JPH02102970A - Swash plate control servo unit of hydraulic continuously variable transmission - Google Patents

Abstract

PURPOSE:To facilitate machining, to obtain the cylindricity and the straightness with high accuracy and to enable correct swash plate control by forming an insert hole where a spool member is inserted as a through hole formed on a valve member in a servo unit of a hydraulic continuously variable gear. CONSTITUTION:In a speed change servo unit 30 of a hydraulic continuously variable transmission, there are provided a piston member 32 inserted in a housing 31, a valve member 33 fixed to the interior of the piston member and a spool member 34 concentrically inserted in the valve member in such a manner as to freely slide right and left. When the spool member 34 is moved right and left, the piston member 32 is forced to follow it and moved by hydraulic force. With a trunnion shaft of a hydraulic motor connected to the piston member 32 as the center, the piston member is turned to vary the capacity. An insert hole of the spool member is formed as a through hole, so that machining is facilitated, high accuracy can be obtained and the oscillation of a swash plate can be controlled correctly.

Description

Detailed Description of the Invention A.Object of the Invention (Field of Industrial Application) The present invention relates to a hydraulic continuously variable transmission, and more specifically,
The present invention relates to a servo unit used for variable swing control of the swash plate angle of a swash plate hydraulic pump or a swash plate hydraulic motor that constitute this transmission.

(Prior Art) Continuously variable transmissions composed of a hydraulic pump and a hydraulic motor have been known for a long time and are used for various purposes. 1
For example, Tokuko Publication No. 32-7159, Tokuko Publication No. 5
As disclosed in Japanese Patent Application No. 8-50142, a constant discharge amount type hydraulic pump is connected to an input shaft, and the oil discharged from this pump is guided to a variable displacement type hydraulic motor via a closed hydraulic circuit. There is a continuously variable transmission that drives an output shaft connected to the transmission.

In such a continuously variable transmission, the gear ratio (input rotation speed/
In the case of the transmission disclosed in the above publication, the output rotation speed) is controlled by variable control of the capacity of the pump or motor.
(by variable control of the displacement of the hydraulic motor). In the case of a swash plate type hydraulic motor (or hydraulic pump), this variable displacement control can be performed by controlling the swing angle of the swash plate, thereby making it possible to perform stepless control of the transmission.

As a method for controlling the swing angle of the swash plate, a method using a servo cylinder mechanism using hydraulic pressure is often used. In this case, the force required to swing the swash plate corresponds to the hydraulic pressure in the hydraulic circuit that connects the hydraulic pump and the hydraulic motor, so the hydraulic pressure in this hydraulic circuit should be used as the hydraulic pressure for operating the servo cylinder. There are many. However, the problem is that it is difficult to directly control this oil pressure to control the operation of the servo cylinder because the oil pressure in this hydraulic circuit can be quite high and fluctuates greatly depending on the load on the transmission. There is.

For this reason, it has conventionally been common practice to provide a pilot valve for controlling supply and discharge of hydraulic pressure to and from the servo cylinder mechanism in the hydraulic circuit. As such a servo unit, for example, the servo unit proposed by the present applicant is disclosed in Japanese Patent Application Laid-Open No.
83453, a piston member axially movably inserted into a cylinder housing and connected at one end to a swash plate of a pump or motor; The hydraulic pressure supply to the left and right cylinder chambers in the cylinder housing is switched and controlled according to the axial movement of the spool member, and the piston member is moved to follow the spool member to swing the swash plate. There are some that perform dynamic control.

(Problems to be Solved by the Invention) When configured as described above, an insertion hole for the spool member is provided in the piston member, but there is a problem in that machining of this insertion hole is difficult.

In particular, in the case of the above configuration, the insertion hole is a blind hole, and there is a problem in that it is difficult to adjust the cylindricity and straightness of the insertion hole to the degree of construction during machining. If the machining accuracy of the insertion hole is not good, the axial movement resistance of the spool member inserted into the insertion hole tends to increase, impairing the smooth movement of the spool member, and eventually causing damage to the swash plate due to the movement of the piston member. There is a problem that the control may become inaccurate.

The present invention has been developed in view of these problems, and it is possible to machine the spool member insertion hole into the piston member with high precision, enable smooth axial movement of the spool member, and achieve accurate swash plate control. The purpose of the present invention is to provide a servo unit that can perform the following functions.

(Means for Solving the Problems) As a means for achieving the above object, the servo unit of the present invention includes a cylinder housing fixed to a case of a continuously variable transmission, and a cylinder housing that is movable in the axial direction within the cylinder housing. A piston member inserted and connected at one end to a swash plate of a hydraulic pump or a hydraulic motor, a cylindrical valve member having an insertion hole penetrating in the axial direction and fitted and held within the piston member, and an insertion hole of this valve member. It consists of a spool member that is inserted movably in the axial direction within the insertion hole, and the hydraulic pressure supply to the left and right cylinder chambers in the cylinder housing is switched and controlled according to the axial movement of the spool member within the insertion hole. The piston member is configured to move to follow the spool member to control the swinging of the swash plate.

(Function) When using the servo unit with the above configuration, when the spool member is moved in the axial direction, the piston member can be moved in the axial direction following this movement, and this piston member is connected to the swash plate. Therefore, the swinging of the swash plate can be controlled by controlling the movement of the spool member. In this case, the insertion hole into which the spool member is inserted is formed in the valve member fitted and held by the piston member, and this insertion hole is a through hole formed in the valve member. For this reason, the insertion hole can be machined through the valve member before it is inserted into the member, making the process easier.
Highly accurate cylindricity, straightness, etc. can be obtained.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 is a hydraulic circuit diagram of a continuously variable transmission in which swash plate control is performed by a servo unit according to the present invention. In this figure, the continuously variable transmission T is driven by an engine E via an input shaft 1. It has a constant discharge type swash plate axial plunger type hydraulic pump P, and a variable displacement type swash plate axial plunger type hydraulic motor M that drives wheels (not shown) via a forward/reverse switching device 20. These hydraulic pump P and hydraulic motor M are connected to the discharge port of pump P and the motor M.
The first oil passage La, which communicates the suction port of the pump P, and the second oil passage Lb, which communicates the suction port of the pump P and the discharge port of the motor M, are connected to form a hydraulic closed circuit. . Of these two oil passages La and Lb, the 1st/Ii circuit La is activated when the pump P is driven by the engine E and the motor M is rotationally driven by the oil pressure from the pump P to drive the wheels, i.e. When the wheels are driven by the engine E via the continuously variable transmission T, the pressure becomes high (at this time, the second oil passage Lb is at low pressure), while the second oil passage Lb The pressure is high when the engine brake is applied in response to driving force from the wheels (at this time, the pressure in the first oil passage La is low).

A direct coupling clutch valve DC that can connect and disconnect this oil passage La is disposed within the first oil passage La.

A discharge port of a charge pump 10 driven by the engine E via a pair of gear sets 9a and 9b is connected to a charge oil passage Lh having a check valve 15 and a third oil passage Lc having a pair of check valves 3.3. connected to a closed circuit. Oil sump 1 by charge pump 10
Hydraulic oil pumped up from 7 and regulated by the charge pressure relief valve 16 is supplied to the lower pressure side of the two oil passages La and Lb by the action of the check valves 3, 3.

A governor valve 8 is attached coaxially with this charge pump 10. Hydraulic oil at a predetermined pressure is supplied to this governor valve 8 from a control valve (not shown), and the governor valve 8 converts the pressure of this hydraulic oil into governor oil pressure corresponding to the rotational speed of the engine E. Note that the input and output oil passages connected to the governor valve 8 are not shown in this figure.

A fourth oil passage Ld having a shuttle valve 4 is connected to the closed circuit. This shuttle valve 4 has high-pressure and low-pressure IJ-F valves 6, 7, and has fifth and sixth oil passages L e + L f connected to the oil sump 17.
is connected. The shuttle valve 4 is a 2-point/3-position switching valve, and the first and second oil passages L a + L
It operates according to the oil pressure difference between the first and second oil passages La.
+Lb, the high pressure side oil passage is communicated with the fifth oil passage Le, and the low pressure side oil passage is communicated with the sixth oil passage Lf. As a result, the relief oil pressure in the oil passage on the high pressure side is regulated by the high pressure relief valve 6, and the relief oil pressure in the oil passage on the low pressure side is regulated by the low pressure relief valve 7.

A seventh oil passage Lg that short-circuits both oil passages is also provided between the first and second oil passages La and Lb, and this seventh oil passage Lg has a variable throttle that controls the opening degree of this oil passage. A main clutch valve CL consisting of a valve is provided.

An output shaft 28 is arranged parallel to the rotating shaft 2 of the hydraulic motor M, and a forward/reverse switching device 20 is provided between both shafts 2 and 28. This device 20 includes first and second drive gears 21 and 22 disposed on a rotating shaft 2 with a spacing in the axial direction, and rotatably supported by an output shaft 28 and a first drive gear 2
1, a second wave gear 25 that meshes with the second drive gear 22 via an intermediate gear 24 and is rotatably supported on the output shaft 28, and the first and second wave gears. A clutch hub 26 is fixed to the output shaft 28 between 23.25 and a clutch gear 23a or 25a which is slidable in the axial direction and formed on the side surfaces of the clutch hub 26 and the driven gears 23 and 25, respectively. A sleeve 27 that is selectively connected is provided, and this sleeve 27 is moved left and right by a shift fork 29. The specific structure of this forward/reverse switching device 20 is shown in FIG. In this forward/reverse switching device 20, when the sleeve 27 is slid leftward in the figure by the shift fork 29 and the clutch gear 23a of the first driven gear 23 and the clutch hub 26 are connected as shown in the figure, the output The shaft 28 is rotated in the opposite direction to the rotating shaft 2, and the wheels are rotated in the forward direction as the continuously variable transmission T is driven. On the other hand, when the sleeve 27 is slid to the right by the shift fork 29 and the clutch gear 25a of the second driven gear 25 and the clutch hub 26 are connected, the output shaft 28 is rotated in the same direction as the rotating shaft 2, The wheels are rotated in the reverse direction.

Next, the concrete structure of the continuously variable transmission T will be briefly explained using FIG. 2.

This continuously variable transmission T is configured such that a hydraulic pump P and a hydraulic motor M are disposed together in a space surrounded by first to fourth cases 5a to 5d. The input shaft 1 of the hydraulic pump P connects to the output shaft E of the engine E via a coupling 1a.
It is combined with s. A centrifugal filter 50 is disposed on the inner peripheral side of this coupling 1a.

Further, a drive gear 9a is connected to the input shaft 1 by a spline, and a driven gear 9b meshes with the drive gear 9a. The driven gear 9b is coaxially connected to the drive shaft 11 of the charge pump 10, and the rotation of the engine E is transmitted to the drive shaft 11 of the charge pump 10 via the pair of gears 9a+9b, thereby driving the charge pump 10. . This drive shaft 11 passes through the charge pump 10 and protrudes to the side opposite to the gear 9b, and is also connected to the governor valve 8. Therefore, the rotation of the engine E is also transmitted to this governor valve 8, and the governor valve 8 causes the engine E to rotate.
The governor hydraulic pressure corresponding to the rotation of is created.

The hydraulic pump P includes a pump cylinder 60 spline-coupled to the input shaft 1, and a plurality of pump plungers 62 slidably engaged with a plurality of cylinder holes 61 formed in the pump cylinder 60 at equal intervals on the circumference. It is rotationally driven by the power of the engine E transmitted through the input shaft 1.

The hydraulic motor M includes a motor cylinder 70 provided surrounding the pump cylinder 60, and a plurality of motor plungers 72 that slide into a plurality of cylinder holes 71 formed in the motor cylinder 70 at equal intervals on the circumference. It is designed to be able to rotate relative to the pump cylinder 60 coaxially.

The motor cylinder 70 is composed of first to fourth parts 70a to 70d that are aligned in the axial direction and are integrally coupled.

The first portion 70a has a bearing 7 at its left end outer periphery.
The pump swash plate ring 63 is rotatably supported by the case 5b via the pump 9a, and the right inner surface is inclined with respect to the input shaft 1 to form a pump swash plate member. is provided. Second portion 70b
The plurality of cylinder holes 71 are formed in the third portion 70c, and the third portion 70c has a distribution plate 80 in which an oil passage to each cylinder hole 61.71 is formed. The fourth portion 70d includes the first
A gear member GM forming the second drive gears 21 and 22 is press-fitted and rotatably supported by the case 5c via a bearing 79b.

An annular pump 64 is rotatably and slidably attached to the pump swash plate puffer 63, and the pump shoe 64 and the pump plunger 62 are connected to each other via a connecting rod 65 so as to be able to swing freely to some extent. pumpsi x -
64 and the pump cylinder 60 are fully engaged 8
8a and 68b are formed. Therefore, when the pump cylinder 60 is rotationally driven from the input shaft 1, the pump shoe 6
4 is rotated at the same time, and the pump plunger 62 is reciprocated in accordance with the inclination of the pump swash plate ring 63, thereby sucking in oil from the suction port and discharging oil to the discharge port.

Also, a swash plate member 73 facing each motor plunger 72
The second case 5b is connected to the second case 5b via a pair of trunnion shafts (swing shafts) 73a that protrude from both outer ends in a direction perpendicular to the paper surface.
It is swingably supported by. A motor swash plate ring 73b is disposed on the surface of the swash plate member facing the motor plunger 72, and a motor shoe 74 is attached along the motor swash plate ring 73b. The motor shoe 74 is swingably connected to the end of each motor plunger 72. The swash plate member 73 is connected to the piston rod 33 of the transmission servo unit 30 via a link member 39 at a position away from the trunnion shaft 73a. When moved in the direction, the swash plate member 7
3 is adapted to swing around a trunnion shaft 73a.

The fourth portion 70d of the motor cylinder 70 is formed hollow, and a fixed shaft 91 fixed to the pressure distribution board 18 is inserted into the center thereof. A distribution ring 92 is fluid-tightly fitted to the left end of the fixed shaft 91, and the left end surface of the distribution ring 92 in the axial direction is eccentric so that it can come into sliding contact with the distribution plate 80.

This distribution ring 92 divides the hollow portion formed in the fourth portion 70d into an inner oil chamber and an outer oil chamber, where the inner oil chamber constitutes the first oil passage La and the outer oil chamber constitutes the first oil chamber. 2 oil passages Lb are configured. Note that the pressure distribution board 18 is connected to the shuttle valve 4.
, high pressure and low pressure relief valves 6.7, etc., are attached to the right side of the third case 5c, and
It is covered by a fourth case 5d.

A pump discharge boat and a pump suction boat are bored in the distribution board 80, and the cylinder hole 61 of the pump plunger 62 in the discharge stroke and the inner oil chamber are connected through the discharge boat and the discharge passage connected thereto. 1st oil passage La
A second oil passage Lb consisting of the cylinder hole 61 of the pump plunger 62 in the suction stroke and the outer oil chamber is communicated with the pump suction boat and the suction passage connected thereto.
is communicated. Furthermore, a communication path communicating with the cylinder hole (cylinder chamber) 71 of each motor plunger 72 is formed in the distribution panel 80, and the opening of this communication path is formed in the distribution ring 9.
2, the motor cylinder 70 communicates with the first oil passage La or the second oil passage Lb according to the rotation of the motor cylinder 70. Therefore, the cylinder hole 71 of the motor plunger 72 in the expansion stroke and the first oil passage La communicate with each other via the communication passage, and the cylinder hole 71 of the motor plunger 72 in the contraction stroke and the second oil passage Lb communicate with each other via the communication passage. Ru.

In this way, a hydraulic closed circuit is formed between the hydraulic pump P and the hydraulic motor M via the distribution panel 80 and the distribution ring 92. Therefore, when the pump cylinder 60 is driven from the input shaft 1, high-pressure hydraulic oil generated by the discharge stroke of the pump plunger 62 is transferred from the pump discharge boat to the discharge passage, the first oil passage La (inner oil chamber), and this. It flows into the cylinder hole 71 of the motor plunger 72 which is in the expansion stroke through the first communication path which is in the shape of a rod, and gives thrust to the motor plunger 72 . On the other hand, the hydraulic oil discharged by the motor plunger 72 in the contraction stroke is
It flows into the cylinder hole 61 of the pump plunger 62 in the suction stroke via the second communication path communicating with the oil path Lb (outer oil chamber), the pump suction path 82b, and the pump suction boat.

Due to this circulation of hydraulic oil, the reaction torque that the pump plunger 62 in the discharge stroke applies to the motor cylinder 70 via the pump swash plate ring 63, and the reaction torque that the motor plunger 72 in the expansion stroke receives from the motor swash plate member 73. The motor cylinder 70 is rotationally driven by the sum of .

The gear ratio of the motor cylinder 70 to the pump cylinder 60 is given by the following equation.

As can be seen from the above equation, if the swash plate member 73 is oscillated by the gear shifting servo unit 30 and the capacity of the hydraulic motor M is changed from O to a certain value, the gear ratio can be changed from 1 (minimum value) to a certain required value. (maximum value).

On the other hand, as described above, the gear member GM having the first and second drive gears is press-fitted and fixed into the fourth portion 70d of the motor cylinder 70. Therefore, the rotational driving force of the motor cylinder 70 is transmitted to the output shaft 28 via the forward/reverse switching device 20. This output shaft 28 is connected to the differential device 10 via final gear sets 28a and 29.
0, and the rotational driving force of the output shaft 28 is transmitted to the differential device 100. Then, the left and right drive shafts 1 are
The rotational driving force divided into 05.106 is applied to the left and right wheels (
(not shown) to drive the vehicle.

In addition, a short-circuit path between the first oil passage La and the second oil passage Lb is formed in the fixed shaft 91 inserted into the hollow part of the fourth portion 70d, and this short-circuit path is controlled from fully closed to fully open. A direct coupling clutch valve DC capable of controlling the main clutch valve CL1 and the first oil passage La on and off is provided.

First, the main clutch valve CL will be explained. A short-circuit port is bored in the peripheral wall of the fixed shaft 91 to allow communication between the first oil passage La and the second oil passage Lb, and a cylindrical main clutch valve body 95 is provided in the hollow portion of the fixed shaft 91. It has been inserted. The valve body 95 is rotatable relative to the fixed shaft 91, and has a short-circuit hole that can be aligned with the short-circuit port. An arm 95a formed at the right end of this valve body 95
By rotating the valve body 95, the amount of alignment (overlapping) between the shorting port and the shorting hole can be adjusted. The size of this matching part becomes the opening degree of the short-circuit passage between the first oil passage La and the second oil passage Lb, and therefore, by controlling the rotation of the valve body 95, the opening degree of the short-circuit passage is changed from fully open to fully closed. can be controlled up to. If the opening degree of the short circuit passage is fully open, the hydraulic oil discharged from the pump discharge port to the first oil passage La flows directly into the second oil passage Lb from the short circuit port and the short circuit hole, and also flows into the pump suction port. Therefore, the hydraulic motor M becomes inactive and the clutch becomes OFF. Naturally, on the contrary, if the opening degree of the short-circuit passage is fully closed, the clutch ON state is realized.

A direct coupling clutch valve DC is disposed within the hollow portion of this main clutch valve body 95. This direct-coupled Clara valve DC includes a piston shaft 85 pushed into the valve body 95 so as to be movable in the axial direction, a shoe 86 attached to the tip of the piston shaft 85, and a pilot inserted into the piston shaft 85. A pilot spool 84
By moving in the axial direction, the piston shaft 85 can be moved in the axial direction to follow this movement. For this purpose, the pilot spool 84 is moved to the left, the piston shaft 85 is moved to the left, and the shoe 86 at the tip of the pilot spool 84 is moved to the left to block the pump discharge path opening to the end surface of the distribution board 80, thereby blocking the first oil path La. is now possible. In this state where the discharge passage 81b is closed,
The pump plunger 62 is hydraulically locked, and the hydraulic pump P and hydraulic motor M are directly connected.

Note that this direct connection state is performed at the minimum gear ratio position with the swash plate member 73 of the motor M upright, that is, at the top position. In addition to improving efficiency, the thrust force exerted by the motor plunger 72 on the swash plate member 73 is reduced,
It is possible to reduce frictional resistance and reduce the load applied to bearings and the like.

Next, the gear shifting servo unit 30 will be explained with reference to FIG.

The speed change servo unit 30 is connected to a fifth servo unit into which high pressure hydraulic oil is introduced from the closed circuit of the continuously variable transmission T by the shuttle valve 4.
A housing 31 having a communication hole 31a connected to the oil passage Le
A piston member 32 is fitted into the housing 31 so as to be slidable from side to side in the figure, a valve member 33 is fixed to the piston member 32, and a valve member 33 is fixed to the piston member 32. It has a spool member 34 that is inserted and inserted so as to be slidable from side to side and a plug member 35 that is disposed on the left side of the valve member 33. Furthermore, a cover member 37 is provided at the right end of the piston member 32 to securely hold the valve member 33 in the inserted state.
7b.

The housing 31 is fixed to the pressure distribution board 18 such that its right end surface is in contact with the pressure distribution board 18. The piston member 32 includes a piston portion 32a formed at the right end portion, and a cylindrical rod portion 32b extending leftward from the piston portion 32a. The piston part 32a is
The rod portion 32b is fitted into a cylinder hole 31b formed in the housing 31 and divides the inside of the cylinder hole 3ib into two to form left and right cylinder chambers 38a and 36b. and is inserted into the idle rod hole 31c. Further, the left end of the rod portion 32b is connected to a motor trunnion 73 via a link 39, as shown in FIG.

The valve member 33 is a cylindrical member having a through hole passing through the center thereof in the axial direction. This valve member 33 is
It is inserted into the piston member 32 following the plug member 35, and is held by a cover member 37 to stop its movement in the axial direction. In this state, the left end of the through hole is closed by the plug member 35, while the right end of the through hole opens outward, and the spool member 34 is inserted into the through hole from this opening. . In this case, the through hole can be formed by processing the valve member 33 as a single unit, and the processing is easy, and it is easy to achieve high accuracy in cylindricity, straightness, etc.

The left cylinder chamber 38a is connected to the fifth oil passage Le containing high-pressure hydraulic oil via the communication hole 31a, and the piston member 32 is connected to the fifth oil passage Le introduced into the left cylinder chamber 3E3a.
It receives a pushing force to the right in the figure due to the hydraulic pressure from. Furthermore, a communication hole 32c formed to penetrate the piston member 32 in the radial direction is formed on the outer peripheral side of the left cylinder chamber 38.
a, and communicates with a first valve hole 33a formed radially through the valve member 33 on the inner peripheral side.

The spool member 34 slidably inserted into the valve member 33 is formed with a second valve hole 34a that penetrates in the radial direction and can face the first valve hole 33a as the spool member 34 slides. This second valve hole 34
a communicates with a communication hole 34b formed to extend in the axial direction within the spool member 34. The communication hole 34b opens at its left end into the space inside the valve member 33 that is closed by the plug member 35, and communicates with the right cylinder chamber 38b at its right end.

On the other hand, the valve member 33 has a ring that is closed by the outer circumference of the left end of the spool member 34 when the spool member 34 moves to the left.
A third valve hole 33b is formed which opens when the spool member 34 moves to the right and communicates with the communication hole 34b, and this third valve hole 33b extends in the axial direction from the outer peripheral groove to the piston member 32. Drain hole 32d formed by
It communicates with the drain side (oil sump 15) through.

In the shift servo unit 30 having the above configuration, the operation when the spool member 34 is moved rightward in the figure will be described. When the spool member 34 is moved to the right, the first valve hole 33
a and the second valve hole 34a are different from each other, both valve holes 33a, 34a
communication is closed. At the same time, the third valve hole 33b, which was blocked by the left end outer peripheral surface of the spool member 34, is opened. As a result, the high-pressure hydraulic oil supplied from the fifth oil passage Le through the communication hole 31a acts only on the left cylinder chamber 36a, and the hydraulic oil in the right cylinder chamber 36b acts on the spool member 3.
The liquid is discharged to the drain side through the communication hole 34b1 formed in the third valve hole 33b and the drain hole 32d formed in the piston member 32. As a result, the piston member 32 moves to the right to follow the spool member 34 in response to the hydraulic pressure acting on the left cylinder chamber 36a.

Contrary to the above case, when the spool member 34 is moved to the left, the first and second valve holes 33a and 34a match and the third valve hole 33b is completely closed, so that the left and right cylinders The oil pressures in chambers 36a and 36b are approximately equal. The pressure receiving area of the piston portion 32a is different (the area receiving the hydraulic pressure from the right cylinder chamber 36b is larger)
Therefore, the piston member 32 receives a pushing force to the left, and the piston member 32 follows the spool member 34 and moves to the left.

In addition, due to the relationship between the matching areas of the first and second valve holes 33a, 34a and the opening amount of the third valve hole 33b, a hydraulic pressure difference is created so that the left and right hydraulic pressures acting on the piston portion 32a are equal. Furthermore, there is a relative position of the piston member 32 with respect to the spool member 34. Therefore, when the spool member 34 is stopped midway, the piston member 32 follows and moves to this relative position with respect to the spool member 34, and is maintained in a hydraulic floating state at this relative position.

Therefore, when the spool member 34 is moved in the left-right direction, the piston member 32 moves to follow the spool member 34 so as to be located at the relative position L with respect to the spool member 34. That is, by moving the spool member 34 left and right, the piston member 32 can be moved to follow the spool member 34 using the hydraulic pressure of the high-pressure hydraulic oil from the fifth oil passage Le, and thereby the link 39
The trunnion 73 of the hydraulic motor M connected to the piston member 32 via the piston member 32 can be rotated about its trunnion shaft 73a to variably control its displacement.

The right end portion of the spool member 34 is connected to the first link member 41 of the link mechanism 40 . The link mechanism 40 also has a second link member 42 that is swingable about a shaft 42b, and the first link member 41 is connected to the arm 42a of the second link member 42. Therefore, by rotating the second link member 42 around the shaft 42b, the spool 34
It is designed to move left and right.

The second link 42 is swung from the illustrated position to the position indicated by the two-dot chain line. In the illustrated state, the piston member 32 has been moved to the leftmost position, the swash plate angle of the motor M is at its maximum, and the gear ratio of the transmission T is also at its maximum, and this is swung to the position indicated by the two-dot chain line. As a result, the motor swash plate angle and gear ratio are changed to minimum values.

As described in detail, according to the present invention, the swash plate control servo unit is provided in the cylinder housing fixed to the case of the continuously variable transmission, and in the cylinder housing in which the swash plate control servo unit is movable in the axial direction. a cylindrical valve member having an insertion hole passing through it in the axial direction and being fitted and held within the piston member; and insertion of this valve member. The spool member is inserted into the hole so as to be movable in the axial direction, and the hydraulic pressure supply to the left and right cylinder chambers in the cylinder housing is switched and controlled according to the axial movement of the spool member in the insertion hole. The piston member is moved to follow the spool member to control the swinging of the swash plate. In this case, the insertion hole into which the spool member is inserted is formed in the valve member fitted and held by the piston member, and this insertion hole is a through hole formed in the valve member. Therefore, the insertion hole can be machined through the valve member before it is inserted into the valve member, which facilitates the process and allows highly accurate cylindricity, straightness, etc. to be obtained.

Therefore, the spool member can be smoothly moved in the axial direction within the through-insertion hole, and the piston member is moved in the axial direction following the movement of the spool member, thereby controlling the swinging of the swash plate. Sometimes, this swing control can be performed accurately.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram of a continuously variable transmission equipped with a servo unit according to the present invention, FIG. 2 is a sectional view of the continuously variable transmission, and FIG. 3 is a sectional view of the servo unit. 4... Shuttle valve 10... Charge pump 18... Pressure distribution panel 20... Forward/forward switching device 30... Servo unit for speed change

Claims (1)

[Scope of Claims] 1) Consisting of a swash plate type hydraulic pump driven by an engine and a swash plate type hydraulic motor driven by hydraulic pressure from the hydraulic pump, at least one of the hydraulic pump and the hydraulic motor A hydraulic continuously variable transmission that performs speed change control by variable rocking control of a swash plate includes a cylinder housing fixed to a case of the continuously variable transmission, and a cylinder housing that is movable in the axial direction within the cylinder housing. a piston member inserted and connected at one end to the swash plate;
and a spool member disposed within the piston member so as to be movable in the axial direction.According to the axial movement of the spool member, the piston member provides access to the left and right cylinder chambers divided into left and right cylinder chambers within the cylinder housing. A swash plate control servo unit that controls the swinging of the swash plate by switching and controlling hydraulic pressure supply and moving the piston member to follow the spool member, the servo unit having a through hole extending in the axial direction. A cylindrical valve member is fitted and held within the piston member, and the spool member is inserted into the through hole, and movement within the through hole causes the spool to move in the axial direction within the piston member. A swash plate control servo unit for a hydraulic continuously variable transmission.