JP2014115251A - Capacitance gear tooth and method for detecting rotational speed of capacitance rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitance gear tooth having electrodes of a simple structure and allowing highly accurate measurement of rotational speed of a rotor.SOLUTION: A capacitance gear tooth is provided with a sensor head (4) that has a pair of capacitance electrodes (4A, 4B) on a housing (1) side with a prescribed gap (a) with respect to a projection (3) of a rotor (2). One of the electrodes is disposed facing an end face of the projection on a crest side, while the other of the electrodes is disposed facing a trough side of the projection. Tips of a pair of cables (6A, 6B) corresponding to the electrodes are connected to the electrodes, while rear ends of the cables are connected to a capacitance arithmetic circuit (5A). When the rotor is rotating, capacitance detected by the electrodes is transmitted as a detection signal via the cables to the capacitance arithmetic circuit, which calculates each detection signal as capacitance difference between C-C.

Description

  The present invention relates to a wheel speed sensor for detecting the rotation speed of a front wheel and a rear wheel of a vehicle and a rotation speed sensor for detecting a rotation angle of an automobile engine, and more particularly to a capacitance type detecting a rotation speed of a rotating body. The present invention relates to a detection method of a rotational speed of a gear tooth sensor and a capacitance type rotating body.

  The problem of Patent Document 1 is that, in view of the drawbacks of the wheel speed sensor described in Japanese Patent Application Laid-Open No. 58-55760, no coil is required, cost can be reduced, and water is not provided in the gap between the protrusion and the sensor head. For example, the output voltage as a pulse signal becomes constant even if foreign matter enters and adheres.

  As means for solving this problem, a wheel speed sensor disclosed in Patent Document 1 includes a sensor head 26 in which a dielectric 14 is provided on a positive electrode body 12 and a peripheral portion of a rotating body B that rotates integrally with a wheel at a predetermined pitch interval. And a protrusion 25 which is the other electrode body in the vicinity of the sensor head 26, and an increase in the output voltage V which is output by converting the capacitance between both electrode bodies into a pulse voltage is a constant voltage. And a cut-off means for cutting off the value (reference numeral 1).

The known device of Patent Document 1 is a capacitive wheel speed sensor that applies the principle of a capacitor as in the present invention, but its structure is complicated. Further, as apparent from FIG. 1 of Patent Document 1, the number of sensor heads on the vehicle body side is “one”.
When an additional note, the sensor head Patent Document 1, during rotation of the rotating body, and detects only one capacitance C _A facing end faces of the projections.

  Therefore, it is necessary to provide a cutoff means for cutting off the increment of the output voltage V to a constant voltage value in order to remove noise. This known device also includes an electrode housing portion 11a and a substrate housing portion 11b insulated by an insulator in the case of the sensor portion A, and a flexible substrate 18 connected to one sensor head in the substrate housing portion 11b. The electronic circuit (IC) having the cut-off means is disposed. The electronic circuit (IC) is disposed with the sensor head at a high temperature place.

Therefore, as a high-temperature countermeasure, for example, G _{A A,} such as S _(Garyumu arsenic), there is a problem that must be used expensive compound semiconductor.

  Therefore, the problems of the conventional gear tooth sensor are briefly pointed out. The gear tooth sensor is used as a means for accurately measuring the rotation angle at a high temperature. The sensor head of the gear tooth sensor is installed close to the tip of the teeth (protrusions) of the rotating body (gear), and detects the number of teeth passed by detecting the difference in distance between the crest and trough of each tooth. Count. In principle, as in Patent Document 2 and Patent Document 3, for example, gears used at high temperatures are made of a magnetic material (mainly iron). ing. However, since the hall element using Si (silicon), which is the most common and inexpensive, deteriorates in characteristics at high temperatures and is difficult to use, a relatively expensive compound semiconductor is used. Still, the upper limit of usable temperature is about 150 ° C. at present.

Japanese Utility Model Publication No. 5-59313 JP 58-55760 A JP 2009-222524 A

  The intended object of the present invention is to measure the rotational speed of the rotating body with high accuracy while the structure of the electrode is simple in view of the problems of Patent Document 1. The second object is that a relatively inexpensive silicon IC can be used for an electronic circuit (capacitance calculation circuit) instead of a relatively expensive compound semiconductor. Note that Patent Document 2 has a similar purpose because a coil is unnecessary as in Patent Document 1.

The capacitive gear toe sensor of the present invention has a predetermined gap (a) with respect to the protrusion (3) of the rotating body (2), and a pair of capacitive electrodes on the housing (1) side ( 4A, 4B) is provided, and one of the electrodes is disposed so as to face the mountain side end face of the protrusion, while the other of the electrodes faces the valley side of the protrusion. The front ends of the pair of cables (6A, 6B) corresponding to the electrodes are connected to the electrodes, respectively, while the rear ends of the cables are respectively connected to the capacitance calculation circuit (5A). When the rotating body rotates, the capacitance detected by the electrode is sent as a detection signal to the capacitance calculation circuit via the cable, and the capacitance calculation circuit Is calculated as a capacitance difference of C _A -C _B.

In addition, according to the method of detecting the rotational speed of the electrostatic capacity type rotating body of the present invention, a pair of gaps (a) is provided on the housing (1) side with respect to the protrusion (3) of the rotating body (2). The sensor head (4) having the electrodes (4A, 4B) is provided, and when the rotating body rotates, when the one electrode faces the peak side of the protrusion, the other electrode Capacitance calculation circuit (6A, 6B) via a pair of cables (6A, 6B) separately connecting the detection signals simultaneously detected by the sensor head (4) having the electrodes so as to face the valley side 5A), and the capacitance calculation circuit calculates each detection signal as a capacitance difference of C _A -C _B.

  Here, the “capacitance calculation circuit” is composed of a pair of capacitance-voltage conversion circuits (hereinafter referred to as “CV conversion circuits”) and an operational amplifier for calculating the difference between the output voltages. Circuits and the like.

Therefore, the capacitive gear toe sensor of the present invention has a predetermined gap a with respect to the protrusion 3 of the rotating body 2, for example, and has a pair of capacitive electrodes 4A and 4B on the housing 1 side. A head 4 is provided, and one of these electrodes 4A is disposed so as to face the mountain side end face of the protrusion 3, while the other electrode 4B is disposed so as to face the valley side of the protrusion 3. The front ends of the pair of cables 6A and 6B corresponding to the pair of electrodes 4A and 4B are respectively connected to the pair of electrodes 4A and 4B, respectively, while the rear ends of the pair of cables are respectively connected to the capacitance − Capacitance detected by the pair of electrodes 4A and 4B during rotation of the rotating body 2 is connected to a voltage conversion circuit (hereinafter referred to as CV conversion circuit) 4, and the pair of cables is detected as a detection signal. CV through 6A and 6B Sent to circuit 4, the C-V conversion circuit 4 and calculates the respective detection signals as an electrostatic capacitance difference C _A -C _B.

  The method for detecting the rotational speed of the electrostatic capacity type rotating body of the present invention is also the same as the above-described invention. The present invention includes the configuration of claim 1 as it is, and in a usage environment in which the temperature on the sensor head side is exposed to a high temperature, the CV conversion circuit constituting the capacitance calculation circuit is The semiconductor element of the CV conversion circuit is a silicon IC, which is disposed at a location lower in temperature than the sensor head via the cable shielded from the outside.

According to the present invention, it is possible to accurately detect that the protrusion of the rotating body has passed through with one sensor head having a plurality of electrodes. In addition, since the sensor head as the detection electrode and the capacitance-voltage conversion circuit and the electronic circuit as the arithmetic circuit can be set apart to a desired range, a relatively low temperature can be set with respect to the temperature on the housing or the vehicle body side. If an electronic circuit is installed in a maintainable place, Si (silicon), which is a general and inexpensive material, can be used as a semiconductor element. Furthermore, if a material (for example, ceramic) that can withstand high temperatures is used as a base material, the detection electrode can be measured even at a temperature of several hundred to 1000 ° C. Therefore, the invention described in each claim has the following effects.
(A) The inventions according to claims 1 and 3 have an extremely simple structure because there is only one sensor head having two electrodes. Further, since the CV conversion circuit outputs each detection signal as a capacitance difference of C _A -C _B , so-called noise is small.
(B) In the invention described in claim 2, an electronic circuit (CV conversion circuit) may be disposed at a location where the temperature of the vehicle body is low, away from the sensor head which must be installed at a high temperature location. Therefore, a relatively inexpensive silicon IC can be used instead of a relatively expensive compound semiconductor. Therefore, cost can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. BRIEF DESCRIPTION OF THE DRAWINGS Schematic explanatory drawing which shows the principal part of this invention (a part of rotary body is developed). Explanatory drawing of an output voltage when two electrodes of one sensor head confront a trough (a) and a peak (b) of a protrusion. The conceptual diagram which shows the technical idea of patent document 1 (Japanese Utility Model Laid-Open No. 5-59313) (a part of the rotating body is developed).

1 to 3 are explanatory diagrams showing an embodiment of the present invention, while FIG. 4 is a conceptual diagram showing a technical idea of Patent Document 1 (Japanese Utility Model Publication No. 5-59313) (rotary body). Part of the development).
First, in order to grasp the difference between the technical idea of Patent Document 1 and that of the present invention, the known device of FIG. 4 will be briefly described. In FIG. 4, X is a wheel speed sensor fixedly disposed on the vehicle body 1 side, 2 is a rotating body (gear), and 3 is a protrusion (tooth) of the rotating body. The sensor portion A of the wheel speed sensor X includes a sensor body (not shown), and an electrode housing portion on the front end side and a substrate housing portion on the rear end portion side are formed on the sensor body. In the electrode accommodating portion on the tip end side, there is provided “one” sensor head 4 that can be opposed to the crest (end surface) 3a of the protrusion (tooth) 3 with a predetermined distance a when the rotating body rotates. ing.

  Also, an electronic circuit 5 is provided in the substrate housing portion, and the electronic circuit 5 is electrically connected to the sensor head 4 via connection means 6 such as a connector, a first substrate, a flexible second substrate, etc. (not shown). Yes. The sensor head 4, connection means 6 and electronic circuit 5 are isolated from the sensor body by an epoxy resin insulator 7.

  Incidentally, a dielectric 8 made of barium titanate / ceramics is adhered to the tip of the sensor head 3, and the peripheral portion of the dielectric 8 is also covered with the insulator 7. The rotating body 2 is a rotor that rotates integrally with a wheel (not shown), and a plurality of protrusions 3 are formed in a gear shape on the periphery of the rotor 2 at a predetermined pitch interval.

  In the above configuration, the operation is as described in paragraph 0016 of the patent document. That is, when the rotor 2 rotates, the output voltage V rises at the initial stage when the right side of the end face 3a of the protrusion (minus electrode body) 3 overlaps the dielectric 8, and the end face 3a of the protrusion (minus electrode body) 3 rises. When it overlaps the dielectric 8 at 1: 1, the output voltage V becomes constant, and the output voltage V falls at the later stage when the left side of the end face 3 a of the protrusion (minus electrode body) 3 overlaps the dielectric 8. For this reason, when one protrusion 3 of the rotor 2 moves relative to the sensor head 4 of the sensor part A, one pulse is generated as the output voltage V, and the number of protrusions (negative electrode bodies) 3 overlapping the dielectric 8. Only the pulse signal oscillates as the output voltage V.

  Next, with reference to FIGS. 1 to 3, the capacitance type gear tooth sensor X1 and the detection method X2 of the rotational speed of the capacitance type rotating body of the present invention will be described. In the description of the configuration and operation of the present invention, the same configuration as that of Patent Document 1 is denoted by the same or similar reference numerals for the sake of convenience, and redundant description is omitted.

  In these drawings, A is a sensor unit, 1 is a vehicle body, 2 is a rotating body (gear), 3 is a protrusion (tooth) of the rotating body, 3a is a protrusion peak, 3b is a protrusion valley, and a is one. A gap between the tip surface of one electrode 4A of the sensor head 4 and the peak 3a of the projection, b is a gap between the tip surface of the other electrode 4B of the sensor head 4 and the valley 3b of the projection, 5A. Is a capacitance calculation circuit having at least a CV conversion circuit, 6A is a first cable corresponding to one electrode 4A, 6B is a second cable corresponding to the other electrode 4B, and 7 is an insulator.

Therefore, the capacitance type gear tooth sensor X1 of the present invention has a predetermined gap a and b with respect to the protrusion 3 of the rotating body 2 and forms a capacitance type sensor head on the housing 1 or the vehicle body side. Two electrodes 4A and 4B having the same form are provided, and one electrode 4A of the sensor head 4 is disposed so as to face the mountain side end surface 3a of the protrusion 3, while the other electrode 4B of the sensor head 4 is It is arranged so as to face the valley side 3b of the projection 3, and the respective ends of the pair of cables 6A and 6B corresponding to the pair of electrodes 4A and 4B are connected to the pair of electrodes 4A and 4B, respectively. On the other hand, each rear end portion of the pair of cables 6A and 6B is connected to a capacitance calculation circuit 5A having a CV conversion circuit, and detected by the electrodes 4A and 4B when the rotating body 2 rotates. capacitance _{C A, B,} the pair of cables 6A as a detection signal is sent to the electrostatic capacity calculation circuit 5A through 6B, electrostatic capacity calculation circuit 5A each detected signal as a differential capacitance of C _A -C _B Calculate (feature 1).

  Therefore, as is clear from the comparison between FIG. 1 and FIG. 4, the difference between Patent Document 1 and the present invention is that the electrode of the sensor head 3 of the sensor part A of Patent Document 1 is “one”. On the other hand, the electrodes 4A and 4B of the sensor head 4 of the present invention are “two” (difference 1).

  That is, in the embodiment, a pair of electrostatic capacitance type electrodes 4A and 4B is provided on the housing or the vehicle body 1 side with a predetermined gap a with respect to the protrusion 3 of the rotating body 2. Each electrode 4A, 4B has the same size and the same shape. For example, as shown in FIG. 2, the crest 3a of each protrusion (tooth) 3 that moves in the direction of the arrow of the rotating body 2 on the same plane and its The valleys 3b are confronted simultaneously with predetermined intervals a and b.

In the embodiment, the capacitance calculation circuit 5A connected to the pair of cables 6A and 6B corresponding to the electrodes 4A and 4B is separated from the one sensor head 4A and 4B which must be installed in a high temperature place. The vehicle body is disposed at a location where the temperature is low (characteristic 2).
Then, during rotation of the rotating body 2, the one sensor head 4A, the detected capacitance C _A in _4B, C _B, the pair of cables 6A as a detection signal, the electrostatic capacitance through the 6B arithmetic circuit 5A The capacitance calculation circuit 5A calculates each detection signal as a capacitance difference of C _A -C _B.

  FIG. 3 is an explanatory diagram of the output voltage when the two electrodes 4A and 4B are opposed to the valley (a) and the peak (b) of the protrusion 3, and FIG. 3 shows the rotational speed of the capacitive rotor. This shows a detection method X2.

Therefore, replacing the product invention with the process invention results in the following. The detection method X2 of the rotational speed of the electrostatic capacity type rotating body of the present invention has a pair of electrodes (4A, 4B) on the housing 1 side with a predetermined gap a with respect to the protrusion 3 of the rotating body 2. When the one rotating head rotates and the one electrode faces the peak side of the protrusion, the other electrode faces the valley side of the protrusion, and the electrode is provided. The capacitance calculation circuit 5A acquires the detection signals simultaneously detected by the sensor head 4 having a sensor via a pair of cables (6A, 6B) respectively connected to the electrodes, and the capacitance calculation circuit detects each detection signal. The signal is calculated as a capacitance difference of C _A -C _B.

  FIG. 3 is an explanatory diagram of the output voltage when the two electrodes 4A and 4B are opposed to the valley 3 (a) and the peak (b) of the protrusion 3, and the output voltage decreases, rises, or becomes constant. The operations such as these are the same as in the conventional embodiment.

  The two electrodes 4A and 4B are both made of barium titanate or ceramics. Further, the CV conversion circuit constituting the capacitance arithmetic circuit 5A is not a relatively expensive compound semiconductor, but is made of a relatively inexpensive silicon IC. Furthermore, the CV conversion circuit is not disposed in the sensor unit A, but is disposed at an appropriate position of the casing or the vehicle body 1 at a temperature lower than that of the sensor unit A via the pair of cables 6A and 6B. Preferably, the length of the cables 6A and 6B is “1 meter or more”.

In the embodiment, two electrodes 4A and 4B having the same shape and the same size are arranged on the same plane with a little space therebetween. Two electrodes 4 </ b> A and 4 </ b> B having the same configuration are arranged in parallel with the rotation direction of the gear 2. In this case, if the width in which the two electrodes 4A and 4B are arranged is smaller than the pitch of the gear, the area where the two electrodes 4A and 4B and one of the teeth 3 face each other changes as the gear rotates. Since the capacitance formed with the larger area facing the teeth 3 is larger, the capacitance difference between the two capacitances (C _A , C _B ) in the figure is periodic as the gear 2 rotates. To change. If this is replaced with an electric signal, it becomes a gear toe sensor.

  It is used as a wheel speed sensor that detects the rotational speeds of the front and rear wheels of a vehicle.

X ... wheel speed sensor,
X1: Capacitance type gear tooth sensor,
X2: Method for detecting the rotational speed of the electrostatic capacity type rotating body,
A ... Sensor part,
1 ... body or housing, 2 ... rotary body (gear),
3 ... Projection (tooth) of rotating body, 3a ... Projection peak, 3b ... Projection valley,
4 ... Sensor head,
4A ... one electrode,
4B ... the other electrode,
a: a gap between the tip surface of one electrode 4A and the protrusion 3a,
b: a gap between the tip surface of the other electrode 4B and the valley 3b of the protrusion,
5A: Capacitance calculation circuit (including at least a CV conversion circuit),
6A: a first cable corresponding to one electrode 4A,
6B ... the second cable corresponding to the other electrode 4B,
7 is an insulator.

Claims (3)

One sensor head (4) having a predetermined gap (a) with respect to the protrusion (3) of the rotating body (2) and having a pair of capacitive electrodes (4A, 4B) on the housing (1) side. ), And one of the electrodes is disposed so as to oppose the crest-side end surface of the protrusion, while the other of the electrodes is disposed so as to oppose the trough side of the protrusion, and a pair corresponding to the electrode Each cable (6A, 6B) is connected to the respective electrodes, while each cable rear end is connected to a capacitance calculation circuit (5A). The capacitance detected by the electrode is sent as a detection signal to the capacitance calculation circuit via the cable, and the capacitance calculation circuit converts each detection signal as a capacitance difference of C _A -C _B. Capacitance type gear toe sensor to calculate. 2. The use environment according to claim 1, wherein the CV conversion circuit constituting the capacitance calculation circuit is shielded from the outside with respect to the electrode in a use environment where the temperature on the sensor head side is exposed to a high temperature. A capacitance type gear tooth sensor, wherein the CV conversion circuit semiconductor element is a silicon IC, which is disposed at a lower temperature than the sensor head via a cable. One sensor head (4) having a predetermined gap (a) with respect to the protrusion (3) of the rotating body (2) and having a pair of electrodes (4A, 4B) on the housing (1) side is provided, When the rotating body rotates, if the one electrode faces the peak side of the protrusion, the other electrode faces the valley side of the protrusion, and the sensor head (4) having the electrode simultaneously The capacitance calculation circuit (5A) obtains the detected detection signals via a pair of cables (6A, 6B) separately connected to the electrodes, and the capacitance calculation circuit transmits each detection signal to C _A − A method of detecting the rotational speed of a capacitance-type rotating body that is calculated as a capacitance difference of C _B.

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