JPS601524A - Semiconductor type flow-rate detecting device - Google Patents

Abstract

PURPOSE:To make durability excellent with respect to vibration and the like and to improve response by reducing thermal capacity, by providing a semiconductor chip, in which a plurality of temperature detecting elements and a heater element are formed in a flow path. CONSTITUTION:The heat of a heater 30 of a semiconductor chip 26 is transmitted to a gas flowing in a path 21 of a casing 29. The average of the temperatures of a fluid in a broad range on the upstream side of the heater 30 is detected by diodes 31-33, which are arranged at the neighboring positions. The average of the temperatures of the fluid on the downstream side of the heater 30 is detected by diodes 34-36. The temperatures can be stably detected even though the flow is disturbed. The temperature detecting elements and the heater are solid states. There are no problems of disconnection. The durability is excellent. They can be manufactured by ordinary semiconductor manufacturing technologies. Fine machining can be performed. The thermal capacity can be reduced and the response can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor flow rate detection device useful, for example, for measuring the intake air flow rate of an engine.

Conventionally, flow needles using platinum resistance wire, such as Thomas meters or hot wire flowmeters, have been known, but since the measuring element exposed to the fluid is a wire, the wires are prone to breakage due to vibrations, shocks, etc. There's a problem.

Further, a flow needle having a structure in which a resistor film is deposited or printed on an insulator such as a ceramic substrate has also been proposed. Since the measuring element is a film, it is strong against vibrations, etc., but since the resistor film is formed by a pre-depositing method or a printing method, fine processing is not possible, and the shape of the measuring element is thick. (There is a problem that this increases heat capacity and deteriorates responsiveness.

The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide a flow rate detection device that has excellent durability and responsiveness against vibrations and the like.

This object is achieved according to the invention in that the measuring element is made up of a semiconductor chip and the temperature detection element is made up of at least two semiconductor elements (diodes, transistors, etc.).

Hereinafter, embodiments of the present invention shown in the drawings will be described.

FIG. 1 shows an example of a fuel injection spark ignition engine equipped with a semiconductor flow rate detection device according to the present invention. The engine 1 sucks combustion air into a combustion chamber through an air cleaner 2 and an intake conduit 3 when an intake valve is opened. Fuel is injected and supplied from an electromagnetic fuel injection valve 6 installed in the intake conduit 3. The intake air flow rate is controlled by opening and closing the throttle valve 7 provided in the intake conduit 3, and the fuel injection amount is basically controlled by changing the opening time of the injection valve 6 using the electronic control unit 8. amount commensurate with the flow rate,
The amount is controlled by adding correction to this amount as necessary.

A rectifying grid 9 is provided immediately downstream of the air cleaner 2. This grid 9 rectifies the flow of intake air and allows the flow rate measurement by the flow rate detection device. ! It serves to improve I-determined accuracy.

In such an intake system of the engine 1, the semiconductor flow rate detection device 10 is installed in the intake conduit 3 between the throttle valve 7 and the rectifier grid 9. This device 10 is an engine I
This device measures the intake air flow rate and inputs a corresponding electric signal to the control unit 8.
2, and the sensor section 11 is disposed within the suction conduit 3.

Next, a description will be given with reference to FIG. 2, which shows the state in which this detection device 0 is attached to the suction conduit 3. Sensor section 11 and circuit section 12
A semiconductor flow rate detection device 10 consisting of the following is fixed to the suction conduit 3 with a screw.

The sensor part 11 has a fluid passage 21 in the housing parallel to the flow of fluid, and a semiconductor chip for detecting the flow rate is installed at the center of the fluid passage 21. The sensor section 11 has a dual in-line pancage type casing 23 having two rows of bins 22, and the sensor section 11 has two rows of pins 22 that output signals from a semiconductor chip through two sockets 2.
4 and is adhesively fixed so that it will not come off due to vibration etc.

The circuit section 12 processes the output signal of the semiconductor chip and outputs a signal representing the flow rate from the connector 25.

The socket 24 is located in the suction conduit 3 so that the flow passing through the flow path 21 of the sensor section 11 can represent the flow rate of the suction conduit 3 without being affected by the boundary layer on the wall of the suction conduit 3. It stands out. Further, in order to prevent flow disturbance and increase in pressure loss, the tip of the socket 24 in the flow direction is made at an acute angle.

In FIG. 3 showing the structure of the sensor section 11, a semiconductor chip is provided with a heater element and a temperature detection element formed on a silicon substrate.

27 is a ceramic substrate, on which a conductive paste is printed and fired to electrically connect the lead pins 22 and the chip 26, and the lead pins 22 and the chip 26 are soldered by the flip-chip bump method.

Note that two protruding support portions 28 are formed in the notch portion of the substrate 27, and the chip 26 is placed so as to be exposed to the air flow at these portions.

As a result, only the portion of the ceramic substrate 27 necessary for fixing the semiconductor chip and extracting the signal is located in the fluid passage 21, and the amount of heat from the heater element of the semiconductor chip 26 lost to the ceramic substrate 27 is reduced. , the amount of heat transferred from the ceramic substrate 27 to the gas is reduced (and the power consumption of the heater element is further reduced.
7 is housed and supported in a casing 29 made of PPS, for example, and the housing 29 is housed in the first casing 29.
A and a second casing 29B.

The inlet 21A of the casing 29 has a bell mouth shape so that the flow can flow into the passage 21 without disturbance.

In addition, in order to prevent the flow to the semiconductor chip 26 from stagnation, the inner part of the housing 29B is designed to protrude toward the semiconductor chip so that the flow hits the chip 26 obliquely. With such a structure, the flow rate can be detected with high accuracy.

Next, the configuration of the semiconductor chip 2G will be explained.

As a semiconductor temperature detection element, a diode or a transistor is formed, and its forward voltage is 2.0 with respect to temperature.
There are two types: one that detects temperature by utilizing the linear characteristic of ~2.5mV/'c, and the other that detects temperature by utilizing the fact that the resistance value of the diffused resistor formed by the diffusion method changes with temperature. Although any method can be considered, in this embodiment, the temperature detection element is formed by a diode. In FIG. 4A showing the semiconductor chip 26, this as a whole includes a heater 30 made of a diffused resistor, an upstream temperature detection element for detecting the fluid temperature upstream of the heater 3o, and a fluid temperature downstream of the heater 30. It consists of a downstream temperature sensing element for

The upstream temperature detection element consists of three diodes (equivalent to transistors) 31, 32, and 33, and is formed at a position slightly apart from the heater 30. The downstream temperature detection element is composed of three diodes 34, 35, and 36, and is formed near the heater 30. Note that the hatching portion is an electrode formed by aluminum vapor deposition.

Also, this depth 26' is N as shown in FIG. 4B.
-N After diffusing P-type impurities 41 and N-type impurities 42 into a small silicon wafer and etching the SiO2 film 43, the aluminum electrode 44 is coated with a protective film (Si02 film, Si3N4 film, etc.) to prevent corrosion of the aluminum electrode 44. ) 45.

Next, the detailed circuit of the circuit section 12 will be explained with reference to FIG. The circuit section 12 processes the detection signal of the sensor section 11 and outputs an output signal representing the flow rate, and the temperature output processing section 1
2A, a feedback control section 12B1, an offset adjustment section 12C, a power supply section 12D, and an output section 12E.

The processing unit 12A is a circuit for extracting the voltage between the anodes and cathodes of the diodes 31 to 36 to which a constant voltage is applied, and includes resistors 501 to 5 connected to each diode.
12, and operational amplifiers 513 and 514. Here, the resistances 507 to 5°9 give the average value between the anodes and cathodes of the diodes 31 to 33 on the upstream side of the flow, and the resistances 510 to 512 give the average value between the anodes and cathodes of the diodes 31 to 33 on the downstream side of the flow.
The average value between the anode and cathode of resistors 501 to 506 is calculated, and a resistance value that is one order of magnitude or more larger than the resistance value of resistors 501 to 506 is used. Here, if the distribution of the variation follows a normal distribution in the case where the temperature coefficient is not corrected, the variation will be 1/3 on both the upstream and downstream sides. In order to further reduce the error, resistors 501 to 5
016 may be a variable resistor. The OP amplifiers 513 and 514 impedance convert the average value of the cathode-anode voltage of the upstream and downstream diodes and output it to the feedback control section 12B.

The feedback control unit 12B controls the power consumption of the heater 30 by changing the voltage applied to the heater 30 so that the temperature difference between the upstream side and the downstream side becomes the voltage difference set by the offset adjustment unit 12C. In this circuit 521.52
2.523 is a resistor, 524.525 is a capacitor, 52
6 is an OP amplifier. And resistance 522.523,
An output signal is output with a time constant determined by capacitors 524 and 525, and the power of the signal is amplified by transistors 528 and 529 connected to Darlington through a resistor 527.

The offset adjustment unit 12C performs control using an OP amplifier 534 and a transistor 535 so that the potential difference across the resistor 533 becomes equal to the voltage determined by the resistors 53 and 532. The power supply section 12D includes a regulator 541 and a capacitor 542.5.
43 and outputs a constant voltage. The output section 12E is
It outputs the power consumed by the heater 30 as a flow signal for the detector/device, and consists of a low resistance 551, a resistance 552, 553, which has a higher resistance than the resistance 551, and an OP amplifier 554. Adjust the output gain using the division value.

In the above configuration, when the heater 30 of the semiconductor chip 26 consumes power, the heat is transferred to the passage 21 of the casing 29.
transmitted to the gas flowing inside.

Since the fluid temperature upstream of the heater 30 is detected by three diodes 31 to 33 arranged adjacently, the average fluid temperature over a wide range is detected instead of a local fluid temperature. .

Further, the fluid temperature on the downstream side of the heater 30 is similarly detected by three diodes 34 to 36, and the average fluid temperature is detected. In particular, since the fluid temperature on the downstream side is the temperature of the fluid heated by the heater 30, it is necessary to accurately detect even if the flow is disturbed, but in this application, since multiple diodes are arranged adjacently, Even if the flow is turbulent, the flow will always flow over the diode, allowing stable temperature detection.

In addition, the temperature detection element and heater are solid and not wires, so there is no problem with disconnection, and since they can be manufactured using normal semiconductor manufacturing technology, microfabrication is possible, and the physique of this part, that is, the heat capacity. Smaller size improves responsiveness.

Therefore, points A and B, which are the results detected by the diode group,
The amount of heat generated by the heater 30 is controlled by the circuit unit 12 so that the potential difference between the points is equal to the offset voltage, and the temperature difference between the diode groups 31 to 33 and the diode groups 34 to 36 is controlled to a predetermined value. When controlled in this way, the heater 30
The power consumed in the flow rate has a predetermined functional relationship with the flow rate, and increases according to a certain curve with respect to the flow rate. On the other hand, heater 3
The power consumption at 0 is output as a voltage at 0 point, so OUT
A signal corresponding to the flow rate is output from the terminal.

Note that in the above configuration, the diodes are connected in parallel, but
It is also possible to connect diodes in series as in the second embodiment shown in FIG. 6A.

In FIG. 6A, 61 to 64 indicate a group of diodes on the upstream side, and 65 to 66 indicate a group of diodes on the downstream side. This equivalent circuit diagram is shown in FIG. 7, and diodes 61 to 64
are connected in series, and diodes 65 to 68 are connected in series.

This chip 26 is made by diffusing P-type impurities 71 into a P to N-type silicon wafer to separate regions, and then diffusing P-type impurities 72 and N-type impurities 73, as shown in FIG. 6B.
A contact hole is etched in the 5i02 film 74, aluminum 75 is vapor-deposited to form an electrode, and a protective film 76 is attached.

By adopting such a configuration, variations in the diodes can be reduced (the temperature characteristics of diodes are considered to follow a normal distribution, and if four diodes are connected in series as in this example, the output will be 4). (The dispersion is isometrically reduced to 1/4 because the dispersion does not change) and becomes resistant to flow turbulence.

Further, in this embodiment, although the manufacturing process of the element is increased compared to the first embodiment, there is an advantage that the number of output lines is reduced and the configuration of the input portion of the control circuit is simplified.

In addition, as in the third embodiment shown in FIG.
6A and the temperature detection-heater chip 26B may be separated into two chips. With such a configuration, the temperature difference between the temperature detection portions composed of upstream and downstream diodes becomes larger than in the case of a single chip, and detection accuracy increases.

As described above, the present invention has the effect of being excellent in terms of durability and responsiveness. Furthermore, it can absorb variations in the temperature characteristics of semiconductor elements such as diodes, and has excellent detectability.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an engine equipped with a device according to the present invention, FIG. 2 is a cross-sectional perspective view of the main parts of the device shown in FIG.
FIG. 3 is a partial cross-sectional perspective view of the sensor section shown in FIG. 2;
4A and 4B are a plan view and a sectional view showing a semiconductor chip, respectively, FIG. 5 is an electric circuit diagram showing a circuit section used in the present invention, and FIGS. 6A and 6B are a second diagram of the present invention. 7 is an equivalent circuit diagram of the semiconductor chip shown in FIG. 6A, and FIG. 8 is a front view showing a third embodiment of the present invention. 26... Semiconductor chip, 30... Heater, 31-3
G...61-68...Diodes forming semiconductor elements. Representative Patent Attorney Takashi Okabe Figure 6A Figure 26 U Figure 68 Figure 7 Figure 8

Claims (4)

[Claims] (1) A semiconductor type characterized in that it is equipped with a semiconductor chip on which a temperature detection element consisting of at least two semiconductor elements and a heater element for heating a fluid are formed, and this semiconductor chip is installed in a flow path. Flow rate detection device. (2) The semiconductor flow rate detection device according to claim 1, wherein the semiconductor element is a diode, and the diodes are connected in series. (3) The semiconductor flow rate detection device according to claim 1, wherein the semiconductor element is a diode, and the diodes are connected in parallel. (4) The semiconductor flow rate detection device according to claim 1, wherein the temperature detection element is formed on both sides of the heater element.