JP3212651B2 - Hydraulic control circuit of hydraulically operated transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control circuit for a hydraulically operated transmission.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. 58-9466.
As disclosed in Japanese Unexamined Patent Publication No. 3 (Kokai) No. 3 (Kokai) No. 3-3, a belt type continuously variable transmission operated by hydraulic pressure is known. This belt-type continuously variable transmission includes a primary pulley and a secondary pulley whose effective diameter is controlled to be changed by hydraulic pressure, and has a configuration in which a V-belt is suspended between both pulleys. A combination of a joint and a forward / reverse switching mechanism provided with a friction engagement element such as a clutch or a brake is used as a continuously variable transmission for a vehicle.

In such a continuously variable transmission, the primary pulley is a speed ratio control pulley and the secondary pulley is a belt tension adjusting pulley.
The hydraulic control circuit of the continuously variable transmission includes a pressure control for adjusting a discharge ratio of a hydraulic pump to generate a line pressure, similarly to a normal automatic transmission for a vehicle in which a torque converter and a multi-speed transmission gear mechanism are combined. A pressure valve (pressure regulator valve) is provided. Since the secondary pulley requires a relatively high belt pressing pressure, the line pressure is directly supplied to a hydraulic chamber that operates the secondary pulley.

In addition, the line pressure is supplied to an operating hydraulic circuit of the torque converter via an orifice, and surplus oil generated by the pressure adjusting operation of the pressure regulating valve is discharged to the operating hydraulic circuit of the torque converter. Supplied to And, in order to prevent the operating oil pressure in the torque converter from rising above a predetermined value, the relief valve is disposed in the above-mentioned operating hydraulic circuit, and when the oil pressure in the torque converter is going to become higher than the predetermined value,
The operating oil of the operating hydraulic circuit is relieved via the relief valve.

[0005]

By the way, in a normal automatic transmission in which a gear is shifted by a multi-stage transmission gear mechanism and a frictional engagement element, the range of use of the line pressure is narrow (4-10 kg / cm ² at the time of forward movement). Even when the line pressure is supplied to the torque converter via the orifice, the flow rate of the hydraulic oil flowing through the orifice was relatively stable. However, in the belt-type continuously variable transmission, since the working range of the line pressure required by the hydraulic chamber of the secondary pulley is extremely wide (6 to 35 kg / cm ² ), the flow rate of the hydraulic oil flowing through the orifice greatly varies. Thus, it has been difficult to stably supply the working oil pressure to the torque converter.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a hydraulic control circuit for a hydraulically operated transmission which can supply a stable hydraulic pressure to a fluid coupling.

[0007]

To achieve the above object, according to the present invention, two pulleys whose effective diameters are controlled to be changed by hydraulic pressure, a belt suspended between these two pulleys, A first pressure regulating valve for controlling a discharge pressure of a pump to a line pressure and controlling a belt pressing pressure against one of the pulleys, and a fluid coupling for supplying surplus oil of the first pressure regulating valve from an operating hydraulic circuit Wherein the pressure is regulated by the first pressure regulating valve.
Oil within the first pressure regulating valves under stream in line flowing, first
A second pressure regulating valve having a substantially constant pressure regulating level lower than the pressure regulating level of the pressure regulating valve is connected, and a hydraulic pressure downstream of the second pressure regulating valve is supplied to the operating hydraulic circuit of the fluid coupling. It is characterized in that hydraulic pressure is also supplied from the circuit via the orifice.

[0008] In the second aspect of the present invention, the second pressure regulating valve supplies hydraulic pressure to the operating hydraulic circuit of the fluid coupling from the hydraulic circuit downstream thereof through an orifice, and operates the friction engagement element. Pressure shall be controlled.

According to a third aspect of the present invention, the excess oil of the first pressure regulating valve is generated by reducing a line pressure supplied to a hydraulic circuit disposed between the one pulley and an oil pump. Pilot pressure is supplied to the first pressure regulating valve.

[0010]

According to the present invention, in addition to the surplus oil of the first pressure regulating valve, a substantially constant hydraulic pressure is supplied from the hydraulic circuit downstream of the second pressure regulating valve to the working hydraulic circuit of the fluid coupling. Therefore, even if the supply of surplus oil from the first pressure regulating valve is restricted, stable supply of operating hydraulic pressure to the fluid coupling becomes possible.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a hydraulic control circuit of a hydraulically operated transmission according to the present invention is applied to a hydraulic control circuit of a belt type continuously variable transmission will be described below with reference to the drawings.

FIG. 2 is a skeleton diagram showing the entire configuration of the continuously variable transmission Z. The continuously variable transmission Z is a continuously variable transmission for driving front wheels, and includes a torque converter B connected to an output shaft 1 of an engine A, a forward / reverse switching mechanism C, a belt transmission mechanism D, and a reduction mechanism E. And a differential mechanism F.

The torque converter B is fixed to one side of a pump cover 7 connected to the engine output shaft 1 as shown in FIG.
A pump impeller 3 integrally rotating with the pump impeller 3, a turbine runner 4 opposed to the pump impeller 3 and rotatably provided in a space inside a pump cover 7, and a pump impeller 3 and a turbine runner 4. And a stator 5 interposed therebetween to perform a torque increasing action. Also,
The turbine runner 4 is connected via a turbine shaft 2 to a carrier 15 which is an input member of a forward / reverse switching mechanism C described later, and the stator 5 is connected via a one-way clutch 8 and a stator shaft 9 to a transmission case 19. I have.

Further, a lock-up clutch is disposed between the turbine runner 4 and the pump cover 7. The lock-up clutch includes a piston 6 spline-coupled to the turbine shaft 2 so as to be movable in the axial direction. The piston 6 occupies a space in the converter cover 7 with a converter rear chamber 7 a on the turbine 5 side and a converter. It is divided into a converter front chamber 10 on the cover 7 side. When the hydraulic pressure is introduced into or discharged from the converter front chamber 10, the pump cover 7 comes into contact with and is integrated with the pump cover 7 according to the pressure difference between the hydraulic pressure in the converter front chamber 10 and the hydraulic pressure in the converter rear chamber 7a. The lock-up state and the converter state separated from the pump cover 7 are selectively realized. And
In the lock-up state, the engine output shaft 1 and the turbine shaft 2 are directly connected without the intervention of fluid, and in the converter state, engine torque is transmitted from the engine output shaft 1 to the turbine shaft 2 via the fluid.

The forward / reverse switching mechanism C includes a torque converter B
In this embodiment, a forward state in which the rotation of the turbine shaft 2 is transmitted to the belt transmission mechanism D as it is, and a reverse state in which the rotation of the turbine shaft 2 is transmitted to the belt transmission mechanism D in the reverse direction are selectively set. The forward / reverse switching mechanism C is constituted by a double pinion type planetary gear unit. That is, the carrier 15 spline-coupled to the turbine shaft 2 has the first pinion gear 1 meshed with the sun gear 12.
3 and a second pinion gear 14 meshing with the ring gear 11
And are attached. The sun gear 12 is spline-coupled to the primary shaft 22 of the belt transmission mechanism D.

Further, between the ring gear 11 and the carrier 15, a forward clutch 16 for connecting and disconnecting the two is connected.
And the ring gear 11 and the transmission case 1
Between the transmission gear 9 and the transmission case 19
A reverse clutch (or brake) 17 is interposed in order to selectively secure the clutch.

Therefore, when the forward clutch 16 is engaged and the reverse clutch 17 is released, the ring gear 11 and the carrier 15 are integrated, and the ring gear 11 is rotatable relative to the transmission case 19. Therefore, the rotation of the turbine shaft 2 is output from the sun gear 12 to the primary shaft 22 as the same rotation as it is (forward state).

On the other hand, when the forward clutch 16 is released and the reverse clutch 17 is engaged, the ring gear 11 is fixed to the transmission case 19 and the ring gear 11 and the carrier 15 can rotate relative to each other. The rotation of the turbine shaft 2 is outputted from the sun gear 12 to the primary shaft 22 side in a state where the rotation is reversed via the first pinion gear 13 and the second pinion gear 14 (reverse state).

That is, in the forward / reverse switching mechanism C, the forward / backward switching is performed by the selection operation of the forward clutch 16 and the reverse clutch 17.

The belt transmission mechanism D is provided between a primary pulley 21 disposed coaxially behind the forward / reverse switching mechanism C and a secondary pulley 31 disposed at a distance from the primary pulley 21. 20 is suspended and configured.

As shown in FIG. 3, the primary pulley 21 is a primary shaft 22 having one shaft end spline-connected to the sun gear 12 of the forward / reverse switching mechanism C.
A fixed conical plate 23 having a predetermined diameter is placed on the primary shaft 2.
2 and the movable conical plate 24 is provided so as to be movable in the axial direction of the primary shaft 22. The conical friction surface of the fixed conical plate 23 and the conical friction surface of the movable conical plate 24 form a belt receiving groove 21a having a substantially V-shaped cross section.

A cylindrical piston 25 is fixed to the outer surface 24a of the movable conical plate 24. The piston 25 is oil-tight on the inner peripheral surface of a cylinder 26 fixed to the primary shaft 22. It is inserted. The piston 25, the cylinder 26, and the movable conical plate 24 constitute a single-chamber primary hydraulic chamber 27.
A hydraulic pressure is introduced into the primary hydraulic chamber 27 from a hydraulic circuit described later.

The primary pulley 21 has its movable conical plate 24
Is moved in the axial direction to increase or decrease the interval with the fixed conical plate 23 and change the groove width of the belt receiving groove 21a, thereby adjusting the winding radius of the belt 20 around the primary pulley 21, that is, the effective radius of the pulley 21. It has become.

The secondary pulley 31 has basically the same configuration as the above-described primary pulley 21, and as shown in FIG.
A fixed conical plate 33 is provided integrally with the secondary shaft 32 on a secondary shaft 32 disposed in parallel with and separated from the movable shaft 2, and a movable conical plate 34 is provided so as to be movable in the axial direction of the secondary shaft 32. . The conical friction surface of the fixed conical plate 33 and the conical friction surface of the movable conical plate 34 form a belt receiving groove 31a having a substantially V-shaped cross section.

A cylindrical cylinder 35 is fixed to the outer surface 34a of the movable conical plate 34, and a piston 36 fixed to the secondary shaft 32 is oil-tight to the inner surface of the cylinder 35. It is inserted. The piston 36, the cylinder 35, and the movable conical plate 34 form a single-chamber secondary hydraulic chamber 37. As in the primary hydraulic chamber 27, hydraulic pressure is introduced into the secondary hydraulic chamber 37 from a hydraulic circuit.

Similarly to the primary pulley 21, the secondary pulley 31 moves the movable conical plate 34 in the axial direction by hydraulic pressure introduced into the secondary hydraulic chamber 37 to increase or decrease the distance between the movable conical plate 34 and the fixed conical plate 33. , Belt receiving groove 31
By changing the groove width a, the winding radius of 20, that is, the effective radius of the pulley 31 is adjusted. The pressure receiving area of the movable conical plate 34 is set to be smaller than that of the movable conical plate 24 of the primary pulley 21.

With respect to the speed reduction mechanism E and the differential mechanism F,
Since the structure is conventionally known, the description thereof is omitted.

Next, the operation of the continuously variable transmission Z will be described. The torque transmitted from the engine A via the torque converter B is transmitted to the belt transmission mechanism D in the forward / reverse switching mechanism C with the rotation direction set to the forward direction or the reverse direction.

In the belt transmission mechanism D, when the effective radius of the primary pulley 21 is adjusted by introducing or discharging hydraulic oil into the primary hydraulic chamber 27 of the primary pulley 21, the primary pulley 21 is moved via the belt 20. Pulley 31 interlocked and connected
In the state following, the secondary pulley 3
The effective radius of 1 is adjusted. The gear ratio between the primary shaft 22 and the secondary shaft 32 is determined by the ratio between the effective radius of the primary pulley 21 and the effective radius of the secondary pulley 31.

The rotation of the secondary shaft 32 further
After being decelerated by the speed reduction mechanism E, the power is transmitted to the differential mechanism F, and transmitted from the differential mechanism F to the front axle.

Next, the hydraulic control circuit will be described with reference to FIGS. 4 to 6. The hydraulic control circuit includes the torque converter B in the above-described continuously variable transmission Z, the forward clutch 16 of the forward / reverse switching mechanism C, This is for supplying controlled hydraulic pressure to the reverse clutch 17, the primary hydraulic chamber 27 for operating the primary pulley 21 of the belt transmission mechanism D, and the secondary hydraulic chamber 37 for operating the secondary pulley 31. The source of the source pressure of the entire hydraulic circuit is the oil pump 40 driven by the engine A.

The hydraulic control circuit includes a pressure regulating valve 41 for regulating the line pressure, a pressure reducing valve 42, a speed ratio control valve 43,
Gear ratio hold valve 44, variable pressure valve 45, clutch valve 46, manual valve 4 for fail safe
7, a converter relief valve 48, an accumulator control valve 49, a lock-up shift valve 50, a lock-up control valve 51, and the like.

The speed ratio control valve 43 is directly controlled by a primary duty solenoid valve 52, and the speed ratio hold valve 44 is directly controlled by an on / off type solenoid valve 53. The variable pressure valve 45 is directly controlled by the duty solenoid 54 and controls the pressure regulating valve 41. The lock-up shift valve 50 and the lock-up control valve 51 include an on / off type solenoid valve 55 and a duty solenoid valve 5.
6 is controlled.

The hydraulic oil discharged from the oil pump 40 is first adjusted to a predetermined line pressure by a pressure adjusting valve 41, and then is adjusted via a line 101 to a secondary hydraulic chamber 3.
7 to form a belt pressing pressure of the secondary pulley 31. The line pressure is supplied to the clutch valve 46 through a line 102, where the line pressure is adjusted (reduced) to a predetermined pressure, and then sent to a manual valve 47 through a line 103.

The pressure reducing valve 42 reduces the line pressure,
An original pressure of the pilot pressure of the variable pressure valve 45, the speed ratio control valve 43, and the speed ratio hold valve 44 is generated on a line 104. From this original pressure, a pilot pressure of the variable pressure valve 45 is generated by a duty solenoid valve 54 that is opened and closed with a duty ratio according to the output torque and the gear ratio of the engine, and the hydraulic pressure (modifier pressure) regulated by the variable pressure valve 45 is obtained. The pressure is supplied to the pressure regulating valve 41 through the line 112 as a pilot pressure, so that a line pressure corresponding to the output torque and the transformation ratio of the engine is obtained.

The gear ratio control valve 43 is controlled by a primary duty solenoid valve 52 to derive a hydraulic pressure for operating the primary pulley 21 on a line 105 from a line pressure supplied through an orifice 61. The hydraulic pressure on the line 105 is transmitted through the transmission ratio hold valve 44 and the line 106 to the primary hydraulic chamber 2.
7 is supplied.

The speed ratio hold valve 44 is controlled by an off-drain type ON / OFF solenoid valve 53 which is in a drain state when not energized. When the solenoid valve 53 is on (excited), the line 106 communicating with the primary hydraulic chamber 27 is communicated with the line 105. When the solenoid valve 53 is off (non-excited), communication between the lines 105 and 106 is cut off. That is, when the solenoid valve 53 is not excited, the pressure in the primary hydraulic chamber 27 is maintained, and the gear ratio is fixed.

When the solenoid valve 53 is energized and the transmission ratio hold valve 44 connects the lines 105 and 106, and the primary duty solenoid valve 52 is on, the primary hydraulic chamber 27 The hydraulic oil of the line 106, 105, 107
, Through the relief ball 60, and no hydraulic pressure is generated in the primary hydraulic chamber 27. On the other hand, the primary
When the duty solenoid valve 52 is off, the line 107 as the drain passage is closed, and the line pressure enters the speed ratio control valve 43 through the orifice 61 and is introduced into the primary hydraulic chamber 27 through the lines 105 and 106. You. Accordingly, the speed ratio control valve 43 opens at an opening ratio corresponding to the duty ratio of the primary duty solenoid valve 52. In this case, the working oil is supplied into the primary hydraulic chamber 27 via the orifice 61, thereby preventing a rapid pressure increase in the primary hydraulic chamber 27.

In the forward movement state, the hydraulic pressure (clutch pressure) reduced by the clutch valve 46 is supplied to the forward clutch 16 through the line 103, the manual valve 47 and the line 108, so that the forward clutch 16 is engaged. Opened through line 109. On the other hand, in the reverse state, as long as the lock-up control valve 51 is in the non-lock-up state, the clutch pressure is supplied to the reverse clutch 17 through the line 103, the manual valve 47, and the lines 110 and 109, so that the reverse clutch 17 When engaged, the hydraulic pressure of the forward clutch 16 is released through the line 108. The accumulators 62 and 63 whose back pressure is controlled by the accumulator control valve 49 are connected to the lines 108 and 109, respectively.

That is, the accumulator control valve 49 is provided in the back pressure chambers 62a, 63a of the accumulators 62, 63.
The control pressure on the line 112 downstream of the variable pressure valve 45, that is, the pilot pressure of the pressure regulating valve 41 is introduced as the pilot pressure of the accumulator control valve 49. As aforementioned,
Since the variable pressure valve 45 is controlled by the duty solenoid valve 54 which is opened and closed with a duty ratio corresponding to the output torque and the variable pressure ratio of the engine, the accumulator control valve 49 is connected to the accumulators 62 and 63 provided on the lines 108 and 109. By controlling the back pressure, a shelf pressure for engaging the clutches 16 and 17 is generated with a level corresponding to the output torque and the gear ratio of the engine.
Has been mitigated.

On the other hand, surplus oil generated by the line pressure adjusting operation of the pressure adjusting valve 41 is discharged from the discharge port onto the line 114, and the converter relief valve 4
The hydraulic oil supplied to the hydraulic control valve 8 and discharged from the valve 48 to the line 115 is supplied from the clutch valve 46 to the line 116.
And the hydraulic oil supplied to the line 115 via the orifice 82 and to the torque converter B. When the oil pressure in the torque converter B is going to rise above a predetermined value, the converter relief valve 48 relieves the hydraulic oil to prevent the oil pressure from rising.

The lock-up control mechanism of the torque converter B includes a lock-up shift valve 50 and a lock-up control valve 51, and an on / off type solenoid valve 5
5 and a duty solenoid valve 56, which supplies hydraulic oil to the converter rear chamber 7 a of the torque converter B through a line 120 and supplies hydraulic oil in the converter rear chamber 7 a to a line 121. Through the oil cooler 64. Further, hydraulic pressure is supplied to the converter front chamber 10 through the line 122, and hydraulic oil in the converter front chamber 10 is discharged through the line 122 as needed, whereby the lock-up piston 6 comes into contact with the pump cover 7 and It is designed to be integrated with this.

The above is the overall configuration of the hydraulic control circuit of the hydraulically operated transmission according to the present invention. The features of the present invention will be further described with reference to FIG.

The line pressure regulating valve 41 (first pressure regulating valve) has a spool 71 urged leftward in the figure by a spring 70 provided in the pilot pressure chamber 41a.
The spool 71 has a biasing force of a spring 70, a pilot pressure introduced from a line 112 into a pilot pressure chamber 41 a through an orifice 72, and a line pressure applied to a feedback port 41 b through an orifice 73. To adjust the line pressure. That is, when the line pressure increases, the spool 71 moves to the right in the drawing against the urging force of the spring 70, and connects the output port 41c to the drain port 41d, thereby reducing the line pressure. When the spool 71 moves rightward in the figure, first, the output port 41c is connected to the discharge port 41.
e from the discharge port 41e to the line 1
14 to be discharged.

The line pressure is reduced by the pressure reducing valve 42 to a constant pressure, and the pilot pressure of the variable pressure valve 45 is controlled by a duty solenoid valve 54 which is opened and closed with a duty ratio corresponding to the output torque and the speed ratio of the engine from the constant pressure. A pressure is generated, and this oil pressure is supplied to the pilot pressure chamber 45a of the variable pressure valve 45. Next, the hydraulic pressure changed by the variable pressure valve 45 is introduced into the line 112 from the output port 45b, and is used as the pilot pressure of the pressure control valve 41 in the pilot pressure chamber 41a.
Supplied to The line pressure adjusted in this way is
Clutch valve 46 (second pressure regulating valve) which is a pressure reducing valve
, And the reduced hydraulic pressure is supplied to the manual valve 47 through the line 103.

On the other hand, the surplus oil discharged from the surplus oil discharge port 41 e of the pressure regulating valve 41 to the line 114 is supplied to a low flow type converter relief valve 48, and from the converter relief valve 48 to the torque converter B. Derived on line 115.

The converter relief valve 48 is urged rightward in FIG.
a, 76b. Further, the relief valve 48 is connected to the discharge port 4 of the pressure regulating valve 41.
1e, an input port 48a to which surplus oil is supplied, an output port 48b connected to a line 115 communicating with the torque converter B, and a hydraulic pressure of the output port 48b, that is, a hydraulic pressure of the line 115 A feedback port 48c that is supplied to a land 76a at the end of 76 and a drain port 48d are provided. When the oil pressure in the line 115 becomes higher than a predetermined value, the spool 76 moves to the left in the drawing against the urging force of the spring 75, closes the input port 48a, and connects the output port 48b to the drain port 48d. , 115 to reduce the hydraulic pressure of the line 115.

The clutch valve 46 has a spool 80 urged to the left by a spring 79, and has an input port 46a through which line pressure is supplied through a line 102, and a hydraulic pressure reduced from the line pressure. 103
Output port 4 that supplies to manual valve 47 through
6b and a feedback port 46c where the hydraulic pressure of the output port 46b is fed back via the orifice 81.
And a drain port 46d. Also line 1
15, the output port 46 of the clutch valve 46
The hydraulic pressure output from b is supplied through a line 116 having an orifice 82.

FIG. 7 is a characteristic diagram showing a change in the line pressure (secondary pressure) and a change in the output pressure (clutch pressure) of the clutch valve 46 with respect to a change in the output pressure (modifier pressure) of the variable pressure valve 45. ~ 35kg / c
Approximately 12 kg / cm ² with the line pressure changing in the range of m ^{2 as} the original pressure
Of the clutch pressure.

As is apparent from the above description, in this embodiment, the hydraulic pressure regulated to a substantially constant pressure by the clutch valve 46 is supplied from the line 116 to the line 115 via the orifice 82. The line 114 is formed by stacking the relief valve 48 or the like.
Even if the supply of the surplus oil through the motor stops, the stable supply of the working oil pressure to the torque converter B is possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main part of an embodiment of a hydraulic control circuit of a hydraulically operated transmission according to the present invention.

FIG. 2 is a skeleton diagram illustrating a mechanical configuration of a belt-type unauthorized family machine controlled by a hydraulic control circuit according to the present invention.

FIG. 3 is a diagram showing a specific configuration of a torque converter, a forward / reverse switching mechanism, and a primary pulley of the continuously variable transmission.

FIG. 4 is a diagram showing a specific configuration of a secondary pulley of the continuously variable transmission and a left part of a hydraulic control circuit.

FIG. 5 is a diagram showing a central portion of the hydraulic control circuit.

FIG. 6 is a diagram showing a right part of the hydraulic control circuit.

FIG. 7 is a characteristic diagram showing changes in line pressure and clutch pressure with respect to changes in a modifier.

[Explanation of symbols]

 Reference Signs List 6 lock-up piston 7 pump cover 7a converter rear chamber 10 converter front chamber 16 forward clutch 17 reverse clutch 20 belt 21 primary pulley 22 primary shaft 27 primary hydraulic chamber 31 secondary pulley 32 secondary shaft 37 secondary hydraulic chamber 41 pressure regulating valve 42 pressure reducing valve 43 Gear ratio control valve 44 Gear ratio hold valve 45 Variable pressure valve 46 Clutch valve 47 Manual valve 48 Converter relief valve 49 Accumulator control valve 50 Lock-up shift valve 51 Lock-up control valve 52, 54, 56 Duty solenoid valve 53, 55 ON / OFF type solenoid valve

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-53357 (JP, A) JP-A-56-35855 (JP, A) JP-A-62-4958 (JP, A) JP-A-63-358 38750 (JP, A) JP-A-58-94663 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16H 59/00-61/12 F16H 61/16-61/24 F16H 63/40-63/48 B60K 17/06

Claims (3)

(57) [Claims] 1. Two pulleys whose effective diameters are changed and controlled by hydraulic pressure, a belt suspended between the two pulleys, and a belt for controlling one of the pulleys while controlling a discharge pressure of an oil pump to a line pressure. In a hydraulically operated transmission including: a first pressure regulating valve for controlling a pressing pressure; and a fluid coupling supplied with surplus oil of the first pressure regulating valve from a working hydraulic circuit, the first pressure regulation is provided. Of the line through which the oil regulated by the valve flows
The First pressure regulating valves under flow, by connecting the second pressure regulating valve having a substantially constant regulated pressure level is lower than the pressure regulating level of the first pressure regulating valve, hydraulic fluid pressure of the fluid coupling A hydraulic control circuit for a hydraulically operated transmission, wherein hydraulic pressure is supplied to the circuit from an oil pressure circuit downstream of the second pressure regulating valve via an orifice. 2. The valve according to claim 1, wherein the second pressure regulating valve supplies a hydraulic pressure to a hydraulic pressure circuit of the fluid coupling from a hydraulic circuit downstream thereof through an orifice and controls a hydraulic pressure of a frictional engagement element. 2. The hydraulic control circuit for a hydraulically operated transmission according to claim 1, wherein: 3. A pilot pressure generated by reducing a line pressure supplied to a hydraulic circuit disposed between the one pulley and an oil pump, as an excess oil of the first pressure regulating valve. 3. The hydraulic control circuit for a hydraulically operated transmission according to claim 1, wherein the hydraulic control circuit is obtained by being supplied to one pressure regulating valve.