JP5525208B2 - Proximity sensor - Google Patents

Description

  The present invention relates to a high-frequency oscillation type proximity sensor.

Conventionally, various high-frequency oscillation type proximity sensors have been provided (for example, see Patent Document 1). This type of proximity sensor includes an oscillation circuit unit, a detection circuit unit, and a casing that houses them. The oscillation circuit unit includes an LC oscillation circuit having at least a core formed in a rod shape and an annular coil wound around the core. The detection circuit unit detects a change in the oscillation amplitude of the LC oscillation circuit (for example, oscillation / oscillation stop) that occurs when a detection object made of a metal body or a magnetic body approaches the tip of the core. Detect presence or absence. That is, the proximity sensor described above utilizes the fact that, for example, when a metal body comes close to the tip of the core, eddy current loss occurs due to electromagnetic induction and the effective resistance value (impedance) of the annular coil changes.

By the way, such a proximity sensor is attached in the housing of the transmission in order to detect, for example, the traveling speed (speed) of the automobile and the rotation state of the wheels. In the housing, there is installed a rotor that rotates integrally with the rotation shaft and has a plurality of protrusions formed at predetermined intervals on the circumferential portion along the rotation direction. Is used in a speed detection device (for example, see Patent Document 2).

This is because each protrusion of the rotating rotor (magnetic material) repeats proximity / non-proximity continuously with respect to the tip of the core where the stationary rotor is located. The rotation speed of the rotor is detected by measuring how many times the rotation is detected.

An example of a proximity sensor used to detect the rotational speed of such a rotor is a proximity sensor 90 as shown in FIG. As shown in FIG. 6, the proximity sensor 90 includes an oscillation circuit unit, a detection circuit unit, a circuit board 91 on which circuit components constituting each circuit unit are mounted, and a casing 92 that houses the circuit board 91 therein. Is provided. The casing 92 is formed in a hollow, substantially cylindrical shape, and a core 94 around which the annular coil 93 is wound is fixed below the inside. However, the hole 92b is penetrated in the lower end part 92a of the casing 92, and the front-end | tip part 94a of the core 94 is exposed outside while being flush with the lower end part 92a of the casing 92 through the hole part 92b. A thread groove 92 c is formed on the peripheral surface of the casing 92, and is attached to the body 96 a (only a part is shown) of the speed detection device 96 by being screwed into the nut 95.

The protrusion 97a of the rotor 97 that rotates in the direction of the broken line in FIG.
Even when it is close to 4a, it is arranged in a transmission housing (not shown) with a predetermined gap 98 (for example, about 1 mm). If there is no gap 98, the proximity sensor 90 and the protrusion 97a may come into contact with each other and be damaged, leading to a decrease in detection accuracy. Further, even if the gap 98 is too wide, a change in the oscillation amplitude cannot be detected, and there is a possibility that the detection accuracy is similarly lowered.

JP 2002-76870 A Japanese Patent Laid-Open No. 62-163970

However, since the conventional proximity sensor 90 is disposed with a gap 98 with respect to the protrusion 97a, the dimensional accuracy of the thread groove 92c and the nut 95 is improved, or the tightening torque thereof is adjusted strictly. It was necessary to do and was very troublesome. In particular, when the proximity sensor 90 is disposed in the transmission housing as described above, the tightening torque cannot be adjusted while directly observing the rotor 97 and the tip end portion 94a of the core 94 by being blocked by the housing. The workability was poor.

The present invention has been made in view of the above reasons, and an object of the present invention is to provide a proximity sensor capable of improving workability without deteriorating the reliability of detection accuracy.

In order to achieve the above object, the invention according to claim 1 is an oscillation circuit section including an LC oscillation circuit having at least a rod-shaped core and an annular coil wound around the core, and a metal body or a magnetic body. A detection circuit unit for detecting the presence or absence of the detected object from a change in the oscillation amplitude of the LC oscillation circuit generated by the proximity of the detected object to the tip of the core, and a casing for storing these inside The tip of the core is formed in a curved shape, and a hole is provided at a position facing the tip of the core of the casing, and the core has a position where the tip projects from the hole to the outside of the casing. The tip is supported so as to be movable between the hole and a position hidden inside the casing, and when the detected object comes into contact with the tip of the core, the core is moved to a position hidden inside the casing. Circuit part Characterized in that it is configured to detect the presence of object to be detected.

According to the present invention, there is no gap between the tip portion of the core and the detected body, and the tip portion is formed in a curved shape even when the tip portion of the core and the detected body contact each other. Therefore, the frictional force generated at the time of contact is small, and furthermore, the component force acting in the longitudinal direction of the core out of the external force received from the detection object moves the core from the protruding position to the hidden position, resulting in energy loss. It is possible to suppress damage due to mutual contact. That is, the clearance between the tip of the core and the detected object may or may not be too wide, and it is possible to adjust the tightening torque flexibly on the assumption of contact. Therefore, workability can be improved without reducing the reliability of detection accuracy.

The invention of claim 2 is characterized in that, in the invention of claim 1, an elastic body for elastically urging the core toward the protruding position is disposed inside the casing.

According to the present invention, even if the longitudinal direction of the core is provided in any direction, when the detected object is not in contact with the tip of the core, the tip of the core is disposed at the protruding position. Can do.

According to a third aspect of the present invention, in the first or second aspect of the present invention, there is provided a regulating means for regulating the movement of the core at the hidden position.

According to the present invention, there is no gap between the tip of the core and the detected body, and even if the tip of the core and the detected body are in contact with each other, the detected body of the core is If the core moves from the protruding position to the hidden position in contact with the tip, the movement of the core to the protruding position is restricted, so that the energy received from the detected object by the subsequent contact is reduced. It can be set to zero, and damage due to contact can be further suppressed.

In the present invention, there is an effect that workability can be improved without lowering the reliability of detection accuracy.

It is sectional drawing when the to-be-detected body of Embodiment 1 of this invention approaches a core, (a) shows a non-contact state and (b) shows a contact state. It is a schematic block diagram in the same as the above. It is a circuit block diagram of the oscillation circuit part in the same as the above. It is sectional drawing when a to-be-detected body in the same as the above approaches a core, (a) is a non-contact state, (b) shows a contact state. It is sectional drawing when the to-be-detected body of Embodiment 2 of this invention approaches a core, (a) shows a non-contact state and (b) shows a contact state. It is sectional drawing of an example of the conventional proximity sensor.

(Embodiment 1)
Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS. In the following description, unless otherwise specified, the vertical and horizontal directions are defined in FIG. 1A, and the front of FIG.

As described in the prior art, the proximity sensor 1 of the present embodiment includes a transmission housing (not shown) via a speed detection device 10 in order to detect, for example, the traveling speed (speed) of an automobile and the rotation state of wheels. Installed inside. Here, in the housing, as shown in FIG. 1, a large number of protrusions 13a (only one is shown in FIG. 1) are rotated integrally with the rotating shaft and at a predetermined interval on the circumferential portion along the rotation direction. The rotor 13 made of a magnetic material on which is formed) is installed. That is, the proximity sensor 1 is used to detect the rotational speed of the protrusion 13a of the rotor 13 as a detection target. As shown in FIGS. 1 and 2, the proximity sensor 1 includes an oscillation circuit unit 2, a detection circuit unit 3, an output circuit unit 4, and a circuit board 5 on which circuit components constituting each circuit unit are mounted. And a casing 6 for housing the circuit board 5 therein.

As shown in FIG. 3, the oscillation circuit unit 2 includes an LC oscillation circuit 21, a bias circuit 22, a level shift circuit 23, a voltage-current conversion circuit 24, and a current mirror circuit 25. As shown in FIGS. 1 and 3, the LC oscillation circuit 21 includes a core 11 formed in a rod shape and having a tip 11 a formed in a curved surface, an annular coil L <b> 1 wound around the core 11, and a capacitor C
1 and. The core 11 is fitted into a substantially cylindrical coil bobbin 12 having both ends opened, and the annular coil L1 is wound around the core 11 via the coil bobbin 12. As shown in FIG. 3, the bias circuit 22 includes a current mirror circuit including transistors Tr4 and Tr5 and a resistor R1, and supplies a constant bypass current Ib to the LC oscillation circuit 21. The level shift circuit 23 is constituted by an NPN transistor Tr6 that is short-circuited between the base and collector and operates as a diode, and shifts the voltage level (oscillation amplitude) VT generated in the LC oscillation circuit 21 to the voltage V1. The voltage-current conversion circuit 24 includes a transistor Tr1, and a resistor Re for setting a feedback current is connected between the emitter of the transistor Tr1 and the circuit ground. The collector current of the transistor Tr1 It flows to the transistor Tr2. The current mirror circuit 25 includes a transistor Tr2
, Tr3 constitute a current mirror circuit, and the collector current Ifb of Tr3 is fed back to the LC oscillation circuit 21.

When the detected object made of a metal body or a magnetic body is not close to the core 11, the LC oscillation circuit 21 oscillates and the oscillation amplitude VT becomes a sufficiently large value. On the other hand, when the object to be detected comes close to the core 11, the oscillation amplitude VT becomes small due to the increase in eddy current loss of the annular coil L1, and the oscillation operation is stopped. Here, as shown in FIG. 2, the oscillation circuit unit 2 continues to output the oscillation amplitude VT to the detection circuit unit 3 while the proximity sensor 1 is in operation. The detection circuit unit 3 compares whether or not the input oscillation amplitude VT exceeds a predetermined threshold value, and the LC oscillation circuit 21 stops the oscillation operation only when it does not exceed the predetermined threshold value. A detection signal is generated by determining that the detection object is present in proximity. Then, the detection signal is output to the input circuit unit 10 b of the speed detection device 10 connected via the output circuit unit 4. For example, the speed detection device 10 calculates the speed from the count number of the detection signals input per certain time, and displays the speed on a display (not shown). Note that power supply for driving these circuit units is performed through a harness cable (not shown) connected to the speed detection device 10.

As shown in FIG. 1, the casing 6 is formed in a hollow, generally cylindrical shape as a whole, and includes a main body portion 61 that houses the circuit board 5 therein, and an insertion portion 61 a that penetrates the lower portion of the main body portion 61.
It is comprised from the accommodating part 62 which accommodates in the inside and accommodates the core 11 which cyclic | annular coil L1 winds. A thread groove 8 is formed on the peripheral surface of the main body 61 and is fitted to the nut 10 a by fitting with the nut 9. And a terminal portion of the input circuit portion 10b of the speed detection device 10 are electrically connected.

As shown in FIG. 1, the storage portion 62 is formed in a hollow cylindrical shape, and its inner diameter is set to a size that is slightly larger than the outer diameter of the core 11 (including the coil bobbin 12 and the annular coil L1). . Further, a hole 62c is provided through the lower end 62a of the storage portion 62. However, the hole 6
The inner diameter of 2c is formed such that the tip 11a formed in the curved shape of the core 11 protrudes to the outside of the storage portion 62 and the core 11 does not fall out of the storage portion 62. A lead-out hole (not shown) is provided through the upper end 62b of the storage part 62, and the lead wires 7, 7 connected to both ends of the annular coil L1 are connected to the circuit board 5 through the lead-out hole. Is done.

And since the core 11 of this embodiment is not fixed inside the accommodating part 62, the front-end | tip part 1
Between a position where 1a protrudes outside the casing 6 from the hole 62c (hereinafter abbreviated as a protruding position) and a position where the tip 11a is hidden inside the casing 6 from the hole 62c (hereinafter abbreviated as a hidden position). It is supported so that it can move freely.

Hereinafter, the operation of the proximity sensor 1 of the present embodiment will be described. First, as shown in FIG. 1 (a), when the protrusion 13a of the rotor 13 comes close, a gap 1 is formed between the tip 11a of the core 11 and the gap.
When there is 4, there is no problem as in the case of the conventional proximity sensor 90. At this time, the core 11 is in the protruding position. On the other hand, as shown in FIG. 1B, when the protrusion 13a of the rotor 13 approaches, if there is no gap 14 between the tip 11a of the core 11, the rotating rotor 1 rotates.
The three protrusions 13a come into contact with the tip 11a of the core 11 that is stationary. However, the core 11
Since the tip portion 11a is formed in a curved surface shape, the frictional force generated at the time of contact is small, and the component force acting upward from the two components of the external force received from the rotor 13 in the vertical and horizontal directions is the core. Energy is lost by moving 11 from the protruding position to the hidden position, and damage due to mutual contact can be suppressed. In other words, the gap 14 between the tip 11a of the core 11 and the rotor 13 may or may not be too wide. That is, the proximity sensor 1 of the present embodiment is in contact with the rotor 13. It is possible to adjust the tightening torque with flexibility. Therefore, workability can be improved without reducing the reliability of detection accuracy.

Note that the proximity sensor 1 of the present embodiment is not limited to detecting the rotational speed of the rotor 13 installed in the housing of the vehicle transmission, but in particular in the housing as described above. When arranging, the tip 11 of the core 11 is blocked by the housing.
The effect can be obtained when the tightening torque cannot be adjusted while directly viewing a and the object to be detected.

By the way, as shown in FIG. 1, the proximity sensor 1 is disposed in the housing with the longitudinal direction of the core 11 facing up and down and the tip 11a of the core 11 facing down. Therefore, the rotor 1
When the three protrusions 13a are not close to the core 11 or when there is a gap 14 that does not come into contact with the core 11, the core 11 moves to the protruding position due to its own weight. But,
When the proximity sensor 1 is disposed in the housing with the tip 11a of the core 11 facing upward, the core 11 always stays in the hidden position due to its own weight, and the above-described effects are not achieved.

Therefore, as shown in FIGS. 4A and 4B, a spring body 15 that elastically biases the core 11 toward the protruding position may be disposed inside the storage portion 62. That is, the spring body 15 is placed in the storage portion 62.
When the projecting portion 13a of the rotor 13 is not close to the core 11, no matter which direction the longitudinal direction of the core 11 is arranged, the intermediate portion is interposed between the upper end portion 62b and the core 11. Alternatively, when there is a gap 14 that is close enough not to contact, the core 11 can be arranged at the protruding position, and the same effect as described above can be obtained. The urging force of the spring body 15 needs to be set to be strong enough to resist the weight of the core 11 and to be weaker than the component force of the external force received from the rotor 13 in the longitudinal direction of the core 11.
(Embodiment 2)
Hereinafter, Embodiment 2 of the present invention will be described with reference to FIG. Since the basic configuration of this embodiment is the same as that of the first embodiment, common components are denoted by the same reference numerals and description thereof is omitted.

The core 11 of the first embodiment described above moves to the hidden position when one projecting portion 13a comes into close proximity, but returns to the projecting position by its own weight or the spring body 15 when the projecting portion 13a is separated. And since the next adjacent protrusion 13a approaches again and contacts, the energy received from the rotor 13 does not become substantially zero. On the other hand, the proximity sensor 1 according to the present embodiment is characterized in that the proximity sensor 1 includes a regulation unit that regulates the movement of the core 11 in the storage unit 62 at the hidden position.

That is, as shown in FIG. 5 (a), the upper end portion 62b of the storage portion 62 is opposed to the upper end portion of the core 11 as the restricting means and is recessed substantially in the same shape as the outer shape of the upper end portion of the core 11. 1
6 is provided. And when the core 11 exists in a protrusion position, it fits with the groove part 16 to such an extent that it can move to an up-down direction. Here, as shown in FIG. 5 (b), when the protrusion 13 a of the rotor 13 comes into contact with the core 11, the external force received from the rotor 13 in the longitudinal direction of the core 11 is applied as in the first embodiment. As a result, the core 11 is pushed upward. However, the inner peripheral surface of the groove portion 16 is slightly expanded in a trumpet shape downward, and the core 11 is firmly inserted to the extent that it does not fall off the groove portion 16 by being pushed upward by the component force. The

Therefore, even if there is no gap 14 between the tip 11a of the core 11 and the protrusion 13a of the rotor 13, and the tip 11a and the protrusion 13a are in contact with each other, the protrusion 13a.
If the core 11 moves from the projecting position to the hidden position by contacting the tip portion 11a, the core 11 is firmly inserted into the groove 16 to restrict the movement of the core 11 to the projecting position. The energy received from the rotor 13 by the contact can be made substantially zero, and damage due to the contact can be further suppressed.

DESCRIPTION OF SYMBOLS 1 Proximity sensor 2 Oscillation circuit part 3 Detection circuit part 6 Casing 11 Core 11a Tip part 13 Rotor 13a Protrusion part 21 LC oscillation circuit 62c Hole part L1 Ring coil

Claims (3)

Core formed at least on the rod-shaped, and an oscillation circuit unit provided with the LC oscillator having an annular coil wound around the core, by a metal body or a magnetic body or Ranaru object to be detected is close to the distal end of the core A detection circuit unit for detecting presence / absence of a detection target from a change in oscillation amplitude of the generated LC oscillation circuit, and a casing for storing these in the interior, wherein the tip of the core is formed in a curved shape, A hole is provided at a position facing the tip of the core,
The core is supported movably between a position where the tip portion protrudes outside the casing from the hole portion and a position where the tip portion is hidden inside the casing from the hole portion, and the detected object contacts the tip portion of the core. A proximity sensor, wherein the detection circuit unit is configured to detect the presence of the detected object in a state where the core is moved to a position hidden inside the casing.   The proximity sensor according to claim 1, wherein an elastic body that elastically biases the core toward the protruding position is disposed inside the casing.   The proximity sensor according to claim 1, further comprising a regulating unit that regulates the movement of the core at the hidden position.

Images