JPH0445089B2 - - 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 outputs a main signal and a sub-signal simultaneously, for example, with a phase difference of 90 degrees in electrical angle. 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 becomes smaller at high temperature than the amplitude characteristic at low temperature. Additionally, 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 at room temperature by the first threshold level setting means is set to the threshold level at room temperature by the first threshold level setting means.
The threshold level set by the second threshold level setting means at room temperature is set lower than the DC voltage level of the detection signal by the second detection means. It's in the settings.

[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 level at normal temperature by the first threshold level setting means is set lower than the DC voltage level of the detection signal by the first detection means, and the threshold level at normal temperature by the second threshold level setting means is set lower than the DC voltage level of the detection signal by the first detection means. Since the threshold level of is set higher than the DC voltage level of the detection signal from the second detection means, the detection signal output from the first and second detection means at high temperature and the detection signal output at low temperature are different. It is possible to reduce fluctuations in the pulse width after conversion to a pulse wave, and to eliminate the influence of temperature changes.

〔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, as shown in FIGS. 2 and 3, in each of the detection units 4 and 5, the respective magnetoresistive elements 4A and 4B, 5A and 5B are connected in series, and the series connection is connected to a power supply 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 output 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
B is characterized in that the element sensitivity decreases as the temperature rises, so the total amplitude voltage V ₀ (see Figure 4) between the peaks of the output voltages Vout4 and Vout5 decreases as the temperature increases, as shown in Figure 5. It has temperature characteristics such that it becomes small.

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 high temperature voltage decreases.
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, Vout5 DC is set as a reference.
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 each of the threshold level setting circuits 10 and 11 is connected to resistors R ₁ and R ₂ , R ₃ and R ₄ . In the first threshold level setting circuit 10, the output terminal 1 is connected between the resistors _R1 and _R2 .
The second threshold level setting circuit 11 outputs a predetermined set voltage V _T11 , which will be described later, from the output terminal 13 between _the resistors R ₃ and R ₄ .

Here, on the first threshold level setting circuit 10 side, the set voltage V _T10 at room temperature has the relationship V _T10 < Vout4 _DC (3) with respect to the DC voltage level Vout4 _DC of the detection unit 4. It will be destroyed. That is, at room temperature, both are placed in the relationship shown in FIG. 8a.

On the other hand, on the second threshold level setting circuit 11 side, the set voltage V _T11 at room temperature is
For the DC voltage level Vout5 _DC , the relationship is V _T11 > Vout5 _DC (4). That is, at room temperature, both are placed in the relationship shown in FIG. 8b.

Further, reference numerals 14 and 15 are first and second comparator circuits each consisting of, for example, an operational amplifier, and the first comparator 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, the output voltage on the detecting section 4 side is Vout4 _L shown in _FIG . It becomes low. Similarly,
On the detecting section 5 side, when the temperature is low or normal temperature, the output voltage is _Vout5L as shown in FIG. 8b, whereas when the temperature is high, the output voltage is _Vout5H , which is high.

However, between the first detection section 4 and the threshold level setting circuit 10, at room temperature,
Since the relationship is expressed by equation (3), the pulse widths of the output voltages Vout4 _L and Vout4 _H output from the comparator circuit 14 are t ₁ and t ₂ , respectively, based on the set voltage V _T10 as shown in FIG. 8a. , pulse width t ₁ ' of the output voltages Vout4 _L and Vout4 _H that are output based on the DC voltage level Vout4 _DC at room temperature as in the conventional technology,
Compared to t ₂ ', fluctuations in pulse width can be significantly reduced.

Furthermore, between the second detection section 5 and the threshold level setting circuit 11, at room temperature, (4)
As shown in FIG. 8b, the pulse width due to the output voltages Voutt5 _L and Vout5 _H output from the comparator circuit 15 based on the set voltage V _T11 is
t ₃ and t ₄ , and the fluctuation in the pulse width can be significantly reduced compared to the pulse widths t ₃ ′ and t ₄ ′ caused by the DC voltage level Vout5 _DC at room temperature as in the prior art.

In this way, this embodiment can always output a rotation detection signal with a constant pulse width without being affected by changes in outside temperature, so it is possible to perform highly accurate rotation detection 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.
Arrange them in the order of A' → 5A' → 4B' → 5B', and set the distance l between the magnetoresistive elements 4A' and 4B', and 5A' and 5B' to P/2 as in equation (1). At the same time, 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 based on the above equation. This is the case when n=1 in equation (2).

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°, 10°) 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. 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 and allowing use over a wide temperature range. Highly accurate rotation detection can be performed over the entire 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 is a characteristic diagram of the output voltage from each detector, Figure 5 is a temperature-total amplitude voltage level characteristic diagram of the output voltage from each detector, and Figure 6 is the temperature-DC output voltage from each detector. 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 setting voltage of the first threshold level setting circuit. 9 and 10, which are characteristic diagrams showing the relationship between the set voltages of the circuit, relate to the second embodiment of the present invention, and FIG. 9 is a configuration diagram of the rotation sensor, and FIG.
The figure is a layout diagram of the magnetoresistive element viewed from the N-pole side magnetized surface in FIG. 9. 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),
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 at room temperature is set by the first threshold level setting means. The level is set lower than the DC voltage level of the detection signal by the first detection means, and the threshold level at normal temperature by the second threshold level setting means is set to be lower than the DC voltage level of the detection signal by the second detection means. A rotation detection device characterized in that the voltage level is set higher than the DC voltage level.