JPS6393634A - Start clutch control method for automatic speed changer - Google Patents

Abstract

PURPOSE:To prevent engagement shock of a slide type start clutch by allowing the transmitted torque to rise to the fully engaged state through following a time gradient when the clutch is put in engagement on the occasion that the difference between input and output numbers of revolutions of the clutch has become below a set value. CONSTITUTION:A follower shaft 13 of a stepless speed changer 10 is coupled with a hollow shaft 19 supported rotatably at the periphery of said follower shaft 13 through a start clutch 20, which is controlled with oil pressure supplied via a start control valve 45. This start control valve 45 is so controlled by an electronic control device 60 that the start clutch 20 is put under slide control or in full engagement depending upon whether the difference between input and output numbers of revolutions of clutch 20 is greater or smaller than the set value. That is, when said difference has become the set value, the start clutch 20 is going to be put in full engagement, which is however not accomplished directly, but so controlled that the transmitted torque rises to fully engaged state through following a time gradient.

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 in which transmission torque can be arbitrarily controlled from the outside.

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 a large power loss 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. Furthermore, although an automatic clutch does not require external control, it is impossible to change the transmission torque characteristics and has the disadvantage that the starting characteristics are fixed.

Therefore, by using a slipping clutch such as a wet multi-disc clutch or an electromagnetic powder clutch and electronically controlling the transmitted torque, we can achieve smooth starting performance similar to that of an automatic clutch, reduce power loss, and have more freedom in starting characteristics. Some proposals have been made to realize the expansion of
1-129339).

In the case of the slip-type starting clutch mentioned above, the judgment as to whether to fully engage or maintain the slipping state is made based on whether the difference between the input rotation speed and the output rotation speed of the starting clutch is less than or equal to the set value. It is the simplest. For example, if the set value is set to Nes, when the difference between the input rotation speed and the output rotation speed is greater than or equal to Nes, slip control is performed so that the engagement force of the starting clutch is gradually increased, and when it is less than Nes, the starting clutch is fully engaged. All you need to do is to complete the start.

However, in the case of the starting clutch control method as described above,
The following problems may occur when the vehicle is reversing.

For example, if the brakes are not applied when the vehicle is idling in the D range on an uphill slope, the vehicle may move backwards due to inertia. At this time, the sensor that detects the engagement of the starting clutch and the output rotation speed cannot detect the direction of rotation. In other words, the engagement and output rotation speed of the starting clutch are detected as absolute values, so even if the vehicle is traveling in the opposite direction. However, the control device determines that the vehicle is starting, and fully engages the starting clutch, which may cause the engine to stall.

In addition to when the vehicle is going backwards, the starting clutch is also engaged.

If noise is added to the signal system of the sensor that detects the output rotational speed, or if the electronic control device that processes the sensor signal malfunctions, the starting clutch may be erroneously fully engaged when it should be in slip control, causing a large engagement. There is also a risk that a shock may occur.

Purpose of the Invention The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a starting clutch for an automatic transmission that prevents engine stalling and shock due to incorrect engagement of the starting clutch, and enables smooth starting at all times. The objective is to provide a control method.

Structure of the Invention In order to achieve the above object, the present invention includes a slip-type starting clutch that can arbitrarily control transmission torque from the outside,
When the difference between the input and output rotational speeds of the starting clutch is equal to or greater than a set value, the starting clutch is controlled to slip, and when the difference between the input and output rotational speeds becomes less than the set value, the starting clutch is fully engaged. The automatic transmission is characterized in that when the difference between the engagement and output rotational speeds of the starting clutch becomes less than a set value, the transmitted torque is increased to a fully engaged state with a time gradient.

For example, even if the starting clutch is incorrectly engaged when the vehicle is traveling in reverse,
Since the transmitted torque increases with a time gradient, the reverse speed of the vehicle decreases during that time, and the vehicle eventually stops. Thereafter, the vehicle starts to start normally, and it is possible to avoid shocks and engine stalls caused by sudden engagement of the starting clutch.

DESCRIPTION OF EMBODIMENTS FIG. 1 shows a belt-type 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 5 is fixed to the end of the input shaft 4, and this external gear 5 meshes with an internal gear 6 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-side boot 1J provided on the drive shaft 11.
12, a driven pulley 14 provided on the driven shaft 13, and a belt 15 wrapped around both pulleys.

The drive pulley 12 has a fixed sheave 12a and a movable sheave 12.
b, and 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 belt 15 from loosening, and these thrusts provide belt tension necessary for torque transmission to the heald 15. ing.

On the other hand, the driven pulley 14 as well as the driving pulley 12,
It has a fixed sheave 14a and a movable sheave 14b,
Behind the movable sheave 14b is a hydraulic chamber 18 for controlling the gear ratio.
is provided. The hydraulic pressure to this hydraulic chamber 18 is controlled by a pulley control valve 43, 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. The hydraulic pressure applied to the starting clutch 20 is controlled by a starting control valve 45, which will be described later. A forward gear 21 and a reverse gear 22 are rotatably supported on the hollow shaft 19, and a forward/reverse switching dog clutch 23 connects either the forward gear 21 or the reverse gear 22 to the hollow shaft 19. It is designed to be connected. The reverse gear 2 is attached to the reverse idler shaft 24.
A reverse idler gear 25 meshing with the reverse idler gear 26 and another reverse idler gear 26 are fixed. Further, the counter shaft 27 is provided with the forward gear 21 and the reverse idler gear 26.
The counter gear 28 and the final reduction gear 2 are simultaneously engaged with the
9 is 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.

The pressure regulating valve 40 regulates the hydraulic pressure discharged from the oil reservoir 41 by the oil pump 42, and outputs it as line pressure to the pulley control valve 4.
3 and the start control valve 45. Pulley control valve 4
3 and the start control valve 45 actuate the solenoids 44 and 46 in accordance with the duty control signal output from the electronic control device 60, and control the line pressure to control the driven pulley 14, respectively.
Control hydraulic pressure is output to the hydraulic chamber 18 and the starting clutch 20.

The specific structure of the control valves 43 and 45 includes, for example, a combination of a spool valve 50 and a solenoid valve 52 as shown in FIG.
and the drain port 55 are selectively opened and closed, and the output boat 5
It is also possible to use a single three-bottom electromagnetic valve that outputs control hydraulic pressure to 6. For example, when the control valve 43, 45 is configured with a spool valve 50 and a solenoid valve 52 as shown in FIG. 2, and the duty ratio output from the electronic control device 60 to the solenoid valve 52 is D, The output oil pressure P of 50 is given by the following equation.

PQJTxA,=P,×DxA2+F...(1)
In the above formula, A, A2 are the pressure receiving areas of the lands 50a and 50b of the spool valve 50, P is the line pressure, and F
is the spring load of the spring 51.

In addition, when the control valve 43.45 is composed of a single solenoid valve as shown in FIG.
Since L and F are constant values, the duty ratio and the output oil pressure P are proportional. On the other hand, since the gear ratio of the continuously variable transmission 1o and the transmission torque of the starting clutch 20 can be controlled by the output oil pressure PO, the gear ratio of the continuously variable transmission 10 and the transmission torque of the starting clutch 2° can be controlled depending on the duty ratio. This means that it can be controlled.

FIG. 4 shows a block diagram of the electronic control device 60, and in the figure,
61 is a sensor that detects the engine rotation speed (or the rotation speed of the input shaft 4), 62 is a sensor that detects the vehicle speed, and 63 is a sensor that detects the rotation speed of the driven shaft 13 (the input rotation speed of the starting clutch 2° or the driven side pulley 14). 64 is a sensor that detects each shift position of P, R, N, D, and L. 65 is a sensor that detects the throttle opening degree, and the signals of the sensors 61 to 64 are is input to the input interface 66, and the signal of the sensor 65 is input to the A/D converter 6.
7, it is converted into a digital signal. 68 is a central processing unit (CPU), and 69 is a read-only memory (ROM) in which programs and data for controlling the pulley control solenoid 44 and the start control solenoid 46 are stored.
, 70 is a random access memory (RAM) that temporarily stores signals and parameters sent from each sensor;
71 is an output interface, and these cPU68
, ROM69, RAM M2O, output interface 7
1. The input interface 66 and the A/Di converter 67 are interconnected by a bus 72.

The output of the output interface 71 is output as a duty control signal to the pulley control solenoid 44 and the start control solenoid 46 via the output driver buffer 3.

FIG. 5 shows an example of the transmission torque characteristic of the starting clutch 20 set in the electronic control device 60. Like a fluid coupling or a centrifugal clutch, it has a characteristic that is almost proportional to the square of the input rotation speed, and has a smooth We are trying to get a good start. In addition,
The vertical axis in FIG. 5 may be the clutch oil pressure instead of the transmitted torque, and if the start control valve 45 is configured as shown in FIGS. 2 and 3, the clutch oil pressure and the duty ratio are proportional. The vertical axis may represent the duty ratio. In the low rotation range near the idle rotation speed Na, low oil pressure is introduced so that the starting clutch 20 generates a low transmission torque Ta, with the aim of improving responsiveness during starting and preventing shock when the clutch is engaged. (creep) has been adjusted to generate the condition. The transmission torque Ta at the time of slipping is set to a magnitude that allows the vehicle to stop without going backwards, for example, on an uphill slope. Note that the neutral range (N
, P range), no oil pressure is introduced to the starting clutch 20, so the starting clutch 20 is in a completely disconnected state.

The starting clutch 20 is slip-controlled so that the transmission torque increases as the input rotation speed increases, as shown in the characteristics shown in FIG. At that point, start clutch 2
There is almost no shock even when 0 is fully engaged, and the start control can be completed in a short time. Therefore, when the difference between the input and output rotation speeds becomes less than the set value Nes, the transmission torque of the starting clutch 20 is immediately set to the maximum Tゎ (duty ratio 100%) from point A, as shown by the broken line in Fig. 5. The starting clutch 20 is fully engaged to complete the starting control.

Note that the set value Nes for determining whether or not the starting clutch 20 should be fully engaged may be constant regardless of the input rotation speed as shown in line 2 in FIG.
The setting value Nes may be set to increase as the input rotation speed increases with a constant slope (m x ε) as shown in FIG. In the case of straight line C, there is an advantage that the engagement shock of the starting clutch 20 can be reduced in the low rotation range of the input rotation speed, and detection variations can be absorbed in the high rotation speed range, making it easy to determine whether engagement is complete.

By the way, the above-mentioned starting clutch control method does not cause any problems when the vehicle starts normally, but there is a risk that the engine stalls when the vehicle is traveling backwards on a slope.

In other words, the vehicle speed sensor is generally a reed switch driven by a magnet turned by the rotation of the speedometer cable, but since this vehicle speed sensor outputs the rotation speed signal as an absolute value, For example, even if the vehicle is traveling backwards on an uphill slope in the D range, it is not possible to determine whether the vehicle is traveling forward or backwards. This also affects the detection of the starting clutch engagement and output rotation speed, and since the starting clutch engagement and output rotation speed are detected as absolute values, if the difference between them becomes less than the set value Nes, the starting clutch 20 is immediately activated. is fully engaged, causing the engine to stall when traveling in reverse. A similar problem can be caused by noise in the signal system of the sensor that detects the starting clutch engagement and output rotation speed.
Alternatively, it may occur when the CPU 68 malfunctions.

In order to solve this problem, in the present invention, the starting clutch 20
When it is determined that the starting clutch 20 should be fully engaged, that is, when the difference between the input and output rotation speeds of the starting clutch 20 becomes less than the set value Nes, the starting clutch notch 20 is not fully engaged immediately,
The transmission torque is increased to a fully engaged state with a time gradient. In this way, for example, even if the starting clutch is engaged incorrectly when the vehicle is moving backwards, the transmitted torque will increase with a time gradient, during which time the vehicle will transition from the reversed state to a stop and then to starting, and the starting clutch This prevents the engine from stalling due to sudden engagement. A straight line D in FIG. 7 shows the time change of the transmitted torque when the starting clutch 20 is fully engaged, and the transmitted torque increases with a constant slope to the fully engaged state (point E).

The shaded area in FIG. 7 shows the change range of the transmitted torque that may occur during slip control of the starting clutch 20. A straight line is located at a position slightly higher than this shaded range, and this straight line represents the time period of the transmitted torque in the slipping state. This is the permissible slope limit.

Note that the time gradient of the transmitted torque at full engagement may be constant regardless of the throttle opening as shown in the straight line in Figure 7, but when the throttle opening is high, the input torque is large and the time gradient of the transmitted torque is Even if it is increased, there is no risk that the starting clutch will cause the engine to stall, and a sudden acceleration start is possible, so the time gradient of the transmitted torque may be increased when the throttle opening is high, as shown by the straight line 2° in FIG.

Next, an example of the starting clutch control method of the present invention will be explained with reference to FIG.

When starting control starts, first input the input rotational speed N, n and output rotational speed N[Ll, of the starting clutch 20 (
80). The input rotational speeds N and n are determined by the rotational speed of the driven shaft 13, but since the input rotational speed N1o is proportional to the engine rotational speed during the starting process, the engine rotational speed may be substituted. In addition, the output rotation speed NU is determined by the product of the vehicle speed (converted to the rotation speed of the output shaft 32) and the gear ratio from the hollow shaft 19 to the output shaft 32, but since the output rotation speed NU and the vehicle speed are proportional to each other, , the vehicle speed may be substituted. Next, the value obtained by dividing the absolute value of the difference between the input rotation speed and the output rotation speed (IN; n-NUl) by the input rotation speed N1n is compared with the set value ε (81)
. This value ε is the slope of the straight line C in FIG. 6, and is, for example, 0.
It is set to about 1. If the value obtained by dividing the absolute value of the difference between the input rotation speed and the output rotation speed by the input rotation speed is less than or equal to the set value ε, it is possible to complete the start, so the start clutch 20 is set to fully engage. The transmitted torque is increased by the straight slope in Figure 7 (82).

Specifically, the start control solenoid 46 is duty-controlled with a time gradient until it becomes ON (duty ratio 100%). Also, if the value obtained by dividing the absolute value of the difference between the input rotation speed and the output rotation speed by the input rotation speed is greater than or equal to the set value ε, it means that the start has not yet been completed. Read out the current duty ratio D□ corresponding to the input rotational speed from (Fig. 5) (83), and then read the difference (D knee D T-, ) to a predetermined value (
α×ΔT) (84). The above α is the slope of the straight line in FIG. D□-D If T-1<α×ΔT, the transmission torque of the starting clutch 20 in the slipping state has not increased abnormally.In other words, the time gradient of the transmission torque is below the straight line in Figure 7. Since it means that there is, the duty is directly compared to the start control solenoid 46. is output, and the starting clutch 20 is controlled to slip (85). On the other hand, if D knee D T-1≧α×ΔT, the transmission torque of the starting clutch 20 in the slipping state has increased abnormally.In other words, the time gradient of the transmission torque is above the straight line in FIG. Therefore, instead of D□, D T-1
+α×ΔT is output to the start control solenoid 46 (8
6). In other words, even if a signal is input to increase the transmitted torque with a time gradient greater than or equal to a straight line, it is determined that this is an error signal due to a failure in the signal system for detecting the input rotation speed or the electronic control unit 60, and the transmission is stopped. The torque is suppressed to a time gradient with the upper limit being the straight line shown in Figure 7. As a result, even if an error signal is received, smooth starting performance without shock can be achieved.

In the present invention, the starting clutch 20 is not limited to a wet multi-disc clutch, but may also be a dry clutch or an electromagnetic powder clutch. In the case of an electromagnetic powder clutch, the transmitted torque can be directly controlled by an electric signal, eliminating the need for a start control valve and simplifying the hydraulic circuit.

Further, the automatic transmission of the present invention is not limited to a continuously variable transmission such as a belt type continuously variable transmission or a toroidal type continuously variable transmission, but it goes without saying that a general planetary gear type automatic transmission can also be used.

Effects of the Invention As is clear from the above explanation, according to the present invention, when the difference between the starting and output rotation speeds of the starting clutch 7 becomes less than the set value,
Since the transmitted torque is raised to the fully engaged state with a time gradient, even if the starting clutch is engaged by mistake when the vehicle is traveling in the opposite direction or when there is noise in the signal system, the starting clutch will still be activated. There is sufficient time until the clutch is fully engaged, and shocks and engine stalls caused by sudden engagement of the starting clutch can be avoided.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of an example of a belt-type continuously variable transmission to which the present invention is applied; Figures 2 and 3 are specific structural diagrams of a control valve;
Fig. 4 is a block diagram of the electronic control device, Fig. 5 is a transmission torque characteristic diagram of the starting clutch, Fig. 6 is a diagram showing the relationship between set value and input rotation speed, and Fig. 7 is a diagram of the transmission torque of the starting clutch. FIG. 8, which is a diagram showing changes over time, is a flowchart showing an example of the method of the present invention. 1... Engine, 10... Continuously variable transmission, 20...
- Starting clutch, 32... Output shaft, 45... Starting control valve, 46... Solenoid for starting control, 60... Electronic control device. Applicant: Daihatsu Motor Co., Ltd. Agent: Patent Attorney: Hidetaka Tsutsui, Figure 5, 77 Rotary Maki 171. 1 ship 1, °＼Both shoulders Figure 8■－－－－－－－－ Last day

Claims (2)

[Claims] (1) Equipped with a slip-type starting clutch that can arbitrarily control the transmitted torque externally, and when the difference between the input and output rotation speeds of the starting clutch is greater than a set value, the starting clutch is slip-controlled and the input and output rotation speeds are controlled. In an automatic transmission that fully engages the starting clutch when the difference becomes less than a set value, when the difference between the starting clutch engagement and output speeds becomes less than the set value, the transmitted torque is changed to a time gradient. A starting clutch control method for an automatic transmission, characterized in that the starting clutch is raised to a fully engaged state. (2) The starting clutch control method for an automatic transmission according to claim 1, wherein the time gradient of the transmitted torque is increased as the throttle opening increases.