JP2007333496A - Rotational position sensor, and rotational position detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress an error caused by axial positional variation of a rotary shaft, and to reduce the size in the axial direction. <P>SOLUTION: A detection element 13 is arranged in the vicinity in the radial direction of a cam plate 11 wherein a distance (d) from a rotational center O to an edge is changed depending on an angle θ, and a direction orthogonal to the rotary shaft 12 is called a detection direction. Thereby, even when the axial position of the rotary shaft 12 is varied by receiving a thrust load, the direction of the variation is orthogonal to the detection direction, whereby it is hardly affected. Since the need of installing a pair of coils to sandwich the cam plate 11 therebetween is obviated, the axial size can be reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rotational position sensor and a rotational position detection device. More specifically, the present invention relates to a rotational position sensor and a rotational position detection device that can suppress errors due to axial position fluctuations of a rotational shaft and reduce the axial size. About.

Conventionally, a cam plate in which the distance from the rotation center to the peripheral edge changes depending on the angle, a rotating shaft for rotating the cam plate, a pair of coils installed so as to sandwich the cam plate, and an electric power according to the characteristics of the coil A position detector including a detection circuit that outputs a signal is known (for example, see Patent Document 1).
JP 2003-014493 A ([0106] to [0111], FIGS. 16 to 21)

In the above conventional position detector, even if the rotational axis receives a thrust load and the axial position fluctuates, the influence caused by the pair of coils installed so as to sandwich the cam plate is offset. It wasn't supposed to be.
However, since it is necessary to install a pair of coils so as to sandwich the cam plate, there has been a problem that the axial size of the position detector becomes thick.
SUMMARY OF THE INVENTION An object of the present invention is to provide a rotational position sensor and a rotational position detection device that can suppress errors due to axial position fluctuations of a rotating shaft and can reduce the axial size.

In a first aspect, the present invention relates to a cam plate (11) in which a distance (d) from a rotation center (O) to a peripheral edge changes according to an angle (θ), and a rotation shaft (12) passing through the rotation center (O). ) And a detection element (13) which is installed in the vicinity of the cam plate (11) in the radial direction and whose electrical characteristics change according to the distance (g) to the nearest peripheral edge. A rotational position sensor (10) is provided.
In the above configuration, the angle (θ) of a point on the periphery of the cam plate (11) refers to an angle viewed from a predetermined reference point (0 °) on the periphery of the cam plate (11).
In the rotational position sensor (10) according to the first aspect, the detection element (13) is installed in the vicinity of the radial direction of the cam plate (11), and the direction orthogonal to the rotational axis (12) is the detection direction. For this reason, even if the rotating shaft (12) receives a thrust load and the axial position fluctuates, the fluctuation is in a direction perpendicular to the detection direction, and therefore it can be hardly affected. That is, it is possible to suppress an error due to the position variation in the axial direction of the rotating shaft (12). And since it is not necessary to install a pair of coils so that a cam board (11) may be pinched | interposed, the size of an axial direction can be made thin.

In a second aspect, the present invention relates to the rotational position sensor (10) according to the first aspect, wherein the cam plate (11) is a nonmagnetic conductor or a magnetic body, and the detection element (13) is a coil. A rotational position sensor is provided.
In the rotational position sensor (10) according to the second aspect, the inductance of the coil (13) changes according to the distance (g) between the coil (13) and the nearest peripheral edge of the cam plate (11). Can be detected electrically.

In a third aspect, the present invention relates to a rotational position sensor (10) according to the first or second aspect, and a detection circuit that outputs an electrical signal (V) corresponding to the electrical characteristics of the detection element (13). (30) is provided, and a rotational position detection device (100) is provided.
In the rotational position detection device (100) according to the third aspect, an electrical signal (V) corresponding to the rotational position of the rotational shaft (12) can be obtained.

In a fourth aspect, the present invention provides the rotational position detection device (100) according to the third aspect, wherein the rotational position (θ) and the electrical signal (V) are within a predetermined angular range (θs ≦ θ ≦ θe). Provided is a rotational position detecting device (100) characterized in that the cam plate (11) has an outer shape that is linearly related.
In the above configuration, the rotational position (θ) refers to the angle (θ) of the peripheral point of the nearest cam plate (11) when viewed from the detection element (13).
In the rotational position detection device (100) according to the fourth aspect, an electrical signal (V) proportional to the rotational position of the rotational shaft (12) can be obtained.

  According to the rotational position sensor and the rotational position detection device of the present invention, it is possible to suppress an error due to a positional variation in the axial direction of the rotational shaft. In addition, the axial size can be reduced.

  Hereinafter, the present invention will be described in more detail with reference to the embodiments shown in the drawings. Note that the present invention is not limited thereby.

FIG. 1 is an explanatory diagram illustrating a rotational position detection apparatus 100 according to the first embodiment.
The rotational position detection device 100 includes a rotational position sensor 10, a cable 20, and a detection circuit 30.

  The rotational position sensor 10 is installed in the vicinity of the cam plate 11 made of aluminum in which the distance d from the rotational center O to the peripheral edge changes according to the angle θ, the rotational shaft 12 passing through the rotational center O, and the radial direction of the cam plate 11. A solenoid type coil 13 whose inductance changes according to the distance g to the nearest peripheral edge, and a case 14 are provided.

The angle θ at a point on the periphery of the cam plate 11 refers to an angle viewed in the clockwise direction with a reference point set on the periphery of the cam plate 11 being 0 °.
The distance d decreases as it rotates clockwise from θ = 0 °, and increases linearly from an angle slightly rotated around the angle θe to an angle slightly before θ = 0 °.

The cam plate 11 and the rotary shaft 12 are integral, and the cam plate 11 also rotates around the rotation center O when the rotary shaft 12 rotates.
Here, the rotational position of the rotary shaft 12 refers to the angle θ of the peripheral point of the cam plate 11 closest to the coil 13.
Then, the distance g is the smallest when the rotation position is θ = 0 °, and increases as the rotation position increases from θ = 0 °, and a little θ = 0 ° from the angle at which the rotation position slightly turns θ = θe. It decreases linearly between before and after.

  As shown in FIG. 2, the thickness of the cam plate 11 is larger than the diameter of the coil 13. The difference between the two is larger than the position variation range in the axial direction of the rotating shaft 12. For this reason, even if the rotating shaft 12 fluctuates in the axial direction, the inductance of the coil 13 does not change. On the other hand, when the rotating shaft 12 rotates and the distance g changes, the inductance of the coil 13 also changes. Specifically, the smaller the distance g, the smaller the inductance of the coil 13.

  Returning to FIG. 1, the detection circuit 30 has a configuration known from Japanese Patent Application Laid-Open No. 2003-014493, and includes a resistor 31 in series with the coil 13, a capacitor 32 charged and discharged via the resistor 31, and a capacitor 32. An inverted output comparator 33 for supplying the output voltage S2 to the coil 13 with the voltage as the input voltage S1 and a rectangular wave having a fixed time width as a trigger triggered by both the rising edge and the falling edge of the output voltage S2 of the comparator 33 The circuit includes a shot circuit 34 and a smoothing circuit 35 that outputs a voltage V corresponding to the frequency of the rectangular wave output from the one-shot circuit 34.

  The comparator 33 outputs a high level up to the rising threshold value VthH when the input voltage S1 rises from a low voltage, and outputs a low level when the input voltage S1 rises above the rising threshold value VthH. When the input voltage drops from the high voltage side, a low level is output until the falling threshold value VthL, and when the input voltage falls below the falling threshold value VthL, a high level is output.

  Therefore, as the distance g decreases, the inductance of the coil 13 decreases, the frequency of the output voltage S2 of the comparator 33 increases, and the output voltage V of the smoothing circuit 35 increases.

FIG. 3 is a characteristic diagram showing the relationship between the rotational position θ of the rotary shaft 12 and the output voltage V of the detection circuit 30.
In a predetermined angle range (θs ≦ θ ≦ θe), the rotational position θ and the output voltage V are in a linear relationship.
The relationship between the rotational position θ and the output voltage V depends on the function d = f (θ) of the distance d with respect to the angle θ. Here, the function d = f (θ) means the outer shape of the cam plate 11. That is, by adjusting the outer shape of the cam plate 11, the relationship between the rotational position θ and the output voltage V can be set to a desired relationship regardless of the non-linear characteristics of the detection circuit 30. Here, the outer shape of the cam plate 11 is adjusted so as to have a linear relationship.

  According to the rotational position detection device 100 according to the first embodiment, it is possible to suppress an error due to a positional variation in the axial direction of the rotation shaft 12. Moreover, since it is not necessary to install a pair of coils so as to sandwich the cam plate 11, the size in the axial direction can be reduced. Furthermore, since the rotational position sensor 10 has high heat resistance, the rotational position can be suitably detected even at high temperatures.

  The cam plate 11 may be made of a magnetic material.

  A circuit disclosed in Japanese Patent Application Laid-Open No. 2004-69415 may be used as the detection circuit 30.

  The rotational position sensor and rotational position detection device of the present invention can be used to detect the rotation of the shaft of a gasoline engine.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration explanatory diagram illustrating a rotational position detection device according to a first embodiment. 1 is a longitudinal sectional view showing a rotational position sensor according to Embodiment 1. FIG. It is a characteristic view showing the relationship between the rotational position θ of the rotating shaft and the output voltage V of the detection circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Rotation position sensor 11 Cam board 12 Rotating shaft 13 Coil 30 Detection circuit 100 Rotation position detection apparatus

Claims (4)

The cam plate (11) in which the distance (d) from the rotation center (O) to the periphery changes according to the angle (θ), the rotation shaft (12) passing through the rotation center (O), and the cam plate (11). A rotational position sensor (10) comprising a detection element (13) installed in the vicinity in the radial direction and having an electrical characteristic that changes in accordance with a distance (g) to the nearest peripheral edge. The rotational position sensor (10) according to claim 1, wherein the cam plate (11) is a non-magnetic conductor or a magnetic body, and the detection element (13) is a coil. The rotational position sensor (10) according to claim 1 or 2, and a detection circuit (30) for outputting an electric signal (V) corresponding to an electric characteristic of the detection element (13). A rotational position detecting device (100) characterized. The rotational position detection device (100) according to claim 3, wherein the outer shape is such that the rotational position (θ) and the electrical signal (V) are linearly related within a predetermined angular range (θs ≦ θ ≦ θe). A rotational position detecting device (100) characterized in that the cam plate (11) has.

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