JPH0415518A - Movement detecting device - Google Patents

Abstract

PURPOSE:To decrease the variation of an output level caused by a variation of a moving speed of a detection body to be moved by providing an E-shaped yoke consisting of a first yoke and a second yoke constituted of a magnetic permeable material on a detector. CONSTITUTION:A detector 8is provided with a magnet 9having width of one period of projecting and recessing of a tooth part 2 in a gear 3, and magneto- resistance elements 10, 11 (first MR, second MR). Also, this magnet 9 and a first MR 10 and a second MR 11 are installed at an interval of half of one period of projecting and recessing of the tooth part 2, and both of them are coupled magnetically by a first yoke 12 and a second yoke 13 of a U-shape. That is, width (a) of the yokes 12, 13, an interval (b) of the magnet 9 and the yokes 12, 13, and width (c) of the magnet 9 are set as shown in the expression, respectively. In such a way, by providing two yokes 12, 13, the greater part of a magnetic flux generated from the magnet 9 can be bypassed forcibly to the yoke of one side in two yokes 12, 13, therefore, a leakage magnetic flux itself can be decreased extremely.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a device for detecting the movement of a moving object in a non-contact manner, and more particularly to a movement detecting device that utilizes magnetic action.

2. Description of the Related Art In recent years, movement detection devices have been used in automobiles as devices for detecting the rotational state of wheels with high precision, and in particular, those using magnetism have been used due to the environment in which they are used.

A conventional movement detection device will be explained below.

FIG. 6 is a side view showing a conventional movement detection device that detects rotation of wheels. In FIG. 6, a gear 3 made of a magnetically permeable member and having a large number of teeth 2 evenly distributed around its outer periphery is fixed to the rotating shaft 1 of the wheel, and rotates integrally with the wheel. ing. Further, in a portion of the gear 3 close to the tooth portion 2, a detector 4 is provided which is fixed to the vehicle body and detects magnetic changes. The detector 4 has a structure in which a magnet 6 is provided at one end of a U-shaped yoke 5 having a spacing that matches the bits of the teeth 2, and a coil 7 is wound around the center of the yoke 5. ing.

The operation of the movement detection device configured as described above will be described below. First, when the gear 3 rotates together with the axle 1, the teeth 2 provided on the outer periphery of the gear 3 sequentially pass through portions close to the detector 4. Here, as shown in FIG. 6, when both end surfaces of the yoke 5 in the detector 4 are opposed to the toothed portion 2, the magnetic flux generated from the magnet 6 is transmitted from the tip of the yoke 5 to the toothed portion 2, The water flows through the yoke 5 through the main body portion of the yoke 5 and the root of the toothed portion 2 facing the magnet 6. In this way, both ends of the yoke 5 are connected to the teeth 2.
In the state where the gear 3 faces the detector 5, the distance between the teeth 2 of the gear 3 and the detector 5 becomes minimum, and the magnetic resistance of this part becomes low, so the magnetic flux passing through the inside of the yoke 5 becomes maximum. .

Next, when the gear 3 rotates further and both ends of the yoke 5 on the detector 4 are located between the teeth 2, the distance between the yoke 5 and the teeth 2 increases, so the magnet 6 Most of the magnetic flux generated from the U-shaped yoke 5
It will flow through the space of the concave part. As a result, the magnetic resistance in the magnetic path increases significantly compared to the state shown in FIG. 6 in which both ends of the yoke 5 face the teeth 2, so that Magnetic flux decreases.

In this manner, when the gear 3 rotates, the amount of magnetic flux flowing inside the yoke 5 changes from the maximum to the minimum for each half pitch of the tooth portion 2. Since a coil 7 is wound around the center of the yoke 5, changes in magnetic flux within the coke 5 caused by the rotation of the gear 3 are extracted as an electrical signal.

Problems to be Solved by the Invention However, in the above configuration, the electric signal (2) taken out from the coil 7 is expressed as V = dφ/based on magnetic flux φ and time.
Since it is a signal expressed as dt, it becomes a signal that changes in level depending on the rate of change in magnetic flux. As a result,
When the rotational speed of the wheel serving as a non-moving detection object decreases, the signal level taken out from the coil 7 also decreases accordingly, making it impossible to obtain a detection signal in a very low-speed moving state or a stationary state. In addition, in the above configuration, even when both ends of the yoke 5 are located between the teeth 2, most of the leakage magnetic flux flows through the recessed part of the yoke 5. It is not possible to increase the range of change in magnetic flux. Furthermore, due to the leakage magnetic flux mentioned above, it is not possible to provide a sufficient distance between the detector 4 and the teeth 2, and as a result, there is less margin for installation, making assembly and adjustment work difficult. .

Furthermore, the above configuration has various problems such as a possibility of malfunction if magnetically permeable substances such as metal dust enter the open portion of the gear and the detector.

The present invention solves the problems of the prior art, and has a small change in the output level due to changes in the moving speed of the moving detected object, a wide change range of the output signal (and a large gap between the gear and the detector). It is an object of the present invention to provide a movement detection device that can widen the area and further prevent foreign matter from entering the recess of the gear and detector.

Means for Solving the Problems In order to achieve the above object, a movement amount detection device according to the present invention includes a gear having teeth arranged at equal intervals and made of a magnetically permeable material, and a gear disposed close to the teeth. one of the gear and the detector is fixed to a fixed side and the other is fixed to a moving detection side, and the detector includes a first yoke made of a magnetically permeable material and a first yoke made of a magnetically permeable material. It is composed of an E-shaped yoke consisting of a second yoke, a magnet placed in the center of this yoke, and a magnetoresistive element placed at the tip of the yoke, and the width a of the magnetoresistive element is the same as that of the magnet. The distance b between the magnetoresistive element and the width C of the magnet are approximately a −T /
2, b = T / 2 X n 1, to = “pXn
2 (n+, n4.: natural number, T: one period of the unevenness of the tooth portion). In addition, the concave and convex portions of the gear and detector are filled with a material with low magnetic permeability.

In the movement detection device configured as described above, when both the magnet and the first magnetoresistive element face the teeth, the other second magnetoresistive element moves between the teeth. It will be located in between. As a result, the magnetic flux generated from the magnet can be bypassed toward the first magnetoresistive element, and when the first magnetoresistive element is moved half a pitch and is positioned between the teeth, the magnet Since both the second magnetoresistive element and the second magnetoresistive element are in a state opposite to the teeth, the magnetic flux generated from the magnet can be bypassed toward the second magnetoresistive element. Therefore, there is little change in the output level due to changes in the moving speed of the moving detected object (
, the variation range of the output signal becomes wider.

Moreover, the signals of the first magnetoresistive element and the second magnetoresistive element obtained by this configuration have a phase difference of 180 degrees, and the signals of the first magnetoresistive element and the second magnetoresistive element have a phase difference of 180 degrees. By assembling the second magnetoresistive element in a bridge shape, a signal with twice the amplitude can be obtained.

Furthermore, with this configuration, the area on the detector side in contact with the teeth is always constant, so the magnetic resistance in the magnetic path is kept constant, and leakage magnetic flux can be minimized.

Furthermore, since the gear teeth and the recessed portion of the detector are filled with a material with low magnetic permeability, the entry of foreign substances that have a negative mechanical and magnetic effect on the gear teeth and the recessed portion of the detector is prevented. It can be prevented.

Embodiment Below, a movement detection device according to an embodiment of the present invention is shown in Figs.
This will be explained using the drawing of FIG.

FIG. 1 is a side view showing an embodiment of the movement detecting device according to the present invention, and for ease of explanation, the gear 3 will be explained as being stretched flat and moved in a straight line. In the figure, reference numeral 8 denotes a detector, which includes a magnet 9 having a width equal to one cycle of the unevenness of the teeth 2 in the gear 3, and a magnetoresistive element 1.
0.11 (hereinafter referred to as first MR 102MR). Then, this magnet 9 and the first
MR101 The second MR11 is installed at an interval of half of one period of the unevenness of the tooth portion 2, and is connected to the U-shaped first yoke 1.
2 and the second yoke 13 magnetically couple them. That is, as shown in FIG. Width a1 of the second yoke 12.13 and the width a1 of the magnet 9 and the first yoke 12. The distance from the second yoke 12.13 and the width C of the magnet 9 are a = T/2, b = T/2Xn+, respectively.
, c=TXnz (n+, ng: natural number, T: width of one period of the unevenness of the tooth portion 2).

In the movement detection sensor configured as described above, in the state shown in FIG. 1 in which the magnet 9 and the first MRIO face the teeth 2 of the gear 3, the distance between the magnet 9 and the first MRIO and each tooth 2 is as follows. narrow,
Since the magnetic path resistance in this portion is significantly reduced, the magnet 9 is placed in the closed magnetic path portion consisting of the magnet 9, the first yoke 12, the tooth portion 2 of the first MR101, the base of the gear 3, the tooth portion 2, and the magnet 9. Most of the magnetic flux generated from this will flow as magnetic flux φ. Further, the second MR is located between the teeth 2 and has a magnet 9 between them.
Also, the space is sufficiently wider than the space between the first MRIO and the tooth portion 2, resulting in high magnetic path resistance.

However, as mentioned above, the magnetic flux generated from the magnet 9 is also the magnetic flux φ shown by the dotted line in the sufficiently expanded space.
It will leak and flow as 2. However, since the relationship between the magnetic flux φ1 and the magnetic flux φ2 in this case is φ=>>φ2, the first MR 10 can be sufficiently moved to the saturation region, and the resistance change of the first MRIO becomes maximum accordingly. The resistance change of the second MR 11 is minute.

Next, when the gear 3 fixed to the moving detected object moves in the direction of the arrow by half a pinch of the toothed portion 2, the relationship between the toothed portion 2 and the detector 8 changes. The result is as shown in FIG. Specifically, in FIG. 2, the magnet 9 and the second MRII face the toothed portion 2, resulting in a phenomenon completely opposite to the above-mentioned phenomenon. In this case, the relationship between the magnetic flux φ and the magnetic flux φ2 is φ1<<φ2, so the resistance change of the second MR12 is minute, and the second M
The resistance change of RII becomes maximum.

In this way, by providing two yokes no matter the positional relationship between the gear 3 and the detector 8, most of the magnetic flux generated from the magnet 9 can be forced to one side of the two yokes. Since the magnetic flux can be bypassed to the yoke, the leakage magnetic flux itself can be extremely reduced. Also the 1st M
The variation range of the magnetic flux φ6 and the magnetic flux φ2 flowing through the RIO1 second MRII becomes wider, and accordingly, the amplitude of the signal obtained from each magnetoresistive element (MR) is greatly expanded. In addition, the first MRIO1 and the second MRIO
By assembling 12 in a bridge shape, an operating output is obtained and a signal with twice the amplitude can be obtained.

The magnetoresistive element used here has elements arranged as shown in FIG. Also, the fact that a large signal amplitude can be obtained means that the gap between the teeth 2 of the gear 3 and the detector 8 can be increased, which in turn leads to easier assembly and adjustment. Become.

In addition, as a magnetic flux detection element, the first MRIO1 and the second MRIO1
When using an element that can output a signal according to the strength of magnetic flux, such as I, unlike the conventional case where a signal output according to changes in magnetic flux is output, gear 3 and detector (related to the relative speed with the The amount of movement and speed of a moving object can be accurately detected over a speed range.

Furthermore, in the tooth part 2 of the gear 3 and the recessed part of the detector 8,
There is a possibility that the teeth 2 of the gear 3 and the detector 8 may be damaged due to the intrusion of metal dust or other dust, and the magnetic path may be disturbed by magnetically permeable substances such as metal dust, so to prevent these. In addition, if the tooth portion 2 of the gear 3 and the concave portion of the detector 8 are filled with a material with low magnetic permeability and made flat as shown in FIG. It has the effect of preventing foreign matter from entering the concave portion, which would have a negative mechanical and magnetic effect.

In the above embodiment, only the case where the gear is moved linearly has been described, but it goes without saying that the rotational movement of the rotating body can be detected by forming the gear into a ring shape. Further, in the above embodiment, the case where the detector is fixed and the gear is moved has been described, but the present invention is not limited to this, and any method may be used as long as the relative movement between the two is detected. It may be a configuration.

Effects of the Invention As described above, according to the present invention, the magnetic flux generated by the magnet when the magnetic resistance element on one side is located between the teeth of the gear is forcibly shunted by the yoke on the opposite side. Since the current is blocked from flowing to the magnetoresistive element, the amplitude range of the detection signal obtained from the magnetoresistive element is increased, and by combining two magnetoresistive elements in a bridge shape, the amplitude range is doubled. An amplitude signal is obtained.

Increasing the amplitude of this detection signal increases the spacing margin between the gear and the detector, which simplifies assembly and adjustment work. In addition, by using an element such as a magnetoresistive element that can extract a signal according to the strength of magnetic flux as a magnetic flux detection element, a detection signal with a nearly constant amplitude can be obtained regardless of the moving speed. Accompanying this, accurate movement detection can be performed, and since the gear teeth and the recessed part of the detector are filled with a material with low magnetic permeability, there is no mechanical impact on the gear teeth and the recessed part of the detector. It also has various excellent effects, such as being able to prevent foreign matter from entering without having any negative magnetic effect.

[Brief explanation of drawings]

FIG. 1 is a side view showing an embodiment of the movement detection device according to the present invention, FIG. 3 is a side view showing the movement detection device shown in FIG. 1 moved by T/2, FIG. 4 is an explanatory diagram of dimensions of essential parts of the movement detection device according to the present invention, and FIG. 5 is a diagram showing the magnetic field used in the present invention. FIG. 6 is a plan view showing a pattern of resistive elements, and a side view showing a conventional movement detection device. 2...Tooth section, 3...Gear, 8...
...Detector, 9...Magnet, 10...
...1st MR111...2nd MR, 12...
...First yoke, 13...Second yoke. Name of agent: Patent attorney Shigetaka Awano (1 figure)

Claims (2)

[Claims] (1) Consisting of a gear having teeth arranged at equal intervals and made of a magnetically permeable material, and a detector placed close to the teeth, one of the gear and the detector is placed on the fixed side. and the other is fixed to the moving detection side, and the detector includes an E-shaped yoke consisting of a first yoke and a second yoke made of a magnetically permeable material, and an E-shaped yoke arranged at the center of this yoke. It is composed of a magnet and first and second magnetoresistive elements arranged at the tip of the yoke, and has a width a of the magnetoresistive element, a distance b between the magnet and the magnetoresistive element, and a width of the magnetoresistive element. The width c is approximately a=T/2, b=T/2×n_1, c=T×n, respectively.
_2 (n_1, n_2: natural numbers, T: one period of the unevenness of the tooth portion). (2) The movement detection device according to claim 1, wherein the concave portions of the gear and the detector are filled with a material having low magnetic permeability.