JP2000088508A - Stroke detecting apparatus of fluid pressure cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stroke detecting apparatus of a fluid pressure cylinder which can reduce the number of non-magnetic parts arranged in a magnetic material rod, and detect accurately the amount of movement of the magnetic material rod. SOLUTION: This stroke detecting apparatus is provided with a magnetic material rod wherein non-magnetic parts are arranged at intervals on the surface, and a magnetic sensor constituted of two magneto-resistance elements and a bias magnet which are arranged facing the magnetic material rod, and outputs a pulse signal 29 in response to a voltage output 23 generated from the magnetic sensor when the magnetic material rod and the magnetic sensor move relatively, thereby detecting the amount of movement of the magnetic material rod. The pulse signal 29 is outputted when the voltage output 23 generated from the magnetic sensor exceeds a specified value E.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic cylinder stroke detecting device for detecting a moving amount of a hydraulic cylinder.

[0002]

2. Description of the Related Art In a conventional stroke detecting device for a hydraulic cylinder, as shown in FIGS. 7 to 9, a plurality of non-magnetic portions 2 are arranged on a surface of a magnetic rod 1 at a pitch p. A magnetic sensor 3 is arranged facing the magnetic rod 1. The magnetic sensor 3 includes two magneto-resistive elements 4 and 5 arranged at a pitch (p / 2), and a bias magnet 6 that covers the magneto-resistive elements 4 and 5. These magnetoresistive elements 4 and 5 are connected as shown in FIG.

When the magnetic rod 1 crosses the magnetic sensor 3, a voltage output 7 is generated at the magnetoresistive elements 4 and 5, as shown in FIG. Is output. The amount of movement of the magnetic rod 1 can be detected by counting the number of pulses.

[0004]

However, in the above configuration, a plurality of non-magnetic portions 2 are arranged on the surface of the magnetic rod 1 at a pitch p. There is a problem in that a large number of parts 2 must be provided, which increases the processing cost.

[0005] Therefore, as shown in FIG.
Although it is conceivable to increase the pitch p1 (p1> p) at which the non-magnetic portion 2 does not exist, in this configuration, as shown in FIG. 10 occurs.

In the flat portion 10, noise is input from the outside, or the temperature changes, the resistance values of the two magnetoresistive elements vary, or the distance between the magnetic rod and the magnetic sensor changes. Due to various factors such as the above, a minute indefinite signal pulse 11 is generated.

The undefined signal pulse 11 causes the non-magnetic portion 2 of the magnetic rod 1 to move into the two magneto-resistive elements 4,
A new problem arises that one mistakes for crossing 5.

The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce the number of non-magnetic portions provided on a magnetic rod and to reduce the amount of movement of the magnetic rod. An object of the present invention is to provide a stroke detecting device for a hydraulic cylinder that can accurately detect the stroke.

[0009]

Means adopted by the present invention to solve this problem are described with reference to the reference numerals used in the embodiments. Body rod 21, two magnetoresistive elements 4, 5 and a bias magnet 6
And a magnetic sensor 3 made of
And when the magnetic sensor 3 moves relatively,
Outputs a pulse signal 29 corresponding to the voltage output 23 generated by the magnetic sensor 3, and outputs a pulse signal 29 when the voltage output 23 generated by the magnetic sensor 3 exceeds a predetermined value E. The pulse signal 29 is output every time the nonmagnetic portion 22 crosses the magnetoresistive elements 4 and 5. If the pulse signal 29 is counted, the magnetic material The moving amount of the rod 21 can be accurately detected.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. However, the same parts as those in the conventional example are given the same numbers.

In FIG. 1 to FIG. 3, the magnetic sensor 3
Pieces of magnetoresistive elements 4, 5 and these magnetoresistive elements 4, 5
And a bias magnet 6 that covers the The magnetoresistive elements 4 and 5 are arranged at a pitch (p / 2).

A magnetic rod 21 which is a movable body of a fluid pressure cylinder has a plurality of non-magnetic portions 22 arranged at equal intervals. The width of the non-magnetic portion 22 is (p / 2),
The pitch p1 is set to be larger than p {twice the pitch (p / 2) of the magnetoresistive elements 4 and 5}.

The magnetic rod 21 is arranged to face the magnetic sensor 3.

The magnetoresistive elements 4 and 5 are directly connected to the applied voltage Vcc as shown in FIG.
The voltage output 23 at the point is input to the + side of the voltage comparator 24. The voltage comparator 24 is composed of an operational amplifier, and a comparison voltage 25 is input to the minus side. Further, a pull-up resistor 26 is connected between the output side of the voltage comparator 24 and the applied voltage Vcc, and a pulse signal 29 corresponding to the voltage output 23 is output.

A resistor 27 connected to the input side of the voltage comparator 24 and a resistor 28 connected between the input and output sides of the voltage comparator 24 are shown in FIG.
Is set so as to output the pulse signal 29 when the voltage output 23 exceeds a predetermined value E. When the voltage output 23 is below E due to external noise due to external noise, the pulse signal 29 is output. This is a so-called dead zone that is not output.

In the first embodiment, when the magnetic rod 21 moves relative to the magnetic sensor 3 and the nonmagnetic portion 22 intersects the magnetoresistive elements 4 and 5,
The magnetic flux passing through the magnetoresistive elements 4 and 5 changes. As a result, the resistance of the magnetoresistive elements 4 and 5 changes and the potential at the point A changes, and a voltage output 23 having a sine waveform is generated as shown in FIG. Since this voltage is larger than E, a pulse signal 29 is output.

When the non-magnetic portion 22 (p1> p) passes through the magneto-resistive elements 4 and 5, the non-magnetic portion 22 and the magneto-resistive
The magnetoresistive elements 4 and 5 do not intersect the non-magnetic portion 22 for a while due to the difference in pitch from the non-magnetic portion 22. Therefore, the voltage output 23 becomes the flat portion 30 and the pulse signal 29 is not output.

If the indeterminate signal pulse 10 is generated by the external factors such as the above-mentioned external noise while the magnetic rod 21 is moving on the flat portion 31, the voltage input 23 caused by this is smaller than the dead zone E. Therefore, the pulse signal 29 is not output.

The magnetic rod 21 is further advanced and the non-magnetic portion 2
When 2 crosses the magnetoresistive elements 4 and 5, a voltage output 23 having a sine waveform is generated again.

As described above, in the first embodiment, the pulse signal 29 is output every time the nonmagnetic portion 22 crosses the magnetoresistive elements 4 and 5, so that the pulse signal 2
By counting 9, the amount of movement of the magnetic rod 21 can be accurately detected.

The pulse signal 29 shown by a solid line in FIG. 1 is when the magnetic rod 21 moves in the extension direction, and the pulse signal 29 shown by the dotted line is when the magnetic rod 21 moves in the contraction direction. When the pulse signal 29 is counted, the dead zone E is set.
However, since the displacement is not more than (p / 2), it does not become an error in detecting the movement amount of the magnetic rod 21.

According to the first embodiment, the non-magnetic portion 22
Can be increased irrespective of the pitch of the magnetoresistive elements 4 and 5, the number of the non-magnetic portions 22 can be reduced, and the cost can be reduced. Since the signal 29 is not output, there is no erroneous detection and the magnetic rod 21
This has the effect that the amount of movement of the object can be accurately detected.

FIG. 6 shows a second embodiment of the present invention. The difference from the first embodiment is that the pitch (interval) of the non-magnetic portion 22 provided on the magnetic rod 21 is different from that of the first embodiment. It depends on For example, p2 <p1 <p3.

The second embodiment is applied to a case where it is detected that the magnetic rod 21 has moved to a specific position, and a required number of non-magnetic portions 22 are provided in accordance with the specific position. Just do it.

The second embodiment has the same effects as the first embodiment.

[0026]

The present invention comprises a magnetic rod having a non-magnetic portion intermittently disposed on its surface, and a magnetic sensor comprising two magneto-resistive elements and a bias magnet disposed opposite to the magnetic rod. In a stroke detection device that outputs a pulse signal corresponding to a voltage output generated by the magnetic sensor when the magnetic rod and the magnetic sensor relatively move, the magnetic sensor emits the pulse signal. Since the pulse signal is output when the voltage output exceeds a predetermined value, the pitch of the non-magnetic part can be increased, so that the cost can be reduced by reducing the number of non-magnetic parts, and Even if noise is input from the outside, there is an excellent effect that the amount of movement of the magnetic rod can be accurately detected without erroneous detection.

[Brief description of the drawings]

FIG. 1 is a diagram showing a voltage output according to a first embodiment of the present invention.

FIG. 2 is a plan view of a magnetic sensor and a magnetic rod.

FIG. 3 is a front view of a magnetic sensor and a magnetic rod.

FIG. 4 is a perspective view of a magnetic rod.

FIG. 5 is a connection circuit diagram.

FIG. 6 is a front view of a second embodiment of the present invention.

FIG. 7 is a perspective view of a magnetic rod in a conventional example.

FIG. 8 is a plan view of a magnetic sensor and a magnetic rod.

FIG. 9 is a front view of a magnetic sensor and a magnetic rod.

FIG. 10 is a connection circuit diagram.

FIG. 11 is a diagram showing a voltage output.

FIG. 12 is a front view of a magnetic sensor and a magnetic rod in another conventional example.

FIG. 13 is a diagram showing a voltage output.

[Explanation of symbols]

 REFERENCE SIGNS LIST 3 magnetic sensor 4 magnetoresistive element 5 magnetoresistive element 6 bias magnet 21 magnetic rod 22 non-magnetic part 23 voltage output 24 voltage comparator 27 resistance 28 resistance 29 pulse signal 30 dead zone

Claims (1)

[Claims] A magnetic rod having a non-magnetic portion intermittently disposed on a surface thereof; and a magnetic sensor including two magnetoresistive elements and a bias magnet disposed opposite to the magnetic rod. In a stroke detection device that outputs a pulse signal corresponding to a voltage output generated by the magnetic sensor when the rod and the magnetic sensor relatively move, and detects a movement amount of the magnetic rod, the voltage output generated by the magnetic sensor is predetermined. Wherein the pulse signal is output when the value of the stroke exceeds the value of the stroke.