JP2001174205A - Position-detecting mechanism for poston rod and autotensioner using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a position detecting mechanism of a piston rod which can determine and detect continuously or in multipoint that the amount of protrusion of a piston rod of a cylinder unit increases or decreases with secular change or the like and a piston rod position changes. SOLUTION: A piston 12 is inserted into a cylinder 11 of a cylinder unit 10, in such a manner that going forward and backward is possible. The amount of protrusion that a piston rod 13 of the piston 12 protrudes from a cylinder end wall 11b is detected by using a position detecting mechanism constituted of a detection coil 17 accommodated in a bobbin 16 formed in the cylinder end portion, a flange part 14 formed in the piston rod, and a coil spring 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanism for detecting the position of a piston rod which is connected to a piston inserted into a cylinder so as to be able to advance and retreat, and which protrudes from the cylinder, and an auto-tensioner using the same.

[0002]

2. Description of the Related Art A cylinder unit of a type in which a piston rod projects from a cylinder in which a piston is inserted so as to be able to move forward and backward, converts hydraulic pressure into mechanical force via a piston rod and transmits the mechanical force to a target device, or a movement stroke. It is used for various purposes such as measuring the moving distance using the property that can be set long. As the former example, a cylinder unit generally used as an auto-tensioner, which is used in the belt transmission shown in FIG. 12, is known. This belt transmission is used to drive the camshaft of an automobile engine.

[0003] The illustrated belt transmission has a crankshaft.
Pulley P attached to G1₁And the pulley attached to the camshaft 2
Re-P_Two, And a pool attached to the drive shaft 3 of the oil pump
Re-P _ThreeIn between the timing belt 4
The rotation of the shaft 1 is transmitted to the camshaft 2 and the drive shaft 3.
Like that. For this belt transmission,
A pulley that can swing about the shaft 5 on the slack side of the belt 4
A rear arm 6 is provided.
Pushed with a push rod 8 protruding from the
Tension pulley 9 supported on the swing-side end of arm 6
To the timing belt 4 and
The change in the tension of G
8 so that the belt tension is kept constant by absorbing
are doing.

In the above-described camshaft driving belt transmission device incorporated in an internal combustion engine, the timing belt 4 changes due to a change in the distance between pulley cores due to thermal expansion of the internal combustion engine main body during operation and an extension of the belt due to aging. The reason is that the cylinder unit of the auto tensioner 7 absorbs the elongation of the belt and keeps the belt tension constant.

[0005] Here, as an auto tensioner 7 used for adjusting the tension of the belt, those described in Japanese Patent No. 1891868 or Japanese Patent Publication No. 7-117130 are known.

The push rod 8 in the auto tensioner 7 moves forward and backward due to a change in the tension of the timing belt 4 to keep the tension of the timing belt 4 constant. The rod 8 moves forward to absorb the extension.

In general, in a belt transmission for driving a camshaft, when the auto tensioner 7 is not mounted, the timing belt 4 is replaced with a guide of traveling 100,000 km, but the auto tensioner 7 is mounted. In such a belt transmission, since the tension of the timing belt 4 is stable and the belt does not flap during operation, the durability of the timing belt 4 is improved, and it is possible to guarantee that the timing belt 4 exceeds 100,000 km.

[0008]

By the way, the stroke of the push rod in the auto tensioner is finite, and when the push rod advances to a position beyond the effective stroke, the tension of the timing belt cannot be kept constant. In this case, the timing belt has a low tension, and the timing belt flaps to cause tooth jumps, or the belt deteriorates due to flapping, and the durability is reduced. It is anticipated that the protrusion amount of the push rod of the auto tensioner will gradually increase, and eventually the timing belt will not function. As a measure to predict such a phenomenon in advance, for example, a detection sensor (coil) is provided at the cylinder end, a non-magnetic ring is fitted to the piston rod to constitute a detection means, and a non-magnetic ring is provided at the center of the detection sensor. When the boundary between the rod and the rod (magnetic material) is reached, a detection signal is obtained in the detection circuit due to a change in the magnetic permeability, and the position can be detected.

However, such a detecting means can detect a change in the position of the piston rod only at a specific position, and cannot detect a change in the position of the piston rod continuously or in multiple points. In particular, in spite of the fact that it is known that the position of the push rod of the auto tensioner changes as the timing belt elongates as the travel distance of the car increases, as in the case of an auto tensioner,
At present, detection of a change in the amount of protrusion of the push rod is not performed. In the process of gradually increasing the push rod protrusion, depending on the elongation of the belt, for example, caution is required at half the elongation to breakage, "warning" at 80% elongation, "breakage" if broken If a gradual warning is given, measures can be taken for the timing of belt replacement, but such measures are not currently taken at all. In addition, there are various target devices other than those described above in which it is desirable to take the same countermeasures for a cylinder unit that is mounted at a position that is difficult to see, such as an auto tensioner.

According to the present invention, when the amount of protrusion of a piston rod of a cylinder unit changes along with deterioration of a target device due to aging or the like, and increases or decreases, a change in the position of the piston rod is determined and continuous. Another object of the present invention is to provide a piston rod position detecting mechanism capable of detecting a multi-point shape and an auto-tensioner using the same.

[0011]

According to the present invention, as a means for solving the above-mentioned problems, a piston is inserted into a cylinder closed at both ends so as to be able to advance and retreat, and a piston rod protruding from a cylinder connected to the piston is provided. In order to detect the position, a detection coil provided at the rod projecting end of the cylinder, and a flange provided on the piston rod opposite to the outer end of the detection coil are provided. This is a piston rod position detection mechanism configured to detect the position of the piston rod by a detection signal based on a change in inductance of the detection coil.

[0012] The piston rod position detecting mechanism of the present invention having the above-described structure is constituted by a detecting coil provided on the cylinder side and a flange provided on the piston rod, and the flange is moved relative to the detecting coil by movement of the piston rod. Approaching and moving away from each other affects the magnetic circuit formed by the detection coil, and changes the inductance indicating the magnetic coupling state between the detection coil and the flange.The current or voltage in the detection coil is determined based on the change in the inductance. Changes. Therefore, by detecting the above change in the detection circuit, the position change of the piston rod is detected continuously or in multiple points.

As another means for solving the above-mentioned problem, a piston is inserted into a cylinder closed at both ends so as to be able to advance and retreat, and the position of a piston rod protruding from a cylinder connected to the piston is detected. And a coil spring mounted on the outer periphery of the piston rod and facing the detection coil. The coil spring is held between the cylinder and the piston rod to change the position of the piston rod. It is also possible to employ a piston rod position detection mechanism configured to detect the position of the piston rod based on a detection signal based on a change in inductance of the detection coil that changes in the above.

The operation of detecting the position of the piston rod by the position detection mechanism is basically the same as that of the first invention. In this case, the detection coil detects the position of the piston rod based on a change in inductance caused by expansion and contraction of the coil spring. Detect the position.

According to a third aspect of the present invention, an exciting coil is disposed so as to face the detecting coil used in the position detecting mechanism according to the second aspect of the present invention, and the lines of magnetic force of each coil are in the normal direction of the piston rod. As described above, the coils may be wound concentrically with each other. In this configuration, a high-frequency signal is applied to the excitation coil, and a change in the magnetic flux is detected by the detection coil. When the coil spring expands and contracts due to the movement of the piston rod, the volume of the magnetic material in the magnetic flux changes, and the detection coil changes. , The position of the piston rod can be determined by detecting a change in the detection signal with a detection circuit. In the measurement method in which a magnetic flux is generated by the excitation coil and the detection signal is detected by the detection coil, the sensitivity is further improved as compared with the detection method using only the detection coil.

As an auto-tensioner having any one of the above-mentioned means for solving the above-mentioned problems, a piston is inserted into a cylinder having both ends closed so as to be able to advance and retreat, and a piston rod connected to the piston is connected to a cylinder. The hydraulic oil is sealed between the chambers by projecting from one end of the cylinder and defining each chamber defined by a piston in the cylinder as a pressure chamber on the side receiving the load acting on the outer end of the piston rod and a reservoir chamber on the opposite side. An auto-tensioner provided with a rod spring for urging the piston rod in the protruding direction may include the position detecting mechanism according to any one of the above three inventions at the protruding end of the piston rod. . Since the position detecting mechanism according to any one of the above aspects is provided, the position of the piston rod is detected when used as an auto-tensioner, and a change in position due to aging or the like is detected.

Further, a piston is provided in a cylinder having both ends closed so as to be able to advance and retreat, a pair of electromagnetic coils is provided with the piston interposed therebetween, a piston rod is connected to at least one side of the piston, and the end of the piston rod is connected to the cylinder end. In the electromagnetically driven valve formed so as to protrude and move the piston forward and backward by the magnetic attraction force of the electromagnetic coil to move the protruding end of the piston rod, any one of the above three inventions may be provided at the protruding end of the piston rod. Such a position detecting mechanism may be provided. Again,
Since the position detecting mechanism according to any one of the above three aspects is provided, the position of the piston rod is detected when used as an electromagnetically driven valve, and a change due to aging or the like is detected.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a main sectional view of the cylinder unit of the first embodiment. Cylinder unit 10
Is closed at both ends of a cylinder 11 by end walls 11a and 11b, and a piston 12 is inserted therein so as to be able to advance and retreat, thereby dividing the inside of the cylinder into an A chamber and a B chamber. A piston rod 13 is attached to one end of the piston 12, and the piston rod 13 protrudes through one end wall 11b. A flange 14 made of a magnetic material is provided at an appropriate position on the protruding shaft of the piston rod 13, and a coil spring 15 is inserted between the flange 14 and the cylinder end wall 11b opposed thereto. The coil spring 15 serves as a holding ring.

The illustrated cylinder unit 10 is configured as a type of hydraulic damper similar to an auto tensioner described later, and although not shown, the piston 12 is provided from the chamber A to the chamber B or vice versa. A required number of small holes having a diameter through which the fluid can flow in the direction, or an annular clearance is provided between the small holes and the cylinder.

Although the pressing ring of the flange 14 is press-fitted to the piston rod 13 in the illustrated example, it may be formed integrally with the material of the piston rod 13. Further, when the pressing ring of the flange portion 14 is provided separately from the piston rod as described above, a non-magnetic and conductive material such as aluminum or copper may be used instead of the magnetic material.

The end wall 1 on the projecting side of the piston rod 13
1b is a bobbin 16 surrounding the outer periphery of the coil spring 15
The bobbin 16 has a piston rod 1
A detection coil 17 for detecting the position 3 is accommodated. A predetermined power supply voltage is sent from the detection circuit 19 to the detection coil 17, and as described later, the detection coil 17
When the coil spring 15 and the flange 14 move with respect to the magnetic circuit formed by the coil, the inductance changes, the voltage or current value of the detection coil changes based on the change in the inductance, and the detection signal is detected by the detection circuit 19. By doing so, the position of the piston rod 13 is detected. Therefore, the detection coil 17, the flange 14, and the coil spring 15 constitute a position detection mechanism.

The piston rod 1 is detected by a piston rod position detecting mechanism provided in the cylinder unit having the above-described structure.
The position of No. 3 is detected as follows. When the cylinder unit is a type of hydraulic damper having a coil spring 15 and a magnetic material flange 14 as shown in FIG. 1, generally, a load acts on the protruding end of the piston rod 13 to It stops at the position shown in balance with the elastic force. When the load decreases for some reason, the piston rod 13 moves forward (rightward in the figure) from the position shown in the figure by the elastic force of the coil spring 15, and the coil spring 1
5, the distance between the coils increases.

As described above, a predetermined power supply voltage is sent to the detection coil 17, and the magnetic circuit formed by the detection coil 17 shown in FIG. And spring 15,
A magnetic coupling state represented by a predetermined inductance value occurs between the flanges 14. However, when the piston rod 13 moves forward, the flange 14 separates from the detection coil 17 and the coil interval of the coil spring 15 increases, so that this inductance value changes and decreases. Conversely, when the load increases and the piston rod retreats, the flange 14 approaches the detection coil 17, the coil interval of the coil spring 15 decreases, and the inductance value increases.

Such a change in the inductance value is determined by a coil spring 1 having a wire diameter of 0.55 mm and an outer diameter of 10 mm.
5 and FIG. 3 shows the measurement results obtained by using a magnetic material as the flange portion 14. The coil spring length on the horizontal axis represents the length of the coil spring between the flange 14 and the cylinder end wall 11b. The inductance value is the spring 15 and the flange 1
4 is a combined inductance value for both. As shown in the drawing, when the coil spring length changes, the inductance value changes, so that the resistance value of the detection coil 17 in the electric circuit changes, and the current value or voltage value supplied to the detection coil 17 changes. By detecting this change in the detection circuit 19, a change in the position of the piston rod 13 can be detected continuously or at multiple points.

On the other hand, FIG. 4 shows a measurement result in the case of a partially modified example in which a non-magnetic, conductive material is used as the pressing ring of the flange portion 14. In this case, when the coil spring contracts in the direction of shortening, the aluminum or copper holding ring of the flange portion 14 approaches the detection coil 17 and the eddy current is generated so as to obstruct the flow of magnetic flux of the magnetic circuit formed by the detection coil 17. It occurs on the collar 14.

Accordingly, the inductance value decreases as the coil spring length decreases, and the inductance value increases as the coil spring length increases. Such characteristics show that the characteristics change in a reverse relationship to the basic example in which the flange 14 is made of a magnetic material. However, the change of the inductance value is larger than that of the basic example, and therefore, the partial modification has higher sensitivity of the detection circuit.

Next, although not shown, the coil spring 15 may be omitted, which is referred to as a second embodiment. In this case, when the cylinder unit is configured as a damper, a coil spring may be provided in the chamber A instead of the coil spring 15 to push or pull the piston 12. Further, although not shown, when the cylinder unit 10 is used as a general cylinder that converts the hydraulic pressure into a pressing force and transmits it through the piston rod 13, the working fluid is supplied to the chambers A and B in the cylinder 11. Is connected to an external piping system that can supply and discharge air. Therefore, in this case, the coil spring 15 need not be provided. However, the flange portion 14 is made of a non-magnetic and conductive material such as aluminum or copper.

In this embodiment, the detection coil 17 and the press ring 14 of the flange 14 provided on the piston rod 13 constitute a position detection mechanism. The basic operation is the same as in the first embodiment. However, since the coil spring 15 is omitted, the detection sensitivity is low, but a detection sensitivity that is practically acceptable is obtained.

FIG. 2 is a main sectional view of a cylinder unit according to a third embodiment. This embodiment differs from the first embodiment in that the flange portion 14 is omitted, and the terminal of the coil spring 15 is provided by being locked in a locking hole 18 provided at an appropriate position of the piston rod 13.

Also in this case, the detection coil 1 is changed based on the change in the inductance value due to the expansion and contraction of the coil spring 15.
7, the change in the position of the piston rod 13 can be detected in the same manner as in the first embodiment.
Is reduced by the amount omitted. However, when detecting a change in position, it is possible to obtain a change in inductance value with a practically acceptable sensitivity (not shown).

FIG. 5 shows a main sectional view of the fourth embodiment. This embodiment is an example in which a position detection mechanism is combined with an auto tensioner. Since the auto tensioner is also a type of hydraulic damper, the position detection mechanism can be applied as in the first to third embodiments. Since the auto tensioner 20 itself is the same as the conventional one, a brief structure will be briefly described below.

The illustrated auto-tensioner 20 has an end wall 2 in a cylinder 21 having one end closed by an end wall 21a and an upper end opened.
An inner cylinder 21 'is fixed to the side 1a, and a piston 22 is slidably fitted to the cylinder 21' so as to be able to advance and retreat. The inside of the cylinder 21 or 21 ′ is A
A chamber (pressure chamber) and a chamber B (reservoir chamber) are partitioned, and an upper opening of the chamber B is closed by an oil seal 21b.
Reference numeral 24 denotes a retaining ring as a retaining member, which is fitted in a groove provided on the inner diameter of the cylinder 21.

A rod insertion hole is formed on one side of the piston 22, and a push rod 23 (piston rod) inserted into this hole slidably penetrates the oil seal 21b and protrudes to the outside. The piston 22 and the push rod 23 are integrally connected by a spring 25 incorporated in the A chamber. A through hole 27 is formed in the piston 22, and a check valve is formed by the ball 26 held by a retainer provided on the opposite side of the piston 22 and the through hole 27.

A guide flange 22 'which is slidable along the inner diameter of the cylinder 21 is fitted to the push rod 23, and is pressed by the elastic force of a pressure adjusting spring 25' incorporated below the push rod 23 so as to be pushed. Are projected outward. Numeral 28 denotes a through hole provided in the flange 22 ', and the flange 2 in the hydraulic oil sealed in the chamber B.
It is provided to allow the 2 ′ to move freely. The hydraulic oil is sealed so that a C chamber of an air layer is formed between the upper surface and the oil seal 21b. Reference numeral 29 denotes a separator, which is provided to prevent the vibration air on the upper surface of the hydraulic oil from entering the pressure chamber.

The retaining ring 24 outside the oil seal 21b
Are provided at predetermined intervals as shown in the figure, and a detection coil 17 housed in a bobbin 16 similar to the first to third embodiments is provided therebetween. The bobbin 16 has an inner peripheral diameter reduced at one end, and a coil spring 15 is provided between the inner peripheral diameter of the bobbin 16 and the flange 14 provided on the push rod 23.
(Pressing ring) is inserted. A detection circuit 19 is connected to the detection coil 17.

In the illustrated example, it is assumed that the inside diameter of one side wall of the bobbin 16 is reduced so as to slide to the outside diameter of the push rod 23, and one end of the coil spring 15 (pressing ring) is brought into contact with the side wall. However, the inner diameter of the retaining ring 24 may be made smaller to make contact with the side wall thereof without reducing the inner diameter of the bobbin.

The operation of the auto-tensioner 20 according to the fourth embodiment configured as described above as an auto-tensioner is the same as the conventional one, and operates as follows. The auto tensioner 20 is incorporated in the belt transmission shown in FIG.
When the tension of the timing belt 4 increases, the push rod 23 is pushed down via the pulley arm 6, and the piston 22 descends. Then, the hydraulic oil in the chamber A is compressed and becomes higher than the pressure in the chamber B. Therefore, the check valve closes the through hole 27 by the ball 26.

Therefore, the pressing force from the timing belt 4 acting on the push rod 23 is received and suppressed, but the hydraulic oil is slightly reduced due to the minute gap formed between the sliding surface of the piston 22 and the cylinder 21 '. Each time the pressure flows to the chamber B, the pressing force acting on the push rod is attenuated, and the auto tensioner acts as a kind of damper.

On the other hand, when the timing belt 4 becomes slack, the push rod 23 moves rapidly in the direction protruding from the cylinder by the elastic force of the pressure adjusting spring 25 '. Therefore, the piston 22 is also pushed upward by the spring 25, so that the pressure in the chamber A becomes lower than the pressure in the chamber B, and the through hole 27 of the check valve is opened. Then, the hydraulic oil in the chamber B flows through the through hole 27 to the chamber A, and therefore the push rod 23
The piston 22 quickly moves upward to absorb the slack of the timing belt 4 and keep the tension of the timing belt 4 constant.

As described above, the auto tensioner 20 has the function of absorbing the fluctuation of the tension of the timing belt 4 and keeping the tension constant. However, when the timing belt 4 is used for a long period of time, it gradually expands due to aging. Since the push rod 23 protrudes from the initial movement stroke range and absorbs the elongation, the push rod 23 protrudes more than the initial movement stroke as the use period becomes longer.

Therefore, the range of the movement stroke of the push rod 23 of the auto tensioner 20 is set in consideration of these factors. The travel distance may increase, and the push rod 23 may move to the limit of the movement stroke. However, the limit of the movement stroke of the push rod 23 is a position at which the guide flange 22 ′ comes into contact with the oil seal 21 b, and when the push rod 23 moves to the limit position, the tension of the timing belt 4 can be kept constant. Disappears.

However, in the auto-tensioner 20 of this embodiment, the detection coil 17 and the flange 14 provided on the push rod 23, the coil spring 1
Since the position detecting mechanism 5 is provided, an arbitrary moving stroke amount until the push rod 23 reaches the limit of the moving stroke can be continuously or multipoint-detected by the position detecting mechanism.

In the example shown in the figure, the position detecting mechanism is a collar 14,
Since it has both coil springs 15, the flange 1
In the case where a magnetic material is used as the material of No. 4, detection by the inductance characteristic of FIG. As a modified example, when aluminum or copper material is used for the flange portion 14, detection can be performed based on the inductance characteristics of FIG.

In the position detecting mechanism of the second embodiment, the coil spring 15 is omitted, and aluminum or copper is used as the material of the flange portion 14. As described above, the detection sensitivity is lower than the inductance characteristic of FIG. The present invention can be applied to detecting the movement of the push rod 23 of the auto tensioner 20. Further, since the position detecting mechanism of the third embodiment can omit the flange portion 14 and detect the position based on the characteristic of the inductance change due to the expansion and contraction of the coil spring 15, this detecting mechanism can be applied.

As described above, the position of the push rod 23 can be detected as a continuously changing position or as a multi-point by applying the position detecting mechanism of any of the first to third embodiments. When the movement stroke of the push rod 23 gradually changes during long-term use due to factors such as aging of the timing belt, the detection signal from the detection circuit 19 also changes according to the amount of change from the initial setting state of the movement stroke. I do.

Therefore, in a circuit for comparing with a plurality of reference values corresponding to each stage of the change of the movement stroke based on the output signal, for example, an alarm signal such as "caution required", "danger", "limit", or A stop signal or the like can be output based on the comparison of the above signals, and the advantage is obtained that a maintenance time can be grasped early and measures can be taken.

FIG. 6 shows a main sectional view of the fifth embodiment.
This embodiment is an example in which any of the position detection mechanisms of the first to third embodiments is combined with an electromagnetically driven valve, and the illustrated example includes a flange portion 14 and a detection coil 17 among them. , The coil spring 15 is not provided. In the illustrated electromagnetically driven valve, a magnetic material piston 12 is slidably and reciprocally fitted in a cylinder 11 having one end closed by an end wall and an upper end opened. A piston rod 13 is provided at both ends of the piston 12 (may be provided so as to penetrate), and both ends of the piston rod 13 are provided so as to protrude from an outer end of the cylinder 11.

In the cylinder 11, two electromagnetic coils 30 and 31 are installed to face each other with the piston 12 interposed therebetween. Reference numerals 30a and 31a denote magnetic materials, and coils are wound around their inner diameters. The coils are driven by applying a current to the respective coils from a power supply circuit (not shown) to attract and drive the piston 12 with magnetic attraction. Have been. A detection coil 17 housed in a bobbin 16 is attached to the inner end of the cylinder outside the one electromagnetic coil 30, and a flange 14 made of a conductive material is attached to an end of the piston rod 13 on the same side as this. Is provided.

The point that a signal measured by a piston rod position detecting mechanism constituted by the flange portion 14 and the detecting coil 17 is detected by a detecting circuit 19 is the same as in the other embodiments. The piston rod 13 at the opposite end of the piston 12 is connected to the end wall of the cylinder 11 by the bearing bush 3.
It is slidably guided at 2. A protruding end of the piston rod 13 is formed with a valve body 13v fitted to a valve seat of an electromagnetic valve main body (not shown), and the electromagnetically driven valve main body is opened and closed by the advance and retreat of the valve body 13v.

The electromagnetically driven valve having the above structure is used as a valve for feeding a fluid such as a fuel gas to an internal combustion engine or the like. Can be set. In such a valve, when the valve opening / closing operation is performed, when the valve opening / closing amount slightly changes due to aging or the like, the change in the valve opening / closing amount by the position detection mechanism is the same as in other embodiments. Is detected.

When the valve is opened or closed, when one of the electromagnetic coils 30 and 31 is energized, the electromagnet including the energized electromagnetic coil attracts the piston 12 and the piston rod 1
3 moves upward or downward, thereby opening and closing the electromagnetically driven valve body. The opening / closing amount of the valve is adjusted by adjusting the intensity of the current supplied to the electromagnetic coils 30 and 31. Also in this embodiment, the detection coil 17
Is the same as in the other embodiments described above, and a description thereof is omitted. However, it is needless to say that the change can be detected continuously or in multiple points.

In this embodiment, the flange 14 is made of a conductive material.
5 is inserted. As described above, the flange portion 14 made of a non-magnetic material and the coil spring 15 may be combined.
Further, as described above, the third embodiment in which the flange portion 14 is omitted and only the coil spring 15 is used may be adopted.

FIG. 7 shows a main sectional view of the sixth embodiment.
In this embodiment, a cylinder unit 10 ″ having a flange 14 on a piston rod 13 is provided with a position detecting mechanism, as in the first embodiment of FIG. 1. This position detecting mechanism includes an end wall 11b and a flange. And a coil spring 15 provided between the coil 14 and an excitation coil 17a and a detection coil 17 provided opposite each other with the coil spring 15 interposed therebetween. The flange 14 is also a retaining ring in this example.

As shown in FIG. 8, the exciting coil 17a and the detecting coil 17 are provided so as to face each other such that the direction of the line of magnetic force passing through both coils is normal to the axial direction of the piston rod 13. . The exciting coil 17a is provided separately from the detecting coil 17 in the illustrated example, and the transmitter 1
7x, a magnetic flux (lines of magnetic force) generated by flowing a signal current of 1 to 50 KHz, for example, is wound around the piston rod 13 and the outer periphery thereof.
When the current reaches the detection coil 17 through the line 5, a minute current induced by electromagnetic induction due to the magnetic flux is detected by the detection coil 17, and a signal of the minute current is amplified and detected by the detection circuit 19.

In the position detecting mechanism, the piston rod 1
3 protrudes and changes its position, the coil spring 15 expands, the distance between the coils widens, and the exciting coil 17
a when the detection coil 17 is transmitted to the detection coil 17
Of the coil spring 15
The cross-sectional area of the magnetic material of the coil spring changes due to the expansion and contraction of the coil spring, and the inductance of the detection coil 17 changes. Therefore, a current or voltage signal in the detection coil 17 due to a predetermined high-frequency signal changes, and a change in the position of the piston rod 13 can be detected by detecting the change in the detection circuit 19.

FIG. 9 shows a result of measuring a change in the output voltage measured by the position detecting mechanism as described above. The coil spring 15 used in this measurement has a wire diameter of 0.6 mm and a coil diameter of 10 mm. The horizontal axis is the displacement of the rod, and the vertical axis is the output voltage. It can be seen that the change in the output voltage is large with respect to the change in the position of the piston rod 13 and that a characteristic with good sensitivity is obtained.

In the above embodiment, the exciting coil 17a
And the detection coil 17 are shown separately, but both coils may be integrally formed. In this case, as in the detection coil of the first embodiment, an excitation current is applied to the detection coil itself, and the magnetic flux generated by the energization is affected by the expansion and contraction of the spring coil 15 to change the inductance. The position change is measured by the detection at 19.

FIG. 10 shows a main sectional view of the seventh embodiment. This embodiment is an example in which the position detection mechanism of the sixth embodiment of FIGS. 7 and 8 is combined with the auto-tensioner of FIG. 5, and the configuration as the auto-tensioner has already been briefly described. Detailed description is omitted.

FIG. 11 shows an example of an electric circuit for performing temperature compensation. In this modification, the detection coil 17 is also used as an excitation coil, and the same coil as the other detection coil 17 is used as a temperature compensation coil 17 'in parallel with the transmitter 17x for temperature compensation. It is provided in. The detection signal from the temperature compensation coil 17 'is set to a state that has little effect on the temperature change (adjustment of the resistance r'), and is sent via the rectifier 17p and the filter 17f based on this signal. 17
The signal transmitted via the signal f is shifted by a temperature compensation system signal by an amount corresponding to a shift due to a temperature change.
Compensation by p enables accurate position detection.

[0060]

As described in detail above, the piston rod detecting mechanism of the present invention includes a detecting coil and a flange or a coil spring so as to detect the position of the piston rod of the cylinder unit. The position of the piston rod is detected continuously or in multiple points by the detection signal based on the change of the inductance coupling of the piston rod, so that the amount of protrusion of the piston rod due to the aging of the cylinder unit or the device cooperating therewith, etc. The advantage is obtained that the change can be detected and the timing for taking measures against the deterioration of the cylinder unit or the device due to aging or the like can be known in advance by a detection mechanism having a simple configuration. Similar effects can be obtained with an auto-tensioner or an electromagnetically driven valve using the detection mechanism. In addition,
If a detection mechanism is used to detect a combination of the detection coil and the excitation coil, the detection sensitivity is further improved.

[Brief description of the drawings]

FIG. 1 is a main cross-sectional view of a cylinder unit including a position detection mechanism according to a first embodiment.

FIG. 2 is a main cross-sectional view of a cylinder unit including a position detecting mechanism according to a third embodiment.

FIG. 3 is a graph showing a measurement of inductance characteristics by the position detection mechanism according to the first embodiment;

FIG. 4 is a measurement graph of inductance characteristics by a position detection mechanism according to a modification of the first embodiment.

FIG. 5 is a main cross-sectional view of an auto-tensioner provided with any one of the position detection mechanisms according to the first to third embodiments.

FIG. 6 is a main sectional view of an electromagnetically driven valve provided with any one of the position detecting mechanisms according to the first to third embodiments.

FIG. 7 is a main sectional view of a cylinder unit according to a sixth embodiment;

FIG. 8 is a perspective view of a position detection mechanism of the above.

FIG. 9 is a graph of data measured by the position detection mechanism according to the first embodiment.

FIG. 10 is a main cross-sectional view of the auto-tensioner provided with the position detecting mechanism according to the embodiment.

FIG. 11 is a diagram of a position detection circuit including a temperature compensation coil.

FIG. 12 is a front view showing a conventional belt transmission for driving a cam shaft.

[Explanation of symbols]

 10, 10 'Cylinder unit 11 Cylinder 11a, 11b End wall 12 Piston 13 Piston rod 14 Flange 15 Coil spring 16 Bobbin 17 Detection coil 19 Detection circuit A A room B B room

Continued on the front page (72) Inventor Kazuyuki Iguchi 1578 Higashikaizuka, Iwata-shi, Shizuoka F-term (reference) 2F063 AA02 BA05 DA05 GA03 KA01

Claims (13)

[Claims] 1. A detection device provided at a rod protruding side end of a cylinder so as to detect a position of a piston rod protruding from a cylinder connected to the piston, wherein the piston is inserted into a cylinder closed at both ends so as to advance and retreat. A coil and a flange provided on the piston rod facing the outer end of the detection coil, and the position of the piston rod is detected by a detection signal based on a change in inductance of the detection coil that changes with a change in the position of the flange. A piston rod position detecting mechanism configured as described above. 2. The piston rod position detecting mechanism according to claim 1, wherein a coil spring is inserted between the flange and the cylinder end. 3. The piston rod position detecting mechanism according to claim 2, wherein said flange portion is a ring made of a magnetic material. 4. The piston rod position detecting mechanism according to claim 1, wherein the flange is made of a nonmagnetic material and a conductive material ring. 5. The piston rod position detecting mechanism according to claim 1, wherein said flange portion is a pressing ring press-fitted into said piston rod. 6. A detection device provided at a rod protruding side end of a cylinder so as to detect a position of a piston rod protruding from a cylinder connected to the piston by freely inserting and retracting a piston into a cylinder closed at both ends. A coil and a coil spring mounted on the outer periphery of the piston rod and opposed to the detection coil. The coil spring is sandwiched between the cylinder and the piston rod, and the inductance of the detection coil changes with the position change of the piston rod. A piston rod position detecting mechanism configured to detect the position of the piston rod based on a detection signal based on the detected position. 7. An exciter coil is provided at the rod protruding end of the cylinder so as to face the detection coil, and is wound concentrically so that the lines of magnetic force of each coil are in the normal direction of the piston rod. The piston rod position detecting mechanism according to claim 6, wherein 8. The piston rod position detecting mechanism according to claim 7, wherein said exciting coil is formed integrally with a detecting coil. 9. The piston rod position detecting mechanism according to claim 7, wherein another pair of the exciting coil and the detecting coil are arranged to face each other. A piston is inserted into a cylinder closed at both ends so as to be able to advance and retreat, and a piston rod connected to the piston is projected from one end of the cylinder. In an auto tensioner having a pressure chamber on the side receiving a load acting on the outer end of the rod and a reservoir chamber on the opposite side, hydraulic oil is sealed between the chambers and a rod spring for urging the piston rod in a projecting direction is provided. An auto-tensioner comprising a position detecting mechanism according to any one of claims 1 to 9 provided at a protruding end of a piston rod. 11. An auto-tensioner provided with the position detecting mechanism according to claim 2, wherein a retaining ring for fixing an oil seal for closing one end of the cylinder is mounted on an inner diameter of the cylinder, and the retaining ring is attached to the retaining ring. The auto tensioner according to claim 10, wherein one end of the coil spring is abutted. 12. An auto-tensioner provided with the position detecting mechanism according to claim 2, wherein the detecting coil is mounted on a cylinder end wall via a bobbin accommodating the detecting coil, and is attached to a side wall of the bobbin. The auto tensioner according to claim 10, wherein one end of the coil spring is abutted. 13. A piston having a piston openable and retractable in a cylinder having both ends closed, a pair of electromagnetic coils provided with the piston interposed therebetween, a piston rod connected to at least one side of the piston, and an end of the piston rod connected to the cylinder end. The piston rod according to any one of claims 1 to 9, wherein the piston rod is provided so as to protrude and is configured to move the piston forward and backward by a magnetic attraction force of an electromagnetic coil so as to move the projecting end of the piston rod forward and backward. An electromagnetically driven valve comprising: a position detecting mechanism.