JP5295060B2 - Control device for automatic transmission for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of a continuously variable transmission for a vehicle at low cost, preventing a belt slip at a reverse start on the down grade. <P>SOLUTION: When a vehicle speed is smaller than or equal to a prescribed value and an accelerator opening is smaller than or equal to a prescribed value in a reverse range, closing control of a primary pulley oil chamber of the continuously variable transmission is executed. When the vehicle speed is smaller than or equal to the prescribed value, the accelerator opening is larger than the prescribed value, and moreover, a brake is OFF in the reverse range, clamping pressure increasing control for increasing the belt clamping pressure of the continuously variable transmission by a prescribed value in accordance with the accelerator opening, is executed. By executing such two-stage control, the belt slip at the reverse start is prevented. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

The present invention relates to a control device for a continuously variable transmission, and more particularly to measures against belt slippage during reverse climbing on a downhill.

Conventionally, vehicles equipped with continuously variable transmissions are known. In general, a continuously variable transmission obtains a target input rotational speed from the vehicle speed and the accelerator opening, controls the pulley ratio so that the actual input rotational speed approaches the target input rotational speed, and does not cause belt slip from the input torque. The target belt clamping pressure is determined, and the hydraulic pressure of the secondary pulley is controlled. On a downhill with a large gradient as shown in FIG. 6, when a vehicle equipped with a continuously variable transmission starts reverse climbing, climbing may start after the vehicle has slipped once.

FIG. 7 shows changes over time in belt clamping pressure, vehicle speed, vehicle position, accelerator signal, and brake signal during reverse climbing. When the brake is turned off at time t1, the vehicle begins to fall down, but in a vehicle equipped with a vehicle speed sensor that cannot detect the rotational direction, the vehicle speed appears as if the vehicle speed has increased. Next, when the accelerator is turned on at time t2, the target belt clamping pressure corresponding to the input torque (engine torque) is calculated. However, when the slippage occurs, the turbine reversely rotates in the torque converter. It cannot be reflected in the pressure. Therefore, the belt clamping pressure is insufficient with respect to the necessary belt clamping pressure, and belt slippage occurs. Eventually, the slippage disappears at time t3, the vehicle speed becomes zero, and reverse start is started. In the meantime, the vehicle slides down from the initial stop position by a distance L.

As described above, when starting up a reverse uphill, if the uphill is started after the vehicle has once lowered, belt slip may occur for the following reasons.
(1) Since the target belt clamping pressure is calculated in the same way as during normal reverse (turbine rotation in the torque converter) even when the vehicle slides down (turbine reverse rotation in the torque converter), the belt clamping pressure is insufficient. To do.
(2) When “sliding down” → “stop” → “reverse start” of the vehicle occurs, the rotation direction of the belt is reversed, and when the vehicle stops, the belt clamping pressure is insufficient and belt slippage occurs.
(3) When the vehicle slides down, the shift control for returning Low is activated, and the hydraulic pressure of the primary pulley is released at a stretch. Therefore, the volume of the oil chamber changes, the pinching pressure of the primary pulley decreases, and belt slip occurs.

Patent Documents 1 and 2 disclose that the belt slip prevention control is performed by determining the reverse rotation of the pulley of the continuously variable transmission. Patent Document 3 discloses a technique for detecting a road surface gradient and increasing the belt clamping pressure above a predetermined gradient. Furthermore, Patent Document 4 discloses a system that performs a closing control for maintaining the maximum gear ratio when starting after the vehicle stops.

In Patent Document 1, it is determined whether or not the secondary pulley is rotating in the reverse direction to the traveling direction selected by the shift lever, based on whether or not the balance between the primary pressure and the secondary pressure is lost. A hydraulic sensor that detects both secondary pressures is required. Further, in Patent Document 2, a turbine rotation sensor for determining the reverse rotation state of the torque converter is necessary, and in Patent Document 3, a road surface gradient sensor is necessary, and both result in an increase in cost. In Patent Document 4, even if the confinement control is performed at the time of starting, if the road surface gradient increases, the sliding down is unavoidable, and no countermeasure is disclosed in that case.

JP 2004-92539 A JP-A-2005-315302 JP 2003-343707 A JP 2008-8339 A

An object of the present invention is to provide a low-cost control device for a continuously variable transmission for a vehicle that can prevent belt slippage when reverse starting on a downhill.

In order to achieve the above object, the present invention detects that the reverse range of the forward / reverse switching device is selected in a vehicle that transmits the driving force of the engine to the wheels via the forward / reverse switching device and the continuously variable transmission. Range detecting means, speed ratio detecting means for detecting the gear ratio of the continuously variable transmission, accelerator opening detecting means for detecting the accelerator opening of the engine, brake detecting means for detecting depression of the brake, Vehicle speed detecting means that detects the vehicle speed and does not have a function of discriminating the rotational direction of the wheel, and the primary pulley oil of the continuously variable transmission when the vehicle speed is not more than a predetermined value and the accelerator opening is not more than a predetermined value in the reverse range. Means for controlling the closing of the chamber and the bell of the continuously variable transmission when the vehicle speed is below a predetermined value, the accelerator opening is larger than the predetermined value, and the brake is OFF in the reverse range. To provide a control device for a continuously variable transmission for a vehicle, characterized in that it comprises a means for performing the clamping increase control for increasing a predetermined value in accordance with clamping on the accelerator opening.

On a steep downhill slope, the vehicle may slide down in the reverse range until the foot is released from the brake pedal and switched to the accelerator pedal. Since the vehicle speed sensor does not have a function for discriminating the rotation direction of the wheels, when the vehicle slides down, it erroneously recognizes that the vehicle has started, and starts high-side shift, but recognizes that the vehicle is decelerating and stopped when returning from the downhill. Then, since the hydraulic pressure of the primary pulley oil chamber is released for returning low, there is a possibility that the belt slips. Therefore, when the vehicle speed is less than the predetermined value and the accelerator opening is less than the predetermined value, the primary pulley oil chamber is controlled to be closed so that the ratio between the primary pressure and the secondary pressure becomes a preset relationship. The secondary pressure is controlled at a predetermined speed ratio. Therefore, the primary pulley oil chamber does not change in volume, and belt slip can be suppressed.

On the other hand, in the reverse range, when the vehicle speed is equal to or less than a predetermined value, the accelerator opening is larger than the predetermined value, and the brake is OFF, the clamping pressure for increasing the belt clamping pressure of the continuously variable transmission by a predetermined value according to the accelerator opening Implement ascent control. Specifically, the hydraulic pressure of the secondary pulley is increased. The target belt clamping pressure is determined according to the input torque, but when the vehicle slips during reverse, the target belt clamping pressure determined based on the case where the torque converter is in the forward rotation state is insufficient, and the belt slip Can not prevent. Therefore, when the above condition is satisfied, it is determined that the vehicle is in reverse start, and the belt clamping pressure is corrected to increase by a predetermined value according to the accelerator opening. As a result, the belt clamping pressure increases from the normal time (at the time of torque converter positive rotation), and reverse uphill starting can be performed while suppressing belt slip.

In the present invention, by optimizing the predetermined values of the vehicle speed and the accelerator opening, the control method on the flat road and the slope road can be made common, and simple control becomes possible. As the predetermined value of the vehicle speed, it is possible to set the assumed maximum speed at which the vehicle slides down by the accelerator depressing operation after the brake is turned off by reverse start on the uphill road. In that case, two-stage control can be performed before returning to the reverse traveling state, and normal control can be promptly returned on a flat road without slipping down. The present invention does not perform hill hold control (control that keeps the brake fluid pressure for a predetermined time even when the foot is released from the brake pedal and prevents the vehicle from sliding down), the gradient sensor, the turbine speed sensor, the primary The present invention can be applied to a simple continuously variable transmission that does not have a pressure sensor or the like.

As described above, according to the present invention, during reverse climbing, when the vehicle speed is equal to or smaller than a predetermined value and the accelerator opening is equal to or smaller than a predetermined value in the reverse range, the control for closing the primary pulley oil chamber of the continuously variable transmission is performed. In the reverse range, when the vehicle speed is less than a predetermined value, the accelerator opening is larger than the predetermined value, and the brake is OFF, the belt clamping pressure of the continuously variable transmission is increased by a predetermined value according to the accelerator opening. Since the pressure increase control is performed, even when the vehicle starts to reverse-climb after the vehicle has slipped down, the belt slip can be reliably prevented and the durability of the belt can be improved.

It is a skeleton figure which shows the structure of the vehicle which concerns on this invention. FIG. 2 is a hydraulic circuit diagram of the continuously variable transmission shown in FIG. 1. It is a hydraulic circuit diagram of the principal part of FIG. It is a figure which shows each characteristic of line pressure P _{L with} respect to solenoid pressure Psls, clutch modulator pressure Pcm, clutch control pressure, and secondary pressure. It is a flowchart figure at the time of reverse climbing start which concerns on this invention. It is a figure of the vehicle at the time of reverse climbing start. It is a figure which shows each time change of the conventional belt clamping pressure at the time of reverse climbing start, a vehicle speed, a vehicle position, an accelerator signal, and a brake signal.

FIG. 1 shows an example of the configuration of a vehicle equipped with a continuously variable transmission according to the present invention. An output shaft 1 a of the engine 1 is connected to a drive shaft (output shaft) 32 via a continuously variable transmission 2. The continuously variable transmission 2 is provided with a torque converter 3, a transmission 4, a hydraulic control device 7, an oil pump 6 driven by the engine 1, and the like.

The continuously variable transmission 2 includes a forward / reverse switching device 8 that transmits the rotation of the turbine shaft 5 of the torque converter 3 to the primary shaft 10 by switching between forward and reverse, the primary pulley 11, the secondary pulley 21, and a V that is wound between the pulleys. The transmission 4 includes a belt 15, a differential device 30 that transmits the power of the secondary shaft 20 to the drive shaft 32, and the like. The turbine shaft 5 and the primary shaft 10 are arranged on the same axis, and the secondary shaft 20 and the drive shaft 32 are arranged parallel to the turbine shaft 5 and non-coaxially. Therefore, the continuously variable transmission 2 has a three-axis configuration as a whole. The V belt 15 used here is, for example, a known compression drive type metal belt composed of an endless tension band and a number of blocks slidably supported by the tension band.

The forward / reverse switching device 8 includes a planetary gear mechanism 80, a reverse brake B1, and a direct connection clutch C1, and the reverse brake B1 or the direct connection clutch C1 corresponds to the start clutch in the present invention. The reverse brake B1 and the direct coupling clutch C1 are wet multi-plate brakes and clutches, respectively. A sun gear 81 of the planetary gear mechanism 80 is connected to the turbine shaft 5 as an input member, and a ring gear 82 is connected to the primary shaft 10 as an output member. The planetary gear mechanism 80 is a single pinion system, the reverse brake B1 is provided between the carrier 84 supporting the pinion gear 83 and the transmission case, and the direct coupling clutch C1 is provided between the carrier 84 and the sun gear 81. When the direct clutch C1 is released and the reverse brake B1 is engaged, the rotation of the turbine shaft 5 is reversed and decelerated and transmitted to the primary shaft 10. Then, the drive shaft 32 rotates in the same direction as the engine rotation direction via the secondary shaft 20, so that the vehicle travels forward. On the contrary, when the reverse brake B1 is released and the direct clutch C1 is engaged, the carrier 84 and the sun gear 81 rotate together, so that the turbine shaft 5 and the primary shaft 10 are directly connected. Then, since the drive shaft 32 rotates in the direction opposite to the engine rotation direction via the secondary shaft 20, a reverse traveling state is set.

The primary pulley 11 of the transmission 4 includes a fixed sheave 11a that is integrally fixed on the primary shaft 10, and a movable sheave 11b that is supported on the primary shaft 10 so as to be axially movable and integrally rotatable. Yes. A cylinder 12 fixed to the primary shaft 10 is provided behind the movable sheave 11 b, and an oil chamber 13 is formed between the movable sheave 11 b and the cylinder 12. Shift control is performed by controlling the amount of oil supplied to the oil chamber 13.

The secondary pulley 21 includes a fixed sheave 21a that is integrally fixed on the secondary shaft 20, and a movable sheave 21b that is supported on the secondary shaft 20 so as to be axially movable and integrally rotatable. A piston 22 fixed to the secondary shaft 20 is provided behind the movable sheave 21 b, and an oil chamber 23 is formed between the movable sheave 21 b and the piston 22. By controlling the hydraulic pressure (secondary pressure) supplied to the oil chamber 23, a belt clamping pressure necessary for torque transmission is applied. The oil chamber 23 may be provided with a bias spring that applies an initial clamping pressure. In the supply oil passage in the vicinity of the oil chamber 23 of the secondary pulley 21, a hydraulic pressure sensor 108 that detects the secondary pressure is provided as will be described later.

One end portion of the secondary shaft 20 extends toward the engine side, and the output gear 27 is fixed to this end portion. The output gear 27 meshes with the ring gear 31 of the differential device 30, and power is transmitted from the differential device 30 to the drive shaft 32 extending left and right to drive the wheels.

The continuously variable transmission 2 is controlled by the electronic control unit 100. The electronic control unit 100 includes an engine speed sensor 101, a vehicle speed (or secondary pulley speed) sensor 102, a throttle opening (or accelerator opening) sensor 103, a shift position sensor 104, a primary pulley speed sensor 105, a brake signal. Signals are input from the sensor 106, the CVT hydraulic oil temperature sensor 107, and the hydraulic pressure sensor 108 that detects the secondary pressure. Other signals may be input as the input signal.

The electronic control device 100 controls a solenoid valve built in the hydraulic control device 7. The hydraulic control device 7 is connected to the oil pump 6, the oil chamber 13 of the primary pulley 11, the oil chamber 23 of the secondary pulley 21, the reverse brake B1, and the direct coupling clutch C1. The electronic control unit 100 determines the target primary rotational speed according to a shift map set in advance according to the vehicle speed and the throttle opening, and controls the solenoid valve in the hydraulic control unit 7 to thereby control the continuously variable transmission 2. The oil amount / hydraulic pressure of the oil chambers 13 and 23 of the primary pulley 11 and the secondary pulley 21 is adjusted to control the primary rotational speed to a target value and to control the belt clamping pressure to a value that does not cause belt slip. . The hydraulic control device 7 also has a function of controlling the hydraulic pressure supplied to the reverse brake B1 and the direct coupling clutch C1.

FIG. 2 is a hydraulic circuit diagram of an example of the hydraulic control device 7, and FIG. 3 is a hydraulic circuit diagram of the main part thereof. In FIG. 2, 71 is a regulator valve, 72 is a clutch modulator valve, 73 is a solenoid modulator valve, 74 is a garage shift valve, 75 is a manual valve, 76 is an upshift ratio control valve, 77 is a downshift ratio control valve, 78 is a ratio check valve and 79 is a clamping pressure control valve. The SLS is a linear solenoid valve that outputs a solenoid pressure Psls to control the pressure regulation of the line pressure, the transient control of the reverse brake B1 and the direct coupling clutch C1, and the pressure regulation control of the oil chamber 23 of the secondary pulley 21, DS1 An upshift solenoid valve that regulates and controls the upshift signal pressure Pds1, DS2 is a downshift solenoid valve that regulates and controls the downshift signal pressure Pds2. The solenoid valves DS1 and DS2 also have a function as a solenoid valve that generates a signal pressure for switching the garage shift valve 74 to the transient pressure side. In this embodiment, the linear solenoid valve SLS uses a normally open linear solenoid valve, and the solenoid valves DS1 and DS2 both use a normally closed duty solenoid valve.

Solenoid valves DS1 and DS2 are controlled as follows according to the running state.

There are the following three types of confinement control of the present invention. The first is vehicle speed = 0, maximum gear ratio, and closing control performed during idling to prevent belt slipping when returning to low (per stopper of the primary pulley) and when stopping. To be implemented. The second is the very low vehicle speed confinement control that is performed when the gear ratio does not return to the lowest level and the vehicle speed is less than or equal to the extremely low vehicle speed (2 to 4 km / h). Sometimes downshifting is done because the belt may slip. Thirdly, the closing control at the time of reverse start according to the present invention is performed when the vehicle speed and the accelerator opening are equal to or less than a predetermined threshold in consideration of the slip start at the time of reverse as described later. .

In FIG. 2, only the hydraulic circuit relating to the primary pulley 11, the secondary pulley 21, the reverse brake B1 and the direct coupling clutch C1 is shown. However, the hydraulic circuit of the lock-up clutch 3a built in the torque converter 3 is the same as that of the present invention. Omitted because there is no direct relationship.

The regulator valve 71 is a valve that regulates the discharge pressure of the oil pump 6 to a predetermined line pressure P _L, and regulates the line pressure P _L according to the solenoid pressure Psls input to the signal port 71a.

The clutch modulator valve 72 is a valve that outputs a clutch modulator pressure Pcm that is a source pressure of supply pressures (P _C1 , P _B1 ) to the direct coupling clutch C1 and the reverse brake B1. The line pressure P _L is input to the input port 72a, and the clutch modulator pressure Pcm is output from the output port 72b. The output pressure is fed back to the first signal port 72c so as to face the spring load. Therefore, the clutch modulator pressure Pcm is adjusted to a constant pressure corresponding to the spring load.

The solenoid modulator valve 73 is a valve that regulates the clutch modulator pressure Pcm and generates a constant solenoid modulator pressure Psm corresponding to the spring load. The solenoid modulator pressure Psm is the original pressure of the upshift solenoid valve DS1 and the downshift solenoid valve DS2, and is also supplied to the clamping pressure control valve 79.

The garage shift valve 74 is for switching the oil passage so that the supply pressure to the direct coupling clutch C1 and the reverse brake B1 can be transiently controlled when the shift lever is switched from N → D or N → R (at the time of garage shift). It is a switching valve. The right side of the center line in FIG. 2 is the transient state, and the left side is the holding state. A spool 74b urged in one direction by a spring 74a is provided, and signal ports 74c and 74d to which signal pressures Pds1 and Pds2 are input are formed so as to face the spring load. Since the solenoid valves DS1 and DS2 are both turned on during the garage shift, the signal pressures Pds1 and Pds2 inputted to the signal ports 74c and 74d are both turned on, and the spool 74b moves downward against the spring 74a and moves to the right side. It becomes a transient state. The solenoid pressure (transient pressure) Psls input to the port 74e is output from the output port 74f and supplied to the direct coupling clutch C1 or the reverse brake B1 via the manual valve 75. Therefore, engagement can be started gently while avoiding the engagement shock of the direct clutch C1 or the reverse brake B1 by the solenoid pressure Psls. When at least one of the signal pressures Pds1 and Pds2 is turned OFF, the left side is held, and the clutch modulator pressure (holding pressure) Pcm input to the port 74g is output from the output port 74f and is directly coupled via the manual valve 75. C1 or reverse brake B1 is supplied. Therefore, the engagement state of the direct clutch C1 or the reverse brake B1 can be maintained regardless of the operation of the linear solenoid valve SLS.

The manual valve 75 is a manually operated valve mechanically connected to the shift lever. The manual valve 75 is switched to each range of P, R, N, D, S, and B, and the hydraulic pressure supplied from the garage shift valve 74 is directly coupled to the clutch C1. Alternatively, it selectively leads to the reverse brake B1. The input port 75a is supplied with hydraulic pressure from the garage shift valve 74, the output port 75b is connected to the direct clutch C1, and the output ports 75c and 75d are both connected to the reverse brake B1. In the R range, the manual valve 75 supplies the hydraulic pressure to the direct clutch C1 and drains the hydraulic pressure of the reverse brake B1. In the D, S, and B ranges, the manual valve 75 supplies the hydraulic pressure to the reverse brake B1 and drains the hydraulic pressure of the direct clutch C1. . In the P and N ranges, which are non-traveling ranges, the hydraulic pressures of the direct clutch C1 and the reverse brake B1 are drained together.

The upshift ratio control valve 76 and the downshift ratio control valve 77 are supplied with and discharged into the oil chamber 12 of the primary pulley 11 by the relative relationship between the upshift signal pressure Pds1 and the downshift signal pressure Pds2. This is a flow control valve for adjusting the flow rate. That is, as shown in FIG. 3, the upshift ratio control valve 76 includes a spool 76b urged in one direction by a spring 76a, and a signal pressure Pds2 is applied to a signal port 76c on one end side where the spring 76a is accommodated. Is entered. The signal pressure Pds1 is input to the signal port 76d on the other end side facing the spring load. A line pressure P _L is supplied to the intermediate input port 76 e, and the output port 76 f is connected to the hydraulic oil chamber 12 of the primary pulley 11. A port 76h connected to a port 78h of a ratio check valve 78 described later is formed between the input port 76e and the drain port 76g, and a downshift ratio control is provided between the output port 76f and the signal port 76d. A port 76 i connected to the port 77 f of the valve 77 and the port 78 d of the ratio check valve 78 is formed.

The downshift ratio control valve 77 includes a spool 77b biased in one direction by a spring 77a, and a signal pressure Pds1 is input to a signal port 77c on one end side in which the spring 77a is accommodated. The signal pressure Pds2 is inputted to the signal port 77d on the other end side facing the spring load. In the intermediate portion, a drain port 77e, a port 77f connected to the port 76i of the upshift ratio control valve 76, and a port 77g connected to the port 78f of the ratio check valve 78 are formed in this order. Since the operation of the upshift ratio control valve 76 and the downshift ratio control valve 77 is known from, for example, Japanese Patent Application Laid-Open No. 2007-263207, the description thereof is omitted.

The ratio check valve 78 is a valve for maintaining the ratio between the primary pressure and the secondary pressure in a preset relationship by switching the oil chamber 12 of the primary pulley 11 from the flow rate control to the hydraulic control for closing control. It is. The ratio check valve 78 includes a spool 78b biased in one direction by a spring 78a, and the hydraulic pressure of the secondary pulley oil chamber 23 is input to a signal port 78c on one end side in which the spring 78a is accommodated. The oil pressure of the primary pulley oil chamber 12 is input to the signal port 78d on the other end side facing the spring load via the ports 76f and 76i of the upshift ratio control valve 76. Note that the pressure receiving area of the signal port 78d to which the primary pressure is input is larger by α times than the pressure receiving area of the signal port 78c to which the secondary pressure is input. The line pressure P _L is supplied to the input port 78e, and the output port 78f is connected to the port 77g of the downshift ratio control valve 77. Further, a port 78h connected to the port 76h of the upshift ratio control valve 76 is formed between the output port 78f and the drain port 78g.

During the closing control, both the solenoid valves DS1 and DS2 are turned OFF, and the signal pressures Pds1 and Pds2 are both zero. Therefore, the upshift ratio control valve 76 is in the right position in FIG. 3, and the downshift ratio control valve 77 is in the left position in FIG. When the sum of the load due to the secondary pressure and the spring load is relatively larger than α times the load due to the primary pressure, the ratio check valve 78 is in the left position in FIG. 3 and is connected to the input port 78e of the ratio check valve 78. The supplied line pressure P _L is supplied from the output port 78f through the ports 77g and 77f of the downshift ratio control valve 77 and the ports 76i and 76f of the upshift ratio control valve 76. Conversely, when the α times the load due to the primary pressure is relatively larger than the sum of the load due to the secondary pressure and the spring load, the ratio check valve 78 is switched to the right position in FIG. Therefore, the primary pressure is drained from the output port 78f and the port 78h via the ports 76h and 76g of the upshift ratio control valve 76. Actually, the spool 78b of the ratio check valve 78 is balanced at an intermediate position between a position connecting the output port 78f and the input port 78e and a position connecting the output port 78f and the port 78h. In this way, the ratio check valve 78 is controlled at the secondary pressure so that the ratio between the primary pressure and the secondary pressure has a predetermined relationship, and can be held at a predetermined gear ratio.

The clamping pressure control valve 79 is a valve for controlling the hydraulic pressure (secondary pressure) of the hydraulic oil chamber 23 of the secondary pulley 21. A spool 79g biased in one direction by a spring 79f is provided, and a constant pressure Psm is supplied from a solenoid modulator valve 73 to a signal port 79a on one end side facing the spring load. Line pressure P _L is supplied to the input port 79b, the output port 79c is connected to the hydraulic oil chamber 23 of the secondary pulley 21, and the secondary pressure is fed back to the port 79d. The solenoid pressure Psls is supplied to the signal port 79e on the other end side in which the spring 79f is accommodated. Port 79h is a drain port. Therefore, the hydraulic pressure obtained by amplifying the solenoid pressure Psls input to the signal port 79e with a predetermined amplification degree can be supplied to the hydraulic oil chamber 23 of the secondary pulley 21 as a secondary pressure. The hydraulic pressure (secondary pressure) in the hydraulic oil chamber 23 is detected by the hydraulic pressure sensor 108, and the belt clamping pressure or the belt transmission torque can be obtained based on the detected hydraulic pressure.

FIG. 4 shows the characteristics of the line pressure P _L , the clutch modulator pressure Pcm, the clutch control pressure, and the secondary pressure with respect to the solenoid pressure Psls. The line pressure P _L is adjusted to a hydraulic pressure substantially proportional to the solenoid pressure Psls. The clutch modulator pressure Pcm is the same as the line pressure P _L until the solenoid pressure Psls reaches a predetermined value, and is limited to a constant pressure when it exceeds the predetermined value. Further, since the solenoid pressure Psls is directly supplied to the reverse brake B1 or the direct coupling clutch C1 in a transient state, the clutch control pressure becomes the solenoid pressure Psls itself. The secondary pressure is proportional to the solenoid pressure Psls and is adjusted to a hydraulic pressure slightly lower than the line pressure P _L. As shown in FIG. 4, although both the clutch control pressure and the secondary pressure are controlled by the solenoid pressure Psls, the secondary pressure is always set to exceed the clutch control pressure. The secondary pressure is detected by the hydraulic pressure sensor 108.

Next, a method for controlling the continuously variable transmission according to the present invention will be described with reference to FIG. Here, at the time of reverse climbing (see FIG. 6), two-stage control (confining control and pinching-up control) for suppressing belt slip and improving the life of the belt is performed.

In FIG. 5, when the control starts, it is first determined whether or not the shift lever is in the reverse position (step S1). If the vehicle is in the reverse state, it is next determined whether or not all the conditions of vehicle speed ≦ 10 km / h, accelerator opening ≦ 5%, gear ratio ≦ 2.0 (maximum gear ratio = 2.23) are satisfied (step S2). ). This determination is control when the vehicle tries to slide down while the brake pedal is switched from the accelerator pedal, and the idle speed is corrected to be higher by a predetermined value and the idle is increased (step S3). When switching from the D range to reverse (R) quickly, the gear ratio may remain higher than the lowest, but if the condition of step S2 is satisfied, the engine speed will be increased by idling up. The engine torque is increased and the sliding down is suppressed.

When at least one of the conditions in step S2 is not satisfied, or while idling up, it is determined whether vehicle speed ≦ 4 km / h (step S4). When the vehicle speed> 4 km / h, it is determined that there is no concern about belt slip, and the subsequent control is not performed. When the vehicle speed ≦ 4 km / h, it is subsequently determined whether or not the accelerator opening degree ≦ 2% (step S5). If the vehicle speed ≤ 4 km / h and the accelerator opening ≤ 2%, the vehicle is almost stopped and the accelerator pedal is not depressed, and the hydraulic pressure of the primary pulley 11 is set in the hydraulic circuit. The confinement control to be confined in is performed (step S6). In the closing control, both solenoid valves DS1 and DS2 are turned OFF as described above. As a result, the situation in which the hydraulic pressure of the primary pulley 11 is released can be eliminated, and belt slippage can be prevented.

On the other hand, if the vehicle speed ≦ 4 km / h and the accelerator opening degree> 2%, it is subsequently determined whether or not the brake is OFF (step S7). If the brake is on, there is no concern of belt slipping, so the following control is not performed. If the brake is OFF, it is determined that the vehicle has started in reverse, and the belt clamping pressure is corrected to increase by a predetermined value according to the accelerator opening (step S8). The target belt clamping pressure is set according to the input torque (engine torque) in the forward rotation state of the torque converter, but the accurate input torque should be reflected in the reverse rotation state of the torque converter, such as when the vehicle slips. Belt slippage may occur due to insufficient belt clamping pressure. Therefore, at the time of reverse starting, the belt clamping pressure is corrected to a value increased by a predetermined value in accordance with the accelerator opening, compared to the target belt clamping pressure during normal running. As a result, the belt clamping pressure increases and belt slip can be suppressed. The belt clamping pressure can be freely controlled by the solenoid pressure Psls of the linear solenoid valve SLS that regulates the secondary pressure. Since the secondary pressure can be detected by the hydraulic sensor 108, feedback control can be accurately performed on the target belt clamping pressure.

DESCRIPTION OF SYMBOLS 1 Engine 2 Continuously variable transmission 4 Continuously variable transmission 6 Oil pump 7 Hydraulic control apparatus 11 Primary pulley 21 Secondary pulley 71 Regulator valve 72 Clutch modulator valve 73 Solenoid modulator valve 74 Garage shift valve 75 Manual valve 76 Ratio control valve for upshift 77 Downshift ratio control valve 78 Ratio check valve 79 Nipping pressure control valve 80 Planetary gear mechanism 100 Electronic control device 101 Engine speed sensor 102 Vehicle speed sensor 103 Throttle opening sensor 104 Shift position sensor 105 Primary pulley speed sensor 106 Brake sensor 108 Hydraulic sensor B1 Reverse brake (start clutch)
C1 Direct clutch SLS Linear solenoid valve DS1 Upshift solenoid valve DS2 Downshift solenoid valve Psls Solenoid pressure Pds1, Pds2 Signal pressure

Claims (2)

In a vehicle that transmits engine driving force to wheels via a forward / reverse switching device and a continuously variable transmission,
Range detecting means for detecting that the reverse range of the forward / reverse switching device is selected;
Gear ratio detecting means for detecting a gear ratio of the continuously variable transmission;
Accelerator opening detecting means for detecting the accelerator opening of the engine;
Brake detecting means for detecting depression of the brake;
Vehicle speed detecting means for detecting the vehicle speed and having no function of discriminating the rotational direction of the wheels;
Means for controlling the closing of the primary pulley oil chamber of the continuously variable transmission when the vehicle speed is equal to or less than a predetermined value and the accelerator opening is equal to or less than a predetermined value in the reverse range;
In the reverse range, when the vehicle speed is less than a predetermined value, the accelerator opening is larger than the predetermined value, and the brake is OFF, the belt clamping pressure of the continuously variable transmission is increased by a predetermined value according to the accelerator opening. And a control device for a continuously variable transmission for a vehicle. 2. The vehicle according to claim 1, further comprising means for detecting a gear ratio in the closed control state and increasing engine torque when the gear ratio is smaller than a maximum gear ratio. Control device for continuously variable transmission.

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