JPH074987A - Reference position detector - Google Patents

Abstract

PURPOSE:To obtain a constantly stable reference position signal by holding an output from a position sensor at a predetermined level and further eliminating waviness and distortion of an output signal at a reference position. CONSTITUTION:In the outer periphery of a rotating body 2, a magnetized surface 4 where different magnetic poles are alternately magnetized is provided, and on the magnetized surface 4, a groove-shaped reference position 5 where a magnetizing pitch of the magnetic poles is larger than on other portions and which has a predetermined groove depth D is formed. A groove bottom 5a of the reference position 5 and the magnetized surface 4 of the magnetic pole adjacent to the reference position 5 are coupled with a curved face 5b having a predetermined curvature. A rotation angle sensor 6 has MR elements 7A, 7B opposite to the magnetized surface 4 and outputs a voltage signal Vout corresponding to magnetic field intensity as the rotating body 2 rotates. A signal processing circuit 15 is connected to the rotation angle sensor 6 via a waveform shaping circuit 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference position detecting device in which a position sensor is constructed by using a magnetic sensitive element such as a magnetoresistive element (hereinafter referred to as an MR element) or a Hall element.

[0002]

2. Description of the Related Art Conventionally, in this type of reference position detecting device, a magnetized body is provided with a magnetized surface in which different magnetic poles (S and N poles) are alternately magnetized, and the magnetized surface is magnetized at a predetermined position. A reference position was provided in which the magnetic pitch was made larger than in other parts. Then, with the relative movement of the magnetized surface of the magnetized body and the position sensor, the position sensor detects a change in the magnetic field strength according to the magnetized pattern, and based on the detected signal, the reference position signal and other A position signal can be obtained (for example, Japanese Patent Laid-Open Nos. 54-156656 and 5).
No. 7-3048, and No. 59-24970.

FIG. 6 is a diagram showing the structure of a conventional reference position detecting device. As shown in FIG. 6, a ring-shaped magnet 22 is fixed to the outer peripheral surface of the rotating body 21 as a magnetized body. The magnet 22 is provided with a magnetized surface 23 in which different magnetic poles are alternately magnetized, and a part of the magnetized surface 23 is provided with a reference position 24 in which the magnetizing pitch is larger than that of other portions. A position sensor 25 composed of an MR element is arranged at a position (sensing gap LG ′) apart from the magnetized surface 23 by a predetermined distance. Then, as the rotating body 21 rotates, the position sensor 25 causes the voltage signal Vout ′ corresponding to the magnetic field strength.
Is output.

However, in the above-mentioned conventional reference position detecting device, the voltage signal V of the position sensor 25 at the reference position 24 is detected.
There was a problem that swells and distortions occurred in'out '. That is, as shown in FIG. 7, magnetic field lines P ′ (indicated by arrows in the figure) corresponding to the magnetization pattern are present on the magnetized surface 23. At the reference position 24, since the width of the magnetic pole is wide, both ends are strongly magnetized at the time of magnetization, and the magnetic force lines P ′ are biased toward both ends, and the magnetic force lines P ′ near both ends of the reference position 24 become dense. Has become. Therefore, when the circumferential direction component of the magnetic force line P ′ (magnetic field strength) at the sensing position of the position sensor 25 (shown by the broken line in FIG. 7) is extracted, the direction of the magnetic field is reversed near the center line LC of the reference position 24. (SN inversion phenomenon) has occurred. That is, if the reference position 24 is the N pole, an outward magnetic field is originally generated with respect to the center line LC, but an inward magnetic field is generated.

Therefore, in the vicinity of the center line LC of the reference position 24, the voltage signal Vout 'of the position sensor 25 has undulations or distortion. Further, due to the waviness and distortion, the threshold level settable range Vth 'for shaping the waveform of the voltage signal Vout' is restricted to a narrow region, and the voltage signal Vou 'is limited.
The margin for variations in t'is reduced. If the voltage signal Vout ′ has a large variation, the waveform shaping process of the voltage signal Vout ′ becomes difficult, and the detection accuracy of the reference position signal may deteriorate.

Therefore, in order to solve the above problem, FIG.
There is proposed a reference position detecting device using a rotating body (magnetized body) 26 shown in FIG. In this rotating body 26, the magnet 27
A magnetized surface 28 is provided on the outer periphery of the magnet, and a reference position 29 formed of a rectangular cutout groove is provided on a part of the magnetized surface 28. That is, the groove bottom surface 29a at the reference position 29 and the magnetized surface 28 of the magnetic pole adjacent to the reference position 29 are connected by the vertical surface 30 perpendicular to the both surfaces 29a, 28.

Therefore, in this reference position detecting device, as shown in FIG.
As shown in, the sensing gap LG at the reference position 29
Since 2'becomes larger than the sensing gap LG1 'at other parts, the position sensor
The detection by 5 is performed. As a result, the swell of the voltage signal Vout is avoided.

[0008]

However, in the reference position detecting device having the rotating body 26 of FIG. 8, the voltage signal Vout
Although the swell is avoided, the output level of the position sensor 25 decreases and the threshold level settable range V
The problem that th 'becomes narrow arises. That is, the reference position 2
On the vertical surface 30 of the magnetic pole (S pole in the figure) adjacent to 9,
Since the opposing magnetic poles are not provided, the magnetic field strength near the reference position 29 becomes weak. As a result, the voltage level of the voltage signal Vout 'of the position sensor 25 is lowered, and the above problem occurs.

The present invention has been made in view of the above problems, and its object is to keep the output of the position sensor at a predetermined level and further to prevent the swell and distortion of the output signal at the reference position. The object of the present invention is to provide a reference position detecting device that can always obtain a stable reference position signal by eliminating the problem.

[0010]

In order to achieve the above object, the present invention has a magnetized surface in which different magnetic poles are magnetized alternately, and the magnetized surface has another magnetized pitch. A magnetized body having a groove-shaped reference position larger than the magnetized surface and having a predetermined groove depth, and a magnetic sensing element facing the magnetized surface of the magnetized body, and moved relative to the magnetized body. Then
A position sensor that outputs an electric signal according to the magnetic field strength of the magnetized surface, and a reference position signal generation circuit that waveform-shapes the output signal of the position sensor based on a predetermined threshold level and generates a reference position signal. In the reference position detecting device described above, the bottom of the groove at the reference position of the magnetized body and the magnetized surface of the magnetic pole adjacent to the reference position are connected by a gradient portion having a predetermined gradient. is there.

The sloped portion may be a curved surface having a predetermined curvature. Further, the sloped portion may be a flat surface having a predetermined inclination angle.

[0012]

According to the above structure, the position sensor outputs an electric signal according to the magnetic field strength of the magnetized surface due to the relative movement with the magnetized body. At this time, since the reference position is formed in a groove shape having a predetermined groove depth, the sensing gap at the reference position (the distance between the position sensor and the magnetized surface) becomes larger than the sensing gaps at other parts. As a result, even if the magnetic field is biased at both ends of the reference position, the reversal phenomenon of the magnetic field at the central part of the reference position is avoided, and the swell and distortion of the output signal of the position sensor are prevented. Also, with the bottom surface of the groove at the reference position,
Since the magnetized surface of the magnetic pole adjacent to the reference position is connected by the gradient portion having a predetermined inclination, the distance between the magnetized surface of the magnetic pole at the reference position and the magnetized surface of the magnetic pole adjacent to the reference position is As a result, the magnetic field strength between both magnetic poles is maintained at a high level, and a decrease in the output signal level of the position sensor is prevented.

The reference position signal generating circuit waveform-shapes the output signal of the position sensor based on a predetermined threshold level to generate a reference position signal. At this time, the output signal of the position sensor has no undulations or distortion and is held at a high output level, so that the threshold level can be set in a wide range. As a result, it is possible to always generate a stable reference position signal.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the reference position detecting device of the present invention is embodied in a fuel injection device for a 4-cylinder diesel engine will be described below with reference to the drawings. As shown in FIG. 1, a disc-shaped rotating body 2 as a magnetized body is fixed to a shaft 1 that rotates at a rotation speed of 1/2 as the diesel engine 40 rotates. The shaft 1 is an input shaft of the fuel injection pump 50,
Pressurizes the fuel by the rotational force of the shaft 1 and distributes the fuel to each injection valve of the diesel engine 40. A reference position detecting device having the rotating body 2 is provided in the fuel injection pump 50.

The rotating body 2 has a ring-shaped magnet 3 on its outer peripheral surface.
have. A magnetized surface 4 in which different magnetic poles are alternately magnetized is provided on the outer periphery of the magnet 3, and the magnetized surface 4 has a cutout groove shape and a reference position 5 magnetized with an N pole. Are evenly distributed in four places. 24 on the magnetized surface 4
The 0-pole magnetic pole is magnetized, and the groove width at the reference position 5 is the width of 7 poles of the magnetic poles other than the reference position 5. That is,
The relationship between the magnetization pitch λ other than the reference position 5 and the magnetization pitch λ0 at the reference position 5 is λ0 = 7 · λ. Specifically, when the outer diameter of the magnet 3 is 70 mm, λ≈0.
92 mm and λ0 ≈ 6.4 mm.

The reference position 5 has a predetermined groove depth D,
The groove bottom surface 5a at the reference position 5 and the magnetized surface 4 of the magnetic pole adjacent to the reference position 5 are connected by a curved surface 5b as a gradient portion having a predetermined curvature (radius R). Specifically, the groove depth D at the reference position 5 is about 1 mm, and the radius R
Is about 6 mm. The shape of the reference position 5 is determined according to the outer diameter of the magnet 3 and the number of magnetic poles, and the groove depth D of the reference position 5 is equal to the magnetizing pitch λ of the magnetic poles other than the reference position 5. It is good to make them approximately equal. Further, the radius R of the curved surface 5b is preferably similar to that of this embodiment. For example, when the outer diameter of the magnet 3 is changed to 35 mm,
R = 3 mm is preferable.

Further, in this embodiment, the magnet 3 is made of a magnetic plastic magnet, and the magnet 3 is integrally molded including the groove portion at the reference position 5. According to this molding method, the magnet 3 can be manufactured at low cost. However, in addition, it is also possible to use a method in which a ring-shaped magnet is fixed to the rotating body 2 and then scraped off by machining, or a molding method by sintering ferrite powder or the like.

The rotation angle sensor 6 as a position sensor includes a pair of MR elements 7 as magnetic sensitive elements facing the magnetized surface 4.
It has A and 7B. The MR elements 7A and 7B are the magnet 3
Of the MR elements 7A and 7B, the mounting pitch λ1 of the MR elements 7A and 7B is 1/2 of the magnetizing pitch λ (λ1 = λ).
/ 2). On the magnetized surface 4 other than the reference position 5, the sensing gap LG1 between the MR elements 7A and 7B and the magnetized surface 4 is
Is set to 0.8 mm. Therefore, at the reference position 5, the sensing gap LG2 is larger than the sensing gap LG1 at other portions by the groove depth D at the reference position 5 (LG2 = LG1 + D).

A driving power source Vcc is applied to the MR elements 7A and 7B.
(5 volts) are connected in series and both MR elements 7A, 7B
The middle point is the output terminal 8 of the rotation angle sensor 6. The rotation angle sensor 6 has a resistance value of the MR element 7A and M
Voltage signal Vout corresponding to the difference from the resistance value of the R element 7B
Is output. A waveform shaping circuit 9 is connected to the rotation angle sensor 6. The waveform shaping circuit 9 includes resistors 10 to 12
The adjusting resistor 13 and the comparator 14 are provided. Then, in the waveform shaping circuit 9, the threshold level Vth is set according to the resistance value of the adjusting resistor 13, and the voltage signal Vout of the rotation angle sensor 6 is waveform-shaped at the threshold level Vth, and the rotation angle signal Ne is obtained. Is generated. A signal processing circuit 15 is connected to the waveform shaping circuit 9. Then, in the signal processing circuit 15, the reference position signal G is generated based on the rotation angle signal Ne output from the waveform shaping circuit 9. In the present embodiment, the waveform shaping circuit 9 and the signal processing circuit 15 constitute a reference position signal generation circuit.

The signals from the waveform shaping circuit 9 and the signal processing circuit 15 are input to the fuel injection control device 60. The fuel injection control device 60 controls the fuel injection pump 50 so as to realize the target injection amount and the injection timing set according to the load condition of the engine and the like. In particular, in this example,
The energization / interruption timing of the electromagnetic spill valve 70 is determined according to the rotation angle signal Ne and the reference position signal G, and the electromagnetic spill valve 7 is operated.
The valve opening time of 0 is adjusted to control the fuel injection amount.

Next, the operation of the reference position detecting device of this embodiment will be described with reference to FIG. As shown in FIG.
Magnetic field lines P (indicated by arrows in the figure) corresponding to the magnetization pattern are present on the magnetized surface 4. For details, the magnetized surface 4
The magnetic field lines P exist from the N pole to the S pole, and at the reference position 5, both ends are strongly magnetized at the reference position 5 due to the wide width, and the magnetic field lines P are biased toward both ends. for that reason,
The magnetic force lines P near both ends of the reference position 5 become dense,
A region near the magnetized surface 4 at the reference position 5 (for example, the groove bottom surface 5a
In a region where the distance is from the sensing gap LG1), a phenomenon in which the direction of the magnetic field is inverted (SN inversion phenomenon) occurs near the center line LC of the reference position 5. That is, if the reference position 5 is the N pole, an outward magnetic field is originally generated with respect to the center line LC, but an inward magnetic field is generated.

However, at the sensing position of the rotation angle sensor 6 (shown by the broken line in FIG. 2), the sensing gap L thereof is
Since G2 is larger than the sensing gap LG1 of the other part, the SN inversion phenomenon is eliminated, and the waviness of the circumferential component of the magnetic force line P (magnetic field strength) near the center line LC is avoided. Further, since the groove bottom surface 5a at the reference position 5 and the magnetized surface 4 of the magnetic pole adjacent to the reference position 5 are connected by the curved surface 5b, the magnetic field at the sensing position in the magnetic pole adjacent to the reference position 5 The strength is maintained at a high level.

As the rotating body 2 rotates, the resistance values of the MR elements 7A and 7B of the rotation angle sensor 6 change, and the rotation angle sensor 6 outputs a voltage signal for two cycles per cycle of change in magnetic field strength. Output Vout. Also, at the sensing position of the rotation angle sensor 6, the rotation angle sensor 6 operates without being affected by the SN inversion phenomenon, and the voltage signal Vou is always stable.
Output t.

In the waveform shaping circuit 9, the voltage signal Vout output from the rotation angle sensor 6 is applied to the threshold level Vth.
The waveform is shaped by and the rectangular pulse-shaped rotation angle signal Ne is output. At this time, since the voltage signal Vout of the rotation angle sensor 6 is stable, the threshold level Vth is possible in a wide range. In addition, the signal processing circuit 15
Then, the reference position signal G is generated by software processing the signal generation cycle Ta of the rotation angle signal Ne.
That is, in the signal processing circuit 15, every time the rotation angle signal Ne is input, the reference position signal output time Tx (= k · Ta) is calculated by multiplying the signal generation cycle Ta by the constant k. Then, within the reference position signal output time Tx, the next rotation angle signal N
When e is input, the reference position signal output time Tx is cleared. If the rotation angle signal Ne is not input within the time Tx, the reference position signal G is output at the timing of the reference position signal output time Tx. In this way, the reference position signal G is output for each cylinder of the diesel engine 40 corresponding to the reference position 5.

The value of the constant k is set so that the reference position 5 will not be erroneously detected even when the generation cycle Ta of the rotation angle signal Ne changes due to the change of the engine speed or the acceleration / deceleration. It is set according to the length of 5. After that, the rotation angle signal Ne and the reference position signal G are input to the fuel injection control device 60, and fuel injection control and the like are performed.

As described in detail above, in the reference position detecting apparatus of this embodiment, the outer peripheral surface of the rotating body 2 is provided with the magnetized surface 4 in which different magnetic poles are alternately magnetized, and the magnetized surface 4 is formed. A groove-shaped reference position 5 was formed in which the magnetic pitch of the magnetic poles was larger than that of the other portions and had a predetermined groove depth D. The groove bottom surface 5a at the reference position 5 and the magnetized surface 4 of the magnetic pole adjacent to the reference position 5 have a curved surface 5 having a predetermined curvature (radius R).
It was connected at b.

According to the above structure, the sensing gap LG2 at the reference position 5 is the sensing gap LG1 at another portion.
Will be larger than. As a result, even if the magnetic field is biased at both ends of the reference position 5, the reversal phenomenon of the magnetic field at the center of the reference position 5 is avoided, and the voltage signal Vou of the rotation angle sensor 6 is avoided.
Waviness and distortion of t are prevented. Further, the magnetic field strength of the magnetic poles adjacent to the reference position 5 is maintained at a high level, and the output signal level of the rotation angle sensor 6 is prevented from lowering. Further, since the swell and distortion of the output signal of the rotation angle sensor 6 are prevented and the output signal is held at a high output level, the threshold level Vth can be set in a wide range. As a result, it is possible to always generate the stable reference position signal G.

The present invention is not limited to the above embodiment, but can be embodied in the following modes.
For example, as shown in FIG. 3, the groove bottom surface 5a at the reference position 5
And the magnetized surface 4 of the magnetic pole adjacent to the reference position 5 may be connected by a plane 16 having a predetermined inclination angle RA.

Further, as shown in FIG. 4, a wall surface 17 having a predetermined length LA is provided at both ends of the reference position 5, and the groove bottom surface 5a at the reference position 5 and the wall surface 17 are provided with a predetermined inclination angle RA.
You may connect by the plane 16 which has. At this time, the predetermined length LA of the wall surface 17 is set within a range in which the magnetic field strength at both ends of the reference position 5 can be maintained at a predetermined level or higher.

Further, as shown in FIG. 5, a linear type magnetizing body 18 may be used instead of the rotating body 2. In this case, the magnetized body 18 or the position sensor is moved by moving the magnetized body 18 or the position sensor to detect the position. Further, the reference position signal generation circuit may be configured differently from the waveform shaping circuit 9 of the above embodiment. For example, the peak value or the bottom value of the output signal of the position sensor may be set as a threshold level, and the waveform shaping process may be performed at the threshold level.

Further, in the first embodiment, the outer diameter of the magnet is 7
Although the outer diameter is set to 0 mm, more magnetic poles may be magnetized by increasing the outer diameter. For example, by setting the outer diameter to 105 mm, it is possible to magnetize 360 poles with the same pitch width λ≈0.92 mm as in the first embodiment, and the resolution can be 1 °. Further, since it is disadvantageous in processing and assembling work to make the sensing gap LG1 small, the pitch width λ may be made large and the magnetic field strength may be increased to make the sensing gap LG1 large. For example, if the magnet has an outer diameter of 70 mm and a pitch width λ≈1.84 mm, a sufficient output voltage Vout can be obtained even if the sensing gap LG1 is LG1 = 1.5 mm.

In addition, as the magnetic sensing element, a hall element may be used instead of the MR element to form the position sensor. In this case, the output signal of the position sensor changes corresponding to the change in the electromotive force of the Hall element according to the magnetic field strength.

[0033]

According to the present invention, the output of the position sensor is maintained at a predetermined level, and the swell and distortion of the output signal at the reference position are eliminated, so that a stable reference position signal can be obtained at all times. Exerts an excellent effect.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a reference position detection device in an embodiment of the present invention.

FIG. 2 is an operation diagram of the reference position detection device according to the embodiment.

FIG. 3 is a plan view showing a modified example of a magnetized body.

FIG. 4 is a plan view showing a modified example of a magnetized body.

FIG. 5 is a perspective view showing a modified example of a magnetized body.

FIG. 6 is a plan view showing a conventional reference position detecting device.

FIG. 7 is an operation diagram of a conventional reference position detection device.

FIG. 8 is a plan view showing a conventional reference position detecting device.

FIG. 9 is an operation diagram of a conventional reference position detection device.

[Explanation of symbols]

 2 Rotating body as magnetized body 4 Magnetized surface 5 Reference position 5a Groove bottom 5b Curved surface as gradient part 6 Rotation angle sensor as position sensor 7A, 7B MR element as magnetic sensitive element 9 Waveform as reference position signal generation circuit Shaping circuit 15 Signal processing circuit as reference position signal generation circuit 16 Plane as gradient part 18 Magnetized body

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masato Hoshino, 1130 Norikura, Midori-ku, Nagoya-shi, Aichi 1303-2 (72) Hiroshi Kimura 148 Akatsuka, Narumi-cho, Midori-ku, Nagoya-shi, Aichi

Claims (3)

[Claims] 1. A groove-shaped reference position having a magnetized surface in which different magnetic poles are alternately magnetized, and the magnetized pitch of the magnetic poles is larger than other portions on the magnetized surface and has a predetermined groove depth. And a magnetizing element facing the magnetized surface of the magnetized body, which moves relative to the magnetized body and outputs an electric signal according to the magnetic field strength of the magnetized surface. In a reference position detection device including a position sensor and a reference position signal generating circuit that shapes the output signal of the position sensor based on a predetermined threshold level, and generates a reference position signal, the reference position of the magnetized body A reference position detecting device characterized in that a groove bottom surface and a magnetized surface of a magnetic pole adjacent to the reference position are connected by a gradient portion having a predetermined gradient. 2. The reference position detecting device according to claim 1, wherein the gradient portion is a curved surface having a predetermined curvature. 3. The reference position detecting device according to claim 1, wherein the sloped portion is a flat surface having a predetermined inclination angle.