JPS62268745A - Departure clutch control method for automatic transmission - Google Patents

Abstract

PURPOSE:To prevent an engine stop by detecting the change rate by time of the vehicle speed or the engine rotating speed at the time of quick deceleration and controlling a departure clutch from a completely engaged state to a sliding state or a disengaged state if this change rate is an allowable value or more. CONSTITUTION:A continuously variable transmission 10 is constituted of a driving side pulley 12 provided on a drive shaft 11, a driven side pulley 14 provided on a driven shaft 13, and a V-belt 15 provided between them. A hollow shaft 19 is rotatably supported around the driven shaft 13, and they are engaged or disengaged by a departure clutch 20. The oil pressure in a hydraulic chamber 18 for controlling the transmission gear ratio and the departure clutch 20 is controlled by an oil pressure control device. In this case, the change rate by time of the vehicle speed or the rotating speed of an engine 1 at the time of quick deceleration is detected, and if this change rate is an allowable value or more, the departure clutch 20 is controlled from a completely engaged stage to a sliding state or a disengaged state.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for controlling a starting clutch of an automatic transmission, and more particularly to a method for controlling a slip type starting clutch that can arbitrarily control transmission torque.

Conventional technology and its problems Traditionally, automatic clutches such as fluid couplings and centrifugal clutches have been widely used as starting clutches in automatic transmissions, but fluid couplings have large transmission losses during normal driving.
Furthermore, in the case of a centrifugal clutch, the transmission torque characteristics depend only on the engine speed, so a complete neutral state cannot be obtained.

Therefore, by using a slipping clutch such as an electromagnetic powder clutch or a wet multi-disc clutch and electronically controlling the transmission torque, it is possible to achieve smooth starting performance similar to an automatic clutch, reduce transmission loss, and further increase the degree of freedom in control. A system has been proposed that achieves expansion.

By the way, in the case of fluid clutches, there is a slipping phenomenon.
Also, in the case of a centrifugal clutch, it is automatically disconnected as the engine speed decreases, so there is no risk of the engine stalling even if sudden braking is applied. However, in the case of electromagnetic powder clutches and wet multi-disc clutches, it is necessary to detect sudden braking using some kind of signal and control the starting clutch to disconnect.One way to do this is to detect when the engine speed is below a set value. One possible method is to control the engine so that it shuts off when the vehicle descends to a low speed, but if the above setting value is set to a low value near the idling speed, even if stalling can be avoided during gentle braking, the starting clutch will disengage during sudden braking. lags behind the drop in engine speed, which can easily cause the engine to stall.Especially, when braking suddenly while driving on a snowy road, the wheels tend to slip. It is almost impossible to return to the cut-off state. on the other hand,
If the set value is set high, it is possible to avoid engine stalling during sudden braking, but since the starting clutch is disengaged at a relatively high engine speed during gentle braking, the engine brake cannot be sufficiently applied. Also, when accelerating again, there is a shock when the starting clutch engages.

OBJECTS OF THE INVENTION The present invention has been made in view of the above problems, and its purpose is to provide a starting clutch control method for an automatic transmission that can prevent engine stalling during sudden deceleration and that does not cause problems even during slow deceleration. It's about doing.

Structure of the Invention In order to achieve the above object, the present invention detects the time rate of change in vehicle speed or engine rotation speed during sudden deceleration in an automatic transmission equipped with a slip-type starting clutch that can arbitrarily control the transmitted torque. However, when the rate of change is greater than or equal to a permissible value, the starting clutch is controlled from fully engaged to either a slip state or a disengaged state.

In other words, if the starting clutch is controlled in the disengaged direction when the time rate of change of the vehicle speed or engine speed exceeds the allowable value, the starting clutch can be quickly disengaged no matter how sudden the deceleration is, and the engine stall can be prevented. can be avoided. Furthermore, since the above control operates only during sudden deceleration (regardless of braking or non-braking), it can be arbitrarily controlled during slow deceleration, taking into consideration engine braking performance, stress during re-acceleration, etc.

DESCRIPTION OF EMBODIMENTS FIG. 1 shows a V-belt continuously variable transmission which is an example of an automatic transmission according to the present invention, in which a crankshaft 2 of an engine 1 is connected to an input shaft 4 via a damper mechanism 3. . An external gear 8 is fixed to the end of the input shaft 4, and this external gear 8 meshes with an internal gear 9 fixed to the drive shaft 11 of the continuously variable transmission 10 to transfer the power of the input shaft 4. Reduce speed and drive shaft 1
1.

The continuously variable transmission 10 includes a drive pulley 1 provided on a drive shaft 11.
2, a driven pulley 14 provided on the driven shaft 13, and a V-belt 15 wound between both pulleys. The drive side pulley 12 has a fixed sheave 12a and a movable sheave 12b.
A torque cam device 16 and a compression spring 17 are provided behind the movable sheave 12b.

The torque cam device 16 generates a force proportional to the human torque, and the compression spring 17 generates an initial thrust sufficient to prevent the V-belt 15 from loosening, and these thrusts apply belt tension to the V-belt 15 necessary for torque transmission. are doing.

On the other hand, the driven pulley 14 also has a fixed sheave 14a and a movable sheave 14b like the drive pulley 14, and a hydraulic chamber 18 for speed ratio control is provided behind the movable sheave 14b. The hydraulic pressure to this hydraulic chamber 18 is controlled by a hydraulic control device which will be described later.

A hollow shaft 19 is rotatably supported on the outer periphery of the driven shaft 13, and the driven shaft 13 and the hollow shaft 19 are connected and connected by a starting clutch 20 consisting of a wet multi-disc clutch, and this starting clutch 20 is controlled by hydraulic control, which will be described later. controlled by the device. A forward gear 21 and a reverse gear 22 are rotatably supported on the hollow shaft 19, and a forward/reverse switching sleeve 23
Either the forward gear 21 or the reverse gear 22 is connected to the hollow shaft 19 by l &
A reverse idler gear 25 that meshes with the reverse gear 22 and another reverse idler gear 26 are fixed to the advance idler shaft 24. A counter gear 28 and a final reduction gear 29 that simultaneously mesh with the forward gear 21 and the reverse idler gear 26 are fixed to the counter shaft 27.
The final reduction gear 29 meshes with the ring gear 31 of the differential mounting surface 30 and transmits power to the output shaft 32.

FIG. 2 shows a hydraulic control device for controlling the hydraulic pressure of the hydraulic chamber 18 and the starting clutch 20, where 40 is a solenoid pulp for speed change control, 50 is a solenoid pulp for starting control, and 60
is a control circuit such as a microcomputer.

The solenoid valve 40 for speed change control has the structure shown in FIG.
An output port 43 for outputting rr and a drain boat 44 are formed. The central valve chamber 45 has an input port 4.
A magnetic ball 46 that selectively opens and closes the input port 42 and the drain port 44 is housed in a movable manner. , the ball 46 moves rightward in FIG. 3 to open the input port 42 and close the drain port 44.

The solenoid valve 50 for start control has the same structure as the solenoid valve 40 for speed change control, and the reference numerals corresponding to those in FIG. 3 are also used. That is, 51 is a valve body, 52 is an input port leading to the hydraulic pressure source, 53 is an output port leading to the starting clutch 20, 54 is a drain port, 55 is a valve chamber, 56 is a ball, 57 is a spring, and 58
is a coil.

The control circuit 60 receives signals such as engine speed, output speed of the output shaft 32 (or vehicle speed), throttle opening θ, brake signal, and position switch signal from a sensor (not shown), and controls the solenoid according to the operating state. valve 4
The duty is controlled to 0.50.

Now, if the duty ratio of the control signal output from the control circuit 60 to the solenoid pulp 40.50 is D, the output oil pressure P of the solenoid pulp 40.50 is P = PL
-D, and since PL (line pressure) is a constant value, the output oil pressure PlIIT is controlled only by the duty ratio. Therefore, the gear ratio of the continuously variable transmission 10 and the transmission torque of the starting clutch 20 can be freely controlled by the duty ratio output from the control circuit 60 to the solenoid pulps 40 and 50. Note that the duty ratio of each solenoid pulp 40, 50 in the operating state is stored in the control circuit 60 as, for example, a data map.

FIG. 4 shows a shift diagram of the V-belt type continuously variable transmission.

In the drawing, first, when starting, the engagement force of the starting clutch 20 is increased from point A, which is slightly higher than the idle speed,
When point B is reached, the starting clutch 20 is maintained in a fully engaged state and the starting control is shifted to shift control. In shift control, the engine speed first accelerates along the straight line of the lowest speed ratio, and when the engine speed reaches the target engine speed N, which corresponds to the throttle opening at that time (0 point), it shifts to the speed change region and the target engine speed changes. Shift to the high speed ratio side while maintaining the number N6. After the speed ratio reaches the maximum speed ratio (point D), the hydraulic pressure in the hydraulic chamber 18 is drained, and the continuously variable transmission 10 continues to travel while being maintained at the maximum speed ratio.

FIG. 5 shows the transmission torque characteristics of the starting clutch 20, which, like a fluid coupling and a centrifugal clutch, has a characteristic that is approximately proportional to the square of the engine rotation speed, so that smooth starting performance can be obtained. In addition, in a low rotation range near the idle rotation speed N1, low oil pressure is introduced so that the starting clutch 20 generates a low transmission torque T1 for the purpose of improving responsiveness when starting and preventing shock when the clutch is engaged. , adjusted to produce a creep phenomenon. Note that in the neutral range (P, N range), no hydraulic pressure is introduced to the starting clutch 20, and the starting clutch 20 is in a completely disconnected state.

By the way, in the V-belt continuously variable transmission with the above configuration,
When slow deceleration is performed while traveling in the maximum speed ratio state, the speed is decelerated along the straight line of the maximum speed ratio, and the engine speed is set to a predetermined value N that is slightly higher than the idle speed N. , the duty ratio of the solenoid valve 40 for speed ratio control is increased to shift to a lower speed ratio side, and the duty ratio of the solenoid valve 50 for start control is decreased, and the start clutch 20 is moved from the fully engaged state. Just return it to creep state. However, if the brakes are applied suddenly while driving on a snowy road, the wheels are likely to lock, and in such a case, the engine speed drops rapidly, so the engine speed is kept at the predetermined value N. If the disengagement of the starting clutch 20 is started only when the condition is below, it is already too late and engine stall cannot be avoided. Therefore, in the present invention, the time rate of change in engine speed or vehicle speed is detected, and when the time rate of change exceeds an allowable value even instantaneously, the starting clutch 20 is returned to the creep state or disconnected state, and sudden deceleration occurs when the wheels are locked. This prevents the engine from stalling.

Next, an example of a method of controlling the starting clutch 20 according to the present invention will be explained with reference to FIG.

When the control starts, it is first determined whether or not the brake signal is ON (70).The brake signal may be detected by detecting pedal operation by, for example, a switch provided on the brake pedal, or by detecting a pedal operation by a switch provided on the brake pedal. Changes in the oil pressure supplied to the cylinder may be detected. If the brake signal is OFF, braking will not be performed.
After this control is completed, if it is ON, the time change rate of the engine speed (ΔN/Δt) is calculated from the current value N of the engine speed and the minute time Δ from the previous value N° using the following formula (
71).

ΔN IN-N'1 Δt Δ, then set the above time rate of change to the allowable value A (for example, 11000 r
p/5ec)72), if ΔN/Δt≧A, it is determined that sudden braking is in progress, and the start control solenoid valve 50
(73), while the duty ratio of ΔN/ If Δt<A, it is determined that slow braking is in progress, and then the current engine speed N and the predetermined value N0 are determined.
(74), this value NG may be set to a value slightly higher than the idle rotation speed. If N≦No, it means that the starting clutch 20 should be disconnected, so similarly to (73), the transmission torque of the starting clutch 20 is reduced to the creep state, and if N>No, the starting clutch 20 is in a state where it should be disconnected. The control is completed by maintaining the fully engaged state.

Other Embodiments In the above control, it is determined whether the brake signal is ON or OFF in (71), but this is for accurately determining the braking state. If the control of the present invention is to be executed even when sudden deceleration is performed without operating the brakes, such as when the vehicle is about to approach the vehicle, it is not necessary to determine the brake signal.

In addition, in the above control, the time rate of change of the engine speed was compared with the allowable value, but the vehicle speed may be used instead of the engine speed. In particular, when the wheels are locked while driving on a snowy road, the vehicle speed (output speed ) has a rapid rate of change over time, so the range of allowable values for discrimination is wide.

In the hydraulic control device of the above embodiment, an example was shown in which the gear ratio of the continuously variable transmission 10 and the transmission torque of the starting clutch 20 are each controlled by the solenoid valves 40 and 50 alone.
The control is not limited to this, but may be controlled by a combination of a solenoid valve and a spool valve, for example.

In this case, the solenoid valve is not limited to the type in which the input port and the drain port are selectively opened and closed using a ball-shaped valve body, and a needle type solenoid valve may be used.

Although the starting clutch 20 is provided in the output shaft system of the continuously variable transmission 10 in the above embodiment, it may be provided in the input shaft system as in a normal transmission. However, when configured as in the embodiment, the following effects can be expected. In other words, when a sudden deceleration is performed while driving at the highest speed ratio, the starting clutch 20 is activated as described above.
If the engagement is released too early, the continuously variable transmission 10 may not return to a low speed ratio at which it can restart the vehicle until the vehicle stops. However, the starting clutch 20 is connected to the continuously variable transmission 10.
Since the continuously variable transmission lO is provided on the output shaft system of the engine 1, even when the vehicle is stopped, the continuously variable transmission lO is idled by the engine 1, and in this state, by applying hydraulic pressure to the hydraulic chamber 18, it is possible to easily return to a low speed ratio. Therefore, forced start from a high speed ratio state can be avoided. This effect is particularly important when a high friction coefficient material such as rubber or resin is used for the contact surface between the belt 15 and the boot.

Further, as the starting clutch 20, an electromagnetic powder clutch can be used instead of a wet multi-disc clutch, and in this case, the transmission torque can be directly controlled by an electric signal, so the configuration can be simplified.

Further, the automatic transmission of the present invention is not limited to continuously variable transmissions such as a V-belt type continuously variable transmission or a toroidal type continuously variable transmission, but also a general idle gear type automatic transmission can be used.

Effects of the Invention As is clear from the above explanation, according to the present invention, when the time rate of change in vehicle speed or engine speed exceeds a permissible value,
Since the starting clutch is controlled in the disengaging direction, the starting clutch can be quickly disengaged even if rapid deceleration occurs, such as when the wheels are locked, and engine stall can be avoided. Furthermore, since the above control operates only during sudden deceleration, it can be controlled arbitrarily in consideration of engine braking performance, shock during re-acceleration, etc. during slow deceleration, and does not interfere with control during slow deceleration.

[Brief explanation of the drawing]

Figure 1 is a skeleton diagram of an example of a belt-type continuously variable transmission to which the present invention can be applied, Figure 2 is a circuit diagram of a hydraulic control device, Figure 3 is a structural diagram of a solenoid pulp, and Figure 4 is a shift line. figure,
FIG. 5 is a transmission torque characteristic diagram of the starting clutch, and FIG. 6 is a flowchart of an example of a starting clutch control method. DESCRIPTION OF SYMBOLS 1... Engine, 4... Input shaft, 10... Continuously variable transmission surface, 15... V-belt, 18... Hydraulic chamber, 20
...Starting clutch, 32...Output shaft 1.50...
Solenoid pulp for starting control, 60...control circuit. Applicant Daihatsu Motor Co., Ltd. Agent Patent Attorney Hidetaka Tsutsui Figure 1 Umbrella L

Claims (1)

[Claims] (1) In an automatic transmission equipped with a slip-type starting clutch that can arbitrarily control the transmitted torque, the time rate of change in vehicle speed or engine speed during sudden deceleration is detected, and when the rate of change is greater than a permissible value, 1. A starting clutch control method for an automatic transmission, comprising controlling a starting clutch from a fully engaged state to a slipping state or a disengaged state.