JPS6046641B2 - Rotation angle detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotation angle detection device that converts mechanical angular displacement into an electrical quantity using a magnetically sensitive element whose resistance value changes depending on the direction of a magnetic field.

In recent years, various control systems for automobiles do not have mechanical electrical contacts as rotation angle detection devices for detecting the opening degree of intake air metering valves and throttle valves, and therefore do not have mechanical electrical contacts. There is a growing demand for something that does not generate noise.

As a means of meeting such requirements, it is known to use a detection body in which a magnetically sensitive element is connected to a bridge as shown in FIG.

As shown in FIG. 1a, the magnetic field direction detector 4', which is composed of four terminals, consists of magnetic elements 4a, 4b, 4c, and 4d whose resistance value changes depending on the direction of the magnetic field, as shown in FIG. is connected to the bridge, and when a current I' is applied to this detecting body 4' and a magnetic field H in the direction of angle θ is applied, the phase changes at the signal output terminals M' and N' as shown in Fig. 1c. Voltage signals VM' and VN' are generated which are represented by output functions y A cos 2 θ+B which are different by 900 degrees. By changing the direction θ of the magnetic field H applied to the detection body 4' depending on the rotation angle, a voltage signal corresponding to the rotation angle can be obtained. Moreover, by using a bridge configuration, a highly accurate detection signal can be obtained with a simple configuration. However, such a detection object is not used as is, but is generally used in combination with a signal amplification circuit having an adjustment function for correcting variations in the resistance value of the magnetic element. For example, as shown in FIG.
and resistance R,′,R2′,Ra,R. It is also possible to combine a known operational amplifier circuit using '. In this circuit, the resistance values of resistors R1'', R2'', R3'', and R4'' are set to R
If 1″=, R3″, R2″=R4, the output voltage is ■.
” is represented by .

However, in order to change the amplification factor of this circuit, R1
Unless `` and R3'' or R2'' and R4'' are changed at the same rate, the above equation (1) will not hold, and it is extremely difficult to change or adjust the amplification factor in the circuit shown in FIG.

In view of the above background, the present invention uses magnetically sensitive elements arranged in a bridge as a detection object, and combines them with an amplifier circuit so that the output signal can be changed by changing only one resistor. It is an object of the present invention to provide a rotation angle detection device whose output can be easily adjusted even in response to variations in characteristics of a magnetically sensitive element. The present invention will be described below with reference to the embodiments shown in FIGS. 3 and 4.

FIG. 3 shows the basic configuration of a valve opening measuring device to which the rotation angle detecting device of the present invention is applied, and FIG. 4 shows an electrical wiring diagram. In Fig. 3, 1 is a pipe through which intake air passes;
2 is an intake air metering valve or throttle valve. 3 is a shaft made integrally with the valve 2, and a magnetic sensing part 4 is attached to the tip of this shaft.

5 and 6 are permanent magnets that apply a magnetic field to the magnetic sensing part 4.

The magnetically sensitive section 4 is composed of four magnetically sensitive elements 4a, 4b, 4c, and 4d arranged in a bridge as shown in FIG.
This is the configuration of the terminal. 41 and 42 are resistors that actively unbalance the potential difference between the two signal output terminals M and N of the bridge, and these resistors 41 and 42 and the magnetic sensing part 4 form a magnetic field direction detector.

Note that the resistors 41 and 42 may be integrated with the magnetic sensing section 4. Reference numeral 7 denotes a DC amplification circuit that amplifies the potential difference generated between the signal output terminals M and N of the magnetic field direction detector. It is composed of a resistor 7d for voltage conversion.

In this amplifier circuit 7, a potential of 9-VN is applied to both ends of the resistor 7b due to the normal operation of the operational amplifier 7a. If the resistance value of the resistor 7b is R1, then the resistor 7b
Current 1 flowing through. is I. =(■9-VN)/R1. In this embodiment, due to the resistors 41 and 42, ■M≧
(2) Since it is N, this current 10 flows from the inverting input terminal of the operational amplifier 7a toward the signal output terminal N of the magnetically sensitive section 4. Generally, the input impedance of an operational amplifier is large, so this current 1. is mostly NPN transistor 7c
is supplied through the emitter of Therefore, by increasing the current amplification factor of this NPN transistor 7c, the voltage drop across the collector resistor 7d of the NPN transistor 7c is reduced to 1 current. and the resistance value of the collector resistor 7d. In other words, the output voltage of the amplifier circuit 7 is ■.

It is represented by a dot.

As is clear from equation (2), in order to adjust the amplification factor for the potential difference (VM-VN), the resistor 7b (R1
) or by adjusting the resistor 7d (R2). By the way, in the above configuration, when a current 1 is passed through the magnetic field direction detector, output voltages M and VN are generated at the signal output terminals M and N according to the direction θ of the magnetic field applied to the magnetic sensing part 4, but the bridge resistors 41, 4 in diagonal relation to each of the current paths of
2 is connected, and by selecting a relatively large resistance value, the relationship between the output voltages VM and VN is always ■9≧VN
It is.

Therefore, in the amplifier circuit 7, since the direction of the potential difference between the voltage difference 9 and the voltage VN, that is, positive and negative, is determined, the amplification factor can be changed simply by adjusting either one of the resistors 7b and 7d independently. Various methods can be considered to simply unbalance the output voltages M and VN of the magnetically sensitive section 4, but in order to maintain the relationship of y=ACOS2O+B, which is the output characteristic of the magnetically sensitive section, The amount of unbalance between M and VN must be increased to some extent, and the currents 1M and IN flowing through the two current paths of the bridge must be made equal.

This makes the output amplitudes of the output voltages ■M and ■N almost the same, and also generates fluctuations due to temperature, etc., and the operational amplifier 7a
This is to offset the Therefore, as shown in FIG. 4, it is necessary to insert resistors 41 and 42 of substantially equal size in diagonal relation with each other in the bridge. As described above, in the present invention, the signal output terminal of the bridge is connected by a combination of a magnetically sensitive element having a bridge configuration that detects the direction of a magnetic field, and a first resistor connected to both opposing sides of the bridge. It is possible to generate a desired potential difference with a gradient always in the same direction depending on the resistance value of the magnetically sensitive element between the two terminals, and one connected to one side of the signal output terminal.
Since the voltage-to-current conversion circuit includes an operational amplifier that can change the amplification factor by simply adjusting two second resistors, there is no need to consider the potential direction of the bridge output. If the circuit can be realized with a simple configuration using a single power supply, and there are variations in the output characteristics of the bridge, the output of the conversion circuit can be easily adjusted by adjusting the resistance values of this second resistor and the first resistor. It has the great effect of making it possible.

In the case of the above-mentioned embodiment, the resistors 41 and 42 were inserted so that VM≧VN, but when the resistors 43 and 44 were inserted in the opposite diagonal relationship as shown in FIG. 5, ■9≦VN. However, in this case, if the transistor 7c is a PNP transistor and the resistor 7d is connected between the collector and ground of the transistor 7c, the same function as in the previous embodiment can be obtained.

Further, a Darlington transistor may be used as the transistor 7c to obtain a large current amplification factor.

[Brief explanation of drawings]

Figures 1A, 1B, and 1C are explanatory diagrams showing the external appearance, internal electrical connections, and output characteristics of a conventionally known magnetic field direction detector, respectively.
The figure is an electrical wiring diagram showing a rotation angle detection device configured using a conventionally known magnetic field direction detection body based on a conventional concept, and Figure 3 shows the valve opening to which the rotation angle detection device of the present invention is applied. A configuration diagram showing an example of a measuring device, FIG. 4 is an electrical wiring diagram showing one embodiment of the rotation angle detection device according to the present invention, and FIG. 5 shows another embodiment of the rotation angle detection device according to the present invention. It is an electrical wiring diagram. 1...Air passage, 2...Valve, 3...
... Rotating shaft, 4... Magnetic sensing part, 4a, 4b, 4c, 4d
... Magnetically sensitive elements arranged in the bridge, 5, 6...
...Permanent magnet forming a magnetic field source, 7...DC amplifier circuit, 7a...゜operational amplifier, 7b...
・Resistance, 7c...Transistor, 41, 42, 4
3, 44...Resistor forming a magnetic field direction detection body with the magnetic sensing part 4, M, N...Signal extraction terminal.

Claims (1)

[Claims] 1 Magnetically sensitive elements whose resistance value changes depending on the direction of the applied magnetic field are arranged in a bridge strip, and a first resistor is connected to each opposing side of the bridge,
A magnetic field direction detector configured to generate a desired potential difference between two signal output terminals of the bridge in accordance with the resistance value of the magnetically sensitive element and always having a gradient in the same direction, this magnetic field direction detector, and this magnetic field. means for relatively changing the angular relationship between at least the bridge portion of the direction detecting body and the direction of the magnetic field generated by the magnetic field source according to the rotation angle; and a voltage-to-current conversion circuit for converting the current into a current, and the voltage-to-current conversion circuit includes an operational amplifier having first and second input terminals, the output of which is fed back to the first input terminal. A rotation angle detection device characterized in that an input terminal is connected to one of the signal output terminals via a second resistor, and the second input terminal is connected to the other of the signal output terminals.