JPH10325719A - Sensor for inclination and acceleration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect both an acceleration and an inclination with good accuracy by using one sensor, by a method wherein the movement direction of a permanent magnet is regulated to one direction by using a leaf spring. SOLUTION: A support base 5 is attached to the frame of an object to be detected such as a motorized bicycle, a motorized wheelchair or the like, in such a way that a leaf spring 6 becomes vertical. When the object to be detected is tilted forward or backward by an angle θ, also the support base 5 is tilted, the leaf spring 6 is deformed, and the position of a permanent magnet 9 is displaced with reference to a magnetoresistance element 11. It is assumed that, when the object to be detected is in a horizontal state, a constant output is generated. Then, an output voltage is decreased when the permanent magnet 9 is displaced to the front direction as shown in Fig. 2b, and when the permanent magnet 9 is displaced to the rear directions shown in Fig. 2c, the output voltage is increased. When an acceleration exists in the movement direction of the object to be detected, the permanent magnet 9 is moved to a direction opposite to a direction in which the acceleration acts. As a result, the acceleration can be detected in the same manner as a case in which the object to be detected is tilted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tilt / acceleration sensor suitable for use in an electric bicycle, an electric wheelchair, and the like.

[0002]

2. Description of the Related Art Conventionally, as a tilt detection switch for detecting a tilt, an acceleration sensor for detecting an acceleration, etc., a tilt detection switch for electrically detecting an angle using the flowability of mercury, and a sensor for detecting vibration due to an earthquake or the like. However, there are seismic devices that electrically open and close circuits at a predetermined acceleration. However, although there is a means for individually detecting the inclination or the acceleration, there is no sensor capable of detecting both the inclination and the acceleration.

There are many types of dedicated acceleration sensors, such as a pendulum-type or vibration-type inertial acceleration sensor and a servo-type acceleration sensor. FIG. 7 shows an example of a pendulum type sensor. The pendulum 1 is supported at its upper end by a pivot bearing 2 having low friction, and is magnetically coupled to a differential transformer 3. An output circuit 4 is connected to the differential transformer 3 so that an output is taken out. Therefore, when an acceleration a in the direction of the arrow of the pendulum 1 is applied, the pendulum 1 is displaced in the opposite direction, and this displacement is detected by the differential transformer 3.

[0004]

As described above, there are various means for detecting either the inclination or the acceleration. However, detection of both the inclination and the acceleration is not performed at the same time. However, in an electric bicycle, an electric wheelchair, and the like, acceleration is required for drive control, and it is necessary to simultaneously detect the degree of inclination on a slope.

In an electric bicycle or an electric wheelchair, the detection range that needs to be detected as acceleration is ± (0.1).
-10) G is relatively small, and the slope angle of the slope to be detected is about ± (0-10) degrees. In the present invention, both the acceleration and the slope in such a range are determined. It is an object of the present invention to provide a tilt / acceleration sensor that can be detected by one sensor as accurately as possible.

[0006]

According to the first aspect of the present invention,
A leaf spring having a predetermined width with its upper end fixed is provided vertically, and a permanent magnet is attached to the lower end of the leaf spring so that a magnetized surface is in a direction orthogonal to the leaf spring. A detecting means for detecting a change in the magnetic field at one point near the surface is provided. Therefore, the moving direction of the permanent magnet is regulated in one direction by the leaf spring, and it is possible to efficiently detect only the acceleration in the front-rear direction necessary for the forward or backward drive control of the electric bicycle or the electric wheelchair, Since the detecting means detects a change in the magnetic field,
It is possible to detect not only a dynamic physical quantity such as acceleration but also a static physical quantity such as inclination.

According to a second aspect of the present invention, the detecting means is formed by a magnetoresistive element disposed opposite to the magnetized surface of the permanent magnet, and the right and left of the detecting means are perpendicular to the magnetized surface by the magnetoresistive element. A magnetic field heading in a direction different by 45 ° is detected, and the difference between the detected values is taken out as an output. Therefore, since there is no friction portion, there is no hysteresis, and a small inclination and a weak acceleration can be detected with high accuracy.

According to a third aspect of the present invention, the permanent magnet is formed in a shape that is long in the moving direction. Therefore, the mass of the magnet can be minimized, and an output with good linearity can be obtained.

According to a fourth aspect of the present invention, the effective swing width of the permanent magnet is set to not more than 1/2 of the length in the moving direction.
Therefore, even if it receives a shock or a large acceleration, there is no damage, and the attenuation of the vibration output can be accelerated.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. First, the upper end of the leaf spring 6 is fixed to the support base 5. The leaf spring 6 has a large width dimension and a thickness of 0.05.
It is about 0.5 mm. A magnet holding base 7 serving as a weight is fixed to the lower end of such a leaf spring 6. A concave portion 8 opening to the near side of the magnet holding base 7
Inside, a permanent magnet 9 having a rectangular parallelepiped shape long in the bending direction of the leaf spring 6, that is, a shape long in the moving direction is attached. The magnetized surface of the permanent magnet 9 is in the front-rear direction (FIG. 1).
Are located in the left-right direction, and in FIG. 2 in the front-back direction). Next, the support table 5 has a PC
The upper end of the plate 10 is fixed. A magnetoresistive element 11 as a detecting means is attached to the PC board 10 at a position close to and opposed to the permanent magnet 9. As shown in FIG. 3, the magneto-resistive element 11 includes four variable resistance portions 12 that are bridge-coupled to each other. The output voltage is generated at the terminal based on the output voltage. More specifically, the variable resistance section 12 detects the magnetic field H in the direction of 45 ° left and right with respect to the magnetic field H, and the difference between these two outputs appears as an output.

Next, the support base 5 is attached to a cover 13 having a magnetic shielding function. The cover 13 includes the leaf spring 6, the permanent magnet 9, and the P
The outer periphery of the C plate 10 is covered. Further, at a position facing both ends of the cover 13 in the moving direction of the permanent magnet 9,
The effective swing width of the permanent magnet 9 is set to 1 / length of the length of the permanent magnet 9.
A stopper 14 is fixed as a buffer restricting means for restricting the pressure to 2 or less.

In such a configuration, the support base 5 is mounted so that the leaf spring 6 is perpendicular to the frame of the detected object such as an electric bicycle or an electric wheelchair. FIG. 2A shows a state in which the detected object is horizontal, but if the detected object is tilted forward or backward by an angle θ, the state shown in FIG. 2B or FIG. Thus, the support table 5 is also inclined, the leaf spring 6 is deformed, and the position of the permanent magnet 9 is displaced with respect to the magnetoresistive element 11. The magnetized surface of the permanent magnet 9 is located such that the N pole faces the magnetoresistive element 11 as shown in FIG. FIG. 4 does not show the magnetoresistive element 11 itself, but shows a state in which the permanent magnet 9 has moved by m from the reference position O, and the magnetoresistive element 11 differs from the reference position O by 45 °. Detect the strength of the magnetic field in the direction. That is, assuming that when the permanent magnet 9 is located at the reference position O, each of the variable resistance portions 12 of the magnetoresistive element 11 in directions different by 45 ° detects the magnetic field H, the state shown in FIG. The permanent magnet 9 is m
In this case, one of the values detected by the variable resistance unit 12 is Hcos θ, and the other is Hsin θ. Therefore, the output from the circuit shown in FIG. 3 is an output corresponding to the difference between the two, that is, H × (cos θ−
(sin θ). Therefore, assuming that a constant output is generated when the object to be detected is horizontal as shown in FIG. 2A, the output voltage is generated when the permanent magnet 9 is displaced in the forward direction as shown in FIG. Decreases, and the output voltage increases when the permanent magnet 9 is displaced backward as shown in FIG. 2C.

Although FIG. 2 has been described assuming that the object to be detected is inclined, if the motion of the object to be detected includes acceleration, the permanent magnet 9 moves in the direction opposite to the direction in which the acceleration acts. Therefore, the acceleration can be detected in exactly the same manner as when the object to be detected is tilted.

The shape of the permanent magnet 9 may be long as long as it is long in the moving direction, and may be formed in a disk-like circle when viewed from above. Now, let the diameter of the permanent magnet 9 be 4d.
FIG. 5 shows the distribution state of the magnetic flux density at the observation point when the distance between the permanent magnet 9 and the magnetoresistive element 11 changes to d, 1.5d, and 2d. FIG. 6 shows a state of an output change when the permanent magnet 9 having such a magnetic flux density distribution moves. That is, in FIG. 6, the horizontal axis indicates the moving distance of the permanent magnet 9 having a diameter of 4d, and the vertical axis indicates the output at that time. Therefore, when the amount of movement is small, the relationship between the amount of movement and the output shows linearity. However, when the amount of movement increases, the value of the detection output decreases, and the linearity disappears. In the state shown in FIG.
The distance between the permanent magnet 9 and the magnetoresistive element 11 is d, 1.5
In any case, even if it changes to d, 2d, and three types, the linearity is shown within the range of the movement amount up to about 1/2 of the diameter.

In practice, however, the amount of deflection of the permanent magnet 9 is defined by the stopper 14 so as to be equal to or less than 1/2 of its length. The necessity of the regulation in this way is mainly because the effect of accelerating the damping of the vibration of the permanent magnet 9 when receiving a strong impact or acceleration is obtained, and the output of the magnetoresistive element 11 is made linear. This is because of the second reason.

First, the first reason is as follows.
Is small, the amount of deformation of the leaf spring 6 is inevitably reduced, so that no excessive force acts on the movable part, and the vibration is rapidly damped. Therefore, the structural strength is also high. Next, the second reason is as described above with reference to FIG. 6, as described above.

[0017]

According to the first aspect of the present invention, a leaf spring having a predetermined width and a fixed upper end is provided vertically, and a magnetized surface is positioned at the lower end of the leaf spring in a direction perpendicular to the leaf spring. A permanent magnet to be mounted is provided, and a detecting means for detecting a change in a magnetic field at one point near the magnetized surface of the permanent magnet is provided. It is possible to efficiently detect only the acceleration in the front-rear direction necessary for the drive control of the forward or backward movement of a bicycle or an electric wheelchair, and the detection means detects a change in the magnetic field. This has the effect that not only physical physical quantities but also static physical quantities such as inclinations can be detected at the same time.

According to a second aspect of the present invention, the detecting means is formed by a magneto-resistive element disposed opposite to the magnetized surface of the permanent magnet, and the magneto-resistive element is used to control the right and left with respect to the perpendicular of the magnetized surface. Since the magnetic field heading in a direction different by 45 ° is detected and the difference between the detected values is taken out as an output, there is no hysteresis because there is no friction portion, and it is possible to accurately detect a small inclination and a weak acceleration. It has the following effects.

According to the third aspect of the present invention, since the permanent magnet is formed to have a long shape in the moving direction, the effect of minimizing the mass of the magnet and obtaining an output with good linearity can be obtained. Have.

According to the fourth aspect of the present invention, the effective swing width of the permanent magnet is set to not more than の of the length in the moving direction, so that the permanent magnet is not damaged even when subjected to a shock or a large acceleration, and the vibration output is damped. This has the effect that it is also possible to accelerate the process.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view showing an embodiment of the present invention.

FIG. 2 shows a state where the PC board is removed.
(a) is a front view when the detected object is in a horizontal state, (b)
FIG. 4 is a front view of a state where the detected object is tilted forward, and FIG. 4C is a front view of a state where the detected object is tilted backward.

FIG. 3 is a circuit diagram equivalently showing a configuration of a magnetoresistive element.

FIG. 4 is an explanatory diagram showing a state of magnetic flux detected in directions different by 45 ° when a permanent magnet moves.

FIG. 5 is a view showing a distribution state of a magnetic flux of a permanent magnet.
Is an explanatory diagram when the distance between the permanent magnet and the magnetoresistive element is d. FIG.
(C) is an explanatory diagram when the distance between the permanent magnet and the magnetoresistive element is 2d.

FIG. 6 is a graph showing a relationship between a movement of a permanent magnet and a detection output.

FIG. 7 is a principle diagram showing an example of a conventional acceleration sensor.

[Explanation of symbols]

 6 leaf spring 9 permanent magnet 11 magnetoresistive element

Claims (4)

[Claims] 1. A leaf spring having a predetermined width fixed to an upper end is provided vertically, and a permanent magnet is attached to a lower end of the leaf spring such that a magnetized surface is in a direction orthogonal to the leaf spring. A tilt / acceleration sensor characterized by comprising a detecting means for detecting a change in a magnetic field at one point near the magnetized surface of a magnet. 2. The detecting means is formed by a magnetoresistive element disposed opposite to a magnetized surface of a permanent magnet, and the magnetoresistive element causes a direction different by 45 ° left and right with respect to a perpendicular to the magnetized surface. 2. The tilt / acceleration sensor according to claim 1, wherein a magnetic field heading toward the sensor is detected, and a difference between the detected values is taken out as an output. 3. The tilt / acceleration sensor according to claim 1, wherein the permanent magnet is formed in a shape that is long in the moving direction. 4. The tilt / acceleration sensor according to claim 1, wherein the effective swing width of the permanent magnet is set to be not more than の of the length in the moving direction.