JPH0198748A - Control device for continuously variable transmission - Google Patents

Abstract

PURPOSE:To prevent a vehicle from moving backward by providing a shift position sensor, a rotating direction deciding portion and a portion for deciding backward movement of a vehicle, and increasing line pressure to be compensated in case of deciding that the vehicle moves backward. CONSTITUTION:Line pressure of a continuously variable transmission 4 is controlled to be minimum at the time of stopping a vehicle to reduce the clamping force of a belt 16. At this time, when the vehicle moves backward in spite of a forward shift position, the backward movement is judged by a rotating direction deciding portion and a portion for deciding backward movement of the vehicle, and the line pressure is controlled to be increased. Then, the friction of the belt 16 and pulley system is increased, and the rotation of the pulley, that is, backward movement of the vehicle is locked to be prevented by the belt 16. Thus, the backward movement of the vehicle is reliably prevented by controlling the line pressure in the continuously variable transmission 4.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a control device for a belt-type continuously variable transmission for a vehicle, and more particularly to prevention of backward movement when the vehicle is stopped.

[Conventional technology]

In this type of belt-type continuously variable transmission, a belt is wrapped between the primary and secondary pulleys, and line pressure is applied to the cylinder of the secondary pulley, and line pressure is applied to the cylinder of the primary pulley to supply and drain oil. The gear shift is controlled by generating a predetermined primary pressure. Here, the belt is made up of a large number of elements stacked in a ring shape and wrapped around the ring, and when the pulley is pressed by line pressure, the force between the element and the ring is I:! The structure is such that belt tension is applied while generating vibration force, and power is transmitted by pressing elements together. On the other hand, there is a tendency for the shift control and line pressure control by varying the primary pressure to be electronically controlled with the aim of optimizing fi. In particular, line pressure control is controlled to the minimum level necessary to prevent belt slip, taking into consideration fuel efficiency due to pump loss, belt durability, and the like. Therefore, when the vehicle is stopped in an idling state, no power is being transmitted, so the line pressure is at its lowest. By the way, as the line pressure decreases, the pulley pressing force also decreases, so the frictional force between the element and the ring in the belt decreases, resulting in a state where relative slippage between the ring and the element is likely to occur. For this reason, even if the road surface has a gentle slope, when the clutch is not engaged, the vehicle cannot be stopped due to the friction of the pulley and belt system, causing the vehicle to idle and move backwards. Therefore, in controlling the line pressure to the minimum, it is necessary to take measures to prevent such backward movement. Conventionally, there is a prior art technique, for example, disclosed in Japanese Patent Laid-Open No. 60-40865, regarding prevention of backward movement of a vehicle equipped with a continuously variable transmission. Here, it is shown that backward movement on an uphill slope is automatically corrected using a gear element, a torque limiter, and a one-way clutch in the forward/reverse switching section.

[Problems to be solved by the invention]

By the way, the above-mentioned prior art assumes that there is no slip in the continuously variable transmission. Therefore, the belt due to the decrease in belt clamping force in the continuously variable transmission itself,
There is a problem that cannot be prevented if the vehicle moves backward due to reduced friction in the pulley system. In view of these points, it is an object of the present invention to provide a control system for a continuously variable transmission that prevents the vehicle from moving backward in a control system in which the line pressure is controlled to the minimum level when the vehicle is stopped.

[Means to solve the problem]

To achieve the above object, the present invention provides engine torque,
The line pressure is adjusted according to the transmission torque by the gear ratio element.
．． In the control system of continuously variable transmission, which controls to the minimum necessary level,
It has a shift position sensor that detects the forward/reverse shift position, a rotation direction determination section that detects the rotation direction of the pulley, and a vehicle backwardness determination section that determines whether the vehicle is backward based on the fact that the pulley rotates in the opposite direction to the shift position. , when it is determined that the vehicle is moving backwards, the line pressure is increased and corrected.

[For production]

Based on the above configuration, the line pressure of the continuously variable transmission is controlled to the lowest level when the vehicle is stopped to reduce the belt clamping force. At this time, for example, if the vehicle moves backward despite the forward shift position, the rotational direction and Each backward determination section determines this and controls the line pressure to increase. So, the belt. The pulley system's 7 traction is increased, and this belt locks the pulley to prevent it from rotating, that is, preventing the vehicle from rolling backwards. Thus, in the present invention, it is possible to reliably prevent the vehicle from moving backwards in the continuously variable transmission by controlling the line pressure.

【Example】

Embodiments of the present invention will be described below based on the drawings. Referring to FIG. 1, the overall configuration of a drive system that combines an electromagnetic clutch and a belt-type continuously variable transmission will be described. The engine 1 is connected to a continuously variable transmission I 14 via an electromagnetic clutch 29 such as an electromagnetic powder 2, a forward/reverse switching device 3, and a set of transmission gears 5 and 5 from the continuously variable transmission 4. Output shaft 6. The transmission is configured to be transmitted to drive wheels 9 via a differential gear 7 and an axle 8. The electromagnetic powder type clutch 2 has a drive member 2a provided at an engine crankshaft 1°, and a driven member 2b provided with a clutch coil 2C at an input @11. The clutch T4m flowing through the clutch coil 2C causes both members 2a to
, 1 in the gap between 2b! Magnetic particles are combined and accumulated in a chain, and the resulting binding force variably controls clutch engagement/disengagement and clutch torque. The forward/reverse switching device 3 is configured in a synchronous mesh type with gears, hubs, and sleeves between the input shaft 11 and the transmission main shaft 12, and has at least a forward position where the input shaft 11 is directly connected to the main shaft 12, and an input position. It has a retreat position where the rotation of the shaft 11 is reversed and transmitted to the main shaft 12. The continuously variable transmission 4 has a main shaft 12 and a sub-shaft 13 arranged parallel to the main shaft 12. The main shaft 12 has a primary pulley 14 with variable pulley spacing and a hydraulic cylinder 14a.
Similarly, the hydraulic cylinder 15a! - A secondary pulley 15 is provided. Further, a drive belt 16 is wound around both pulleys 14 and 15, and both cylinders 14a,
ISa is configured in a hydraulic control circuit 17. Line pressure corresponding to the transmitted torque is supplied to both cylinders 14a and 15a to apply a pulley pressing force, and the primary pressure causes the drive belt 16 to wrap around the pulley 14.15 steplessly by changing the diameter ratio. It is configured to perform speed change control. Next, the electronic control system of the electromagnetic powder clutch 2 and the continuously variable transmission 4 will be explained. Engine speed sensor 19 for engine 1. Primary pulley rotation speed sensor 21 of continuously variable transmission 4. Secondary pulley rotation speed sensor 22. It has sensors 23 and 24 that detect the operating status of the air conditioner and choke. The shift lever 25 of the operation system is mechanically connected to the forward/reverse switching device 3, and has a shift position sensor 26 that detects each range of reverse (R), drive (D), and sporty drive (Ds). have Further, the accelerator pedal 27 has an accelerator switch 28 for detecting the accelerator depression state, and a throttle opening sensor 29 for opening the throttle valve. The various signals from the switches and sensors are input to the electronic control unit 20 and processed by software using a microcomputer or the like. Then, the clutch control signal output from the electronic control unit 20 is input to the electromagnetic clutch 2, and the shift control signal and line pressure control signal are input to the hydraulic control circuit 17 of the continuously variable transmission 4 to perform each control operation. There is. Referring to FIG. 2, the electromagnetic clutch control system and continuously variable speed control system of the control unit 20 will be explained. First, the electromagnetic clutch control system includes a reverse excitation mode determination section 32 to which the engine speed Ne and signals of parking (P) and neutral (N) ranges other than R, D, and DS of the shift position sensor 26 are input. , for example Ne <3
In the case of 00 rpm or in the parking P or N range, the reverse excitation mode is determined, and the output determination unit 33 causes a small current in the opposite direction to the normal flow to flow, and the residual magnetism of the electromagnetic clutch 2 is removed and the electromagnetic clutch 2 is completely released. . Further, the determination output signal of this reverse excitation mode determination section 32, the accelerator switch 28
stepping signal and secondary pulley rotation speed sensor 22
It has an energization mode determination unit 34 to which a vehicle speed ■ signal is input,
The running state such as starting is determined, and this discrimination signal is sent to the starting mode current setting section 35. Drag mode current setting section 36. The current is input to the direct connection mode current setting section 37. The starting mode current setting unit 35 separately sets starting characteristics in relation to the engine rotation speed Ne, etc. in the case of normal starting or starting using an air conditioner or a choke. Then, throttle opening θ and vehicle speed ■. The clutch current is set by correcting the starting characteristics according to each driving range of R, D, and DS. The drag mode current setting unit 36 determines a slight drag current in each of the R, D, and Ds ranges when the accelerator is released at low vehicle speed, and generates drag torque in the electromagnetic clutch 2 to reduce play in the belt and drive system. In this mode, the current is set to zero until just before the vehicle stops after the clutch is released in the D range, ensuring coasting performance. The direct-coupling mode current setting unit 37 determines the direct-coupling current based on the relationship between the vehicle speed ■ and the throttle opening θ in each of the R, D, and DS ranges, fully engages the electromagnetic clutch 2, and saves power in the engaged state. The output signals of these current setting units 35, 36, and 37 are input to the output determining unit 33, and the clutch current is determined according to the instructions thereof. Next, to describe the speed change control system of the continuously variable speed control, the primary rotation speed Nl) and the secondary rotation speed Ns of the primary pulley rotation speed sensor 21° and the secondary pulley rotation speed sensor 22 are input to the actual speed ratio calculation unit 40, The actual speed ratio l is calculated from the actual speed ratio 1=Np/NS. The actual gear ratio l and the throttle opening θ of the throttle opening sensor 29 are input to the target primary rotation speed search unit 41, and R,
The target primary rotation speed NPD is searched for each range of D and DS using a 1-θ map based on the shift pattern. The target primary rotation speed NPD and the secondary rotation speed NS are input to the target gear ratio calculation unit 42, and the target gear ratio is
= N Po / N S is calculated. This target gear ratio is is then input to the target gear ratio change rate calculating section 43, and a target gear ratio change rate dis/dt is calculated based on the amount of change in the target gear ratio is over a certain period of time. These actual gear ratio i, target gear ratio iS, and target gear ratio change speed dis
/dt and the coefficients 1 and 2 of the coefficient setting section 44 are input to the shift speed calculation section 45, and the shift speed di/dt is calculated as follows. di/dt = 1 (is −i) + 2 ・di
s/dt In the above equation, 1s-i is the control amount for the difference between the target and actual speed change ratio, and dis/dt is the delay correction element of the control system. The shift speed di/dt and the actual gear ratio 1 are input to the duty ratio search section 46. Here, since the duty ratio of the manipulated variable is set according to the relationship D = f (di/dt, i), the duty ratio is di/dt - i for upshifts and downshifts. Searched. And the value of the duty ratio of this operation amount is
The signal is outputted via the drive unit 47 to the solenoid valve 48 for speed change control of the hydraulic control circuit 17 . Next, the line pressure control system for continuously variable transmission control will be described. Engine speed sensor 19. Throttle opening sensor 2
The engine torque retrieval unit 50 receives the engine rotational speed Ne of 9 and the throttle opening θ, and calculates the engine torque T from the torque characteristic map of θ-Ne. The engine torque T and the signal of the actual gear ratio i from the actual gear ratio calculation unit 40 are as follows:
The target line pressure PL is input to the target line pressure setting unit 51 and is determined by the product of the required line pressure according to the engine torque and the actual gear ratio i.
Define d. On the other hand, since the maximum line pressure value changes as the pump discharge pressure changes depending on the engine speed, the maximum line pressure search unit 52 inputs the engine speed Ne and the actual gear ratio i in order to detect this fluctuation state. and N
15-t map to find the maximum line pressure P. Target line pressure PLd and maximum line n pressure P1. i is input to the reduced pressure value calculation section 53, and the line pressure [lP, R is calculated as the target line pressure PL-ratio to the maximum line pressure P. This is input to the duty ratio search section 54 and calculated as the line pressure PLR. Determine the duty ratio accordingly. The duty signal is configured to be outputted to the line pressure control solenoid valve 56 via the drive section 55. Therefore, in the control system, another primary pulley rotation speed sensor 60 is provided in the same way as the primary pulley rotation speed sensor 21 as a measure to prevent the vehicle from moving backward. These primary rotation speed sensors 21
, 60 have their gears set in advance with a predetermined phase difference t as shown in FIG. At t1 when the signal Np of the primary pulley rotation speed sensor 21 is input, the signal ND' of the primary pulley rotation speed sensor 60 moves forward as shown by the solid line in FIG. If the input has already been made, it is determined that the vehicle is moving backward. Judgment result of rotation direction judgment unit 61, shift position sensor 26
The shift position of the vehicle, as well as signals from the accelerator switch 28 and brake switch 62 are input to a vehicle backward displacement determining section 63. When the vehicle is stopped with the brake and accelerator released, the vehicle backing determination unit 63 detects whether the shift position matches the forward/backward motion determination 7, and determines whether the vehicle is moving backward if they do not match. On the other hand, the duty search unit 5 of the line pressure control system
4 has a duty ratio correction section 64 on the output side, and this duty ratio correction section 64 changes the duty ratio in response to the backward movement signal from the vehicle backward movement determination section 63 to increase and correct the line pressure. Next, the operation of the continuously variable transmission control device configured as described above will be explained. First, the power from engine 1 corresponding to the depression of the accelerator is '! 4-magnetic clutch 21 is input to the primary pulley 14 of the continuously variable transmission 4 via the forward/reverse switching device 3, and the drive belt 16. The power that has been changed by the secondary pulley 15 is output, and this is transmitted to the drive wheels 91111I, thereby driving the vehicle. During the above-mentioned driving, the target line pressure is set to be larger as the engine torque T is larger in the lower speed gear where the value of the actual gear ratio i is larger, and a duty signal corresponding to this is input to the solenoid valve 56 to generate the control pressure. By controlling the line pressure using the averaged pressure, the line pressure PL is increased. Then, as the shift to a high speed gear occurs, the gear ratio i becomes smaller, and as the engine torque T also becomes smaller, the line pressure PL is controlled to decrease by the same effect, and in this way, the transmission by the drive belt 16 is always A pulley push that corresponds to a torque exerts a force. The line pressure P is always supplied to the secondary cylinder i5a, and is supplied to the primary cylinder 14a by a speed change control valve (not shown) using the control pressure of the solenoid valve 48.
Shift speed is controlled by supplying and draining oil to and from the engine. Here, line pressure control when the vehicle is stopped will be described using the flowchart in FIG. 4 and the line pressure characteristic diagram in FIG. 5. First, when the brake switch 62 is turned on due to a brake operation, the determination by the vehicle trailing determination section 63 is canceled and normal control is performed. Also, when the accelerator switch 28 is turned on by pressing the accelerator, normal control is performed in the same way, and at the time of starting, the line pressure is adjusted between P1 and P1 in Fig. 5 according to the engine torque.
It becomes a predetermined value between b0. On the other hand, if both the brake and accelerator are released,
The vehicle backward determination section 63 enters a determination state based on the shift position of the shift position sensor 26 and the rotation direction of the rotation direction determination section 61. Therefore, when decelerating at the forward position, the constant portion 61 is normally controlled by determining the forward rotation direction for each rotation direction, and the line pressure is controlled along the curve L1 in FIG. 5. On the other hand, when the vehicle is stopped in the forward position, the engine torque is small due to engine idling, and therefore the line pressure is controlled to the lowest value of PLn in Fig. 5.
m! The belt 16 at 414 is in a state where the frictional force between the element and the ring has almost disappeared. Therefore, at this time, if the vehicle moves backward due to the slope of the road surface, etc., the rotation direction determination unit 61. The line pressure is determined by the vehicle backward displacement determining unit 63 and the duty ratio correcting unit 64 adjusts the line pressure to PL shown in FIG.
l, and is kept in this increased state by setting a flag. For this reason, in the continuously variable transmission 4, the pressing force is increased by the primary pulley 14 and the secondary pulley 15, and the belt 16 is tensed and the clamping force is strengthened, and the pulley and belt system friction generated by this belt clamping force is Locks to stop the vehicle from moving backwards as the pulley rotates. When the vehicle starts from the stop condition by pressing the accelerator, the flag is cleared and normal control is resumed. Further, the same effect occurs when decelerating in the reverse position or moving backward in the forward direction. Although one embodiment of the present invention has been described above, it is not limited thereto.

【Effect of the invention】

As described above, according to the present invention, when controlling the line pressure to the minimum necessary level in a continuously variable transmission, if the vehicle moves backward due to a decrease in belt clamping force when the vehicle is stopped, the belt clamps by increasing the line pressure. By increasing the force, it is possible to reliably prevent the person from moving backward. Since only the line pressure is increased and corrected, control is easy and there is little effect on fuel efficiency, etc.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an outline of an embodiment of the control device of the present invention, Fig. 2 is a block diagram of the electronic control system, Fig. 3 is a diagram showing determination of the rotation direction, and Fig. 4 is a flow chart of the operation. , Figure 5 is a characteristic diagram of line pressure. 4...Continuously variable transmission, 20...Control unit, 26.
...Shift position sensor, 56...Solenoid valve for line pressure control, 61...Rotation direction determination section, 63...Vehicle backward displacement determination section, 64...Duty ratio correction section Patent attorney Susumu Murai Figure 3 Figure 5 Earth-poor L

Claims (1)

[Scope of Claims] A shift position sensor that detects the forward/reverse shift position in a control system of a continuously variable transmission that controls line pressure to the minimum necessary level according to transmission torque based on factors such as engine torque and gear ratio. , a rotation direction determination unit that detects the rotation direction of the pulley, and a vehicle backwardness determination unit that determines whether the vehicle is moving backward based on the fact that the pulley rotates in the opposite direction to the shift position. A control device for a continuously variable transmission characterized by increasing and correcting pressure.