JP2005164356A - Tyre pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tyre pressure sensor equipped with a loop antenna of a length suitable for transmission/reception of radio wave. <P>SOLUTION: This tyre pressure sensor 2 is equipped at least with a pressure sensor 21 for detecting a tyre pressure of a vehicle and a transmission means for transmitting a detection result detected by the pressure sensor 21. The pressure sensor 2 is housed in an enclosure 27 placed in a middle part of a wheel W for holding a tyre while the transmission means comprises a loop antenna (sensor-side antenna 25) internally mounted in the enclosure 27. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a tire air pressure sensor provided with a sensor side transmitting means for transmitting vehicle tire air pressure information detected by a pressure sensor to a vehicle body side antenna.

Conventionally, as a system for detecting a decrease in tire air pressure, for example, in order to make the driver recognize a decrease in tire air pressure, information on the decrease in tire air pressure detected by pressure sensors respectively installed on four wheels is used as a sensor. 2. Description of the Related Art A wireless (direct) tire pressure monitoring device is known that transmits a radio wave from a side antenna to a vehicle body side antenna to monitor tire pressure.
The pressure sensor used in such a tire pressure monitoring device is installed integrally with the tire valve on the outer or inner surface of the wheel rim. Since the pressure sensor is a wireless system, a sensor-side antenna for transmitting or transmitting / receiving radio waves is incorporated.

  As a sensor side antenna, in general, a coil provided in a screw attached to a tire valve is used as a sensor side antenna (Patent Document 1), and a tire valve itself is used as a sensor side antenna (Patent Document 2). 2. Description of the Related Art There are known a sensor-side antenna using an electronic board installed in a pressure sensor (Patent Document 2) and a casing antenna insert-molded on a pressure sensor lid (Patent Document 2).

The length of the sensor-side antenna is preferably set to a value that is an integral multiple of the wavelength (λ) or a value obtained by dividing the wavelength (λ) by a multiple of 2, in accordance with the wavelength. it can. In the tire pressure monitoring device, a radio wave having a frequency of 300 to 400 MHZ and a wavelength (λ) of about 100 cm is generally used. Therefore, the length of the sensor-side antenna is preferably 50 cm (λ / 2), 25 cm (λ / 4),.
Japanese Patent Laid-Open No. 11-180117 (paragraph numbers 0009 and 0010, FIGS. 1 and 2) JP 2003-165315 A (paragraph numbers 0035 to 0039, FIGS. 1 to 3)

However, the conventional sensor-side antenna described in Patent Document 1 is sufficiently long because the size of the tire air pressure sensor is limited by being installed in the tire air pressure sensor integrated with the valve installed on the rim. I could not secure it.
For this reason, many conventional sensor-side antennas have a length of about 12.5 cm (λ / 8) to about 6.25 cm (λ / 16), and radio wave transmission / reception sensitivity is poor.

In order to solve this problem, in Patent Document 2, in order to lengthen the sensor-side antenna, an antenna made of a tire valve itself, an antenna made of an electronic board, a casing antenna insert-molded on the lid of the tire pressure sensor, Are connected to form a sensor-side antenna.
However, even if these three types of antennas are connected and lengthened, the length of the sensor-side antenna can only be about 1/4 of the wavelength (about 25 cm).
In such a tire pressure sensor in Patent Document 2, since the antenna is installed on the tire valve, the electronic substrate, and the lid portion, the number of parts and the number of assembling steps are increased, and the internal structure of the tire pressure sensor is increased. There is a problem of increasing complexity.

  The wheel is made of steel or aluminum alloy, and the tire has a steel wire. The tire pressure sensor is arranged on the rim of the wheel, so that when the vehicle travels, the wheel arranged on the outer periphery of the tire pressure sensor and the steel wire of the tire generate magnetism. Radio waves transmitted and received from the air pressure sensor were sometimes blocked.

In addition, there is a tire pressure sensor provided with a sensor-side antenna, and a cord-shaped sensor-side antenna is drawn outside the tire pressure sensor. In this case, even if the sensor-side antenna can secure a desired length, there is a problem in that the cord-shaped sensor-side antenna cannot be firmly fixed to the wheel or the like depending on the shape of the wheel.
In a tire pressure sensor that uses such a cord-shaped sensor-side antenna or valve as the sensor-side antenna, the sensor-side antenna is placed in a state where it is exposed from the sensor body. As a result, the transmission accuracy decreases.

Conventionally, as a general means for solving this problem and reliably transmitting a weak transmission radio wave, the transmission power of the tire pressure sensor is increased.
However, when the transmission power of the tire pressure sensor is increased, the battery consumption and the battery replacement period are shortened. And since the battery was built in the tire pressure sensor, there was a problem that it took time to replace the battery.
In the radio wave law, wireless output is restricted, and there is a limit to improve the transmission accuracy by increasing the transmission power of the tire pressure sensor.

  Accordingly, the present invention has been made to solve the problems of the prior art, and an object of the present invention is to provide a tire pressure sensor including a loop antenna having a length suitable for transmission / reception of radio waves. Is an issue.

  In order to solve the above-described problem, the tire pressure sensor according to claim 1 includes at least a pressure sensor that detects a tire pressure of a vehicle and a transmission unit that transmits a detection result detected by the pressure sensor. The tire pressure sensor is housed in a housing installed at a central portion of a wheel that holds the tire, and the transmission means includes a loop antenna built in the housing. To do.

  According to the first aspect of the present invention, the tire air sensor can be widened by installing the tire air sensor in the center portion of the wheel. The size can be increased compared to the case. When the transmission means provided in the casing has a loop antenna, the length of the loop antenna can be set to a desired length, and the transmission / reception sensitivity of radio waves can be improved. Further, the tire air pressure sensor is installed at the center of the wheel, so that the loop antenna is disposed at a position away from the tire, so that it can be prevented from being affected by the magnetism of the steel wire of the steel tire. .

  The tire air pressure sensor according to claim 2 is the tire air pressure sensor according to claim 1, wherein the loop antenna is disposed closer to an outer peripheral portion of the housing and closer to an outer side of the vehicle. It is characterized by.

According to the second aspect of the present invention, the loop antenna can be arranged closer to the outer periphery of the casing, thereby increasing the length of the loop antenna and improving the transmission / reception sensitivity of radio waves.
In addition, since the loop antenna is arranged closer to the vehicle exterior of the housing, the loop antenna is disposed at a position closer to the vehicle exterior of the wheel. Sensitivity can be improved. As a result, the loop antenna can be used as an antenna for a non-stop automatic fee payment system (ETC) installed outside the vehicle other than the tire pressure monitoring device, an antenna for communication with other vehicles, and the like.

The casing of the tire pressure sensor is preferably formed in a cylindrical shape.
The casing can be formed in a cylindrical shape by being installed at the center of the wheel. The casing is formed into a cylindrical shape, so that an antenna in which the loop antenna is circularly wired along the cylindrical portion of the casing or the loop antenna is matched with the wavelength (λ) to λ / of the wavelength (λ). The antenna can be formed into a length such as 2 or λ / 4 and wound in a spiral shape a plurality of times so as to have a good sensitivity.

According to the tire pressure sensor according to the present invention, the tire air sensor is accommodated in the casing installed in the center of the wheel, and the transmission means has a loop antenna built in the casing, thereby occupying the casing. Since the space can be increased and the size can be increased, the length of the loop antenna can be appropriately increased to improve radio wave transmission / reception sensitivity. Further, the tire air pressure sensor is installed at the center of the wheel, so that the loop antenna is disposed at a position away from the tire, so that it can be prevented from being affected by the magnetism of the steel wire of the steel tire. .
In addition, the loop antenna is disposed near the outer periphery of the casing and near the outside of the vehicle, so that there is no obstacle to radio waves around the casing, and radio wave transmission / reception sensitivity can be improved. Therefore, it can be used as an antenna for a non-stop automatic fee payment system (ETC) installed outside the vehicle other than the tire pressure monitoring device, an antenna for communication with other vehicles, and the like.

  The tire pressure sensor according to the embodiment of the present invention can be applied to all vehicles equipped with tires such as passenger cars and work vehicles. Hereinafter, a four-wheel passenger car will be described as an example. In addition, the kind and shape of the tire used for this tire pressure monitoring apparatus are not specifically limited, It can apply to all the tires.

[First Embodiment]
First, with reference to FIGS. 1-4, the tire pressure sensor which concerns on 1st Embodiment of this invention is demonstrated.
FIG. 1 is a block diagram showing a configuration of a passenger car provided with a tire pressure monitoring device according to a first embodiment of the present invention. FIG. 2 is a diagram showing the passenger car equipped with the tire pressure monitoring device according to the first embodiment of the present invention, and is a schematic diagram showing a state when radio waves are transmitted to the vehicle body side antenna. FIG. 3 is a diagram showing a wheel equipped with the tire air pressure sensor according to the first embodiment of the present invention, and is an exploded perspective view showing an attachment state of the air pressure sensor unit. FIG. 4 is an exploded perspective view of the tire pressure sensor according to the first embodiment of the present invention. FIG. 5 is a perspective view showing a layout in the housing, showing the tire pressure sensor according to the first embodiment of the present invention.

First, the tire pressure monitoring apparatus 1 will be described with reference to FIG.
The tire pressure monitoring device 1 shown in FIG. 1 detects the air pressure of each tire T by the air pressure sensor unit 2 and controls the air pressure of the tire T by transmitting and receiving radio signals by the vehicle body side antenna 4 provided on the side mirror 3. In addition, the air pressure information is displayed on the display 5 and monitored.
The tire pressure monitoring device 1 is provided in the air pressure sensor unit 2 that detects the air pressure of the tire T and transmits the detection result (air pressure signal), the side mirrors 3 on the left and right of the vehicle body C, and the like. Vehicle-side antenna 4 that transmits and receives radio waves, a vehicle-side radio transmitter / receiver 6 provided on a side mirror 3 or an instrument panel (not shown), a display 5, and an in-vehicle ECU (Electronic Control Unit) 7 and an in-vehicle power supply 8.

As shown in FIG. 1, among the components of the tire pressure monitoring device 1, the vehicle body C includes a vehicle body side antenna 4, a vehicle body side radio wave transmitter / receiver 6, an in-vehicle ECU 7, a display device 5, and an in-vehicle power source 8. Is provided. For example, four tires T are mounted on the wheel W of the vehicle body C.
As shown in FIG. 3, the wheel W is provided with a tire valve V for injecting air into the tire T and a wheel nut N for fixing the wheel W to an axle (not shown). The shape of the wheel W is not particularly limited as long as the tire T, the tire valve V, and the wheel nut N are attached.

  As shown in FIGS. 1 and 2, the side mirror 3 is a door mirror or a fender mirror disposed on each of the left and right side surfaces of the vehicle body C, and transmits / receives radio waves to / from the air pressure sensor unit 2 therein. A vehicle body side antenna 4 is provided. The housing 3a of the side mirror 3 is made of synthetic resin so that the radio wave transmitted from the sensor antenna 25 is not blocked.

The vehicle body side antenna 4 is an antenna for transmitting and receiving radio waves from the air pressure sensor unit 2, and is formed by, for example, a conductive wire or a conductive foil provided in the side mirror 3. The vehicle body side antenna 4 is wired along the longitudinal direction of the housing 3a at a position near the lower end or the bottom surface portion in the housing 3a, and is electrically connected to the vehicle body side radio wave transmitter / receiver 6. The length of the vehicle body side antenna 4 is preferably set to a length according to the wavelength of the radio wave transmitted from the sensor side antenna 25 in order to improve the transmission / reception sensitivity. For example, the length of the vehicle body side antenna 4 is ¼ or ½ of the wavelength of the radio wave.
The vehicle body side antenna 4 may be an antenna installed inside the vehicle body C, an antenna installed in a wheel house, an antenna installed in a door handle, or the like. The vehicle body side antenna 4 may be a loop antenna.

  A vehicle body side radio wave transmitter / receiver 6 shown in FIG. 1 is a device for transmitting and receiving radio waves from the vehicle body side antenna 4. The vehicle-side radio wave transmitter / receiver 6 includes a transmission circuit (not shown) that converts a signal from the vehicle-mounted ECU 7 into a radio wave so that it can be transmitted from the vehicle-side antenna 4 to the air pressure sensor unit 2, and the air pressure received by the vehicle-side antenna 4 It is comprised from the receiving circuit (not shown) which converts the electromagnetic wave from the sensor unit 2 into an electrical signal. The vehicle body side radio wave transmitter / receiver 6 is electrically connected to the in-vehicle ECU 7.

  The indicator 5 is a monitor device configured to display and alarm the air pressure information of all four tires T detected by the pressure sensor 21, and is disposed on, for example, an instrument panel. The display 5 is electrically connected to the in-vehicle ECU 7.

  The in-vehicle ECU 7 includes an amplifier circuit that amplifies signals received by the vehicle body side antenna 4, a storage circuit that stores data such as standard air pressure values of the tire T under various driving conditions and disturbance conditions, and the data and pressure sensor A comparison circuit that compares the air pressure detected at 21, a determination circuit that determines whether or not to operate the display 5 based on a signal from the comparison circuit, and a wakeup signal that activates and deactivates the display 5 and the air pressure sensor unit 2 -It consists of a microcomputer equipped with a transmission circuit for transmitting a sleep signal. The in-vehicle ECU 7 is electrically connected to an in-vehicle power source 8 composed of a battery.

Next, the air pressure sensor unit 2 will be described with reference to FIGS.
As shown in FIG. 2, the air pressure sensor unit 2 detects the air pressure of each tire T and transmits air pressure information to the vehicle body side antenna 4, and receives the radio wave transmitted from the vehicle body side antenna 4 to receive the tire T It is a device that adjusts the air pressure. The air pressure sensor unit 2 is screwed to the center portion of the wheel W provided on all the tires T of the front wheel and the rear wheel via a stay 28, respectively.
As shown in FIG. 4, the air pressure sensor unit 2 includes a temperature sensor (not shown) for detecting the temperature of air in the tire T and a pressure sensor 21 having an actuator portion 21 a for adjusting the air pressure in the tire T. An air hose 22 connected to the pressure sensor 21, a sensor ECU (Electronic Control Unit) 23, a sensor-side radio wave transmitter / receiver 24, a sensor-side antenna 25, and the sensor-side antenna 25 and the sensor ECU 23 and A control board 26 on which the sensor-side radio wave transmitter / receiver 24 is mounted and a battery BT are mainly provided.
4 and 5, among these, the control board 26, the pressure sensor 21 and the battery BT are built in the housing 27, and are connected to the wheel W (see FIG. 3) via the stay 28. Attached to the center.
The air pressure sensor unit 2 corresponds to a “tire air pressure sensor” recited in the claims, and the sensor ECU 23, the sensor side radio wave transmitter / receiver 24, and the sensor side antenna 25 correspond to “sensor side transmitting means”.

  In addition, the air pressure sensor unit 2 may not include the actuator portion 21a including a motor or the like as long as the air pressure sensor unit 2 includes the pressure sensor 21 that detects the air pressure of the tire T. The sensor-side radio wave transmitter / receiver 24 may be a dedicated transmitter that transmits information such as the pressure of the tire T.

Next, the housing 27 will be described with reference to FIG.
As shown in FIG. 4, the casing 27 is formed by insert-molding the sensor-side antenna 25 with a reinforced resin such as an ABS resin or a modified PPE resin. The casing 27 includes a bottomed cylindrical storage case main body 27a having an open top, and a lid 27b that closes the opening of the storage case main body 27a. The casing 27 is made of a bottomed cylindrical body having a diameter of about 80 to 100 mm and a thickness of about 20 to 40 mm, for example. An air hole 27c and a screw hole 27e are formed on the bottom surface of the storage case main body 27a. Further, an attachment screw 27d is provided through the center of the lid 27b so that the head of the attachment screw 27d can be gripped and easily fitted into the storage case main body 27a.
A bracket 29 is fixed by screws S1 in the storage case main body 27a (see FIG. 5), and a screw hole 29a formed in the bracket 29 and a screw portion of an attachment screw 27d of the lid 27b are screwed together. Thus, the storage case body 27a and the lid body 27b are pressure-bonded. The storage case main body 27a may be provided with a watertight packing between the storage case main body 27a and the lid body 27b in order to improve water resistance.

Next, the sensor-side antenna 25 will be described with reference to FIG.
The sensor side antenna 25 is an antenna for transmitting and receiving the air pressure of the tire T detected by the pressure sensor 21 to and from the vehicle body side antenna 4 (see FIG. 1) via the sensor ECU 23 and the sensor side radio wave transmitter / receiver 24. is there. The sensor-side antenna 25 includes, for example, a loop antenna formed by a conductive wire or conductive foil inserted in the vicinity of the opening end side of the housing 27.
The sensor-side antenna 25 is inserted into the opening end side of the housing 27, and the housing 27 is installed on the vehicle outer side of the wheel W via the stay 28 as shown in FIG. It is arranged on the outermost side.
As shown in FIG. 4, the sensor-side antenna 25 is arranged in a ring shape along the side surface of the cylindrical casing 27 and is connected to a cable 26 a connected to the control board 26 at both ends. 25a, 25b.
The sensor side antenna 25 is formed with a length adjusting portion 25c for adjusting the effective length of the sensor side antenna 25 in the vicinity of the terminal 25a. The length adjusting unit 25c is composed of a loading coil formed by winding a conductive wire constituting the sensor-side antenna 25 in a coil shape. The sensor-side antenna 25 extends and contracts its length adjusting unit 25c to finely adjust the entire length (effective length) of the sensor-side antenna 25 according to the wavelength of the radio wave, thereby improving the sensitivity of radio wave transmission / reception. Can be.
The length (effective length) of the sensor-side antenna 25 is preferably set to a length that matches the wavelength of the transmitted / received radio wave in order to improve the transmission / reception sensitivity. For example, the length (effective length) of the sensor side antenna 25 is set to 1/4 or 1/2 of the wavelength of the radio wave.
The sensor-side antenna 25 corresponds to a “loop antenna” described in the claims.

In general, radio waves having a frequency of 300 to 400 MHZ are used for transmission and reception between the sensor-side antenna 25 and the vehicle-body-side antenna 4 of the tire pressure monitoring device 1, and the wavelength λ is about 1 m. For example, if the diameter of the housing 27 is about 80 mm, the outer circumference of the housing 27 is about 250 mm. Then, by arranging the sensor-side antenna 25 in the vicinity of the outer peripheral surface of the casing 27, the sensor-side antenna 25 has a length of about 250 mm and has a wavelength 1 / λ of a wavelength (λ) with good radio wave transmission / reception sensitivity. Can be 4 lengths.
Terminals 25a and 25b of the sensor-side antenna 25 are connected to a sensor-side radio wave transmitter / receiver 24 provided on the control board 26 by a cable 26a.

FIG. 6 is a view showing a tire air pressure sensor according to another embodiment of the present invention, and is a perspective view showing an attachment state of an air pressure sensor unit having a sensor-side antenna wound a plurality of times.
Note that the length of the sensor-side antenna 25 can be adjusted by the length adjusting unit 25c. However, as shown in FIG. The length can be adjusted. As described above, the sensor-side antenna 25 has a length of about 250 mm and a quarter of the wavelength when it is wound around the casing 27 as described above. When wound, the length is about 500 mm, which is half the wavelength. As described above, the sensor-side antenna 25 is provided in the casing 27 in a state of being wound a plurality of times, thereby improving the radio wave transmission / reception sensitivity.

Next, each component of the air pressure sensor unit 2 provided in the housing 27 will be described with reference to FIG.
The control board 26 is composed of a printed board in which an electronic element 26b such as a CPU (Central Processing Unit) or a resistance element (not shown) and a cable 26a whose core wire is coated with an insulating film are soldered. The control board 26 includes a sensor side radio wave transmitter / receiver 24 that receives a control signal for driving the pressure sensor 21 and a sensor ECU 23 for controlling the pressure sensor 21.

  The pressure sensor 21 includes a detector function for detecting the air pressure in the tire T, and an actuator unit 21a that operates the valve 22a when the tire T air pressure rises above a reference value to reduce the air pressure in the tire T. It is a device that has. The actuator portion 21a is configured to convert a rotational force from a motor (not shown) into a force in the axial direction of the rotary shaft 21b, and to move the tip 21c back and forth in the axial direction of the rotary shaft 21b every predetermined stroke. Has been. The actuator portion 21a projects the tip 21c by a predetermined stroke, thereby pressing the valve pin 22b of the valve 22a provided on the air hose 22 to release the air in the tire T by a predetermined amount so as to adjust the air pressure. It is configured. The pressure sensor 21 is electrically connected to the sensor ECU 23.

The air hose 22 shown in FIGS. 2 and 3 is a hollow hose for guiding the air in the tire T to the housing 27 at the center of the wheel W. The air hose 22 is formed of a rigid member in order to suppress bending due to centrifugal force or vertical vibration while the vehicle is running. One end of the air hose 22 is connected to a tire valve V provided on the wheel W in a state where the valve pin 22b is constantly pressed, and the other end is fixed to the outer peripheral surface of the storage case body 27a and provided on the wheel W. It is connected to the actuator portion 21a via a valve 22a having the same structure as the tire valve V (see FIG. 4).
In other words, the air in the tire T is compressed through the inside of the casing 27 by the tip 21c of the actuator portion 21a pressing the valve pin 22b of the valve 22a provided on the other end side of the air hose 22 shown in FIG. It is a mechanism that is discharged to the outside from the hole 27c.

  In the present embodiment, the air hose 22 has a structure having the valve 22a and the valve pin 22b on the actuator portion 21a side, but the present invention is not particularly limited, and is directly fitted to a tire valve V provided on the tire T. It can also be set as the structure which has a valve pin to do.

The battery BT supplies power to the pressure sensor 21, the actuator unit 21a, the sensor ECU 23, and the sensor side radio wave transmitter / receiver 24. The battery BT is composed of, for example, a plurality of single 5 type dry batteries. The batteries are arranged at equal intervals along the inner peripheral surface of the storage case body 27a. By doing in this way, while being attached to the wheel W and rotating with the wheel W, the rotation balance improves and the storage efficiency can be improved (see FIG. 3). The battery BT is electrically connected to the sensor ECU 23.
When the air pressure sensor unit 2 does not include the actuator unit 21a, the battery BT may be a small button type battery such as a lithium battery, a coin type battery, or a gum type (flat plate) battery.

  The sensor ECU 23 shown in FIG. 4 starts and pauses the air pressure sensor unit 2 in response to an electric circuit that amplifies and encodes the signal of the pressure sensor 21 and a wake-up signal and a sleep signal from the in-vehicle ECU 7 (see FIG. 1). The apparatus includes a power supply circuit, a drive circuit that activates and deactivates the pressure sensor 21, and includes, for example, a microcomputer. The sensor ECU 23 is installed on the control board 26 and is electrically connected to the sensor-side radio wave transmitter / receiver 24.

The sensor-side radio wave transmitter / receiver 24 is a device for transmitting and receiving radio waves from the sensor-side antenna 25, and a transmission circuit (not shown) that converts an air pressure signal from the sensor ECU 23 into radio waves so that it can be transmitted from the sensor-side antenna 25. ) And a receiving circuit (not shown) that converts the radio wave received from the vehicle-mounted ECU 7 received by the sensor-side antenna 25 into an electric signal.
The sensor-side radio wave transmitter / receiver 24 transmits / receives a control signal for activating / deactivating the pressure sensor 21 and the actuator unit 21a and an air pressure signal of the pressure sensor 21 to the vehicle-mounted ECU 7 (see FIG. 1) via the sensor-side antenna 25. Has the function of a transceiver. The sensor side radio wave transmitter / receiver 24 is electrically connected to the in-vehicle ECU 7 (see FIG. 1).

Next, the arrangement of the components built in the housing 27 will be described.
As shown in FIG. 4, the pressure sensor 21 is disposed at the center of the bottom of the storage case body 27a, and the battery BT is disposed along the inner peripheral surface of the storage case body 27a. The control board 26 is arranged above the pressure sensor 21 and fixed to the bracket 29 with screws S2 so as not to move inside the storage case body 27a.
By arranging in this way, the balance of the center of gravity of the entire air pressure sensor unit 2 is improved, and further, the rotational balance when the wheel is mounted with the wheel W and rotated together with the wheel W is improved.

As shown in FIG. 3, the casing 27 is attached to the center of the wheel W by a stay 28 for fixing the air pressure sensor unit 2 to the wheel W. At this time, a wheel nut N having a screw hole N1 at the head is screwed to five wheel bolts (not shown) protruding from the wheel W. On the other hand, a screw S3 is screwed into a screw hole 27e provided in the lower surface of the storage case main body 27a through a first through hole 28a formed in the stay 28, and the housing 27 is fixed to the stay 28. The stay 28 is screwed into the screw hole N1 of the wheel nut N by a bolt B1 that passes through the second through hole 28b of the stay 28 and is attached to the center of the wheel W.
As a result, the air pressure sensor unit 2 can handle various types of wheels W with different positions of the wheel nuts N by simply replacing the stays 28. Therefore, the air pressure sensor unit 2 has versatility and can handle wheels W of any shape. Furthermore, it is not necessary to remove the wheel W or the tire T for attachment to the wheel W, and the attachment operation can be easily performed.

  And from the side surface of the housing | casing 27, it arrange | positions in the state with which the air hose 22 was pulled out. As shown in FIG. 3, the air hose 22 has one end connected to the center portion side of the wheel W and the other end connected to a tire valve V installed on the outer peripheral side of the wheel W, so that the air hose 22 is slightly loosened. Placed in a state.

Next, the operation of the tire pressure monitoring device 1 will be described with reference to FIG. 1, FIG. 2, and FIG.
For example, the tire pressure monitoring device 1 is activated when the driver turns on an ignition switch (not shown).
That is, when the ignition switch is turned on, electric power is supplied to the in-vehicle ECU 7 shown in FIG. The in-vehicle ECU 7 sends an activation signal to the display 5 and activates it, and the wake-up signal from the in-vehicle ECU 7 is transmitted from the vehicle body side radio wave transmitter / receiver 6 and the vehicle body side antenna 4 to the sensor side antenna 25 and the sensor side radio wave shown in FIG. The air pressure sensor unit 2 is activated by being sent to the sensor ECU 23 via the transceiver 24.

As shown in FIG. 1, since the vehicle body side antenna 4 is provided on the side mirror 3 protruding from the vehicle body C, there is no obstacle between the side mirror 3 and the wheel W. The radio waves transmitted from the sensor W are linearly delivered toward the sensor-side antenna 25 installed on the wheel W.
The sensor-side antenna 25 is disposed at a position where the side mirror 3 can be directly viewed from the casing 27 by being provided on the casing 27 disposed outside the vehicle body C from the wheel W.
Furthermore, by installing the casing 27 at the center of the wheel W, the degree of freedom with respect to the size can be increased and the size can be increased.
As a result, the sensor-side antenna 25 can be provided in an annular shape in the vicinity of the outer peripheral surface of the relatively large casing 27, so that the sensor-side antenna 25 can be made longer to The radio waves between can be transmitted and received with high sensitivity.

The in-vehicle ECU 7 transmits a data transmission request signal to the air pressure sensor unit 2 via the vehicle body side antenna 4. In the air pressure sensor unit 2, the sensor ECU 23 activates the pressure sensor 21 to detect the air pressure of the tire T. The air pressure signal of the tire T detected by the pressure sensor 21 is transmitted from the sensor-side antenna 25 via the sensor ECU 23 and the sensor-side radio wave transmitter / receiver 24.
The air pressure signal is received by the vehicle body side antenna 4 installed on the side mirror 3 (see FIG. 2), and is taken into the in-vehicle ECU 7 through the vehicle body side radio wave transmitter / receiver 6. At this time, as shown in FIG. 1, the air pressure signals of the front and rear tires T on the right side of the vehicle body C are received by the vehicle body side antenna 4 provided on the right side mirror 3. On the other hand, the air pressure signals of the front and rear tires T on the left side of the vehicle body C are received by the vehicle body side antenna 4 provided on the left side mirror 3.
The vehicle body side antenna 4 is provided at a position where the side mirror 3 protrudes from the left and right of the vehicle body C made of a metal body so that the tires T arranged before and after the vehicle body C can be directly viewed. Therefore, the radio wave transmitted from the air pressure sensor unit 2 is transmitted directly to the vehicle body side antenna 4, so that it can be reliably received by the vehicle body side antenna 4.
Thus, transmission / reception between the vehicle body side antenna 4 and the sensor side antenna 25 can be performed accurately from either side.

Next, the in-vehicle ECU 7 compares whether the air pressure of the tire T is within the reference value.
The in-vehicle ECU 7 shown in FIG. 1 compares the reference air pressure of the tire T of the vehicle stored in a storage circuit (not shown) with the detected air pressure of each tire T. If the air pressure is within the reference value, the display 5 indicates that the air pressure of the tire T is within the reference value. The display of the air pressure of the display 5 at this time is displayed well because the radio waves of the vehicle body side antenna 4 and the sensor side antenna 25 can communicate with high sensitivity.

When the detected air pressure is outside the reference value, an alarm is displayed on the display 5 that the air pressure of the tire T is outside the reference value.
When the detected air pressure is outside the reference value and is higher than the reference value, an image is displayed on the display 5 that the air pressure of the tire T is high, and when it is lower than the reference value, the air pressure of the tire T is low. As a result, the driver can know the air pressure state of each tire T with the display 5 and take treatment.

While the vehicle is running, the air pressure signal of the tire T is taken in every short predetermined sampling interval.
When the air pressure of the tire T rises due to frictional heat or the outside air temperature and exceeds a predetermined air pressure value, the in-vehicle ECU 7 sends the actuator unit 21a shown in FIG. 4 from the vehicle body side antenna 4 via the vehicle body side radio wave transmitter / receiver 6. A control signal for driving is transmitted. Then, this control signal is sent to the actuator unit 21a via the sensor side antenna 25, the sensor side radio wave transmitter / receiver 24, and the sensor ECU 23.
The radio wave transmitted at this time can be transmitted directly toward the sensor side antenna 25 because the vehicle body side antenna 4 shown in FIG.
On the other hand, the sensor-side antenna 25 on the receiving side is disposed outside the center portion of the wheel W and disposed outside the vehicle body C formed of metal, so that it is not affected by the magnetic barrier. And reception sensitivity is good.

The actuator portion 21a shown in FIG. 4 has its tip 21c moved forward based on the control signal, and moved backward after a predetermined time, so that the valve 22a provided at the center of the wheel W (see FIG. 1) The valve pin 22a is pressed with a predetermined stroke for a predetermined time, and a predetermined amount of air is discharged from the tire T (see FIG. 1) into the housing 27, via the air hole 27c and the air hole 28c formed in the stay 28. To release to the outside. Thereby, the air pressure in the tire T shown in FIG. 1 can be removed and the air pressure can be set to the reference value while the vehicle is running.
On the other hand, when the air pressure of the tire T becomes the reference value, the display 5 indicates that the air pressure of the tire T has reached the reference value.

The display unit 5 updates and displays the tire T air pressure information at predetermined time intervals by taking in the tire T air pressure signal that is performed at short predetermined sampling intervals.
And the indicator 5 and the tire pressure monitoring apparatus 1 are turned off in conjunction with it by turning off an ignition switch (not shown).

  As described above, the tire pressure monitoring device 1 is configured such that the casing 27 is formed in a cylindrical shape by installing the air pressure sensor unit 2 at the center of the wheel W as shown in FIG. The occupied space of 27 can be widened. For this reason, the housing | casing 27 can be enlarged compared with the housing | casing 27 of the conventional tire pressure sensor. Therefore, the sensor-side antenna 25 can be a loop antenna provided in a ring shape on the cylindrical casing 27, and the desired length of the sensor-side antenna 25 can be used to improve radio wave transmission / reception sensitivity. Can do.

[Second Embodiment]
Next, a tire pressure sensor according to a second embodiment of the present invention will be described with reference to FIGS. The same components as those described in the second embodiment are denoted by the same reference numerals and description thereof is omitted.
In the second embodiment of the present invention, the sensor-side antenna is provided separately from the housing by providing a support member made of a flexible substrate, a flat cable, a spiral cable, etc., and the tire air detected by the air pressure sensor unit is provided. It is comprised from the tire pressure sensor which introduce | transduces from the hollow part integrally formed in the wheel, and detects an air pressure.

  FIG. 7 is a perspective view showing a tire air pressure sensor according to the second embodiment of the present invention, showing a state in which the center valve unit is attached. 8 is an enlarged cross-sectional view in the XX direction of FIG. FIG. 9 is an enlarged view of a portion A in FIG. FIG. 10 is a diagram showing a tire pressure sensor according to the second embodiment of the present invention, and is an exploded perspective view of the center valve unit.

First, the wheel W1 will be described with reference to FIGS.
A wheel W1 shown in FIG. 7 is for attaching, for example, four tires T installed on the front, rear, left and right of the vehicle body C (see FIG. 1), and is formed of a cast product made of aluminum alloy or the like. The wheel W1 includes a rim W1a on which the tire T is mounted, and a wheel disc W1b for attachment to an axle (not shown).
As shown in FIG. 8, the wheel disc W1b is provided with a hollow portion W1d having one end communicating with the air chamber Ta in the tire T and the other end communicating with the base holding hole W1e.
The base holding hole W1e is a hole for attaching the center valve unit 9 to the wheel W1, and is formed by a circular hole formed in the center of the wheel W1. On the inner wall of the base holding hole W1e, the hollow portion W1d that is continuous with the communication hole 91g formed in the outer peripheral surface 91c of the center valve unit 9 is formed. A screw hole W1f into which a bolt B1 (see FIG. 3) for fixing the wheel W1 to an axle (not shown) is screwed is formed around the base holding hole W1e.

Next, the center valve unit 9 will be described with reference to FIGS.
The center valve unit 9 shown in FIG. 7 detects the air pressure of each tire T and transmits the detection result to the vehicle body side antenna 4 (see FIG. 1), and is transmitted from the vehicle body side antenna 4 (see FIG. 1). It is a device that receives radio waves. The center valve unit 9 is pressure-bonded to the base holding hole W1e via a seal material SE (see FIG. 9).
As shown in FIG. 10, the center valve unit 9 includes a housing (holder base) 91, a tire air pressure sensor 92, a sensor-side antenna 93, and a center valve 94.
As shown in FIG. 10, among these, the tire pressure sensor 92, the sensor-side antenna 93, and the center valve 94 are built in the holder base 91.

Next, the holder base (housing) 91 will be described with reference to FIGS. 9 and 10.
As shown in FIGS. 9 and 10, the holder base 91 is composed of a bottomed cylindrical storage case main body 91a having an open top, and a lid 91b for closing the opening of the storage case main body 91a. And a reinforced resin such as a modified PPE resin. The holder base 91 is a holder base made of a bottomed cylindrical body having a diameter of about 65 mm to 80 mm and a thickness of about 25 to 30 mm, for example. The holder base 91 is fitted to the central portion of the wheel W1 with the lid body 91b facing outside.
The holder base 91 corresponds to a “housing” described in the claims.

  As shown in FIG. 9, the outer peripheral surface 91c of the holder base 91 is formed in, for example, a stepped taper shape so as to match the base holding hole W1e of the wheel W1. On the taper surface 91d formed on the outer peripheral surface 91c, a seal material SE is disposed for bringing the holder base 91 into close contact with the base holding hole W1e. Further, an insertion hole 91e for installing a detent mechanism 96 for holding the valve holder 95 of the center valve 94 at a predetermined position is formed in the outer peripheral surface 91c.

  As shown in FIGS. 9 and 10, a holder installation hole 91 f with which the valve holder 95 is engaged is formed on the inner peripheral side of the holder base 91. A plurality of communication holes 91g communicating with the hollow portion W1d of the wheel W1 and the valve port 95a formed in the valve holder 95 are formed in the holder installation hole 91f and the outer peripheral surface 91c. An air introduction hole 91h for guiding the air in the tire T to the tire pressure sensor 92 is formed on the outside of the vehicle crossing the communication hole 91g. The tire air pressure sensor 92 is fixed to a bottom surface of a storage portion 91i formed on the vehicle outer side of the holder base 91 and closed by a lid body 91b so as to close the air introduction hole 91h.

  As shown in FIG. 9, the storage portion 91i of the holder base 91 is a space formed by an annular groove, and a sensor-side antenna 93 is disposed on the outer inner wall 91j in the storage portion 91i. Near the outer inner wall 91j, a plurality of convex portions 91k are formed along the outer inner wall 91j for supporting the sensor-side antenna 93 disposed so as to be in contact with the outer inner wall 91j. The sensor-side antenna 93 is inserted between the outer inner wall 91j and the convex portion 91k, and the lid 91b is screwed to the storage case main body 91a with a screw S4, and the sensor-side antenna 93 is connected to the outer inner wall 91j. The protrusion 91k and the plurality of protrusions 91m formed on the ring-shaped lid 91b are sandwiched and held.

  The lid body 91b is a disk-shaped member made of a reinforced resin such as ABS resin or modified PPE resin, and is screwed to the storage case main body 91a via O-rings O3 and O4 to thereby fix the storage portion 91i. It is sealed.

Next, the tire pressure sensor 92 will be described with reference to FIGS. 9 and 10.
As shown in FIGS. 9 and 10, the tire air pressure sensor 92 is a sensor for detecting the air pressure of the tire T, and includes a pressure sensor, a sensor ECU, a sensor side radio wave transmitter / receiver, and a small battery (not shown). . As shown in FIG. 10, the tire air pressure sensor 92 is fixed to the bottom surface of the storage portion 91i so as to close the air introduction hole 91h, and is sealed in the storage portion 91i by a lid 91b. The tire pressure sensor 92 has a terminal 92 a for connecting to a lead wire 93 a connected to the sensor-side antenna 93.

Next, the sensor-side antenna 93 will be described with reference to FIG. 7, FIG. 9, and FIG.
A sensor-side antenna 93 shown in FIG. 10 is an antenna for transmitting / receiving radio waves to / from the vehicle-body-side antenna 4 (see FIG. 1), and is a loop antenna provided on the holder base 91 after being wound once or a plurality of times. The sensor-side antenna 93 includes, for example, a metallic conductive wire 93b, end portions 93d formed by bending both ends of the conductive wire 93b in the vehicle width direction, and the conductive wire 93b to the holder base 91. The holding member 93c for holding and a lead wire 93a connected to the end portion 93c of the conductive wire 93b are configured.
The sensor-side antenna 93 corresponds to a “loop antenna” described in the claims.

The conductive wire 93b is made of, for example, a thin flat metal that has elasticity and can be bent, and is provided on the support member 93c by insert molding or the like. The conductive wire 93b may be printed or fixed on the surface of the support member 93b.
For example, when the frequency of the radio wave is set to several GHZ, the end 93d can constitute a unipolar antenna that can receive radio waves only by the end 93.
The support member 93c is formed of a resin material to which the conductive wire 93b is fixed.

As described above, the sensor-side antenna 93 is configured by a flat cable or a flexible board having the conductive wire 93b serving as an antenna, and can be freely wound. The sensor-side antenna 93 is disposed in the vicinity of the outer peripheral portion of the back surface of the lid 91b, so that it is annularly disposed outside the vehicle at the center of the wheel W1, as shown in FIG.
The length of the sensor-side antenna 93 is set to 1/4, 1/2 or the same length of the wavelength of the radio wave according to the wavelength of the radio wave to be transmitted / received in order to improve the transmission / reception sensitivity.
For example, if the diameter of the holder base 91 is about 80 mm, the length of the sensor-side antenna 93 disposed in the vicinity of the outer peripheral surface 91c of the holder base 91 is about 250 mm, which is generally used in the tire pressure monitoring device 1. The length (about 250 mm) of ¼ of the wavelength of the existing radio wave (frequency: 300 to 400 MHZ) can be obtained. When the sensor-side antenna 93 is formed long and wound twice in a substantially spiral shape, the length of the sensor-side antenna 93 is ½ of the wavelength and wound four times. In this case, the length of the sensor-side antenna 93 is the same as the wavelength, and when the sensor-side antenna 93 is wound, the length can be set to an integral multiple of the wavelength. Thus, the sensor-side antenna 93 is configured so that its length can be adjusted appropriately.

  As in the first embodiment, the sensor-side antenna 93 may be constituted by, for example, a loop antenna formed by a conductive wire or conductive foil inserted in the vicinity of the opening end side of the holder base 91. Further, as in the first embodiment, the sensor-side antenna 93 may be formed with a length adjusting portion for adjusting the length of the sensor-side antenna 93 in the vicinity of the lead wire 93a provided at the end portion. Good.

Next, the center valve 94 will be described with reference to FIGS.
As shown in FIG. 9, the center valve 94 is a valve for injecting air into the tire T (see FIG. 7) through the continuous valve port 95a, the communication hole 91g, and the hollow portion W1d, as shown in FIG. As described above, the valve holder 95, the valve core 97, the valve body 98, and the cap 99 are configured.

  The valve holder 95 is a substantially cylindrical member that holds a valve body 98 into which the valve core 97 is inserted, and is formed of a reinforced resin such as an ABS resin or a modified PPE resin. The valve holder 95 is brought into close contact with the holder installation hole 91f of the holder base 91 via O-rings O1 and O2 (see FIG. 9). The valve holder 95 has a stepped valve holding hole 95b at the shaft center, a notch 95c at the outer periphery of the vehicle, and a locking flange formed in the storage case main body 91a shown in FIG. An annular groove 95d (see FIG. 9) to be engaged with 91n (see FIG. 9) is formed on the side surface with the valve port 95a, an O-ring installation hole 95e and recesses 95f and 95g.

  The valve port 95a is engaged with a jig (not shown) for rotating the valve holder 95 and a claw of a socket wrench in the notch 95c, and a mark 95h is placed at the position “LOCK” marked on the lid 91b. The holder installation hole 91f is closed by the inner wall when rotated, and is formed so as to communicate with the holder installation hole 91f when the mark 95h is rotated to the position of “UNLOCK” added to the lid 91b.

  A valve core 97 is inserted into the valve holding hole 95b, and a valve body 98 having a thread formed on the outer peripheral portion thereof is press-fitted or screwed. Further, a cap 99 is fitted into the air inlet 98a of the valve body 98. As a result, the opening of the valve holding hole 95b is closed.

  The detent mechanism 96 includes a steel ball 96a that engages with the locking recess 95f and the unlocking recess 95g to hold the valve holder 95 in a predetermined position, and a coil spring 96b that biases the steel ball 96a. The steel ball 96a and the coil spring 96b are constituted by a set screw 96c for confining the steel ball 96a and the coil spring 96b in the insertion hole 91e.

Next, the operation of the tire pressure monitoring device 1 will be described with reference to FIGS. 1 and 7 to 10.
For example, when the driver turns on the ignition switch and the tire pressure monitoring apparatus 1 shown in FIG. 1 is activated, a wake-up signal is sent from the vehicle-mounted ECU 7 to the sensor-side antenna 93 via the vehicle-side radio wave transmitter / receiver 6 and the vehicle-body-side antenna 4. When transmitted, the tire pressure sensor 92 is activated.
Thereafter, a data transmission request signal, a pause signal or the like is transmitted from the vehicle body side antenna 4 to the sensor side antenna 93, and a pneumatic signal or the like is transmitted from the sensor side antenna 93 to the vehicle body side antenna 4.

The vehicle body side antenna 4 is provided on the side mirror 3, and the sensor side antenna 93 is provided on the holder base 91 (see FIG. 7) disposed on the outer side of the wheel W <b> 1. 3, the radio wave transmitted from the vehicle body side antenna 4 is directly transmitted to the tire pressure sensor 92.
Furthermore, since the sensor-side antenna 93 can be increased in size by installing the center valve unit 9 at the center of the wheel W1, the space for installing the sensor-side antenna 93 is widened. The length of the side antenna 93 can be increased.
And the sensor side antenna 93 is comprised by the loop antenna provided in the vicinity of the cover body 91b, and the length of the sensor side antenna 93 can be suitably adjusted according to the frequency of a radio wave. Therefore, radio waves from the vehicle body side antenna 4 can be received with high sensitivity.
Therefore, the sensor side antenna 93 can reliably receive the radio wave transmitted from the vehicle body side antenna 4.
Further, the radio wave transmitted from the sensor side antenna 93 can be transmitted with higher sensitivity than directly transmitted to the vehicle body side antenna 4.

  The present invention is not limited to the above-described embodiments, and various modifications and changes can be made within the scope of the technical idea, and the present invention extends to these modifications and changes. Of course.

  The communication direction between the sensor side antenna (25, 93) and the vehicle body side antenna 4 may be bidirectional communication as described above, or from the sensor side antenna (25, 93) side to the vehicle body side antenna (4). ), And only the pressure signal detected by the pressure sensor (21) may be received.

1 is a block diagram showing a configuration of a passenger car including a tire pressure monitoring device according to a first embodiment of the present invention. It is a figure which shows the passenger car provided with the tire pressure monitoring apparatus which concerns on 1st Embodiment of this invention, and is a schematic diagram which shows a state when an electromagnetic wave is transmitted to the vehicle body side antenna. It is a figure which shows the wheel provided with the tire pressure sensor which concerns on 1st Embodiment of this invention, and is an exploded perspective view which shows the attachment state of a pneumatic sensor unit. 1 is an exploded perspective view of a tire pressure sensor according to a first embodiment of the present invention. FIG. 5 is a perspective view showing a layout in the housing, showing the tire pressure sensor according to the first embodiment of the present invention. It is a figure which shows the tire pressure sensor which concerns on other embodiment of this invention, and is a perspective view which shows the attachment state of the air pressure sensor unit which has the sensor side antenna wound in multiple times. It is a figure which shows the tire pressure sensor which concerns on 2nd Embodiment of this invention, and is a perspective view which shows the attachment state of a center valve unit. It is a XX direction expanded sectional view of Drawing 7. It is the A section enlarged view of FIG. It is a figure which shows the tire pressure sensor which concerns on 2nd Embodiment of this invention, and is a disassembled perspective view of a center valve unit.

Explanation of symbols

1 Tire pressure monitoring device 2,92 Air pressure sensor unit (tire pressure sensor)
4 Car body side antenna 9 Center valve unit 21 Pressure sensor 25, 93 Sensor side antenna (loop antenna)
25c Length adjustment part 27 Case 91 Holder base (case)
C Body T Tire W, W1 Wheel

Claims (2)

A tire pressure sensor comprising at least a pressure sensor that detects a tire pressure of a vehicle and a transmission unit that transmits a detection result detected by the pressure sensor,
The tire pressure sensor is housed in a housing installed at the center of the wheel that holds the tire,
The tire pressure sensor, wherein the transmitting means includes a loop antenna built in the housing.   The tire pressure sensor according to claim 1, wherein the loop antenna is disposed near an outer peripheral portion of the housing and near the outside of the vehicle.

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