JPH04324302A - Throttle position sensor - Google Patents

Abstract

PURPOSE:To achieve a stable detection accuracy without being affected by a normal displacement in axial direction of a shaft without any contact. CONSTITUTION:A detection element 10 where a magnetic resistance element 12 is adhered on a plate surface around a penetration hole 11a which is provided on a substrate 11 is stored in a housing 3 and is supported to a specified position. A shaft 2 is placed so that a tip portion in axial direction 2a penetrates a penetration hole 11a and is supported to the housing 3 so that it can rotate freely. A magnet 20 is provided at a position crossing the substrate 11 of the tip portion in axial direction 2a. A length of the magnet 20 in axial direction is obtained by adding a length in axial direction corresponding to a thickness of the magnetoresistance element 12 to at least a specified allowable displacement in axial direction of the shaft 2 and the normal displacement in axial direction for the shaft 2 does not cause the magnet 20 to leave the substrate surface.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a throttle position sensor installed in an internal combustion engine, and more particularly to a non-contact type throttle position sensor using a magnetic resistance element.

0002

2. Description of the Related Art An internal combustion engine equipped with an electronically controlled fuel injection system is equipped with a throttle position sensor, and its output signal is used for fuel injection control and the like. This throttle position sensor is connected to the throttle valve shaft, and normally outputs a throttle opening signal that changes depending on the throttle valve opening (hereinafter referred to as throttle opening) and an idle signal that turns on and off depending on whether it is in the idle range or output range. be done. Regarding such throttle position sensors, magnetic sensors are used to construct a contactless mechanism or to reduce inertia loss of the shaft. A resistance element is arranged.

Semiconductor magnetoresistive elements and ferromagnetic magnetoresistive elements are known as the above-mentioned magnetoresistive elements. The former utilizes the property that the electrical resistance of a semiconductor changes in a magnetic field. The latter utilizes the property that the resistance of a ferromagnetic material in a magnetic field changes anisotropically depending on the angle formed between the magnetization direction and the current direction. For example, JP-A-62-
As described in Japanese Patent No. 237302, a rotational position detecting device is known in which a ferromagnetic magnetoresistive element is provided on either an end face of a shaft or a position facing the end face, and a permanent magnet is provided on the other end.

The above-mentioned rotational position detection device can be applied to a throttle position sensor, but in the case where the permanent magnet and the plate surface of the magnetic resistance element are arranged facing each other as described in the above-mentioned publication, it is possible to apply the rotational position detection device to the shaft position sensor. The axial movement changes the magnetic field applied to the magnetoresistive element. Although the above-described ferromagnetic magnetoresistive element can function in a relatively small magnetic field, measurement errors may occur if the distance from the permanent magnet is large and sufficient magnetic flux is not applied to the magnetoresistive element. Therefore, it is necessary to maintain a predetermined distance between the plate surface of the magnetoresistive element and the permanent magnet. Although not specifically disclosed in the above publication, the shaft must be supported to prevent at least axial movement, the shaft support structure requires precision, and accurate assembly is required. becomes.

[0005] In order to solve this problem, the applicant has proposed various rotation angle sensors in order to be able to place the magnetoresistive element in a uniform magnetic field at all times.
It is disclosed in Japanese Patent No. 815. For example, the magnet member is formed of a permanent magnet with a substantially U-shaped cross section, a substrate is interposed between both open ends of this permanent magnet, and the plate surface of the substrate is parallel to the direction of magnetic flux between both open ends of the permanent magnet. We have proposed a rotation angle sensor with a substrate arranged so that

[0006]

However, in the above rotation angle sensor, it is necessary to form a gap in the axial direction of the shaft between the substrate and the permanent magnet, so when applied to a throttle position sensor, , the overall dimension in the axial direction increases by this gap, although it is small. Furthermore, during assembly, it is necessary to set the gap between the permanent magnet and the circuit board to be less than the thickness of the magnetic sensor, and the allowable axial displacement of the shaft is smaller than this gap. Therefore,
Although the above-mentioned rotation angle sensor is much easier to manufacture than the device described in Japanese Patent Application Laid-Open No. 62-237302, it is still difficult to make adjustments when assembling the shaft.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a non-contact type throttle position sensor that is easy to manufacture and that can ensure stable detection accuracy without being affected by normal axial displacement of a shaft. With the goal.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the throttle position sensor of the present invention includes a through hole formed in a substrate and a magnetoresistive element attached to the plate surface around the through hole. a detection element, a housing that accommodates the detection element and supports it in a predetermined position, a shaft that is disposed so that its axial tip passes through the through hole of the substrate and is rotatably supported by the housing; A magnet member provided at a position intersecting the substrate at the axial end of the shaft, the magnet member having an axial length corresponding to the thickness of the magnetoresistive element plus at least a predetermined permissible axial displacement of the shaft. A magnet member having an axial length is provided.

[0009]

[Operation] In the throttle position sensor configured as described above, when the shaft rotates in conjunction with the throttle valve, the magnet member rotates relative to the detection element. According to this relative rotation, the magnetic field of the parallel magnetic flux containing the magnetoresistive element of the detection element changes, so
The resistance value changes in accordance with the change in the magnetic field, and a signal corresponding to the rotation of the shaft is output from the detection element.

[0010] In this case, the shaft is arranged to pass through the through hole of the substrate of the detection element, and the magnet member having the predetermined axial length is provided at the axial end of the shaft at a position intersecting the substrate. Therefore, the magnet member does not deviate from the substrate surface under normal axial displacement with respect to the shaft. Therefore, the detection element is always placed in a uniform magnetic field, ensuring stable detection accuracy.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a throttle position sensor 1 according to an embodiment of the present invention, which is mounted on a throttle body (not shown) and supported so that a shaft 2 rotates in conjunction with the throttle shaft (not shown). That is,
The throttle position sensor 1 is located between two adjacent recesses 3.
A shaft 2 is rotatably supported via a bearing 4 on a partition wall 3c between these recesses 3a and 3b.

A lever 5 housed in one recess 3a of the housing 3 is fixed to one end of the shaft 2.
The lever 5 is connected to a throttle shaft (not shown). A return spring 6 is interposed between the housing 3 and the lever 5, and the lever 5 is urged toward a predetermined initial position. Therefore, when a throttle valve (not shown) is opened, the lever 5 that is interlocked with the throttle shaft is driven against the biasing force of the return spring 6, and the shaft 2 is rotated. Note that although a sintered oil-impregnated bearing is used as the bearing 4 in this embodiment, it goes without saying that a ball bearing or the like may also be used.

A detection element 10 is disposed within the recess 3b of the housing 3 so as to surround the shaft 2. That is, the detection element 10 has a rectangular substrate 11 with a through hole 11a formed approximately in the center, and the housing 3 is attached so that the axial tip 2a of the shaft 2 passes through the through hole 11a.
is supported by Then, the substrate 1 around the through hole 11a
A magnetoresistive element 12 is attached to the surface of one plate.

A plurality of lead members 7 are connected to the ends of the substrate 11. The lead member 7 is embedded within the housing 3, and extends laterally to form a connector 8 integrally with the housing 3. Furthermore, a detection circuit (not shown) for processing the output signal of the detection element 10 is mounted on the substrate 11, but since it is well known, a description thereof will be omitted. still,
The shape of the substrate 11 is not limited to a rectangle, and may be any shape.

The magnetoresistive element 12 is formed of a ferromagnetic magnetoresistive element, and has four elements 12a and 12b as shown in FIG.
, 12c and 12d. As shown in FIG. 3, a constant current source CS is connected to the connection point between the element 12a and the element 12d, and the connection point between the element 12b and the element 12c is grounded. At this time, a potential difference generated between the connection point between element 12a and element 12b and the connection point between element 12c and element 12d becomes a detection signal.

A magnet 20, which is a magnetic member according to the present invention, is provided at the axial end portion 2a of the shaft 2, and is housed in the other recess 3b of the housing 3. The magnet 20 is a columnar permanent magnet with a predetermined axial length a, and is embedded in the axial tip 2a of the shaft 2, and rotates together with the shaft 2. Incidentally, the magnet 20 may be configured such that a part of the axial tip 2a of the shaft 2 is removed in the axial direction and attached to the side surface thereof, or the entire axial tip 2a may be made of a permanent magnet. You can also use it as

The axial length a of the magnet 20 is set to the axial length corresponding to the thickness of the magnetoresistive element 12 plus at least a predetermined allowable axial displacement of the shaft 2. ing. The allowable axial displacement is shaft 2
The value is set to be greater than the axial displacement that can normally occur. For example, if the normal axial displacement of the shaft 2 is 5 mm, the axial length a of the magnet 20 is set to, for example, 10 mm. The relative positional relationship between the shaft 2 and the substrate 11 is set such that the position where the magnet 20 intersects the substrate 11, particularly the substantially central portion in the axial direction of the magnet 20, is located on the attachment surface of the magnetoresistive element 12. There is.

As described above, the detection element 10 and the magnet 20 are housed in the recess 3b of the housing 3.
This recess 3b is sealed with a cover 13 made of synthetic resin via a seal member 9 made of rubber.

According to the throttle position sensor 1 of this embodiment configured as described above, the lever 5 is driven in conjunction with the throttle valve (not shown), and the shaft 2 is moved to the bearing 4.
Rotate inside. According to this rotation of the shaft 2, the resistance value of the magnetoresistive element 12 of the detection element 10 changes. That is, as the shaft 2 rotates, the magnetic field by the magnet 20 also rotates, and the direction of the magnetic field applied to each magnetoresistive element changes, so the resistance value of each of the elements 12a, 12b, 12c, and 12d changes. Accordingly, the connection point between element 12a and element 12b and the connection point between element 12c and element 1 are determined according to the ratio of each resistance value.
The potential difference generated between the connection points 2d changes, and a signal corresponding to the rotation of the shaft 2 is output from the detection element 10.

In the throttle position sensor 1 described above, a magnetic field from a magnet 20 is applied to the magnetoresistive element 12 as shown in FIG. 4, and a parallel magnetic flux is formed over the axial length a. In addition, in FIG. 4, the broken lines indicate equipotential lines. Since the axial length a of the magnet 20 is set to be greater than the normal axial displacement of the shaft 2, even if the shaft 2 undergoes axial displacement within the range of the axial length a, the magnet 20 Always magnetoresistive element 12
The magnetic field applied to the magnetoresistive element 12 does not change due to normal axial displacement of the shaft 2. Therefore, errors in the detected rotation angle can be reduced, and detection accuracy is improved.

[0021] Also, the throttle position sensor 1
During manufacturing, the positional relationship between the substrate 11 and the shaft 2 only needs to be strictly controlled in the direction perpendicular to the shaft 2, and within the axial length a of the magnet 20 with respect to the axial direction of the shaft 2. Since it only needs to be controlled, tolerances can be expanded, resulting in lower defective rates and lower manufacturing costs.

Although a ferromagnetic magnetoresistive element is used as the magnetoresistive element 12 in this embodiment, a semiconductor magnetoresistive element may be used instead.

[0023]

[Effects of the Invention] Since the present invention is constructed as described above, it achieves the following effects. That is, according to the throttle position sensor of the present invention, the magnetoresistive element is always placed in a uniform magnetic field, and the output of the detection element does not change even if the shaft is displaced in the normal axial direction, allowing stable detection. Accuracy can be ensured. Moreover, the shaft can be easily manufactured because it is disposed through the through hole of the substrate and only needs to be assembled to the shaft with a precision that ensures a predetermined allowable axial displacement.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a throttle position sensor according to an embodiment of the present invention.

FIG. 2 is a plan view of a detection element and a shaft in one embodiment of the present invention.

FIG. 3 is a circuit diagram showing a connection state of a ferromagnetic magnetoresistive element in an embodiment of the present invention.

FIG. 4 is a front view showing the relationship between a magnetic field generated by a magnet embedded in a shaft and a detection element in an embodiment of the present invention.

[Explanation of symbols]

2 Shaft 3 Housing 10 Detection element 11 Board 12 Magnetoresistive element 13 Cover 20 Magnet (magnetic member)

Claims (1)

[Claims] 1. A detection element comprising a through hole bored in a substrate and a magnetic resistance element attached to a plate surface around the through hole, a housing for accommodating and supporting the detection element in a predetermined position, and a shaft. A shaft disposed so that a directional tip passes through a through hole of the substrate and rotatably supported by the housing, and a magnet member provided at a position intersecting the substrate at an axial tip of the shaft. , a magnet member having an axial length corresponding to the thickness of the magnetoresistive element plus at least a predetermined permissible axial displacement of the shaft. .