JPH0242202A - Piston position detecting device - Google Patents

Abstract

PURPOSE:To simplify the structure of a piston position detecting device and to enhance the environment resistance by detecting a variation in the inductance of a coil so as to know a position of a piston. CONSTITUTION:A piston rod 27 is composed of a nonmagnetic part 272 and a magnetic part 271 which are joined together at the middle of the rod 27, and a position detecting device 43 composed of a coil 432 having an enamel wire or the like wound on a resin bobbin 431 and a magnetic material 433 covering the outside of the bobbin 431 is provided in the upper section of a cylinder body 21, and is connected thereto with an inductance detecting means and a computing means for computing a position of the piston from a variation in inductance. With this arrangement, since the position of the piston 22 can be known from a variation in the inductance of the coil 432, it is possible to simplify the structure of the detecting devices, and further, it is possible to enhance the environment resistance thereof in a pace where the environmental condition relating to temperature variations, vibration or the like is severe.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a piston position detection device for detecting the position of a piston disposed inside a cylinder in a cylinder device, for example, for adjusting the torsional force of a stabilizer. It is effective when used to detect the piston position of a cylinder device.

[Conventional technology]

As a means of detecting the piston position in a cylinder device,
Conventionally, for example, a potentiometer (variable resistor) was linked to the piston rod to detect the piston position from changes in voltage, or, as shown in Japanese Utility Model Application Publication No. 60-77802, a magnetizing body was placed on the piston rod. However, methods have been proposed, such as detecting the piston position using a reading head provided in a part of the cylinder.

[Problem to be solved by the invention]

However, when using a sensor with a contact distance such as a potentiometer, or when using a configuration that requires an electric/electronic circuit in the sensor section such as a magnetic read head, the structure of the sensor itself becomes complex, and, for example, It is difficult to apply it to places with severe environmental conditions such as temperature changes and vibrations, such as automobile suspension systems.

The present invention has been made in view of the above points, and an object of the present invention is to provide a piston position detection device for a cylinder device that has a simplified structure and excellent environmental resistance.

[Means to solve the problem]

In order to achieve the above object, a piston position detection device according to the present invention includes a piston that is slidably disposed inside a cylinder, a piston that moves integrally with the piston, and a first
a piston rod constituted by a member having a second different magnetic permeability; and a periphery of the piston rod such that when the piston slides, portions of the piston rod having the first and second magnetic permeabilities pass. a hollow coil that is provided in the coil and is provided with an electric signal that changes at a predetermined period; a detection means for detecting a change in inductance of the coil; and a detection means for detecting a change in inductance of the coil detected by the detection means; The structure includes calculation means for calculating the position of the piston.

[Action/effect of the invention]

According to the above configuration, when the members having the first and second magnetic permeabilities of the piston rod pass through the coil,
The inductance of the coil changes. By detecting changes in the inductance of this coil, the position of the piston can be determined.

At this time, since the detecting means can be composed only of a coil wound with a conducting wire, the piston position detecting device according to the present invention can be used even in places with severe environmental conditions such as temperature changes and vibrations.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, the cylinder device 16 is divided into an upper chamber 25 and a lower chamber 26 by a piston 22 slidably disposed within a cylinder body 21. As shown in FIG. Pressure fluid is supplied and discharged from the upper chamber port 23 and lower chamber port 24 in the upper chamber 25 and lower chamber 26, respectively. A piston rod 27 is fixed to the piston 22, and a position detection device 43 is installed at the upper part of the cylinder body 21.

The piston rod 27 is made by joining a non-magnetic material (for example, 5US304) 272 as a member with a first magnetic permeability and a magnetic material (for example, 5IQC) 271 as a member with a second magnetic permeability by a method such as friction welding. be. In addition, boundary part 2
The position 73 connects the piston rod 27 to the cylinder device 16.
It is designed to be at an intermediate position in the piston stroke (the range in which the screw 1-22 can move within the cylinder body 21) when installed in the cylinder body 21.

Further, as shown in FIG. 2, the position detection device 43 includes a coil 432 made by winding an enameled wire (copper wire coated with enamel) around a bobbin 431 made of resin, and further winding the outside of the bobbin 431 into a coil 432. Magnetic material (e.g. 5IOC) 433
It is made up of what was covered with. This magnetic material 433 is what is called a circumcenter, and is for concentrating the magnetic flux generated by the coil 432 on the piston rod 27 without leaking to the outside.

Here, when the inductance of the coil 432 is measured,
When the non-magnetic material 272 passes through the inside of the coil 432, the inductance becomes small (minimum value L sia) because the magnetic permeability of the non-magnetic material 272 is very small, and when the unidirectional material 271 passes through the inside of the coil 432, the magnetic material 271 Since the magnetic permeability of is large, the inductance becomes large (maximum value, ,X). Further, when the boundary portion 273 is within the coil 432, the coil 43
The inductance of No. 2 has a minimum value L187, a maximum value, and a value between □. That is, the inductance changes as shown in FIG.

Therefore, if a comparison process is performed using the inductance L, 6, which corresponds to the intermediate position of the piston stroke, as a threshold value, the piston stroke of the cylinder device 16 will be reduced by the magnetic material 27.
It can be used as a switch to distinguish whether it is on the 1 side or the non-magnetic material 272 side, that is, whether it is on the contraction side or the expansion side from the intermediate position. Note that the change in inductance mainly occurs when the boundary portion 273 of the piston rod 27 passes through the inside of the coil 432.
If the width (length in the axial direction) is made thinner, the switch can detect the intermediate position with high accuracy.

An example in which the present invention is used as a switch for detecting an intermediate position has been described above, but an example in which the present invention is used as an analog sensor will now be described.

As mentioned earlier, the inside of the coil 432 is connected to the piston rod 2.
7, the inductance of the coil 432 changes continuously.

Therefore, if a thick coil 432 is used, the inductance will gradually change near the intermediate position, and the coil 432 can be used as an analog sensor in this region. However, if a thick coil 432 is simply used, the inductance change will increase as the magnetic material 271 penetrates into the coil 432, as shown by the broken line (b) in FIG. Therefore, the magnetic material 271 side, the non-magnetic material 272 side
The resolution on the side becomes non-linear, and a sufficient amount of change cannot be obtained especially on the non-magnetic material 272 side, resulting in poor resolution. In order to improve this problem, the magnetic flux passing path of the coil 432 may be made asymmetrical with respect to the installation surface of the coil 432. That is, the effective magnetic permeability of the magnetic flux passage paths above and below the coil 432 may be changed. As a specific method for this purpose, as shown in FIG.
The bobbin 43 is placed so that the thick part of 1 faces the non-magnetic material 272
Install 1. As a result, the magnetic material 271 is attached to the coil 43.
Even if the coil 432 penetrates deeply into the coil 432, a change in the inductance of the coil 432 is suppressed because the thick part of the resin bobbin 431 exists in the middle of the magnetic flux path of the coil 432. Therefore, the relationship between the stroke of the piston rod 27 and the inductance of the coil 432 at this time is shown by the solid line (
As shown in a), the linearity is improved and there is no difference in resolution on either the extension side or the contraction side.

Next, the vehicle attitude control device 1 using the cylinder device 16 having the above-mentioned configuration will be explained based on FIG. 5.

In FIG. 5, in the front wheel stabilizer device 2, the left and right front wheels 6.10 are respectively provided with left and right front wheel shock absorbers 7,
1 and right and left front wheel suspension arms 8 and 12, the vehicle body 9 is supported by the vehicle body 9.

Further, the torsion portion of the front wheel stabilizer bar 13 is rotatably supported by the vehicle body 9 by bearings 14 and 15 fixed to the vehicle body 9 with bolts or the like.

One end portion 13a of the front wheel stabilizer bar 13 is coupled to a sprung portion of the right front wheel shock absorber 11 via a cylinder device 16 whose connection distance can be adjusted. Thereby, the connection distance between the one end 13a of the front wheel stabilizer bar 13 and the unsprung portion of the right front wheel shock absorber 11 can be adjusted by expanding and contracting the cylinder device 16. The other end 13b of the front wheel side stabilizer bar 13 is
Left front wheel shock absorber 7 via link rod 17
is connected to the lower part of the spring. Further, the steering mechanism 19 is
Depending on the operation of the steering wheel 18, the left and right front wheels 6.
This is to change the direction of 10.

As shown in FIG. 6, the electronic control device 4 includes a CPU 4a,
ROM4b, RAM4c, data bus 4f.

A vehicle speed sensor 4L comprising an input section 4d and an output section 4e, which detects the running speed of the vehicle; a steering angle sensor 42 which detects the steering angle of the steering wheel per day; and a position according to the present invention which detects the piston position of the cylinder device 16. A control signal is output to the hydraulic device 3 in accordance with the signal from the detection device 43.

As shown in FIG. 6, the cylinder device 16 is operated by pressure oil supplied from the hydraulic device 3 in response to a control signal from the electronic control device 4.

In the hydraulic system 3, a hydraulic pump 31 driven by an engine 30 via a power transmission mechanism sucks hydraulic oil from a reservoir tank 34, and operates through a conduit 33a and a control valve (4-point, 3-position solenoid valve) 32. , pressure oil is supplied to the cylinder device 16 via pipes 33c and 33d. The control valve 32 is moved to a neutral position 32a in response to a control signal from the electronic control device 4.
, an extended position 32b, a retracted position 32c, and any intermediate position thereof.

Here, how the position of the piston 22 is detected by the position detection device 43 will be explained using FIG. 7.

A coil 43 with an inductance L is connected in series with a pulse voltage having a voltage width E that changes periodically by a pulse voltage generator 4g provided in the output section 4e of the electronic control device 4.
2 and is applied to a resistor 4h with a resistance value R. At this time, if the current flowing through the coil 432 and the resistor 4h is i, then the terminal voltage v of the coil 432 is, so the following differential equation is obtained. Solving this, i = (1-
e-(*/L I L ), and the terminal voltage v2 of the resistor 4h is vz=Ri=E(1e-"8+1). This terminal voltage v2 and the predetermined reference voltage V r
of is compared with the comparator 41, when the terminal voltage v2 is large, the output of the comparator 41 becomes Hi, and the terminal voltage v2
When is small, the output of the comparator 41 becomes Low. The pulse output of the comparator 41 is converted into an average voltage by a pulse width to voltage conversion circuit 4j comprising a resistor 4 and a capacitor 41. Here, the inductance L of the coil 432
When the inductance L is small, the pulse output of the comparator 41 has a high percentage, and when the inductance L is large, the low percentage increases. Therefore, the pulse width → the average voltage value converted by the voltage conversion circuit 4j is This corresponds to the value of inductance L.

This average voltage and the threshold voltage Vth are compared by the comparator 4M, and since this threshold voltage V is determined to correspond to the intermediate position of the piston stroke, the output of the comparator 4M From this, it is possible to detect whether the piston stroke is on the extension side or on the contraction side.

Next, the basic operation and control method in the above configuration will be explained.

First, a description will be given of when the vehicle is traveling straight ahead. When the vehicle is traveling straight ahead, the control valve 32 shown in FIG. 6 is set to the neutral position 32a. At this time, the pressure oil discharged from the hydraulic pump 31 returns to the reservoir 34 via the pipe line 33a, the control valve 32, and the pipe line 33b. On the other hand, since the pipes 33c and 33d are blocked by the control valve 32, the upper and lower chambers 25, 26 of the cylinder device 16
is maintained in an oil-tight state, and the piston 22 is kept in an oil-tight state, and the piston 22 is
It is fixed within 1. That is, the cylinder device 16 functions as a kind of rigid body like the link rod 17, and the stabilizer 13 exhibits its inherent torsional rigidity to ensure running stability of the vehicle.

Next, the time of turning will be explained. When turning,
The target expansion/contraction amount of the cylinder device 16 is determined according to a predetermined relationship depending on the vehicle speed and the magnitude of the steering angle. The hydraulic device 3 is driven so that the cylinder device 16 is expanded or contracted according to the target expansion/contraction amount. That is, when extending the cylinder device 16, the control valve 32 is driven toward the extended position 32b or the near solenoid is energized. At this time, the boat of the control valve 32 connected to the lower chamber 26 of the cylinder device 16 via the pipe 33d is immediately fully opened.
Pressure oil from the pump 31 is supplied to the lower chamber 26 of the cylinder device 16 via the pipe line 33a, the control valve 32, and the pipe line 33d. On the other hand, the boat of the control valve 32 connected to the upper chamber of the cylinder device 16 via the conduit 33c operates so that its opening area increases as the applied current increases. Therefore, by controlling the applied current, the amount of oil flowing out through the pipe line 33c is adjusted. In other words, the piston 22 is moved to the upper chamber 25 only after the pressure oil flows out from the upper chamber 25.
Since the piston 22 can be moved to the side, the amount of movement of the piston 22 can be adjusted by controlling the current applied to the linear solenoid. Furthermore, since the relationship between the magnitude of the energizing current and the amount of spilled oil, that is, the amount of movement of the piston can be known in advance, the electronic control bag W4 can predict and calculate the position of the piston 22 from the magnitude of the energizing current to be output and the energizing time. .

In this prediction calculation, the piston position detection device 43 according to the present invention is used to correct the predicted position of the piston 22,
Thereafter, when it is determined that the predicted position of the piston 22 has reached the target position, the energization of the linear solenoid is terminated. At this time, the control valve 32 returns to the neutral position 32a, the upper and lower chambers 25, 26 of the cylinder device 16 are again maintained in an oil-tight state, and the piston 22 is fixed at the target position. As described above, since the hydraulic device 3 has the configuration of a meter-out hydraulic circuit, it is possible to accurately adjust the amount of oil from a small amount to a large amount of oil, and the cylinder device 16 can be reliably controlled.

Also, when contracting the cylinder device 16, the control valve 3
2 toward the retracted position 32c and energizes the near solenoid. At this time, the pipe line 33 is connected to the upper chamber 25 of the cylinder device 16.
The boat of the control valve 32 connected through the pipe c is immediately fully opened, and the pressure oil from the pump 31 is transferred to the upper chamber 25 of the cylinder device 16 via the pipe 33a, the control valve 32, and the pipe 33C.
supply to On the other hand, the pipe line 3 is connected to the lower chamber 26 of the cylinder device 16.
The boat of the control valve 32 connected via 3d operates so that its opening area increases as the applied current increases. Therefore, by controlling the applied current, the amount of oil flowing out through the conduit 33d is adjusted. Therefore, the piston position is predicted in the same way as when the cylinder device 16 is extended, and when it is determined that the piston 22 has reached the target position, the energization is terminated and the piston 22 is fixed at the target position.

In the above embodiment, as shown in FIG. 1, the piston rod 27 is made of a magnetic material 271 and a non-magnetic material 27.
2 are connected by a plane perpendicular to the axial direction, but
In general, any structure may be used as long as it can change the inductance by connecting two or more members with different magnetic permeabilities.

For example, as shown in Fig. 8(a), if the two members to be joined (magnetic material and non-magnetic material) are provided with convex and concave tapered surfaces so that the boundary part becomes conical, the change in inductance can be reduced. Since it becomes smooth near the boundary, the detection range as an analog sensor can be expanded.

Further, as shown in FIG. 8(b), even if two materials are connected with a screw, the detection range as an analog sensor can be expanded in the same way as above.

Furthermore, in the configuration in which the screws are used for connection as shown in FIG. 8(C), by further inserting a member having a magnetic permeability between the two types of members between the two members,
Since even smoother inductance changes can be realized, the detection range as an analog sensor is further expanded.

Although the above is an example of a configuration in which materials having different magnetic permeabilities are connected, it is possible to configure the piston rod so that the magnetic permeability effectively differs even if only one type of magnetic material is used.

For example, as shown in Figure 9(a), 1/1 of the length of the magnetic material is
If holes are drilled up to the region 2, there will be a difference in magnetic flux distribution between areas with holes and areas without holes, and the inductance of the coil will change.

Furthermore, if the diameter of the hole is changed stepwise as shown in FIGS. 9(b) and 9(C), or if a conical hole is formed, a wider range of inductance changes can be obtained.

In this example, a resistor is connected in series with the coil as a means of detecting changes in the inductance of the coil.
Although the time constant of the output response to the pulse voltage input was measured, a capacitor may be connected to measure the resonance frequency, or the phase difference of the current to the AC voltage input may be measured.

Further, in this embodiment, the boundary of the piston rond is designed to be at the intermediate position of the piston stroke, but when the present invention is used as an analog sensor, the position of this boundary is Any position that passes through the coil is fine.

Note that a cylinder device including the piston position detection device of the present invention may be used as a shock absorber. At this time, for example, the position of the boundary part of the piston rond is set as the intermediate position of the piston stroke, and the coil is arranged at a position a predetermined distance from the intermediate position. By detecting how many times the boundary portion of the piston rond passes through the coil within a certain period of time, it is possible to determine whether the road surface on which the vehicle is traveling is a good road or a bad road.

〔Effect of the invention〕

As described above, according to the present invention, since the position of the piston is detected from the change in inductance of the coil, the structure can be simplified, and furthermore, it can be used in places with severe environmental conditions such as temperature changes and vibrations. Excellent environmental resistance can also be achieved.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing the overall configuration of one embodiment of the present invention,
2(a) and 2(b) are longitudinal cross-sectional views and side views showing the structure of the position detection device in FIG. 5 is a block diagram showing the overall configuration of the vehicle attitude control device, FIG. 6 is a schematic diagram of the electronic control device and hydraulic circuit that control the cylinder device in FIG. 5, and FIG.
This figure is a circuit diagram for detecting the piston position in FIG. 6, and FIGS. 8 and 9 are explanatory diagrams illustrating other embodiments of the piston rond in FIG. 1. 16... Cylinder device, 21... Cylinder body. 22... Piston, 25... Upper chamber, 26... Lower chamber, 27... Piston Rondo, 271... Magnetic material, 2
72...Nonmagnetic material, 273...Joint part, 43...
Position detection device 431...bobbin, 432...coil.

Claims (4)

[Claims] (1) A piston that is slidably disposed inside the cylinder; a first piston that moves together with the piston;
a piston rod constituted by a member having a second different magnetic permeability; and a periphery of the piston rod such that when the piston slides, portions of the piston rod having the first and second magnetic permeabilities pass. a hollow coil that is provided in the coil and is provided with an electric signal that changes at a predetermined period; a detection means for detecting a change in inductance of the coil; and a detection means for detecting a change in inductance of the coil detected by the detection means; A piston position detection device comprising: a calculation means for calculating the position of a piston. (2) The piston position detection device according to claim 1, wherein the piston rod is constructed by joining at least two types of members having different magnetic permeabilities. (3) A claim characterized in that one member is provided with a convex portion and the other member is provided with a recessed portion to form a boundary portion of the piston rod, and the magnetic permeability of the boundary portion of the piston rod gradually changes. Item 1. The piston position detection device according to item 1. (4) The piston position detection device according to claim 1, wherein the magnetic flux passage path of the coil is asymmetrical with respect to the installation surface of the coil.