JPH05118420A - Hydraulic control device continuously variable transmission - Google Patents

Abstract

PURPOSE:To eliminate the deflection on the NULL value in selecting the drive frequency by selection-controlling the drive frequency of a working oil pressure control valve means to one value according to the driving condition and selection-controlling the NULL value of a speed change ratio hydraulic control means to one value according to the oil temperature state. CONSTITUTION:As for a continuously variable transmission 2, the speed change ratio is varied by the increase and decrease of the revolution radius of a belt 2A laid between a drive side pulley 4 and a driven side pulley 10 when the grove width between the fixed pulley part pieces 6 and 12 and the movable pulley part pieces 8 and 14 is increased and decreased by the hydraulic pressure. In this case, a primary pressure control valve 40 as speed change control valve is interposed in the first oil passage 36, and the first three-way solenoid valve 48 for the control of the primary pressure is allowed to communicate to the primary pressure control valve 40. A plurality of drive frequencies of the solenoid valve 48 and the oil temperature - NULL value map of the NULL value of the control valve 40 which corresponds to the oil temperature state are memorized in a control part 104. Then, the selection control to one drive frequency and one NULL value is performed according to the driving condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for a continuously variable transmission, and more particularly to a gear shift due to a deviation of the NULL value of the hydraulic control valve means for gear ratio when the drive frequency of the hydraulic control valve means for operation is switched. The present invention relates to a hydraulic control device for a continuously variable transmission that can prevent the occurrence of discontinuity and shock.

[0002]

2. Description of the Related Art In a vehicle, a transmission is interposed between an internal combustion engine and driving wheels. This transmission changes the driving force transmitted to the driving wheels in accordance with the traveling conditions of the vehicle that change over a wide range, and allows the internal combustion engine to exhibit its full performance. The transmission is provided with, for example, two pulleys each having a fixed pulley portion fixed to the rotating shaft and a movable pulley portion attached to the rotating shaft so as to be able to come into contact with and separate from the fixed pulley portion, and the pulley is wound around the pulley. And a groove width formed between both pulley parts of each pulley is hydraulically increased / decreased to increase / decrease the radius of gyration of the belt wound around the pulley to continuously change the belt ratio (gear ratio). There is a continuously variable transmission.

In this continuously variable transmission, the hydraulic pressure is controlled by the hydraulic control valve for gear ratio to change the gear ratio. The hydraulic pressure control valve for gear ratio is operated by controlling the hydraulic pressure for operation by the hydraulic control valve means for operation. The actuating hydraulic control valve means is composed of an electromagnetic valve or the like, and is controlled by the drive frequency which is the output value of the duty ratio.

Japanese Patent Application Laid-Open No. 64-44 discloses that the drive frequency of the hydraulic control valve means for operation is switched and controlled.
It is disclosed in Japanese Patent No. 348 and Japanese Patent Laid-Open No. 1-153851. The one disclosed in JP-A-64-44348 controls switching to a low drive frequency when the oil temperature is low according to the oil temperature state, in consideration of the fact that the viscosity increases as the oil temperature decreases. When the oil temperature is high, switching control is performed to a high drive frequency. JP-A-1-15385
The one disclosed in Japanese Patent Publication No. 1 controls switching to a high driving frequency at low speed and switching to a low driving frequency at high speed according to the vehicle speed at normal temperature.

[0005]

By the way, as shown in FIG. 6, the gear ratio hydraulic control valve means whose operating hydraulic pressure is controlled by the operating hydraulic control valve means has a duty ratio of the operating hydraulic control valve means. It has a characteristic that the output pressure changes rapidly with respect to the change. The duty ratio at which the gear ratio does not change at the sudden change point of the gear shift of this characteristic is called the NULL value. The NULL value of this gear ratio hydraulic control valve means is shown in FIG.
As shown in Fig. 3, the temperature fluctuates under the influence of the oil temperature and the driving frequency.

Therefore, as disclosed in the above-mentioned publication, when the driving hydraulic control valve means is driven by switching the driving frequency according to the driving condition, the NULL value is influenced by the oil temperature and the driving frequency. By doing so, there will be a deviation in the NULL value at the time of switching. This null
As shown in FIG. 8, the shift in the value causes a change in the shift speed, which causes discontinuity in the shift and a shock.

That is, the one disclosed in Japanese Patent Laid-Open No. 64-44348 controls the switching of the drive frequency according to the oil temperature, so that a shock-free control mode (neutral mode, hold mode) or a shock is generated. The switching control is performed in the control mode (drive mode) where there is little Further, the one disclosed in the above-mentioned Japanese Patent Laid-Open No. 1-153851 controls switching by the vehicle speed.

Therefore, in all of the publications, the driving frequency is switched, but the NULL value is deviated by the switching of the driving frequency, and the shift is discontinuous due to the deviation of the NULL value. There was a problem that a shock was generated.

Therefore, the applicant of the present invention has filed an application for a hydraulic control method in which the NULL value is switched and controlled according to the oil temperature state (Japanese Patent Laid-Open No. 1-153854).

However, in the one disclosed in this publication, the NULL value is calculated from a single oil temperature-NULL value map, so that the NULL value is appropriately set in accordance with the drive frequency that is switch-controlled according to the drive condition. However, there is a problem in that it is not possible to switch gears, and it is impossible to reliably prevent discontinuity of gear shifting and the occurrence of shocks.

[0011]

SUMMARY OF THE INVENTION Therefore, in order to eliminate the above-mentioned inconvenience, the present invention proposes both pulley part pieces, namely, a fixed pulley part piece and a movable pulley part piece which is attached to and detachable from the fixed pulley part piece. In a continuously variable transmission in which the groove width between the pulleys is increased / decreased by hydraulic pressure to increase / decrease the radius of gyration of the belt wound around the pulleys to continuously change the gear ratio, the hydraulic pressure is controlled to change the gear ratio. A gear ratio hydraulic control valve means is provided and an actuation hydraulic control valve means for controlling the actuation hydraulic pressure of the gear ratio hydraulic control valve means is provided, and the drive frequency of the actuation hydraulic control valve means corresponding to the drive condition is set. NUL of the hydraulic control valve means for gear ratios, which stores a plurality of data and corresponds to the oil temperature state for each of the plurality of drive frequencies.
An oil temperature-NULL value map of the L value is stored, and switching control is performed to any one of the plurality of drive frequencies according to the drive condition, and an oil temperature calculated from the oil temperature-NULL value map of the one drive frequency. It is characterized in that control means is provided for controlling the switching to a NULL value according to the state.

[0012]

According to the structure of the present invention, the control means has a plurality of drive frequencies and the oil temperature for each of the plurality of drive frequencies-NULL.
A value map is stored, and the control means controls switching to any one of the plurality of drive frequencies according to the drive condition, and the oil temperature of this one drive frequency-NUL.
By controlling the switching to the NULL value according to the oil temperature state calculated from the L value map, it is possible to eliminate the deviation of the NULL value when the drive frequency is switched.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings.

1 to 5 show an embodiment of the present invention. In FIG. 5, 2 is a belt drive type continuously variable transmission, 2A is a belt, 4 is a drive side pulley, 6 is a drive side fixed pulley section piece, 8 is a drive side movable pulley section piece, 10 is a driven side pulley, Reference numeral 12 is a driven side fixed pulley section piece, and 14 is a driven side movable pulley section piece.

The drive-side pulley 4 includes a drive-side fixed pulley portion 6 fixed to an input shaft 16 which is a rotary shaft, and the input shaft 1.
The input shaft 16 is movable in the axial direction of 6 and cannot rotate.
And a drive-side movable pulley piece 8 attached to the. Further, the driven side pulley 10 is also movable in the axial direction of the driven side fixed pulley portion 12 fixed to the output shaft 18, which is a rotating shaft, and the non-rotatable direction, like the driving side pulley 4. And a driven side movable pulley portion piece 14 that is mounted on the output shaft 18 as much as possible.

The drive side movable pulley portion piece 8 and the driven side movable pulley portion piece 14 have a first housing 20 and a second housing 20, respectively.
22 are mounted respectively, and first and second hydraulic chambers 24, 26 are formed respectively. Further, in the second hydraulic chamber 26 on the driven side, the driven side movable pulley portion is reduced in the direction of decreasing the groove width between the driven side fixed pulley portion piece 12 and the driven side movable pulley portion piece 14. Biasing means 2 including a spring for biasing the piece 14
8 is provided.

An oil pump 30 is provided on the input shaft 16. The suction side of the oil pump 30 communicates with the inside of the oil pan 34 via the oil filter 32. The discharge side of the oil pump 30 has the first and second hydraulic chambers 2
Nos. 4 and 26 are communicated with the first and second oil passages 36 and 38, respectively, and a primary pressure control valve 40, which is a shift control valve for controlling the primary pressure that is the input shaft sheave pressure, is provided in the middle of the first oil passage 36. To do.

In the first oil passage 36 on the oil pump 30 side of the primary pressure control valve 40, the third oil passage 4
The constant pressure control valve 44, which controls the line pressure (generally 5 to 25 〓 / 〓 ² ) to a constant pressure (3 to 4 〓 / 〓 ² ), is connected to communicate with the primary pressure control valve 40. The 4th oil passage 46 connects the 1st three-way solenoid valve 48 for primary pressure control.

In the middle of the second oil passage 38, a line pressure control valve 50 having a relief valve function for controlling the line pressure which is a pump pressure is connected by a fifth oil passage 52, and the line pressure control valve 50 is connected. The sixth oil passage 54 communicates with the line pressure control second three-way solenoid valve 56.

Further, in the middle of the second oil passage 38 closer to the second hydraulic chamber 26 than the portion where the line pressure control valve 50 communicates, a clutch pressure for controlling a clutch pressure, which is a hydraulic pressure acting on a hydraulic clutch 68 described later, is provided. The control valve 58 communicates with the seventh oil passage 60, and the clutch pressure control valve 58 is connected to the eighth oil passage 60.
The oil passage 62 connects the clutch pressure control valve third three-way solenoid valve 64.

Further, a constant control hydraulic pressure taken out from the constant pressure control valve 44 is supplied to the primary pressure control valve 40.
And a first three-way solenoid valve 48 for controlling the primary pressure, a line pressure control valve 50, and a second three-way solenoid valve 5 for controlling the line pressure.
6, and the clutch pressure control valve 58 and the clutch pressure control third three-way solenoid valve 64 are supplied to these valves 4 and 4 respectively.
The 0th, 44th, 48th, 50th, 56th, 58th, and 64ths are connected by a ninth oil passage 66, respectively.

The clutch pressure control valve 58 communicates with a later-described clutch hydraulic chamber 78 of the automatic starting clutch 68 by a tenth oil passage 70, and a pressure sensor 74 by an eleventh oil passage 72 in the middle of the tenth oil passage 70. To communicate. The pressure sensor 74 can directly detect the hydraulic pressure when controlling the clutch pressure in the hold mode, the start mode, etc., and contributes to commanding the detected hydraulic pressure to be the target clutch pressure. Further, in the drive mode, the clutch pressure becomes equal to the line pressure, which also contributes to the line pressure control.

The automatic starting clutch 68 is pushed by an input side casing 76 attached to the output shaft 18, a clutch hydraulic pressure chamber 78 provided in the casing 76, and a hydraulic pressure acting on the clutch hydraulic pressure chamber 78. Piston 80, an annular spring 82 for urging the piston 80 in the retreat direction, and a first pressure plate 84 movably provided by the pushing force of the piston 80 and the urging force of the annular spring 82. And a friction plate 86 on the output side and a second pressure plate 88 fixed to the casing 76.

When the clutch pressure, which is a hydraulic pressure applied to the clutch hydraulic chamber 78, is increased, the automatic starting clutch 68 pushes the piston 80 to bring the first pressure plate 84 and the second pressure plate 88 into close contact with the friction plate 86. , So-called combined state. On the other hand, the clutch hydraulic chamber 7
When the clutch pressure, which is the hydraulic pressure acting on 8, is lowered, the piston 80 is retracted by the urging force of the annular spring 82 to separate the first plate 84 and the second pressure plate 88 from the friction plate 86, and a so-called clutch disengaged state. become. In this way, the automatic starting clutch 68
Are coupled / disengaged by the clutch pressure, and the driving force output from the continuously variable transmission 2 is interrupted.

An input shaft rotation detection gear 90 is provided outside the first housing 20, and an input shaft side first rotation detector 92 is provided in the vicinity of the outer peripheral portion of the input shaft rotation detection gear 90.
An output shaft rotation detection gear 94 is provided outside the second housing 22, and a second rotation detector 96 on the output shaft side is provided near the outer peripheral portion of the output shaft rotation detection gear 94. From the rotation speed detected by the first rotation detector 92 and the second rotation detector 96, the engine rotation speed and the belt ratio (gear ratio) are grasped.

Further, the automatic starting clutch 68 is provided with an output transmission gear 98. This output transmission gear 9
Reference numeral 8 denotes a forward output transmission gear 98F and a reverse output transmission gear 98R, and third rotation detection for detecting the clutch output rotation speed, which is the rotation of the final output shaft 100, in the vicinity of the outer peripheral portion of the reverse output transmission gear 98R. A container 102 is provided. The third rotation detector 102 detects the clutch output rotation speed of the forward / reverse switching mechanism (not shown), the intermediate shaft, the final reduction gear, the differential mechanism, the drive shaft, and the final output shaft 100 that communicates with the wheels. Vehicle speed can be detected. Further, by detecting the rotation speeds detected by the second rotation detector 96 and the third rotation detector 102, it is possible to detect the clutch input rotation speed and the clutch output rotation speed on the input side and the output side before and after the automatic starting clutch 68, respectively. It is possible and contributes to the detection of the clutch slip amount.

In addition to various signals from the pressure sensor 74 and the first to third rotation detectors 92, 96 and 102, a carburetor throttle opening, a carburetor idle position, an accelerator pedal signal, a brake signal, a power mode option signal, A control unit 104 is provided for inputting various signals such as the shift lever position and performing control. In addition, this control unit 10
A signal from the oil temperature sensor 106 is input to 4.

The control unit 104 controls the belt ratio and the clutch disengagement state by various control modes in accordance with various input signals in order to control the first three-way solenoid valve 48 for primary pressure control and the second three-way solenoid valve 56 for line pressure control. , And controls the operation of the third three-way solenoid valve 64 for clutch pressure control.

The function of the input signal input to the control section 104 will be described in detail.

Shift lever position detection signal: Line pressure, ratio, clutch control required for each range by P, R, N, D, L, etc. range signals

Detecting signal of carburetor throttle opening ... Detecting engine torque from a memory input in the program in advance, and determining target ratio or target engine speed

Detecting signal of carburetor idle position ...... Improvement of accuracy in correction and control of carburetor throttle opening sensor

, Accelerator pedal signal: The driver's intention is detected by the state of depression of the accelerator pedal, and the control method during running or starting is determined.

, Brake signal: Detects whether the brake pedal is depressed or not, and determines the control direction such as clutch disengagement

, Power mode option signal: sports performance (or economy) of vehicle performance
Used as an option to

, Oil temperature signal: a signal corresponding to the oil temperature state of the hydraulic circuit, etc.

The oil temperature signal is, for example, the oil pan 34.
It is output from the oil temperature sensor 106 installed inside.

The continuously variable transmission 2 whose belt ratio (gear ratio) is controlled by the oil pressure is a primary pressure control valve which is a gear ratio hydraulic control valve means for controlling the oil pressure so as to change the belt ratio (gear ratio). 40 is provided, and a primary pressure control first three-way solenoid valve 48, which is an operating hydraulic control valve means for controlling the operating hydraulic pressure of the primary pressure control valve 40, is provided.

As shown in FIG. 4, the primary pressure control valve 40 has a spool valve body 110 reciprocally incorporated in a body 108. A large-diameter hole 112 and a small-diameter hole 114 are linearly provided in the body 108, and the large-diameter hole 11 is formed.
1st-5th hole parts 116-124 communicating with 2 and the small diameter hole 1
A sixth hole 126 communicating with 14 is provided. The spool valve body 110 includes first and second land portions 128 and 130 slidably incorporated in the large diameter hole 112 to open and close the second to fifth hole portions 118 to 124 and the small diameter hole 11.
4 is provided with a third land portion 134 that is slidably installed, and the first and second springs 134 and 136 are provided between the first land portion 128 and the body 108 and between the third land portion 132 and the body 108, respectively. It is installed.

The first hole portion 116 of the body 108 is connected to the first three-way solenoid valve 48. Second hole 118
Is open to the atmosphere. The third hole 120 is connected to the first hydraulic chamber 24 of the drive pulley 4. The fourth hole 122 is connected to the oil pump 30. The fifth hole portion 124 is open to the atmosphere. Sixth hole 126
Is connected to the constant pressure control valve 44.

The first three-way solenoid valve 48 has a control section 104.
Is driven by the drive frequency that is the output value of the duty ratio to control the operating hydraulic pressure of the primary pressure control valve 40. The primary pressure control valve 40 is actuated by this hydraulic pressure for operation, and controls the hydraulic pressure that acts on the first hydraulic chamber 24 so as to change the belt ratio (gear ratio).

As shown in FIGS. 1 and 2, the control section 104 includes a first hydraulic pressure control valve means, which is an operating hydraulic control means corresponding to a driving condition.
While storing a plurality of drive frequencies of the three-way solenoid valve 48,
N of the primary pressure control valve 40, which is the hydraulic control valve means for gear ratio, corresponding to the oil temperature state for each of these plurality of drive frequencies.
The oil temperature-NULL value map of the ULL value is stored. The control unit 104 performs switching control to any one of the plurality of drive frequencies according to the drive condition and sets a NULL value according to the oil temperature state calculated from the oil temperature-NULL value map of the one drive frequency. Switching control is performed.

Next, the operation will be described.

As shown in FIG. 5, the continuously variable transmission 2 operates the oil pump 30 located on the input shaft 16 to suck the oil in the oil pan 34 through the oil filter 32.

The pump pressure which is the oil pressure discharged from the oil pump 30, that is, the line pressure is the line pressure control valve 50.
Controlled by. The line pressure decreases when the amount of leakage from the line pressure control valve 50 is large, and conversely increases when the amount of leakage is small. The line pressure control valve 50 has a shift control characteristic that performs three-stage control for changing the line pressure in the full low state, the full over state, and the fixed ratio state.

The operation of the line pressure control valve 50 is controlled by a dedicated second three-way solenoid valve 56.
The line pressure control valve 50 operates following the operation of the three-way solenoid valve 56. The second three-way solenoid valve 56 is controlled by the control unit 104 at a duty ratio of a constant drive frequency. That is, the duty ratio of 0% means a state in which the second three-way solenoid valve 56 does not operate at all, and the output hydraulic pressure becomes zero. Also,
The duty ratio of 100% means that the second three-way solenoid valve 56 operates and the maximum output hydraulic pressure is the same as the control pressure. In this way, the second three-way solenoid valve 56 changes the output hydraulic pressure according to the duty ratio.

Therefore, the characteristic of the second three-way solenoid valve 56 is substantially linear, the line pressure control valve 50 can be operated in an analog manner, and the duty ratio of the second three-way solenoid valve 56 can be arbitrarily changed. The line pressure can be controlled.

The primary pressure for shift control is controlled by the primary pressure control valve 40. Like the line pressure control valve 50, the primary pressure control valve 40 is controlled by a dedicated first three-way solenoid valve 48. The first three-way solenoid valve 48 is similar to the second three-way solenoid valve 56 in the control unit 10
4 controls the primary pressure by varying the output hydraulic pressure to the primary pressure control valve 40.

The clutch pressure control valve 58 for controlling the automatic starting clutch 68 controls the clutch pressure.
When the maximum clutch pressure is required, it is connected to the line pressure side, and when it is set to the minimum clutch pressure, it is connected to the atmosphere side. The clutch pressure control valve 58, like the line pressure control valve 50 and the primary pressure control valve 40,
The operation is controlled by the dedicated third three-way solenoid valve 64, and a description thereof will be omitted.

The clutch pressure changes within the range from the minimum atmospheric pressure (zero) to the maximum line pressure. There are four basic patterns for controlling the clutch pressure. There are four basic patterns: (1), neutral mode (2), hold mode (3), start mode (4), and drive mode.

The basic pattern (1) is performed by a dedicated switching valve (not shown) that is interlocked with the shift operation, and the other basic patterns (2), (3), and (4) are the first to the first by the control unit 104. The duty ratio control of the three-way three-way solenoid valves 48, 56, 64 is performed.

In particular, in the state (4), the clutch pressure control valve 58 connects the seventh oil passage 60 and the tenth oil passage 70 so that the maximum pressure is generated, and the clutch pressure is equal to the line pressure. Become.

The primary pressure control valve 40, the line pressure control valve 50, and the clutch pressure control valve 58 are controlled by the output hydraulic pressure from the first to third three-way solenoid valves 48, 56 and 64, respectively. These first to third three-way solenoid valves 4
The control hydraulic pressure for controlling 8, 56 and 64 is a constant hydraulic pressure created by the constant pressure control valve 44. This control oil pressure is lower than the line pressure, but is a stable and constant pressure. The control oil pressure is the primary pressure control valve 4
0, the line pressure control valve 50, and the clutch pressure control valve 58 are stabilized.

Next, the control of the continuously variable transmission 2 will be described.

The continuously variable transmission 2 is hydraulically controlled, and has an appropriate line pressure from the control unit 104, a primary pressure for changing the gear ratio, and an automatic starting clutch 68.
The clutch pressures for surely connecting the two are secured.

FIG. 1 is a block diagram of hydraulic control of the continuously variable transmission 2. The hydraulic control will be described.

The control unit 104 controls the throttle opening THRT.
The final target engine speed NESPRF is calculated (100) from the vehicle speed NCO and the engine speed, and the proportional gain K is calculated.
It is multiplied by p (102) and passed through the limiter 1 (104). This value is multiplied by an integral gain (106), and a plurality of drive frequencies (for example, 12.5) are switched and controlled according to the drive condition.
Hz, 25 Hz, 50 Hz, 100 Hz), the NULL value calculated from the oil temperature-NULL value map corresponding to one driving frequency is adjusted (108), and this value (108) and the limiter 1 are passed through (104). Add and subtract values (110)
Then, through the limiter 2 (112), it is output as the ratio solenoid duty OPWRAT, and the first three-way solenoid valve 4
Drive eight.

Next, the hydraulic control will be described with reference to FIG.

The control unit 104 starts control (20
0) Then, regarding the drive frequency of the first three-way solenoid valve 48, a plurality of stored drive frequencies, for example, 12.5H
It is determined (202) which value the drive frequency of z, 25 Hz, 50 Hz, and 100 Hz should be in accordance with the drive condition.

If the drive frequency is switched to 12.5 Hz, the oil temperature at this drive frequency of 12.5 Hz-NUL
Nominal NULL value NNU according to oil temperature condition from L value map
L is determined (204), the nominal NULL value NNUL is switched to, and another shift control (212) is performed to perform step (20).
Return to 2).

When the drive frequency is switched to 25 Hz, the nominal NULL value NNUL corresponding to the oil temperature state is obtained from the oil temperature-NULL value map of the drive frequency of 25 Hz (206) and switched to this nominal NULL value NNUL. , Other shift control (212) is performed, and the process returns to step (202).

When the drive frequency is switched to 50 Hz, the nominal NULL value NNUL corresponding to the oil temperature condition is obtained from the oil temperature-NULL value map of the drive frequency of 50 Hz (208) and switched to this nominal NULL value NNUL. , Other shift control (212) is performed, and the process returns to step (202).

When the drive frequency is switched to 100 Hz, the nominal NULL value NNUL corresponding to the oil temperature condition is obtained from the oil temperature-NULL value map of the drive frequency of 100 Hz (210) and switched to this nominal NULL value NNUL. , Other shift control (212) is performed and the step (20
Return to 2).

In this way, the control unit 104 controls switching to any one of the plurality of drive frequencies of the first three-way solenoid valve 48 according to the drive condition, and calculates from the oil temperature-NULL value map of this one drive frequency. By performing the switching control to the NULL value of the primary pressure control valve 40 according to the oil temperature state, it is possible to eliminate the deviation of the NULL value when the drive frequency is switched, as shown in FIG.

Therefore, in consideration of the deviation of the NULL value caused by the difference of the driving frequency, the primary pressure control valve 40
It is possible to reliably control discontinuity of gear shift and occurrence of shock, and to provide a comfortable riding sensation without giving the driver a feeling of discomfort.

In this embodiment, the primary pressure control valve 40 and the first three-way solenoid valve 48 have been described as an example, but the line pressure control valve 50 and the second three-way solenoid valve 56,
By similarly controlling the clutch pressure control valve 58 and the third three-way solenoid valve 64, the control changes can be smoothed.

Further, the present invention can be applied not only to the continuously variable transmission but also to other control devices for controlling the fluid by the drive frequency and switching control of the drive frequency, and has great versatility.

Moreover, it can be dealt with only by changing the program of the control unit, which does not increase the cost and is economically advantageous.

[0069]

As described above, according to the present invention, the control means controls switching to any one of a plurality of drive frequencies of the hydraulic control valve means for operation according to the drive condition, and the oil temperature of the one drive frequency is controlled. -NUL of the gear ratio hydraulic control valve means according to the oil temperature state calculated from the NULL value map
By controlling the switching to the L value, it is possible to eliminate the deviation of the NULL value when the driving frequency is switched.

Therefore, the hydraulic pressure for actuation of the gear ratio hydraulic control valve means can be controlled in consideration of the deviation of the NULL value caused by the difference in the drive frequency, so that the discontinuity of the gear shift and the occurrence of the shock can be surely performed. Therefore, it is possible to prevent the driver from feeling uncomfortable and obtain a comfortable riding feeling.

[Brief description of drawings]

FIG. 1 is a block diagram of a hydraulic control device showing an embodiment of the present invention.

FIG. 2 is a flow chart of hydraulic control according to the present invention.

FIG. 3 is a time chart of duty ratio, pressure, vehicle speed, and ratio according to the present invention.

FIG. 4 is an enlarged sectional view of a primary pressure control valve.

FIG. 5 is a schematic configuration diagram of a continuously variable transmission.

FIG. 6 is a diagram showing a relationship between a duty ratio and a NULL value.

FIG. 7 is a diagram showing the relationship between the oil temperature and the NULL value with respect to the drive frequency.

FIG. 8 is a time chart of a conventional duty ratio, pressure, vehicle speed, and ratio.

[Explanation of symbols]

 2 continuously variable transmission 2A belt 4 driving side pulley 10 driven side pulley 40 primary pressure control valve 44 constant pressure control valve 48 primary pressure control first three-way solenoid valve 50 line pressure control valve 56 line pressure control second three-way solenoid valve 58 clutch pressure control valve 64 third three-way solenoid valve for clutch pressure control 68 automatic starting clutch 74 pressure sensor 92 first rotation detector 96 second rotation detector 102 second rotation detector 104 control unit 106 oil temperature sensor

Claims (1)

[Claims] 1. A groove width between the fixed pulley portion piece and a movable pulley portion piece attached to the fixed pulley portion piece so as to be able to come into contact with and separate from the fixed pulley portion piece is increased or decreased by hydraulic pressure and wound around the both pulleys. In a continuously variable transmission for continuously changing a gear ratio by increasing or decreasing the radius of gyration of a belt, a gear ratio hydraulic control valve means for controlling a hydraulic pressure to change the gear ratio is provided, and the gear ratio hydraulic control valve is provided. An operating hydraulic control valve means for controlling the operating hydraulic pressure of the means is provided, and a plurality of drive frequencies of the operating hydraulic control valve means corresponding to the drive conditions are stored, and each of the plurality of drive frequencies corresponds to an oil temperature state. An oil temperature-NULL value map of the NULL value of the gear ratio hydraulic control valve means is stored, and switching control is performed to any one of the plurality of drive frequencies according to the drive condition, and the one drive frequency is controlled. A hydraulic control device for a continuously variable transmission, comprising control means for switching control to a NULL value according to an oil temperature state calculated from a number of oil temperature-NULL value maps.