JPS6390441A - Method of controlling starting clutch for automatic transmission - Google Patents

Abstract

PURPOSE:To prevent abrupt start and shocks upon engagement, by setting an upper limit to the ascent grade of transmission torque to carry out the slip control of a start clutch even though an abnormally high input rotational speed signal is inputted due to noise in a signal system. CONSTITUTION:Signals from sensors 61 through 64 are inputted to an input interface 66, and a throttle opening degree signal from a sensor 65 is converted into a digital signal by an A/D converter 67. A CPU 68, a ROM 69, a RAM 70, an output interface 71, the input interface 66 and the A/D converter 67 are coupled to each other through a bus 71. The output of the output interface 71 is delivered as a duty control signal for a pulley control solenoid 44 and a start control solenoid 46, through an output driver 73. Further, when the slip control of a start clutch is carried out, an upper limit is set to the ascent grade of transmission torque to prevent occurrence of shocks upon engagement even through an abnormally high input rotational speed signal is inputted due to noise in the signal system.

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 by electronically controlling the transmitted torque, it achieves smooth starting performance similar to an automatic clutch, reduces power loss, and offers greater freedom in starting characteristics. Some proposals have been made to realize the expansion of
1-129339).

When controlling the above-mentioned slip type starting clutch, the transmission torque-human power rotation speed characteristic of the starting clutch is set in advance,
In accordance with this characteristic, slip control is generally performed so that the transmitted torque gradually increases as the input rotational speed increases. During normal starting, the input rotation speed does not rise very rapidly, so the transmitted torque does not increase abnormally. When the electronic control unit that processes the signal malfunctions, the input rotation speed signal may rise to an unbearable level, and the transmitted torque corresponding to the input rotation speed also rises rapidly, causing the vehicle to suddenly jump out. or 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 prevent the input rotational speed signal from increasing to such an extent that it cannot be heard during commuting due to noise in the signal system or malfunction of the electronic control device.
An object of the present invention is to provide a starting clutch control method for an automatic transmission that suppresses an abnormal increase in transmission torque of a starting clutch and enables smooth starting at all times.

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,
In an automatic transmission in which the starting clutch is subjected to slip control so that the transmission torque increases as the input rotation speed increases according to a predetermined characteristic, an allowable limit of the time gradient of the transmission torque during the slip control is set, The present invention is characterized in that when the time gradient of the transmitted torque corresponding to the actual input rotational speed signal exceeds the above-mentioned allowable limit, the time gradient of the transmitted torque is diuresed so that it becomes below this allowable limit.

That is, since the upper limit of the time gradient of the transmitted torque is fixed, even if the input rotational speed signal increases abnormally due to noise in the signal system, the rate of increase in the transmitted torque is suppressed. Therefore, it is possible to avoid shocks and engine stalls caused by the sudden movement of the vehicle or 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 lO includes a drive pulley 1 provided on a drive shaft 11.
2, a driven pulley 14 provided on the driven shaft 13, and a belt 15 wound between both pulleys. 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 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 sheep 14a and a movable sheep 14b, and a hydraulic chamber 18 for speed ratio control is provided behind the movable sheep 14b. 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 boat 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 Pafr of 50 is given by the following equation.

P[XAI = PL XDXA, 2 +F ・(1
1 In the above formula, A, , A2 are the spool valves 50, respectively.
pressure receiving area of lands 50a and 50b, PL is line pressure,
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. 3, its output oil pressure PGJT is calculated by the following formula % formula % (In formula 11 and formula (2), A, , A2.PL+
Since F is a constant value, the duty ratio and the output oil pressure P station are proportional. On the other hand, since the gear ratio of the continuously variable transmission 10 and the transmission torque of the starting clutch 20 can be controlled by the output oil pressures P and M, the gear ratio of the continuously variable transmission 10 and the transmission torque of the starting clutch 20 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 20 or the driven side boolean IJ 14). 64 is a sensor that detects each shift position of P, R, N, D, L, 65 is a sensor that detects the throttle opening degree, and the signals of the sensors 61 to 64 are as follows: The signal from the sensor 65 is input to an input interface 66 and converted into a digital signal by an A/D converter 67. 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 CPtJ6
8, the ROM 69, the RAM 2O, the output interface 71, 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 approximately proportional to the square of the input rotation speed, and allows for smooth starting. I'm trying to get sex. 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. Adjusted to generate a veri (creep) 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), the hydraulic pressure is not fully applied 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.

When the difference in output rotation speed becomes less than the set value Nes, then
Even if the starting clutch 20 is fully engaged at the time point, there is almost no friction, and the starting control can be completed in a short time. Therefore, the difference between the person and the output rotation speed is the set value Nes.
When the following occurs, the transmission torque of the starting clutch 20 is immediately set to the maximum T (duty ratio 100%) from point A as shown by the broken line in Figure 5, and the starting clutch 20 is fully engaged to complete the starting control. do.

Note that the set value New 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 the straight line B in FIG.
The setting value Nes may be set to increase as the input rotation speed increases with a constant slope (inclination ε) as shown in FIG. This has the advantage of reducing engagement shock, absorbing detection variations in the high rotation range, and making it easier to determine whether engagement is complete.

By the way, the starting clutch control method as described above has no problems when the electrical system is operating normally, but for example, when there is noise or a disconnection in the signal system of the sensor 63 that detects the input rotation speed, or When the CPU6B itself malfunctions, an abnormally high input rotation speed signal is input even though the actual input rotation speed is low, and as a result, the transmission torque (duty ratio) corresponding to the input rotation speed is read out from Fig. 5. The solenoid for starting liIIm will be powered. That is, when the slip control should normally be performed slowly, two strong transmission torques are applied, causing the vehicle to jump suddenly or causing a large engagement shock.

In order to solve this problem, in the present invention, the starting clutch 20
When the starting clutch 20 should be controlled by slipping, that is, when the difference between the output rotation speed of the starting clutch 20 is greater than the set value Nes, even if a command is issued to generate excessive transmission torque due to an abnormal input rotation speed signal, the transmission will not be performed. This restricts the time gradient of torque so that it does not exceed a permissible limit, thereby preventing the vehicle from jumping out or causing an engagement shock. The shaded area in FIG. 7 shows the change range of the transmitted torque that normally occurs during slip control of the starting clutch 20, and the permissible limit of the time gradient of the transmitted torque in the slip state is located at a position slightly higher than this shaded range (
A straight line D) is set. The above straight line also serves as the time gradient of the transmitted torque when the starting clutch 20 is fully engaged, and even if the difference between the output rotation speed of the starting clutch 20 becomes less than the set value Nes, the starting clutch 20 is completely engaged immediately. First, the transmitted torque is completely suspended with a certain time gradient! :i (point E)
It is set to rise to.

Note that the time gradient of the transmitted torque at full engagement (the permissible time gradient at the time of slippage) 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 Since the torque is large and the time gradient of the transmitted torque is large, there is no risk that the starting clutch will stall the engine, and rapid acceleration is possible.
When the throttle opening is high as in II D', the time gradient of the transmitted torque may be increased.

Next, an example of the starting clutch control method of the present invention will be described in Section BV.
Explain according to J.

When the start control starts, the input rotation speeds N and n of the start clutch 20 and the output rotation speed NM are first input (80).
, the input rotational speed Nln is determined by the rotational speed of the driven shaft 13, but since this manual rotational speed N1n is proportional to the engine rotational speed during the starting process, the engine rotational speed may be substituted.
In addition, the output rotation speed N 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 NIIIT is proportional to the vehicle speed, , the absolute value of the difference between the input rotation speed and the output rotation speed (I N +n N LII
The value obtained by dividing TI ) by the manual rotation speed NIn is compared with a set value ε (81). This value ε is the slope of the straight line C in FIG. 6, and is set to about 0.1, for example. If the value obtained by dividing the absolute value of the difference between the input rotation speed and the output rotation speed by the manual rotation speed is less than or equal to the set value ε, the start is ready to be completed, and the starting clutch 20 is fully engaged. In order to increase the transmission torque by increasing the slope of the straight line in Figure 7 (
82).

Specifically, the start control solenoid, Id 46, is turned ON (duty ratio 100%) with a time gradient, and the duty is controlled at 1:1. Furthermore, 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.
Next, read out the current duty ratio DT corresponding to the input rotation speed from the transmission torque characteristics (Fig. 5) (83), and then compare this current duty ratio DT with the duty ratio DT-1 a certain period of time ago Δτ. Difference (D y D T-1)
is compared with a predetermined value (α×ΔT) (84), the above α is
Figure 7 shows the slope of the straight line. DT-D knee 1kuα×ΔT
If so, it means that 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, so it can be used for starting control as it is. A duty ratio is output to the solenoid 46, and the starting clutch 20 is controlled to slip (8
5). 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. This means that D instead of D
T-+10α×ΔT is output to the start control solenoid 46 (86). 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. 7th torque
The time gradient is suppressed to the upper limit of the straight line. With this-
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 V-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 performing slip control on the starting clutch, even if an abnormally high input rotation speed signal is input due to noise in the signal system, the rising slope of the transmitted torque is not affected. Since the limit is set, it is possible to prevent situations such as the vehicle suddenly jumping out or a large engagement shock occurring, and it is possible to always achieve smooth starting performance.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an example of a V-belt type continuously variable transmission to which the present invention is applied, FIGS. 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. Representative: Patent Attorney Hidetaka Tsutsui Figure 1 Figure 2 Figure 3 Figure 9: J4 Figure Figure 5 Figure 6 Shake 77 Rotation Calendar Figure 8

Claims (1)

[Claims] (1) A slip-type starting clutch is provided that allows the transmission torque to be arbitrarily controlled from the outside, and the starting clutch is subjected to slip control in accordance with predetermined characteristics so that the transmission torque increases as the input rotation speed increases. In an automatic transmission, a permissible limit for the time gradient of the transmitted torque during the above slip control is set, and when the time gradient of the transmitted torque corresponding to the actual input rotation speed signal exceeds the above permissible limit, it is determined that the time gradient of the transmitted torque is below this permissible limit. 1. A starting clutch control method for an automatic transmission, characterized in that the time gradient of transmitted torque is limited so that the time gradient of transmitted torque is limited.