JP2020169833A - Rotational speed sensor - Google Patents

Abstract

To provide a rotational speed sensor equipped with a sensor head having a plurality of sensor ICs buried, in which the reliability of the rotational speed sensor is improved.SOLUTION: A rotational speed sensor comprises a sensor head, two sensor ICs buried in the sensor head, and a cable 3 with its end located inside of the sensor head. Stranded wires composed of insulated electric wires 61a, 61b connected to one of the two sensor ICs and insulated electric wires 62a, 62b connected to the other sensor IC pass through the inside of the cable 3. Out of the insulated electric wires 61a, 61b and 62a, 62 arranged at positions corresponding to the four corners of a square in a cross section of the cable 3, the insulated electric wires 61a, 61b are arranged at the diagonal positions of the square and the insulated electric wires 62a, 62b are arranged at the other diagonal positions of the square.SELECTED DRAWING: Figure 8

Description

The present invention relates to a sensor that detects the rotational speed of an object, and more particularly to a sensor that is suitable for detecting the rotational speed of a wheel.

Today, vehicles such as automobiles and motorcycles are equipped with various sensors, and one of the sensors for these vehicles is a rotation speed sensor. The rotation speed sensor is mounted on the vehicle, for example, for the purpose of detecting the rotation speed of the wheels. A rotational speed sensor mounted on a vehicle for this purpose is generally called a wheel speed sensor. The rotation speed sensor as a wheel speed sensor is mounted on the vehicle as one of the components such as an anti-lock braking system (ABS system) that prevents the wheels from locking or a traction control system that prevents the wheels from slipping.

The wheel speed sensor as described above has a cable constituting a signal transmission line, a sensor head provided on one end side of the cable, and a connector provided on the other end side of the cable. The sensor head has a built-in magnetic sensor IC (hereinafter, referred to as “sensor IC”) including a detection element such as a Hall element or a magnetoresistive effect element. The sensor head is located in the vicinity of a magnet encoder or rotor that rotates with the wheels. The sensor IC (detection element) built into the sensor head detects the magnetic field fluctuation around the sensor head generated by the rotation of the magnet encoder or rotor, and an electric signal corresponding to this magnetic field fluctuation (wheel rotation speed). Is output. The electric signal output from the sensor IC is transmitted by a cable and input to a control unit or a control device via a connector.

Conventionally, only one sensor IC is built in the sensor head. On the other hand, with the development of automatic driving systems or driving support systems, improvements in reliability and stability of rotational speed sensors including wheel speed sensors are required. Therefore, it is considered to increase the number of sensor ICs built in the sensor head to improve the reliability and stability of the rotational speed sensor. That is, redundancy of the rotation speed sensor is being studied.

Patent Document 1 (Japanese Unexamined Patent Publication No. 2017-96828) describes a wheel speed sensor equipped with two detection element units. Here, the two wires connected to the detection element section are combined into one sheathed wire, and the sheathed wires connected to each of the two detection element section sensors are combined into one rubber tube, for a total of four. The wires are grouped together.

JP-A-2017-96828

When two sensor ICs are built in the sensor head due to the redundancy of the rotation speed sensor, two electric wires (Vcc wiring and GND wiring for sensor power supply) connected to each sensor IC, that is, a total of four electric wires are used as one. It is conceivable to put them together. When four electric wires connected to two sensor ICs operating at the same time are combined into one, a problem (crosstalk) occurs in which noise flows through the other pair of electric wires due to the magnetic field generated from one pair of electric wires. Therefore, it is an issue to suppress the occurrence of crosstalk and thereby improve the reliability of the rotational speed sensor.

Other challenges and novel features will become apparent from the description and accompanying drawings herein.

A brief overview of typical embodiments disclosed in the present application is as follows.

The rotational speed sensor according to one embodiment includes a sensor head made of resin, first sensor ICs and second sensor ICs embedded in the sensor heads, and first sensor ICs whose ends are located in the sensor heads. It is provided with a cable having a stranded wire composed of a first insulated wire and a second insulated wire connected to the sensor IC and a third insulated wire and a fourth insulated wire connected to the second sensor IC. Of the four insulated wires arranged at positions corresponding to the four corners of the cable in the cross section of the cable, the first insulated wire and the second insulated wire are arranged at diagonal positions of the square, and the third insulated wire and the third insulated wire The fourth insulated wire is arranged at another diagonal position of the square.

According to the present invention, the reliability of the rotational speed sensor can be improved.

It is the schematic which shows the structure of the rotation speed sensor which concerns on one Embodiment. It is a perspective view of the sensor head shown in FIG. It is a perspective view of the sensor head shown in FIG. It is sectional drawing in line AA of the sensor head shown in FIG. It is a perspective view which shows the connection state of the sensor IC and a cable in the sensor head shown in FIG. It is a top view which shows the connection state of the sensor IC and a cable in the sensor head shown in FIG. It is a bottom view which shows the connection state of the sensor IC and a cable in the sensor head shown in FIG. It is sectional drawing in the BB line of the cable shown in FIG. It is the schematic which shows the connection state of the sensor IC and a cable in the sensor head shown in FIG. It is sectional drawing of the cable which comprises the rotational speed sensor which concerns on one Embodiment. It is the schematic which shows the connection state of the sensor IC and the cable in the sensor head of the rotation speed sensor which concerns on the modification of one Embodiment.

Hereinafter, an example of the embodiment of the rotational speed sensor of the present invention will be described in detail with reference to the drawings. The rotation speed sensor according to the present embodiment is a wheel speed sensor mounted on a vehicle as one of the components of the ABS system.

<Structure of rotational speed sensor of this embodiment>
2 and 3 used in the following description are perspective views showing the sensor head 2 from different directions. However, in FIG. 3, the cable 3, the sensors ICs 41 and 42, the terminals between them, the insulated wire, and the like are shown transparently.

As shown in FIG. 1, the wheel speed sensor 1A, which is the rotation speed sensor according to the present embodiment, has a sensor head 2, a cable 3, and a connector 4. The sensor head 2 is arranged in the vicinity of a magnet encoder 5 that rotates together with a wheel (not shown). Specifically, the sensor head 2 is fixed to the vehicle body (hub, knuckle, suspension, etc.) so that the positional relationship with the magnet encoder 5 has a predetermined positional relationship. N-pole portions and S-pole portions are alternately provided on the peripheral edge of the magnet encoder 5 along the rotation direction of the magnet encoder 5. Therefore, when the magnet encoder 5 rotates with the rotation of the wheels, a magnetic field fluctuation occurs around the sensor head 2. The sensor head 2 has a built-in magnetic sensor IC (sensor IC) that detects magnetic field fluctuations and outputs an electric signal corresponding to the magnetic field fluctuations. Further, the sensor head 2 and the connector 4 are connected via a single cable 3. The electric signal output from the sensor IC built in the sensor head 2 is transmitted to the connector 4 via the cable 3 and input to the connection destination of the connector 4. The connector 4 is connected to, for example, a control unit or control device of an ABS system, or a control unit or control device that collectively controls various systems including the ABS system.

As shown in FIGS. 1, 2 and 3, the sensor head 2 includes a flange portion 10, a sensor holding portion 20 provided on one side of the flange portion 10, and a cable provided on the other side of the flange portion 10. The holding unit 30 and the like are included. The flange portion 10, the sensor holding portion 20, and the cable holding portion 30 are integrally molded with resin. In other words, each of the flange portion 10, the sensor holding portion 20, and the cable holding portion 30 is a part of the injection-molded resin molded body.

As shown in FIG. 1, the flange portion 10 has a front surface 11a and a back surface 11b parallel to each other, and has a substantially plate-like appearance as a whole. As shown in FIGS. 1, 2 and 3, the flange portion 10 is provided with a through hole 12 through which a fixing member (for example, a bolt) for fixing the sensor head 2 at a predetermined position is inserted. The through hole 12 penetrates the flange portion 10 in the thickness direction of the flange portion 10, one end of the through hole 12 opens at the front surface 11a of the flange portion 10, and the other end of the through hole 12 is the back surface of the flange portion 10. It is open at 11b. As shown in FIG. 2, an annular reinforcing member 13 is provided inside the through hole 12. The reinforcing member 13 in the present embodiment is made of metal, but the reinforcing member 13 is not limited to metal, and may be made of resin, for example.

As shown in FIGS. 1, 2 and 3, the sensor holding portion 20 and the cable holding portion 30 generally have a tubular appearance as a whole. More specifically, the sensor holding portion 20 projects forward from the front surface 11a of the flange portion 10, and has a substantially cylindrical appearance on the root side and a substantially square tubular appearance on the tip side. On the other hand, the cable holding portion 30 protrudes from the back surface 11b of the flange portion 10 to the rear opposite to the front, and has a substantially cylindrical appearance over the entire length.

Here, the thickness direction of the flange portion 10 is defined as the “front-back direction”, and the height direction (longitudinal direction) of the flange portion 10 is defined as the “vertical direction”. Further, the direction orthogonal to both the front-rear direction and the up-down direction is defined as the "left-right direction". Further, regarding the front-rear direction, the protruding direction (first direction) of the sensor holding portion 20 with respect to the flange portion 10 is "forward", and the protruding direction (second direction) of the cable holding portion 30 with respect to the flange portion 10 is "rear". .. Regarding the vertical direction, the side where the through hole 12 is provided is referred to as "downward", and the side opposite to the side where the through hole 12 is provided is referred to as "upward" (third direction). Further, the root side of the sensor holding portion 20 having a substantially cylindrical appearance is called a "base end portion 20a", and the tip end side of the sensor holding portion 20 having a substantially cylindrical appearance is referred to as a "tip portion 20b". May be called. In other words, the portion exhibiting a substantially cylindrical appearance is the base end portion 20a, and the portion exhibiting a substantially square tubular appearance is the tip end portion 20b.

As shown in FIGS. 3 and 4, the sensor head 2 contains a plurality of sensor ICs 40 including a detection element for detecting magnetic field fluctuations. In other words, the sensor head 2 contains a plurality of sensor ICs 40 that output an electric signal corresponding to the fluctuation of the magnetic field. In the present embodiment, a total of two sensor ICs (first sensor IC) 41 and sensor IC (second sensor IC) 42 are embedded in the tip of the sensor holding portion 20. More specifically, the two sensors ICs 41 and 42 are embedded in the vicinity of the end face of the tip end portion 20b of the sensor holding portion 20.

Each of the sensors ICs 41 and 42 includes magnetoresistive elements 41c and 42c as detection elements. The magnetoresistive elements 41c and 42c in the present embodiment are giant magnetoresistive elements (GMR (Giant Magneto Resistive effect) elements). The sensors ICs 41 and 42 are stacked one above the other with both detection surfaces facing upward. In the following description, the sensor IC 41 may be referred to as an "upper sensor IC 41" and the sensor IC 42 may be referred to as a "lower sensor IC 42" for distinction. However, such a distinction is merely a distinction for convenience of explanation. On the other hand, the sensors ICs 41 and 42 may be collectively referred to as "sensor IC40".

As shown in FIG. 4, the tip of the cable 3 is connected to the sensor head 2. Specifically, the end of the cable 3 is covered with the cable holding portion 30. That is, the end of the cable 3 is molded into the cable holding portion 30. As a result, the cable 3 extends rearward from the end surface 30a of the cable holding portion 30. FIG. 4 is a cross-sectional view taken along the line AA of the sensor head shown in FIG. 2, but the four insulated wires passing through the cable 3 are shown not in cross section but in the side view from the left.

As shown in FIGS. 4 to 7, the cable 3 is a multi-core cable including four core wires 50. More specifically, the cable 3 is a multi-core cable including a pair of core wires 50 connected to the upper sensor IC 41 and another pair of core wires 50 connected to the lower sensor IC 42. FIG. 6 is a plan view of the structure shown in FIG. 5 viewed from above, and FIG. 7 is a plan view and bottom view of the structure shown in FIG. 5 viewed from below.

As shown in FIG. 5, each core wire 50 is covered with an insulator (insulating film) 55. Further, each core wire 50 covered with the insulator 55 is collectively covered with a sheath (skin, insulator) 56 in a twisted state (see FIG. 4). Specifically, the insulator 55 that covers the core wire 51a and the core wire 51a constitutes an insulated wire (first insulated wire) 61a, and the insulator 55 that covers the core wire 51b and the core wire 51b is an insulated wire (second insulating wire). (Electric wire) 61b (see FIGS. 5 and 6). Further, the insulator 55 that covers the core wire 52a and the core wire 52a constitutes an insulated wire (third insulated wire) 62a, and the insulator 55 that covers the core wire 52b and the core wire 52b is an insulated wire (fourth insulated wire) 62b. (See FIGS. 5 and 7).

That is, the cable 3 has four insulated wires 61a, 61b, 62a and 62b twisted together, and a sheath 56 that collectively covers the four insulated wires 61a, 61b, 62a and 62b and puts them together. It is a core cable. The core wire 50 in the present embodiment is a stranded wire composed of a plurality of copper alloy wires containing tin. The insulator 55 is made of flame-retardant cross-linked polyethylene, and the sheath 56 is made of thermoplastic urethane. Of course, the materials of the core wire 50, the insulator 55, and the sheath 56 are not limited to the above materials.

As shown in FIGS. 6 and 7, the four core wires 50 included in the cable 3 are electrically connected to a predetermined sensor IC 40. Specifically, as shown in FIG. 6, two core wires 51a and 51b are connected to the upper sensor IC 41, and as shown in FIG. 7, the other two core wires 52a and 52b are connected to the lower sensor IC 42. There is. More specifically, the core wire 51a is connected to the input terminal (first terminal) 41a of the upper sensor IC 41, and the core wire 51b is connected to the output terminal (second terminal) 41b of the upper sensor IC 41. Similarly, the core wire 52a is connected to the input terminal (third terminal) 42a of the lower sensor IC 42, and the core wire 52b is connected to the output terminal (fourth terminal) 42b of the lower sensor IC 42.

Each of the input terminals 41a and 42a and the output terminals 41b and 42b has a strip shape. Then, the core wire 51a is resistance welded to the input terminal 41a, and the core wire 51b is resistance welded to the output terminal 41b. Further, the core wire 52a is resistance welded to the input terminal 42a, and the core wire 52b is resistance welded to the output terminal 42b. In the following description, the input terminal 41a and the output terminal 41b may be collectively referred to as "terminal 57", and the input terminal 42a and the output terminal 42b may be collectively referred to as "terminal 58".

The end of the sheath 56, the core wire 50, the terminal 57, the terminal 58, and the main body of the sensor IC 40 shown in FIGS. 4, 6 and 7 are held by the holder 60. In other words, the sensor IC 40 including the end of the sheath 56, the core wire 50, the terminal 57 and the terminal 58 is built in the sensor head 2 shown in FIG. 2 while being held by the holder 60. In FIGS. 6 and 7, the specific shapes of the plate-shaped separators 66 and 67 and the side wall portions 64 and 65 constituting the holder 60 are not shown, and are shown by alternate long and short dash lines.

The holder 60 has a pair of side wall portions 64, 65 facing each other and a support plate 63 straddling the side wall portions 64, 65. The upper sensor IC 41 (see FIGS. 5 and 6) including the core wires 51a and 51b and the terminal 57 is arranged on the upper surface side of the support plate 63. On the other hand, the lower sensor IC 42 (see FIGS. 5 and 7) including the core wires 52a and 52b and the terminal 58 is arranged on the lower surface side of the support plate 63.

A plate-shaped separator 66 interposed between the core wires 51a and 51b is provided so as to project. In other words, the separator 66 is a partition wall interposed between a pair of core wires 51a and 51b connected to the same sensor IC (upper sensor IC41). A separator 67 similar to the separator 66 is projected on the lower surface of the support plate 63. The separator 67 is also a partition wall interposed between the pair of core wires 52a and 52b connected to the same sensor IC (lower sensor IC 42).

As shown in FIG. 6, the separator 66 extends forward beyond the ends of the core wires 51a and 51b, and is interposed between the input terminal 41a and the output terminal 41b. As shown in FIG. 7, the separator 67 extends forward beyond the ends of the core wires 52a and 52b, and is interposed between the input terminal 42a and the output terminal 42b. As a result, the core wire 51a and the input terminal 41a are arranged between the separator 66 and the upper portion of the side wall portion 64, and the core wire 51b and the output terminal 41b are arranged between the separator 66 and the upper portion of the side wall portion 65. (See FIG. 6). Further, the core wire 52a and the input terminal 42a are arranged between the separator 67 and the lower portion of the side wall portion 64, and the core wire 52b and the output terminal 42b are arranged between the separator 67 and the lower portion of the side wall portion 65 ( (See FIG. 7).

The separator 66 shown in FIG. 6 plays a role of positioning the core wires 51a and 51b, the input terminal 41a and the output terminal 41b at predetermined positions on the holder 60, short-circuits the core wire 51a and the core wire 51b, and causes the input terminal 41a. It plays a role of preventing a short circuit with the output terminal 41b. The separator 67 shown in FIG. 7 plays a role of positioning the core wires 52a and 52b, the input terminal 42a and the output terminal 42b at predetermined positions on the holder 60, short-circuits the core wire 52a and the core wire 52b, and causes the input terminal 42a. It plays a role of preventing a short circuit with the output terminal 42b.

As shown in FIG. 8, four insulated wires 61a, 61b, 62a and 62b pass through the sheath 56 constituting the cable 3. That is, the cable 3 is a bundle of four insulated wires 61a, 61b, 62a and 62b.

The cross section of the cable 3 shown in FIG. 8 is a cross section along the lateral direction (diameter direction) of the cable 3 and is a cross section orthogonal to the extending direction of the cable 3. In the cross section, the four insulated wires 61a, 61b, 62a and 62b are located, for example, at the four corners of a virtual regular quadrangle along the cross section. That is, the insulated wires 61a, 61b, 62a and 62b are arranged in a matrix. Here, in the cross section, the insulated wires 62a and 61b are aligned with each other in the first direction, and the insulated wires 61a and 62b are aligned with each other in the first direction. Further, in the cross section, the insulated wires 61a and 62a are aligned with each other in the second direction, and the insulated wires 62b and 61b are aligned with each other in the second direction. The first direction and the second direction are directions along the cross section and intersect with each other. The first direction and the second direction are, for example, orthogonal to each other.

That is, in the cross section, the four insulated wires 61a, 61b, 62a and 62b are located at the four corners of the virtual quadrangle, respectively, and the insulated wires 61a and 61b connected to the sensor IC 41 are of the quadrangle. The insulated wires 62a and 62b arranged at diagonal positions and connected to the sensor IC 42 are arranged at other diagonal positions of the quadrangle.

Further, the positions of the other pair of insulated wires may be exchanged with respect to one pair of insulated wires arranged at diagonal positions of the quadrangle. That is, for example, the insulated wire 62a and the insulated wire 62b in FIG. 8 may be replaced with each other. In that case, in the cross section, the insulated wires 61a and 62b are aligned with each other in the first direction, the insulated wires 62a and 61b are aligned with each other in the first direction, the insulated wires 61a and 62a are aligned with each other in the second direction, and the insulated wires 62b, 61b are aligned with each other in the second direction.

FIG. 9 shows a schematic view of a state in which the sensors ICs 41 and 42 in the sensor head 2 (see FIG. 2) are not overlapped in the vertical direction but arranged side by side (expanded state). Note that FIG. 9 shows a state in which the sensors ICs 41 and 42 are deployed, and at least a part of the sensors ICs 41 and 42 embedded in the actual sensor head 2 overlap each other. That is, the configuration shown in FIG. 9 does not indicate the arrangement of the sensors ICs 41 and 42 of the present embodiment.

The upper sensor IC 41 has a layout close to a rectangle, for example, in a plan view. The plan view referred to here means viewing the upper sensor IC 41 from a direction (upper side) orthogonal to the detection surface (main surface, first surface) of the sensor IC. The input terminal 41a and the output terminal 41b extend from one side of the substantially rectangular upper sensor IC 41 in a plan view, and are aligned with each other along the one side. The lower sensor IC 42 is the same element having the same function and structure as the upper sensor IC 41. Therefore, the input terminal 42a and the output terminal 42b extend from one side of the substantially rectangular lower sensor IC 42 in a plan view, and are aligned with each other along the one side.

In FIG. 9, the detection surface of the upper sensor IC 41 is directed upward, and the detection surface of the lower sensor IC 42 is directed downward. That is, in FIG. 9, the back surface (first back surface) opposite to the detection surface (main surface, first detection surface) of the upper sensor IC 41 faces downward, and the detection surface (main surface, second detection surface) of the lower sensor IC 42 faces downward. The back side (second back side) on the opposite side of) is facing upward. In the process of connecting the core wire 50 to each of the sensors IC 41 and 42, the sensors IC 41 and 42 are oriented so that the main surface (upper surface) of the two upper sensor IC 41 and the back surface (lower surface) of the lower sensor IC 42 face upward. It is conceivable to weld the core wire 50 to the terminals 57 and 58 in that state. After that, by changing the directions of the sensors ICs 41 and 42 by 90 degrees in opposite directions, the sensors ICs 41 and 42 can be overlapped with the detection surfaces facing the same direction. However, in this connection step, the detection surfaces of the sensors IC 41 and 42 may face either upward or downward.

In each of the drawings of the present application, the sensors ICs 41 and 42 have a substantially rectangular planar shape so that the directions of the detection surface and the back surface of the sensors ICs 41 and 42 can be easily understood. The part is shown. On the other hand, the planar shape of the sensor IC 41 may be symmetrical in the direction in which the input terminals 41a and the output terminals 41b are lined up. The same applies to the sensor IC 42.

Further, the detection surfaces of the sensors IC 41 and 42 do not have to face completely in the same direction. In other words, the detection surfaces of the sensors IC 41 and 42 do not have to be perfectly parallel.

The input terminal 41a is a power supply voltage terminal for supplying a power supply voltage (Vcc) to the upper sensor IC 41, and the insulated wire 61a including the core wire 51a connected to the input terminal 41a is a power supply wiring (plus wiring, input wiring). Is. The output terminal 41b is a ground terminal for connecting the upper sensor IC 41 to a ground potential (GND), and the insulated wire 61b including the core wire 51b connected to the output terminal 41b is a ground wire (minus wiring, output wiring). ).

Similarly, the input terminal 42a is a power supply voltage terminal for supplying a power supply voltage (Vcc) to the lower sensor IC 42, and the insulated wire 62a including the core wire 52a connected to the input terminal 42a is a power supply wiring (plus wiring). , Input wiring). The output terminal 42b is a ground terminal for connecting the lower sensor IC 42 to the ground potential (GND), and the insulated wire 62b including the core wire 52b connected to the output terminal 42b is a ground wire (minus wiring, output). Wiring).

As shown in FIG. 5, the sensors ICs 41 and 42 and the cable connected to each other in this way are stacked one above the other with their detection surfaces facing upward. This is because each of the sensors ICs 41 and 42 has the same function. One of the sensors ICs 41 and 42 is a spare element provided to prevent the rotation speed sensor from losing its function and not operating normally when, for example, the other fails due to a failure or the like. .. Therefore, the detection surfaces of the sensors IC 41 and 42 need to face the same direction. In other words, the back surface of the upper sensor IC 41 and the detection surface of the lower sensor IC 42 face each other.

If the detection surfaces of the sensors IC 41 and 42 are facing different directions, the wheel rotation direction detected by the sensor IC 41 and the wheel rotation direction detected by the sensor IC 41 are different from each other. Therefore, one of the sensor ICs cannot be used as a spare. Here, the detection surface of the sensor IC and the back surface are expressed separately, but it can be said that the back surface is also a detection surface capable of detecting the rotational speed of the wheel. However, when the back surface faces the wheel side, reverse rotation is detected unlike the case where the detection surface faces the wheel side.

In the normal state, the sensors ICs 41 and 42 operate at the same time. Therefore, current signals of the same magnitude flow through the core wires 51a and 52a at the same time, and current signals of the same magnitude flow through the core wires 51b and 52b at the same time.

Looking at the sensor ICs 41 and 42 from the end of the sheath 56 on the sensor head 2 (see FIG. 3) side (hereinafter referred to as the sheath end) shown in FIG. 6, the input terminals 41a and the output terminals 41b are laterally oriented (hereinafter referred to as sheath ends). The input terminal 42a and the output terminal 42b are arranged in the horizontal direction (horizontal direction), and the input terminal 42a and the output terminal 42b are located below the input terminal 41a and the output terminal 41b, respectively. On the other hand, at the sheath end, among the insulated wires 61a, 61b, 62a and 62b arranged in a matrix, the insulated wires 61a and 61b are arranged at diagonal positions of the quadrangle and at other diagonal positions of the quadrangle. Insulated wires 62a and 62b are arranged. Therefore, at least two of the insulated wires 61a, 61b, 62a and 62b exposed from the sheath 56 in the sensor head 2 intersect with each other and twist.

<Effect of this embodiment>
When four electric wires (core wire and insulated wire) are twisted and bundled, crosstalk that occurs between the electric wires becomes a problem. Crosstalk means that when a magnetic field is generated by a current flowing through one or more electric wires, the current (induced noise) or the current (induced noise) flowing through an induced electromotive force in another electric wire passing through the magnetic field Refers to flowing. That is, crosstalk means that when a plurality of signal lines are adjacent to each other, the signal flowing through one signal line affects the other signal line.

Two sensor ICs are embedded in the sensor head, and among those sensor ICs, the input wiring and the output wiring connected to one sensor IC and the input wiring and the output wiring connected to the other sensor IC are included. In a cable including a stranded wire composed of four electric wires, crosstalk becomes a problem due to the arrangement of the four electric wires in the cable.

That is, when four electric wires are arranged in a matrix in a cross section along the radial direction of the cable, the input wiring and the output wiring connected to one of the two sensor ICs are in the row direction (or column direction). It is conceivable that the input wiring and the output wiring connected to the other sensor IC are arranged in a row direction (or column direction). In the rotational speed sensor of the comparative example using such a cable, when a current signal flows through the input wiring or the output wiring connected to one of the two sensor ICs, a magnetic field is generated around the wiring. Since the input wiring or output wiring connected to the other side passes through the magnetic field, a current (induced noise) flows through the input wiring or output wiring passing through the magnetic field due to the induced electromotive force.

The generation of crosstalk (induction noise) due to mutual interference as described above may cause a malfunction of the rotational speed sensor. For example, when performing a durability test on a rotational speed sensor, a high voltage is applied to a pair of insulated wires connected to one of the sensor ICs. Therefore, in the rotational speed sensor of the above comparative example, a large induced noise may occur in the pair of insulated wires connected to the other sensor IC during the durability test. Therefore, the other sensor IC may malfunction due to crosstalk.

Similarly, it is conceivable that some failure causes an abnormality in the power supply that supplies voltage to the rotation speed sensor, and a large current (for example, an inrush current) flows through the input wiring and the output wiring connected to any of the sensor ICs. At that time, the other sensor IC provided as a spare may cause a malfunction due to the induced current. This can be a factor that reduces the reliability of the rotational speed sensor.

On the other hand, in the present embodiment, as described with reference to FIG. 8, among the insulated wires 61a, 61b, 62a and 62b arranged in a matrix in the cross section of the cable 3, the insulated wires 61a and 61b are included in the cross section. The insulated wires 62a and 62b are arranged at diagonal positions of the quadrangle along the line, and the insulated wires 62a and 62b are arranged at other diagonal positions of the quadrangle. As a result, as shown in FIG. 10, in the magnetic field generated from each of the pair (first set) of electric wires (for example, insulated wires 61a and 61b) connected to one of the sensor ICs, the other. The pair (second set) of electric wires (here, insulated wires 62a and 62b) connected to the sensor IC of No. 1 do not pass. This is because the second set of electric wires are lined up at an intermediate position of the magnetic field generated by the current signal flowing through each of the first set of electric wires. Therefore, it is possible to suppress the occurrence of crosstalk in the second set of electric wires. This is the same even if the positions of the first group and the second group are exchanged. That is, since the first set of electric wires does not pass through the magnetic field generated by the current signal flowing through the second set of electric wires, it is possible to suppress the occurrence of crosstalk in the first set of electric wires. Therefore, the induced noise caused by crosstalk can be reduced in all of the four insulated wires 61a, 61b, 62a and 62b.

In FIG. 8, the four insulated wires 61a, 61b, 62a and 62b are separated from each other in the sheath 56, but adjacent insulated wires may be in contact with each other. That is, the insulated wires 61a and 61b may be in contact with the insulated wires 62a and 62b, respectively, and the insulated wires 62a and 62b may be in contact with the insulated wires 61a and 61b, respectively. Further, each of the four insulated wires 61a, 61b, 62a and 62b is located at four corners of a rectangle or a parallelogram (for example, a rhombus) instead of a regular quadrangle in a cross section along the radial direction of the cable 3. You may. However, from the viewpoint of reducing crosstalk, it is preferable that each of the four sides of the quadrangle has the same length. That is, it is desirable that the quadrangle is a square or a rhombus rather than a rectangle. In other words, it is desirable that the distance between the insulated wire 61a and each of the insulated wires 62a and 62b and the distance between the insulated wire 61b and each of the insulated wires 62a and 62b are equal.

Further, although the case where the sensors ICs 41 and 42 are separated from each other has been described here, the magnetoresistive effect elements 41c and 42c (see FIG. 4) are enclosed in the same resin to form one sensor IC. You may be. That is, the magnetoresistive elements 41c and 42c and the resin may form one sensor IC having four terminals 57 and 58, and the sensor IC may be enclosed in the sensor head 2. In other words, the sensors ICs 41 and 42 may be integrated with each other to form one sensor IC. On the other hand, when the magnetoresistive elements 41c and 42c are enclosed in the same resin to form one sensor IC, and the magnetoresistive elements 41c and 42c are arranged without overlapping, the following is a case. This will be described as a modification.

<Modification example>
As a method of making the rotation speed sensor redundant, it is conceivable to enclose the sensor IC formed by encapsulating (molding) two magnetoresistive elements in the same resin in the sensor head. As shown in FIG. 11, the present embodiment can also be applied when the magnetoresistive elements 41c and 42c are enclosed in the same resin and fixed to each other. In FIG. 11, the contours of the magnetoresistive elements 41c and 42c are shown by broken lines.

As shown in FIG. 11, one sensor IC 43 of this modified example has two magnetoresistive elements 41c and 42c inside. The magnetoresistive elements 41c and 42c are arranged side by side in the resin constituting the sensor IC 43 in the direction along their detection surfaces, and are separated from each other in a plan view. That is, at least a part of each of the magnetoresistive elements 41c and 42c is arranged side by side. The input terminal 41a, the output terminal 41b, the input terminal 42a, and the output terminal 42b extending from one side of the sensor IC 43 having a rectangular planar shape are arranged side by side in this direction. The input terminal 41a and the output terminal 41b are connected to the magnetoresistive element 41c, and the input terminal 42a and the output terminal 42b are connected to the magnetoresistive element 42c. The magnetoresistive elements 41c and 42c are arranged so that the same surface (detection surface) faces the same direction (upward direction). The magnetoresistive elements 41c and 42c are not electrically connected to each other and are insulated.

The structure of the cable 3, that is, the arrangement of the insulated wires 61a, 61b, 62a and 62b in the cable 3 is the same as that shown in FIG. As described above, even when the magnetoresistive elements 41c and 42c form one sensor IC43, the effect of reducing crosstalk can be obtained as in the case of the rotational speed sensor described with reference to FIGS. 1 to 10. .. That is, even when the magnetoresistive elements 41c and 42c do not overlap each other and are arranged in the lateral direction along the detection surface, the same effect as the rotational speed sensor described with reference to FIGS. 1 to 10 can be obtained. ..

Although the invention made by the present inventors has been specifically described above based on the embodiment thereof, the present invention is not limited to the embodiment and can be variously modified without departing from the gist thereof. is there.

For example, the detection element included in the sensor IC built in the sensor head is an anisotropic magnetoresistance effect element (AMR (Anisotropic magnetoresistance effect) element) or a tunnel magnetoresistance effect element (TMR (Tunnel magnetoresistance effect) element). It may be a Hall element.

The method of connecting the core wire and the output terminal of the sensor IC is not limited to welding, and may be, for example, soldering. Further, the core wire and the output terminal of the sensor IC may be connected via the connection terminal. In this case, for example, one end of the connection terminal and the core wire are caulked, and the other end of the connection terminal and the output terminal are caulked.

The present invention can be applied to a rotational speed sensor other than the wheel speed sensor, and when applied, the same effect as described above is obtained.

2 Sensor head 3 Cable 40 Sensor IC
41 Sensor IC (upper sensor IC)
41a, 42a Input terminal 41b, 42b Output terminal 42 Sensor IC (lower sensor IC)
41c, 42c Magnetoresistive element 50, 51a, 51b, 52a, 52b Core wire 61a, 61b, 62a, 62b Insulated wire

Claims (7)

The sensor head including the sensor holding part and the cable holding part,
A cable extending from the cable holding portion and
It has a first sensor IC and a second sensor IC, which are embedded in the sensor holding portion and output an electric signal corresponding to a magnetic field fluctuation.
The first sensor IC has a first detection surface, a first back surface opposite to the first detection surface, and first and second terminals.
The second sensor IC has a second detection surface, a second back surface opposite to the second detection surface, and a third terminal and a fourth terminal.
The cable includes a first insulated wire electrically connected to the first terminal, a second insulated wire electrically connected to the second terminal, and a third insulated wire electrically connected to the third terminal. A stranded wire composed of a three insulated wire and a fourth insulated wire electrically connected to the fourth terminal.
In the cross section along the radial direction of the cable, the first insulated wire and the third insulated wire are arranged in the first direction, and the second insulated wire and the fourth insulated wire are arranged in the first direction. The first insulated wire and the fourth insulated wire are arranged in a second direction intersecting with the first direction, and the second insulated wire and the third insulated wire are arranged in the second direction. Sensor. In the rotation speed sensor according to claim 1,
The first terminal is an input terminal of the first sensor IC.
The second terminal is an output terminal of the first sensor IC.
The third terminal is an input terminal of the second sensor IC.
The fourth terminal is a rotation speed sensor which is an output terminal of the second sensor IC. In the rotation speed sensor according to claim 1 or 2.
A part of the first sensor IC and a part of the second sensor IC overlap each other in a plan view.
A rotation speed sensor in which the first back surface and the second detection surface face each other. In the rotation speed sensor according to claim 1 or 2.
A part of the first sensor IC and a part of the second sensor IC are arranged side by side in a plan view.
A rotation speed sensor in which each of the first detection surface and the second detection surface faces a third direction. In the rotation speed sensor according to any one of claims 1 to 4.
The first sensor IC and the second sensor IC are integrated with each other to form one third sensor IC.
The third sensor IC is a rotation speed sensor embedded in the sensor holding portion. In the rotation speed sensor according to any one of claims 1 to 5.
Each of the first sensor IC and the second sensor IC is a rotational speed sensor including a magnetoresistive element as a detection element. In the rotation speed sensor according to any one of claims 1 to 6.
The first sensor IC and the second sensor IC are rotational speed sensors that operate at the same time.

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