JPH0467062B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for controlling an automatic transmission, and more particularly, to a method for protecting occupants and the automatic transmission in the event that a vehicle speed sensor that detects vehicle speed fails. .

[Conventional technology]

Generally, in electronically controlled automatic transmissions,
The gear ratio of the transmission gear is automatically controlled based on the throttle opening and vehicle speed. However, if the vehicle speed sensor that detects the vehicle speed malfunctions or the wiring cable is disconnected while driving, the vehicle speed signal becomes zero.
There are problems when the transmission is downshifted suddenly, causing the engine to rev up, or when a large gear shift shock is applied.

In order to solve such problems, the special public
As described in Publication No. 18574, the engine rotation speed is detected, and when this value becomes equal to or higher than the engine rotation speed corresponding to normal gear shifting, the upshift is performed, which approximates the case when the vehicle speed sensor is operating normally. A device in which a speed change operation is performed is known.

[Problem to be solved by the invention]

By the way, if the vehicle speed signal line is disconnected, the vehicle speed signal will instantly become zero, so the above method can prevent sudden downshifts. If the wire is disconnected, the speedometer needle continues to rotate due to inertia, so it takes time for the vehicle speed signal to reach zero. In such a case, downshifting is performed as the vehicle speed signal decreases, and there is a risk that the same problems as in the past may occur.

On the other hand, there is also known a vehicle in which the vehicle speed signal is obtained from two systems: the speedometer and the output shaft of the transmission. In this case, even if one system fails, there will be no problem in driving as long as the other system is operating normally, but if the vehicle speed sensor and wiring cable are
Since it is necessary to provide a system, there is a drawback that the cost is high.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an automatic transmission control method that can determine failures in all aspects of a vehicle speed sensor using a single system of vehicle speed signals and can safely control an automatic transmission.

[Means to solve the problem]

In order to achieve the above object, the present invention provides that, when a vehicle speed signal suddenly decreases, the difference between the vehicle speed value immediately before the decrease and the current vehicle speed value is a deceleration calculated from the maximum deceleration amount per unit time when the brake is applied. When the level is higher than the determination level, the failure determination means outputs a failure signal to maintain the current transmission gear position.

[Effect]

In other words, when the vehicle speed signal suddenly decreases, if this is a sudden deceleration that cannot normally occur, it means that the vehicle speed sensor is malfunctioning.
This system maintains the current gear position (shift hold) to avoid sudden downshifting.

〔Example〕

FIG. 1 shows an example of a control device according to the present invention, in which 1 is a throttle opening sensor that detects the throttle opening, 2 is a vehicle speed sensor that is installed on one of the speedometer or the transmission output shaft and detects the vehicle speed, and 3 is a throttle opening sensor that detects the throttle opening. 1 is an engine rotation speed sensor that detects the engine rotation speed, and these sensors 1, 2, and 3 are similar to those mounted on general automobiles.

Reference numeral 4 denotes a failure determination means, which receives a vehicle speed signal from the vehicle speed sensor 2 at regular intervals;
The vehicle speed V immediately before starting deceleration when the vehicle speed signal from the vehicle suddenly decreases. The difference (V ₀ -V) between the vehicle speed V (referred to as initial speed) and the vehicle speed V during deceleration (referred to as instantaneous value) is determined, and this difference is compared with a preset deceleration determination level α. Note that if V ₀ −V is the speed difference (deceleration) in a unit time interval, the deceleration determination level α should be the maximum deceleration amount (maximum deceleration) per unit time when the brake is applied, and V ₀ −V is a speed difference at another time interval Δt, the deceleration determination level α may be set as the product of the maximum deceleration amount per unit time when the brake is applied and the time interval Δt. and,
In the case of V ₀ −V>α, it means that deceleration is being performed in a way that is normally impossible (vehicle speed sensor 2 is malfunctioning), so the failure determination means 4 outputs a failure signal and V ₀ If −V<α, a non-fault signal is output. The failure determination means 4 also includes the engine rotation speed N detected by the engine rotation speed sensor 3.
The engine speed N is also input and compared with a preset reference value _Ns . Then, when N>N _s , the fault signal continues to be output, and when N<N _s , the fault signal is canceled and a non-fault signal is output. The above reference value N _s can be the engine speed when idling or the engine speed when the AT converter stalls, and from this, it is determined that the vehicle is running when N > N _s . can.

Reference numeral 5 denotes a transmission gear position determining means, into which the throttle opening signal from the throttle opening sensor 1 and the signal from the failure determining means 4 are input. The transmission gear position determining means 5 maintains the current transmission gear position regardless of the throttle opening signal when the signal output from the failure determination means 4 is a failure signal (V ₀ −V>α). When there is a non-fault signal (V ₀ -V<α), a shift signal corresponding to the vehicle speed and throttle opening is output in accordance with a normal shift operation. The output signal from the transmission gear position determining means 5 operates a hydraulic circuit switching solenoid valve (not shown) of the transmission via the shift output means 6.

Next, the operation of the failure determination control device having the above configuration will be explained with reference to the flowchart shown in FIG.
First, after starting, the throttle opening degree and vehicle speed (V ₀ , V) are sequentially detected, the failure determination means 4 determines the difference between the vehicle speed V ₀ and the instantaneous value V, and this difference is calculated as the deceleration determination level α. compare. If V ₀ −V<α, the gear position is determined and shifted according to the normal gear shifting operation. In the case of V ₀ −V>α, it means that the vehicle speed sensor 2 is malfunctioning, so the warning lamp flashes and the malfunction determination means 4 inputs a malfunction signal to the transmission gear position determination means 5. command to maintain the current transmission gear position. In other words, sudden downshifts are not performed, and engine revving and gear shift shock are prevented.

Next, when the driver maintains the shift gear position while flashing the warning lamp, the driver becomes aware of the abnormality and lowers the throttle opening and operates the brake. Then, the engine speed N also begins to decrease, and this engine speed N is compared with a reference value _Ns , and if N> _Ns , the current transmission gear position is continued to be maintained. On the other hand, if N<N _s , the failure determining means 4 outputs a non-failure signal, cancels maintenance of the gear position (shift hold release), and returns to normal gear shifting operation. Then, the transmission downshifts to the first speed according to (≒0) and the throttle opening. This makes it possible to stop the vehicle safely without causing shock to the occupants or the automatic transmission.

In the above embodiment, failure determination was explained when the vehicle speed signal decreased for a certain period of time, such as when the speedometer cable was disconnected. Even when the vehicle speed sensor is worn out, it is possible to determine whether the vehicle speed sensor is malfunctioning in the same way as described above. That is, when the vehicle speed signal instantaneously becomes zero, since the instantaneous value V is zero, V ₀ -V is naturally larger than α, and the current gear position is maintained in the same order as above,
Prevents gear shift shock and engine revving. Therefore, the present invention can deal with all types of failures in the transmission gear 2.

Furthermore, in the above embodiment, it was determined whether to continue to maintain the current gear position or to release shift hold by comparing the engine speed N and the reference value _Ns , but this is not the only option. First, it is also possible to make a determination based on, for example, the negative pressure in the intake pipe of the engine. That is, as shown in FIG. 1, an engine intake pipe negative pressure sensor 7 is provided in place of the engine rotation speed sensor 3, and its intake pipe negative pressure signal P is input to the failure determination means 4. Compare with the stored reference value P _s . This reference value P _s can be, for example, the negative pressure in the intake pipe when the AT converter stalls. and,
If V ₀ −V > α and P > P _s , it means that the vehicle is running and the vehicle speed sensor 2 is malfunctioning, so the failure signal from the failure determination means 4 is continued and the current transmission gear is It continues to maintain its position.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, even if the vehicle speed sensor fails due to any cause while the vehicle is running, a sudden downshift will not be performed, so that engine revving and gear shift shock can be prevented. Further, in the present invention, since a failure of the vehicle speed sensor is determined from the signals of one system of vehicle speed sensors, there is no need to install a separate sensor, and the configuration can be made at low cost.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a control device according to the present invention, and FIG. 2 is a flowchart showing its operation. 1... Throttle opening sensor, 2... Vehicle speed sensor,
3...Engine speed sensor, 4...Failure determination means,
5...Transmission gear position determining means, 7...Engine intake pipe negative pressure sensor.

Claims (1)

[Claims] 1. In an automatic transmission that automatically controls the gear ratio of a transmission gear based on a throttle opening signal and a vehicle speed signal, when the vehicle speed signal suddenly decreases, the vehicle speed value immediately before the decrease and the current vehicle speed value are determined. When the difference between the vehicle speed value and the vehicle speed value is higher than the deceleration determination level determined from the maximum deceleration amount per unit time when the brake is applied, the failure determination means outputs a failure signal and maintains the current transmission gear position. How to control the transmission.