JP2566121B2 - Piston position detector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston position detecting device, and more particularly to a piston position detecting device for magnetically detecting the piston position of a fluid pressure cylinder.

[0002]

2. Description of the Related Art Conventionally, as such a piston position detecting device, for example, there is a magnetic proximity switch disclosed in Japanese Utility Model Publication No. 6-24722. In this magnetic proximity switch, as shown in FIG. 5, the magnetic detector 21 has two reed switches 2 having the same glass tube length and different sensitivities.
2, 23. Both reed switches 2
2, 23 are arranged such that their detection directions are parallel to the axis of the cylinder tube T of the pneumatic cylinder S that detects the piston position, and the centers of both detection ranges are aligned. As a result, the reed switch 22 having a low sensitivity has a detection range of the reed switch 2 having a high sensitivity.
3 is included in the detection range.

Then, by turning on only the reed switch 23, the LED for indicating that the piston position is within the allowable range is turned on. Further, by turning on both reed switches 22 and 23, the LED for indicating that the piston position is within the optimum range is turned on. As a result, the piston position is detected within the optimum range or the allowable range, and the detection range is displayed in a distinguishable manner.

By the way, in the piston position detecting device, it is desirable to increase the allowable range. That is, in order to reliably detect and warn a piston position out of the optimum range during use of the pneumatic cylinder S equipped with the magnetic detection switch, a somewhat large allowable range with respect to the optimum range is required. And in the above magnetic detection switch,
Reed switch 2 with equal glass tube length and different sensitivity
The allowable range is formed by the difference in the widths of the detection ranges 2 and 23. However, if the glass tubes are of equal length,
Even if there is a difference in sensitivity, there is no great difference in the detection range.
Actually, the difference between the detection ranges of the reed switches 22 and 23 having different sensitivities is about 1 mm, so the allowable range is 0.5 m.
It will be about m. As a result, only a narrow allowable range can be obtained, so that a preferable detection characteristic cannot be obtained as the piston position detecting device.

In the magnetic proximity switch disclosed in Japanese Utility Model Laid-Open No. 2-65103, as shown in FIG. 6, the magnetic detectors 24 have the same glass tube length and the contact portions are located on one end side of the glass tube. It is composed of two offset type reed switches 25 and 26 which are offset.
The contact points of the reed switches 25 and 26 are arranged on opposite sides of the magnetic detection unit 24 in the axial direction. That is, by shifting both contact portions of both reed switches 25 and 26 in the detection direction by the distance d, the detection ranges of both reed switches 25 and 26 are shifted and part of them are overlapped.

By turning on only the reed switch 25 or the reed switch 26, the LED for indicating that the piston position is within the allowable range is turned on.
Further, by turning on both reed switches 25 and 26, the LED for indicating that the piston position is within the optimum range is turned on. As a result, the piston position is detected within the optimum range or the allowable range, and the detection range is displayed in a distinguishable manner. Further, in this magnetic proximity switch, both allowable ranges are formed by shifting the pair of reed switches 25 and 26 in the detection direction. Therefore, unlike the case of the magnetic proximity switch described above,
A relatively large tolerance can be obtained.

[0007]

However, in the offset type reed switches 25 and 26 used in the magnetic proximity switch described above, it is difficult to form the detection range uniformly on both sides with respect to the contact portion, and the detection range is small. There is a characteristic that the individual reed switches 25 and 26 vary. As a result, the sizes of the optimum range and the allowable range formed by the reed switches 25 and 26 vary, and in the worst case, the allowable range may not be formed on one side.

Therefore, in order to avoid this problem, FIG.
As shown in FIG. 3, the center gap type reed switches 27 and 28, whose contact portions are provided in the center of the glass tube, are arranged such that the contact portions are displaced by the distance d in the detection direction to form the magnetic detection portion 29. I have to. The center gap type reed switch is different from the offset type reed switch in that the detection range is evenly formed on both sides of the contact portion, and therefore the allowable range is not formed. However, the size of the detection range itself of each reed switch may vary from one reed switch to another.
When the individual reed switches 27 and 28 are combined, a difference may occur in the size of the allowable range formed on both sides of the optimum range.

The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a large allowable range and to make the allowable ranges on both sides of the optimum range equal in size. It is to provide a piston position detecting device.

[0010]

In order to solve the above problems, a first reed switch having a contact portion at the center and a first reed switch having the contact portion at the center are provided.
Second reed switch having a detection range larger than that of the second reed switch, the detection range in which only the second reed switch is turned on is set as an acceptable range, Further, there is provided display means for displaying the detection ranges in which the first reed switch and the first reed switch are both turned on in different states as optimum ranges.

According to the second aspect of the present invention, the display means includes the first light emitting element which is turned on in the allowable range and the second light emitting element which is turned on in the optimum range.

[0012]

Therefore, according to the first aspect of the present invention, the first contact points are provided in the center and the detection ranges are different from each other.
Since the reed switch and the second reed switch are arranged such that the centers of their respective detection ranges coincide with each other, the detection range formed by the two reed switches can be detected only by the second reed switch. The detection range is detected by the second reed switch. Then, the detection range detected by only the second reed switch is set as the allowable range, and the detection ranges detected by the first and second reed switches are displayed as different ranges by the display means in different states. As a result, an allowable range of equal size is formed on both sides of the optimum range.

According to the invention described in claim 2, in addition to the function of the invention described in claim 1, when the piston corresponds to the allowable range, the first light emitting element is turned on, and the piston is in the optimum range. In response, the second light emitting element lights up.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment embodying the present invention will now be described with reference to FIGS.
It will be described with reference to FIG. As shown in FIG. 1, the magnetic detection unit 1 of the piston position detection device of the present embodiment is composed of a first reed switch 2 and a second reed switch 3 having detection ranges of different sizes. The detection range of the second reed switch 3 is larger than the detection range of the first reed switch 2. The two reed switches 2 and 3 are arranged parallel to the mounting surface of the magnetic detection unit 1 on the cylinder tube T in a state where the respective detection directions are parallel and the centers of the respective detection ranges are aligned. Has been done. When the piston position is within the allowable range with respect to the piston position detecting device, only the reed switch 3 is turned on. Further, when the piston position is in the optimum range, the reed switch 2 is turned on in addition to the reed switch 3. The magnetic detection unit 1 is mounted on a circuit board provided inside a case (not shown) of the piston position detection device.

Next, a detection circuit including the above-mentioned magnetic detection section will be described. As shown in FIG. 2, the reed switch 2 is provided between the power supply line (plus side input line) 4 and the ground line (minus side input line) 5, and a green L as a second light emitting element.
ED6 is connected in series. The LEDs 6 are connected with their anodes on the positive side. Also, the power line 4 and the ground line 5
The reed switch 3, the switching diode 7, and the red LED 8 serving as the first light emitting element are connected in series between and. Therefore, the series circuit including the reed switches 2 and 3 is connected in parallel. Furthermore, power line 4
A Zener diode 9 is connected between the and the ground line 5 with its anode on the negative side.

Next, the operation of the piston position detecting device constructed as described above will be described. The piston position detecting device according to the present embodiment is used, for example, with the mounting surface abutting against the outer peripheral surface of the cylinder tube T of the pneumatic cylinder S. As a result, each reed switch 2, 3
Are arranged at equal distances from the axis of the cylinder tube T. At this time, as shown in FIG. 1, both reed switches 2, 3 of the magnetic detection unit 1 are located at positions where the magnetic field of the ring-shaped magnet M attached to the outer peripheral side of the piston P arranged at a predetermined stop position is the strongest. The center of the detection range of is arranged. FIG. 1 is a schematic diagram showing the arrangement and mounting state of both reed switches 2 and 3 of the magnetic detection unit 1, and the dimensional relationship is different from the actual one.

In the pneumatic cylinder S to which the piston position detecting device is attached as described above, the moving piston P
When comes close to the piston position detecting device from one side and enters the allowable range, the magnetic field of the magnet M acts on the reed switch 3, so that the reed switch 3 is turned on as shown in FIG. As a result, a current flows through the switching diode 7 and the LED 8 via the reed switch 3, so that only the red LED 8 is turned on. Therefore, the operator can easily visually recognize that the piston position is within the allowable range.

Further, when the piston P moves in the same direction and enters the optimum range, the magnetic field also acts on the reed switch 2, so that the reed switch 2 is turned on in addition to the reed switch 3. When both the reed switches 2 and 3 are turned on, the circuit of the reed switch 3, the switching diode 7, the LED 8 and the reed switch 2 are connected between the power line 4 and the ground line 5.
-The circuit of LED6 is closed respectively. in this case,
Since the voltage drop of the switching diode 7 is sufficiently larger than the voltage drop of the LED 6, it becomes difficult for current to flow in the circuit including the LED 8. As a result, most of the current flows through the reed switch 2 to the LED 6, so that the green LED 6
Only lights up. Therefore, the operator can easily visually recognize that the piston position is in the optimum range.

Further, when the piston P moves in the same direction and enters the allowable range again, the magnetic field does not act on the reed switch 2, so the reed switch 2 remains off while the reed switch 3 remains on. As a result, the switching diode 7 and the LED 8 are again connected via the reed switch 3.
Since a current flows through the LED, only the red LED 8 lights up.
Therefore, the operator can easily visually recognize that the piston position is within the allowable range again.

Since the Zener diode 9 is connected between the power line 4 and the ground line 5, a large voltage is applied to the switching diode 7 and the LEDs 6 and 8 when the reed switches 2 and 3 are turned on. It is not applied.

As described in detail above, according to the piston position detecting apparatus of the present embodiment, it is possible to visually determine whether the piston stop position is the optimum range or the allowable range by turning on the LEDs 6, 8.

Further, according to the piston position detecting apparatus of the present embodiment, the allowable range is formed by the combination of the long reed switch 3 having a large detection range and the short reed switch 2 having a narrow detection range, so that a large allowable range is formed. can do.

Furthermore, since the centers of the respective detection ranges of the center gap type reed switches 2 and 3 having different detection ranges are made coincident with each other to form the optimum range and the allowable range, they are equal to both sides of the optimum range. Size tolerances can be formed.

Moreover, since the reed switches 2 and 3 are arranged at the same distance from the axis of the cylinder tube T (that is, the axis of the piston P), the strength of the magnetic field acting on the reed switches 2 and 3 from the magnet M is high. Are almost equal. As a result, malfunction due to the external magnetic field can be suppressed.

The present invention is not limited to the above embodiment, but may be configured as follows. (1) In the above embodiment, the reed switches 2 and 3 are arranged at the same distance from the axis of the cylinder tube T (that is, the axis of the piston P). As shown in FIGS. 4A and 4B, the magnetic detection unit 1 may be configured such that both reed switches 2 and 3 are arranged in a plane including the axis of the cylinder tube T. In this case, of the reed switch 3 with the larger detection range or the reed switch 2 with the smaller detection range,
Any of the reed switches 2 and 3 may be on the cylinder tube T side.

(2) The colors of the LEDs 6 and 8 may be the same, and the switch diode 7 may be omitted, so that both LEDs 6 and 8 are turned on within the optimum range. or,
The LEDs 6 and 8 may be a combination of colors other than green and red. For example, a combination of yellow and orange may be used.

(3) The shape of the magnet M provided on the piston P is not limited to the ring shape, but may be a semicircular shape, a cylindrical shape, a quadrangular shape or the like. (4) You may comprise so that the signal which becomes H level may be output only within an allowable range. This signal can be used as a signal to warn that the piston position has deviated from the optimum range.

(5) Instead of the LEDs 6 and 8, for example,
It is also possible to use an electroluminescent element (EL element), a light emitting element such as a liquid crystal element, and a display element to perform display in the optimum range and the allowable range.

Below, in addition to the technical idea described in the claims, the technical idea grasped in each of the above-mentioned embodiments will be described together with its effects. (1) In the piston position detecting device according to the first aspect, the first reed switch 2 and the second reed switch 3 are formed so that they can be arranged at equal distances with respect to the axis of the piston P for detecting the position. With such a configuration, malfunction due to an external magnetic field can be suppressed.

[0030]

As described above in detail, according to the invention described in claim 1, it is possible to provide a large allowable range and to make the allowable ranges on both sides of the optimum range equal in size.

According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, since the piston position is indicated by the lighting of another light emitting element, the piston position can be extremely easily determined. Can be determined.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a magnetic detection unit of a piston position detection device.

FIG. 2 is a detection circuit diagram including a magnetic detection unit.

FIG. 3 is an operation chart showing the relationship between the ON range of each reed switch and the LED lighting range.

FIG. 4A and FIG. 4B are schematic views showing another example of a magnetic detection unit.

FIG. 5 is a schematic diagram showing a magnetic detection unit of a conventional magnetic proximity switch.

FIG. 6 is a schematic diagram showing a magnetic detector of the magnetic proximity switch.

FIG. 7 is a schematic diagram showing a magnetic detection unit of a magnetic proximity switch.

[Explanation of symbols]

2 ... 1st reed switch, 3 ... 2nd reed switch, 6 ... LED as a 2nd light emitting element, 8 ... LED as a 1st light emitting element.

Claims (2)

(57) [Claims] 1. A first reed switch (2) having a contact portion in the center, and a second reed switch (3) having a contact portion in the center and having a larger detection range than the first reed switch (2). ) Are arranged so that the centers of their detection ranges coincide with each other, and the detection range in which only the second reed switch (3) is turned on is set as an allowable range, and the second reed switch (3) and the first reed switch ( The display means (6, 6) that displays the detection ranges in which both 2) are turned on as the optimum ranges in different states.
8) A piston position detection device provided with. 2. The piston according to claim 1, wherein the display means comprises a first light emitting element (8) which is turned on in an allowable range and a second light emitting element (6) which is turned on in an optimum range. Position detection device.