WO2005088318A1

WO2005088318A1 - Acceleration sensor and tire information transmitting device with acceleration sensor

Info

Publication number: WO2005088318A1
Application number: PCT/JP2005/004317
Authority: WO
Inventors: Toshio Ohmori; Yasuo Shimizu; Hideki Nihei
Original assignee: Citizen Watch Co., Ltd.; Citizen Miyota Co., Ltd.; Yokohama Rubber Co., Ltd.
Priority date: 2004-03-15
Filing date: 2005-03-11
Publication date: 2005-09-22
Also published as: JPWO2005088318A1

Abstract

Acceleration produced in a tire can be detected even if a small force of the extent occurring when a tire installed on a vehicle is stolen is applied to the tire. An acceleration sensor (1) is constituted of a sheet spring (5) that is installed in the lower section of an outer case (4), a magnet (6) and a weight (7) that are held at a holding section of the sheet spring (5), and magnetism-electricity converting means (8) that is installed in the upper part of the outer case (4). The holding section, holding the magnet (6), of the sheet spring (5) is formed as an arm section with an open end, and the sheet spring (5) is held by the magnet (6) and the weight (7) by clasping the open end of the sheet spring (5) by the magnet (6) and the weight (7).

Description

Specification

Acceleration sensor and tire information transmission device with acceleration sensor

Technical field

The present invention relates to an acceleration sensor and a tire information transmitting device with an acceleration sensor, and when a tire attached to a car is subjected to a force that is stolen, the applied force is applied to the tire. The present invention relates to an acceleration sensor capable of measuring generated acceleration and a tire information transmitting device with an acceleration sensor.

Background art

[0002] In general, electronic components can be used for new applications due to their miniaturization and weight reduction, and by adding supplementary new functions to existing electronic components. In some cases, it can be used for new applications.

This also applies to an acceleration sensor using magnetoelectric conversion means. For example, an acceleration sensor is used in a tire condition monitoring device that is attached to a tire wheel of an automobile and detects a physical quantity (for example, air pressure) in a running tire. There are new uses when used.

[0003] The tire condition monitoring device is a technology disclosed in Japanese Patent Application Laid-Open Nos. 2000-203218 and 2000-203129, and includes, for example, a pressure detection sensor, a transmitter, a battery, a control device, and an acceleration sensor. (Centrifugal switch) and the like. In this case, the acceleration sensor is used as a centrifugal switch to detect the centrifugal force acting on the running tire and to operate the tire condition monitoring device only when the vehicle is running, in order to extend the life of the battery. You.

Therefore, the centrifugal switch needs to be reduced in size and weight so that it can be attached to a tire wheel.

[0004] Various sensors using magnetoelectric conversion means, for example, a sensor described in Patent Document 1 have been proposed. In this displacement detection sensor, a spring portion displaced by external stress is formed in a meandering arm piece shape, and this spring portion is disposed axially or line-symmetrically with respect to the center axis of the movable portion. Then, a magnet is attached to the center of the movable part, and the magnet is changed. A magneto-electric conversion element is arranged at a position opposed in the shift direction, and a change in voltage due to a displacement of the magnet is detected as a displacement.

Patent Document 1: JP-A-6-230023

Disclosure of the invention

Problems to be solved by the invention

[0005] However, even if the displacement detection sensor of Patent Document 1 is used as an acceleration sensor, it is difficult to reduce the size due to its structure. There was a problem that it could not be downsized.

A well-known miniaturized acceleration sensor is a MEMS acceleration sensor. However, this MEMS acceleration sensor has a problem in that it cannot withstand vibration and impact during traveling when used in a tire.

Further, there is also an acceleration sensor using a coil panel. A sensor using the coil panel has a problem that the panel and the case are scraped off by sliding, and these have a problem that they are greatly affected by their life.

[0006] The present invention solves the above-mentioned problem, and detects acceleration generated in a tire by the applied force even when the tire attached to the vehicle is applied with enough force to be stolen. Of an acceleration sensor and a tire information transmission device with an acceleration sensor that can be reduced in size so that it can be mounted inside the tire and can withstand the vibrations and shocks of tens of thousands of kilometers of vehicle travel. For the purpose of providing.

Means for solving the problem

[0007] To achieve the above object, an acceleration sensor according to the present invention includes a planar spring having at least a base fixed inside a case, a magnet held by a central holding portion of the planar spring, An acceleration sensor including the magnet and a magneto-electric conversion unit that is disposed to face the case via a gap and that detects a magnetic change when the magnet moves, wherein the planar spring has one end connected to the base. It has a plurality of arms connected and the other end is an open end, and the holding portion is provided at an open end of at least two arms of the plurality of arms.

In this way, a small-sized planar spring having a small panel constant can be obtained. It can be installed in the ground, and can detect acceleration in the range of 0.3-5G.

[0008] Further, in the acceleration sensor of the present invention, the arm portion of the planar spring has a first arm extending in a radial direction, one end of which is an open end, and the other end force of the first arm. It comprises a second arm extending in the circumferential direction and connected to the base.

In this way, the effects of vibrations and shocks in the direction orthogonal to the acceleration direction can be reduced, and the magnet, weight, and panel do not generate the IJ scum due to the force of the case. As a result, it greatly contributes to improving the service life of the sensor.

Further, in the acceleration sensor of the present invention, the panel spring has a panel constant of 0.15-1.25 mN / mm.

[0010] The acceleration sensor of the present invention has a configuration in which a weight is attached to the magnet.

With this configuration, when the acceleration sensor is used as a centrifugal switch, the threshold centrifugal force can be easily set by adjusting the weight of the weight.

[0011] Further, the acceleration sensor of the present invention has a configuration in which the magnet is held by the sheet spring by holding the open end of the sheet spring by the magnet and the weight attached to the magnet. is there.

With this configuration, the center portion (the pinched portion) of the spring can be sandwiched between the magnet and the weight, and the downsized magnet can be attached to the spring. Further, if the clamped portion of the spring is sandwiched between the lower surface of the magnet and the upper surface of the weight (clamping portion) at a free end, the spring is easily elastically deformed, and the panel constant can be reduced. The size can be reduced.

[0012] The acceleration sensor of the present invention has a configuration in which the outer peripheral portion of the weight is chamfered so that even if the weight moves, only the holding portion of the weight contacts the spring.

With this configuration, even if the magnet and the weight move upward and the spring elastically deforms obliquely upward, it is possible to prevent a problem that occurs when the spring comes into contact with the upper part of the weight.

[0013] The acceleration sensor of the present invention is configured such that the planar spring has substantially the same diameter as the main body of the magnetoelectric conversion means.

With this configuration, the outer case to which the planar spring is attached is reduced in size, so that the acceleration sensor can be reduced in size.

[0014] In the acceleration sensor according to the present invention, a concave portion may be formed inside the case, and The base of the spring is fitted into the recess.

With this configuration, the positioning of the planar spring can be easily performed, and the positional accuracy of the magnet can be improved.

[0015] Further, the acceleration sensor of the present invention has a configuration in which a guide for restricting movement of the magnet in a direction orthogonal to the acceleration detection direction is provided inside the case.

In this way, even if an impact is applied in a direction perpendicular to the acceleration detection direction, even if vibration is applied, the movement distance of the magnet in this direction is limited, thereby preventing problems such as damage to the spring. can do.

Further, the acceleration sensor according to the present invention has a configuration in which the magnetic member is arranged at a position where the movement of the magnet is restricted by the magnetic attraction of the magnet while the acceleration acting on the magnet is smaller than a predetermined acceleration. There is.

In this manner, when an acceleration equal to or more than a predetermined acceleration is applied by utilizing the magnetic attraction force of the magnet, the acceleration can be detected for the first time.

As a method of urging the magnet in one direction, in addition to using magnetic attraction force, it is conceivable to use spring force or the like.However, in a miniaturized acceleration sensor, magnetic attraction force is used. Thereby, measurement accuracy and reliability can be improved.

[0017] The tire information transmitting device with an acceleration sensor of the present invention is attached to a tire cavity region surrounded by the inner peripheral surface of the tire and the wheel wall surface, and detects atmosphere information in the tire cavity region. A tire information transmission device with an acceleration sensor for wirelessly transmitting the tire information to the outside of the tire cavity area, wherein the acceleration sensor detects a rotation state of the tire and changes transmission information based on the rotation state detection signal. is there.

By doing so, the acceleration sensor can accurately detect the rotation state of the tire, so that malfunction of the tire information transmitting device can be prevented and reliability can be improved. Also, since the acceleration sensor is downsized, the tire information transmitting device can be downsized. The invention's effect

The acceleration sensor and the tire information transmitting device with the acceleration sensor according to the present invention use an acceleration sensor in which a magnet is joined to the center of a sheet spring. 1.25mNZmm), the degree to which the tire mounted on the car is stolen Even when a very small force is applied to the tire, it is possible to detect the acceleration (for example, 0.3G-5G) generated in the tire by the applied force. Further, at least two radially extending first arms arranged at regular intervals in the circumferential direction, and a second arm extending in the circumferential direction at the distal end force of the one arm. Therefore, the magnet attached to the leaf spring by the first arm can move as much as possible on the center axis of the planar spring, and the movement inside the center of the acceleration sensor due to the movement away from the center axis. Wear of the spring itself can be minimized. This makes it possible to withstand the vibrations and impacts of tens of thousands of kilometers of vehicle travel.

Brief Description of Drawings

FIG. 1 is a schematic enlarged view of an acceleration sensor according to an embodiment of the present invention, in which (a) is a top view and (b) is a cross-sectional view along AA.

FIG. 2 is a schematic enlarged plan view of a planar spring of an acceleration sensor according to an embodiment of the present invention.

FIG. 3 is a schematic enlarged cross-sectional view for explaining an operation state of the acceleration sensor according to the embodiment of the present invention.

FIG. 4 is a schematic sectional view of an acceleration sensor according to another embodiment of the present invention.

FIG. 5 is a schematic enlarged cross-sectional view for explaining an operation state of an acceleration sensor according to another embodiment of the present invention.

FIG. 6 shows a graph for explaining an output voltage curve of an acceleration sensor according to another embodiment of the present invention.

FIG. 7 is a schematic diagram for explaining a mounting state of a tire information transmitting device with an acceleration sensor according to an embodiment of the present invention.

FIG. 8 is a schematic diagram for explaining the structure of a tire information transmitting device with an acceleration sensor according to an embodiment of the present invention, where (a) is a cross-sectional view and (b) is a block diagram. .

FIG. 9 (A) is a conceptual diagram showing a positional relationship between the tire information transmitting device and the wheel, and is a diagram showing a state where the tire information transmitting device is located at an angle of 0 ° with respect to the wheel center. .

FIG. 9 (B) is a conceptual diagram showing the positional relationship between the tire information transmitting device and the wheel, FIG. 9 is a diagram showing a state where the tire information transmitting device is located at a position at an angle of 90 ° with respect to the center.

FIG. 9 (C) is a conceptual diagram showing the positional relationship between the tire information transmitting device and the wheel, and shows a state where the tire information transmitting device is located at an angle of 180 ° with respect to the center of the wheel. .

FIG. 9 (D) is a conceptual diagram showing a positional relationship between the tire information transmitting device and the wheel, and shows a state where the tire information transmitting device is located at an angle of 270 ° with respect to the wheel center. .

FIG. 10 is a diagram showing the output level of the acceleration sensor force when the tire is rotating at each position with respect to the wheel center of the tire information transmitting device.

FIG. 11 is a flowchart showing a process in the tire information monitoring device.

Explanation of symbols

1 Accelerometer

2 Magnetic material

3 Base

4 Outer case

5 Planar spring

6 magnet

7 Weight

8 Magnetoelectric conversion means

10 Tire information transmission device

11 Substrate

12 batteries

13 Sensor section

14 Analog to Digital Converter

15 Manorechi processor 18 Transmitting antenna

17a receiver

18a receiving antenna

19 Mold

19a Measurement hole

31 Magnetic member mounting hole

32 Through hole

33 Stepped part

41 notch

42 recess

43 magnet storage room

44 Spacer

51 Leaf spring

52 Annular

61 Press-fit hole

71 pin section

72 base

73 Chamfer

74 Holding part

81 External connection terminal

82 Magnetoelectric converter

90 tires

91 Inner circumference

92 Wheel wall

93 Tire cavity area

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1]

FIG. 1 is a schematic enlarged view of an acceleration sensor according to an embodiment of the present invention. The figure and (b) show the AA cross section.

In FIG. 1, an acceleration sensor 1 includes an outer case 4 provided on a base 3, a planar spring 5 attached to a lower portion of the outer case 4, and a magnet 6 attached to a central portion of the planar spring 5. And a weight 7, and magnetoelectric conversion means 8 attached to the upper part of the outer case 4.

The base 3 is a square plate made of non-permeable plastic, ceramic, or non-permeable metal, and has a side length of about 4 mm and a thickness of about lmm.

The four corners of the base 3 are formed with through holes 32 each having a stepped portion 33 as viewed from the lower surface side. The notches 41 of the outer case 4 are inserted into the through holes 32. Then, the outer case 4 is fixed to the base 3 by subjecting the leading end of the notch 41 to plastic working by heating and engaging with the stepped portion 33.

The method of fixing the outer case 4 is not limited to the method using the notch 41.

The outer case 4 is made of a non-magnetically permeable plastic or the like, and has a substantially cubic shape with a side of about 4 mm and a height of about 3 mm on a square upper surface.

The outer case 4 has a substantially rectangular recess 42 formed on the upper surface thereof. The recess 42 accommodates the magnetoelectric conversion device main body 82, and further includes a bonding agent between the recess 42 and the magnetoelectric conversion device main body 82. Filling (not shown) causes the magnetoelectric conversion means main body 82 to be embedded in the concave portion 42.

Here, it is preferable that a recess 421 into which the bottom of the main body 82 is fitted is formed on the bottom of the recess 42. By doing so, the magnetoelectric conversion means main body 82 can be accurately positioned.

Further, a notch 422 for passing the external connection terminal 81 of the magnetoelectric conversion means 8 is formed in a part of the wall formed by forming the concave portion 42. By doing so, the external connection terminal 81 of the magnetoelectric conversion means 8 does not need to be processed into a complicated shape, and the magnetoelectric conversion means 8 is buried at a position lower than the upper surface of the outer case 4. Therefore, damage to the magnetoelectric conversion means 8 can be prevented.

[0025] The outer case 4 has a three-stage cylinder on the lower surface, the diameter of which is reduced in a stepwise manner as the diameter is directed upward. A magnet storage chamber 43 is formed.

An annular spacer 44 for fixing the annular portion 52 of the planar spring 5 (see FIG. 2) is press-fitted into the first cylindrical concave portion 431 having the largest diameter located at the lower stage of the magnet storage chamber 43. The upper surface of the spacer 44 presses the annular portion 52 of the planar spring 5 against the first stepped portion 431a, thereby fixing the planar spring 5 to the outer case 4.

The second cylindrical recess 432 located in the middle of the magnet storage chamber 43 is a space for the planar spring 5 to move freely when the magnet 6 moves.

Further, the third cylindrical concave portion 433 having the smallest diameter located at the upper stage of the magnet storage chamber 43 is a space for the magnet 6 which has been subjected to the upward (acceleration detecting direction) acceleration to move upward. . The third cylindrical concave portion 433 has a depth of about 0.6 mm, and moves upward by about 0.3 mm from a state where the magnet 6 is inserted by about 0.3 mm.

Here, it is preferable that the diameter of the third cylindrical concave portion 433 is larger than the diameter of the magnet 6 by about 0.05 mm. In this way, the side surface of the third cylindrical concave portion 433 serves as a guide for restricting the movement of the magnet 6 in a direction orthogonal to the acceleration detection direction, so that when an acceleration acts in a direction orthogonal to the acceleration detection direction. Even in this case, the moving distance of the magnet 6 in this direction is limited, and the problem that the planar spring 5 is damaged can be prevented. The case where the acceleration acts in the direction perpendicular to the acceleration detection direction is, for example, the case where the acceleration sensor 1 (centrifugal switch) attached to the tire wheel is in the horizontal direction, and the magnet 6 and the weight 7 are In (b), gravitational acceleration acts in the left-right direction. Angular acceleration also acts when the rotating tire suddenly stops due to sudden braking.

FIG. 2 is a schematic enlarged plan view of a planar spring of the acceleration sensor according to the embodiment of the present invention.

In the figure, the planar spring 5 includes three leaf springs 51 having a predetermined shape, and an annular portion 52 that connects the ends of the respective leaf springs 51 in the outer circumferential direction.

The leaf spring 51 includes a circumferential leaf spring portion 511 formed in the circumferential direction and a radial leaf spring portion 512 formed in the radial direction. The circumferential leaf spring portion 511 and the radial leaf spring portion are provided. By connecting 512 and selecting the width and length of each board, slab, bending shape, A spring having the required spring characteristics can be manufactured.

The leaf spring 51 has a small panel constant in the acceleration detection direction (thickness direction) and has a low rigidity. The reason for reducing the panel constant is to make the acceleration sensor small and sensitive. In the leaf spring 51 of the present embodiment, the circumferential leaf spring 511 is formed in an arc shape, the spring portion is lengthened, and the panel constant is reduced.

On the other hand, the panel constant in the radial direction from the held portion 513 of the leaf spring 51 is set large to increase rigidity. The reason for increasing the panel constant is that the magnet 6 and the weight 7 are prevented from moving in the direction perpendicular to the acceleration detection direction due to external shock and vibration, and the magnet 6 and the weight 7 collide with the inner periphery of the case 4. This is to prevent the case 4 from being worn. In the leaf spring 51 of the present embodiment, the spring width of the circumferential leaf spring 511 is made 15 to 25 times or more larger than the spring thickness, and has a rigidity of 225 to 625 times the panel constant in the thickness direction.

The panel constant of the leaf spring 51 is set to 0.15-1.25 mNZmm, and the detected acceleration is 0.3-5G. In areas where the panel constant is small, it is installed inside vehicle-related tires, and is also used for detecting theft of tires.

[0029] Further, since the planar spring 5 is formed by integrating a plurality of leaf springs 51 with each other by an annular annular portion 52 connecting ends of the respective leaf springs 51 in the outer peripheral direction, the leaf springs 51 are formed. Even if the size is reduced, a plurality of leaf springs 51 can be assembled and assembled efficiently. Further, since the annular portion 52 is fitted into the first cylindrical concave portion 431 of the outer case 4, the planar spring 5 can be easily attached, and the magnet 6 can be accurately positioned.

Further, the planar spring 5 has a structure in which the ends (the pinched portions 513) of the leaf springs 51 in the center direction are not connected to each other. By doing so, for example, although not shown, a space for providing a connecting portion or an annular portion on the center side of the planar spring 5 becomes unnecessary, and the planar spring 5 is reduced in size by this space. be able to.

Further, it is preferable that the planar spring 5 has substantially the same diameter as the magnetoelectric conversion means main body 82. By doing so, the outer case 4 to which the planar spring 5 is attached can be reduced in size, so that the acceleration sensor 1 can be reduced in size. The phrase "the planar spring 5 has substantially the same diameter as the main body 82 of the electromagnetic conversion means" means that the diameter of the main body 82 of the electromagnetic conversion means falls within a range of 0.7 to 1.3 times the diameter of the spring 5 of the planar spring. , Which means that the four corners are located. Further, the planar spring 5 can be formed in various shapes other than the above-mentioned shape, and for example, the connecting portion or the annular portion may be provided.

[0031] The magnet 6 is a bonded magnet mainly composed of neodymium (Nd) 'iron (Fe) and boron (B), and has a press-fit hole 61 into which a pin 71 of the weight 7 is press-fitted in the center. It has a formed cylindrical shape, the upper surface is an N pole, and the lower surface is an S pole. The outer diameter is about 1.3mm and the height is about 0.6mm.

In the present embodiment, the weight 7 is press-fitted into the magnet 6, and the weight 7 is directly coupled to the magnet 6. Therefore, there is no need for a magnet arrangement case member for installing the magnet. Therefore, the number of parts can be reduced, the cost can be reduced, and the acceleration sensor can be downsized. On the other hand, the method of press-fitting the magnet 6 into the weight 7 makes it easier to achieve coaxiality and increases the assembly accuracy as compared with the method of fixing the magnet and the weight with an adhesive or the like.

The magnet 6 of the present embodiment is not limited to a certain force as the bond magnet described above. For example, a permanent magnet such as a ferrite magnet or a rare earth magnet can be used.

Preferably, the size of the magnet 6 is smaller than that of the main body 82 of the magnetoelectric conversion means. As described above, when the magnet 6 for performing the acceleration detection is reduced in size, the planar spring 5 to which the magnet 6 is attached and the outer case 4 to which the planar spring 5 is fixed can be reduced in size. . For example, it is possible to reduce the size of the acceleration sensor 1 to the size specified by the magnetoelectric conversion means 8.

The weight 7 is made of a non-magnetically permeable metal, for example, a copper-based metal such as brass, and has a substantially cylindrical base 72, a pin 71 protruding from the center of the upper surface of the base 72, and the pin 71. And the chamfered portion 73 connecting the base 72 and the base 72. The pin portion 71 is pressed into the press-fit hole 61 of the force magnet 6 through the center of the planar spring 5.

In this way, when the weight 7 is attached to the magnet 6 and the acceleration sensor 1 is used as a centrifugal switch, the weight of the weight 7 can be adjusted to freely set the threshold centrifugal force. it can.

[0034] Further, due to the press-fitting, the clamped portion 513 of the radial leaf spring portion 512 of the planar spring 5 has a gap in the vertical direction between the lower surface of the magnet 6 and the clamp portion 74 of the weight 7. It is pinched in a state. In this way, the clamped portion 513 of the planar spring 5 is connected to the lower surface of the magnet 6 and the clamped portion 7 of the weight 7. 4, the spring constant of the planar spring portion 5 can be reduced as compared with the case where the flat spring portion 5 is supported in a state where there is no gap in the vertical direction (fixed end state). .

[0035] In the present embodiment, the clamped portion 513 of the planar spring 5 is clamped with a gap in the vertical direction, but may be supported without a gap in the vertical direction. By doing so, for example, the acceleration sensor 1 (centrifugal switch) attached to the tire wheel receives the gravitational force whose direction of action rotates together with the centrifugal force, so that the magnet 6 and the weight 7 incline with the held portion 513 as a fulcrum. Therefore, the posture of the magnet 6 and the weight 7 can be maintained along the central axis of the acceleration sensor 1.

[0036] Preferably, the inner diameter of the spacer 44 is about 0.2 mm larger than the outer diameter of the base 72 of the weight 7, and the inner side surface of the spacer 44 is used as a guide. In this way, even when acceleration is applied in a direction orthogonal to the acceleration detection direction, the movement distance of the weight 7 in this direction is limited, so that there is a problem that the planar spring 5 is damaged. Can be prevented. In addition, it is possible to prevent a problem that the postures of the magnet 6 and the weight 7 become unstable, and the acceleration cannot be accurately detected.

Further, when the weight 7 moves upward, the outer peripheral portion above the weight 7 is chamfered so that the weight 7 does not come into contact with the surface spring 5 excluding the holding portion 74. .

In this case, even when the magnet 6 and the weight 7 move upward, and the leaf spring 51 of the planar spring 5 elastically deforms obliquely upward, the leaf spring 51 comes into contact with the chamfered portion 73 of the weight 7. Can be prevented.

The magnetoelectric conversion means 8 has a built-in magnetoelectric conversion element (not shown) for detecting magnetism in the lower surface direction inside the magnetoelectric conversion means main body 82, and four external connections from the magnetoelectric conversion means main body 82. Terminal 81 protrudes.

The external connection terminal 81 extends in the horizontal direction from the side surface of the main body 82 of the magnetoelectric conversion means, bends downward when coming out of the outer case 4, and again in the horizontal direction at the same height position as the lower surface of the base 3. It is a bent surface mount type lead. In this way, it is possible to efficiently mount the miniaturized acceleration sensor 1 having dimensions of about 5 mm X 4 mm X 3 mm on the mounting board (not shown) using the surface mounting technology. it can.

FIG. 3 is a schematic diagram for explaining an operation state of the acceleration sensor according to the embodiment of the present invention. FIG. 3 shows a substantially enlarged sectional view.

In FIG. 3, when the acceleration sensor 1 is used on the earth, it always receives gravitational acceleration. Accordingly, when the magnetoelectric conversion means 8 is positioned above (the state shown in FIG. 1 (b)), the acceleration sensor 1 receives the gravitational acceleration of the magnet 6 and the weight 7, and the lower surface of the weight 7 is in contact with the upper surface of the base 3. Abut. On the other hand, when the magnetoelectric conversion means 8 is located below the magnet 6 (the state shown in FIG. 3 is rotated by 180 degrees), the upper surface of the magnet 6 contacts the bottom surface of the third cylindrical concave portion 433.

[Embodiment 2]

FIG. 4 is a sectional view of an acceleration sensor according to another embodiment of the present invention. In the figure, the difference from the embodiment of FIG. 1 is that the magnetic member 2 is embedded in the base 3. The base 3 has a magnetic member mounting hole 31 having a depth of about 0.5 mm in the center of the lower surface, and the magnetic member 2 is press-fitted into the magnetic member mounting hole 31.

The magnetic member 2 pressed into the magnetic member mounting hole 31 is a circular plate having a diameter of about lmm and a plate thickness of about 0.2 mm.

The magnetic member 2 is made of a material having magnetic permeability, such as iron. Usually, an iron-nickel alloy (permalloy) and ferrite having excellent magnetic permeability are used. As described above, by using permalloy, which is a ferromagnetic material, the size of the magnetic member 2 can be reduced.

The magnitude of the magnetic attraction generated between the magnetic member 2 and the magnet 6 can be set by adjusting the distance, the area, and the like of the magnetic member 2. The magnet 6 can be attracted in the direction of the magnetic member 2 by the action of the magnetic attraction.

Also, when an external force having a magnitude equal to or greater than the magnetic attraction force and the gravity acts on the magnet 6 and the weight 7, the magnet 6 moves in the direction of the magnetoelectric conversion means 8. By detecting the magnetic change due to the movement of the magnet 6 by the electromagnetic conversion means 8, the acceleration sensor 1 can detect an acceleration equal to or higher than a predetermined acceleration.

[0042] The magnetic member 2 is provided below the magnet 6, and a magnetoelectric conversion means 8 is provided above the magnet 6. That is, the magnetic member 2 is provided on the opposite side of the magnetoelectric conversion means 8 with the magnet 6 interposed therebetween. In this way, the magnetic flux generated from the S pole of the magnet 6 enters the magnetic member 2 in a substantially straight line, and the magnetic flux generated by the magnetoelectric conversion means 8 side (N pole side) is not disturbed. (Not shown), so there is no adverse effect such as disturbance of magnetic flux Stable detection can be performed. Further, since the magnetic flux generated from the S pole of the magnet 6 enters the magnetic member 2 in a substantially linear shape, the magnetic attractive force is stabilized, and the measurement accuracy can be further improved.

Next, an operation of the acceleration sensor 1 having the above configuration will be described with reference to the drawings.

FIG. 5 is a schematic enlarged cross-sectional view for explaining an operation state of the acceleration sensor according to the embodiment of the present invention.

FIG. 6 is a graph for explaining an output voltage curve of the acceleration sensor according to the embodiment of the present invention.

In FIG. 5, when the acceleration sensor 1 is used on the earth, it always receives a gravitational acceleration (one 1G: a downward acceleration is defined as 1, and an upward acceleration is defined as +). Therefore, when the magnetoelectric conversion means 8 is located above and the magnetic member 2 is located below, the acceleration sensor 1 is configured such that the magnet 6 and the weight 7 receive the gravitational acceleration. Since they are in contact with each other (see Fig. 4), the leaf spring 51 of the planar spring 5 does not bend downward. In this case, the leaf spring 51 is deformed to only one side (between the horizontal direction and the obliquely upward direction), and the acceleration sensor 1 does not move the magnet 6 downward even if the acceleration sensor 1 receives further downward acceleration. Therefore, this acceleration is not detected.

The acceleration sensor 1 receives an acceleration in an upward direction (acceleration detection direction), and when the acceleration gradually increases from 0 to +1 G, a force that offsets the gravitational acceleration (-1 G). The magnetic member 2 and the magnet Between 6, the magnetic attraction car a G is acting.

Then, when the acceleration further increases from + 1G to + (l + a) G, the magnetic attraction force is canceled out, and the magnet 6 and the weight 7 stand still in a zero-gravity state (see FIG. 4).

Subsequently, when the acceleration further increases from + (1 + oG), the acceleration sensor 1 gradually raises the magnet 6 and the weight 7 in a state of being balanced with the spring force of the planar spring 5, and 8 detects the movement of the magnet 6 as acceleration, and the output voltage increases.

As shown in FIG. 5, when the top surface of the magnet 6 abuts on the bottom surface of the third cylindrical concave portion 433, the spring force of the planar spring 5 at this time is | 8 G, and the acceleration of the magnet 6 and the weight 7, the acceleration of + (1 + α + β) G acts.

Since the magnet 6 cannot be raised even if the acceleration increases further, the acceleration sensor 1 The voltage is constant.

As described above, the acceleration sensor 1 according to the present embodiment can detect acceleration from + (1 + a) G to + (1 + α + j8) G. Therefore, when the state force is inverted upside down and the magnetoelectric conversion means 8 is located below and the magnetic member 2 is located above, the acceleration sensor 1 causes the magnet 6 and the weight 7 to have a gravitational acceleration of +1 G. Force subject to acceleration This acceleration is not detected.

That is, when the acceleration sensor 1 is used in the tire condition monitoring device, even if the tire stops in a state where the magnetoelectric conversion means 8 is located below and the magnetic member 2 is located above, the tire rotates at this gravitational acceleration. Since it is not detected as centrifugal force, malfunction can be prevented. Furthermore, by utilizing the magnetic attraction force of the magnet 6, the acceleration sensor 1 can improve measurement accuracy and reliability and can be downsized.

[Tire Information Transmitter with Acceleration Sensor]

FIG. 7 is a schematic diagram for explaining an attached state of the tire information transmitting device with the acceleration sensor according to the embodiment of the present invention.

In the figure, a tire information transmitting device 10 with an acceleration sensor (abbreviated as tire information transmitting device 10 as appropriate) is attached to a tire cavity region 93 surrounded by an inner peripheral surface 91 of a tire 90 and a wheel wall surface 92.

FIG. 8 is a schematic diagram for explaining the structure of a tire information transmitting device with an acceleration sensor according to an embodiment of the present invention, in which (a) is a cross-sectional view, and (b) is a block diagram. In the figure, a tire information transmitting device 10 includes a substrate 11, a battery 12 provided on the lower surface of the substrate 11, a sensor unit 13 mounted on the substrate 11, an analog-to-digital converter 14, Multiprocessor 15, storage unit 16, transmitting unit 17, transmitting antenna 18, receiving unit 17a, receiving antenna 18a and the acceleration sensor 1 used as a centrifugal switch, and the above components 11, 13, 14, 15, 16, 17, 18, 17a, 18a, 1 and Moronored 咅 19 are powerful. The mold section 19 has a measurement hole 19a at a position corresponding to the sensor section 13.

[0049] The multiprocessor 15 includes a sensor unit 13, an analog-to-digital converter 14, a storage unit 16, The communication unit 17, the reception unit 17a, and the acceleration sensor 1 are connected to each other, and control these to detect atmosphere information (generally, pressure, Z or temperature, etc.) in the tire cavity 93, and Transmit wirelessly outside the cavity area.

Hereinafter, usage examples when the acceleration sensors described in Embodiments 1 and 2 are mounted on the tire information transmitting device 10 will be described.

[Example in which the acceleration sensor according to the first embodiment is used]

FIG. 9 is a conceptual diagram showing the positional relationship between the tire information transmitting device and the wheel. FIG. 9 (A) shows a state in which the tire information transmitting device is located at an angle of 0 ° with respect to the wheel center. FIG. 9 (B) is a view showing a state in which the tire information transmitting device is located at an angle of 90 ° with respect to the wheel center, and FIG. 9 (C) is a view showing an angle of 180 ° with respect to the wheel center. Fig. 9 (D) is a diagram showing a state in which the tire information transmitting device is located at a position of 270 ° with respect to the center of the wheel. It is.

FIG. 9 (A) shows a case where the tire information transmitting device 10 is located at an angle of 0 ° with respect to the center of the wheel 92, that is, a case where the tire information transmitting device 10 is located above the wheel 92. . Here, when the tire is stationary, that is, when centrifugal force due to the rotation of the tire 90 is not acting on the tire information transmitting device 10, the acceleration sensor 1 installed in the tire information transmitting device 10 is as shown in FIG. In addition, the weight 7 of the acceleration sensor 1 is in contact with the base 3.

[0053] Conversely, as shown in FIG. 9 (C), when the tire information transmitting device 10 is positioned at an angle of 180 ° with respect to the center of the wheel 92, regardless of whether the tire 90 is stationary or not. As shown in FIG. 3, the upper surface of the magnet 6 of the acceleration sensor 1 comes into contact with the bottom surface of the third cylindrical concave portion 433.

In the case shown in FIGS. 9 (B) and 9 (D) and when the tire is in a stationary state, the acceleration sensor 1 installed in the tire information transmitting device 10 Is in contact with the base 3! /

FIG. 10 is a diagram showing a change in the output level of the acceleration sensor when the tire rotates at each position with respect to the wheel center of the tire information transmitting device. When the rotation of the tire is extremely low, the upper surface of the magnet 6 of the acceleration sensor 1 is located at the position just before the tire information transmitting device 10 at an angle of 180 ° with respect to the wheel 92, and the bottom surface of the third cylindrical concave portion 433. At this point, the output level of the acceleration sensor 1 changes from S "L" to "H".

When the tire further rotates past 180 °, the acceleration sensor 1 enters a state as shown in FIG. 1, that is, a state in which the weight 7 of the acceleration sensor 1 is in contact with the base 3, and at this time, the acceleration The output level of sensor 1 changes from "H" to "L".

[0057] The output level of the acceleration sensor 1 is stabilized in the state of "H" at a rotation speed higher than the rotation speed at which the tire rotates at a high speed and the centrifugal force becomes larger than the gravity.

As described above, when the tire rotates at a low speed, the output level of the acceleration sensor 1 changes from “L” → “H” → “L” once per rotation.

[0059] The tire information transmitting device 10 of the present invention transmits a signal indicating that the tire is rotating at a low speed based on the output of the acceleration sensor. On the other hand, a tire information monitoring device (not shown) is provided inside the vehicle on which the tires are mounted, and receives a signal from the tire information transmitting device 10 and notifies the driver and the like. If the tires are running at low speed without the car's induction switch in place, it is determined that the vehicle is stolen and an alarm is issued. FIG. 11 is a flowchart showing processing in the tire information monitoring device.

[0060] Stepl: If the car is in the ON / OFF state when the car's induction switch is ON !, go to Step6. If the car is in the OFF state (OFF), go to Step2.

[0061] Step 2: If the induction switch is turned on and the state is (OFF), the tire information monitoring device can receive a signal from the tire information transmitting device 10 by a receiving device (not shown). , Step3 @ ko it

[0062] Step 3: Determine whether the signal received from the tire information transmitting device 10 is a signal indicating that the tire is rotating at a low speed, and if the tire is rotating at a low speed (YES), proceed to Step 4; Return to Stepl.

[0063] Step4: If the tire is in the state (OFF) and the low speed rotation state is detected without the induction switch, it is determined that the vehicle is stolen, and an alarm is sounded by an alarm device (not shown).

Go to Step5. Step 5: If a reset signal from the tire information monitoring device or the like is received (YES), the alarm of the alarm device (not shown) is released, and the process returns to Step 1 and returns to Step 5 until the reset signal is received. Wait for reset signal.

[0065] Step 6: If it is determined in step 1 that the induction switch has entered the ON / OFF state, the tire information monitoring apparatus determines the tire state received from the tire information transmitting apparatus 10, ie, the tire state. The air pressure in the tire cavity 93, the temperature 93 in the tire cavity, and the like are displayed on a display device (not shown). If the air pressure and temperature are out of the range of the normal values, processing such as sounding an alarm by an alarm device (not shown) is performed. The processing in Step 6 is an example, and various applications can be considered.

[Example Using Acceleration Sensor of Second Embodiment]

An example in which the acceleration sensor described in the second embodiment is used as a switch for extending the life of the battery 12 of the tire information transmitting device 10 will be described.

When the acceleration sensor 1 detects the rotation state (including the stationary state) of the tire 90, the multiprocessor 15 changes the transmission information according to the rotation state detection signal. For example, when the multiprocessor 15 determines that the tire 90 has stopped based on the rotation state detection signal, the multiprocessor 15 stops detecting the atmosphere information and transmitting the detection result so as not to consume the power of the battery 12. Further, the pressure is detected as the atmosphere information in the tire cavity 93 every hour based on the rotation state detection signal, and the pressure is wirelessly transmitted to the outside of the tire cavity. Further, when the multiprocessor 15 determines that the tire 90 is rotating at a high speed based on the rotation state detection signal, the pressure and the temperature are detected every 10 minutes as atmosphere information in the tire cavity area 93, and the tire 90 is detected. Transmit wirelessly outside the cavity area.

[0068] According to the tire information transmitting apparatus 10 of the present embodiment, the acceleration sensor 1 accurately detects the rotation state of the tire 90 regardless of the gravitational acceleration of the person 1G acting every time the tire 90 rotates. Therefore, malfunction of the tire information transmitting device can be prevented and reliability can be improved. Further, since the acceleration sensor 1 is downsized, the tire information transmitting device 90 can be downsized.

Further, the transmission information can be changed by the rotation state detection signal from the acceleration sensor 1, so that the atmosphere of the tire 90 according to the driving condition can be effectively used while effectively using the power of the battery 12. Ambient information can be transmitted wirelessly outside the tire cavity area.

Although the acceleration sensor and the tire information transmitting device with an acceleration sensor according to the present invention have been described above with reference to the preferred embodiments, the acceleration sensor and the tire information transmitting device with an acceleration sensor according to the present invention have the above-described implementation. It is needless to say that various modifications can be made within the scope of the present invention.

For example, although the acceleration sensor 1 uses the magnet 6 and the magnetic member 2 as means for generating a magnetic attraction force, when a larger magnetic attraction force is required, a magnet is used instead of the magnetic member 2. May be used.

Further, when the magnetic attraction force acting on the magnet 6 is increased, the acceleration sensor 1 reduces the spring force of the planar spring 5 when the magnetoelectric conversion means 8 is located below and the magnetic member 2 is located above. The magnet 6 and the weight 7 can be attracted upward (to the base 3 side) without being used. In such a case, the planar spring 5 is used as a means for adjusting the posture of the magnet 6 and the weight 7.

[0072] Furthermore, the tire information transmitting apparatus 10 may have a configuration in which a plurality of acceleration sensors 1 having different detection areas are provided. In this case, the atmosphere information corresponding to the rotation speed of the tire 90 in a wide range can be further improved. It can be transmitted in a finely divided state.

Industrial applicability

[0073] The acceleration sensor of the present invention can also be applied as a measurement device such as a displacement sensor using a magnetoelectric conversion unit or an acceleration switch.

Claims

The scope of the claims

[I] A planar spring having at least a base fixed to the inside of the case, a magnet held by a holding portion at the center of the planar spring, and disposed facing the case via a gap with the magnet. A caro speed sensor comprising: a magnetoelectric conversion means for detecting a magnetic change when the magnet moves.

The planar spring has a plurality of arms each having one end connected to the base and the other end being an open end, and the holding unit includes an open end of at least two of the plurality of arms. An acceleration sensor installed in a vehicle.

[2] The arm portion of the planar spring has a first arm extending in a radial direction having an open end at one end thereof, and a circumferentially extending arm extending from the other end of the first arm. The acceleration sensor according to claim 1, comprising a second arm connected to the second arm.

[3] The acceleration sensor according to claim 1, wherein the planar spring has a panel constant of 0.15-1.25 mNZmm.

[4] The acceleration sensor according to claim 1, wherein a weight is attached to the magnet.

5. The acceleration sensor according to claim 4, wherein the magnet is held by the sheet spring by holding the open end of the sheet spring by the magnet and the weight attached to the magnet. .

6. The acceleration sensor according to claim 5, wherein an outer peripheral portion of the weight is chamfered.

7. The acceleration sensor according to claim 1, wherein the planar spring has substantially the same diameter as the main body of the magnetoelectric conversion unit.

[8] The acceleration sensor according to claim 1, wherein a recess is formed inside the case, and a base of the planar spring is fitted into the recess.

[9] The acceleration sensor according to claim 1, wherein a guide for restricting movement of the magnet in a direction orthogonal to the acceleration detection direction is provided inside the case.

10. The magnetic member according to claim 1, wherein a magnetic member is arranged at a position where the movement of the magnet is regulated by a magnetic attraction force of the magnet while the acceleration acting on the magnet is smaller than a predetermined acceleration. Acceleration sensor.

[II] An acceleration sensor according to any one of claims 1 to 10, wherein the acceleration sensor according to any one of claims 11 to 10, A tire information transmission device with an acceleration sensor, which is attached to a tire cavity region surrounded by a wheel wall surface, detects atmosphere information in the tire cavity region, and wirelessly transmits the outside of the tire cavity region,

A tire information transmitting device with an acceleration sensor, wherein the acceleration sensor detects a rotation state of the tire, and changes transmission information based on the rotation state detection signal.