JPH01170801A - Piston position detector for hydraulic cylinder - Google Patents

Abstract

PURPOSE:To visually confirm the position range of a piston by detecting the magnetic field of a permanent magnet attached to the piston by a first voltage comparator where a high reference voltage is set and a second voltage comparator where a low reference voltage is set. CONSTITUTION:A nonmagnetic piston 2 is fitted into a nonmagnetic cylinder tube 1, and an annular permanent magnet 3 is fitted to the groove of the piston 2. When the piston 2 approaches a piston position detector 4 and the magnetic field of the magnet 3 which acts upon a magnetic sensor 6 is stronger, the electric resistance of a magnetic resistance element 6b is reduced and the voltage at a middle point (a) rises. When this voltage exceeds a reference voltage at a connection point (c) of voltage dividing resistances, the output of a second voltage comparator 10 goes to the turn-on level and a detection signal is issued from a switch operation output terminal 15. When the piston 2 approaches the detector 4 furthermore and the voltage at the middle point (a) exceeds a reference voltage at a connection point (b), the output of a first voltage comparator 9 goes to the turn-on level to light a light emitting diode 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a piston position detection method that is attached to the outside of a cylinder tube of a fluid pressure cylinder such as an air cylinder or a hydraulic cylinder and detects the approach of a piston within the cylinder tube using a magnetic sensor. Regarding equipment.

Prior Art and Problems to be Solved by the Invention Conventionally, this type of piston position detection device is fixed to the outer periphery of a cylinder tube at a position that correctly corresponds to the piston at a predetermined position within the cylinder tube. In order to generate a detection output when approaching a certain range of The detection sensitivities of the magnetic sensors are adjusted equally, and this detection device is slid on the cylinder tube in the direction of movement of the piston, and when the outputs of both voltage comparators are both at the ON level, the light emitting diode By lighting up, it is confirmed that the permanent magnet of the piston is within a certain optimum range centered on the midpoint between the two magnetic sensors, the detection device is fixed at that position, and one of the voltage comparators is When the output of the LED becomes ON level, a detection output is generated or other light emitting diodes are turned on.

However, when two magnetic sensors are used in this way, the circuit becomes complicated and large, which increases the cost.Also, it is necessary to adjust the sensitivity of both sensors to be equal, which increases the adjustment cost and reduces the circuit. The disadvantage is that it consumes a lot of power and is uneconomical.

Means for Solving the Problems The present invention provides a magnetic sensor that generates an output corresponding to the strength of the magnetic field formed by a permanent magnet attached to the piston. and a first voltage comparator with a high reference voltage set and a second voltage comparator with a low reference voltage, which are connected to the magnetic sensor, respectively.

Functions and Effects of the Invention The present invention has the above configuration, and as the piston to which the permanent magnet is attached approaches, the output of the magnetic sensor gradually increases.
When the output exceeds the reference voltage of the second voltage comparator, its output terminal becomes ON level, and when the piston approaches further and the output of the magnetic sensor exceeds the reference voltage of the first voltage comparator, its output terminal also becomes ON level. For example, by connecting the output terminals of the first and second voltage comparators to two light emitting diodes with different colors, it is possible to visually determine the range in which the piston is located. Alternatively, by connecting these output terminals to a sequencer, two-step control can be performed as the piston approaches.Since only one magnetic sensor is required, the circuit is small and simple. In addition, the adjustment cost is reduced because there is no need to adjust the sensitivity of the magnetic sensor, and the circuit consumes less power and is economical.The detection device is a DC 2-wire type. In case,
There is an effect that the leakage current when OFF is small, and it is easy to distinguish between ON and OFI.

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings.

A piston 2 made of a non-magnetic material is tightly and slidably fitted into a cylinder dupe 1 made of a non-magnetic material such as aluminum or stainless steel, and a ring-shaped permanent groove is inserted into a groove formed in the center of the outer periphery. A magnet 3 is fitted, and a magnetic sensor 6 and a control circuit 7 are housed in a case 5 made of non-magnetic material such as synthetic resin on the outer periphery of the cylinder duplex I. A piston position detecting device 4 of the present invention, in which the head of the door 8 protrudes from the upper surface of the case 5, is fixed by a fastener (not shown).

As shown in FIG. 2, the magnetic sensor 6 has a magnetic resistance element 6b whose electrical resistance decreases in accordance with the strength of the magnetic field formed by the permanent magnet 3, and the magnetic sensor 6 has a different mounting direction, so that the magnetic field of the permanent magnet 3 is A magnetic resistance element 6a for compensating temperature 5, which is not sensitive, is connected at the midpoint &, and the midpoint a is connected to the non-inverting input terminal of the first and second voltage □ comparators 9.10 of the control circuit 7. are connected to each other. 11. +2.13 is connection point b1 c
3 voltage dividing resistors connected in series with power supply line 1
The connection point C on the power line +6 side is connected to the inverting input terminal of the first voltage comparator 9, and the connection point C on the ground line 17 side is connected in parallel with the magnetic sensor 6 between 6 and the ground line I7. are respectively connected to the inverting input terminal of the second voltage comparator IO,
The output terminal of the second voltage comparator 10 is connected to the switch operation output terminal 15, and the light emitting diode 8 is connected between the output terminal of the first voltage comparator 9 and the ground line 17.

The present embodiment has the above-described configuration, and when the piston 2 gradually approaches the piston position detection device 4 and the magnetic field of the permanent magnet 3 acting on the magnetic sensor 6 gradually becomes stronger, the electric resistance of the magnetic resistance element 6b on the power line 16 side increases. decreases and the voltage Va at midpoint 1
increases by 1 as shown in Figure 1 (2), and the voltage dividing resistor 11,
12, +3 exceeds the reference voltage Vc at the connection point C on the ground wire 17 side, the output of the second voltage comparator IO becomes ON level, a detection signal is emitted from the switch operation output terminal 15, and the piston 2 becomes closer and the voltage at the midpoint 1 exceeds the reference voltage vb at the connection point on the power line 16 side of the voltage dividing resistor 11, 12, 13, the output of the first voltage comparator 9 also turns ON.
level and the light emitting diode 8 lights up.

Therefore, when the piston 2 is fixed at a predetermined position, the piston position detection device 4 is connected to the cylinder tube 1.
When the piston 2 is moved in the direction of movement of the piston 2 and fixed at the position where the light emitting diode 8 lights up, the detection device 4 is set at the optimum position approximately in the center of the detection range, and the output terminal I5 is set at the optimal position. By connecting to a sequencer (not shown), the approach of the piston 2 can be output as a signal, and the fact that the piston 2 is in the optimum position can be visually confirmed by lighting the light emitting diode 8.

In the above embodiment, the light emitting diode 8 and a light emitting diode having a different color are connected between the output terminal of the second voltage comparator 10 and the ground line I7, and when this light emitting diode is turned on, the light emitting diode 8 is turned off. It may also be a configuration.

In the above embodiment, a three-wire system consisting of a power line, a ground line, and an output line is used, but two load circuits with different load voltages are connected in parallel between the power line and the ground line, and the two voltages are compared. It is also possible to use a DC two-wire system in which the two load circuits are closed separately by the output of the device, thereby changing the voltage of the power supply line and taking it out as an output.

[Brief explanation of the drawing]

FIG. 1 (1) is a sectional view of an embodiment of the present invention, and FIG. 1 (2) is a sectional view of an embodiment of the present invention.
is a diagram showing the voltage change at the midpoint a of the magnetic sensor 6;
3) and (4) are diagrams showing output changes of the first and second voltage comparators 9 and IO, and FIG. 2 is a circuit configuration diagram of this embodiment. 1 Nijilinda tube 2: Piston 3: Permanent magnet
4: Piston position detection device 5: Case 6: Magnetic sensor 7・Control circuit 8: Light emitting diode 9, IO = voltage comparator 11, 12.13: Voltage dividing resistor 15: Output terminal

Claims (1)

[Claims] A magnetic sensor that generates an output of a magnitude corresponding to the strength of a magnetic field formed by a permanent magnet attached to a piston; a first voltage comparator connected to the magnetic sensor and having a high reference voltage; A piston position detection device for a fluid pressure cylinder, comprising a second voltage comparator set to a low value.