JP2647287B2 - Pressure sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor, and more particularly, to a pressure sensor used in a device for detecting an abnormality in tire pressure in a truck, a bus or the like.

[0002]

2. Description of the Related Art It is preferable for safe driving to monitor the air pressure in a tire when the wheel is rotating or stationary. For this reason, conventionally, a tire internal pressure abnormality detecting device that issues an alarm when the air pressure of the tire falls below a predetermined value has been proposed. This tire internal pressure abnormality detection device connects a pressure switch attached to a substantially central portion of a tire wheel and a tire air chamber with a copper pipe,
A resonance circuit including a pressure switch and a transmission circuit mounted on an axle are magnetically coupled to transmit a detection signal. According to the tire internal pressure abnormality detection device, the internal pressure in the tire air chamber acts on the pressure switch via the pipe, and when the tire internal pressure falls below a predetermined value, the pressure switch is turned off, and the abnormal state of the tire is detected.

[0003]

However, the conventional pressure sensor is composed of a pressure switch and a pipe that electrically connects the pressure switch and the tire air chamber. For example, air leakage occurs due to such factors, and thus there is a problem in vibration resistance and fatigue durability. In addition, since it is necessary to provide a play intentionally in order to cope with the vibration resistance and the fatigue durability, there is a problem that mounting accuracy is inferior.

The present invention has been made to solve the above problems, and has as its object to provide a pressure sensor having improved vibration resistance and fatigue durability.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides one or more pressure switches which are directly connected to an air valve provided on a tire to detect a change in the internal pressure of a tire air chamber, and an electric wire. A transmitter connected to the pressure switch via the same and transmitting the detection result of the pressure switch, and connecting the pressure switch and the transmitter and coating the electric wire so that tension does not act on the electric wire. And a flexible protective tube.

[0006] A stop for attaching the pressure sensor to the tire wheel can be provided on the protective tube so as to be movable in the longitudinal direction of the protective tube.

When the protective tubes are connected to each other, one end of each protective tube is inserted with a resin interposed between the holes formed in the housing, and the housing and the protective tube are penetrated. It is effective to drive and connect the punch. When the direction of the protective tube is changed to a substantially right angle direction, substantially orthogonal holes are provided in the housing, and one end of the protective tube may be connected to each hole of the housing by a resin and a punch as described above. .

[0008]

The pressure switch for detecting a change in the internal pressure of the tire air chamber according to the present invention can be directly connected to an air valve provided in the tire. The direct connection here includes not only the case where the pressure switch is directly attached to the air valve but also the case where the connection is made via a relatively short adapter. For this reason, the distance between the tire air chamber and the pressure switch, that is, the detection unit, is reduced. This pressure switch is connected via a wire to a transmitter for transmitting the detection result of the pressure switch. The wire is also covered by a flexible protective tube connecting the pressure switch and the transmitter so that tension is not applied. Therefore, by attaching this protective tube to the tire wheel by applying an appropriate tension, it can be attached with high accuracy, thereby minimizing the influence of tire rotation and vibration, and improving vibration resistance and fatigue durability. can do. Further, since the electric wire is covered by the protective tube so that no tension acts, even if the electric wire is attached to the tire wheel by applying an appropriate tension to the protective tube, the electric wire can be prevented from being broken.

If a stopper for attaching the pressure sensor to the tire wheel is provided on the protective tube so as to be movable in the longitudinal direction of the protective tube, an appropriate tension is applied to the protective tube to attach the tire to the tire wheel. It will be easier.

When connecting the protective tube to the protective tube, a housing having a hole formed between the protective tubes is provided, one end of the protective tube is inserted into the hole, and the protective tube is connected to the housing with a resin and a punch. If the connection is made, the protection tube can be prevented from rotating by punching, and dust can be prevented from entering the protection tube by the resin. Also, by using this connection, the direction of the protective tube can be changed to a substantially right angle direction or the like.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. This embodiment uses two pressure switches. As shown in FIG. 1, the pressure switch 10A
It is connected to a coupling housing 16A made of aluminum via a flexible protective tube 12A. Combined housing 1
6A is connected to a coupling housing 16B having substantially the same configuration as above via a flexible protective tube 12B having a spiral groove (see FIG. 3) formed on the outer peripheral surface. The coupling housing 16B is
Protection tube 12C having the same configuration as protection tube 12A
Is connected to a pressure switch 10B having the same configuration as the pressure switch 10A. The coupling housing 16B is connected to the transmitter (transmitter) 14 via a protection tube 12B having the same configuration as the protection tube 12B. A stop 18 is attached to the protection tubes 12B and 12D so as to be movable in the length direction of the protection tubes. A spiral groove may be provided on the outer peripheral surfaces of the protective tubes 12A and 12C, similarly to the protective tubes 12B and 12D, but a spiral groove may not be provided since a stopper is not attached. Pressure switch 12A, 12B
And the transmitters 14 are interconnected by wires that are housed in a protective tube so that no tension is exerted, i.e. are covered in a loose state by the protective tube. In the above description, the two pressure switches and the transmitter are connected, but one pressure switch or three or more pressure switches may be connected to the transmitter.

Next, the pressure switch will be described. Since the pressure switches 12A and 12B have the same configuration, only one of the pressure switches will be described. As shown in FIG. 2, the pressure switch includes a substantially cylindrical first housing 20 having a small diameter at the distal end 20A and a large diameter at the proximal end 20B. The first housing 20 is made of brass. First
A second end having a base end 24B having the same diameter as the base end 20B of the first housing 20 and a small-diameter portion 24A having a smaller diameter than the base end 24B is provided on the base end 20B side of the first housing 20. Are arranged such that the base end 24B faces the base end 20B of the first housing 20. The second housing 24 is made of phosphor bronze. In the small diameter portion 24A of the second housing 24,
An insulator 26 made of ceramics is interposed between the small-diameter portion 24A and an electrode receiver 28 made of phosphor bronze having an internal thread formed on the inner peripheral surface. This electrode receiver 2
As shown in FIG. 2, the male screw 8 has a substantially cylindrical fixing in which an external thread 32 is engraved on the outer peripheral surface, a spherical portion 31 is formed at the distal end, and an adjusting groove 36 is formed at the proximal end. The electrode 30 is screwed. A flange 34 is provided on the base end side of the fixed electrode 30. This fixed electrode 30 is formed of stainless steel.

The radius R of the spherical portion 31 formed at the tip of the fixed electrode 30 is 0.75 mm. By setting the radius R of the spherical portion to a value in the range of 0.3 to 1.5 mm, it is possible to improve the pressure resistance and the contact property. When the radius is less than 0.3 mm, the sharpness is too sharp, so that the pressure resistance is inferior, so that it is easy to break. The spherical portion is plated with 10 μm gold. The pitch length of the male screw 32 is 0.25 m.
m. If the external thread pitch is made as small as possible, the adjustment accuracy can be improved.

Between the base end 20B of the first housing 20 and the base end 24B of the second housing 24, a phosphor bronze bronze having a 10 μm gold-plated surface on the fixed electrode 30 side is provided. A movable electrode 38 which is a conductive elastic thin film formed of a thin film (about 0.2 mm in thickness) is sandwiched. This movable electrode 38
A sealing material 40 such as solder is interposed between the base end portion 20B and the base end portion 24B, and the base end portion 20B and the base end portion 24B are caulked with a third housing 52 made of stainless steel, so that the peripheral edge is formed. A chamber 21 is formed in the first housing 20 so as to be airtightly sandwiched. The movable electrode 38 is sandwiched so as to be in a flat state, that is, so as not to bend.

As described above, since the surface of the fixed electrode and the surface of the movable electrode in contact with the fixed electrode are gold-plated, the ability to detect contact and non-contact can be improved. In addition,
Instead of gold plating, another conductive material may be coated.

An electric wire 44 of a wire harness 45 is soldered to the flange 34 of the fixed electrode 30, and the second housing 24
The electric wire 42 of the wire harness 45 is soldered to the small diameter portion 24A. Note that this soldering is performed after a driver or the like is inserted into the adjustment groove 36 to rotate the fixed electrode 30 so that the spherical portion 31 of the fixed electrode 30 comes into contact with the movable electrode 38 in the flat state. . Since the fixed electrode is provided with a flange and the wire harness is soldered to the flange, the solder does not flow into the adjustment groove and hardens in the adjustment groove. The wire harness 45 projects through a fourth housing 54 fixed to the third housing 52 with an adhesive 48,
It is fixed by the resin 46 filled in the fourth housing 54. A protruding portion of the wire harness 45 from the fourth housing 54 is sealed with a packing 50 and a resin 56.

In this pressure switch, when the pressure in the air chamber of the tire is normal, the pressure in the chamber 21 of the first housing 20 has a predetermined value, and the movable electrode 38 is in a flat state. In this state, the movable electrode 38 and the fixed electrode 30 are in contact with each other, and the electric wire 44, the fixed electrode 30, the movable electrode 38,
The ON signal is output from the wire harness because the second housing 24 and the electric wire 42 are in a conductive state. When the pressure in the tire air chamber decreases, the pressure in the chamber 21 of the first housing 20 decreases, so that the movable electrode 38 elastically deforms away from the fixed electrode 30. As a result, the movable electrode 38 and the fixed electrode 30 are brought into a non-contact state, and an off signal is output from the wire harness.

Although an example in which one side of the fixed electrode is gold-plated has been described above, both sides may be gold-plated. By gold-plating both surfaces of the movable electrode in this way, it is possible to improve the corrosion resistance, particularly the corrosion resistance of the surface of the movable electrode connected to the tire air chamber. Although the movable electrode is made of phosphor bronze, it may be made of stainless steel or copper foil having good corrosion resistance.

Next, the stopper 18 will be described in detail with reference to FIG. The stopper 18 has a flange 60A formed on the base end, a screw 60B formed on the outer peripheral surface on the distal end side, and a projection that engages with the spiral groove 11 formed on the outer peripheral surface of the protective tube on the inner peripheral surface. 60C is provided with the bolt 60 formed. The stopper 18 includes a nut 62 and a washer 64 for holding an L-shaped bracket 66 fixed to the rim of the tire wheel between the stopper 60 and the flange 60A of the bolt 60. The L-shaped bracket 66 is provided with a mounting hole 68 into which the bolt 60 is inserted, as shown in FIG.
It is communicated to the outside through 0. When attaching the protective tube to the L-shaped bracket 66 by the stopper 18, the protective tube is inserted into the mounting hole 68 through the notch 70, and the bolt 60 is inserted into the mounting hole 68 in this state. Subsequently, the nut 62 is screwed into the screw of the bolt 60 with the washer 64 interposed therebetween, whereby the L-shaped bracket 66 is sandwiched between the nut 62 and the flange 60A of the bolt 60.

FIG. 5 shows the coupling housing 16A in detail. The coupling housing 16A is provided with an insertion hole 17 that is bent at a substantially right angle at the center from one side surface toward the center and communicates with an adjacent side surface. The protective tube 12A is coated with a resin at one end and screwed into the insertion hole. The protective tube 12A penetrates through the coupling housing 16A and the protection tube 12A and drives a punch 74 into the coupling housing 16A.
Is linked to The connection between the protective tube 12B and the coupling housing 16A is also performed using a resin and a punch 75 in the same manner as described above. Note that the connection between the coupling housing 16B and the protective tube is the same as described above, and thus the description is omitted.

FIG. 6 shows a state in which the pressure sensor according to the present embodiment is attached to a plurality of rear wheels of a truck. The pressure switches 10A and 10B are directly attached by screwing or the like to air valves 77A and 77B for measuring internal pressure, which are fixed to penetrate the rim 72 and communicate with the tire air chamber, and a bracket 66 fixed to the rim 76.
A, 66B. This pressure switch
It may be attached directly to the tire air injection air valve,
Also, these air valves may be attached via a relatively short adapter. The protection tube 12D has two fixtures 1
8, and is attached to brackets 66C and 66D fixed to the rim with an appropriate tension. The transmitter 14 is mounted on a bracket 66E mounted on the rim 76. With such an attachment, the vibration of the protection tube is reduced to the level indicated by the dashed line.

FIG. 7 shows a tire pressure abnormality detecting device using the above-described pressure sensor. Pressure sensors 80A to 80D are attached to the rear wheels as shown in FIG. Antennas 82A to 82D are arranged to face the transmitters of the pressure sensors 80A to 80D, respectively, and the antennas 82A to 82D are connected to a control circuit 84 including a microcomputer. The control circuit 84 is connected to display means 86 provided on an instrument panel in the driver's seat. Further, pressure sensors 80E and 80F each composed of one pressure switch and one transmitter are attached to the front wheels, and are connected to the control circuit 84 via antennas 82E and 82F similarly to the rear wheels. 86A to 86C are connectors.

FIG. 8 shows a circuit of an antenna 82A provided on the rear wheel and a transmitter of the pressure switch 80A. The antenna 82A includes a coil L2, and the transmitter includes a coil L2.
1. Capacitor C connected in parallel to coil L1
1 and a capacitor C2. Capacitor C
2 is connected in series with the pressure switches SW1, SW2 connected in series. Pressure switches SW1, SW2
Are grounded. The other antennas and transmitters have the same configuration.

Hereinafter, the operation of the tire pressure abnormality detecting device shown in FIG. 7 will be described while describing the operation of the present embodiment. When the pressure in the tire air chamber is normal, since the pressure switches are turned on, the coil L
1. A resonance circuit of the capacitors C1 and C2 is configured. Therefore, when a pulsed current is applied to the coil L2 constituting the antenna, the resonance circuit resonates and the coil L2
1 and the coil L on the antenna side by mutual induction
2, an induced current flows. Therefore, it can be confirmed from the magnitude of the induced current that the internal pressure of the tire air chamber is normal.

When the pressure in the tire air chamber falls below a predetermined value, at least one of the contacts SW1 and SW2 of the pressure switch is turned off, so that the transmitter side becomes a resonance circuit of the coil L1 and the capacitor C1. Therefore, the time constant of the resonance changes, and the waveform of the current induced in the coil L2 changes. Therefore, an abnormality in which the pressure in the tire air chamber has decreased can be detected from the change in the waveform. The detection result of the normality or abnormality is displayed on the display device 86.

[0026]

As described above, according to the present invention, the pressure switch can be directly connected to the air valve,
Because the wires are connected by a flexible protective tube so that tension does not act on the wires, the distance between the tire air chamber and the detection position can be shortened, and the effect of tire vibration can be absorbed by the flexible protective tube. The effect of improving vibration resistance and fatigue durability can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of the present invention.

FIG. 2 is a sectional view showing details of a pressure switch of FIG. 1;

FIG. 3 is a cross-sectional view showing details of the stopper of FIG. 1;

FIG. 4 is a plan view of a bracket fixed to a tire wheel.

FIG. 5 is a detailed view of a portion of the coupling housing of FIG. 1;

FIG. 6 is a schematic diagram showing a state where the pressure sensor of the present embodiment is mounted on a tire wheel.

FIG. 7 is a schematic diagram of a tire pressure abnormality detecting device using the pressure sensor of the present embodiment.

FIG. 8 is a circuit diagram of an antenna and a transmitter.

[Explanation of symbols]

 10A, 10B Pressure switch 14 Transmitter 12A, 12B, 12C, 12D Protection tube

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Tomohito Morikawa 3-1-1 Hinodai, Hino City, Tokyo Inside Hino Motors, Ltd.

Claims (3)

(57) [Claims] At least one pressure switch connected directly to an air valve provided on a tire to detect a change in the internal pressure of a tire air chamber, and a pressure switch connected to the pressure switch via an electric wire and detecting the pressure switch A pressure sensor comprising: a transmitter for transmitting a result; and a flexible protective tube connecting the pressure switch and the transmitter and covering the electric wire so that tension is not applied to the electric wire. 2. The pressure sensor according to claim 1, wherein a stopper for attaching the pressure sensor to the tire wheel is provided on the protection tube so as to be movable in a length direction of the protection tube. 3. When the protective tubes are connected to each other, one end of each protective tube is inserted with a resin interposed between the holes in the housing in which the holes are formed, and the housing and the protective tube are penetrated. 3. The pressure sensor according to claim 1, wherein the pressure sensor is connected by driving a punch.