JPH05107141A - Pressure sensor - Google Patents

Abstract

PURPOSE:To improve the vibration resistance and fatigue strength of a sensor which detects the pressure in the air chamber of a tire. CONSTITUTION:Pressure switches are set so that they can be directly connected to a valve for measuring internal pressure installed a tire. Then pressure switches 10A and 10B are connected to a transmitter 14 through electric wires. The electric wires are covered with flexible protective tubes 12A, 12B, 12C, and 12D in a state where no tension is applied to the wires, namely, in a slackened state. Since the protective tubes can be fitted to tire wheels with appropriate tension, the protective tubes do not move by centrifugal forces, etc., and the vibration resistance and fatigue strength of this pressure sensor can be improved.

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 tire internal pressure abnormality detecting device for trucks, buses and the like.

[0002]

2. Description of the Related Art Monitoring the air pressure in a tire when the wheel is rotating or at rest is preferable for safe driving. For this reason, conventionally, there has been proposed a tire internal pressure abnormality detection device that issues an alarm when the tire air pressure falls below a predetermined value. This tire internal pressure abnormality detection device, while connecting the pressure switch and the tire air chamber attached to the substantially central portion of the tire wheel 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 this 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 tire abnormal state 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. When the pipe vibrates due to the vibration of the tire, the pipe fatigues. As a result, air leakage occurs, which causes problems in vibration resistance and fatigue durability. Further, since it is necessary to intentionally provide a play in order to cope with the vibration resistance and the fatigue durability, there is a problem that the mounting accuracy is poor.

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

[0005]

In order to achieve the above object, the present invention provides one or a plurality of pressure switches which are directly connected to an air valve provided in a tire to detect a change in internal pressure of a tire air chamber, and an electric wire. One transmitter that is connected to the pressure switch via the and that transmits the detection result of the pressure switch, and that connects the pressure switch and the transmitter and covers the electric wire so that tension does not act on the electric wire. And a flexible protective tube that does.

A stopper 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 protection tubes are connected to each other, one end of each protection tube is inserted with a resin interposed in the hole of the housing having the hole, and the housing and the protection tube are penetrated. It is effective to hit the punches and connect them. When the direction of the protective tube is changed to a substantially right-angled direction, holes that are substantially orthogonal to each other may be 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 changes in the internal pressure of the tire air chamber of the present invention can be directly connected to the air valve provided in the tire. The direct connection mentioned here includes not only the case where the pressure switch is directly attached to the air valve but also the case where the pressure switch is connected through a relatively short adapter. For this reason, the distance between the tire air chamber and the pressure switch, that is, the detection unit becomes short. The pressure switch is connected via an electric wire to a transmitter that transmits the detection result of the pressure switch. The wire is also shielded from tension by a flexible protective tube that connects the pressure switch and the transmitter. Therefore, this protection tube can be mounted accurately by mounting it on the tire wheel by applying appropriate tension, thereby minimizing the effects of tire rotation and vibration, and improving vibration resistance and fatigue durability. can do. Further, since the electric wire is covered with the protective tube so that the tension does not act, 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 breaking.

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 length direction of the protective tube, an appropriate tension is applied to the protective tube to attach it to the tire wheel. It will be easier.

When the protective tubes are connected to each other, a housing having holes formed between the protective tubes is provided, and one end of the protective tube is inserted into the hole so that the resin and the punch form a housing. If they are connected, the punch tube can prevent the protection tube from rotating, and the resin can prevent dust from entering the protection tube. 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 in detail below with reference to the drawings. In this embodiment, two pressure switches are used. As shown in FIG. 1, the pressure switch 10A is
It is connected to a joint housing 16A made of aluminum through a flexible protection tube 12A. Combined housing 1
6A is connected to a coupling housing 16B having substantially the same configuration as above via a flexible protection tube 12B having a spiral groove (see FIG. 3) formed on the outer peripheral surface. The combined housing 16B is
Protective tube 12C having the same configuration as the protective tube 12A
Is connected to a pressure switch 10B having the same structure as the pressure switch 10A. Further, the coupling housing 16B is connected to the transmitter 14 via a protection tube 12B having the same configuration as the protection tube 12B. A stopper 18 is attached to the protection tubes 12B and 12D so as to be movable in the length direction of the protection tube. The outer peripheral surfaces of the protection tubes 12A and 12C may be provided with spiral grooves as in the case of the protection tubes 12B and 12D, but the spiral grooves may not be provided because a stopper is not attached. Pressure switch 12A, 12B
The transmitter 14 and the transmitter 14 are connected to each other by an electric wire which is housed in a protective tube in a tension-free state, that is, covered with the protective tube in a loose state. Although the two pressure switches and the transmitter are connected to each other in the above description, 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 pressure switch will be described. As shown in FIG. 2, the pressure switch includes a substantially cylindrical first casing 20 having a small tip 20A and a large base 20B. The first housing 20 is made of brass. First
On the side of the base end portion 20B of the housing 20, a second base portion 24B having the same diameter as the base end portion 20B of the first housing 20 and a small diameter portion 24A having a diameter smaller than the base end portion 24B are provided. The housing 24 is arranged such that the base end portion 24B faces the base end portion 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 a phosphor bronze electrode receiver 28 having an internal thread engraved on its inner peripheral surface. This electrode receiver 2
As shown in FIG. 2, male screw 32 is engraved on the outer peripheral surface of 8, and spherical portion 31 is formed on the distal end portion and adjustment groove 36 is formed on the proximal end portion. The electrode 30 is screwed. A flange 34 is provided on the base end side of the fixed electrode 30. The fixed electrode 30 is made 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 pressure resistance and contactability. If the radius is less than 0.3 mm, it becomes too sharp, resulting in poor pressure resistance and easy breakage. If it exceeds 1.5 mm, the contact surface becomes too large, resulting in poor contact and insufficient detection capability. The spherical portion is plated with 10 μm of gold. The pitch length of the male screw 32 is 0.25 m.
m. If this male thread pitch is made as small as possible, the adjustment accuracy can be improved.

Between the base end portion 20B of the first casing 20 and the base end portion 24B of the second casing 24, a surface of the fixed electrode 30 side is made of phosphor bronze with 10 μm of gold plating. A movable electrode 38, which is a conductive elastic thin film formed of a thin film (about 0.2 mm thick), is sandwiched. This movable electrode 38 is
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 by a third casing 52 made of stainless steel to form a peripheral edge. It is sandwiched so as to be airtight, and forms a chamber 21 in the first housing 20. Further, the movable electrode 38 is sandwiched so as to be in a flat state, that is, so as not to be bent.

As described above, since the tip end of the fixed electrode and the surface of the movable electrode that contacts the fixed electrode are plated with gold, the contact / non-contact detection capability can be improved. In addition,
Instead of gold plating, another conductive material may be coated.

The electric wire 44 of the 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. The soldering is performed after inserting a driver or the like into the adjustment groove 36 and rotating 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 the flange and the wire harness is soldered to the flange, the solder does not flow into the adjustment groove and harden in the adjustment groove. The wire harness 45 penetrates the fourth housing 54 fixed to the third housing 52 with the adhesive 48 and projects.
It is fixed by the resin 46 filled in the fourth housing 54. The protruding portion of the wire harness 45 from the fourth housing 54 is sealed with packing 50 and 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 casing 20 is at 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,
Since the second housing 24 and the electric wire 42 are brought into conduction, an ON signal is output from the wire harness. 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.

In the above, the example in which one surface of the fixed electrode is gold-plated has been described, but both surfaces may be gold-plated. By thus plating the both surfaces of the movable electrode with gold, 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. Further, although the movable electrode is made of phosphor bronze, it may be made of stainless steel or foreign foil having good corrosion resistance.

Next, the stopper 18 will be described in detail with reference to FIG. This stopper 18 has a flange 60A formed at 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. The bolt 60 is formed with 60C. Further, the stopper 18 is provided with a nut 62 and a washer 64 for sandwiching the L-shaped bracket 66 fixed to the rim of the tire wheel with the flange 60A of the bolt 60. As shown in FIG. 4, the L-shaped bracket 66 is provided with a mounting hole 68 into which the bolt 60 is inserted, and the mounting hole 68 has a cutout 7.
It is connected to the outside through 0. When the protection tube is attached to the L-shaped bracket 66 by the stopper 18, the protection tube is inserted into the attachment hole 68 through the notch 70, and in this state, the bolt 60 is inserted into the attachment hole 68. Then, the L-shaped bracket 66 is sandwiched between the nut 62 and the flange 60A of the bolt 60 by screwing the nut 62 into the screw of the bolt 60 with the washer 64 interposed.

FIG. 5 shows in detail the portion of the coupling housing 16A. The coupling housing 16A has an insertion hole 17 which is bent from one side surface toward the center and bent at a substantially right angle at the center to communicate with the adjacent side surface. A resin is applied to one end of the protective tube 12A and is screwed into this insertion hole, and the punch 74 is driven through the combined casing 16A and the protective tube 12A to drive the combined casing 16A.
Is connected with. Further, the connection between the protective tube 12B and the coupling housing 16A is also made by using the resin and the punch 75 as in the above. The connection between the coupling housing 16B and the protective tube is also similar to the above, and the description thereof is omitted.

FIG. 6 shows a state in which the pressure sensor of this embodiment is attached to the compound wheels of the rear wheels of the 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 that are fixed so as to penetrate through the rim 72 and communicate with the tire air chamber, and the bracket 66 fixed to the rim 76.
It is attached to A and 66B. This pressure switch
It may be attached directly to the air valve for inflating the tire,
It may also be attached to these air valves via a relatively short adapter. Protective tube 12D has two fittings 1
It is attached to brackets 66C and 66D which are fixed to the rim by being given a proper tension by means of 8. The transmitter 14 is attached to a bracket 66E attached to the rim 76. With such an attachment, the vibration of the protective tube becomes only as shown by the alternate long and short dash line.

FIG. 7 shows a tire air pressure abnormality detecting device using the pressure sensor as described above. As shown in FIG. 6, pressure sensors 80A to 80D are attached to the rear double wheels. Antennas 82A to 82D are arranged so as to face the transmitters of the pressure sensors 80A to 80D, and the antennas 82A to 82D are connected to a control circuit 84 including a microcomputer. The control circuit 84 is also connected to a display means 86 provided on the instrument panel of the driver's seat. Further, pressure sensors 80E and 80F composed of one pressure switch and one transmitter are attached to the front wheel, and are connected to the control circuit 84 via the antennas 82E and 82F, similarly to the rear wheel. Note that 86A to 86C are connectors.

FIG. 8 shows a circuit of the antenna 82A provided on the rear wheel and the transmitter of the pressure switch 80A. The antenna 82A is composed of a coil L2, and the transmitter is a coil L2.
1, a capacitor C connected in parallel with the coil L1
1 and a capacitor C2. Condenser C
2 is connected in series with pressure switches SW1 and SW2 connected in series. In addition, pressure switches SW1 and SW2
The connection line that connects is grounded. The other antennas and transmitters have the same configuration.

The operation of the tire pressure abnormality detecting device of FIG. 7 will be described below while explaining the operation of the present embodiment. When the pressure in the tire air chamber is normal, each pressure switch is on, so 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 forming the antenna, the resonance circuit resonates and the coil L2 resonates.
A current flows through the coil 1 and the coil L on the antenna side is induced by mutual induction.
An induced current flows through 2. Therefore, it can be confirmed from the magnitude of this induced current that the internal pressure of the tire air chamber is normal.

When the pressure in the tire air chamber decreases below a predetermined value, at least one of the contact points 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 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 normal and abnormal detection results are 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, and
Since the flexible protection tube is connected so that tension does not act on the electric wire, 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 protection tube. Further, it is possible to obtain the effect that the vibration resistance and the fatigue durability can be improved.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing details of the pressure switch of FIG.

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

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

5 is a detailed view of a portion of the combined housing of FIG.

FIG. 6 is a schematic view showing a state in which the pressure sensor of the present embodiment is attached to 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 Protective tube

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yuzo Katsu 3-1-1 Hinodai, Hino-shi, Tokyo Inside Hino Motor Co., Ltd. (72) Inventor Tomohito Morikawa 3-1 Hinodai, Hino-shi, Tokyo -1 Inside Hino Motor Co., Ltd.

Claims (3)

[Claims] 1. One or a plurality of pressure switches that are directly connected to an air valve provided in a tire to detect a change in internal pressure of a tire air chamber, and a pressure switch that is connected to the pressure switch via an electric wire and is also detected. 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 the length direction of the protection tube. 3. When the protection tubes are connected to each other, one end of each protection tube is inserted through a resin in a hole of a housing having a hole, and the housing and the protection tube are penetrated. 3. The pressure sensor according to claim 1 or 2, wherein punches are driven and connected as described above.