Pressure detecting device for vehicle

In a pressure detecting device for a vehicle, a first detection member is fixed to a sensor housing such that a first surface of a first diaphragm faces a closed space of the vehicle and a first chamber isolated from the closed space is provided to face a second surface of the first diaphragm. A second detection member is fixed to the sensor housing such that a first surface of a second diaphragm faces the closed space, and a second chamber is provided to face a second surface of the second diaphragm. When the first diaphragm and the second diaphragm are deformed by the same amount and in the same direction, the first detection member and the second detection member output signals having the same value with opposite signs. The first surface of the first diaphragm and the first surface of the second diaphragm are covered with a protection member.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2013-259282 filed on Dec. 16, 2013, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a pressure detecting device for a vehicle.

BACKGROUND

For example, JP 2007-71596 A, which corresponds to US 2007/0051599 A1, discloses a collision detecting apparatus for a vehicle. The collision detecting apparatus includes a pressure sensor disposed in the inside of a vehicle side door to detect a change in pressure inside of the side door caused by deformation of the side door in the event of a collision. The collision detecting apparatus detects a side collision of the vehicle based on the change in pressure detected by the pressure sensor. When the collision is detected, side airbags and the like are activated to protect an occupant from an impact of the collision.

In the event of the collision to the side door, the increase in pressure inside of the side door due to the deformation and vibrations of a side door member due to the impact of the collision and the travelling of the vehicle are likely to occur simultaneously. Therefore, a pressure sensor used for such a collision detecting apparatus is applied with the increase in pressure and the vibrations in a superimposed manner. As such, a detection value of the pressure sensor contains the influences by the increase in pressure and the vibrations, and thus it is difficult to accurately detect only the change in pressure inside of the side door.

The collision detecting apparatus of JP 2007-71596 A has the pressure sensor and a vibration sensor. The pressure sensor has a diaphragm disposed to face a closed space provided inside of the side door. The vibration sensor has a diaphragm isolated from the closed space. A detection value of the vibration sensor is subtracted from the detection value of the pressure sensor so as to remove the influence by the vibration of the side door from the detection value of the pressure sensor.

SUMMARY

In the collision detecting apparatus of JP 2007-71596 A, the diaphragm of the pressure sensor is covered with a protection member, which is made of a synthetic resin, whereas the diaphragm of the vibration sensor is not covered with the protection member. Therefore, although the influence by the vibrations of the diaphragms of the pressure sensor and the vibration sensor can be removed, it was difficult to remove the influence by the vibration of the protection member. Specifically, the protection member is necessary to protect electronic components of the pressure sensor. It has been highly required to improve accuracy of collision detection. As a result, the influence by the vibration of the protection member to the detection value has been increased.

It is an object of the present disclosure to provide a pressure detecting device that is capable of accurately detecting only a change in pressure generated in a vehicle.

According to an aspect of the present disclosure, a pressure detecting device for a vehicle includes a sensor housing, a first detection member, a second detection member, and a protection member. The first detection member includes a first diaphragm. The first detection member is fixed to the sensor housing such that a first surface of the first diaphragm faces a closed space of the vehicle and a first chamber that is isolated from the closed space is provided to face a second surface of the first diaphragm. The first detection member outputs a signal when the first diaphragm is deformed according to a pressure in the closed space. The second detection member includes a second diaphragm. The second detection member is fixed to the sensor housing such that a first surface of the second diaphragm faces the closed space, and a second chamber is provided to face a second surface of the second diaphragm. When the second diaphragm is deformed by the same amount and in the same direction as the first diaphragm, the second detection member outputs a signal having a same value as a signal outputted from the first detection member but having an opposite sign from that of the signal outputted from the first detection member. The protection member is filled in the sensor housing and covers the first surface of the first diaphragm and the first surface of the second diaphragm.

In such a structure, the first detection member outputs a signal containing both of a component of a change in pressure of the closed space and components of impulsive vibrations of the first diaphragm and the protection member covering the first diaphragm. The second detection member outputs a signal containing components of impulsive vibrations of the second diaphragm and the protection member covering the second diaphragm. Between the signal outputted from the first detection member and the signal outputted from the second detection member, the components of the impulsive vibrations of second diaphragm and the protection member are same in magnitude but are opposite in positive and negative signs. Therefore, the influence by the impulsive vibrations can be removed from the signals outputted from the first detection member and the second detection member by adding the signal outputted from the first detection member and the signal outputted from the second detection member. As such, the change in pressure generated in the closed space can be accurately detected.

In particular, the first detection member and the second detection member are both covered with the protection member. Therefore, by adding the signal outputted from the first detection member and the signal outputted from the second detection member, the influence by the impulsive vibration of the protection member can be removed from the detection values of the first detection member and the second detection member, in addition to the removal of the influence by the impulsive vibration of the first diaphragm and the second diaphragm. As such, the accuracy of detection of the change in pressure of the closed space can be further improved.

When the first diaphragm and the second diaphragm are deformed by the same amount and in the same direction, the first detection member and the second detection member output the signals that are same in magnitude but with opposite signs. In this case, the signals outputted from the first detection member and the second detection member may have some variations as long as the variations do not affect in the removal of the influence by the impulsive vibrations by adding the signals outputted from the first detection member and the second detection member.

DETAILED DESCRIPTION

First Embodiment

A pressure sensor structure unit SE and an airbag system including the pressure sensor structure unit SE according to a first embodiment of the present disclosure will be described with reference toFIGS. 1 to 5.

The pressure sensor structure unit SE includes a pressure sensor1. In the following description of a structure of the pressure sensor1, for the convenience of explanation, an upper side inFIG. 2is referred to as an upper side of the pressure sensor1, and a lower side inFIG. 2is referred to as a lower side of the pressure sensor1. However, the upper side and the lower side are irrelevant to an actual fixing direction of the pressure sensor1to a vehicle.

As shown inFIG. 1, a side door7of a vehicle6has an outer panel71and an inner panel72. The outer panel71is located at a side end of the vehicle6, and provides a side end surface of the vehicle6. The inner panel72is opposed to the outer panel71on a passenger compartment side of the outer panel71.

Each of the outer panel71and the inner panel72is formed by press-forming from a steel plate. The outer panel71and the inner panel72are integrated with each other by welding an outer peripheral end of the outer panel71and an outer peripheral end of the inner panel72to each other.

A door trim73is engaged to the inner panel72on a passenger compartment side of the inner panel72. The door trim73is made of a synthetic resin.

A window glass74projects from an upper end of the door7. The window glass74is movable in an up and down direction between the outer panel71and the inner panel72.

Inside of the door7, a closed chamber75is provided by the outer panel71, the inner panel72and the window glass74. The closed chamber75corresponds to a closed space. It is not always necessary that the closed chamber75is a fully closed space to resist to external high pressure. The closed chamber75may be isolated from the outside with a sealing force that can restrict entry of raindrops. The closed chamber75may be in communication with the outside through a drainage hole formed at the lower part of the door7.

The pressure sensor structure unit SE is fixed to the inner panel72. The pressure sensor structure unit SE is fixed to face the closed chamber75. The pressure sensor structure unit SE is disposed to detect an increase (change) in pressure inside of the closed chamber75that is caused by compression of the door7when the door7is deformed by a collision.

The pressure sensor1of the pressure sensor structure unit SE corresponds to a pressure detecting device for a vehicle. The pressure sensor1is a semiconductor pressure sensor. As shown inFIG. 2, the pressure sensor1includes a first sensor chip12and a second sensor chip14. The first sensor chip12is a semiconductor pressure sensor device. The first sensor chip12is disposed in a first housing11made of a synthetic resin. The second sensor chip14is a semiconductor pressure sensor device. The second sensor chip14is disposed in a second housing13made of a synthetic resin.

The first housing11and the second housing13are disposed in such a manner that a bottom wall11aof the first housing11and a bottom wall13aof the second housing13are opposed to each other through a sensor substrate20. The first sensor chip12is fixed to the bottom wall11aof the first housing11. The second sensor chip14is fixed to the bottom wall13aof the second housing13. The first sensor chip12and the second sensor chip14are disposed in opposite directions with respect to a vertical direction ofFIG. 2, such as a direction perpendicular to a sensor substrate20.

The first housing11and the second housing13form a sensor housing. The first sensor chip12corresponds to a first detection member. The second sensor chip14corresponds to a second detection member.

Each of the first sensor chip12and the second sensor chip14is made of a silicon chip. The first sensor chip12has a first recess12aon its lower surface. A first diaphragm12bis formed at a bottom (top side inFIG. 2) of the first recess12a.

The second sensor chip14has a second recess14aon its upper surface. A second diaphragm14bis formed at a bottom of the second recess14a. The second diaphragm14bhas the same shape as the first diaphragm12b.

The first diaphragm12band the second diaphragm14bcan be deformed in directions perpendicular to a planar direction thereof, such as in an upward direction and a downward direction inFIG. 2.

The first sensor chip12is fixed to the bottom wall11aof the first housing11such that a first chamber12c(air chamber) is provided between the first housing11and the first diaphragm12b. As shown inFIG. 2, the first chamber12cis isolated from the closed chamber75. By such a structure, the first diaphragm12bis disposed in such a manner that a first surface (upper surface inFIG. 2) faces the closed chamber75through a protection member18and a second surface (lower surface inFIG. 2) opposite to the first surface faces the first chamber12c.

The second sensor chip14is fixed to the bottom wall13aof the second housing13such that a second chamber14c(air space) is provided between the second housing13and the second diaphragm14b. As shown inFIG. 2, the second chamber14cis isolated from the closed chamber75. By such a structure, the second diaphragm14bis disposed in such a manner that a first surface (lower surface inFIG. 2) faces the closed chamber75through a protection member18and a second surface (upper surface inFIG. 2) opposite to the first surface faces the second chamber14c.

A circuit chip15, which is made of a silicon chip, is disposed on the bottom wall11aof the first housing11. The circuit chip15and the first sensor chip12are arranged in a horizontal direction ofFIG. 2. In other words, the circuit chip15and the first sensor chip12are arranged in a planar direction of the bottom wall11a.

A plurality of electrodes16is provided at corner portions in the first housing11. Bonding wires17connect between the electrodes16and the first sensor chip12, between the electrodes16and the circuit chip15, and between the first sensor chip12and the circuit chip15. The protection member18is filled in the first housing11to cover the first sensor chip12, the circuit chip15, the electrodes16and the bonding wires17, which are disposed in the first housing11, from the top. The protection member18is made of a fluorine-based gel, which is a fluorine-based resin material.

A circuit chip15, which is made of a silicon chip, is disposed on the bottom wall13aof the second housing13. The circuit chip15and the second sensor chip14are arranged in the horizontal direction ofFIG. 2. In other words, the circuit chip15and the second sensor chip14are arranged in a planar direction of the bottom wall13a.

A plurality of electrodes16is provided at corner portions in the second housing13. Bonding wires17connect between the electrodes16and the second sensor chip14, between the electrodes16and the circuit chip15, and between the second sensor chip14and the circuit chip15. The protection member18is also filled in the second housing13to cover the second sensor chip14, the circuit chip15, the electrodes16and the bonding wires17, which are disposed in the second housing13, from the lower side of the second housing13.

Each of the electrodes16disposed in the first housing11and the second housing13is electrically connected to the sensor substrate20through a solder19. The sensor substrate20is fixed to the inner panel72through a box member (not shown) of the pressure sensor structure unit SE. With this, the first housing11and the second housing13are fixed to the door7through the sensor substrate20.

Next, a method for detecting the pressure of the closed chamber75by the first diaphragm12band the second diaphragm14bwill be described with reference toFIGS. 2 to 4.

FIG. 3illustrates the shape of a diaphragm to represent the first diaphragm12band the second diaphragm14b. InFIG. 3, the diaphragm is shown in the same direction as the first diaphragm12bshown inFIG. 2. The second diaphragm14bshown inFIG. 2is disposed in an opposite direction from the diaphragm shown inFIG. 3.

As shown inFIG. 3, each of the first diaphragm12band the second diaphragm14bis a silicon chip processed to be thin, and is integrally formed with diffused resistors Rc, Rs thereon. The first diaphragm12bhas two diffused resistors Rc and two diffused resistors Rs. The second diaphragm14bhas two diffused resistors Rc and two diffused resistors Rs. Note that, inFIG. 3, one diffused resistor Rc is shown.

When the first diaphragm12band the second diaphragm14bare deformed in a downward direction inFIG. 3due to the change in pressure generated in the closed chamber75, resistance values of the diffused resistors Rc, Rs are increased or decreased. When an impulsive vibration occurs in the door7due to an impact of a collision or the travelling of the vehicle, the first diaphragm12band the second diaphragm14bare deformed in an upward direction or in the downward direction ofFIG. 3. Thus, the resistance values of the diffused resistors Rc, Rs are increased or decreased.

In each of the first diaphragm12band the second diaphragm14b, the diffused resistors Rc, Rs are connected in a manner shown inFIG. 4to form a Wheatstone bridge. InFIG. 4, the change in pressure generated in the closed chamber75can be detected by detecting a voltage Vs (corresponding to a signal) between a connecting point m and a connecting point n in a state where an electric current Is flows from a point X toward a point Y.

That is, when the Wheatstone bridge of the diffused resistors Rc, Rs is in an equilibrium state, the connecting point m and the connecting point n have the same potential. Therefore, the voltage Vs between the connecting point m and the connecting point n is zero.

When the pressure of the closed chamber75changes and the first diaphragm12band the second diaphragm14bare deformed in the downward direction ofFIG. 3, the resistance value of the diffused resistor Rc reduces, and the resistance value of the diffused resistor Rs increases. In this case, the potential of the connecting point m becomes higher than the potential of the connecting point n. Therefore, the voltage Vs is generated between the connecting point m and the connecting point n according to the amount of deformation of the first diaphragm12band the second diaphragm14b.

When the first diaphragm12band the second diaphragm14bare deformed in the upward direction ofFIG. 3due to the impulsive vibration applied to the door7, differently from the case described above, the resistance value of the diffused resistor Rc increases and the resistance value of the diffused resistor Rs reduces. With this, the potential of the connecting point n becomes higher than the potential of the connecting point m. Therefore, the voltage Vs is generated between the connecting point m and the connecting point n, in the opposite direction to the case described above, according to the amount of deformation of the first diaphragm12band the second diaphragm14b.

The first diaphragm12band the second diaphragm14bare set to have equal characteristics to each other. Therefore, when the first diaphragm12band the second diaphragm14bare both applied with the impulsive vibration having the same magnitude in the downward direction ofFIG. 3, the voltages Vs occur in the first diaphragm12band the second diaphragm14bwith the same value (magnitude) and in the same direction. When the first diaphragm12band the second diaphragm14bare both applied with the impulsive vibration having the same magnitude in the upward direction inFIG. 3, the voltages Vs occur in the first diaphragm12band the second diaphragm14bwith the same value (magnitude) and in the same direction.

When the first diaphragm12band the second diaphragm14bare applied with the impulsive vibration having the same magnitude, but in opposite directions, such as in the downward direction ofFIG. 3in one of the first diaphragm12band the second diaphragm14band in the upward direction ofFIG. 3in the other one of the first diaphragm12band the second diaphragm14b, the voltages Vs occur in the first diaphragm12band the second diaphragm14bwith the same value (magnitude), but in the opposite directions. The voltages Vs occurring with the same magnitude but in the opposite directions means that the voltages Vs have the same magnitude but have opposite signs.

Hereinafter, in each of the first diaphragm12band the second diaphragm14b, the voltage Vs occurring between the connecting point m and the connecting point n is referred to as a detection value. The pressure sensor1may have any structure other than the structure described hereinabove. For example, the pressure sensor1may employ a strain gauge, in place of the diffused resistors Rc, Rs.

Next, a mechanism of action of the pressure generated in the closed chamber75due to a collision to the door7and the impulsive vibration applied to the door7onto the pressure sensor1will be described with reference toFIG. 2.

As shown inFIG. 2, each of the first diaphragm12band the second diaphragm14bcan be deformed in the upward and downward directions. In the pressure sensor1, however, the first sensor chip12and the second sensor chip14are arranged in opposite directions to each other with respect the direction perpendicular to the sensor substrate20, such as in the vertical direction inFIG. 2. Therefore, when the first diaphragm12band the second diaphragm14bare deformed in the same direction inFIG. 2, the first sensor chip12and the second sensor chip14output the detection values having opposite signs, that is, one being a positive value and the other being a negative value.

As described above, the first chamber12cof the pressure sensor1is isolated from the closed chamber75. The pressure generated in the closed chamber75deforms the first diaphragm12btoward the first chamber12c, that is, in the downward direction ofFIG. 2through the protection member18.

The second chamber14cis also isolated from the closed chamber75. The pressure generated in the closed chamber75deforms the second diaphragm14btoward the second chamber14c, that is, in the upward direction inFIG. 2through the protection member18.

In this case, the first diaphragm12band the second diaphragm14bgenerate the detection values being same in magnitude but having opposite signs.

The impulsive vibration applied to the door7acts on the first diaphragm12band the second diaphragm14bin the same direction inFIG. 2, irrespective of the arrangement directions of the first diaphragm12band the second diaphragm14b. Therefore, the impulsive vibration applied to the door7causes accelerations to the first diaphragm12band the protection member18covering the first diaphragm12b, thereby deforming the first diaphragm12bin the upward direction or the downward direction ofFIG. 2.

Further, the impulsive vibration applied to the door7also causes accelerations to the second diaphragm14band the protection member18covering the second diaphragm14b, thereby deforming the second diaphragm14bin the same direction as the direction of deformation of the first diaphragm12b.

As described above, the first diaphragm12band the second diaphragm14bhave the same characteristics, including the thickness of the protection member18. Therefore, when being applied with the impulsive vibration applied to the door7, the second diaphragm14bgenerates the detection value that has the same magnitude as the magnitude of the detection value of the first diaphragm12bbut have the positive or negative sign opposite from that of the detection value of the first diaphragm12b.

In the event of collision to the door7, the first diaphragm12bgenerates the detection value containing both the pressure of the closed chamber75and the components of the impulsive vibrations of the first diaphragm12band the protection member18. The second diaphragm14bgenerates the detection value containing both the pressure of the closed chamber75and the components of the impulsive vibrations of the second diaphragm14band the protection member18. A detection value based on the components of the impulsive vibrations of the second diaphragm14band the protection member18has a positive or negative sign opposite from that of a detection value based on the components of the first diaphragm12band the protection member18.

Next, an operation of the airbag system including the pressure sensor1according to the present embodiment will be described with reference toFIG. 5. One of the circuit chips15of the pressure sensor1has a circuit portion15athat adds the detection value of the first diaphragm12band the detection value of the second diaphragm14b. The circuit portion15acorresponds to a calculation circuit. The circuit portion15ais connected to an A/D converter15b, and the A/D converter15bis connected to a collision detection unit31of an airbag controller3. The airbag controller3is a controller that is provided by input and output devices, a CPU, a RAM, and the like, which are not shown.

The airbag controller3is connected to a sensor group4. The sensor group4includes a plurality of sensors such as another pressure sensor and an acceleration sensor. The airbag controller3is connected to an airbag module5. The airbag module5may be similar to a conventional type. The airbag module5includes an inflater, a bag, and an igniter, which are not shown.

A detection value PS1 of the first diaphragm12bis the sum of the amount of change ΔP of pressure of the closed chamber75and the amount of change ΔF due to the impulsive vibrations of the first diaphragm12band the protection member18, i.e., PS1=ΔP+ΔF. The detection value PS1 corresponds to the amount of change in the event of collision relative to a normal time.

A detection value PS2 of the second diaphragm14bis the sum of the amount of change ΔP of pressure of the closed chamber75and the amount of change −ΔF due to the impulsive vibrations of the second diaphragm14band the protection member18, i.e., PS2=ΔP−ΔF. The detection value PS2 corresponds to the amount of change in the event of collision relative to a normal time.

The circuit portion15acalculates the pressure PS0 (i.e., PS0=ΔP) of the closed chamber75, i.e., the amount of change of the pressure of the closed chamber75by dividing the sum of the detection value PS1 of the first diaphragm12band the detection value PS2 of the second diaphragm14bby2. A calculation result of the circuit portion15ais digitalized by the A/D converter15b, and is then transmitted to the collision detection unit31of the airbag controller3.

When the pressure sensor1has detected that the pressure of the closed chamber75is equal to or greater than a predetermined collision threshold, when another sensor of the sensor group4has detected an increase in pressure of another door of the vehicle6, or when another acceleration sensor has detected an acceleration equal to or greater than a predetermined collision threshold, the collision detection unit31detects that a collision has occurred in the vehicle6, and activates the airbag module5.

In the first embodiment, the pressure sensor1includes the sensor housing, the first sensor chip12, the second sensor chip14, and the protection member18. The sensor housing is provided by the first housing11and the second housing13. The first sensor chip12has the first diaphragm12b. The first sensor chip12is fixed to the first housing11such that the first surface of the first diaphragm12bfaces the closed chamber75, and the second surface of the first diaphragm12bfaces the first chamber12cisolated from the closed chamber75. When the first diaphragm12bis deformed according to the change in pressure of the closed chamber75, the first sensor chip12generates a signal.

The second sensor chip14has the second diaphragm14b. The second sensor chip14is fixed to the second housing13such that the first surface of the second diaphragm14bfaces the closed chamber75, and the second surface of the second diaphragm14bfaces the second chamber14c. When the second diaphragm14bis deformed in the same direction as the deformation of the first diaphragm12band by the same amount as the deformation of the first diaphragm12b, the second sensor chip14generates a signal having the same magnitude as the signal of the first diaphragm12b, but having the positive or negative sign opposite from that of the signal of the first diaphragm12b.

The protection member18is filled in the first housing11and the second housing13to cover the first surface of the first sensor chip12and the first surface of the second sensor chip14.

In such a structure, the first sensor chip12outputs a signal in which the change in pressure of the closed chamber75and the components of the impulsive vibrations of the first diaphragm12band the protection member18covering the first diaphragm12bare mixed. The second sensor chip14outputs a signal in which the change in pressure of the closed chamber75and the components of the impulsive vibrations of the second diaphragm14band the protection member18covering the second diaphragm14bare mixed.

In the signal outputted from the first sensor chip12and the signal outputted from the second sensor chip14, the component of the impulsive vibrations of the first diaphragm12band the protection member18and the component of the impulsive vibrations of the second diaphragm14band the protection member18are same in magnitude but have opposite signs. Therefore, the influence by the impulsive vibrations can be removed from the signals of the first sensor chip12and the second sensor chip14by adding the signal from the first sensor chip12and the signal from the second sensor chip14. As such, the change in pressure generated in the closed chamber75can be accurately detected.

The first sensor chip12and the second sensor chip14are both covered with the protection member18. Therefore, by adding the signal outputted from the first sensor chip12and the signal outputted from the second sensor chip14, the influence by the impulsive vibration of the protection member18can be removed from the detection values of the first sensor chip12and the second sensor chip14, in addition to the removal of the influence by the impulsive vibrations of the first diaphragm12band the second diaphragm14b. As such, the accuracy of detection of the change in pressure of the closed chamber75can be further improved.

The pressure sensor1includes the circuit portion15athat adds the detection value of the first diaphragm12band the detection value of the second diaphragm14b. Therefore, the amount of calculations performed in the airbag controller3can be reduced, and thus the number of memories of the airbag controller3can be reduced.

The closed chamber75is provided inside of the door7. When a collision to the door7has occurred, the pressure sensor1detects the increase in pressure according to the compression of the closed chamber75. Therefore, a collision to the door7can be accurately detected.

Second Embodiment

A pressure sensor1A according to a second embodiment of the present disclosure will be hereinafter described with reference toFIG. 6. Hereinafter, points different from the pressure sensor1of the first embodiment will be mainly described. InFIG. 6, components similar to those ofFIG. 2are designated with the same reference numbers. In the description of the structures of the pressure sensor1A, for the convenience of explanation, an upper side inFIG. 6is referred to as an upper side of the pressure sensor1A, and a lower side inFIG. 6is referred to as a lower side of the pressure sensor1A. However, the upper side and the lower side are irrelevant to an actual fixing direction of the pressure sensor1A to the vehicle6.

The pressure sensor1A has a sensor housing21that is integrally formed of a synthetic resin material. As shown inFIG. 6, the sensor housing21has a pair of side walls21a,21band a middle wall21c. The side walls21a,21bextend in the up and down direction, and are opposed to each other in a horizontal direction ofFIG. 6. The middle wall21cextends in the up and down direction, and is located between the side wall21aand the side wall21b. The sensor housing21has a bottom wall21dbetween the side wall21aand the middle wall21c. The bottom wall21dextends in the horizontal direction ofFIG. 6and connects the lower end of the side wall21aand the lower end of the middle wall21c. The sensor housing21further has a top wall21eextending in the horizontal direction inFIG. 6. The top wall21econnects the upper end of the side wall21band the upper end of the middle wall21c.

The first sensor chip12is fixed to the bottom wall21d. Similar to the first embodiment, the first sensor chip12has the first recess12aon its lower surface. The first diaphragm12bis formed at the bottom (upper side) of the first recess12a. The first chamber12cis provided between the upper surface of the bottom wall21dand the first diaphragm12b. As shown inFIG. 6, the first chamber12cis isolated from the closed chamber75.

The second sensor chip14is fixed to the lower surface of the top wall21e. Similarly to the first embodiment, the second sensor chip14has the second recess14aon its upper surface. The second diaphragm14bis formed at the bottom of the second recess14a. The second chamber14cis provided between the lower surface of the top wall21eand the second diaphragm14b. As shown inFIG. 6, the second chamber14cis isolated from the closed chamber75.

On the bottom wall21dof the sensor housing21, the circuit chip15is disposed. The circuit chip15and the first sensor chip12are arranged in the horizontal direction, i.e., in the planar direction of the bottom wall21d. The plurality of electrodes16is disposed at the corner portions of the bottom wall21d. The bonding wires17connect between the electrodes16and the first sensor chip12, between the electrodes16and the circuit chip15, and between the first sensor chip12and the circuit chip15. The protection member18is filled in the sensor housing21to cover the first sensor chip12, the circuit chip15, the electrodes16and the bonding wires17, which are disposed on the bottom wall21d, from the top.

A plurality of electrodes16is also disposed at the corner portions of the top wall21e. InFIG. 6, only one electrode16is shown on the top wall21e. The electrode16and the second sensor chip14are connected to each other through a boding wire17, and the second sensor chip14is also connected to the circuit chip15disposed on the bottom wall21d. The protection member18is filled in the sensor housing21to cover the second sensor chip14, the electrodes16and the bonding wires17, which are disposed on the lower surface of the top wall21e, from the lower side.

Each of the electrodes16disposed in the sensor housing21is electrically connected to the sensor substrate20through the solder19. The sensor substrate20is fixed to the inner panel72, and the sensor housing21is fixed to the door7through the sensor substrate20. The pressure sensor1A is fixed to the door7such that the up and down direction inFIG. 6corresponds to the thickness direction of the door7, i.e., the horizontal direction inFIG. 1. The structures of the pressure sensor1A other than the above are similar to those of the pressure sensor1of the first embodiment. Therefore, the descriptions thereof are not repeated.

In the present embodiment, the first sensor chip12and the second sensor chip14are arranged next to each other in an expanding direction of the first diaphragm12band the second diaphragm14b, that is, in a direction parallel to the planar direction of the first diaphragm12band the second diaphragm14b.

Therefore, the height of the pressure sensor1A, that is, the dimension of the pressure sensor1A in the up and down direction inFIG. 6can be reduced, as compared with the pressure sensor1of the first embodiment. As such, the pressure sensor1A can be easily installed inside of the door7, which is limited to a small space.

For example, in a case where the space inside of the door7has more allowance in the up and down direction than in the thickness direction (horizontal direction of the vehicle), the pressure sensor1A can be easily arranged in the door7such that the expanding direction (the horizontal direction inFIG. 6) of the pressure sensor1A coincides with the up and down direction of the door7, and the height of the pressure sensor1A (the up and down direction inFIG. 6) coincides with the thickness direction of the door7.

Third Embodiment

A pressure sensor1B according to a third embodiment will be described with reference toFIG. 7. Hereinafter, points different from the pressure sensor1of the first embodiment will be mainly described. InFIG. 7, components similar to those ofFIG. 2are designated with the same reference numbers.

In the pressure sensor1B, the second housing13has a chamber communication hole13bon the bottom wall13a. The chamber communication hole13bcorresponds to a housing through hole. The chamber communication hole13bpenetrates through the bottom wall13aof the second housing13to allow communication between the second chamber14cand the closed chamber75. In the present embodiment, the other structures of the pressure sensor1B are similar to those of the pressure sensor1of the first embodiment. Therefore, description thereof will not be repeated.

In the present embodiment, the second chamber14cand the closed chamber75are in communication with each other through the chamber communication hole13b. The pressure generated in the closed chamber75is also introduced into the second chamber14c, and the second diaphragm14dis not deformed by the pressure generated in the closed chamber75.

Therefore, when the change in pressure occurs in the closed chamber75, the first sensor chip12outputs the detection value in which the change in pressure of the closed chamber75and the components of the impulsive vibrations of the first diaphragm12band the protection member18covering the protection member18are mixed. The second sensor chip14outputs the detection value containing the components of the impulsive vibrations of the second diaphragm14band the protection member18covering the second diaphragm14b. In the detection value of the first sensor chip12and the detection value of the second sensor chip14, the component of the impulsive vibrations of the first diaphragm12band the protection member18and the component of the impulsive vibrations of the second diaphragm14band the protection member18are same in magnitude but have opposite signs.

Therefore, only by adding the detection value of the first sensor chip12and the detection value of the second sensor chip14, that is, without dividing the sum of the detection value of the first sensor chip12and the detection value of the second sensor chip14by two, the influence by the impulsive vibrations can be removed from the detection values of the first sensor chip12and the second sensor chip14, and the change in pressure generated in the closed chamber75can be detected.

Therefore, a calculation process of calculating the change in pressure generated in the closed chamber75can be simplified, and the circuit chip15can be reduced in size and weight.

The chamber communication hole13bis formed in the bottom wall13aof the second housing13to allow communication between the second chamber14cand the closed chamber75. The chamber communication hole13bcan be formed at the same time as forming the second housing13. Therefore, the pressure sensor1B can be easily produced.

Fourth Embodiment

Next, a pressure sensor1C according to a fourth embodiment of the present disclosure will be described with reference toFIG. 8. Hereinafter, points different from the pressure sensor1A of the second embodiment will be mainly described. InFIG. 8, components similar to those ofFIG. 6are designated with the same reference numbers.

In the pressure sensor1C of the present embodiment, a chamber communication hole21fis formed in the top wall21eof the sensor housing21. The chamber communication hole21fcorresponds to the housing through hole. The chamber communication hole21fpenetrates through the top wall21eof the sensor housing21. The chamber communication hole21fallows communication between the second chamber14cand the closed chamber75.

The other structures of the pressure sensor1C are similar to those of the pressure sensor1A of the second embodiment. In the pressure sensor1C, the change in pressure generated in the closed chamber75is detected in the similar manner to the pressure sensor1B of the third embodiment. Therefore, descriptions thereof are not repeated.

Fifth Embodiment

Next, a pressure sensor1D according to a fifth embodiment of the present disclosure will be described with reference toFIG. 9. Hereinafter, points different from the pressure sensor1of the first embodiment will be mainly described. InFIG. 9, structures similar to those ofFIG. 2are designated with the same reference numbers.

In the description of the structures of the pressure sensor1D, for the convenience of explanation, an upper side inFIG. 9is referred to as an upper side of the pressure sensor1D, and a lower side inFIG. 9is referred to as a lower side of the pressure sensor1D. However, the upper side and the lower side are irrelevant to an actual fixing direction of the pressure sensor1D to the vehicle6. InFIG. 9, illustration of the solder19and the sensor substrate20are omitted.

The pressure sensor1D has a sensor housing22that is integrally formed of a synthetic resin material. As shown inFIG. 9, the sensor housing22has a pair of side walls22a,22band a separation wall22c. The side walls22a,22bare opposed to each other in a horizontal direction ofFIG. 9. The separation wall22cextends in the horizontal direction ofFIG. 9and connects a middle portion of the side wall22aand a middle portion of the side wall22b.

The first sensor chip12having the first diaphragm12bis fixed to a first surface of the separation wall22c, such as an upper surface of the separation wall22cinFIG. 9. The first chamber12cis provided between the upper surface of the separation wall22cand the first diaphragm12b. As shown inFIG. 9, the first chamber12cis isolated from the closed chamber75.

The second sensor chip14having the second diaphragm14bis fixed to a second surface of the separation wall22c, such as a lower surface of the separation wall22cinFIG. 9. The second chamber14cis provided between the lower surface of the separation wall22cand the second diaphragm14b. The second chamber14cis opposite to the first chamber12cwith respect to the separation wall22c. As shown inFIG. 9, the second chamber14cis isolated from the closed chamber75.

On the upper surface of the separation wall22c, the circuit chip15is arranged. The circuit chip15and the first sensor chip12are arranged in the horizontal direction ofFIG. 9, such as in a planar direction of the separation wall22c. The plurality of electrodes16is disposed at the corner portions of the separation wall22c. The bonding wires17connect between the electrodes16and the first sensor chip12, between the electrodes16and the circuit chip15, and between the first sensor chip12and the circuit chip15.

The protection member18is filled in the sensor housing22to cover the first sensor chip12, the circuit chip15, the electrodes16and the bonding wires17, which are disposed on the upper surface of the separation wall22c, from the top.

The circuit chip15is also disposed on the lower surface of the separation wall22c. The circuit chip15and the second sensor chip14are arranged in the horizontal direction ofFIG. 9, such as in the planar direction of the separation wall22c. The plurality of electrodes16is also disposed at the corner portions of the lower surface of the separation wall22c. The bonding wires17connect between the electrode16and the second sensor chip14, between the electrode16and the circuit chip15, and between the second sensor chip14and the circuit chip15.

The protection member18is filled in the sensor housing22to cover the second sensor chip14, the electrodes16and the bonding wires17, which are disposed on the lower surface of the separation wall22c, from the bottom. As shown inFIG. 9, the separation wall22cis formed with a sensor connection hole22d. The sensor connection hole22dpenetrates through the separation wall22cin the up and down direction ofFIG. 9. The first chamber12cand the second chamber14care in communication with each other through the sensor connection hole22d, and thus the first chamber12cand the second chamber14care integrated with each other. In other words, the first chamber12cand the second chamber14care integrated into a single chamber. In the present embodiment, the other structures of the pressure sensor1D are similar to those of the pressure sensor1of the first embodiment. Therefore, description thereof will not be repeated.

In the present embodiment, the first chamber12cand the second chamber14care in communication with each other, and are formed into one chamber. Therefore, the entirety of the pressure sensor1D can be reduced in size.

Sixth Embodiment

Next, an airbag system including a pressure sensor1E according to a sixth embodiment of the present disclosure will be described with reference toFIG. 10. Hereinafter, points different from the first embodiment will be mainly described. InFIG. 10, components similar to the structures ofFIG. 5are designated with the same reference numbers.

The pressure sensor1E is different from the pressure sensor1of the first embodiment only on a point that a circuit chip15A connected to the first sensor chip12and the second sensor chip14does not include the circuit portion15a. Instead, an airbag controller3A includes a calculation portion32having similar functions to those of the circuit portion15aof the first embodiment. The calculation portion32is connected to the A/D converter15bof the circuit chip15A, and the collision detection unit31of the airbag controller3A.

In this case, the detection value PS1 by the first diaphragm12band the detection value PS2 by the second diaphragm14bare digitalized by the A/D converter15b, and then transmitted to the airbag controller3A. In the calculation portion32, the detection value PS1 and the detection value PS2 are added to each other, and then divided by two.

The other structures of the airbag system according to the present embodiment are similar to the airbag system of the first embodiment. Therefore, the description thereof will not be repeated.

In the present embodiment, the circuit chip15A does not have the circuit portion15a. Therefore, the circuit chip15A can be reduced in size. With this, the pressure sensor1E can be reduced in size.

Other Embodiments

The present disclosure are not limited to the embodiments described hereinabove, but may be modified or expanded in various other ways, for example in the following manners.

Use of the pressure sensors1to1E may be limited to detect a collision to the side door7. The pressure sensors1to1E may be adaptable to detect a collision to a rear door of the vehicle6, in addition to the side door7.

The pressure sensors1to1E may be used for any purpose other than the detection of a collision to the vehicle6. Namely, the pressure sensor of the present disclosure may be used to detect various types of pressure generated in a vehicle.

In the pressure sensors1to1E, when the first diaphragm12band the second diaphragm14bare applied with the same impulsive vibrations (e.g., the impulsive vibrations in the same direction and with the same magnitude), the first sensor chip12and the second sensor chip14output the detection values that are same in magnitude but have opposite signs. The detection value of the first diaphragm12band the detection value of the second diaphragm14bmay have some variations as long as the variations do not affect in the removal of the influence by the impulsive vibrations from the detection values when the detection value of the first diaphragm12band the detection value of the second diaphragm14bare added.

While only the selected exemplary embodiment and examples have been chosen to illustrate the present disclosure, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made therein without departing from the scope of the disclosure as defined in the appended claims. Furthermore, the foregoing description of the exemplary embodiment and examples according to the present disclosure is provided for illustration only, and not for the purpose of limiting the disclosure as defined by the appended claims and their equivalents.