JPH0445090B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a rotation detection device using a semiconductor magnetoresistive element, which simultaneously outputs a main signal and a sub-signal having a phase difference of 90 degrees in electrical angle, for example. The present invention relates to a rotation detection device capable of detecting rotation.

[Prior art]

Conventionally, this type of two-phase rotation detection device is provided with a gear made of a magnetic material and a permanent magnet, and tooth shapes are spaced apart by a predetermined distance with respect to the rotation direction of the gear according to equation (1) described later. first and second detection means each consisting of a pair of magnetoresistive elements arranged to face each other; and first and second thresholds for setting a threshold level of a detection signal output from each of the detection means. The distance between the first and second detection means will be described later (2).
The first and second detection means have a configuration in which a pair of magnetoresistive elements are connected in series, with the intermediate position serving as an output terminal, and the terminals to which voltage is applied are connected in parallel. It's summery. When the gear rotates, the resistance value of the magnetic resistance element facing the tooth tip becomes large, and the resistance value of the magnetic resistance element facing the tooth bottom or tooth groove becomes small. Magnetoresistive elements are connected in series, a voltage is applied, and an output voltage close to a sine wave is derived from each detection means. Then, in order to shape the waveform of this output voltage and make it into a pulsed main signal and sub-signal,
The threshold level is set as a reference voltage by each threshold level setting means, and the output voltage from the first and second detection means and the reference voltage are respectively input to each comparison means. ing.

[Problem that the invention seeks to solve]

By the way, in most of the conventional techniques, the threshold level set by each threshold level setting means is set based on the DC voltage level of each detection means at room temperature. Here, the DC voltage level refers to the voltage at the center of the voltage amplitude of the output voltage output from each detection means, that is, the intermediate voltage of the full amplitude voltage.

However, as a characteristic of the magnetoresistive element, the amplitude characteristic at high temperature is smaller than the amplitude characteristic at low temperature. In addition, the amount of crossover with the magnetic flux differs for each magnetoresistive element due to the angle at which the magnetoresistive element is attached to the gear. The DC voltage level tends to be higher than the average voltage, and conversely, the DC voltage level of the second detection means located on the rear side with respect to the rotational direction of the gear tends to be lower than the average voltage.

As a result, if the threshold level is set as the DC voltage level of each detection means at room temperature, the pulse width of the pulse signal output from the comparison means will change due to changes in the outside temperature, and the pulse duty will be reduced. As a result of fluctuations in
There was a problem in that highly accurate rotation detection was not possible.

The present invention was made in view of the problems of the prior art, and provides a rotation detection device that corrects the temperature characteristics of a magnetoresistive element and enables highly accurate rotation detection over a wide range from low to high temperatures. Our goal is to provide the following.

[Means for solving problems]

In order to solve the above problems, a rotation detection device according to the present invention is provided on a gear made of a magnetic material and a permanent magnet, and is provided at a distance of 1/2 of the pitch P of the tooth profile of the gear with respect to the rotation direction of the gear. first and second detection means each consisting of a pair of magnetoresistive elements spaced apart and facing the tooth profile; a first detection means for setting a threshold level of a detection signal output from each detection means; and a second threshold level setting means, and the distance W between the first and second detection means is W=2n-1/with respect to the pitch P of the tooth profile with respect to the rotational direction of the gear. 4×P However, n is set to an integer, and the first and second detection means have a pair of magnetoresistive elements connected in series, with the intermediate position serving as an output terminal, and the terminals to which voltage is applied being connected in parallel. It is now connected to

The feature of the configuration adopted by the present invention is that the threshold level set by the first and second threshold level setting means is determined by the change in the DC voltage level of the detection signal by the first and second detection means. This is because each temperature-sensitive element is used to set a value that is approximately equal to the characteristic value that varies depending on the temperature.

[Effect]

With this configuration, when the gear rotates, the first and second detection means output a detection signal having an output voltage close to a sine wave centered approximately at 1/2 of the applied voltage. At this time, the magnetic resistance elements constituting the first and second detection means have a characteristic that the amplitude characteristics at high temperatures are smaller than the amplitude characteristics at low temperatures; In the first detection means located at tends to be lower than the average voltage.

However, the threshold hold level set by the first and second threshold level setting means is
Since the DC voltage level of the detection signal by the first and second detection means is set to a value approximately equal to the characteristic value when it fluctuates due to temperature change, respectively, using a temperature sensing element, the first and second detection means It is possible to reduce the variation in pulse width between the detection signal output from the means at high temperatures and the detection signal output at low temperature after converting it into a pulse wave, and it is possible to eliminate the influence of temperature changes. Become.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to FIGS. 1 to 10.

1 to 8 show a first embodiment of the present invention. In FIGS. 1 and 2, 1 is a gear consisting of an involute gear, and the gear 1 has tooth profiles 1A, 1A, …have. Reference numeral 2 denotes a rotation sensor according to this embodiment, and the rotation sensor 2 includes a permanent magnet 3 that applies a magnetic bias, and a magnetized surface on the north pole side of the permanent magnet 3 with a predetermined dimension W ₁ and facing the tooth profile 1A. The detector is comprised of first and second detection units 4 and 5. Here, each of the detection units 4 and 5 is composed of two magnetoresistive elements 4A and 4B, and 5A and 5B, and the distance between the magnetoresistive elements 4A and 4B and between 5A and 5B is a predetermined dimension l, which will be described later. and this is 4A→4B→5 in the rotation direction R of gear 1.
They are installed in the order of A → 5B.

Then, if the pitch in the pitch circle of the gear 1 (the pitch in the tip circle is also acceptable) is P, then in order for the output voltage from each detection section 4, 5 to reach the maximum output, the magnetic resistance elements 4A and 4B The distance l between 5A and 5B is set by the following equation (1).

l=P/2...(1) Also, the output voltage from each detection section 4, 5 is π/2
In order to have a phase difference of
The distance W between 5 is 1/4×P, 3/4×P,
All you have to do is set it like 5/4×P,...
The general formula is set by the following formula (2).

W=2n-1/4×P...(2) However, n is an integer.In the present embodiment shown in FIG. 1, when n=2 in equation (2), The separation dimension W ₁ is set as W ₁ = 3/4×P (2)′.

Next, in each of the detection units 4 and 5, as shown in FIGS. 2 and 3, each magnetoresistive element 4A and 4B, 5A and 5B are connected in series, and the series connection is connected to a power terminal 6 and a ground terminal 7. The input voltage Vin is applied from the power supply terminal 6 to the terminals 6 and 6, which are connected in parallel between them. As a result, output voltages Vout4 and Vout5 are outputted from output terminals 8 and 9 between magnetoresistive elements 4A and 4B and between 5A and 5B with a phase difference of 90 degrees as shown in FIG. There is.

However, each magnetoresistive element 4A, 4B, 5A, 5
Since B has the characteristic that the element sensitivity decreases as the temperature rises, the total amplitude voltage V ₀ (see Figure 4) between the peaks of the output voltages Vout4 and Vout5 is
As shown in the figure, it has a temperature characteristic such that the higher the temperature, the smaller the total amplitude.

On the other hand, in the relationship between the gear 1 and the rotation sensor 2 as shown in FIG.
Since A and 5A face tooth profile 1A at almost right angles,
Although the amount of magnetic flux crossover increases, since the upper and lower magnetoresistive elements 4A and 5B in the figure obliquely face the tooth profile 1A, the amount of magnetic flux crossover is small. As a result, the output voltage
DC voltage level of Vout4, Vout5 (voltage at the center of voltage amplitude of output voltage) Vout4 _DC , Vout5 _D
C exhibits temperature characteristics as shown in FIG. That is,
The DC voltage level Vout4 _DC of the first detection unit 4 is
Average voltage of input voltage Vin applied to power supply terminal 6
The DC voltage level of the second detection unit 5 is slightly higher than Vin/2, and has the characteristic that the voltage decreases as the temperature increases.
Conversely, Vout5 _DC has a characteristic that it is slightly lower than the average voltage Vin/2 of the input voltage Vin, and that the voltage increases as the temperature increases.

Therefore, the threshold level is set based on the DC voltage level Vout4 _DC , Vout5 _DC at normal temperature (or room temperature), and the output voltage Vout4,
Compared to Vout5, a large deviation occurs on the high temperature side or low temperature side, making it impossible to perform appropriate signal processing.

Therefore, in this embodiment, a signal processing circuit shown in FIG. 7 is used.

That is, in FIG. 7, 10 and 11 are first and second threshold level setting circuits, and the first threshold level setting circuit 10 has a resistor R ₁ , a resistor R ₂ , and a thermistor Th _{1 .} The series connection is connected between the power supply terminal 6 and the earth terminal 7,
A set voltage V _T10 , which will be described later, is output from the output terminal 12 between R ₁ and resistor R ₂ . On the other hand, the second threshold level setting circuit 11 has a resistor R ₃ , a thermistor Th ₂ , and a resistor R ₄ connected in series in this order.
It is constructed by inserting the series connection between the power supply terminal 6 and the ground terminal 7, and the set voltage, which will be described later, is generated from the output terminal 13 between thermistor Th ₂ and resistor R ₄ .
Output V _T11 . and the thermistor Th ₁ ,
Th ₂ is a specific example of the temperature sensing element of the present invention.

Here, the first threshold level setting circuit 10 has a resistor on the high voltage side across the output terminal 12.
R ₁ is provided, resistor R ₂ and thermistor on the low voltage side
The configuration is such that Th ₁ is connected in series, and the thermistor Th ₁ has a characteristic that its resistance is high at low temperatures and low at high temperatures, so the voltage level set at low temperatures is high at low temperatures (room temperature).
It outputs V _T10L , which gradually decreases as the temperature rises, and at high temperatures it outputs the high temperature setting voltage V _T10H (see Figure 8a). Therefore, the voltage set by the first threshold level setting circuit 10
V _T10 is the DC voltage level detected by the first detection unit 4
Characteristics similar to those of Vout4 _DC (see Fig. 6) can be obtained, and the relationship can be set as V _T10 ≒ Vout4 _DC (3).

On the other hand, the second threshold level setting circuit 11 has a resistor connected to the high voltage side across the output terminal 13.
R ₃ and thermistor Th ₂ are provided to provide resistance on the low voltage side.
Since the configuration is such that R ₄ is provided, the voltage level is low at low temperatures (room temperature).
It outputs V _T11L , which gradually increases as the temperature rises, and when the temperature is high, it outputs the high temperature setting voltage V _T11H (see Figure 8b). Therefore, the voltage set by the second threshold level setting circuit 11
V _T11 is the DC voltage level detected by the second detection unit 5
Characteristics similar to those of Vout5 _DC (see Fig. 6) can be obtained, and the relationship can be set as V _T11 ≈Vout5 _DC (4).

Further, reference numerals 14 and 15 are first and second comparison circuits each consisting of, for example, an operational amplifier, and the first comparison circuit 14
When the non-inverting input terminal side is connected to the output terminal 8 and the inverting input terminal side is connected to the output terminal 12, and the level of the output voltage Vout4 is higher than the set voltage V _T10 ,
The main signal is output as a pulse from the output side. On the other hand, the second comparator circuit 15 also has its non-inverting input terminal side connected to the output terminal 9 and its inverting input terminal side connected to the output terminal 13, so that when the level of the output voltage Vout5 is higher than the set voltage V _T11 , the sub-signal is output from the output side. is output as a pulse.

The present embodiment is configured as described above, and its operation will be described next.

As is clear from the characteristics shown in FIGS. 5 and 6, on the detection unit 4 side, at low temperatures or room temperature, the characteristics shown in FIG.
The output voltage becomes _Vout4L as shown in FIG. 2, whereas at high temperature the output voltage becomes _Vout4H and becomes low. Similarly, on the detecting unit 5 side, the output voltage _Vout5L is shown in FIG. 8b at low temperature or room temperature, whereas
At high temperatures, the output voltage becomes _Vout5H and becomes high.

However, the DC voltage level of the first detection unit 4
Since Vout4 _DC and the set voltage V _T10 of the threshold level setting circuit 10 have a relationship as shown in equation (3), as _shown in FIG. Output voltage Vout
The pulse widths due to 4 _L and Vout 4 _H are t ₁ and t ₂ , respectively, and the DC voltage level at room temperature is
Vout4 Output voltage Vout that is output based on _DC
Compared to the pulse widths t ₁ ′ and t ₂ ′ of Vout 4 _L and Vout 4 _H , fluctuations in pulse width can be almost completely eliminated.

Furthermore, since there is a relationship between the second detection section 5 and the threshold level setting circuit 11 as shown in equation (4), the set voltage is as shown in FIG. 8b.
The pulse widths due to the output voltages Vout5 _L and Vout5 _H output from the comparator circuit 15 using V _T11 as a reference are t ₃ and t ₄
Therefore, compared to the pulse widths t ₃ ′ and t ₄ ′ due to the DC voltage level Vout5 _DC at room temperature as in the conventional technology,
Fluctuations in pulse width can be almost completely eliminated.

In this manner, this embodiment can output a rotation detection signal with no fluctuation in pulse duty without being affected by changes in outside temperature, so that highly accurate rotation detection can be performed over a wide temperature range.

Next, FIGS. 9 and 10 show a second embodiment of the present invention, in which the same components as in the first embodiment regarding the rotation sensor are marked with a dash (') and their explanation will be omitted.

However, the feature of this embodiment is that the rotation direction R of the gear 1
On the other hand, the magnetoresistive elements of the detection parts 4' and 5' are set to 4.
They are arranged in the order of A' → 5A' → 4B' → 5B', and the distance l between the magnetoresistive elements 4A' and 4B', and between 5A' and 5B' is set to P/2 as in equation (1). In addition, the distance W ₂ between the detection parts 4' and 5' is set to W ₂ = 1/4 x P ... (2)''. This equation (2)' is In the above-mentioned equation (2), this is the case where n=1.

Although the present embodiment is constructed as described above, there is no difference from the first embodiment except that the shape of the rotation sensor 2' can be made smaller, so a description of its operation will be omitted.

Incidentally, in each embodiment of the present invention, a spur gear is illustrated as the gear 1, but the gear 1 is not limited to this, and a rack gear, an internal gear, etc. may also be used. In addition, the detection units 4, 5 (4',
5') has been described as outputting a detection signal with a phase difference of 90°, but if an appropriate phase difference (for example,
45°, 180°) may be arranged.
Furthermore, the arrangement of the magnetoresistive elements 4A, 4B, 5A, and 5B is not limited to the relationship expressed by equation (2), and may be set to an appropriate spacing. On the other hand, each threshold level setting circuit 10, 11 has been described as having a resistor and a thermistor connected in series, but depending on the temperature gradient,
A resistive connection that generates a function corresponding to this may be used. Further, the threshold level setting circuits 10 and 11 may be provided with separate power supplies from the detection units 4 and 5.

〔Effect of the invention〕

As described in detail above, the present invention is capable of outputting a rotation detection signal with a constant pulse width without being affected by changes in outside temperature, thereby eliminating fluctuations in pulse duty. The pulse duty can be maintained in a one-to-one relationship, and rotation can be detected with high precision over a wide temperature range.

[Brief explanation of the drawing]

1 to 8 relate to a first embodiment of the present invention, in which FIG. 1 is a configuration diagram of a rotation sensor, and FIG. 2 is an arrangement of a magnetoresistive element as seen from the N-pole side magnetized surface in FIG. 1. Figure 3 is a wiring diagram of a magnetoresistive element, Figure 4 is a wiring diagram of a magnetoresistive element.
The figure shows a characteristic diagram of the output voltage from each detection section, FIG. 5 shows a temperature-total amplitude voltage level characteristic diagram of the output voltage from each detection section, and FIG. 6 shows a temperature-total amplitude voltage level characteristic diagram of the output voltage from each detection section. FIG. 7 is a diagram showing the configuration of the signal processing circuit, FIG. 8 is a diagram showing the relationship between the output voltage and the threshold level according to this embodiment, and FIG. A characteristic diagram showing the relationship between the output voltage from the detection section and the setting voltage of the first threshold level setting circuit, and FIG. 8b shows the relationship between the output voltage from the second detection section and the second threshold level setting circuit. 9 and 10, which are characteristic diagrams showing the relationship between the set voltages of the setting circuit, relate to the second embodiment of the present invention. FIG. 9 is a configuration diagram of the rotation sensor, and FIG. FIG. 2 is a layout diagram of a magnetoresistive element viewed from the N-pole side magnetized surface. 1... Gear, 1A... Tooth profile, 2, 2'... Rotation sensor, 3, 3'... Permanent magnet, 4, 5, 4',
5'...detection section, 4A, 4B, 5A, 5B, 4
A', 4B', 5A', 5B'...magnetic resistance element, 10,
11...Threshold level setting circuit,
Vout4, Vout5...Output voltage (detection signal number,
Vout4 _DC , Vout5 _DC ...DC voltage level, V _T10 ,
V _T11 ...Set voltage (threshold level).

Claims (1)

[Scope of Claims] 1. A gear made of a magnetic material and a permanent magnet, which are disposed opposite to the tooth profile at a distance of 1/2 the pitch P of the tooth profile of the gear in the rotational direction of the gear. first and second detection means each comprising a pair of two magnetoresistive elements; a first detection means for setting a threshold level of a detection signal output from each of the detection means;
a second threshold level setting means, a separation dimension W between the first and second detection means;
is, with respect to the pitch P of the tooth profile with respect to the rotational direction of the gear, W = 2n - 1/4 x P, where n is set to an integer, and the first and second detection means are a pair of magnetic resistances. In a rotation detection device in which elements are connected in series, an intermediate position serves as an output terminal, and terminals to which a voltage is applied are connected in parallel, the threshold is set by the first and second threshold level setting means. The level is set to a value approximately equal to the characteristic value when the DC voltage level of the detection signal by the first and second detection means changes due to temperature change, respectively, using a temperature sensing element. Characteristic rotation detection device.