JP2701475B2 - Hydraulic control device for belt-type continuously variable transmission for vehicles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hydraulic control device for a belt-type continuously variable transmission for a vehicle.

2. Description of the Related Art There is known a continuously variable transmission for a vehicle that is inserted into a power transmission path of a vehicle to continuously change the rotation of an engine and transmit the rotation to drive wheels. For example, power is transmitted through a transmission belt wound around a pair of variable pulleys, and the speed ratio is changed by changing the effective diameter of the variable pulley, while the engagement pressure of the transmission belt, This is a belt-type continuously variable transmission in which the power transmission capacity is adjusted according to the control oil pressure supplied to a hydraulic cylinder that generates a squeezing force on a pulley. In the belt-type continuously variable transmission as described above, power is transmitted based on the frictional force of the power transmission belt. Therefore, the power loss is reduced by controlling the clamping pressure on the power transmission belt as necessary and sufficiently. Further, it is desired to increase the durability.

For this reason, normally, a control hydraulic pressure of a magnitude corresponding to the input torque and the speed ratio of the belt-type continuously variable transmission is regulated by the pressure regulating valve and supplied to the hydraulic cylinder,
In addition, in order to compensate for an increase in the squeezing force of the transmission belt based on the centrifugal oil pressure generated in the hydraulic cylinder rotating with the output shaft or the input shaft, the squeezing force of the hydraulic cylinder is reduced by rotating with the hydraulic cylinder. A compensating oil chamber that compensates for squeezing pressure by generating a compensating thrust in the direction is provided, and the compensating oil chamber generates insufficient compensating thrust based on the pressure receiving area difference between these hydraulic cylinders and the compensating oil chamber. In order to solve the problem, there has been proposed a hydraulic control device that reduces a control hydraulic pressure supplied to a hydraulic cylinder in association with an increase in the rotation speed of the hydraulic cylinder. For example, the hydraulic control device described in FIGS. 1 and 2 of JP-A-63-30641 is such a device.

Problems to be Solved by the Invention Incidentally, in the above conventional hydraulic control device, since the control oil pressure supplied to the hydraulic cylinder is controlled by a relief type pressure regulating valve, the control pressure changed according to the rotation speed is: It is restricted within a predetermined range. That is, the maximum value of the control pressure does not exceed the output pressure of the hydraulic pressure source supplied to the pressure regulating valve, and the minimum value of the control pressure is limited by the minimum value of the controllable range of the pressure regulating valve. For this reason, if the control pressure is limited as described above when the control pressure is to be reduced and corrected in relation to the vehicle speed, the control pressure does not decrease sufficiently, and the control pressure is not reduced sufficiently due to the centrifugal hydraulic pressure in the hydraulic cylinder. In some cases, the increase in the squeezing pressure cannot be sufficiently compensated, and the power loss may be reduced and the durability of the transmission belt may not be sufficiently obtained.

The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce the clamping pressure caused by the centrifugal oil pressure in the hydraulic cylinder even if the pressure adjustment range of the control pressure by the pressure adjustment valve is limited. An object of the present invention is to provide a hydraulic control device that can sufficiently compensate for the increase.

Means for Solving the Problems To achieve the above object, the gist of the present invention is to provide a pair of input-side variable pulleys and an output-side variable pulley provided on an input shaft and an output shaft, respectively, and the pair of input-side variable pulleys. A pair of input-side hydraulic cylinders and an output-side hydraulic cylinder that change the effective diameter of the transmission belt wound around the output-side variable pulley and the output-side variable pulley. Power is transmitted from the input shaft to the output shaft via the transmission belt. In a transmission belt-type continuously variable transmission for a vehicle, a hydraulic control device for controlling a clamping force on the transmission belt,
(A) An oil-tight compensating oil having a pressure receiving area smaller than that of the output side hydraulic cylinder and generating a compensating thrust in the direction opposite to the clamping pressure of the output side hydraulic cylinder in order to reduce the clamping pressure. And (b) compensating hydraulic pressure supply means for increasing the hydraulic pressure supplied to the compensating oil chamber in association with an increase in vehicle speed and decreasing the hydraulic pressure supplied to the output side hydraulic cylinder. .

In this way, the clamping pressure on the transmission belt is basically compensated by the compensating thrust based on the centrifugal oil pressure generated in the compensation oil chamber, while the output hydraulic cylinder and the output hydraulic cylinder Even if the control pressure for compensating for the lack of the compensating thrust caused by the pressure receiving area difference from the compensating oil chamber having a small pressure receiving area is limited by the lower limit of the pressure regulating range of the pressure regulating valve, the compensation hydraulic The supply means increases the hydraulic pressure supplied to the compensating oil chamber in association with the increase in the vehicle speed and reduces the hydraulic pressure supplied to the output side hydraulic cylinder. The increase in the squeezing pressure is preferably offset. For this reason,
The increase in the squeezing pressure due to the centrifugal oil pressure in the hydraulic cylinder can be suitably compensated, and the squeezing pressure can be controlled with high accuracy.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a skeleton view illustrating a power transmission device of an FF type vehicle. In the figure, the power of an engine 10 is a torque converter 12, a forward / reverse switching device 14, a belt-type continuously variable transmission 16,
The power is transmitted to the pair of front wheels 22 via the reduction gear device 18 and the differential gear device 20. The torque converter 12 includes a pump impeller 26 connected to a crankshaft 24.
And a turbine impeller 28 connected to the forward / reverse switching device 14.
And the stator 30 fixed via a one-way clutch
It is composed of The torque converter 12
Instead, a clutch such as a fluid coupling, an electromagnetic clutch, or a friction clutch may be used.

The forward / reverse switching device 14 is a not-shown planetary gear device,
A forward clutch, a reverse brake and the like are provided, and the torque input from the turbine impeller 28 of the torque converter 12 is switched in the forward rotation direction or the reverse rotation direction in accordance with a hydraulic signal from a hydraulic circuit (not shown), and the belt type is provided. The power is transmitted to the input shaft 32 of the step transmission 16. Belt-type continuously variable transmission 16
Has a pair of variable pulleys 36 and 38 provided on the input shaft 32 and the output shaft 34, and a transmission belt 40 wound around the variable pulleys 36 and 38 to transmit power. The transmission belt 40 functions as a transmission member of the belt-type continuously variable transmission 16, and the transmission capacity is determined according to the tension of the transmission belt 40, in other words, the clamping force of the variable pulley 38 on the transmission belt 40.

The essential part of the hydraulic circuit according to the present embodiment is configured as shown in FIG. 1, and the hydraulic oil volume in the input side hydraulic cylinder 42 for changing the V-groove width of the variable pulley 36 is changed by the shift control valve 44. The speed ratio e (= output shaft rotation speed N _out / input shaft rotation speed N _in ) of the belt-type continuously variable transmission 16 is changed by changing the V-groove width of the variable pulley 36. Has become. Further, the line pressure Pl regulated by the line pressure regulating valve 48 is always applied to the output side hydraulic cylinder 46 of the belt type continuously variable transmission 16 in order to exclusively control the tension of the transmission belt 40. Has become. In the present embodiment, the line pressure Pl functions as a control oil pressure for controlling the tension of the transmission belt 40. The line pressure regulating valve 48 is a relief type pressure regulating valve that regulates the line pressure Pl by adjusting the amount of hydraulic oil leaking from the line oil passage 78 to the return oil passage 82. The line pressure Pl is adjusted within a pressure adjustment range from the minimum pressure adjustment value Pl _min to the maximum pressure adjustment value Pl _max .

As shown in detail in FIG. 1, the output shaft 34 is rotatably supported by a transaxle housing (not shown) via a bearing 52. The output shaft 34 has a variable pulley
A fixed disk 54 and a movable disk 56 which constitute 38 are provided. That is, the output shaft 34 has a fixed disk
A movable disk 56 is provided so as to be movable in the axial direction and non-rotatable around the axis.
The transmission belt 40 is wound around the V groove between the fixed disk 54 and the movable disk 56.

The movable disk 56 includes an inner cylindrical portion 58 and an outer cylindrical portion 60 that protrude concentrically in the axial direction. Spline teeth formed on the inner circumferential surface of the inner cylindrical portion 58 and the outer circumferential surface of the output shaft 34. The spline teeth formed on the outer cylindrical portion 60 are spline-fitted, and an inward flange portion 62 is formed at the end of the outer peripheral cylindrical portion 60 toward the inner peripheral side. The output shaft 34 has a bottomed cylindrical portion 64 slidably in contact with the inner peripheral edge of the inward flange 62 on the outer peripheral surface, and an outer periphery protruding from the open edge of the bottomed cylindrical portion 64 to the outer peripheral side. Flange part
A fixed cylinder member 68 is provided. As a result, a relatively oil-tight first oil chamber 70 is formed between the movable disk 56 and the cylinder member 68 for exclusively generating a clamping force on the transmission belt 40. An oil-tight seal between the cylindrical portion 60 and the inward flange portion 62 for generating an opposing force for compensating for an increase in the squeezing pressure W caused solely by the centrifugal oil pressure generated in the first oil chamber 70. Two oil chambers 72 are formed. Reference numeral 73 denotes a seal member formed of, for example, an O-ring.

Therefore, the output side hydraulic cylinder 46 has a first pressure receiving area A ₁ corresponding to the first oil chamber 70, that is, an annular pressure receiving area having the outer diameter of the outer cylindrical portion 60 and the inner diameter of the output shaft 34. The power transmission belt 40 is pinched by a thrust based on the area and the line pressure Pl acting on the transmission pressure, but the second pressure receiving area A ₂ corresponding to the second oil chamber 72, that is, the inner diameter of the outer cylindrical portion 60 is set as the outer diameter and If the compensating thrust based on the compensation pressure Pl acting (P ₂₎ of the outer diameter to an annular pressure receiving area a ₂ of the inner diameter of the bottomed cylindrical portion 64 is allowed to occur, due to the compensating thrust The clamping pressure W on the transmission belt 40 is reduced. That is, the clamping pressure W on the transmission belt 40 is determined based on (A ₁ −A ₂ ) × Pl. In this embodiment, the second
The oil chamber 72 functions as a compensating oil chamber that generates a compensating thrust in the direction opposite to the clamping pressure in order to decrease the clamping pressure W on the transmission belt 40 as the vehicle speed increases.

The oil pump 74 is rotationally driven by the engine 10 to pump the hydraulic oil recirculated into the oil tank 76 to the line oil passage 78 under pressure. The line pressure regulating valve 48 regulates the line pressure Pl by changing the amount of hydraulic oil leaked to the return oil passage 82 according to a command signal from an electronic control device 80 described later. The line pressure Pl is supplied to the shift control valve 44, while being constantly supplied to the first oil chamber 70 through the switching valve 86 at the normal position and the oil passage 84 provided in the output shaft 34. Switching valve
86 connects the first oil chamber 70 to the line oil passage 78 and the second oil chamber
The normal position in which the second oil chamber 72 is connected to the return oil path 82 and the compensation position in which the second oil chamber 72 is connected to the line oil path 78 and the first oil chamber 70 is connected to the return oil path 82 can be switched. When the electronic control unit 80 is located at the normal position, the lubricating oil pressure described below is applied to the pressure receiving surface in the second oil chamber 72.
P ₀ is actuated, but when it is positioned at the compensation position, the first oil chamber 70 is communicated with the return oil path 82 to lubricate the oil pressure P ₁ in the first oil chamber 70 from the line pressure Pl up to that point. while reducing the pressure P _o, the switching valve 86, the oil passage provided in the output shaft 34 8
8, the line pressure Pl is applied to the pressure receiving surface in the second oil chamber 72 through the oil passage 90 formed in the cylinder member 68,
Increasing the pressure P ₂ in the oil chamber 72 from the pressure P ₀ so far to Pl.
Therefore, in the present embodiment, the switching valve 86 and the like are supplied into the second oil chamber 72, which is a compensation oil chamber, by the line pressure that is the compensation oil pressure.
Supplying Pl in conjunction with increasing vehicle speed
It functions as compensation oil pressure control means for increasing the oil pressure in the oil chamber 72 and decreasing the oil pressure in the first oil chamber 70.

A part of the hydraulic oil flowing out of the line pressure regulating valve 48 and the switching valve 86 to the return oil passage 82 is returned to the oil tank 76 through the check valve 92. The oil is supplied to an oil cooler (not shown), and is supplied to a bearing (not shown) as lubricating oil. The check valve 92 controls the oil pressure in the return oil passage 82 to the line pressure Pl to send oil to an oil cooler, a bearing, and the like.
It is intended to generate a slightly higher constant lubricant pressure P ₀ than sufficiently low and the atmospheric pressure than.

The electronic control unit 80 is a so-called microcomputer including a CPU, a ROM, a RAM, and the like.The CPU processes an input signal according to a program stored in a ROM in advance while using a temporary storage function of the RAM, and controls the shift control valve 44, The operation of the line pressure regulating valve 48 and the switching valve 86 is controlled. The electronic control unit 80 reads, for example, the throttle valve opening θ corresponding to the required output amount from the throttle sensor 94, and detects the rotation speeds of the input shaft 32 and the output shaft 34 from the input shaft rotation sensor 96 and the output shaft rotation sensor 98. The vehicle speed V is calculated based on the rotational speeds of the read and output shafts 34, and the speed ratio e of the belt-type continuously variable transmission 16 is calculated based on the rotational speeds of the input shaft 32 and the output shaft 34.

In the speed ratio control of the belt-type continuously variable transmission 16, the electronic control unit 80 controls the actual throttle valve opening based on a relationship determined in advance so that the engine 10 operates along an optimal curve in consideration of fuel efficiency and drivability. The target rotation speed N _in ^* is determined based on the degree θ and the vehicle speed V, and the speed control valve 44 is driven to control the speed ratio so that the actual input shaft rotation speed N _in matches the target rotation speed N _in ^*. I do. In the line pressure control, the electronic control unit 80 adjusts the line pressure based on the actual throttle valve opening θ and the speed ratio e based on a relationship previously determined so that the transmission belt 40 has a necessary and sufficient tension. By driving the pressure valve 48, the power loss related to the rotational driving of the oil pump 74 is reduced as much as possible. The belt clamping force W of time is determined based on the line pressure Pl acting primarily pressure receiving area A ₁ of the first oil chamber 70 and a first oil chamber 70. Moreover, in this line pressure control, the line pressure Pl is decreased with the increase of the vehicle speed V from a predetermined relationship during high-speed running in which the speed ratio e is continuously the value of the maximum speed. Drive the line pressure regulating valve 48,
The shortage of the compensation thrust for the transmission belt 40 due to the pressure receiving area difference (A ₁ −A ₂ ) between the first oil chamber 70 and the second oil chamber 72 is eliminated. Furthermore, the electronic control unit 80 determines whether the vehicle speed V exceeds the determination reference value V ₂ to a predetermined, if not exceeded positions the selector valve 86 as shown in Figure 1 during normal position The pressure in the first oil chamber 70 is set to the line pressure Pl and the pressure in the second oil chamber 72 is set to the compensating oil pressure Po. Lubrication oil pressure
By setting Po and the line pressure Pl in the second oil chamber 72, the clamping pressure on the transmission belt 40 is reduced. The belt clamping pressure W at this time is mainly the pressure receiving area of the first oil chamber 70.
A value obtained by subtracting the compensating thrust based on the line pressure Pl acting on the pressure receiving area A ₂ between the thrust from the second oil chamber 72 based on the lubricating oil Po acting on the A _1.

 Hereinafter, the operation and effect of the present embodiment will be described.

At the time of high-speed running of a vehicle in which the speed ratio e is continuously the value on the highest speed side, as described above, the line pressure Pl is decreased so as to decrease the line pressure Pl as the vehicle speed V increases from the predetermined relationship. The pressure regulating valve 48 is driven, and the first oil chamber 70 and the second
Insufficiency of the compensating force for the transmission belt 40 due to the pressure receiving area difference from the oil chamber 72 is eliminated. Changes in line pressure Pl until the vehicle speed V ₁ of the Figure 3 shows this state.

When the vehicle speed V reaches V _1, the line pressure Pl is limited to the lower limit value Pl _min pressure regulating range determined by the structure of the line pressure regulating valve 48 of the relief type, it can not be reduced further. Therefore, when the vehicle speed V exceeds V _1, V ₁ of the line pressure Pl is Figure 3
It is a raw value Pl _min as shown until V ₂ from the belt squeezing force W begins to increase with increasing centrifugal hydraulic pressure as shown in Figure 4. However, when the vehicle speed V reaches V _2, since the switching valve 86 as described above is switched to the compensation for position, when the first oil chamber 70 is lowered from the line pressure Pl to lubricant pressure Po at the same time, the second The pressure in the oil chamber 72 is increased from the lubricating oil pressure Po to the line pressure Pl, and the clamping pressure on the transmission belt 40 is reduced. Then, in the this since, since the line pressure Pl in accordance with a command from the electronic control unit 80 is increased with increasing vehicle speed, based on the line pressure Pl acting to the pressure receiving area A ₂ of the second oil chamber 72 The compensation thrust is increased, and the belt clamping pressure W is kept constant irrespective of the increase in the vehicle speed V. V ₂ and subsequent FIG. 4 shows this state.

Therefore, according to this embodiment, when it exceeds V ₂ vehicle speed V rises, the oil pressure P ₁ is the change-over valve 86 in the first oil chamber 70 is lowered from the line pressure Pl to lubricant pressure Po at the same time, the The hydraulic pressure P ₂ in the second oil chamber 72 is increased from the lubricating oil pressure Po to the line pressure Pl, and the clamping pressure on the transmission belt 40 is reduced to the target value W _0, so that the first oil chamber 70 and the second oil chamber 72 Even if the reduction of the line pressure Pl for compensating for the shortage of the compensating thrust caused by the pressure receiving area difference (A ₁ −A ₂ ) is limited by the lower limit of the pressure regulation range of the line pressure regulating valve 48, the output side hydraulic cylinder 46 Since the increase in the squeezing pressure W due to the centrifugal oil pressure in the inside is suitably offset,
Nipping pressure W due to centrifugal oil pressure in output side hydraulic cylinder 46
Can be suitably compensated for, and the pinching pressure can be controlled with high accuracy, and the power loss can be reduced and the durability of the transmission belt can be sufficiently obtained.

In this connection, FIG. 5 and FIG. 6 shows a case where the vehicle speed V is conventionally not supplied line pressure Pl to the second oil chamber 72 even if the V ₂ or more. The shaded area in FIG. 5 indicates a region in which the line pressure Pl should be reduced in order to compensate for an increase in the clamping pressure W based on the centrifugal oil pressure, but is limited by the lower limit Pl _min of the pressure regulation range. 6 indicates an excessive belt clamping pressure W that is generated based on the centrifugal oil pressure generated in the first oil chamber 70 and increases with the vehicle speed V.

Next, another embodiment of the present invention will be described. In the following description, the same parts as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted. Further, the electronic control unit 80 and the shift control valve 44 are omitted in the block diagrams of the following embodiments.

Example of FIG. 7, the electronic control oil pressure P _D indicating the maximum value when and the vehicle speed V ₂ lower than the line pressure Pl unchanged in relation to the vehicle speed V as shown in two-dot chain line in FIG. 8 A second pressure regulating valve 100 generated according to a command from the device 80 is added to the hydraulic circuit of FIG. Thus, in a state where the switching valve 86 is switched to the normal position, the hydraulic pressure P ₁ in the first oil chamber 70 is the line pressure Pl and second
Although hydraulic P ₂ in the oil chamber 72 is with the oil pressure P _D, in a state that is switched to the compensation for position, pressure P ₁ in the first oil chamber 70
Is the hydraulic pressure P _D and the hydraulic pressure P ₂ in the second oil chamber 72 is the line pressure Pl. According to this embodiment, as shown in FIG. 8, the line pressure Pl is controlled to be constant irrespective of the vehicle speed V, the hydraulic pressure P _D is increased until the vehicle speed V reaches V _2, the vehicle speed V is V _Two
Since it is controlled to descend after a Pl ≒ P _D leads to an advantage that the belt clamping force W is maintained at a necessary and sufficient target pressure W _0. According to the present embodiment, the vehicle speed V is adjusted so that the increase in the clamping pressure W based on the centrifugal oil pressure is compensated.
While pressure P _D is increased continuously from before reaching V _2,
The line pressure Pl does not change regardless of the vehicle speed.
The pressure regulation range is maintained at a value sufficiently larger than the lower limit Pl _{min of the} pressure regulation range. Incidentally, the line pressure Pl and pressure P _D, the ninth
A similar effect can be obtained even if the control is performed as shown in the drawing.

In the embodiment of FIG. 10, while the switching valve 86 of FIG. 1 is removed, the hydraulic pressure P _D that is lower than the line pressure Pl and increases as the vehicle speed V increases as shown by a two-dot chain line in FIG. and second pressure regulating valve 100 is provided for generating in accordance with a command of the electronic control device 80, acting on the hydraulic P _D is always the second oil chamber 72 with the line pressure Pl is applied to the first oil chamber 70 at all times Have been. The hydraulic pressure P _D is controlled so as to compensate for an increase in the squeezing pressure W based on the centrifugal oil pressure, while the line pressure is controlled.
Since Pl is being varied above the limit Pl _min pressure regulating range of line pressure regulating valve 48, as shown in FIG. 12, is maintained in the belt squeezing force W is required and sufficient target pressure W ₀ There are advantages.

In the embodiment of Figure 13, while the switching valve 86 in Figure 1 is removed, the first switching valve 102 to alternatively effect one of the first oil chamber 70 to the line pressure Pl and lubricating oil P _o a second switching valve 104 to alternatively effect is provided either in the second oil chamber 72 to the line pressure Pl and lubricating oil P _o. The hydraulic pressure P ₁ in the first oil chamber 70 and the hydraulic pressure P ₂ in the second oil chamber 72
As shown in the figure, the line pressure Pl is always applied to the first oil chamber 70 through the first switching valve 102 and to the second oil chamber 72 through the second switching valve 104 so as to change in relation to the vehicle speed V. the vehicle speed V reaches V _2, the first switching valve 102 is switched by the electronic control unit 80, the hydraulic pressure in the first oil chamber 70
P ₁ is lowered from the line pressure Pl so far into the lubricating oil pressure P _0. In the case shown in FIG. 15, like the embodiment of FIG. 1, the line pressure Pl is raised again when the vehicle speed V exceeds V _2.

According to this embodiment, as shown in FIG. 16, the belt clamping force W is begins to rise and the vehicle speed V reaches V _1, is returned when the vehicle speed V reaches V ₂ to the target value W _0. And the 14th
When the oil pressure is controlled as shown in the figure, the belt clamping pressure W starts increasing again as shown by the solid line in FIG.
When the hydraulic pressure is controlled as shown in FIG. 15, the belt clamping pressure W is kept constant as shown by the broken line in FIG. Also in this embodiment, similarly to the above-described embodiments, the belt clamping pressure W is suitably controlled.

FIG. 17 shows the first switching valve 102 when the vehicle starts.
And switching control of the second switching valve 104. In this embodiment, the input shaft rotation speed and the output shaft rotation speed of the torque converter 12 are detected by a sensor (not shown), and as shown in FIG. 17, the torque converter 12 calculated from those rotation speeds is used. When it is determined that the slip ratio r of the first oil chamber is lower than _a predetermined reference value ra for determining the torque converter region (torque amplification region), the line pressure Pl is applied to the first oil chamber 70. Although the action of lubricating oil P ₀ to be allowed and the second oil chamber 72, when the slip ratio r is determined to be the coupling region of the torque converter 12 exceeds the determination reference value r _a, the second Switching valve 10
4 is switched to apply the line pressure Pl to the second oil chamber 72. Therefore, for example, in a torque converter region in which the input torque of the belt-type continuously variable transmission 16 increases due to the torque amplifying action of the torque converter 12 when the vehicle starts, the belt clamping pressure W is increased and the torque transmission capacity is increased. ing.

Example of FIG. 18, the second to generate a hydraulic pressure P _D which and the vehicle speed V lower than the line pressure Pl as shown in FIG. 19 is reduced enough larger than V ₁ in accordance with a command of the electronic control device 80 The pressure regulating valve 100 is configured by being added to the hydraulic circuit of FIG. Thus, in the process of increasing the vehicle speed V toward V ₁ , the line pressure Pl is applied to the first oil chamber 70 through the first switching valve 102 and the second pressure is applied to the second oil chamber 70 through the second switching valve 104.
Although the oil chamber 72 the line pressure Pl is operatively, the vehicle speed V reaches V _1, the first oil chamber first switching valve 102 is switched 7
0 pressure P _D is exerted on the. As shown in FIG. 19, the line pressure Pl is controlled to decrease as the vehicle speed V increases, but does not decrease below the pressure regulation lower limit value Pl _min . However, the hydraulic P _D is because it is controlled so as to decrease with increase in the vehicle speed V from this state, the belt clamping force W is continuously reduced with increasing vehicle speed V, is generated based on the centrifugal hydraulic pressure An increase in the belt clamping pressure W is suitably compensated.

In this embodiment, as in the embodiment shown in FIG. 17, control is performed so that the belt clamping pressure W is increased in the torque converter region of the torque converter 12 when the vehicle starts moving. That is, in this embodiment, as shown in FIG. 20, the line pressure P is passed through the first switching valve 102 into the first oil chamber 70.
l is continuously applied and the second oil chamber 72 has a second switching valve 104
Although pressure P _D is continuously acts through the second pressure regulating valve 100 so that hydraulic pressure P _D with increasing slip ratio r is the torque converter area rises toward the line pressure Pl
Is controlled. For this reason, in the torque converter region where the input torque of the belt-type continuously variable transmission 16 is large, the belt clamping pressure W is necessary and sufficiently controlled in accordance with the torque increase due to the torque amplifying action.

Further, in the hydraulic circuit similar to Figure 7, while increasing the belt clamping force W by the action of pressure P _D to the second oil chamber 72 and by the action of the line pressure Pl in the first oil chamber 70 in the torque converter region During normal traveling, the hydraulic pressure P _D is increased to the line pressure Pl, and the line pressure Pl is decreased with an increase in the vehicle speed V. Further, during high-speed traveling, the hydraulic pressure P _D is applied to the first oil chamber 70 and the second hydraulic pressure P _D is applied. The line pressure Pl acts on the chamber 72 and the vehicle speed V
The line pressure Pl may be increased with the increase in the pressure.

As mentioned above, although one Example of this invention was described based on drawing, this invention is applied also in another aspect.

For example, in the above-described embodiment, the switching valve 86, the first switching valve 102, and the second switching valve 104 are configured to be electrically switched according to a command from the electronic control unit 80. The switching may be performed based on a hydraulic signal related to the vehicle speed generated from the governor valve, or the hydraulic pressure that continuously increases as the vehicle speed V increases according to a command from the electronic control device 80 may be changed to the line pressure Pl or another pressure. It may be configured to be generated from a hydraulic pressure source and supplied to the second chamber 72.

Further, in the above-described embodiment, while the line pressure Pl is constantly applied to the first oil chamber 70 of the output-side hydraulic cylinder 46, the shift control valve 44 causes the hydraulic oil in the input-side hydraulic cylinder 42 to flow out, or Although the speed ratio e is controlled by supplying the hydraulic oil into the side hydraulic cylinder 42, the first line pressure on the high pressure side and the second line pressure lower than
The present invention is applicable to a hydraulic control circuit of a type that controls the belt clamping pressure W while controlling the speed ratio e by acting on one and the other of the input-side hydraulic cylinder 42 and the output-side hydraulic cylinder 46. You get.

The above is merely an example of the present invention, and the present invention can be variously modified without departing from the spirit thereof.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross-sectional configuration of a main part of the hydraulic control circuit and an output-side variable pulley of the embodiment of FIG. FIG. 2 is a skeleton view showing a vehicle power transmission device including one embodiment of the present invention. 3 and 4 are views for explaining the operation of the embodiment of FIG. 2, wherein FIG. 3 shows the relationship between vehicle speed and line pressure, and FIG. 4 shows the relationship between vehicle speed and belt clamping pressure. Shows the relationship. 5 and 6 are diagrams corresponding to FIGS. 3 and 4 of a conventional hydraulic control device that does not increase the pressure in the compensating oil chamber as the vehicle speed increases. FIG. 7 is a diagram corresponding to FIG. 1 showing another embodiment of the present invention, and FIGS. 8 and 9 are diagrams corresponding to FIG. 3 in the embodiment of FIG. FIG. 10, FIG. 11,
FIG. 12 shows another embodiment of the present invention.
FIG. 5 is a diagram corresponding to FIG. 3 and FIG. 4, respectively. No.
13, FIG. 14, FIG. 15, and FIG. 16 are views corresponding to FIG. 1, FIG. 3, and FIG. 4, respectively, in another embodiment of the present invention. FIG. 17 is a view for explaining the operation of the embodiment of FIG. 13 at the time of starting. Fig. 18, Fig. 19
FIG. 20 and FIG. 20 show a first embodiment according to another embodiment of the present invention.
FIG. 5 is a diagram corresponding to FIG. 3, FIG. 3, and FIG. 4, respectively. 16: Belt-type continuously variable transmission 32: Input shaft 34: Output shaft 36: Variable pulley (input side variable pulley) 38: Variable pulley (output side variable pulley) 40: Transmission belt 42: Input side hydraulic cylinder 46: Output side Hydraulic cylinder 72: Second oil chamber (compensation oil chamber) 86: Switching valve (compensation hydraulic control means) 102: First switching valve 104: Second switching valve

Claims (1)

(57) [Claims] 1. An effective diameter of a pair of input-side variable pulleys and output-side variable pulleys provided on an input shaft and an output shaft, respectively, and a transmission belt wound around the pair of input-side variable pulleys and output-side variable pulleys. A pair of input-side hydraulic cylinders and an output-side hydraulic cylinder that change power, and a clamping force against the power transmission belt in a vehicle belt-type continuously variable transmission that transmits power from an input shaft to an output shaft via the power transmission belt. A hydraulic pressure control device for controlling a pressure receiving area smaller than the output side hydraulic cylinder,
An oil-tight compensating oil chamber for generating a compensating thrust in the direction opposite to the clamping pressure of the output hydraulic cylinder to reduce the clamping pressure; and A hydraulic pressure control device for a belt-type continuously variable transmission for a vehicle, comprising: compensating hydraulic pressure supply means for increasing the supplied hydraulic pressure and reducing the hydraulic pressure supplied to the output side hydraulic cylinder.