Casing structure of transmitter of tire condition monitoring apparatus

1. A transmitter in an apparatus for monitoring a condition of a tire of a vehicle, the transmitter comprising:

a circuit portion that detects pressure of the tire and generates a transmission signal that contains data representing the detected pressure of the tire; and

a casing that accommodates the circuit portion, wherein the casing has a first pressure transmitting portion that transmits the pressure in the tire to the circuit portion so that the circuit portion can detect the pressure in the tire, wherein the pressure transmitted to the circuit portion through the first pressure transmitting portion produces force that presses the circuit portion, and wherein the casing further has a second pressure transmitting portion that transmits the pressure in the tire to the circuit portion to apply force that acts against the pressing force to the circuit portion.

2. The transmitter according to claim 1 , wherein the circuit portion includes a substrate and an electronic element mounted on the substrate, the substrate having a first surface and a second surface opposite to the first surface, wherein the first pressure transmitting portion transmits the pressure in the tire to the circuit portion, thereby producing force that presses the first surface, and wherein the second pressure transmitting portion transmits the pressure in the tire to the circuit portion, thereby producing force that presses the second surface.

3. The transmitter according to claim 2 , wherein the electronic element includes a pressure sensor mounted on the first surface, and wherein the first pressure transmitting portion transmits the pressure in the tire to the pressure sensor, and the second pressure transmitting portion transmits the pressure in the tire to a section of the second surface that corresponds to the pressure sensor.

4. The transmitter according to claim 3 , wherein the pressure sensor has a pressure sensing portion, and wherein the circuit portion is covered with a potting material except for the pressure sensing portion.

5. The transmitter according to claim 2 , wherein the casing has a boss that can contact the second surface.

6. The transmitter according to claim 1 , wherein the first pressure transmitting portion has a vent hole formed in the casing.

7. The transmitter according to claim 1 , wherein the second pressure transmitting portion is provided by making a part of the casing deformable by the pressure in the tire.

8. The transmitter according to claim 7 , wherein the second pressure transmitting portion is a thin portion provided by making a part of the casing thinner than the remainder of the casing.

9. The transmitter according to claim 1 , wherein the second pressure transmitting portion has a through hole for connecting the interior of the casing with the outside.

10. A transmitter in an apparatus for monitoring a condition of a tire of a vehicle, the transmitter comprising:

a circuit portion that detects pressure of the tire and generates a transmission signal that contains data representing the detected pressure of the tire, wherein the circuit portion includes a substrate and a pressure sensor mounted on the substrate, the substrate having a first surface and a second surface opposite to the first surface, the pressure sensor being located on the first surface, the pressure sensor having a pressure sensing portion, and wherein the circuit portion is covered with a potting material except for the pressure sensing portion; and

a casing that accommodates the circuit portion, wherein the casing has a first pressure transmitting portion and a second pressure transmitting portion, the first pressure transmitting portion transmits the pressure in the tire to the pressure sensing portion, and the second pressure transmitting portion transmits the pressure in the tire to a section of the second surface that corresponds to the pressure sensor.