JP3343878B2 - Failure detection device for vehicle acceleration detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for mounting a small acceleration sensor integrally with an electronic circuit for processing an output signal of the acceleration sensor. The present invention relates to an improvement for reducing the influence of gravitational acceleration generated on an acceleration sensor. The present invention is used as a device mounted on an automobile. Although the present invention has been developed as an acceleration detection circuit that serves as a control input of a slope start assist device mounted on an automobile, it can be widely used for other purposes.

[0002]

2. Description of the Related Art The technology of equipping a middle- or large-sized vehicle with a slope start assist device has become widespread. The hill start assist device is where the driver needs to delicately coordinate the timing of the clutch operation and the accelerator operation with the brake release operation when the vehicle starts from a state where the vehicle stops on the hill. , An auxiliary control device used to reduce the burden of this operation. That is, when the vehicle stops while the brake pedal is depressed, the electronic device of the slope start assist device detects this, and maintains the pressure of the brake cylinder even when the brake pedal is released. Therefore, when the driver starts on a slope,
After stepping on the clutch pedal and engaging the gear, even if you release your foot from the brake pedal, you do not have to worry about the car slipping down the slope, making driving much easier.

[0003] Such a slope start assist device is mounted on a practical vehicle and has been well received, and various improvements have been made. In particular, it has rapidly become widespread in freight vehicles in which driving conditions must be changed depending on the amount of cargo. The hill start assist device is used not only when starting on a steep hill but also in driving situations where the vehicle repeatedly starts and stops when driving on a congested road on a flat ground. Was reduced.

With such improvements, it has been considered to use an acceleration sensor for detecting the acceleration / deceleration of the vehicle as a sensor input in order to more accurately determine that the vehicle is in a stopped state (Japanese Patent Application No. 7-213,197). 40811). And
An acceleration sensor will be attached to the body of the car.

In recent years, small components have been developed as acceleration sensors. For example, a small plate-shaped weight is supported by a leaf spring inside a small plate-shaped component of about 20 mm x 15 mm x 3 mm, and the position of the weight is detected by a slight change in the capacitance between both sides. And the like. This plate-shaped acceleration sensor detects acceleration in a direction perpendicular to the plate.

Unlike the conventional acceleration sensor, such an acceleration sensor does not need to be individually mounted on the body of an automobile, but is integrated inside an apparatus integrally with an electronic circuit for processing an output signal of the acceleration sensor. It is possible to implement. In particular, in the case of a hill start assist device, the device can be integrally mounted with an electronic device (computer device) that performs control, and can be configured as a small lunch box or a smaller device as a whole. Such a device can be mounted, for example, on the ceiling of the driver's seat of an automobile, near the driver's rearview mirror, or inside the dashboard.

The inventor has already filed a patent application for an apparatus having such a configuration (Japanese Patent Application No. 8-130249).

[0008]

The inventor of the present invention mounted this device on an automobile and repeated tests to analyze the causes of failures. As a result, it was found that there were three factors.
One is that the output of the acceleration sensor is fixed to the upper limit (5V), the other is the one that is fixed to the lower limit (0V), and an intermediate value (in this case, the fixed value Is not fixed).

A failure fixed at the upper limit value is caused by a short circuit or the like, and almost always reaches the same voltage as the supply voltage. Further, in the case of a failure that is fixed to the lower limit value, disconnection or the like is considered, and the voltage is almost 0 in most cases.

For this reason, the voltage range used in the control is limited to 5% to 95% of the output voltage of the acceleration sensor, and the control logic is configured to determine that the voltage is abnormal in the other range. It is to be detected.

On the other hand, a fault that is fixed to a certain voltage in the control region occurs when the internal weight is in a stopped state and cannot be detected by the above-described fault determination. If the detected output is used for a slope start assist device, inappropriate control will be performed.

The present invention has been made in such a background, and when an output signal of an acceleration sensor is abnormal, an alarm is issued to control the acceleration sensor so as not to use the abnormal output signal. Aim. An object of the present invention is to provide an acceleration detection circuit which is small and inexpensive and has a protection circuit against abnormal output. SUMMARY OF THE INVENTION An object of the present invention is to provide a small and inexpensive and highly accurate control unit for a slope start assist device.

[0013]

The present invention is characterized in that the occurrence of an abnormality is detected by the presence or absence of a change in the output of the acceleration sensor caused by the vibration of the vehicle body.

That is, according to the present invention, in a fault detecting device for a vehicle acceleration detecting circuit in which an acceleration sensor and an electronic circuit for processing an output signal of the acceleration sensor are mounted in one housing, the vehicle has a vehicle speed V The traveling detection means for detecting that the vehicle is traveling as described above, and the acceleration minimum value (α) which is the same as the acceleration maximum value (α) appearing in the output signal of the acceleration sensor within time t when the traveling detection means has a detection output. means for adding the difference (α−β) to the difference (α−β) n times, and the added value (Σ
Means for sending an abnormal alarm when (α-β)) does not exceed the predetermined value (k).

Means for setting the time t at regular intervals T, wherein the running detecting means detects that the vehicle is running at a vehicle speed V or higher and that the transmission is set to the running position. It is desirable to include means for doing so.

When the vehicle speed is equal to or higher than a certain value (for example, 50 km / s), the vehicle body is always shaken, and the output of the acceleration sensor fluctuates in accordance with the shake.
If the weight of the acceleration sensor sticks for some reason, the output will not fluctuate, and the output will show a constant value for a long time. Therefore, when the vehicle speed is equal to or higher than a certain value, a certain time t is separated and a difference always occurs between the maximum value (α) and the minimum value (β) of the acceleration sensor output during that time period. Therefore, when this difference appears on average or more, it is assumed that the acceleration sensor is operating normally. Conversely, the maximum value (α) and the minimum value (β)
It is considered that the weight is fixed when the difference between the two has almost disappeared.

As described above, since the abnormality of the acceleration sensor itself can be detected, it is possible to prevent the control from being performed in accordance with an inappropriate detection signal output from the abnormal state, and the traveling safety of the vehicle can be prevented. Properties can be further enhanced. In practicing the present invention, existing hardware can be used, and the present invention can be implemented only by changing software, so that the configuration can be made small and inexpensive.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

[0019]

Next, an embodiment of the present invention will be described with reference to the drawings. The present embodiment will be described on the assumption that the acceleration detection circuit is mounted on the slope start assist device. FIG. 1 is a block diagram showing a configuration of a main part of a slope start assist device according to an embodiment of the present invention.

The hill start assist device according to the embodiment of the present invention is provided with an acceleration sensor 1 and an acceleration detection circuit 2 in which an electronic circuit for processing an output signal of the acceleration sensor 1 is mounted in one case. Further, a vehicle speed sensor 3 for detecting that the vehicle is traveling at a vehicle speed V or higher, a clutch / stroke sensor 4 for detecting a stroke of a clutch pedal, and a transmission in a neutral position are provided as travel detection means. A neutral switch 5 indicating that
A brake sensor 6 for detecting that a brake pedal has been operated, a control valve 7 for maintaining a brake pressure in accordance with a control signal even when a brake pedal is released, and an output of each of the above sensors and switches. A program control circuit 9 including a means for transmitting a control signal and a failure detection device 8 for detecting a failure based on the output of the acceleration sensor 1
And an alarm device 10 that generates an alarm in accordance with an alarm signal from the failure detection device 8. An alarm buzzer 10a and an alarm lamp 10b are connected to the alarm device 10.

Further, as a feature of the present invention, when the detection output from the vehicle speed sensor 3 is equal to or higher than V, the failure detection device 8 calculates the maximum acceleration value (α) that appears in the output signal of the acceleration sensor 1 within the time t. Similarly, the difference from the minimum acceleration value (β) (α-
a means for adding β) n times, a means for setting the time t for each fixed period T, and a means for adding the value (Σ (α-β)) to a predetermined value (k).
Means for sending out an abnormal alarm when not exceeding the threshold.

FIG. 2 is a perspective view showing a configuration example of an acceleration detecting circuit according to the embodiment of the present invention, and FIG. 3 is a partial sectional view in the direction of arrow A in FIG. 2 showing an attached state of the acceleration sensor according to the embodiment of the present invention. .

The acceleration detection circuit 2 according to the present embodiment
It is mounted in the case 20 together with the operation unit 26 and the acceleration sensor 1. The operation unit 26 is provided with a main switch 21, a display 22, a release adjustment switch 23, and an initial adjustment switch 24. The main switch 21 is used to open and close the power supply by operation. The main switch 21 is turned on when the switch knob is raised, and is turned off when the switch knob is lowered. The display 22 is a 7-segment numeric display with a decimal point 25, and a number is displayed while the release adjustment switch 23 and the initial adjustment switch 24 are operated.

The acceleration sensor 1 is fixed to a bent portion 27 formed on a metal case 20. The bent portion 27 can be adjusted by changing the angle of bending as shown in FIG. 3, and normally, the gravitational acceleration applied to the acceleration sensor 1 when the case 20 is attached to the detection target is small. Is set to The electronic circuit for processing the output signal includes a unit for setting the influence of the acceleration of the small gravity detected by the acceleration sensor 1 to zero. The case 20 is mounted on the ceiling of the driver's seat, near the rearview mirror of the driver's seat, or inside the dashboard.

FIG. 4 is an exploded perspective view for explaining the structure of a main part of the acceleration sensor used in the embodiment of the present invention, and FIG. 5 is an assembled state of the acceleration sensor shown in FIG. 4 used in the embodiment of the present invention. 6A is a plan view showing the external shape of the acceleration sensor used in the embodiment of the present invention, and FIG. 6B is a side view thereof.

In the acceleration sensor 1, a first frame 11 formed of an insulator is sandwiched between a second frame 12 and a third frame 13 formed of an insulator. The first frame 11 has a built-in weight 15 supported by a leaf spring 14, and movable electrodes are formed on both surfaces of the weight 15. Further, fixed electrodes 16 are provided at positions corresponding to the movable electrodes of the second frame 12 and the third frame 13, and the fixed electrodes 16 are formed between both surfaces of the weight 15 and the second frame 12 and the third frame 13. A space is provided between each. This acceleration sensor is sensitive to acceleration in the direction of the arrow shown in FIG.

An acceleration sensor of this type is already commercially available as a capacitance type sensor, for example, as shown in FIG. 6, having a plurality of terminals 17 on the outer periphery and a mounting bracket 18 on the rear surface. Can be

FIG. 7 is a diagram for explaining the detection principle of the acceleration sensor according to the embodiment of the present invention. When the vehicle starts or stops or is on a slope, the weight (movable electrode) 15 moves in the direction of the arrow, and the gap d between the weight (movable electrode) 15 and the fixed electrode 16 changes. The change in the gap d changes the dielectric constant. By taking this change in the dielectric constant as an electric signal and performing the processing, a minute acceleration of 1% of the heavy acceleration can be detected.

Next, the operation of the embodiment of the present invention configured as described above will be described. FIG. 8 is a flowchart showing a flow of the operation in the embodiment of the present invention.

The failure detection device 8 provided in the program control circuit 9 takes in the output of the vehicle speed sensor 3 and determines whether or not the vehicle speed has exceeded the determination start speed v _S. Acceleration sensor 1
Since the higher the traveling speed of the vehicle, the higher the output, the higher the speed, the lower the judgment value, the higher the normal speed in order to prevent erroneous detection.

If the vehicle speed is equal to or higher than the determination start speed v _S , the output of the clutch stroke sensor 4 and the output of the neutral switch 5 are also taken in to determine whether the vehicle is running. Is in a gear-in state and the vehicle is in a running state. If the vehicle is in a running state, a predetermined time (t) is set for each predetermined period (T), and the output of the acceleration sensor 1 is captured over the predetermined time (t). The difference (α−β) between the maximum acceleration value (α) and the minimum acceleration value (β) appearing in the acquired output signal of the acceleration sensor 1 is added n times at regular intervals (T).

Next, it is determined whether or not the added value Σ (α−β) has exceeded a predetermined value k. And sends an abnormal alarm signal to the alarm device 10. This is based on the idea that if the vehicle speed is equal to or higher than a certain value, shaking or vibration always occurs in the vehicle body, and if the acceleration sensor 1 is normal, the output always changes.

For example, as shown in FIG. 9, if the weight 15 of the acceleration sensor 1 is fixed to one of the fixed electrodes 16 for some reason, the output is substantially constant for a long time as long as the fixed state is continued. Indicates a value. Therefore, if it is detected that there is almost no difference between the maximum value (α) and the minimum value (β) of the output of the acceleration sensor 1 within a certain period of time, the output during that period is shown as a constant value, indicating an abnormal state. At the same time.

The alarm device 10, which has received the abnormality alarm signal, issues an alarm from the alarm buzzer 10a and / or the alarm lamp 10b, and reports that it is in an abnormal state.

The above-mentioned abnormality warning signal is taken into the slope start assist device as an operation prohibition signal, and the operation of the slope start assist device can be prohibited while the alarm signal is being transmitted. Thus, it is possible to automatically prevent the slope start assist device from performing an undesired operation due to the abnormal output of the acceleration sensor.

[0036]

As described above, according to the present invention, when the weight of the acceleration sensor is stuck for some reason, the output does not fluctuate, so that an abnormality can be detected. Can be controlled so as not to use the abnormal output signal. As a result, erroneous control can be prevented from being performed according to the abnormal output, and traveling safety can be further improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a slope start assist device according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration example of an acceleration detection circuit according to the embodiment of the present invention.

FIG. 3 is a partial cross-sectional view in the direction of arrow A in FIG. 2 showing an attached state of the acceleration sensor according to the embodiment of the present invention.

FIG. 4 is an exploded perspective view showing a structure of a main part of the acceleration sensor used in the embodiment of the present invention.

FIG. 5 shows an acceleration sensor used in the embodiment of the present invention.
BB sectional drawing shown in FIG.

6A is a plan view showing an external shape of an acceleration sensor used in an embodiment of the present invention, and FIG. 6B is a side view thereof.

FIG. 7 is a view for explaining the detection principle of the acceleration sensor in the embodiment of the present invention.

FIG. 8 is a flowchart showing a flow of an operation in the embodiment of the present invention.

FIG. 9 is a sectional view showing a state in which the weight of the acceleration sensor according to the embodiment of the present invention is fixed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Acceleration sensor 2 Acceleration detection circuit 3 Vehicle speed sensor 4 Clutch stroke sensor 5 Neutral switch 6 Brake sensor 7 Control valve 8 Failure detection device 9 Program control circuit 10 Alarm device 10a Alarm buzzer 10b Alarm lamp 11 First frame 12 second frame 13 third frame 14 leaf spring 15 weight 16 fixed electrode 17 terminal 18 mounting bracket 20 case 21 main switch 22 indicator 23 release adjustment switch 24 initial adjustment switch 25 decimal point 26 operation unit 27 bending Department

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01P 21/00 G01P 15/00-15/18 G01D 1/18 G01D 5/12

Claims (3)

(57) [Claims] An acceleration sensor and an electronic circuit for processing an output signal of the acceleration sensor are mounted on a single housing. A failure detection device for an acceleration detection circuit for a vehicle, wherein the vehicle is traveling at a vehicle speed V or higher. And a minimum acceleration value (β) which is the same as the maximum acceleration value (α) appearing in the output signal of the acceleration sensor within a time t when the detection signal is detected by the travel detection unit. Difference (α-β)
And a means for sending an abnormality alarm when the added value (Σ (α−β)) does not exceed a predetermined value (k). Failure detection device. 2. The failure detection device for an acceleration detection circuit for a vehicle according to claim 1, further comprising means for setting the time t at every predetermined period T. 3. The vehicle acceleration detection device according to claim 1, wherein said traveling detection means includes means for detecting that the vehicle is traveling at a vehicle speed V or higher and that a transmission is set to a traveling position. Circuit failure detection device.