JPH11287341A - Relief valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the line pressure from changing by allowing two hydraulic forces to cancel each other, which act when the working oil passes two valve opening parts. SOLUTION: The B1 chamber as the first chamber always in communication with the inlet port P of a relief valve 40 connected with the discharge line of an oil pump can be put in communication with the first outlet port R1 via the first valve opening part 48A. The inlet port P can be put in communication with the B2 chamber as the second chamber via the second valve opening part 48B. When the working oil passes the valve opening parts 48A and 48B, the forces F1 and F2 generated in a spool valve 44 owing to unbalance of the pressures in the B1 and B2 chambers act in such directions as to cancel each other. Thus the line pressure P'L of the relief valve 40 can be stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relief valve for obtaining a constant line pressure in a hydraulic line in a discharge circuit or the like of an oil pump.

[0002]

2. Description of the Related Art Conventionally, particularly in a vehicle, a hydraulic system as shown in FIG. 4 is used. In this hydraulic system, an oil pump 30 is a pump driven by an engine, pumps oil from a reservoir 31 and supplies the oil to a hydraulic line 32 as a main line. The oil supplied by the oil pump 30 is supplied to each device mounted on the vehicle through each line branched from the hydraulic line 32. In the illustrated hydraulic system, the oil supplied to the hydraulic line 32 is supplied to the torque converter pilot valve 33 through a line 32d. The torque converter pilot valve 33 is a spool valve that feeds back the outlet pressure to the displacement of the spool. The torque converter pilot valve 33 obtains a constant outlet pressure from the line pressure of the hydraulic line 32 and supplies a constant pressure oil to the lock-up control valve 3.
4 to the torque converter 35 to control the direct connection of the torque converter 35. Lock-up control valve 34
Is supplied to the cooling / lubricating system circuit 36. The hydraulic line 32 is also connected to a manual valve 37 through a line 32b, and is selectively supplied to a hydraulic actuator 38 or 39 by operating the manual valve 37. Hydraulic line 32
Is further connected to a transmission hydraulic actuator 12 for driving a trunnion 9 of a toroidal type continuously variable transmission (to be described in detail later) through a line 32a. As described above, the oil pump 30 is used as a hydraulic pressure source of an automatic transmission for a vehicle (a toroidal-type continuously variable transmission).

The hydraulic oil discharged from the oil pump 30 is supplied to a pilot valve 51 through a hydraulic line 50 and also to each device 52 requiring lubrication of the vehicle as lubricating oil. It is released to the reservoir 31 through 53. The pilot valve 51 is a spool valve that feeds back its own discharge pressure to the displacement of the spool.
The pressure is reduced to a constant pressure Pp set by a spring, and the constant pressure Pp is supplied to each of the solenoid valves 23A to 23D through a constant pressure line 54. Each of the solenoid valves 23A to 23D converts the pilot pressure of the constant pressure line 54 into an arbitrary control pressure from 0 to the pressure Pp by a solenoid operated in accordance with a control signal from the controller 24. An arbitrary pilot pressure obtained in this manner is supplied to a lock-up control valve 34 for a torque converter 35, a manual valve 37 for hydraulic actuators 38 and 39, and a spool as a transmission ratio control valve of a toroidal type continuously variable transmission. It is used for controlling the valve 18.

[0004] In the above-mentioned conventional hydraulic system, the oil pump 30 is directly connected to the engine crankshaft or mechanically connected via a gear, so that the rotation speed is the same as or proportional to the engine rotation speed. Therefore, it fluctuates greatly depending on the operating state of the engine and is not always constant. In some cases, variable displacement vane pumps are used. However, fixed displacement gear pumps and the like, which have fewer parts than variable displacement vane pumps and are advantageous from the viewpoint of cost and maintenance, are also available. Trochoid pump
Widely used. However, the discharge flow rate of the fixed displacement pump varies by about 6 to 10 as a ratio from the idle operation state of the engine to the maximum rotation state. In view of this, a hydraulic circuit is configured to release or circulate a part of the discharge flow rate of the fixed displacement pump, so that output fluctuation is devised. On the other hand, the side that uses the hydraulic oil supplied by the oil pump 30 such as an actuator also greatly changes according to the use state of the equipment mounted on the vehicle. Therefore, as it is, the hydraulic line 3
2, the line pressure PL greatly fluctuates.

[0005] An oil pump 30 whose discharge amount fluctuates greatly according to the operating state of an engine or the like is used, and a hydraulic line 3
In the hydraulic system in which the consumption of oil passing through the oil pump 2 fluctuates greatly, a relief valve as a pressure control valve is connected to a line 32c branched from the hydraulic line 32 in order to release a part of the oil discharge amount of the oil pump 30 to the reservoir 31. 40 are connected. The relief valve 40 has a solenoid valve 23
Since the hydraulic pressure controlled by the control signal input to C is supplied through the control pressure line 59c, the relief valve 4
0 is controlled so that the maximum pressure of the line pressure PL of the hydraulic line 32 becomes a value corresponding to the control oil pressure.

An example of a conventional line pressure relief valve 40 is shown in FIG. The line pressure relief valve 40 shown in FIG.
A has a large diameter hole 42 and a small diameter hole 43 formed in a valve case 41, and the large diameter hole 42 has a large diameter portion 45 of a spool 44A.
a and 45b are slidably fitted, and the small-diameter hole 43 is slidably fitted with the small-diameter portion 45c of the spool 44A. In FIG. 2, the room A is on the left side of the large diameter portion 45a, the room C is on the right side of the large diameter portion 45b, and the space D is between the large diameter portions 45a and 45b.
A chamber is formed. The chamber A is connected to the pilot control pressure line 59c through the control port F, and the pilot control pressure Pmf controlled by the solenoid valve 23C acts on the chamber A. That is, the first end of the spool 44A receives the pilot control pressure Pmf in the chamber A and applies a spring force to the spool 44A.
A first pressure-receiving surface 47a with which the first pressure-receiving surface 9 engages is formed. The C room is a hydraulic line 32 through the inlet port P and the line 32c.
And the line pressure PL is acting on the C chamber. That is, a second pressure receiving surface 47c on which the line pressure PL in the C chamber acts is formed at the second end of the spool 44A. The chamber D is also connected to the hydraulic line 32 through the inlet port P and can be connected to the reservoir 31 through the port R. Spool 44 constituting room D
The areas of the axially projected surfaces of the pressure receiving surfaces 47d and 47e of A are formed to be equal.

The hydraulic oil discharged from the oil pump 30 flows into the C chamber and the D chamber.
Since the area of the projection surface in the axial direction of e is equal, the forces by the hydraulic oil are balanced. Eventually, the line pressure PL acting on the pressure receiving surface 47c of the chamber C receives a leftward force Fc in the figure.
On the other hand, the spool 44A receives a force Fa in the right direction in the drawing by the force based on the pilot control pressure Pmf acting on the pressure receiving surface 47a of the chamber A and the spring force of the setting spring 49. If Fc> Fa, the spool 44A moves leftward in the drawing, and the valve opening 48a that opens and closes the D chamber and the port R is opened. When the spool valve 44A opens, the hydraulic oil in the D chamber starts to be discharged to the reservoir 31, and the line pressure PL decreases. When the line pressure PL decreases, the leftward force Fc decreases, and the line pressure PL is adjusted so that Fc balances Fa.
Is determined. The balance equation (1) at this time is PL × A
c = Pmf × Aa + Fs (where Aa and Ac are the areas of the pressure receiving surfaces 47a and 47c of the spool 44A receiving the pressure of the hydraulic oil in the chambers A and C, respectively, and Fs is the spring force of the spring 49 at the balance point. is there). By controlling the magnitude of the pilot control pressure Pmf to the chamber A, the magnitude of the line pressure PL can be controlled.

In this case, when the drive shaft of the oil pump is driven at a high speed, that is, when the discharge flow rate of the oil pump 30 is large, most of the oil is discharged through a drain circuit including a relief valve 40A. , As this emission increases, in addition to the above balancing equation (1),
The fluid force Ff according to the equation (2) acts on the spool 44A, and the predetermined line pressure PL cannot be obtained. Ff = 2Cd × π × D × χ × PLcosθ (where Cd is a flow coefficient (about 0.
7), D is the spool diameter, χ is the valve opening degree (a function of flow rate and PL) of the valve opening portion 48a, and θ is the jet angle (69 degrees when the flow rate is sufficiently large). )

The above-mentioned fluid force is applied to the relief valve 40 shown in FIG.
In the case of A, the pressure acting on the left wall surface where the valve opening 48a is formed in the D chamber decreases near the outer periphery of the spool 44A due to the flow of hydraulic oil flowing through the valve opening 48a.
The balance with the pressure acting on the right wall surface is lost, and a net rightward force is generated on the spool 44A. Therefore, the port R is in the closing direction, and the valve opening 48a does not open unless the line pressure PL acting on the chamber C becomes higher. Therefore, the line pressure PL becomes equal to the hydraulic pressure F of the working oil.
The line pressure PL is adjusted to a higher pressure than when f does not act on the spool 44A.

In addition to the relief valve 40A shown in FIG. 2, a relief valve 40B shown in FIG. 3 is also conceivable. The relief valve 40B is basically configured such that the valve opening 48b is formed between the inlet port P and the E chamber, that is, on the side where the hydraulic oil of the line pressure PL enters the E chamber. Elements and portions that are basically equivalent to the relief valve 40A shown in FIG. 2 and have corresponding equivalent functions are assigned the same reference numerals.
In the case of the relief valve 40B, if Fc> Fa, the valve opening 48b is opened at the point where Fc and Fa are balanced so that the line pressure PL balances the force of the setting spring 49 and the force of the pilot control pressure Pmf. It is determined. Since the pressure acting on the left side wall 47d in the E chamber increases near the outer periphery of the spool 44B due to the fluid force passing through the valve opening 48b, the balance with the pressure (= 0) acting on the right side wall 47e is lost, and A force is generated at 44B, which is a net leftward force in the figure. Accordingly, the direction between the inlet port P and the chamber E is open, and the valve opening 48b is opened at a lower pressure of the line pressure PL acting on the chamber C. Therefore, the line pressure PL is increased by the hydraulic oil. The pressure is adjusted to a lower pressure than when the hydraulic pressure Ff does not act on the spool 44B.

A spool for slidably connecting or disconnecting the primary passage and the secondary passage is slidably fitted in a fitting hole formed in the valve body, and the pressure of the primary passage acting on the spool is adjusted by a spring. For example, Japanese Patent Application Laid-Open No. 3-213778 discloses a pressure control valve configured so that the primary passage is connected to the secondary passage when the pressure exceeds a value corresponding to the force set by the pressure control device. The oil pump discharge pressure is fed back to the spool. When the oil pump pressure increases, the spool moves in a direction to open the valve opening in response to the pressure, and the amount of oil drain from the valve opening increases. The oil pump pressure is reduced by increasing the pressure, and when the oil pump pressure is reduced, the spool moves in a direction to close the valve opening in response to the pressure, and the amount of oil drain from the valve opening decreases. Japanese Patent Laid-Open No. 6-93 discloses a relief valve which raises the oil pump pressure to thereby adjust the oil pump pressure to a predetermined pressure, in order to prevent the fluctuation of the pressure adjustment value due to the fluid force (flow force).
No. 977 discloses this. Fluid force is the force acting on the spool in a direction that opposes the feedback pressure by increasing the flow between the edge of the land of the spool and the wall of the valve body. As the flow rate of the oil pump discharge circuit increases, the pressure adjustment value of the relief valve tends to increase due to the fluid force. In the relief valve disclosed in the above-mentioned Japanese Patent Application Laid-Open No. Hei 6-93977, the influence of the fluid force is reduced by applying a negative suction pressure of the oil pump to the spool.

[0012]

As described above, the line pressure PL is adjusted to a predetermined pressure under the influence of the oil pressure flowing through the valve opening between the edge of the spool land and the wall of the valve case. When the pressure of the line pressure PL drops, the hydraulic pressure to be supplied to the clutch inside the transmission is insufficient and slippage occurs.
When the pressure of the line pressure PL increases, there is a problem that power loss in the oil pump increases. In particular, like a toroidal type continuously variable transmission, the position of the trunnion in the tilt axis direction is controlled by the hydraulic pressure of a hydraulic actuator to which hydraulic oil is supplied from an oil pump as a hydraulic power source, thereby controlling the gear ratio. In this case, the amount of oil consumed through the gear ratio control valve changes greatly in accordance with the shifting operation, so that the flow rate discharged by the relief valve also changes. As a result, even if the engine speed is constant, There is a serious problem that the line pressure PL fluctuates and a stable gear ratio cannot be obtained.

As described above, the spool is prevented from moving under the influence of the above-mentioned oil pressure generated when the pressure oil passes through the valve opening formed between the valve case and the land of the spool. desirable. Since it is difficult to completely prevent hydraulic pressure from being generated completely, the net effect on the spool is minimized by applying and canceling the hydraulic pressure generated at two points in directions opposite to each other. Therefore, there is a problem to be solved in that the spool is not affected immediately even when the hydraulic pressure is generated.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and by providing two valve opening portions,
The net effect on the spool is reduced as much as possible by acting the oil pressures generated at the respective valve openings in directions opposite to each other, thereby reducing the line pressure fluctuation caused by the oil pressure acting on the spools. It is to provide a relief valve that can be prevented.

The present invention provides a valve case having a hollow hole, an inlet port connected to a hydraulic line, and an outlet port connected to a drain line, and a line pressure of the hydraulic line and the hydraulic line. A valve opening portion provided between the valve case and the spool and connecting the inlet port and the outlet port, the valve opening portion including a spool accommodated in the hollow hole so as to be displaceable based on a deviation from the set pressure. The relief valve is configured to maintain the line pressure at the set pressure by opening and closing the valve by the displacement of the spool, wherein the outlet port includes a first outlet port and a second outlet port, and the valve opening portion includes: A first valve opening connecting the inlet port to the first outlet port and a second valve opening connecting the inlet port to the second outlet port; There about a relief valve, wherein the oil pressure generated in the spool is offset with each other when flowing through the second valve opening portion and the first valve open part.

In this relief valve, the spool partitions the hollow hole to form at least a first chamber and a second chamber. The first chamber is always in communication with the inlet port and the first chamber is connected to the first port. The first chamber communicates with the first outlet port through one valve opening, and the second chamber communicates with the inlet port through the second valve opening and always communicates with the second outlet port.

Further, in this relief valve, a first pressure receiving surface on which a set spring is engaged and a pilot control pressure acts to form the set pressure is formed at a first end of the spool. A second pressure receiving surface on which the line pressure acts is formed at a second end of the spool.

In the relief valve, the hydraulic line is a discharge line of a fixed displacement oil pump or a variable displacement oil pump.

In this relief valve, the relief valve is applied to a transmission hydraulic line as the hydraulic line connected to a transmission hydraulic cylinder of a toroidal type continuously variable transmission. An input disk and an output disk disposed in opposition to each other; a pair of power rollers for continuously changing the rotation of the input disk according to a tilt angle with respect to the two disks and transmitting the rotation to the output disk; A trunnion rotatably supporting each of the power rollers and rotating about the tilt axis by being displaced in the tilt axis direction by the operation of the shift hydraulic cylinder; Two cylinder chambers that operate by being supplied with line pressure of the shift hydraulic line through a valve;
Each of the cylinder chambers is cut off from the transmission hydraulic line when the transmission ratio control valve is in the neutral position, and the respective cylinder chambers are disconnected from the transmission hydraulic line when the transmission ratio control valve is displaced from the neutral position. And selectively communicating with the reservoir.

According to the relief valve of the present invention, the outlet port is configured as two outlet ports of the first outlet port and the second outlet port, and the valve opening connects the inlet port to the first outlet port. A valve opening, and a second valve opening connecting the inlet port to the second outlet port. When the hydraulic oil flows through the first valve opening and the second valve opening, the hydraulic pressure exerted on the spool is mutually controlled. Since they are made to act in opposite directions to cancel each other, it is possible to prevent the line pressure from fluctuating due to the oil pressure acting on the spool at the valve opening.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view showing an embodiment of the relief valve according to the present invention. The relief valve according to the present invention can be incorporated in a hydraulic system shown in FIG. 4 as an example.

In FIG. 1, the same components as those used in the conventional relief valve shown in FIGS. 2 and 3 are denoted by the same reference numerals as those in FIG. 2 or FIG. explain. The pressure relief valve 40 shown in FIG.
A large-diameter hole 42 and a small-diameter hole 43 are formed in the valve case 41, and large-diameter portions 45 a and 45
The small diameter portion 45c of the spool 44 is slidably fitted in the small diameter hole 43. FIG.
A room is formed on the left side of the large diameter portion 45a, a C room is formed on the right side of the small diameter portion 45c, and a B1 room is formed as a first room between the large diameter portions 45a and 45d. , 45b, a B2 chamber as a second chamber is formed. A room is connected to the control pressure line 5 of the solenoid valve 23C through the control port F.
9c (see FIG. 4), and the pilot control pressure Pmf acts on the A chamber. Chamber C is connected to hydraulic line 32 through inlet port P and line 32c (see FIG. 4).
Therefore, the line pressure PL is acting on the C chamber.
Room B1 also has hydraulic line 3 through inlet port P.
2 and the line pressure PL is acting.
The chamber is connectable to the reservoir 31 through a second outlet port R2. That is, the room B1 has the same function as the room D shown in FIG. 2, and the room B2 has the same function as the room E shown in FIG. A first valve opening 48A (having the same function as the valve opening 48a shown in FIG. 2) is formed between the chamber B1 and the first outlet port R1, and a first valve opening 48A is provided between the inlet port P and the chamber B2. 2 valve opening portion 48B (the valve opening portion 48b shown in FIG. 3)
Having the same function as described above). The spool 4
The large-diameter portion 45a of 4 is a first end portion, and the end surface thereof is a first pressure receiving surface 47a on which a setting spring 49 is engaged and a pilot control pressure is applied. The large-diameter portion 45b of the spool 44 is a second end, and the end surface thereof has a line pressure PL.
Is formed on the second pressure receiving surface 47b.

In FIG. 1, when the amount of discharge from the relief valve 40 is small and the hydraulic pressure can be ignored,
Is determined by equation (1) as in the conventional case. When the amount of oil discharged through the relief valve 40 is large, the chamber B1 is the same as the chamber D in FIG.
Since the pressure acting on the left wall surface 47d when the hydraulic oil passes through 8A decreases near the outer periphery of the large diameter portion 45a of the spool 44, the spool 44 has a net pressure due to imbalance with the pressure acting on the right wall surface 47e. As a result, a force F1 toward the right side of the figure is generated. Similarly, in the chamber B2, when the hydraulic oil passes through the valve opening 48B, the pressure acting on the left wall surface 47f becomes higher than the pressure acting on the right wall surface 47g (gauge pressure = 0). And force F2 toward the left side of the figure
Occurs. In this case, since the flow rate of the hydraulic oil discharged from the relief valve 40 is shared between the chambers B1 and B2, the valve opening に お け る in the equation (2) is reduced, and the magnitudes of the forces F1 and F2 are as shown in FIGS. It is smaller than the fluid forces Fa and Fc generated in FIG. Further, since the forces F1 and F2 are generated in directions opposite to each other, the forces F1 and F2 are canceled and the force exerted on the spool 40 becomes very small. Therefore, the line pressure PL is not affected by the flow rate discharged by the relief valve 40, and the line pressure PL is stably regulated to a predetermined pressure.

When a toroidal type continuously variable transmission is mounted on a vehicle as an automatic transmission, the hydraulic line 32 is used as a transmission hydraulic line. During operation of the toroidal-type continuously variable transmission, a tangential force is constantly applied to the power roller from the input disk and the output disk, and the tangential force is opposed to the power roller. There is a certain pressure difference between both cylinder chambers. When changing the gear ratio, it is necessary to change the piston position of the hydraulic actuator by supplying hydraulic pressure in consideration of the pressure difference. Accordingly, the hydraulic pressure for shifting is supplied from the hydraulic pressure line 32 having a large hydraulic pressure, which is the discharge line of the oil pump. If the line pressure of the hydraulic line fluctuates, the hydraulic pressure applied to the hydraulic actuator of the toroidal-type continuously variable transmission cannot be accurately controlled, and the position of the trunnion cannot be accurately determined, and a predetermined gear ratio cannot be obtained. There is a problem.

FIGS. 5 and 6 respectively show an example of a toroidal-type continuously variable transmission and an outline of its gear ratio control. The toroidal type continuously variable transmission 1 shown in FIG. 5 is arranged opposite to the input disk 4, which is rotatably supported with respect to the input shaft 2 to which the output of the engine E is input, and the input shaft 2. Output disk 5, which is rotatably supported with respect to input shaft 2, disposed between input disk 4 and output disk 5 opposed to each other, and can be tilted to transmit torque from input disk 4 to output disk 5. And a load roller disposed between the input disk 4 and the flange portion 7 provided on the input shaft 2 and acting on the input disk 4 to change the pressing force of the power roller 6 in accordance with the magnitude of the input torque. A pressing means 8 such as a cam is provided, and by rotating the power roller 6 around the tilt axis 11, the rotation of the input disk 4 according to the tilt angle .theta. It is configured to shift to transmission steplessly. When the power roller 6 tilts as shown in the figure, the frictional contact position of the power roller 6 with the input disk 4 becomes the position of the radius r ₁ , and the frictional contact position with the output disk 5 becomes the position of the radius r ₂ . The gear ratio between the input and output disks is r ₁ / r ₂ . The member denoted by reference numeral 9 is a trunnion that supports the power roller 6 in a tiltable manner, and will be described later in detail. Also, between the other transmission unit, the pair of output disks 5 are integrally connected by a connecting member (not shown), and output torque to the output shaft 3. The toroidal-type continuously variable transmission 1 mounted on an automobile is generally a double-cavity toroidal-type continuously variable transmission 1 in which two transmission units are arranged on the same shaft.

The tilt control of the power roller 6 of the toroidal type continuously variable transmission 1 is controlled as follows. FIG. 6 shows a control system of the toroidal type continuously variable transmission 1. As shown, a pair of power rollers 6 are arranged opposite to each other so as to be sandwiched between an input disk 4 and an output disk 5 (not shown in FIG. 6) which are arranged opposite to each other. It is rotatably supported by the trunnion 9. The power roller 6 has an eccentric shaft 1 with respect to the trunnion 9.
Supported by 0. Each trunnion 9 is supported by a casing 29 of the transmission so as to be rotatable and movable in the axial direction. That is, each trunnion 9
Is movable in the axial direction of its own tilting shaft 11 and is rotatable about the tilting shaft 11. Trunnion 9
A hydraulic actuator 12 is disposed on the tilting shaft 11 of the vehicle. The hydraulic actuator 12 is fixed to the hydraulic cylinder chambers 13A and 13B (generally referred to as 13) formed in the casing 29 and the traniton 9. And a piston 14 slidably provided in the hydraulic cylinder chamber 13. The hydraulic cylinder chamber 13 holds the piston 1
The cylinder chamber is divided into two cylinder chambers, namely, a speed increasing cylinder chamber 13A and a decelerating cylinder chamber 13B.

Each of the cylinder chambers 13A of the hydraulic cylinder 13
13B communicates with the spool valve 18 through oil passages 17A and 17B. A spool 21 slidably disposed in the spool valve 18 is held at a neutral position by springs 22 disposed at both ends in the axial direction. The spool valve 18 has an Sa port at one end, an Sb port at the other end, and a hydraulic pressure P at the Sa port via a solenoid valve 23C.
a is supplied, and the hydraulic pressure Pb is supplied to the Sb port via the solenoid valve 23D. The spool valve 18 has a PL port communicating with the hydraulic line 32, an A port communicating with the speed increasing side cylinder chamber 13A via the oil passage 17A, and an oil passage 17B.
B port communicating with the deceleration side cylinder chamber 13B through the
It has two R ports that communicate with the reservoir. The solenoid valves 23C and 23D are configured to operate according to a control signal output from the controller 24. The spool valve 18 and the solenoid valves 23C and 23D
The transmission ratio control valve of the toroidal-type continuously variable transmission 1 is configured.

A precess cam 15 is connected to the tip of the tilting shaft 11, and one end of a lever 16 pivotally connected to the center portion contacts the precess cam 15, and the other end of the lever 16 contacts the spool 21 of the spool valve 18. ing. Precess cam 15
Is displaced in accordance with the axial displacement Y of the tilt shaft 11 of the trunnion 9 and is also displaced in accordance with the displacement angular displacement θ, so if both displacements are present, the combined displacement of the two displacements The amount will be detected. The spool 21 is displaced inside the spool valve 18 in accordance with the resultant displacement. The spool valve 18 has a sleeve 19 which is slidably disposed in the valve case and into which a spool 21 is slidably fitted.

Detection signals from various sensors such as an engine speed sensor 25 and an accelerator pedal depression amount sensor 26 are input to the controller 24. Controller 2
Reference numeral 4 calculates a target gear ratio based on a gear shift information signal such as an engine speed and an accelerator pedal depression amount detected by these sensors, and outputs a control signal to the solenoid valves 23C and 23D. The output shaft speed sensor 25 is a vehicle speed sensor, and the accelerator pedal depression amount sensor 26
May be a throttle opening sensor. Sleeve 19
Corresponds to the solenoid valve 23C,
The position is shifted to a position where the oil pressure based on the output pressure output by 23D and the spring 20 are balanced.

The position of the spool 21 is feedback-controlled so as to match the position of the sleeve 19. That is, in the toroidal-type continuously variable transmission 1, when the trunnion 9 is displaced in the tilt axis direction from the neutral position to either one (that is, the axial direction of the tilt shaft 11), the direction according to the direction and the amount of displacement. By using the property that the trunnion 9 tilts around the tilt shaft 11 at a high speed, the shift control is performed by controlling the tilt. Specifically, the spool 21 and the sleeve 19
The hydraulic pressure of the hydraulic line 32 that has entered the PL port depends on the relative position of the hydraulic cylinder 13 to the speed increasing side cylinder chamber 1 of the hydraulic cylinder 13.
3A or selectively supplied to the deceleration side cylinder chamber 13B,
The position of the trunnion 9 in the direction of the tilt axis 11 is controlled. When the axial position Y of the tilt shaft 11 of the trunnion 9 changes, the friction contact points between the power roller 6 rotatably supported by the trunnion 9 and the input disk 4 and the output disk 5 are changed. A tilting force is generated around the rotation axis 11. The precess cam 15 detects the combined displacement amount of the displacement amount Y of the trunnion 9 in the direction of the tilt axis 11 and the displacement θ in the rotation direction. The detected combined displacement is
This corresponds to the current information of the gear ratio, and is converted into the displacement of the spool 21 of the spool valve 18 via the lever 16.

First, the controller 24 calculates a target speed ratio based on the speed change information, and calculates the port Sa,
The duty (C) and dutyD to be output to the solenoid valves 23C and 23D are calculated so that the pressure difference ΔP between the pressures Pa and Pb acting on Sb is proportional to the target gear ratio. Duty is ON in pulse width modulation control
And OFF time ratio. That is, duty (%) is given by the following equation. duty = (one cycle of solenoid ON time / solenoid operation cycle) × 100 Next, dutyC and dutyD are output to the solenoid valves 23C and 23D, respectively. The sleeve 19 of the spool valve 18 moves to a position where it is balanced by receiving the differential pressure ΔP and the spring force of the springs 20 disposed at both ends of the sleeve 19. That is, the displacement of the sleeve 19 is proportional to the target gear ratio.

For example, when the speed is to be shifted to the speed increasing side when the trunnion 9 is at a certain neutral position, the calculated duty C and duty D are determined by the solenoid valves 23C, 2C.
As a result of the output to 3D, the relationship between the oil pressure Pa and the oil pressure Pb acting on both ends of the spool valve 18 becomes a relationship Pa> Pb, and the sleeve 19 moves to the right in the figure. The oil passage 17B communicates with the hydraulic line 32 via the PL port.
A communicates with the reservoir via the R port, and oil passage 17B
Is higher than the pressure Pd of the oil passage 17A (Pu> Pd). As a result, the cylinder chambers 13A, 13B
6, the trunnion 9 in FIG. 6 is displaced in the negative direction of the displacement axis direction Y, that is, the left trunnion 9 is displaced upward, and the right trunnion 9 is displaced downward. Since the tilt axis displacement Y is negative (Y <0), the tilt angle displacement θ of the power roller 6 is negative (θ <0) due to the tilt characteristics of the power roller 6 (speed increasing side). The heft trunnion 9 starts to tilt, and the speed change operation to the speed increasing side is started. As described above, the tilt characteristic of the power roller 6 is such that the displacement of the tilt angle is caused by the displacement of the trunnion 9 in the axial direction of the tilt shaft 11, so that the displacement amount Y of the trunnion 9 in the tilt axis direction is changed. The combined displacement of the power roller 6 and the tilt angle displacement θ of the power roller 6 is detected by the
Is displaced so as to follow the sleeve 19.

When the trunnion 4 continues to be tilted, the spool 21 is displaced to the right, the relative position with respect to the sleeve 19 changes, and the pressure Pa of the oil passage 17A and the oil passage 17B, the direction of the tilt axis displacement Y of the trunnion 9 changes. When the tilt axis displacement Y becomes a positive value, the trunnion 9 tilts to the deceleration side, and the above shifting operation is repeated. The speed ratio converges to the target speed ratio. At that time, the displacement amount Y of the trunnion 4 in the tilt axis direction is also zero, and the shift operation ends. At this time, the positions of the spool 21 and the sleeve 19 are aligned, and the supply of hydraulic oil to the hydraulic actuator 12 is stopped.
In this case, a small change in the pressure of the hydraulic oil applied to the hydraulic actuator 12 leads to a stable shift operation. At the time of the shifting operation, it is necessary to supply the hydraulic pressure necessary for shifting from the line pressure of the hydraulic line 32 to the hydraulic actuator 12 together with the force opposing the tangential force between the input disk 4 and the power roller 6 and the output disk 5 and the power roller 6. There is
When the pressure of the line pressure PL is stable, the axial displacement of the tilt shaft 11 of the trunnion 9 does not change except for the gear required for shifting, and a stable shifting operation can be obtained.

[0034]

The relief valve according to the present invention is configured as described above, and has the following effects. That is, since the flow rate discharged at each valve opening is approximately half as compared with the conventional relief valve, the absolute value of the generated fluid force itself is reduced, and the hydraulic oil passes through each valve opening. The resulting hydraulic pressures are offset because they face in opposite directions, and the effect on the balance of the spool is reduced to a virtually negligible effect. Therefore, the line pressure of the hydraulic line, which is the discharge line of the oil pump, becomes less affected by the oil pressure flowing through the valve opening between the edge of the spool land and the wall of the valve case. Is regulated. As a result, the line pressure is adjusted to a low pressure and the hydraulic pressure to be supplied to the clutch inside the transmission is insufficient, causing slippage. This also means that the line pressure is adjusted to a high pressure and the power loss in the oil pump increases. There is no problem such as doing. In particular, like a toroidal type continuously variable transmission, the position of the trunnion in the tilt axis direction is controlled by the hydraulic pressure of a hydraulic actuator to which hydraulic oil is supplied from an oil pump as a hydraulic power source, thereby controlling the gear ratio. In this case, even if the amount of oil consumed through the gear ratio control valve changes greatly in accordance with the shifting operation,
The pressure is adjusted to an appropriate pressure by the relief valve, and a stable gear ratio can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a relief valve according to the present invention.

FIG. 2 is a sectional view showing an example of a conventional relief valve.

FIG. 3 is a sectional view showing another example of a conventional relief valve.

FIG. 4 is a schematic diagram of a hydraulic system that uses an oil pump as a hydraulic pressure source and supplies hydraulic pressure to a load including a toroidal-type continuously variable transmission.

FIG. 5 is a schematic diagram showing an example of a toroidal-type continuously variable transmission including a speed ratio control mechanism.

FIG. 6 is a diagram showing an example of a control system of the toroidal-type continuously variable transmission shown in FIG.

[Explanation of symbols]

 Reference Signs List 1 relief valve 2 input shaft 3 output shaft 4 input disk 5 output disk 6 power roller 9 trunnion 11 tilting shaft 12 hydraulic actuator 13A, 13B hydraulic cylinder chamber 18 spool valve 30 oil pump 31 reservoir 32 hydraulic line 40 relief valve 41 valve case 42 Large-diameter hole 43 Small-diameter hole 44 Spool 47a First pressure-receiving surface 47c Second pressure-receiving surface 48A First valve opening 48B Second valve opening 49 Setting spring θ Tilt angle P Inlet port R1 First outlet port R2 Second outlet Port B1 First chamber B2 Second chamber F Control port Pmf Pilot control pressure PL Line pressure

Claims (5)

[Claims] 1. A valve case in which a hollow hole is formed and an inlet port connected to a hydraulic line and an outlet port connected to a drain line are formed, and the line pressure of the hydraulic line and the setting of the hydraulic line A spool accommodated in the hollow hole so as to be displaceable based on a deviation from pressure.
Maintaining the line pressure at the set pressure by opening and closing a valve opening formed between the valve case and the spool and connecting the inlet port and the outlet port by displacement of the spool. In the relief valve, the outlet port includes a first outlet port and a second outlet port, and the valve opening unit connects the first valve opening unit that connects the inlet port to the first outlet port and the inlet port. A second valve opening connected to a second outlet port, wherein hydraulic pressures generated in the spool when the pressure oil flows through the first valve opening and the second valve opening cancel each other out. Features a relief valve. 2. The spool further defines at least a first chamber and a second chamber by dividing the hollow hole, and the first chamber is always in communication with the inlet port and through the first valve opening. The first outlet port and the second outlet port;
2. The relief valve according to claim 1, wherein the chamber communicates with the inlet port through the second valve opening and constantly communicates with the second outlet port. 3. A first pressure receiving surface on which a set spring is engaged and a pilot control pressure acts to determine the set pressure is formed at a first end of the spool. The relief valve according to claim 1, wherein a second pressure receiving surface on which the line pressure acts is formed at an end portion. 4. The relief valve according to claim 1, wherein the hydraulic line is a discharge line of a fixed displacement oil pump or a variable displacement oil pump. 5. The relief valve is applied to a transmission hydraulic line as the hydraulic line connected to a transmission hydraulic cylinder of a toroidal type continuously variable transmission, and the toroidal type continuously variable transmission is opposed to the transmission line. A pair of power rollers for continuously changing the rotation of the input disk according to the tilt angle of the input disk and the output disk with respect to the two disks and transmitting the rotation to the output disk; and rotating the power rollers. And a trunnion that is freely supported and rotates about the tilt axis by being displaced in the tilt axis direction by the operation of the shift hydraulic cylinder, and the shift hydraulic cylinder is configured to shift the gear through a gear ratio control valve. And two cylinder chambers that are operated by being supplied with the line pressure of the hydraulic pressure line, and each of the cylinder chambers has the gear ratio control valve in the neutral position. In a certain state, the cylinder chambers are selectively disconnected from the shift hydraulic line and the reservoir while the gear ratio control valve is displaced from the neutral position. The relief valve according to any one of claims 1 to 4, characterized in that: