JPS63217202A - Noncontact type potentiometer - Google Patents

Abstract

PURPOSE:To obtain a high-accuracy detection signal even in an atmosphere where temperature variation is large by setting output voltage characteristics of a couple of magneto-resistance elements which constitute a magnetic detecting element into opposite states according to the variation in temperature and compensating them mutually. CONSTITUTION:A moving body 11 constituted including a magnet is set as a body to be detected. Then the intensity of a magnetic field which operates on 1st and 2nd magneto-resistance elements(MR) 12 and 13 varies according to the displacement caused by the movement of the moving body 11 and their resistance values vary respectively corresponding to it. Further, the resistance variation rates of the MRs 12 and 13 have a negative temperature coefficient -alpha. Then the output voltage from an output terminal 14 varies with temperature unless temperature correction is performed, so 1st and 2nd constant voltage circuits 15 and 16 are given temperature coefficients alpha/2 and -alpha/2 respectively. Thus, variation in the deviation quantity of the output voltage from the terminal 14 with the variation quantity of the moving body 11 is eliminated. Further, the temperature coefficients of the circuits 15 and 16 are set opposite to each other and their neutral point potential does not vary and becomes constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a non-contact potentiometer that can obtain an output signal corresponding to a position and is used, for example, as a position detection device for a moving object.

[Prior Art] For example, a non-contact type potentiometer is used to configure a position detection device, and it is considered that this potentiometer can be configured using, for example, a magnetoresistive element. That is, a magnet member is set as a moving object that is displaced, and a detection element using a magnetoresistive element is set so as to be brought close to the position where the magnet member moves. Then, as the magnet member moves, changes in resistance due to changes in the magnetic field strength acting on the magnetoresistive element are detected, and an electrical signal corresponding to the amount of displacement of the magnet member is obtained. be.

However, the magnetoresistive element used as the detection element has temperature characteristics. Therefore, even when a magnetic field of the same strength is applied, the resistance value of the magnetoresistive element changes as the temperature changes, making it impossible to obtain a highly accurate position detection signal. Therefore, for example, in order to improve the control accuracy of an automatic control device using such a position detection means, a complicated temperature correction means is required.

[Problems to be Solved by the Invention] The present invention has been made in view of the above points, and uses a magnetoresistive element having temperature characteristics as a detection element, while making sure that the output characteristics do not have temperature characteristics. The purpose of this invention is to provide a non-contact type potentiometer.

[Means for Solving the Problems] That is, in the non-contact potentiometer according to the present invention, the magnetic detection element is constituted by a pair of magnetic resistance elements formed into a half bridge, for example. A moving member constituted by a magnetic member is set along the element. The detection output signal is taken out from the connection point of the pair of magnetoresistive elements, and each of the pair of magnetoresistive elements has a first and a first temperature coefficient set to have positive and negative temperature coefficients, respectively. The voltage is supplied from the constant voltage circuit No. 2.

[Function] In the non-contact potentiometer configured as described above, the output voltage characteristics from the pair of magnetoresistive elements constituting the magnetic detection element are set to opposite states as the temperature changes. It becomes like this. Therefore, the output characteristics compensate each other, and as a result, the output signal from the magnetic sensing element has no temperature characteristics, and the potentiometer provides an output signal that is unaffected by temperature changes. This is what happens.

[Embodiments of the invention] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows its configuration, in which a moving body 11 including a magnet is set as a moving detection body. First and second magnetoresistive elements (MR) 12 and 13 are set along the moving direction of the moving body 11 shown by the arrow, and as the moving body 11 moves,
This moving body 11 is successively set to face the magnetoresistive elements 12 and 13.

The first and second magnetoresistive ropes 12 and 13 are
For example, they are configured as a half-bridge and are connected in series with each other. Then, the output terminal 14 is connected to that connection point.

Power is supplied to the first magnetoresistive element 12 via a first constant voltage circuit 15, and power is supplied to the second magnetoresistive element 13 via a second constant voltage circuit 16. I'm trying to make it happen. In this case, the first constant voltage circuit 15 is configured to have a positive temperature coefficient, and the second constant voltage circuit 1B is configured to have a negative temperature coefficient.

In the potentiometer configured in this way, the strength of the magnetic field acting on the first and second magnetoresistive ropes 12 and 13 changes in response to the displacement caused by the movement of the moving body 11, and The resistance value changes depending on the magnetic field strength.

Therefore, an output voltage signal corresponding to the change in resistance value can be obtained from the output terminal 14 to the moving body 1.
An output voltage signal corresponding to position 1 is now output.

Assuming that a potentiometer using such a magnetoresistive element is used in a wide temperature environment, the rate of change in resistance of the magnetoresistive element has a negative temperature coefficient -α as shown in Figure 2. (-3000~3500PPM/'C
) exists.

Therefore, unless temperature correction is performed, the output voltage obtained from the output terminal 14 will change depending on the temperature.

Therefore, the first constant voltage circuit 15 has "α/2".
Furthermore, the second constant voltage circuit 16 is made to have a temperature coefficient of "-α/2".

Therefore, the voltage applied to the first and second magnetoresistive elements 12 and 13, that is, the voltage between points and 5, is the temperature characteristic of the resistance change rate of the magnetoresistive element "-α" indicated by A in FIG. A temperature coefficient of "α" as shown by B is now set, which cancels out "." Therefore, the amount of displacement of the output voltage from the output terminal 14 with respect to the amount of displacement of the moving body 11 does not change depending on the temperature.

Further, the first and second constant voltage circuits 15 and 16
Since the temperature coefficient of is set to be exactly opposite,
The midpoint potential remains constant without changing depending on the temperature, as shown by the broken line in FIG.

In other words, this means that the midpoint position of the output voltage signal from the output terminal 14 does not change with temperature, and furthermore, considering that the amount of voltage displacement does not change with temperature, the above embodiment It will be appreciated that with the non-contact potentiometer shown, the sensed output voltage signal is not affected by temperature changes.

In the description of the above embodiment, it is assumed that the resistance value ratio of the first and second magnetoresistive elements 12 and 13 is "1:1", but this resistance ratio is rl :a
J, the temperature coefficients of the first and second constant voltage circuits 15 and 16 are set to [α/(1+a)J and α・a/(1+a)J, respectively.
A potentiometer without this temperature characteristic can be used.

[Effects of the Invention] As described above, according to the non-contact potentiometer according to the present invention, even if the magnetoresistive element used as a detection element has temperature characteristics, the output voltage signal from this potentiometer does not have temperature characteristics. The present invention eliminates the existence of a high-precision detection signal even in an atmosphere with rapid temperature changes, and effectively expands its range of applications.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram illustrating a non-contact potentiometer according to an embodiment of the present invention, FIG. 2 is a diagram showing the temperature characteristics of a magnetoresistive element used in the potentiometer, and FIG.
The figure is a diagram illustrating the relationship between the resistance change rate and temperature of the magnetoresistive element in the above embodiment, and FIG. 4 is a diagram illustrating the output voltage characteristics of the potentiometer. DESCRIPTION OF SYMBOLS 11... Moving object (magnet), 12... 1st magnetoresistive element, 13... 2nd magnetoresistive element, 14...
- Output terminal, 15... first constant voltage circuit (positive temperature coefficient), 1B... second constant voltage circuit (negative temperature coefficient). Applicant's Representative Patent Attorney Takeshi Suzue 3rd Part 1 Figure 3.

Claims (1)

[Claims] Magnetic detection means constituted by at least one pair of magnetoresistive elements set in series; and a direction in which the magnetic resistance elements are arranged in proximity to the pair of magnetoresistive elements constituting the magnetic detection means. a moving member configured to include a magnetic member that is moved by the magnet, and first and second constant voltage circuits that respectively supply voltage signals to the pair of magnetic detection means, The output signal is taken out from the connection point of the magnetoresistive element, and the first and second constant voltage circuits are set to have positive and negative temperature coefficients. Non-contact potentiometer.