JPH02297068A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To detect an unclear fault state by providing a second coil wound round on a circular core adjacently to a first coil and a test signal transmitting circuit connected to an input part of a second coil. CONSTITUTION:For instance, in the case of detecting a fault of an acceleration sensor 1, first of all, a test signal is inputted to an input part of a second coil 6 from a test signal transmitting circuit 19. This test signal is a sine wave or a pulse wave. Subsequently, the test signal inputted to the coil 6 is transferred to a first coil 5 by a mutual induction. Also, when the test signal is inputted, the coil 6 receives force by an action of a ferromagnetic field formed by a magnet 2 and a pendulum 7 is displaced. When the test signal is inputted to the coil 6, if the coil 5 and the displaced state of the pendulum 7 are all normal, a signal corresponding to the test signal is all outputted from the coil 5. That is, by comparing the circuit 19 and the signal of each output part of the coil 5 with the circuit 19, a fault of the sensor 1 can be detected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a failure diagnosis technique for an acceleration sensor using an inductive pickup, and particularly to an acceleration sensor in which a test coil is installed in addition to an acceleration detection coil. Regarding.

[Prior Art] Conventionally, a so-called servo accelerometer disclosed in Japanese Patent Application Laid-Open No. 60233565, for example, has been proposed as an acceleration sensor using a conductive pickup, that is, a coil.

This type of servo accelerometer consists of a pendulum that displaces when subjected to acceleration, a detector that detects the amount of displacement of this pendulum, such as a photointerrupter, and a feedback circuit that returns the pendulum to a predetermined position using the output of this detector. and was configured to detect acceleration based on the output of the feedback circuit.

[Problems to be Solved by the Invention] However, although the above-mentioned types of acceleration sensors are inexpensive, they have many mechanical configurations and are prone to failure. In particular, when the coil gets caught on something and the movement of the coil and pendulum is obstructed, or when a failure occurs in the feeder circuit, etc.
It has developed that the output of the feedback circuit may appear normal and cause an unspecified fault.

It is difficult to determine such a failure based on the state of the output signal, and there is a possibility that the failure may not be discovered.

[Means for Solving the Problems] The present invention has been made by focusing on the above-mentioned problems, and is intended to reliably detect ambiguous failures caused by coil snags, feedback circuit failures, etc. It is intended for this purpose.

As a means for that purpose, we use a magnet that forms a strong magnetic field,
The acceleration sensor includes a first coil interposed in the strong magnetic field and a pendulum fixed to the first coil, and detects acceleration applied to the pendulum based on an output signal of the first coil. a second coil wound on the core of the mouth in close proximity to the second coil; a test signal generating circuit connected to the input section of the second coil; and a test signal connected to the test signal generating circuit and the output section of the first coil. The present invention provides an acceleration sensor characterized by comprising a receiving circuit.

[Function] The acceleration sensor including the above-mentioned means can detect a failure by the following function.

For example, when detecting a failure in the acceleration sensor, a test signal is first input from the test signal generation circuit to the input section of the second coil.

The test signal is a sine wave or a pulse wave.

A test signal input to the second coil is transmitted to the first coil by mutual induction. Further, when a test signal is input, the second coil receives a force due to the action of a strong magnetic field formed by the magnet, and displaces the pendulum. When a test signal is input to the second coil, if the displacement states of the first coil and the pendulum are all normal, all signals corresponding to the test signal are output from the first film.

That is, by comparing the signals of the test signal transmitting circuit and each output section of the first coil using the test signal receiving circuit, it is possible to detect a failure of the acceleration sensor.

[Embodiments] The attached drawings are drawings showing preferred embodiments of the present invention.

The acceleration sensor l shown in this embodiment is mounted on a vehicle and is exemplified as a sensor that detects vertical acceleration applied to the vehicle body, and its output is used to control the hardness of the suspension according to the unevenness of the road surface. Connected to suspension control device, etc.

FIG. 1 is an exploded perspective view showing only the main parts with the case etc. omitted.

In the figure, 2 is a magnet, and 3 is the magnet 2.
It is a ferromagnetic yoke that fixes the

Further, 4 is a bobbin that is fitted into the gap A formed between the magnet 2 and the yoke 3 so as to be able to swing freely.

The bobbin 4 is wound with a first coil 5 and a second coil 6,
It is fixed to the pendulum 7.

The pendulum 7 is, for example, a molded plastic product, and has a shutter 8 integrally molded on its free end.

Further, the support end side of the pendulum 7 has a thickness of, for example, 25 to 50 [
A holding plate 1 holds a film 9 made of polyimide resin of about μ■
Fixed by 0.

The film 9 is further fixed to the holder 12 by a holding plate 11.

Reference numeral 13 denotes a board, on which an element 14 such as an IC is mounted, and has an insertion hole 15 through which the shutter 8 is swingably inserted.

A photointerrupter 16 is attached to the location where the insertion hole 15 is formed. The photo ink converter 16 is composed of a light emitting diode (LED) 17 and a photo diode 18 as a pair, and the optical path is opened and closed by the shutter 8.

Although not shown in FIG. 1, each of the above-mentioned components is housed in an opaque case.

Next, an electric circuit diagram of the acceleration sensor 1 according to this invention will be explained using FIG. 2.

In FIG. 2, 19 is a test signal transmitting circuit connected to the second coil 6, and 20 is a test signal receiving circuit connected to the test signal transmitting circuit 19 and the first coil 5.

The test signal transmitting circuit 19 is a circuit that transmits a test signal to the second coil 6 in response to a control signal from the microcomputer 21, and even if the resistance value of the second coil 6 varies depending on the temperature, the magnetomotive force does not fluctuate. It is a temperature compensated circuit. That is, the test signal generating circuit 19
Regardless of variations in the resistance value of the coil 6, a test signal of the same current level is always output.

The test signal is, for example, a sine wave of about 100 Hz or a trigger pulse signal. When the vehicle is stopped, such as when the ignition switch 22 is operated or when the parking brake 23 is operated, the test signal is generated, for example, after several seconds in response to the operation of the operated switch.
Output between c.

The test signal receiving circuit 20 is a circuit for diagnosing a failure of the acceleration sensor l by comparing the human power signals from the test signal transmitting circuit 19 and the first coil 5, and is composed of a comparator 20a and resistors 20b to 20e. There is. Then, resistors 20b to 2 are connected so that when the acceleration sensor l is normal, the levels of the B point and the 0 point of both input parts of the comparator 20a of the test signal receiving circuit 20 are almost equal.
The constant 0e, the turns ratio and polarity of the first coil 5 and second coil 6, etc. are set in advance.

Next, 24 is an output circuit connected to the output section of the microcomputer 21, and is a circuit connected to an alarm device, a suspension control device, etc. that notifies a failure of the acceleration sensor 1. Further, 25 is an amplifier connected between the photointerrupter 16 and the first coil 5, and the level is determined according to the amount of interruption of the optical path between the light emitting diode (LED) 17 and the photodiode 18 of the photointerrupter 16 by the shutter 8. This is a circuit that energizes the first coil 5 with an excitation current of .

Next, the operation of the embodiment configured as described above will be explained.

For example, before power is supplied to the acceleration sensor 1, no excitation current is applied to either the first coil 5 or the second coil 6, and the bobbin 4 around which the first and second coils 5 and 6 are wound is Due to its own weight, the pendulum 7 falls into the deep part of the gap A formed between the magnet 2 and the yoke 3.

Next, when the ignition switch 22 is turned on, power is supplied to each part of the circuit of the acceleration sensor 1, the microcomputer 21 is initialized, and a fault diagnosis program for the acceleration sensor 1 is subsequently executed.

The failure diagnosis mode is a mode in which the test signal transmitting circuit 19 is operated for, for example, several 1 ieC, a signal from the test signal receiving circuit 20 during that period is input, and failure diagnosis is performed based on the state of the signal.

Now, as mentioned above, when the even switch 22 is turned on, the photo interrupter 16 and the amplifier 25 are turned on.
Power is supplied to the first coil 5, etc., and an excitation current is applied to the first coil 5.

When an excitation current is applied to the first coil 5, the first coil 5 receives a force from the strong magnetic field formed by the magnet 2 and levitates, and the pendulum 7 is lifted.

When the pendulum 7 is lifted, the shutter 8 also moves upward and blocks the optical path of the photointerrupter 16.

When the optical path is blocked by the shutter 8, the output of the amplifier 25 decreases and the excitation current of the first coil 5 decreases.

Finally, the pendulum 7 is floated to a position where the force exerted by the first film 5 and the weight of the pendulum 7 are balanced and comes to rest.

Now, when the failure diagnosis mode by the microcomputer 21 is started, the excitation current of the second coil 6 is output from the test signal generating circuit 19 as a test signal. The second coil 6 receives a force from the strong magnetic field of the magnet 2 when the excitation current is applied, and applies an external force to the pendulum 7.

The pendulum 7 is displaced by the force received from the second coil 6, and changes the amount of interruption of the optical path of the photointerrupter 16 by the shutter 8.

Therefore, the excitation current of the first coil 5 also changes, and when the acceleration sensor 1 is normal, signals with substantially the same waveform and the same level are input to the B point and the 0 point of the test signal receiving circuit 20.

Therefore, the comparator 20a manually outputs a signal of, for example, O'' level indicating normality to the microcomputer 21.

Next, a case will be described in which, for example, an unspecified failure occurs such that the bobbin 4 is caught by the magnet 2 or the yoke 3 due to deformation of the bobbin 4, and the swinging motion of the pendulum 7 is no longer smooth.

As above, when the failure diagnosis mode is started, the second coil 6
An excitation current is applied to the second coil 6, and the second coil 6 receives a force from the strong magnetic field of the magnet 2.

However, as mentioned above, due to the deformation of the bobbin 4, the pendulum 7
If the oscillating motion is not performed smoothly, the pendulum 7 will not move in proportion to the excitation current of the second coil 6, and the levels at point B and point 0 of the test signal receiving circuit 20 will eventually become inconsistent.

Therefore, the comparator 20a indicates an abnormality, for example, "1".
A level signal is input to the microcomputer 21.

Immediately after the ignition switch 22 is turned on, the microcomputer 21 activates the test signal generation circuit 19 for a predetermined period of time.
and confirm the state of the signal input from the test signal receiving circuit 20 during that time. When it is determined that a signal indicating an abnormality has been input from the test signal receiving circuit 20, the microcomputer 21 sets a flag indicating that the acceleration sensor l is abnormal and outputs an alarm signal to the output circuit 24.

Note that this invention is not limited to the above-described embodiment; for example, the switch for obtaining the timing for outputting the test signal from the test signal generating circuit 19 may be an Igni).
It may be a switch that is operated while the vehicle is stopped, such as a brake switch or a parking brake switch (it may also be a manual switch).

[Effects of the Invention] Since the present invention has the above-described configuration and operation, it is possible to reliably detect an unclear failure state that is difficult to determine as a failure by looking at it, and also achieve the above-described effects. This provides an excellent effect in that a fault condition can be automatically detected even when the vehicle is stopped, and the fault can be detected more accurately in a state where there is no vibration of the vehicle body.

Great brake.

that's all

Claims (1)

[Claims] An acceleration sensor comprising a magnet that forms a strong magnetic field, a first coil interposed in the strong magnetic field, and a pendulum fixed to the first coil, and detects acceleration applied to the pendulum using an output signal of the first coil. a second coil wound on a circular core close to the first coil;
An acceleration sensor comprising: a test signal transmitting circuit connected to an input section of the second coil; and a test signal receiving circuit connected to the test signal transmitting circuit and an output section of the first coil.