a hydraulic continuously variable transmission, the servo piston is slidably fitted into a blind valve hole in the servo piston, and the rear end surface of the servo piston has the valve hole in the inner end surface. A recess is formed that is open and locks a stopper ring on the inner circumferential surface, and a stopper pin that can engage with the stopper ring within the recess is integrated on the outer periphery of the pilot valve in order to limit the retraction limit of the pilot valve with respect to the servo piston. Further, the oil passage switching groove is formed of a plurality of chamfered portions arranged in the circumferential direction provided on the outer peripheral surface of the pilot valve, and between the chamfered portions, the oil passage switching groove is provided in contact with the land and the pilot valve is The pilot valve is characterized in that a plurality of guide lands for preventing the valve from tilting are provided at approximately equal intervals in the circumferential direction of the pilot valve.

Hereinafter, one embodiment of the present invention will be explained with reference to the drawings. In Fig. 1, a hydraulic servo motor S
, a servo cylinder 2 fixed to a machine frame 1, a servo piston 4 slidably fitted into a cylinder hole 3 of the servo cylinder 2, and a servo cylinder 2.
The pilot valve 6 is comprised of a pilot valve 6 whose intermediate portion is slidably fitted into the through hole h of the rear end wall 2a and whose tip outer periphery is slidably fitted into the valve hole 5 of the servo piston 4. A high-pressure oil chamber 8 connected to a hydraulic pressure source is formed at the front of the servo cylinder 2, and a piston rod 7 at the front end of the servo piston 4 always faces the front end of the piston rod 7 into the chamber 8.

The cylinder hole 3 is defined by a front oil chamber 9 surrounding the piston rod 7 by the servo piston 4, and a rear oil chamber 10 surrounding the pilot valve 6.
The rear oil chamber 10 is always in communication with the high pressure oil chamber 8 via an oil hole 11 passing through the servo piston 4 in the axial direction.

The valve hole of the servo piston 4 is formed into a blind hole with the front end closed, and an annular oil passage 12, a land 13, an annular oil passage 14, and a land 15 are sequentially arranged on the inner circumference from the front end to the rear end. The annular oil passage 12 is in continuous communication with an oil reservoir (not shown) through an oil hole 16 passing through the pilot valve 6 in the axial direction, and the annular oil passage 14 is connected to a front oil reservoir through an oil hole 17 extending in the radial direction. Constant communication with room 9.

On the other hand, the pilot valve 6 moves the annular oil passage 14 between the other annular oil passage 12 and the rear oil chamber 1 by sliding back and forth.
The oil passage switching groove 18 is provided on the outer periphery of the tip of the oil passage switching groove 18 that selectively communicates with the pilot valve 6, and as shown in FIGS. A plurality of chamfered portions 19, 19, arranged in the circumferential direction, three in the illustrated example, formed by cutting.
19, and these chamfered portions 19,
19, 19, a plurality of guide lands 20, 20, 2 are provided on the same plane as the outer peripheral cylindrical surface of the front and rear parts.
0 remain at approximately equal intervals in the circumferential direction of the pilot valve 6. In addition, each guide land 20 may be formed with a narrow groove 21 that communicates between the adjacent chamfered portions 19, as shown by chain lines in FIG.

A recess 4a is formed in the rear end surface of the servo piston 4, and the valve hole 5 is opened in the inner end surface, and a stop ring 22 made of a circlip is engaged in the inner peripheral surface of the recess 4a. The recess 4a to restrict the backward limit
A stopper pin 23 that can engage the stopper ring 22 within the pilot valve 6 has both ends thereof connected to the pilot valve 6.
The pilot valves 6 each protrude from the outer peripheral surface of the pilot valve 6.
is fixed to.

In the above, the dimensions of each part are designed so that the following formula holds.

B<A-C However, A... Cross-sectional area of the servo piston 4 B... Cross-sectional area of the piston rod 7 C... Cross-sectional area of the pilot valve 6 Next, the operation of the servo motor S will be explained.
First, the pilot valve 6 is moved forward (moved to the left in FIG. 1) to block the annular oil passage 14 and the rear oil chamber 10 with its outer peripheral surface, and to open the oil passage switching groove 18, that is, the chamfered portions 19, 19, 19. If the two annular oil passages 12 and 14 of the valve hole 5 are communicated through the valve hole 5, the pressure oil in the high pressure oil chamber 8 will flow only into the rear oil chamber 10 via the oil pressure 11.
Hydraulic pressure is applied to the rear end surface of the servo piston 4.
Therefore, the rear end pressure receiving area of the servo piston 4 is A-C
Since the front end pressure receiving area of the piston rod 7 facing the high pressure oil chamber 8 is B, the servo piston 4 is hydraulically driven forward to follow the pilot valve 6 due to the above-mentioned inequality B<A−C. Ru.

Next, move the pilot valve 6 back (rightward movement in Figure 1)
and both annular oil passages 12, 14 are connected by the outer peripheral surface thereof.
If the annular oil passage 14 and the rear oil passage 10 are communicated with each other via the oil passage switching groove 18, the pressure oil in the high-pressure oil chamber 8 can flow not only to the rear end oil chamber 10 but also to the front oil chamber 9. The oil flows in and applies hydraulic pressure to both the front and rear end faces of the servo piston 4. At this time, too, the front end face of the piston rod 7 receives the hydraulic pressure from the high pressure oil chamber 8, so the servo piston 4 eventually receives the hydraulic pressure in the backward direction. The pressure-receiving area that receives the hydraulic pressure in the forward direction is A, while the pressure-receiving area that receives the hydraulic pressure in the forward direction is A-C. Naturally, since A>A-C, the servo piston 4 is hydraulically driven rearward to follow the pilot valve 6. be done.

What should be noted here is that as the pilot valve 6 is operated back and forth, the oil passage switching groove 18, that is, the chamfered portion 1
Even when the guide lands 9, 19, 1 pass through the lands 13 or 15 of the valve hole 5, the guide lands 20, 20, 20 of the pilot valve 6 are in contact with the lands passing through, and thereby the pilot valve Valve 6
Tilt in either direction can be prevented.

Next, the relationship between the servo motor S and the hydraulic continuously variable transmission in which it is incorporated will be explained. In the illustrated example, the servo piston 4 performs clutch control of a known hydraulic continuously variable transmission comprising a hydraulic pump and a hydraulic motor, and direct control of the pump and motor. That is, D is a hydraulic oil distribution mechanism interposed between a hydraulic pump and a hydraulic motor (both not shown), and is connected to the distribution panel 24.
and a distribution ring 25 supported by the front end of the servo cylinder 2 and in close contact with the distribution plate 24, and the high pressure oil chamber 8 formed inside the distribution ring 25.
A discharge port 26 connected to a cylinder hole in the discharge stroke of the hydraulic pump and a high pressure communication port 27 connected to a cylinder hole in the expansion stroke of the hydraulic motor are communicated in a low pressure oil chamber 8' formed on the outside of the distribution ring 25. The suction port 26' connected to the cylinder hole in the suction stroke of the hydraulic pump and the low pressure communication port 27' connected to the cylinder hole in the contraction stroke of the hydraulic motor are communicated, and due to these communication, hydraulic oil is transferred between the hydraulic pump and the motor. Hydraulic power transmission is carried out in circulation.

Short-circuit ports 28, 28 that communicate between the high-pressure oil chamber 8 and the low-pressure oil chamber 8' are bored in the side wall of the servo cylinder 2 so as to be opened and closed according to the forward and backward movement of the piston rod 7. is provided with a direct control valve 29, which is a poppet valve, which closes the discharge port 26 when it advances beyond the closed position of the short-circuit ports 28, 28.
A replenishment port 30 connected to a feed pump (not shown) opens in the discharge port 26, and a check valve 31 is provided there.

Thus, when the piston rod 7 is in the retracted position shown, the shorting ports 28, 28 are opened, and therefore, the pressure oil in the high pressure oil chamber 8 is short-circuited to the low pressure oil chamber 8' through these ports 28, 28. The hydraulic motor does not operate, and this is the so-called clutch-off state. Furthermore, when the piston rod 7 moves forward and completely closes the short-circuit ports 28, 28, the pressure oil in the high-pressure oil chamber 8 is supplied to the hydraulic motor through the high-pressure communication port 27 and operates it, so this is a so-called clutch-on state. When the short-circuit ports 28, 28 are half-opened up to this point, the clutch is in a half-clutch state. If the piston rod 7 moves further beyond the closed position of the short-circuit ports 28, 28,
The direct control valve 29 closes the distribution panel 24 and closes the discharge port 26, thereby hydraulically locking the hydraulic pump, so that the hydraulic motor can be mechanically driven directly from the hydraulic pump, that is, the hydraulic pump and motor can be driven directly. A direct connection state is obtained. It goes without saying that all of the above controls are performed by operating the pilot valve 6 back and forth.

As described above, according to the present invention, a servo piston having a direct connection control valve connected to its front end for performing direct connection control between a hydraulic motor and a hydraulic pump of a hydraulic continuously variable transmission is slid into a cylinder hole of a servo cylinder. The servo piston has an annular oil passage and a land on its inner periphery, and includes a pilot valve that is freely fitted, slidably penetrates the rear end wall of the servo cylinder, and has an oil passage switching groove formed on its outer periphery. In a hydraulic servomotor for driving a directly coupled control valve in a hydraulic continuously variable transmission, which is slidably fitted into a blind valve hole, the valve hole is opened on an inner end surface of the rear end surface of the servo piston. A recessed portion in which a stopper ring is engaged is formed on the inner peripheral surface, and a stopper pin that can engage with the stopper ring within the recessed portion is integrally formed on the outer periphery of the pilot valve in order to limit the retraction limit of the pilot valve with respect to the servo piston. Since the stopper ring and stopper pin are provided in a protruding manner, the stopper ring and the stopper pin work together to reliably restrict the retraction limit of the pilot valve with respect to the servo piston and are effective in preventing overshifting of the pilot valve. It is also possible to reliably prevent the material from slipping out. Moreover, since the stopper ring and the stopper pin are provided in the recess on the rear end surface of the servo piston, they can be easily arranged regardless of the presence of the direct-coupled control valve on the front end side of the servo piston. Moreover, when assembling the servo motor,
It is only necessary to fit the tip of the pilot valve into the valve hole of the servo piston and then set the stopper ring on the inner periphery of the recess. Therefore, although the stopper ring and stopper pin are specially installed in the recess, the ease of assembling the servo motor is improved. There is no decline in

Furthermore, the oil passage switching groove is constituted by a plurality of chamfered portions arranged in the circumferential direction provided on the outer circumferential surface of the pilot valve, and a chamfered portion is provided between the chamfered portions and contacts the land to prevent the pilot valve from tilting. Since a plurality of guide lands are provided at approximately equal intervals in the circumferential direction of the pilot valve, the plurality of guide lands are distributed in the circumferential direction of the pilot valve, but when the pilot valve is operated, the valve does not move. The center of the through hole in the valve hole and the rear end wall of the servo cylinder is in constant sliding contact with the land of the hole and can always accurately guide the sliding movement of the pilot valve, so that the tip and middle portions of the pilot valve slide together, respectively. Even if the axes are slightly misaligned, each guide land effectively prevents the pilot valve from falling with respect to the center axis of the valve recess, and from getting caught between the edges of the oil passage switching groove and the annular oil passage. As a result, the pilot valve can always slide smoothly, and as a result, the retraction limit of the pilot valve with respect to the servo piston is reliably regulated as described above, and the direct control of the front end of the servo piston is always controlled. It can be accurately hydraulically driven. Moreover, since the oil passage switching groove can be formed by simply chamfering the outer circumferential surface of the pilot valve, machining is easy and can contribute to cost reduction and improvement of machining accuracy.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention, FIG. 2 is a side view of the main part of the pilot valve therein,
FIG. 3 is a sectional view taken along the line -- in FIG. 2. S... Hydraulic servo motor, 2... Servo cylinder, 2a... Rear end wall, 3... Cylinder hole, 4...
Servo piston, 4a... recess, 5... valve hole, 6
... Pilot valve, 12, 14 ... Annular oil passage, 1
3, 15...Land, 18...Oil passage switching groove, 19
... Chamfered portion, 20 ... Guide land, 22 ... Stopper ring, 23 ... Stopper pin, 29 ...
Direct control valve.

Claims (1)

[Claims] 1 A servo cylinder 2 is equipped with a servo piston 4 connected to a front end thereof with a direct connection control valve 29 for direct connection control between a hydraulic motor and a hydraulic pump of a hydraulic continuously variable transmission.
A pilot valve 6 is slidably fitted into the cylinder hole 3 of the servo cylinder 2, slidably penetrates the rear end wall 2a of the servo cylinder 2, and has an oil passage switching groove 18 formed on its outer periphery.
is the annular oil passage 12, 1 of the servo piston 4.
4 and lands 13 and 15 on the inner periphery of the hydraulic servo motor for driving a control valve in a hydraulic continuously variable transmission, which is slidably fitted into a blind hole-shaped valve hole 5 having lands 13 and 15 on the inner periphery. The end face is formed with a recess 4a in which the valve hole 5 is opened on the inner end face and a stopper ring 22 is locked on the inner circumferential face. A stopper pin 23 that can be engaged with the stopper ring 22 is integrally provided on the outer periphery of the pilot valve 6, and the oil passage switching groove 18 is formed on the outer periphery of the pilot valve 6 through a plurality of circumferentially arranged stopper pins 23. A plurality of guide lands 20 are provided between the chamfered portions 19 in the circumferential direction of the pilot valve 6 to prevent the pilot valve 6 from tilting by contacting the lands 13 and 15. A hydraulic servo motor for driving a directly coupled control valve in a hydraulic continuously variable transmission, characterized in that the motors are provided at equal intervals.