JPS62268744A - Departure clutch control method for automatic transmission - Google Patents

Abstract

PURPOSE:To suppress the decrease of the engine rotating speed at the time of transfer to the drive range and prevent an engine stop by controlling so that the transmitted torque of a departure clutch in a creep state is reduced as the engine rotating speed is decreased. 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 suspended across them. A hollow shaft 19 is rotatably sheathed 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, the departure clutch 20, and a directly coupled clutch 5 is controlled by an oil pressure control device. In this case, the transmitted torque is controlled so as to be reduced concurrently when the rotating speed of an engine 1 starts to be decreased from the initial idle rotating speed at the time of transfer from the neutral range to the drive range.

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 an electromagnetic powder clutch or a wet multi-disc clutch and electronically controlling the transmission torque, we are able to achieve smooth starting performance similar to an automatic clutch, reduce transmission loss, and further expand the degree of freedom in control. A similar method has also been proposed.

By the way, when an electromagnetic powder clutch or a wet multi-disc clutch such as the one mentioned above is used as a starting clutch, in order to improve the responsiveness during starting and reduce the shock when the clutch is engaged, it is necessary to It is thought that it can cause a leap (drag) phenomenon. In this case, if the transmitted torque during creep is set to be almost constant regardless of the engine speed, the engine speed will inevitably drop when switching from the neutral range to the drive range, and in the worst case, there is a risk of engine stalling. .

OBJECTS OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a starting clutch control method for an automatic transmission that can suppress a drop in engine speed during creep.

Structure of the Invention In order to achieve the above-mentioned object, the present invention provides an automatic transmission equipped with a slip-type starting clutch capable of arbitrarily controlling transmission torque, and in which the starting clutch generates a creep state during idling. This is to control the transmission torque of the starting clutch in the creep state so that it gradually decreases as the engine speed decreases.

In other words, when the engine speed starts to drop from the initial idle speed due to switching from the neutral range to the drive range, the transmitted torque is controlled to decrease as the engine speed falls, so the engine speed decreases. There is little descent (and stalling can be reliably prevented.

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. . A wet type direct coupling clutch 5 and a freely rotatable direct coupling drive gear 7 are provided on the input shaft 4, and the direct coupling clutch 5 is controlled by a hydraulic control device, which will be described later, to connect the direct coupling drive gear 7 to the input shaft 4 during direct coupling drive. It has become.

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. The speed is decelerated and transmitted to the drive shaft 11.

The continuously variable transmission 10 is composed of a driving side boot 2 provided on a drive shaft 11, a driven pulley 14 provided on a driven shaft 13, and a V-belt 15 wound between both the boots. The drive 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 thrust proportional to the input torque, and the compression spring 17 generates an initial thrust sufficient to prevent the V-belt 15 from loosening.
5 is given the belt tension necessary for torque transmission. On the other hand, similarly to the driving pulley 12, the driven pulley 14 has a fixed sheave 14a and a movable sheave 14b, 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 the hydraulic control device described below.

A hollow shaft 19 is rotatably fitted around 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. The starting clutch 20 also serves as a power intermittent clutch, and is engaged by a hydraulic control device to be described later during belt drive (continuously variable speed drive), disconnected during direct drive, and duty-controlled during start. The hollow shaft 19 has a forward gear 2.
1 and a reverse gear 22 are rotatably supported, and either the forward gear 21 or the reverse gear 22 is connected to the hollow shaft 19 by a forward/reverse switching sleeve 23. The idler shaft 24 for reverse movement is the driven shaft 13
This shaft 24 has a reverse gear 2.
A reverse idler gear 25 meshing with the reverse idler gear 26 and another reverse idler gear 26 are fixed. A counter shaft 27 is also arranged parallel to the driven shaft 13.
7 includes a counter gear 28 that meshes with the forward gear 21 and the reverse idler gear 26 at the same time, and a final reduction gear 29.
are fixed, and the final reduction gear 29 meshes with the ring gear 31 of the differential device 30 to transmit power to the output shaft 32.

In the transmission having the above configuration, a direct coupling clutch 5°, a direct coupling drive gear 7, a counter gear 28. The final reduction gear 29 and the differential device 30 constitute a direct drive path, and the external gear 8. Internal gear9. Continuously variable transmission 10, starting clutch, tick 0. Forward gear 21. Counter gear 28. Final reduction gear 2
9 and the differential device 30 constitute a belt drive path. Then, the input shaft 4 in the direct drive path
The direct transmission ratio between the input shaft 4 and the output shaft 32 is set to be approximately the same as the maximum speed ratio between the input shaft 4 and the output shaft 32 in the belt drive path.

FIG. 2 shows a hydraulic control device for controlling the hydraulic pressure of the hydraulic chamber 18, the starting clutch 20, and the direct coupling clutch 5, where 40 is a solenoid pulp for speed change control, 50 is a solenoid valve for starting control, and 60 is a solenoid pulp for direct coupling control. , 70
is a control circuit such as a microcomputer.

The solenoid pulp 40 for speed change control has the structure shown in FIG.
An output port 43 for outputting the water and a drain boat 44 are formed. In the central valve chamber 45, there is a magnetic ball 46 that selectively opens and closes the input port 42 and the drain boat 44.
is housed in a movable manner. This ball 46 normally closes the input port 42 by a spring 47, and when an exciting current flows through the coil 48, the ball 46 closes the input port 42.
It moves to the right in the figure to open the input port 42 and close the drain boat 44.

The solenoid pulp 50 for start control and the solenoid valve 60 for direct connection control have completely the same structure as the solenoid pulp 40 for speed change control, and are also denoted by the reference numerals corresponding to those in FIG. 3. That is, 51.61 is pulp body, 5
2.62 is an input port leading to the hydraulic pressure source, 53.63 is an output port leading to the starting clutch 20 and direct coupling clutch 5, respectively, 54.64 is a drain boat, 55.65 is a valve chamber, 56.66 is a ball, 57. 67 is a spring, 5
8.68 is a coil.

The control circuit 70 receives the engine rotation speed, output rotation speed of the output shaft 32 (or vehicle speed), throttle opening θ, brake signal, position switch signal, etc. from a sensor (not shown), and controls the solenoid pulp 40 according to the driving state. .5
The duty is controlled to 0.60.

Now, if the duty ratio of the control signal output from the control circuit 70 to the solenoid pulps 40, 50, 60 is D, the output oil pressure pHl of the solenoid pulps 40, 50, 60 is
Since IT is given by P-PL-D and P5 (line pressure) is a constant value,
The output leg pressure PIIIT is controlled only by the duty ratio. Therefore, the transmission gear ratio of the continuously variable transmission 10, the transmission torque of the starting clutch 20 and the direct coupling clutch 5 are controlled by the control circuit 70.
It can be freely controlled by the duty ratio output from to each solenoid pulp 40, 50, 60. Note that the duty ratio of each solenoid pulp 40, 50, 60 in the operating state is stored in the control circuit 70 as, for example, a data map.

The overall operation of the hydraulic control system having the above configuration will be explained with reference to the shift diagram shown in FIG. 4.

First, during normal starting, the starting clutch 20 is gradually engaged from point A, and when reaching point B, the starting clutch 20 is maintained in the engaged state and the starting control is shifted to shift control. In shift control, acceleration is first performed along the straight line of the lowest speed ratio, and when the input rotation speed N1 reaches the target input rotation speed N5 corresponding to the throttle opening at that time, the shift region is entered and the target input rotation speed N is set. Shift to the high speed ratio side while maintaining the same. When the gear ratio reaches the maximum speed ratio, that is, the direct coupling transmission ratio (point D), the starting clutch 20 is disconnected and the direct coupling clutch 5 is engaged, thereby shifting to direct coupling drive. Hydraulic chamber 1 in direct drive
Since the hydraulic pressure of 8 is drained, the continuously variable transmission 10 is maintained at the highest speed ratio and continues to idle. In addition, in order to reduce torque loss during idling, the continuously variable transmission 10 may be shifted to an intermediate boolean ratio during idling.

In addition, if an abnormal situation occurs such as damage to the bell day 5 or failure of the starting clutch 20 itself or the starting control solenoid valve 50, it is impossible to start using the continuously variable transmission path as described above, so Emergency start is performed by the drive path. In this case, as shown by the broken line in FIG. 4, the starting clutch 20 is maintained in a disengaged state, and the direct coupling clutch 5 is gradually engaged to move from point A to point B° to perform emergency starting control. After reaching point B°, the direct coupling clutch 5 is maintained in the engaged state, and the vehicle accelerates along the straight line of the direct coupling transmission ratio.

The transmission torque characteristic of the starting clutch 20 at an idle rotation speed of N7 or more, that is, the transmission torque characteristic a at the time of starting is as follows:
As shown in FIG. 5, like a fluid coupling or a centrifugal clutch, it has a characteristic that is approximately proportional to the square of the engine rotational speed, so that smooth starting performance can be obtained. In addition, in the low rotation range below the idle rotation speed N, the hydraulic pressure is low so that the piston of the starting clutch 20 engages loosely as a clutch, in order to improve responsiveness during starting and prevent shock when the clutch is engaged. is guided, and the transmitted torque is adjusted so as to cause a creep phenomenon. The transmission torque characteristic during creep is set so that the slope slopes upward to the right with respect to the transmission torque characteristic a during start. In other words, if the transmission torque characteristic has a quadratic curve characteristic as shown by the broken line in Fig. 5 even in the low rotation range below the idle rotation speed N, as in the conventional case, the transmission torque at the idle rotation speed N and below. is almost constant, so when switching from neutral range to drive range, the initial idle speed N
The engine speed will drop from , and even if this drop occurs, the transmitted torque will hardly change, so the engine speed will further drop, and in the worst case, there is a risk that the engine will stall. On the other hand, if the slope of the transmitted torque during creep is set upward to the right as described above, and the transmitted torque is set to decrease as the engine speed decreases,
When switching from the neutral range to the drive range, the engine speed does not drop, reliably preventing engine stalling.

In addition, in 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 and the direct coupling clutch 5 are controlled by the solenoid valves 40, 50, and 60 alone, but the invention is not limited to this. For example, the solenoid valve may be controlled by a combination of a solenoid valve and a spool valve. In this case, the solenoid valve is not limited to a system in which the input boat and drain boat are selectively opened and closed using a ball-shaped valve body, but a needle-type solenoid valve may also be used. May be used.

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

Effects of the Invention As is clear from the above explanation, according to the present invention, the transmission torque of the starting clutch in the creep state is controlled so as to decrease as the engine speed decreases, so that it is possible to switch from the neutral range to the drive range. Time,
This suppresses the drop in engine speed and reliably prevents engine stalling.

[Brief explanation of the drawing]

Figure 1 is a skeleton diagram of an example of a V-belt 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 valve, and Figure 4 is a shift line. figure,
FIG. 5 is an example of a transmission torque characteristic diagram of the starting clutch. DESCRIPTION OF SYMBOLS 1... Engine, 4... Input shaft, 10... Continuously variable transmission, 15... V-belt, 18... Hydraulic chamber, 20
... Starting clutch, 32... Output shaft, 40... Solenoid valve for speed ratio control, 50... Solenoid valve for starting control, 60... Solenoid valve for direct connection control, 70... Control circuit . Applicant Daihatsu Motor Co., Ltd. Agent Patent Attorney Hidetaka Tsutsui Figure 3e Figure 5

Claims (1)

[Claims] (1) In an automatic transmission equipped with a sliding starting clutch that can arbitrarily control the transmission torque, the starting clutch generates a creep state during idling, in which the transmission torque in the creep state of the starting clutch is transferred to the engine. A starting clutch control method for an automatic transmission, characterized in that the starting clutch is controlled to gradually decrease as the rotational speed decreases.