JPH0130029B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for controlling an automatic transmission, and more particularly to a method for protecting an occupant and an automatic transmission when a vehicle speed sensor that detects vehicle speed fails.

Conventional technology and its problems 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. 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. In this case, the speedometer needle continues to rotate due to inertia, so it takes time for the vehicle speed signal to reach zero. When the vehicle speed signal gradually decreases in this way, it is almost indistinguishable from applying the brakes, so there is a risk that downshifts will be performed as the vehicle speed signal decreases, causing the same problems as before. .

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.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to enable an automatic transmission system that can determine any type of failure of the vehicle speed sensor using one system of vehicle speed signals, and that can safely control the automatic transmission. The objective is to provide a method for controlling the machine.

Structure of the Invention In order to achieve the above object, the present invention calculates, when the vehicle speed signal decreases, the initial speed Vo immediately before the decrease and the current vehicle speed V in the middle of decrease, and also divides the vehicle speed into a plurality of zones in advance according to the vehicle speed. A deceleration determination level _αo corresponding to the above-mentioned initial speed Vo is determined from among the deceleration determination levels αo, and when the difference between the initial speed Vo and the current vehicle speed V is higher than the deceleration determination level _αo , the failure determination means outputs an abnormal signal. The current gear position is maintained. In other words, when the vehicle speed sensor fails and the vehicle speed signal decreases, the manner in which it decreases depends on the vehicle speed immediately before the decrease (initial speed Vo), so the vehicle speed deceleration determination level at the time of failure is divided into zones and memorized in advance. Then, among these deceleration determination levels, find the deceleration determination level α _o corresponding to the above initial speed Vo,
If the difference between the initial speed Vo and the current vehicle speed V (Vo - V) is greater than the deceleration judgment level α _o , it means that the vehicle is decelerating in a way that would normally not occur (the vehicle speed sensor is malfunctioning). Therefore, the current gear position is maintained to prevent sudden downshifting.

DESCRIPTION OF THE EMBODIMENTS FIG. 1 shows an example of a control device according to the present invention, in which 1 is a throttle opening sensor for detecting the throttle opening, and 2 is installed on either a speedometer or a transmission output shaft for detecting vehicle speed. These sensors 1 and 2 are similar to those mounted on general automobiles.

3 is a failure determination means, which receives a vehicle speed signal from the vehicle speed sensor 2 at regular intervals;
When the vehicle speed signal from the vehicle suddenly decreases, the difference Vo-V between the vehicle speed Vo immediately before starting deceleration (referred to as initial speed) and the vehicle speed V during deceleration (referred to as current vehicle speed) is determined. Further, as shown in FIG. 2, the failure determination means 3 stores the deceleration change rate at the time of failure divided into three zones depending on the initial speed, and the deceleration determination level α _o (n =1 to 3) are set. That is, when Vo> _V1 , the deceleration determination level is _α1 , when _V1 >Vo> _V2 , the deceleration determination level is _α2 , and when _V2 >Vo> _V3 , the deceleration determination level is _α3 . Then, these deceleration judgment levels α ₁ to _{α 3}
Then, the difference Vo-V between the initial speed Vo and the current vehicle speed V is compared, and if Vo-V > α ₁ to _{α 3} , deceleration is being performed which is normally impossible (vehicle speed sensor 2 is malfunctioning). Therefore, the failure determination means 3 outputs an abnormal signal, and outputs the current vehicle speed signal V as is when Vo-V<α ₁ to α ₃ .

Reference numeral 4 indicates manual determination of the gear position, and the throttle opening signal from the throttle opening sensor 1 and the signal from the failure determining means 3 are input. When the signal output from the failure determination means 3 is an abnormal signal (Vo-V>α ₁ to α ₃ ), the transmission gear position determining means 4
Regardless of the throttle opening signal, the current transmission gear position is maintained, and if it is not an abnormal signal (Vo-V<α ₁ to α ₃ ), the vehicle speed is adjusted according to the normal transmission operation. It outputs a speed change signal according to the throttle opening. The output signal from the transmission gear position determining means 4 operates a hydraulic circuit switching solenoid valve (not shown) of the transmission via the shift output means 5.

Next, the operation of the control device having the above configuration will be explained according to the flowchart shown in FIG. First, after starting, check the throttle opening and vehicle speed (Vo,
V) are sequentially detected and the initial velocity Vo and _V3 are compared.
If Vo<V ₃ , the initial speed is low, so no deceleration check is performed, and if Vo>V ₃ , the initial speed Vo is further reduced.
Compare with V ₁ . If Vo＞V ₁ , the initial velocity Vo
The difference between Vo-V and the current vehicle speed V is compared with the deceleration judgment level _α1 , and if Vo-V> _α1 , an abnormality is detected.
If Vo-V< _α1 , no deceleration check is performed.
In addition, in the case of Vo>V ₁ , the initial speed Vo and V ₂ are further compared, and in the case of Vo>V ₂ , the difference Vo−V between the initial speed Vo and the current vehicle speed V and the deceleration judgment level α ₂ are calculated. Compare,
If Vo−V＞α ₂ , an abnormality is detected, and if Vo−V＜α ₂
If so, no deceleration check is performed. In addition, Vo
If <V ₂ , the difference between the initial speed Vo and the current vehicle speed V Vo - V
and the deceleration determination level _α3 , and if Vo-V> _α3 , an abnormality is detected, and if Vo-V< _α3 , no deceleration check is performed.

After detecting whether or not there is an abnormality as described above, if no abnormality is detected, the gear position is determined and the gear is shifted according to a normal speed change operation. On the other hand, if an abnormality is detected, it means that the vehicle speed sensor 2 is malfunctioning, so a warning lamp or the like is flashed to warn the driver, and the malfunction determination means 3 outputs an abnormal signal to the gear position. A command is inputted to the determining means 4 to maintain (shift hold) the current transmission gear position. In other words, sudden downshifts are not performed, and engine revving and gear shift shock are prevented.

Note that if you stop the vehicle while maintaining the current gear position as described above, it will be difficult to start again, so release the shift hold and gradually downshift until the vehicle comes to a stop. It is necessary to control the For this purpose, for example, as shown in FIG. 1, the engine rotation speed N detected by the engine rotation speed sensor 6 is input to the failure determination means 3, and this engine rotation speed N is compared with a preset reference value Ns. By doing so, it can be determined whether the vehicle is traveling at high speed or not. That is, after performing a shift hold, the engine speed N is detected as shown by A in FIGS. 3 and 4, and N
When >Ns, the vehicle speed is high, so shift hold is continued; when N<Ns, it means the vehicle speed has become low enough, so release shift hold and shift to 1st gear as usual. All you have to do is go down. As the above standard value Ns,
Engine speed at idling, AT
The engine speed when the converter stalls can be taken.

Furthermore, instead of the engine speed N, the determination can be made based on the negative pressure in the intake pipe of the engine. That is, as shown in FIG. 1, the intake pipe negative pressure signal P from the engine intake pipe negative pressure sensor 7 is input to the failure determining means 3 and compared with a reference value Ps stored in the failure determining means 3 in advance. This reference value Ps can be, for example, the intake pipe negative pressure when the AT converter stalls. And P
> In the case of Ps, shift hold is continued,
If P<Ps, shift hold may be released.

In the above embodiment, the 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 current vehicle speed V is zero, Vo~V naturally becomes greater than _αo , 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 kinds of failures of the vehicle speed sensor 2.

Effects of the Invention As is clear from the above explanation, according to the present invention, when the vehicle speed sensor fails while driving, the failure of the vehicle speed sensor is determined based on the manner in which the vehicle speed signal decreases.
Since it prevents sudden downshifts, engine revving and gear shift shock can be prevented. especially,
When the vehicle speed sensor fails, the way the vehicle speed signal decreases depends on the initial speed, so in the conventional method it was not possible to distinguish between the case where the vehicle speed sensor failed and the case where sudden braking was applied, but with the present invention, The deceleration judgment level is divided into zones depending on the initial speed,
Since a deceleration determination level is set for each zone and compared with the difference between the initial speed and the current vehicle speed, failure of the vehicle speed sensor can be determined without fail. 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 drawings]

FIG. 1 is a block diagram of a control device according to the present invention, FIG. 2 is a diagram showing a decreasing change in a vehicle speed signal when a vehicle speed sensor fails, and FIG. 3 is a flowchart showing the operation of the device of the present invention. FIG. 4 is a flowchart added to FIG. 3. 1...Throttle opening sensor, 2...Vehicle speed sensor, 3...Failure determination means, 4...Transmission gear position determination means.

Claims (1)

[Claims] 1. In an automatic transmission that automatically controls the speed ratio of a transmission gear based on a throttle opening signal and a vehicle speed signal, when the vehicle speed signal decreases, find the initial speed Vo immediately before the decrease and the current vehicle speed V in the middle of decreasing. At the same time, the deceleration determination level α _o corresponding to the above initial speed Vo is determined from among the deceleration determination levels divided into a plurality of zones in advance according to the vehicle speed, and the initial speed Vo and the current vehicle speed V are determined.
A control method for an automatic transmission, wherein the failure determining means outputs an abnormal signal to maintain the current transmission gear position when the difference between the two _and