JP2000162075A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the temperature difference between a pressure detecting element and a signal processing element so as to improve the output of a pressure sensor by a method wherein the pressure detecting element is connected to a thermally good thermal conductor and the good thermal conductor is extended to a chamber for the signal processing element. SOLUTION: A pressure detecting element 21 is connected thermally to a lead frame 42 as at least one good thermal conductor, and the good thermal conductor is extended to a chamber 13 for a signal processing element. A gas which is introduced from a pressure source into a chamber 12 in which the pressure detecting element 21 is installed follows the temperature of the pressure source so as to be set to an unstable state. On the other hand, since the chamber 13 in which a signal processing element 22 is installed is a comparatively closed space, it is in a state which is stable in terms of temperature. In addition, due to the heat capacity of the chamber 13 as a whole, the temperature of the signal processing element 22 is nearly equal to the temperature of the chamber 13 so as to be stable. In addition, since the pressure detecting element 21 and the thermally connected good thermal conductor are covered with a protective gel 71 whose heat insulating effect is large, the heat energy of the gas which is introduced into the chamber 12 for the pressure detecting element and that of the pressure detecting element 21 are hard to move.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor for measuring pressure, and more particularly to a pressure sensor for measuring pressure in an intake passage of a vehicle internal combustion engine.

[0002]

2. Description of the Related Art A known example similar to the present invention is disclosed in
There is a structure of a pressure sensor described in Japanese Patent Application Publication No. 1-280232. The pressure detecting element converts the detected pressure into an electric signal. The pressure and the electrical output of each pressure detecting element have differences in zero point offset, sensitivity, temperature dependency, and non-linearity due to manufacturing variations. For this reason, the pressure sensor has an initial characteristic that is measured and corrected in advance during manufacturing, and a pressure detecting element,
Alternatively, a signal processing element for measuring the temperature in the vicinity thereof and correcting the temperature dependency is required.

[0003] As in the case of various other electronic circuit devices, the integration of signal processing elements by semiconductors is advancing.
In the pressure sensor disclosed in Japanese Patent Application Laid-Open No. 1-280232, a pressure detecting element and a signal processing element are installed in separate chambers, and a heat conducting member directly attached to the signal processing element is replaced with a chamber in which the pressure detecting element is arranged. , The heat energy of the chamber in which the pressure detecting element is disposed is transferred to the signal processing element.

[0004]

However, in the above structure, the pressure detecting element and the thermal conductor which is wire-bonded to the pressure detecting element generally include water from the intake passage, which is a pressure source, and water.
In order to protect from gasoline and acid, it is necessary to cover with a protective coating having a very low thermal conductivity, and the temperature of the gas entering the pressure detecting element is not immediately transmitted to the pressure detecting element or the heat conductor.

[0005] In particular, when the temperature of the gas is changing, the temperature distribution in the room becomes large. However, in the above-mentioned structure, the heat conductor to which the signal processing element is thermally connected and the pressure detecting element are thermally separated. Therefore, the temperature difference between the pressure detection element and the signal processing element may increase. In particular, in a state where the pressure detecting element and the good thermal conductor are covered with the gel, if there is a difference in the response of the temperature change between the good thermal conductor and the pressure detecting element to the temperature change of the gas, the temperature difference becomes large.

It is an object of the present invention to provide a pressure sensor that reduces the temperature difference between a pressure detection element and a signal processing element even when the temperature of a gas is changing.

[0007]

Means for solving the above problems will be described below. The pressure sensing element is thermally connected to a thermal conductor, which extends into the chamber of the signal processing element. The extended thermal conductor may or may not be thermally connected to the signal processing element. The room in which the signal processing element is installed is in a thermally stable state, but the gas in the room in which the pressure detection element is installed is in an unstable state following the temperature of the pressure source. A thermal conductor to which the pressure sensing element is connected extends to the chamber of the signal processing element, and the pressure sensing element is covered with a protective gel having relatively low thermal conductivity, that is, a heat insulating effect.

Therefore, even when the temperature of the gas is changing, the temperature of the gas is hardly transmitted to the pressure detecting element.
Rather, the temperature of the chamber of the signal processing element is transmitted via the thermal conductor. Thus, the temperature difference between the two elements remains small. Also, when the temperature of the gas changes significantly, the temperature of the pressure detecting element changes relatively slowly due to the heat insulation effect of the gel, but the temperature of the pressure detecting element changes via a thermally connected thermally good conductor. The temperature difference between the two elements also remains small, since it propagates relatively quickly into the room of the signal processing element.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1 which shows a pressure sensor and a signal processing element as viewed from an arrangement surface, and FIG. This will be described with reference to the drawings.

The main housing 11 of the pressure sensor 10 comprises two chambers 12 and 13 for accommodating a pressure detecting element 21 and a signal processing element 22, respectively, and a connector 14 for inputting and outputting to and from the outside of the pressure sensor.

An input / output terminal between the input / output terminal of the pressure detecting element 21 and the signal processing element 22 is provided with a plurality of lead frames 4.
The wires 61 are electrically connected by bonding the wires 61 through 1 to 44. Further, the terminals of the lead frames 31 to 33 for connecting the input / output terminals of the signal processing element and the outside of the pressure sensor are also electrically connected by bonding the wires 61. The lead frames 51 to 53 via the terminals for recording correction coefficients in the signal processing element 21 and the outside are also electrically connected by bonding the wires 61.

The pressure detecting element 21 and the signal processing element 22
For example, it comprises various circuits formed on a silicon substrate. The pressure detecting element 21 includes a gauge for converting the pressure of the pressure source into an electric signal and, if necessary, a signal processing circuit such as an amplifier circuit.

The signal processing element 22 includes a correction circuit for correcting manufacturing variations and temperature dependence of the pressure detection element 21 and a temperature detection section for converting temperature, which is information necessary for temperature correction of the pressure detection element, into an electric signal. , An amplifier circuit for extracting the output of the pressure sensor to the outside, a filter circuit for removing electromagnetic noise entering from the outside of the pressure sensor and noise generated inside, and an overvoltage protection circuit for protecting against overvoltage.

This correction circuit can be constituted by either an analog circuit or a digital circuit. When the correction circuit is a digital circuit, an analog /
A digital converter and a digital / analog converter are also required. The correction coefficient necessary for the correction circuit is written from outside the pressure sensor 10 via the lead frames 51 to 53 when the characteristic adjustment is performed at the time of assembling the pressure sensor 10.
The pressure detection element 21 and the outside of the pressure sensor are connected via the signal processing element 22, and the filter circuit and the overvoltage protection circuit need only be formed on the signal processing element 22 only.

The lead frames 31 to 33 for connecting the signal processing element 22 to the outside of the pressure sensor 10 and the signal processing element 2
Lead frames 41 to 41 connecting the pressure detection element 21 to
44 may be the same material or another material. For example, for the lead frames 31 to 33, a material designated for a connector, for example, brass can be used, and for the lead frames 41 to 44, Fe-42Ni (42 alloy) can be used as described below.

The pressure detecting element 21 is made of a semiconductor substrate such as a single crystal silicon substrate, and there are detection methods such as a capacitance type and a piezoelectric strain type. In the capacitance type, the pressure detecting element 21 is directly bonded to a lead frame. Alternatively, in both methods of capacitance and piezoelectric strain, the pressure detecting element 21 is bonded to a glass base having substantially the same thermal expansion coefficient as silicon by a method such as anodic bonding, and the glass base is bonded to a lead frame or a housing. I do.

Since the pressure detecting element 21 is a sensor that converts a change in strain into an electric quantity, it is preferable that disturbance other than a change in pressure, particularly a change in electrical output characteristics due to a temperature change, be small. One of the causes of the change in the output characteristics is a difference in the thermal expansion coefficients of the pressure detecting element 21, the glass base, and the lead frame.
1, or stress is generated at the interface between the glass table and the pressure detecting element is distorted.

Therefore, the smaller the difference between the coefficients of thermal expansion of these materials, the better. For example, borosilicate glass is used as the material for the glass table, and Fe-42Ni (42 alloy) is used as the material for the lead frame.

The pressure detecting element 21 and the signal processing element 22 are provided with gels 71 and 72 for protecting them from a harmful environment.
Protect with. After each element is protected by the protective gels 71 and 72, each chamber 1 of the pressure detection element 21 and the signal processing element 22
A cover 81 having a pressure introducing pipe 82 for introducing pressure from a pressure source to only the pressure detecting element 21 is adhered.

When the chamber is divided into two parts, the chamber 12 in which the pressure detecting element 21 is installed is exposed to water, gasoline, acid and the like in the intake passage. Protect with a protective gel having excellent chemical resistance, for example, fluorosilicone gel.

The chamber in which the signal processing element 22 is installed does not need to consider chemical resistance, and can be protected by, for example, a dimethyl silicone gel. The opening of the pressure introduction pipe 82 on the pressure sensing element 21 side is
To form a sloping structure 83 that spreads out throughout the room. This is because the water that has entered through the pressure introduction pipe 82 freezes, and thus the pressure detection element 21 may be destroyed. Therefore, the water is discharged from the pressure introduction pipe 82.

The recording of the correction coefficient for correcting the output characteristic of the pressure detecting element 21 can be performed before or after the cover 81 is bonded. Before the cover 81 is bonded, a jig for providing the test pressure and temperature to the pressure detecting element 21 is used, and the correction coefficient is determined based on the relationship between the test pressure and temperature and the electrical output of the pressure sensor. To record. After the cover 81 is bonded, a test pressure and a temperature are applied, and a correction coefficient is recorded in the signal processing element 22 in the same manner.

In the present invention, the temperature difference between the two elements, the pressure detecting element 21 and the signal processing element 22, is reduced by the method described below.

The pressure sensing element 21 is thermally connected to at least one lead frame 42 which is also a good heat conductor, and this heat good conductor is extended to the chamber 13 of the signal processing element. The extended thermal conductor may or may not be thermally connected to the signal processing element 22. The gas introduced from the pressure source into the chamber 12 in which the pressure detection element 13 is installed is in an unstable state following the temperature of the pressure source.

On the other hand, the interior of the room 13 in which the signal processing elements are installed is a relatively closed space. Therefore, the signal processing element 22, the protective gel 72, and the wall in the room have substantially the same temperature, and are in a temperature-stable state.

Further, the heat capacity of the entire chamber 13 is larger than the gas in the chamber 12 of the pressure detecting element. Therefore, the temperature of the signal processing element 22 is almost equal to the temperature in the chamber 13 and is stable.

In the structure according to the present invention, the pressure detecting element 2
1 is extended to the chamber 13 of the signal processing element, and the pressure detecting element 21 and the thermal conductor to which it is thermally connected have a relatively small thermal conductivity, that is, a heat insulating effect. It is covered with a large protective gel 71. That is,
The transfer of heat energy between the signal processing element chamber 13 and the pressure detection element 21 is likely to occur, but the transfer of heat energy between the gas introduced into the pressure detection element chamber 12 and the pressure detection element 21 occurs. Hateful.

Therefore, even when the temperature of the gas is changing, the temperature of the chamber 13 of the signal processing element propagates to the pressure detecting element 21 through the good heat conductor, and the change is small.
The temperature difference between the two elements remains small.

When the temperature of the gas greatly changes, the temperature of the pressure detecting element 21 changes relatively slowly due to the heat insulation effect of the gel 71. However, the pressure detecting element 21 and the signal processing element are installed. Because the thermal energy transfer between the chambers 13 is fast, the temperature difference between the two elements also remains small.

According to the study by the present inventors, in the structure of the present invention, the temperature difference between the two elements in the steady state is within 2 ° C. In normal use, the correction error due to this temperature difference is small.

The above embodiments can be variously modified without departing from the gist thereof. For example, as a method of recording the correction coefficient in the signal processing element, a method of directly writing the signal processing element such as a laser trimming method can eliminate a correction lead frame for connecting to the outside.

There is also a method of preparing a molded product for connecting the signal processing element and the pressure detection element via a lead frame, performing adjustment, and then inserting the molded product into a main housing having a connector portion.

[0033]

According to the present invention, since the temperature difference between the pressure detecting element and the signal processing element can be reduced, the output of the pressure sensor can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a part of a pressure sensor housing viewed from an arrangement surface of a pressure detection element and a signal processing element of the present invention.

FIG. 2 is a sectional view of the entire pressure sensor housing of FIG. 1;

[Explanation of symbols]

10 pressure sensor, 11 main housing, 12, 13 ...
Chamber, 14 connector, 21 pressure detecting element, 22 signal processing element, 31 to 33, 41 to 44, 51 to 53 lead frame, 61 wire, 71, 72 protective gel, 8
1 ... cover, 82 ... pressure introduction pipe, 83 ... sloping structure.

Continued on the front page (72) Inventor Satoshi Shimada 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Norio Ichikawa 2477 Takaba, Hitachinaka-shi, Ibaraki F-term in Hitachi Car Engineering Co., Ltd. (Reference) 2F055 AA22 DD04 EE13 EE25 FF02 FF12 FF13 GG03 GG32 GG33 4M112 AA01 BA01 BA07 EA03 GA01 GA03

Claims (6)

[Claims] A pressure detecting element for converting a pressure into an electric signal; and a signal processing element comprising a semiconductor integrated circuit for processing an electric signal from the pressure detecting element, the pressure sensor being installed in different chambers. A pressure sensor, wherein a sensing element extends a thermally conductive conductor thermally connected to the chamber of the signal processing element. 2. The pressure sensor according to claim 1, wherein a thermal conductor to which said pressure detecting element is thermally connected and a thermal conductor to which said signal processing element is thermally connected are separated. 3. A pressure sensor in which a pressure detecting element and a signal processing element are installed in different chambers, wherein the entirety of the chamber including the pressure detecting element and a lead frame electrically or thermally connected has high heat insulation. A pressure sensor, wherein the pressure sensor is covered with a filler that mediates pressure. 4. The circuit according to claim 1, wherein an input / output terminal from outside the pressure sensor and an input / output terminal formed on a main surface of the pressure detecting element are formed on a main surface of the signal processing chip. Electrically connected only through the input / output terminals of
A pressure sensor, wherein the support on the back surface of the signal processing element is not electrically connected to the input / output terminals of the semiconductor pressure detection element and the support on the back surface. 5. The pressure sensor according to claim 1, wherein a correction coefficient recorded in a signal processing element for processing an electrical output from the pressure detection element is recorded from outside the pressure sensor. 6. The pressure sensor according to claim 5, wherein the pressure detection element and the signal processing element are bonded to a main housing of the pressure sensor.
Manufacturing a pressure sensor comprising the steps of: electrically connecting the pressure detection element, the signal processing element, and input / output terminals from the outside of the pressure sensor, bonding the cover, and adjusting a correction coefficient from outside the pressure sensor. Pressure sensor.