JPH0617923A - Hydraulic control unit of continuously variable transmission for vehicle - Google Patents

Abstract

PURPOSE:To prevent belt slip and enhance acceleration responsiveness by correcting a second primary pulley controlling hydraulic pressure value by a predetermined amount if a primary pully controlling hydraulic pressure signal value does not reach a desired control hydraulic pressure after the vehicle has reached a low-speed running range. CONSTITUTION:A continuously variable transmission 2 comprises a steel belt 13 hung between a primary 9 and secondary 12 pulley and provides a desired transmission gear ratio by changing the effective diameter of each pulley 9, 12 through the axial displacement of the movable side pulley member 902, 122 of each pulley 9, 12 by a hydraulic actuator 15, 16. Governed pressure oil is fed to and discharged from each hydraulic actuator 15, 16 via a transmission gear ratio control valve by a hydraulic control unit. In this case, delivery pressure introduced into the primary side hydraulic actuator 15 is detected and when the vehicle speed is at or below a predetermined value a primary control signal is corrected by a predetermined amount so that the delivery pressure detected equals a preset desired value.

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 for a vehicle, in which the winding diameter ratio of a belt wound around a pair of pulleys is changed by switching operation of a hydraulic actuator, and a continuously variable transmission is provided. The present invention relates to a hydraulic control device for a vehicle continuously variable transmission that eliminates slippage between a primary pulley and a drive belt after the vehicle has stopped.

[0002]

2. Description of the Related Art This continuously variable transmission is provided with a primary piston and a secondary piston, and a regulator valve is regulated by an electromagnetic control valve so that a line pressure according to operating information of a vehicle is obtained. It is supplied to the hydraulic piston on the side to obtain the belt clamping force. Also, by supplying this line pressure to the gear ratio control valve,
The gear ratio control hydraulic pressure, which is obtained by further adjusting the pressure using the electromagnetic control valve for the same gear ratio control valve, is supplied to the hydraulic piston on the primary pulley side to adjust the gear ratio so that it becomes the target gear ratio according to the vehicle driving information. It is configured to be changed to perform continuously variable transmission.

[0003]

By the way, in order to transmit the torque in the speed change portion (between the belt and the pulley) of the continuously variable transmission, it is necessary for the pulley to firmly pinch (press) the belt. If the force pressing the belt is weak, slip will occur between the cone surface of the pulley and the drive belt.

Particularly, in the conventional shift control device, when the vehicle is stopped due to deceleration, the gear ratio is increased in preparation for the next start. For this reason, it is necessary to open the passage leading to the primary hydraulic chamber to the oil drain hole to discharge the oil and move the primary pulley to the stopper (maximum gear ratio state). Further, since the torque is absorbed by the fluid coupling during the vehicle deceleration or stop, the primary pulley hardly rotates or at all, the centrifugal force does not act on the oil in the hydraulic chamber, and the oil in the hydraulic chamber continues to be discharged. , Oil is exhausted up to the center of the shaft where the oil passage is located.

By the way, in starting the vehicle when the pulley is in contact with the stopper, if the oil enters the hydraulic chamber of the secondary pulley, the gap between the secondary pulley becomes small, and the belt wound around the secondary pulley is pushed out in the outer peripheral direction, and the belt is Be pulled. When the primary pulley hits the stopper (because the pulley does not work), the reaction force is generated between the belt pulleys even on the primary pulley side, and the belt does not slip. However, the pulley that is likely to occur when the vehicle starts after a sudden stop is the stopper. If you don't hit
Even if oil enters the hydraulic chamber of the secondary pulley, the primary pulley first moves in the axial direction, so that a reaction force cannot be obtained between the belt and the cone surface of the sheave until it hits the stopper, causing belt slip.

In order to face this, conventionally, as shown in FIG.
As shown in (b), prior to starting, the hydraulic pressure is periodically introduced into the hydraulic chamber of the primary pulley (only for the hydraulic pressure introduction time t determined in the predetermined hydraulic pressure introduction period To) to keep the hydraulic pressure in the hydraulic chamber and to keep the sheave of the sheave. Prevents belt slip between the cone surface and the belt. This is because if there is oil in the hydraulic chamber of the primary pulley, a discharge pressure is generated when the pulley moves, and a large reaction force is generated between the pulley and the belt, so that the belt can be clamped.

However, in the conventional method, since the hydraulic pressure is introduced at the expected hydraulic pressure introduction period To and the hydraulic pressure introduction time t,
If the primary hydraulic pressure Pp varies and falls below the target value Po, it is not sufficient as a measure against belt slip, and belt slip occurs when starting. That is, a slip easily occurs between the sheave cone surface and the drive belt, an uncomfortable shock occurs due to the slip, and the durability of the belt and the sheave cone surface is impaired, which is a problem.

On the other hand, when the primary oil pressure Pp is too large and exceeds the target value Po, it changes to the small gear ratio (high gear stage) side, so the acceleration response at the start is low (acceleration is slow). There is a problem.

An object of the present invention is to prevent belt slip of a continuously variable transmission and ensure acceleration responsiveness.

[0010]

In order to achieve the above-mentioned object, the present invention comprises a primary pulley and a secondary pulley around which a drive belt is wound, and the gear ratio is adjusted by adjusting the gap between the pulleys. In a continuously variable transmission for a vehicle that changes continuously, a primary-side hydraulic actuator that adjusts the gap between the primary pulleys, a secondary-side hydraulic actuator that adjusts the gap between the secondary pulleys, and a regulator that adjusts the hydraulic pressure from a hydraulic source. A valve, a gear ratio control valve to which the discharge pressure from the regulator valve is introduced, and a hydraulic pressure detection means arranged in an oil passage for guiding the discharge pressure from the gear ratio control valve to the primary side hydraulic actuator, An electromagnetic control valve that adjusts the gear ratio control valve, and controls the electromagnetic control valve based on the operating state of the vehicle Child control means, and the electronic control means corrects the electromagnetic control valve drive signal so that the detection value from the hydraulic pressure detection means becomes a preset target when the vehicle speed of the vehicle is equal to or lower than a predetermined vehicle speed. It is characterized by doing.

[0011]

When the vehicle reaches the low speed traveling range, the electronic control means presets the next primary pulley control hydraulic pressure value unless one value of the primary pulley control hydraulic pressure signal reaches the preset target control hydraulic pressure. Since the correction amount is corrected and set, the primary pulley control oil pressure can be maintained at the target control oil pressure, and the hydraulic actuator of the primary pulley operates so as to narrow the pulley gap of the primary pulley.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The hydraulic control system for a vehicle continuously variable transmission shown in FIGS. 1 and 2 is attached to a continuously variable transmission 2 in a power transmission system Pw connected to an engine 1 of the vehicle. Here, the engine 1 is an electronically controlled fuel injection type four-cycle engine, and various devices such as an injector (not shown) and a spark plug for igniting an air-fuel mixture are placed under the control of an electronic control means (not shown) of the engine. A CVT ECU 3 which is an electronic control unit of the continuously variable transmission (CVT) 2 in the power transmission system Pw is connected to this control unit, and the operation information of the engine 1 is transmitted to the CVT ECU 3 from the electronic control unit of the engine. Is configured. The CVTECU 3 includes a pair of electromagnetic control valves 4 for hydraulically controlling the gear ratio i of the continuously variable transmission 2.
5 is connected.

A continuously variable transmission 2 is connected to the crankshaft of the engine 1 via a fluid coupling 6 for smoothly transmitting the output of the engine to the power transmission system Pw side and a planetary gear type forward / reverse switching device 7. . Here, the continuously variable transmission 2
Is a primary pulley 9 having a primary shaft 8 integrally coupled to the output shaft of the forward / reverse switching and transmission 7.
And a secondary pulley 12 having a secondary shaft 11 that outputs a rotational force to the speed reducer 10 side, and a steel belt 13 is stretched over the primary pulley 9 and the secondary pulley 12. The secondary shaft 11 is configured to transmit a rotational force to a drive wheel (not shown) via the transmission 10 and the differential 14.

Both the pulleys 9 and 12 are divided into two parts, and the movable pulley members 901 and 121 are fixed pulley members 902 and 1, respectively.
It is fitted on the outer surface 22 such that it cannot rotate relative to it and can be separated and contacted at a relative interval. A primary cylinder 15 and a secondary cylinder 16 are mounted on the movable pulley members 901 and 121 as hydraulic actuators for operating the relative distance between the movable pulley members 901 and 121 and the fixed pulley members 902 and 122. It should be noted that the pair of rotation sensors 17 and 18 for detecting the rotational speeds Wp and Ws of the primary pulley 9 and the secondary pulley 12 are the actual speed ratio in.
(= Wp / Ws) is mounted as a detection means.

Here, the gear ratio of the continuously variable transmission changes as follows. Fixed pulley material 902 of the primary pulley 9
On the other hand, the winding diameter of the primary pulley is increased by bringing the movable pulley member 901 closer, and the winding diameter of the secondary pulley 12 is made smaller than the fixed pulley member 122 of the secondary pulley 12 to reduce the winding diameter. As a result, the continuously variable transmission reduces its actual speed ratio in (primary speed Wp / secondary speed Ws), that is, a small speed ratio (high speed), and when it operates in reverse, a large speed ratio (low speed) is achieved. You can do it. A hydraulic circuit of such a continuously variable transmission 2 will be described with reference to FIG. This hydraulic circuit is provided with an oil pump 20, and its discharged oil is distributed to the fluid coupling 6, the forward / reverse switching 21 and the reverse clutch 22 of the forward / reverse switching / transmission unit 7, the primary cylinder 15 and the secondary cylinder 16 of the continuously variable transmission 2. Supplied.

Here, the oil pump 20 is driven according to the rotation of the engine to change its oil pressure. Therefore, the maximum allowable pressure of the oil pump 20 is regulated by the relief valve 23, and the first electromagnetic control valve 4 and the regulator valve 24 are pressure-regulated so as to maintain a predetermined line pressure. A part of the line pressure passage 25 is connected to the clutch pressure control valve 26, and the pressure oil whose pressure is adjusted to a set value by the valve is supplied to the manual valve 28 via the clutch oil passage 27. The manual valve 28 is interlocked with a manual switching lever (not shown) for shifting the shift speed, and is provided with each range of forward side D, 2, L, reverse side R range, and neutral N and parking P range. , Forward / reverse switching and transmission unit 7 to achieve a gear train corresponding to each range
The forward clutch 21 and the reverse clutch 22 and the changeover switching valve (not shown) are switched. The manual valve 28 is provided with a gear shift position sensor 34 for outputting each gear shift position signal, and the gear shift signal indicates the CVTECU3.
Is output to.

In the manual valve 28, the forward clutch 21 is engaged in this range on the forward drive side D, 2, L, and at this time, the engine rotation is directly transmitted to the continuously variable transmission 2 via the forward / reverse switching device 7, while In the reverse range R range, the engine rotation is reversed and transmitted to the continuously variable transmission 2. A part of the line pressure path 25 is branched and pressure-reduced and adjusted to a set value by the pressure control modulator valve 29, and the hydraulic pressure is supplied to the electromagnetic control valves 4 and 5. Based on the hydraulic pressure, the electromagnetic control valve 5 regulates the shift control hydraulic pressure Pc according to the target gear ratio. The electromagnetic control valve 5 is connected to the CVTECU 3 and outputs a shift control oil pressure Pc according to the gear ratio to a gear ratio control valve 30 described later.

The primary cylinder 15 and the secondary cylinder 16 of the continuously variable transmission 2 are respectively connected to the main port 301 and the sub port 302 of the gear ratio control valve 30, and particularly the secondary cylinder 16 is also directly connected to the line pressure passage 25. . Here, the gear ratio control valve 30 includes the main and sub ports 30.
1, 302, a control port 303 that receives the shift control oil pressure Pc of the electromagnetic control valve 5, and a pressure adjusting port 3 that receives the adjusting pressure from the pressure control modulator valve 29.
04, the drain port X communicating with the oil tank 31 is provided, and the switching control of the oil passage is performed by the spool valve 32. Here, the spool 32 has its control port 303
The portion opposite to and receives the shift control hydraulic pressure Pc to the left, and the other end receives the adjusting pressure and the spring force in the opposite direction, and switches and moves to the balance position (position where the pressure adjusted state can be maintained). In this case, the drain port X is closed in accordance with the right movement of the spool 32 (the shift control hydraulic pressure Pc is reduced), is completely closed after a certain movement, and is further closed after the certain movement.
01 and the auxiliary port 302 increase in communication state, the primary pulley control hydraulic pressure Pp of the primary cylinder 15 is increased (secondary pulley control pressure is always line pressure),
It is possible to reduce the actual speed ratio in to a small speed ratio (high speed), conversely decrease the control oil pressure Pp, and increase the actual speed ratio in to a high speed ratio (low speed).

The main part of the CVTECU 3 is composed of a microcomputer, and the built-in storage circuit is shown in FIG.
Of the pressure regulation period calculation map, the open time calculation map of FIG.
The main routine of the CVTECU3 of FIG. 8 and P of FIG.
Each control program of the low speed control routine for the N range, the low speed control routine for the running range of FIG. 10, the setting routine of the intermittent hydraulic pressure output to the primary pulley of FIG. 11, and the execution routine of the intermittent hydraulic pressure output of the primary pulley of FIG. Amnestics are being processed.

Here, the CVTECU 3 as the shift control means controls the electromagnetic control valve 5 so as to regulate the shift control oil pressure for switching the gear ratio control valve to a pressure regulated state corresponding to the target gear ratio i. Further, this shift control means takes in the pulley control hydraulic pressure Pp of the primary pulley from the pulley control hydraulic pressure sensor 33, and the value of the primary pulley control hydraulic pressure Pp is preset when the shift control to the target speed change ratio in the low speed traveling range of the vehicle is performed. If the target control oil pressure Po is not reached, the next solenoid valve drive signal is corrected and set by a preset correction amount Δp (the correction amount is achieved by the introduction time correction term Δtn described later). It has the function. Hereinafter, a hydraulic control device for a vehicle continuously variable transmission according to the present embodiment will be described with reference to the control programs shown in FIGS.

In this embodiment, the engine is started by operating an ignition key (not shown), and the CVT
The control in the electronic control means of the ECU 3 and the engine (not shown) is also started. When the control is started, the CVTECU3 executes the main routine of FIG. Here, first, in step s1, the initial setting and the detection data of each sensor are read, and, for example, the primary pulley 9 and the secondary pulley 1 are read.
The two rotational speeds Wp and Ws of 2, the throttle opening θa from the electronic control means of the engine (not shown), the engine rotational speed Ne and the like are fetched and stored in a predetermined area.

In step s2, it is determined whether the vehicle speed V according to the rotation speed Ws of the secondary pulley 12 is an extremely low speed or a judgment value Va indicating a stop or less, and if it is Va or less, step s3.
If not, go to step s6 and go to CV
T Perform normal control. In the CVT normal control, a well-known program, that is, the target engine speed Neo corresponding to the throttle opening θs is calculated by a target engine speed Neo calculation map (not shown) according to the characteristics of FIG. 7, and the same value is reached. Then, CVTECU3 sets the target engine speed Ne.
The process of increasing the gear ratio is continuously performed so that o is maintained.

At step s3 of the main routine, it is judged whether or not the current gear shift range is the P or N range based on the gear stage signal. The low range control routine for the traveling range in step s5 is performed.

In the low speed control routine for the P and N ranges, as shown in FIG. 9, it is judged in step e1 whether or not the control is currently performed by the P and N range control flag PRFLG, and if the control is in progress (PRFLG = 1), the step is executed. At e2, it is determined whether or not the primary rotation speed Wp exceeds a determination value Wp1 for whether or not the vehicle has left the starting range.
In step 3, the low speed control flag PRFLG is cleared and step e6
Otherwise go directly to step e6. In step e1, low speed control flag PRFLG = 0 and in step e4
Is reached, it is determined whether or not the primary rotation speed Wp is below the determination value Wp2 for determining whether or not the primary rotation speed has reached the starting range. If it is below, the low speed control flag PRFLG =
The process proceeds to step e6 as 1, otherwise proceeds directly to step e6. In step e6, if the P / N range control flag PRFLG is not 1, the process returns to the main routine. Otherwise, in the low speed control range, the process proceeds to step e7, in which the control oil pressure Ps (line pressure) of the secondary pulley is set to the minimum value (preset). ), The primary pulley hydraulic pressure is intermittently output in step e8, and the process returns to the main routine.

Prior to the description of the intermittent output of the primary pulley hydraulic pressure, the low speed control routine for the traveling range is shown in FIG.
Follow along. In step f1, it is determined whether or not the control is currently performed by the control flag PRFLG that was set last time, and in control (PRFLG = 1), in step f2, the primary rotation speed Wp exceeds the determination value Wp1 that determines whether or not the primary speed Wp has left the start range. It is judged whether or not there is, and if it exceeds, step f
In step 3, the low speed control flag PRFLG is cleared and step f6
Otherwise go directly to step f6. In step f1, low speed control flag PRFLG = 0 and in step f4
Is reached, it is determined whether or not the primary rotation speed Wp is below a determination value Wp2 that has reached the start range.
If it is 1, the process proceeds to step f6, and if not, the process directly proceeds to step f6.

At step f6, the low speed control flag PRFL is set.
If G = 1 is not satisfied, the process returns to the main routine. Otherwise, in the low speed control range, the process proceeds to step f7, where it is determined whether the time after the vehicle has stopped has passed a predetermined time. Ps or line pressure Pl
Is set to the maximum value to enhance the belt pressing force,
The primary pulley hydraulic pressure is intermittently output in step f10, and the process returns to the main routine. On the other hand, when the time after the vehicle is stopped has passed the predetermined time, the process for strengthening the belt pressing force is canceled, and in step f9, the target secondary pulley hydraulic pressure Ps is released.
Then, the normal calculation process of the line pressure Pl is started. in this case,
The input torque T is calculated from the throttle opening and the engine speed, the line pressure Pl is calculated in the normal process based on the line pressure Pl from the current gear ratio i and the current vehicle speed V, and the duty output corresponding to the target line pressure Pl is electromagnetically controlled. The pressure is output to the valve 4, and the regulator valve 24 operates to adjust the line pressure Pl in accordance with the output to correct and hold the line pressure Pl at a target value.

Next, the primary pulley hydraulic pressure intermittent output setting in step f10 and step e9 in FIG. 9 will be described with reference to FIG. Here, the basic time is set first.
That is, when step g1 is reached, the hydraulic pressure introduction cycle Tint = f1 (P1, Toil) into the primary hydraulic chamber (FIG. 3).
(See (b)) from the line pressure Pl and the oil temperature, the cycle T of FIG.
It is calculated by the int calculation map. Period Ti here
According to the nt calculation map, the cycle Tint is the line pressure Pl.
And the oil temperature Toil are set to be large and high, and are set to be long, and the line pressure Pl and the oil temperature Toil are set to be small and set to be short.

Then, when step g2 is reached, the oil pressure introduction time tinl = f2 (Pl, To
il) (see FIG. 3B), line pressure Pl and oil temperature To
It is calculated from il using the hydraulic pressure introduction time tinl calculation map of FIG. According to the oil pressure introduction time tinl calculation map here, the oil pressure introduction time tinl is set shorter as the line pressure Pl and the oil temperature Toil are higher, and the line pressure P
The smaller l and the oil temperature Toil are, the longer the value is set.
By such processing of steps g1 and g2, the hydraulic pressure value of the hydraulic pressure introduction cycle Tint and the hydraulic pressure introduction time tinl and the viscosity of the oil can be corrected.

When step g3 is reached, this step g3
It is determined whether or not the first time has been reached, and at the first time, step g4
Then, the control variable is initialized, that is, the introduction time correction term Δtn = 0 is processed in step g5. When it is determined that the step g3 has not been reached for the first time and the step g6 is reached,
It is judged whether or not the previous primary pressure Pp has reached a preset target control oil pressure Po. For example, if it has reached as shown by reference sign m3 in FIG. 3 (a), the process proceeds to step g7, and the introduction time The correction term Δtn is set to Δtn = Δtn-1−ΔtHP
Correct as follows. On the contrary, in step g6, when the previous primary pressure Pp does not reach the preset target control oil pressure Po, for example, as shown by reference signs m1 and m2 in FIG. Correction term Δtn
Is increased and corrected as Δtn = Δtn-1 + ΔtHM.

Here, ΔtHP and ΔtHM are solenoid valve control duty correction terms for reducing the primary pressure when the primary pressure reaches the target pressure Po, respectively, and increase the primary pressure when the primary pressure does not reach the target pressure Po. In the present embodiment, it is given as a constant value, but it may be variable according to the output of the hydraulic sensor 33. Thereafter, in step g9, the target introduction period T is set to T (= Tint), and the target introduction time t
Is calculated as t (= tinl + Δtn).
However, the target introduction time t is within a certain range (tmin ≦ t ≦ tm
ax).

The target introduction period T and the target introduction time t thus set are sequentially adopted in the routine for intermittently outputting the hydraulic pressure to the primary pulley shown in FIG. The intermittent hydraulic pressure output execution routine is executed by interrupting the main routine every predetermined time. That is, when step h1 is reached, the current time is set to the area TIMEO.
In step h2, the process waits for the target introduction time t to elapse, that is, while the current time TIME ≦ TIMEO + t, the process proceeds to step h3, in which the hydraulic pressure supply processing to the primary hydraulic chamber, that is, the electromagnetic control valve 5 is performed. The gear ratio control valve 30 is operated to open and the oil of the line pressure 25 is sent to the primary cylinder 15 for the target introduction time t. Step h
When step h4 is directly reached from step 3 and step h2,
The time to start the next output, that is, the target introduction period T is T
Time t-n obtained by adding to IMEO (t in FIG. 3B)
1, t2, t3) are calculated and stored in a predetermined area, and the process returns to the main routine.

By executing the hydraulic pressure intermittent output execution routine as described above, for example, as shown in FIG. 3B, the hydraulic pressure of the hydraulic circuit to the primary cylinder is controlled. The primary oil pressure changes. As a result, in the low speed control range, the primary hydraulic pressure Pp of the primary cylinder 15 is maintained at the target hydraulic pressure Po, so that the hydraulic chamber of the primary pulley can be filled with oil, and the pressing force to the steel belt 13 is applied. Given. Therefore, the occurrence of belt slip can be reduced even if the rotation speed of the primary pulley sharply increases due to a start request. On the contrary, when the primary hydraulic pressure Pp is too large and exceeds the target value Po, the primary hydraulic pressure Pp is reduced to maintain the primary hydraulic pressure Pp at the target hydraulic pressure Po, so that the gear ratio can be reliably controlled to the target value, and the acceleration response at the time of starting It is possible to secure the sex. In case of failure of the oil pressure sensor 33, the opening time of the oil pressure circuit to the oil chamber on the primary pulley side increases or decreases within a control range centered on a certain reference value (oil temperature and line pressure are stored in the memory as parameters). You may let it be done.

[0033]

As described above, the hydraulic control system for a continuously variable transmission for a vehicle according to the present invention corrects the primary pulley hydraulic control signal in accordance with the output of the hydraulic sensor when the vehicle reaches the low speed traveling range. Therefore, the primary pulley control hydraulic pressure can be kept at the target control hydraulic pressure, and the hydraulic actuator of the primary pulley can be filled with oil to secure the pressing force against the belt, so that the primary pulley cone surface can be maintained even when starting. It is possible to eliminate the occurrence of slippage with the belt, prevent uncomfortable shocks associated with this slippage, and ensure the durability of the belt and the sheave cone surface. Further, the primary oil pressure is set to the target oil pressure P.
Since it is held at o, it is possible to control the gear ratio to a target value with good responsiveness, and it is also possible to improve the driver's mileage when starting and fuel consumption. Further, according to the present invention, by changing the hydraulic pressure supplied to the secondary pulley between the P and N ranges and the running range, for example, the P and N ranges do not start running immediately, so the pump loss is the minimum necessary hydraulic pressure. In addition, the belt slip can be surely prevented by setting the maximum hydraulic pressure value or the hydraulic pressure according to the running state so that the belt does not slip when running in the running range.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a main part hydraulic circuit and a control system of a hydraulic control device for a vehicle continuously variable transmission according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a power transmission system of a vehicle including the hydraulic control device of FIG.

3A is a waveform diagram of a primary hydraulic pressure in the hydraulic control device of FIG. 1, and FIG. 3B is a waveform diagram showing an opening / closing operation of a hydraulic circuit communicating with a primary cylinder in the hydraulic control device of FIG.

FIG. 4A is a waveform diagram of a primary hydraulic pressure in a conventional hydraulic control device, and FIG. 4B is a waveform diagram showing an opening / closing operation of a hydraulic circuit communicating with a primary cylinder in the conventional hydraulic control device.

5 is a characteristic diagram of a hydraulic pressure introduction period calculation map adopted by the CVTECU in the hydraulic control device of FIG.

FIG. 6 is a characteristic diagram of a hydraulic pressure introduction time calculation map adopted by CVTECU in the hydraulic control device of FIG.

FIG. 7 is a characteristic diagram of a torque calculation map used by the electronic control device in the hydraulic control device of FIG.

8 is a flowchart of a main routine adopted by the electronic control device in the hydraulic control device of FIG.

9 is a diagram illustrating P and N adopted by the electronic control unit in the apparatus of FIG.
It is a flow chart of a low speed control routine for ranges.

10 is a flowchart of a low-speed control routine for a travel range adopted by the electronic control device in the device of FIG.

11 is a flowchart of a routine for setting an intermittent hydraulic pressure output to a primary pulley adopted by the electronic control unit in the apparatus of FIG.

12 is a flowchart of an execution routine of intermittent hydraulic pressure output to a primary pulley adopted by an electronic control unit in the apparatus of FIG.

[Explanation of symbols]

 1 Engine 2 Continuously Variable Transmission 3 CVT ECU 4 Electromagnetic Control Valve 5 Electromagnetic Control Valve 9 Primary Pulley 901 Movable Pulley Material 902 Fixed Pulley Material 12 Secondary Pulley 121 Movable Pulley Material 122 Secondary Pulley 13 Steel Belt 15 Primary Cylinder 16 Secondary Cylinder 17 Rotation Sensor 18 Rotation Sensor 24 Regulator Valve 30 Gear Ratio Control Valve 34 Gear Shift Position Sensor Ws Secondary Pulley Rotational Speed Wp Primary Pulley Rotational Speed V Vehicle Speed

Claims (1)

[Claims] 1. A continuously variable transmission for a vehicle, which comprises a primary pulley and a secondary pulley around which a drive belt is wound, and which continuously changes the gear ratio by adjusting the gap between the pulleys. A primary hydraulic actuator that adjusts the clearance, a secondary hydraulic actuator that adjusts the clearance of the secondary pulley, a regulator valve that adjusts the hydraulic pressure from the hydraulic source, and a gear ratio control that introduces the discharge pressure from the regulator valve. A valve, a hydraulic pressure detection means arranged in an oil passage for guiding the discharge pressure from the gear ratio control valve to the primary hydraulic actuator, an electromagnetic control valve for adjusting the gear ratio control valve, and a vehicle operating condition. And electronic control means for controlling the electromagnetic control valve based on the electronic control means. When the vehicle speed is less than or equal to a predetermined vehicle speed, the electromagnetic control valve drive signal is corrected so that the detected value from the hydraulic pressure detecting means becomes a preset target. apparatus.