JP3063502B2 - Relative displacement detection sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relative displacement detecting sensor, and more particularly to a relative displacement detecting sensor for detecting a relative displacement by utilizing a magnetostriction phenomenon.

[0002]

2. Description of the Related Art Conventionally, there is a relative displacement amount detection sensor for detecting a relative displacement amount of an object using a magnetostriction phenomenon.

For example, Japanese Unexamined Patent Publication (Kokai) No. 61-112923 discloses a technique in which a current pulse is applied to a magnetostrictive wire to generate or reflect an ultrasonic wave at a magnetostrictive wire adjacent to a permanent magnet movable along the magnetostrictive wire. The relative displacement between the magnetostrictive wire and the permanent magnet is detected by measuring the propagation time of the ultrasonic wave to a specific portion of the magnetostrictive wire.

[0004]

When the above-mentioned relative displacement detection sensor is used for measuring the vehicle height, it is conceivable to dispose the detection sensor in a shock absorber. If the shock absorber has a mechanism for switching damping force, the magnetic field of the magnetostrictive wire of the detection sensor is affected by the magnetic field generated by the electromagnetic actuator while the electromagnetic actuator for switching damping force is acting, There is a problem that the relative displacement amount, that is, the vehicle height detection accuracy is reduced.

[0005] The present invention has been made in view of the above points,
An object of the present invention is to provide a relative displacement amount detection sensor that prevents a decrease in detection accuracy of a relative displacement amount by not using magnetic information of the relative displacement amount in calculation of the relative displacement amount when an electromagnetic actuator is operated.

[0006]

FIG. 1 shows the principle of the present invention.

[0007] The relative displacement amount detection sensor of the present invention has a
Move the absorber rod inside the filled absorber cylinder.
The piston arranged at one end moves and is attached to the piston.
And the other end of the absorber rod
Attenuation that can be varied by an electromagnetic actuator provided outside
Provided on the variable force shock absorber,
Detects the relative displacement between the rod and the absorber cylinder
You. The magnetic detection sensor M1 is provided in addition to the absorber rod.
The absolute , which is provided outside the end side and is relatively movable.
Magnetic information whose arrival time changes according to the relative displacement between the absorber rod and the absorber cylinder is detected.

The calculating means M2 calculates the relative displacement from the arrival time of the detected magnetic information.

The employment prohibition means M4 operates when the electromagnetic actuator M3 arranged near the magnetic detection sensor operates.
The detected magnetic information is used for calculating the relative displacement.
Absent.

[0010]

[0011]

According to the present invention, since the magnetic information of the relative displacement affected by the magnetic field generated by the electromagnetic actuator is not used in the calculation of the relative displacement, the detection accuracy of the relative displacement is prevented from lowering.

[0012]

FIG. 2 is a block diagram showing an embodiment of the sensor according to the present invention. In this embodiment, a relative displacement detection sensor is applied to a shock absorber of an air suspension as a vehicle height sensor.

In FIG. 1, an air chamber 14 for sealing high-pressure air is formed between the absorber cylinder 11 and the suspension tower 12. Since the absorber cylinder 11 moves up and down, the air chamber 14 and the absorber cylinder 1
1 is a diaphragm 15 made of a flexible resin.
Are connected by

The vehicle height is adjusted by the air pump 16 and the accumulator 18 by the air valve 16 provided on the side wall of the air chamber 14 under the control of the vehicle height controller 51 so that the vehicle height is set by the vehicle height setting switch 52. , By adjusting the amount of air in the air chamber 14. If the current vehicle height position is lower than the appropriate vehicle height position, the air in the accumulator 18, which has been increased in pressure by the air pump 17, is released from the air valve 16 to the air chamber 1.
The vehicle height is raised to an appropriate position by injecting the pressure into the inside 4 and increasing the pressure. Conversely, if the current vehicle height position is higher than the proper vehicle height position, the air valve 16 causes the air chamber 14 to move.
The air inside is discharged to lower the vehicle height to the appropriate vehicle height position. The above-described vehicle height control is executed by determining the vehicle height based on the detection signal of the vehicle height sensor, and the control is performed regardless of whether the vehicle is running or stopped.

The damping force control is performed by switching a variable orifice 21 provided in the piston 20.
Oil in the upper and lower chambers in the absorber cylinder 11 partitioned by the piston 20 moves through the variable orifice 21 as the absorber cylinder 11 moves up and down, thereby generating a damping force. Therefore, the diameter of the orifice is varied to increase or decrease the damping force.

The damping force switching mechanism includes an absorber rod 22
The diameter of the orifice is switched by rotating the control rod 23 disposed therein. For this purpose, a damping force switching actuator 27 as an electromagnetic actuator M3 including a magnet 25 and a solenoid 26 is disposed above the absorber rod 22. In the damping force control, the damping force control controller 31 drives the damping force switching actuator 27 so that an appropriate damping force is set by the damping force setting switch 30.

The damping force switching actuator 27 rotates a magnet 25 (fixed to the control rod 23), which is a central rotor of the actuator 27, by passing a current through a solenoid 26, which is a stator. Therefore, when the damping force is switched, a strong magnetic field is generated around the damping force switching actuator.

A ground line 35 is provided on the inner peripheral surface of the nonmagnetic absorber rod 22 with an insulating film interposed therebetween, and a magnetostrictive film 37 is further provided with an insulating film interposed therebetween. , The magnetostrictive film 37 is connected to the ground line 35.

Here, the current pulse generated by the current pulse generator 41 of the vehicle height detecting module 40 is supplied from the input terminal 42 to the magnetostrictive film 37. A local magnetic field in the circumferential direction of the magnetostrictive film 37 is formed by the current pulse, and the magnetic field in the circumferential direction moves downward in the axial direction with the conduction of the current downward in the axial direction of the absorber rod 22. Absorber cylinder 1
The magnet 45 disposed on the upper portion 1 forms a static magnetic field in the axial direction of the absorber rod 22, and the magnetic field in the circumferential direction due to the current pulse collides with this axial magnetic field, thereby synthesizing the magnetic field film 37 in a twisting direction. A magnetic field is formed.
The magnetostrictive material has a physical property that, when a magnetic field is applied, a strain is generated in a direction of a magnetic force line, and when a mechanical strain is applied, the material is magnetized in the strain direction. For this reason, mechanical distortion occurs in the magnetostrictive film 37 at the position where the magnet 45 is disposed, and the mechanical torsion propagates on the magnetostrictive film 37 in the vertical direction of the absorber rod 22 along with the magnetization of the magnetostrictive film 37, and the distortion detecting coil 46. To the set position. A starting force is generated in the distortion detection coil 46 as the magnetic detection sensor M1 due to the magnetization caused by the mechanical torsion of the magnetostrictive film 37, and this signal is transmitted to the vehicle height detection module 4
It is supplied to the distortion detection unit 48 within 0.

In the vehicle height detection module 40, the clock generator 49 generates a clock having a period T ₁ as shown in FIG. 3A and supplies it to the current pulse generator 41 and the SR flip-flop 50. The current pulse generator 41 generates a current pulse shown in FIG. 3B in synchronization with the rise of the clock. The distortion detection unit 48 includes a distortion detection coil 46
By comparing the output signal of FIG.
A distortion detection pulse as shown in (C) is generated and supplied to the flip-flop 50.

The flip-flop 50 is set at the rising edge of the clock, reset at the rising edge of the distortion detection pulse, generates the vehicle height detection signal shown in FIG. The pulse width T ₂ of the vehicle height detection signal is equal to the vehicle height, that is, the magnet 4 of the absorber rod 22.
5 is proportional to the relative displacement.

Here, since the distortion detecting coil 46 detects a weak magnetic field, a large magnetic field generated by the operation of the damping force switching actuator 27 near the distortion detecting coil 46 is erroneously detected. Therefore, it is necessary not to detect the vehicle height while the damping force switching actuator 27 is operating. Therefore, when switching the damping force, the damping force control controller 31 drives the damping force switching actuator, generates an actuator operation signal, and supplies it to the vehicle height controller 51.

Further, regardless of the type of the magnetostrictive material, since the propagation of torsional strain is extremely fast, the high level period (pulse width) of the strain detection pulse is shorter than the vehicle height calculation time in the vehicle height controller 51. Then, an interrupt is performed at the edge of the distortion detection pulse, and an interrupt routine having a short processing time is executed.

FIG. 4 shows a flowchart of a vehicle height calculation routine executed by the vehicle height controller 51. This routine is a part of the main routine, for example, 8 msec.
It is executed every time. In the figure, in step S10, it is determined whether or not the damping force is being switched by looking at the actuator operation signal supplied from the damping force controller 31. If the damping force is being changed, the interrupt prohibition flag is set in step S20 to prohibit the interrupt, and in step S30, the operation flag is set to 0.
To end the process. This is because it is impossible to determine whether the distortion detection pulse was obtained before or after the supply of the actuator operation signal after the previous vehicle height calculation processing, and there is a risk of erroneous detection. Steps S20 and S3
0 corresponds to the adoption prohibition means M4.

If it is determined in step S10 that the damping force is not being switched, then in step S40 the damping force controller 3
It is determined from the actuator operation signal from 1 whether or not the operation of the damping force switching actuator 27 has just finished.
If it is immediately after the operation is completed, the process proceeds to step S50, the interrupt prohibition flag is reset, the interrupt is permitted, and the process ends.

If it is not immediately after the end of the operation of the damping force switching actuator 27 in step S40, step S60
Is used to determine whether the operation flag is 1. If the operation flag is 0, the process is terminated as it is, but if the operation flag is 1, the process proceeds to step S70, in which the rising edge time is subtracted from the falling edge time stored in an interrupt routine to be described later. The pulse width T of the distortion detection pulse shown in FIG.
₂ calculates the, by the following expression in step S80, converts the pulse width T ₂ in vehicle height.

Vehicle height = k × v × T ₂ where v is a propagation speed (sound speed) of strain in the magnetic film, and k is a correction coefficient for performing temperature correction of v and the like. Step S above
70 and S80 correspond to the calculating means M2.

Further, in step S90, the operation flag is reset to 0, and the process is terminated.

FIG. 5 shows a flowchart of the interrupt routine. This interrupt routine is executed when the interrupt disable flag is reset and the interrupt is enabled at the rising or falling edge of the distortion detection pulse according to the value of the rising edge interrupt enable flag. That is, even in the interrupt enabled state, when the rising edge interrupt enable flag is 1, an interrupt is performed only at the rising edge, and when the rising edge interrupt enable flag is 0, the interrupt is performed only at the falling edge.

In FIG. 5, in step S100, it is determined whether the edge of the interrupt is rising or falling. In the case of the rising edge, the count value of the free running timer is written and stored in the RAM as the rising edge time in step S110. Next, in step S120, the rising edge interrupt permission flag is set to 0, and the process ends.

In the case of a falling edge in step S100, the count value of the free running timer is written and stored in the RAM as the falling edge time in step S130.
Next, in step S140, the operation flag is set to 1, and in step S150, the rising edge interrupt permission flag is set to 1, and the process ends.

The reason why the rising edge interrupt permission flag is inverted in steps S120 and S150 is that the rising edge and the falling edge are supplied alternately by the pulse of the distortion detection signal. Since the rising edge must always be supplied at first, the rising edge interrupt permission flag is initialized to 1 immediately after the engine is started.

As described above, the damping force switching actuator 2
7 is activated and the magnetic field affects the magnetostrictive film 37, the interrupt prohibition flag is set to prohibit the storing of the rising edge time and the falling edge time, and the calculation flag is reset to 0 to calculate the vehicle height. Then, immediately after the end of the operation of the damping force switching actuator 27, the interrupt prohibition flag is reset to store the rising edge time and the falling edge time, and the vehicle height is calculated using both the stored times. For this reason, erroneous detection of the vehicle height due to the influence of the magnetic field generated by the damping force switching actuator is prevented, and a decrease in detection accuracy can be prevented.

Instead of providing the magnetostrictive film 37 on the inner peripheral surface of the absorber rod 22 as shown in FIG. 2, the magnetostrictive film 37 is provided with an insulating film interposed on the outer peripheral surface of the conductive control rod 23 as shown in FIG. The outer peripheral surface of the magnetostrictive film 37 is insulated by an insulating film, and the magnetostrictive film 37 is electrically connected to the control rod 23 below the control rod 23.
The control rod 23 may be configured to be grounded. In FIG. 6, the same parts as those in FIG.

[0035]

As described above, according to the relative displacement detection sensor of the present invention, since the magnetic information of the relative displacement affected by the magnetic field generated by the electromagnetic actuator is not used in the calculation of the relative displacement, the relative displacement is not calculated. The detection accuracy of the displacement amount is prevented from lowering, and the detection accuracy is improved, which is extremely useful in practice.

[Brief description of the drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a configuration diagram of the sensor of the present invention.

FIG. 3 is a signal timing chart of each unit in FIG. 2;

FIG. 4 is a flowchart of a vehicle height calculation routine.

FIG. 5 is a flowchart of an interrupt routine.

FIG. 6 is a configuration diagram of a modified example of the sensor of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Absorber cylinder 20 Piston 21 Variable orifice 22 Absorber rod 23 Control rod 27 Damping force switching actuator 31 Damping force control controller 37 Magnetostrictive film 40 Vehicle height detection module 41 Current pulse generator 48 Strain detector 51 Vehicle height controller M1 Magnetic detection sensor M2 calculation means M3 electromagnetic actuator M4 adoption prohibition means

Claims (1)

(57) [Claims] 1. Inside an absorber cylinder filled with a fluid
The piston arranged at one end of the absorber rod moves
And a variable orifice provided in the piston
An electromagnetic actuator provided outside the other end of the bushover rod
Equipped with variable damping force shock absorber that can be varied by eta
The absorber rod and the absorber cylinder
A relative displacement amount detection sensor that detects the relative displacement with
And provided outside the other end of the absorber rod,
Wherein the relatively movable said absorber rod absorber
A magnetic detection sensor that detects magnetic information whose arrival time changes according to the relative displacement amount with the cylinder ; an arithmetic unit that calculates the relative displacement amount from the arrival time of the detected magnetic information; A relative displacement detection sensor comprising: an adoption prohibition unit that does not use the detected magnetic information for calculating the relative displacement when an electromagnetic actuator disposed in the vicinity is operated.