JPS62166106A - Device for detecting displacement of suspension system for vehicle - Google Patents

Abstract

PURPOSE:To simplify the constitution of the captioned device by disposing electromagnetic coils respectively on the car body and axle sides of a suspension system to supply cyclically variable exciting current to one coil while induced voltage generated in the other electromagnetic coil is detected. CONSTITUTION:Exciting current of sine wave is supplied from an exciting circuit to an electromagnetic coil 1A. Thus, the exciting coil 1A forms a alternating field to generate induced voltage V in an exciting coil 1B. This induced voltage V is determined by the mutual inductance M12 between change amount dI/dt in the exciting current and the exciting coils 1A, 1B, Since this mutual inductance M12 varies with the distance between the coils 1A, 1B, the distance between the coils 1A, 1B, i.e. the displacement of a suspension system can be detected by detecting the change in the induced voltage V accurately with a simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a displacement detection device for a vehicle suspension system.

[Prior Art] The above-mentioned suspension device is usually provided with a shock absorber and a spring member to prevent transmission of vibration input.

By the way, in recent years, the damping force of the shock absorber is made variable according to the unevenness of the road surface, or the spring force of the suspension device is changed to maintain a constant vehicle height regardless of the load. Therefore, in such applications, there is a need for a device that accurately detects the relative displacement between the body side and the axle side of the suspension device.

Various such detection devices have been proposed, for example,
No. 0-23334 discloses that a non-magnetic material is embedded in the piston rod of a shock absorber at intervals in the longitudinal direction,
It has been proposed to detect the relative displacement by using a magnetic sensor to detect the passage of the piston rod as it expands and contracts.

In addition, in Utility Model Application No. 60-62307, a detection spring is provided in series with a main spring attached to a shock absorber, and the above-mentioned relative displacement is detected by detecting the movement of a magnet placed between these springs with a magnetic sensing element. It is suggested that something be done.

[Problems to be solved by invention U] By the way, the above-mentioned proposal of Utility Model Application Publication No. 60-23334 requires special machining of the piston rod, and also has the problem that the absolute amount of displacement cannot be detected. There is.

In addition, in the proposed Utility Model Application Publication No. 60-62307, since a detection spring is provided, the effective displacement length of the piston rod may be restricted, or if the detection spring and main spring resonate, accurate displacement cannot be detected. The problem is that it can't be done.

In view of these problems, the present invention provides a displacement detection device for a vehicle suspension device that does not require machining of the piston rod of a shock absorber and does not impose restrictions on the effective displacement length of the piston rod, has a simple structure and is accurate. The purpose is to

[Means for Solving the Problems] To explain the configuration of the present invention with reference to FIG. 1, the vehicle suspension device 4 has one electromagnetic coil 1A on the body B side.
The other electromagnetic coil IB is provided on the axle A side that is relatively displaced with respect to the body B side. These electromagnetic coils IA and IB are positioned facing each other and are electromagnetically coupled.

The electromagnetic coil 1A is supplied with an excitation current that changes periodically from the excitation means 2. The induced voltage generated in the electromagnetic coil 1B is detected by the detection means 3.

[Function] When Pode B and axle A undergo relative displacement due to vibration input, etc.,
The mutual inductance between the electromagnetic coils 1A and 1B changes, and the induced voltage generated in the electromagnetic coil 1B changes.

By detecting the magnitude of this induced voltage, the relative displacement between the podium B side and the axle A side of the suspension device 4 can be accurately known.

[Effects] According to the displacement detection device of the present invention, there is no need to process the piston rod of the shock absorber as in the conventional device, and there is no restriction on the effective displacement length of the piston rod.

Furthermore, it can be easily installed in the suspension device without making major changes to its structure.

Furthermore, since displacement is detected by changing the mutual inductance of the electromagnetic coil, there are no mechanically moving parts, and problems such as wear do not occur, resulting in excellent reliability.

[Example] FIG. 1 shows a vehicle suspension system equipped with a displacement detection device according to the present invention. The figure shows a strut type suspension device having a shock absorber 4 with variable damping force, and the lower end of the cylinder 41 of the shock absorber 4 is connected to the axle
The upper end of the piston rod 42, which is fixed to the cylinder 41 and protrudes from the cylinder 41, is connected to the Pod B via a bearing 51 and vibration isolating rubber 52 attached to the outer circumference of the piston rod 42.

Further, spring receivers 43 and 44 are provided at the upper ends of each of the cylinder 41 and the piston rod 42, and the suspension spring 6 is disposed between them.

A piston 45 that moves IM within the cylinder 41 is fixed to the lower end of the piston rod 42, and the piston 45 has throttle holes 451 and 452 formed therein.

A portion of the piston rod 42 directly above the fixed portion of the piston 45 is a large-diameter cylindrical body, inside which a piezo stack 46 and a spool valve 47 are disposed facing each other with a pressure chamber 48 interposed therebetween.

The spool valve 47 is moved up and down as the piezo stack 46 expands and contracts, and opens and closes a liquid flow passage 49 formed in the piston rod 42 and communicating with the upper and lower liquid chambers C1D. Such a structure is known, and the damping force of the shock absorber 4 increases when the liquid flow passage 49 is closed.

Electromagnetic coils IA and 1B are provided at the upper ends of the spring receiver 43 and the cylinder 41, which face each other.

That is, the electromagnetic coil 1A is embedded in an insulating resin 11 fixed to the lower surface of the spring receiver 43, and is arranged around the piston rod 42 concentrically therewith.

On the other hand, the electromagnetic coil 1B is embedded in an insulating resin 12 fixed to the outer periphery of the upper end of the cylinder 41 so as to be concentric with the piston rod 42. The coil 1A is connected to an excitation circuit 2 which is also buried in the resin 11, and a lead wire 21 extends from the excitation circuit 2 to an external power source (circuit). The tip of the lead wire 21 is a connector 22. The electromagnetic coil 1B is connected to a detection circuit 3 embedded in a resin 12, and a lead wire 31 having a connector 32 at its tip extends from the detection circuit 3. Lead wire 31 leads to the damping force control device of the enclosure. Hey, number 7 in the diagram
is required with a rubber stopper.

The excitation circuit 2 outputs a sinusoidal excitation current, and the electromagnetic coil 1A receiving the excitation current forms an alternating magnetic field around the electromagnetic coil 1A, thereby generating an induced voltage in the electromagnetic coil 1B. The induced voltage V at this time is expressed by the following equation.

d■ Here, dI/dt is the amount of change in excitation current, and M12
is the mutual inductance between the electromagnetic coils 1A and 1B. As is clear from the above equation, the induced voltage V is proportional to the mutual inductance M12, and this mutual inductance M1□ is equal to both the coils 1A.

It changes depending on the distance between 1B. However, when the relative distance between the axle A and the body B changes due to vibration input, etc., and the shock absorber 4 expands and contracts, the mutual inductance between the electromagnetic coils 1A and 18 changes accordingly, and eventually occurs in the electromagnetic coil 1. Based on the magnitude of the induced voltage V, the relative displacement between the axle side and the body side of the shock absorber 4 can be detected. In this example, each of the electromagnetic coils 1A and 1B has a diameter of 70 m, a number of turns of 400,
The frequency of the excitation current was 1KH7.

An example of the excitation circuit 2 and the detection circuit 3 is shown in FIGS. 2 and 3. In FIG. 2, 21 is an operational amplifier, 22 is a transistor, and these together with a resistor and a capacitor constitute a sine wave generating circuit.

In Figure 3, 31.32.33.34.35.36
is an operational amplifier, 37 is a pair of transistors, and 38.39 is a diode. The operational amplifier 31 constitutes an amplifier, and the operational amplifier 32 constitutes a rectifier circuit including three diodes 38.

Thus, a DC detection voltage 1q corresponding to the amplitude of the induced voltage generated in the electromagnetic coil 1B is applied to the output side P1 of the operational amplifier 33. This is shown in FIG.

As can be seen from the figure, the detected voltage changes approximately exponentially with respect to the displacement of the suspension device.

The operational amplifiers 34 and 35 and the pair of transistors 37 constitute a logarithmic amplifier, and after the detection voltage is linearized by this, the voltage is adjusted by the operational amplifier 36, and a displacement detection signal approximately proportional to the displacement of the suspension device is sent to the terminal P2. is output as This is shown in FIG. The damping force control device learns the magnitude of the vibration input from the displacement detection signal and changes the damping force of the shock absorber 4.

In this manner, the displacement detection device of the present invention can accurately detect the absolute amount of displacement of the suspension device.

In particular, in this embodiment, since the pair of electromagnetic coils 1A11B are disposed concentrically and facing the piston rod 42, there is an advantage that displacement detection can be performed while the piston rod 42 is allowed to rotate freely.

The displacement detection device having the above structure can also be provided in a suspension device having a vehicle height adjustment function.

This is shown in FIG. In the figure, air is formed around a piston rod 42 that protrudes from a cylinder 41. The upper half of the air chamber 8 is constituted by a metal cylindrical wall 81, and the center of the top surface of the cylindrical wall 81 is fixed to the rod 42. The lower half of the air chamber 8 is a rolling diaphragm 8
2, and the center portion of the diaphragm 82 is fixed to the outer periphery of the upper end of the cylinder 41. Pressurized air is supplied to the air chamber 8 from a nipple 83 provided on the cylindrical wall 81, thereby changing the spring pressure of the air chamber 8 and maintaining the vehicle height constant regardless of the load.

In order to know the change in vehicle height in this case, that is, the expansion and contraction of the shock absorber 4, an electromagnetic coil IA is provided along the inner periphery of the cylindrical wall 81, and the cylinder 41 An electromagnetic coil 1B is provided on the outer periphery of the upper end.

These electromagnetic coils 1A and 1B are respectively connected to an excitation circuit 2 provided on the outside of the cylinder wall 81 and a detection circuit 3 provided on the outer periphery of the upper end of the cylinder 4.

FIG. 7 shows an example of an electromagnetic coil. In the installation structure shown in FIG. 1, water droplets and mud adhere to the surface of the resin 11.12 in which the electromagnetic coils 1A and 1B are embedded. Since these have conductivity, they have the effect of weakening the magnetic field formed by the electromagnetic coil 1A, and this causes errors in displacement detection due to adhesion of water droplets and the like. Therefore, in the electromagnetic coil 1 shown in FIG. 7, the ring-shaped bobbin 1 around which the winding 13 is wound
4 and the cover 15 are made of a non-magnetic conductive material, such as aluminum, 18-8 stainless steel, brass, copper, or conductive plastic, and the bobbin 14 and the winding 13
This is necessary by interposing an insulating material 16 between them. As the insulating material 16, an insulating film or an insulating coating film such as silicone or varnish is used.

According to such a structure, the electromagnetic coupling between the electromagnetic coils is slightly reduced, but the influence of adhesion of rainwater etc. can be suppressed to a small level.

The effect of this structure will be explained with reference to FIG.

Line A in the figure is a graph showing the relationship between displacement of the suspension device and detected voltage when a coil using a bobbin made of insulating material is used, and line B is a graph showing the relationship between the displacement of the suspension device and the detected voltage when the outer surface of the bobbin is wetted by rainwater. This indicates the detected voltage. In this case, the detected voltage decreases as shown in the figure. Line C is
This shows the displacement of the detected voltage when aluminum is used as the bobbin. Although the detected voltage is lower than A, there is no displacement of the detected voltage due to rainwater or the like. Note that instead of making the bobbin from a conductive material, the entire coil winding may be buried in an insulating resin, and the surface of the resin may be covered with aluminum foil or the like.

When the displacement detection device of the present invention is provided for each of the left and right front and rear wheels, the excitation circuit 2 and the detection circuit 3 can be shared as shown in FIG. That is, in the figure, the excitation circuit 2 excites four electromagnetic coils 1A simultaneously. Further, the detection circuit 3 includes an analog multiplexer 91, an A/D
It is composed of a converter 92 and a microprocessor 93, and the excitation circuit 2, multiplexer 91, and A/D converter 92 are operated in synchronization with the microcomputer 93.

The induced voltages obtained in the four electromagnetic coils 1B are sequentially switched by an analog multiplexer 91, converted into digital signals by an A/D converter 92, and processed by a microprocessor 93.

Here, the timing at which the induced voltage is taken into the A/D converter 92 is synchronized with the phase of the excitation current from the excitation circuit 2, so that the maximum value of the induced voltage is always taken in. The memory of the microprocessor 93 stores in advance the relationship between the maximum value of the induced voltage and the displacement of the suspension device, so that the displacement can be easily determined. Note that 94, 95, and 96 in the figure are output terminals of the microprocessor 93, which output the linearly sliced displacement output signal, or the vehicle height adjustment command signal, damping force control signal, etc. obtained by further processing this signal. Output.

According to this configuration, the four pairs of electromagnetic coils 1A, 1B
Even when @ is provided, the excitation circuit 2 and the detection circuit 3 can be shared, and the circuit configuration is simplified.

In particular, since the rectifier circuit and logarithmic amplifier in the detection circuit 3 as in the above-mentioned embodiments are unnecessary, the circuit can be simplified in this respect as well. Further, since suspension devices are generally made of magnetic metal, the induced voltage obtained in the electromagnetic coil 1B varies depending on the shape of the suspension device. This case can also be easily handled by changing the memory contents of the microprocessor 93.

In each of the above embodiments, the excitation current of the excitation circuit 2 is not limited to a sine wave, but may be a triangular wave, for example.

[Brief explanation of drawings]

1 to 5 show a first embodiment of the present invention, FIG. 1 is an overall sectional view of a suspension device equipped with a detection device of the present invention, FIG. 2 is a circuit diagram of an excitation circuit, and FIG. Figure 4 is a circuit diagram of the detection circuit, Figure 4 is a graph showing the relationship between displacement and detection voltage, Figure 5 is a graph showing the relationship between displacement and detection signal,
FIG. 6 shows a second embodiment of the present invention, and FIGS. 7 and 8 show a whole sectional view of a suspension device equipped with a detection device of the present invention, and FIG. FIG. 7 is a cross-sectional view of a half part of the electromagnetic coil, and FIG. 8 is a graph showing the relationship between displacement and detection voltage. is. 1.1A, 1B... Electromagnetic coil 13...
・Coil winding 14...Bobbin (S electrical material) 15...Cover (conductive material)] 6...Electrical insulating material 2...Excitation circuit 3. ...Detection circuit 4 ...Shock absorber 41 ...Cylinder 42 ...Piston rond 45 ...Piston 6 ...Suspension spring 8...
・Air chamber 91...Analog multiplexer 92...
...A/D converter 93...Microprocessor A...Axle B...Body 1st 2nd f, ', 4'J#jJγ Fig. 6 Figure 8

Claims (3)

[Claims] (1) One electromagnetic coil provided on the body side of the vehicle suspension device, and an electromagnetic coil provided opposite to the one electromagnetic coil on the axle side of the suspension device that is relatively displaced with respect to the body side. an excitation means for supplying a periodically changing excitation current to the one or the other electromagnetic coil, and an induction generated in the other or one of the electromagnetic coils in response to changes in the excitation current; A displacement detection device for a vehicle suspension system, comprising a detection means for detecting a voltage and determining a relative displacement between a body side and an axle side of the suspension system based on the detected induced voltage value. (2) Displacement of the vehicle suspension device according to claim 1, wherein the one and the other electromagnetic coils are provided so that their centers coincide with and surround the piston rod of a shock absorber provided in the suspension device. Detection device. (3) A displacement detection device for a vehicle suspension device according to claim 1, wherein the one and the other electromagnetic coils are covered with a non-magnetic conductive material via an electrical insulating material.