JP4904881B2 - Pressure detecting device and intake passage of internal combustion engine - Google Patents

Description

  The present invention relates to a pressure detection device that detects intake negative pressure in an intake passage downstream of a throttle valve, and an intake passage of an internal combustion engine to which the pressure detection device is attached.

  For example, in an electronically controlled fuel injection device provided in an automobile engine, intake pipe negative pressure is an important factor for determining the fuel injection amount.

  For this reason, a pressure detection device for detecting the intake pipe negative pressure is provided, and the negative pressure in the intake passage is guided to the pressure detection device via a pressure introduction passage that opens downstream from the throttle valve in the intake passage.

  FIG. 3 is a schematic view of an automobile engine. The basic operation of the engine 40 as shown in FIG. 3 will be described. First, air is supplied from the intake passage (intake manifold) 46 toward the cylinder 50. Further, the fuel is injected from the fuel injection device 45 and supplied into the cylinder 50 of the internal combustion engine together with the air flowing through the intake passage 46.

  In the cylinder 50, the piston 51, the valve 48, and the spark plug 49 operate in synchronization with each other, so that the air / fuel mixture is “intake” → “compress” → “combustion (ignition / expansion)”. The engine operates by repeatedly performing a series of operations “→ exhaust (exhaust gas)”.

  In order to control the engine speed and power, the amount of air flowing through the intake passage 46 and the amount of fuel injected from the fuel injection device 45 may be controlled. A mechanical valve for controlling the amount of air flowing into the intake passage 46 is a throttle valve 44. The throttle valve 44 is opened and closed according to the operation of the accelerator in the driver's seat, and controls the amount of air flowing through the intake passage 46.

  Further, a pressure detection device 43 is used via a pressure introduction path 42 to measure the amount of air flowing in the intake passage 46 controlled by the throttle valve 44 in the throttle body 41. . The value measured by the pressure detection device 43 is output to an engine control device (ECU) 47, and the amount of fuel injected from the fuel injection device 45 by the engine control device (ECU) 47 based on the value of the pressure detection device 43 is determined. Control. Thereby, the combustion efficiency in the cylinder 50 is improved and optimized.

  In recent years, restrictions on environmental loads such as carbon dioxide emissions have become stricter year by year, and improvement of the combustion efficiency of motorcycle engines is the most effective field for environmental load countermeasures. Accordingly, detection means for measuring the pressure and temperature of the intake passage plays an important role in improving combustion efficiency.

  Conventionally, as a pressure detection device (pressure sensor) for measuring the pressure of the intake passage of the internal combustion engine, a semiconductor sensor such as a device using a piezoresistance effect by diffusion resistance or a device using capacitance is used. Are known.

  FIG. 4 is an external view showing the pressure detection device, and FIG. 5 is a cross-sectional view taken along line II in FIG.

  In this pressure detection device, a glass pedestal 69 on which a semiconductor pressure sensor chip 63 as a sensor element is mounted is fixed to a sensor mount 62 of a storage container body 61 made of resin by an adhesive 81 or the like, and the semiconductor pressure sensor chip 63 And a lead terminal (lead frame) 65 are electrically connected by a bonding wire 66, the surface of the semiconductor pressure sensor chip 63 and the bonding wire 66 are protected by a gel-like protective member 67, and a pressure introducing pipe 64 is connected to the storage container body 61. The pressure detection chamber 68 is configured by bonding.

  The pressure introducing pipe 64 includes a base 71 used for joining to the storage container main body 61 and a cylindrical portion 72 for introducing a medium to be measured. In the cylindrical portion 72, a protective portion 73 is provided so as to substantially block the entrance of the pressure detecting chamber 68 in a state where the pressure detecting chamber 68 and the space in the cylindrical portion 72 are in circulation. The space in the cylindrical portion 72 is connected to a pressure measurement space (not shown).

  The protection part 73 is configured by, for example, three pieces of projecting parts 74, 75, and 76 that protrude into the cylindrical part 72. These three pieces of projections 74, 75, 76 are formed by the three pieces of projections 74, 75, 76 when the inside of the cylindrical portion 72 is viewed from the opposite side of the base 71 (upper side in FIG. 5). It is arranged so that the inside is hardly or completely visible. In addition, the protection part 73 may be comprised by the protrusion part of 2 pieces or 4 pieces or more. In such a pressure detection device, a deteriorated and solidified foreign substance such as gasoline enters the pressure detection chamber and collides with the surface of the sensing unit to prevent variation in the amount of change in the diaphragm. Such a pressure detection device is described in Patent Document 1.

  FIG. 6 is a plan view of the semiconductor pressure sensor chip 63 shown in FIG.

  This is a semiconductor pressure sensor using a piezoresistance effect, and a resistance element (not shown) is formed on the diaphragm 84. Around that, a signal processing circuit 82 including an amplification circuit that amplifies a signal from the resistance element, a sensitivity adjustment circuit, an offset adjustment circuit, a temperature characteristic adjustment circuit, and an EPROM that sends adjustment trimming data to these adjustment circuits is arranged. ing. Input / output pads 83 for EPROM trimming, power input and sensor output are arranged on both sides of the chip.

  7 is a cross-sectional view of the main part of the EPROM after the write operation is performed, FIG. 8 is an equivalent circuit diagram of FIG. 7, and FIG. 9 shows the initial state of the EPROM and the respective MOSFETs after the write. It is a figure which shows the relationship between a threshold voltage and drain current. Note that the threshold voltage in the initial state is Vth (ini), and the threshold voltage after writing is Vth (wri).

  FIG. 7 shows an EPROM having a single-layer polysilicon structure, and shows one cell. An n-type control gate region 2 is formed on the surface layer of the p-type semiconductor substrate 1, and a floating gate 7 is formed thereon via a gate insulating film 5. The floating gate 7 is also formed on the gate insulating film 5 formed on the semiconductor substrate 1 between the drain region 3 and the source region 4. The MOSFET 15 constituted by the semiconductor substrate 1, the drain region 3, the source region 4 and the floating gate 7 and the control gate region 2 are separated by a LOCOS 6. An interlayer insulating film 8 made of a silicon oxide film is formed on the floating gate 7, contact holes are formed in the interlayer insulating film 8, and the control gate electrode 9, the drain electrode 10 and the source electrode 11 are controlled respectively. It is formed so as to be connected to gate region 2, drain region 3 and source region 4. A surface protective film 13 made of a silicon nitride film is formed on the control gate electrode 9, the drain electrode 10 and the source electrode 11. The steps up to here constitute the semiconductor pressure sensor chip 63. As shown in FIG. 5, the surface protective film 13 is protected by a gel-like protective member 14 (67).

  In order to write to the EPROM, a considerably high voltage is applied to the control gate electrode 9 and the drain electrode 10. At this time, the source electrode 11 and the semiconductor substrate 1 are grounded. The electrons injected from the source region 4 into the semiconductor substrate 1 penetrate the gate insulating film 5 and are injected into the floating gate 7 (indicated by negative charges in FIG. 7), so that the floating gate 7 is charged to the negative side. become. As shown in FIG. 8, the control gate region 2, the floating gate 7, and the gate insulating film 5 therebetween constitute a capacitor C1, and the floating gate 7, the semiconductor substrate 1 and the gate insulating film 5 therebetween constitute a capacitor C2. Yes. As shown in part A of FIG. 8, the electrons injected into the floating gate 7 are shaped like a battery that generates a counter electromotive force, so as to cancel the voltage (Vcg) applied from the control gate electrode 9. Play an important role.

  As shown in FIG. 9, the EPROM characteristics after writing transition to a state in which the MOSFET 15 cannot be turned on unless a voltage higher than the determination voltage is input. Note that the determination voltage is set between Vth (ini) and Vth (wri). By making a circuit in which this determination voltage is given as Vcg at regular times, a binary state is created in which the MOSFET 15 is turned on for the cell in the initial state and the MOSFET 15 is turned off for the cell after writing. Can be used as "0" and "1".

  In the engine 40 of FIG. 3, the intake air contains gasoline, water, etc. charged by friction in the fuel tank or during fuel injection, and if these adhere to the surface of the gel-like protective member 14, Become. The mechanism of malfunction is as follows.

  FIG. 10 is a cross-sectional view of the main part of the EPROM when charged gasoline adheres to the surface, and FIG. 11 is an equivalent circuit diagram of FIG.

  When charged gasoline (indicated by a positive charge in FIG. 10) adheres to the surface of the gel-like protective member 14, the charged gasoline becomes one electrode and the floating gate 7 becomes the other electrode, and the gel-like protective member 14, The surface protective film 13 and the interlayer insulating film 8 constitute a capacitor C3, and the potential (Vgel) of the surface of the gel-like protective member 14 is transmitted to the floating gate 7 via this capacitor C3, and the potential of the floating gate 7 Fluctuates. Originally, since the determination voltage (Vcg) is constant in the steady state, the on / off state of the MOSFET 15 is determined depending on whether or not the EPROM is written. However, when charged gasoline is attached, the determination voltage is distorted. As shown in FIG. 10, when positively charged gasoline adheres, the written EPROM is equivalent to the unwritten (initial state) EPROM, and all MOSFETs 15 may be turned on, or charged negatively. When gasoline adheres, the unwritten EPROM is equivalent to the written EPROM, and all MOSFETs 15 may be turned off. In these cases, the digital data set in the EPROM is garbled, leading to fluctuations in the output of the pressure detection device.

Conventionally, Patent Document 2 and the like have proposed a filter or the like provided in a pressure introduction path so that charged gasoline does not reach the sensing portion surface of the pressure detection device. Further, Japanese Patent Application Laid-Open No. H10-228561 is known that employs a method of sensing pressure on the side of the pressure detection device where the semiconductor circuit pattern is not formed (back surface pressing method).
JP 2002-310836 A Japanese Patent Laid-Open No. 11-82198 Japanese Patent Laid-Open No. 2-100372

  Conventionally, since pressure sensors for two-wheeled vehicles, particularly sports bikes, require a quick response, a pressure detecting device is often disposed in the vicinity of the fuel injection device. In this case, it is well known that gasoline is charged by friction in the fuel tank or during fuel injection. When EPROM trimming is used for adjusting sensitivity, offset, and temperature characteristics in the pressure detection device, there is a problem that charged gasoline adheres to the gel-like protective member of the pressure detection device and deteriorates the sensor performance. In order not to cause these problems, a filter is provided in the pressure introduction path as described in Patent Document 2, or a back surface pressure type pressure detection device is selected as described in Patent Document 3. However, there was a problem that the cost was high. Moreover, in patent document 1, it does not describe at all about the problem of adhesion of charged gasoline. The present invention is to provide a surface pressure type pressure detection device and an intake passage for an internal combustion engine that can be manufactured inexpensively and with high accuracy and are not easily affected by charged gasoline.

In order to solve the above-described problem, a pressure detection device disposed in a pressure introduction path connected to a downstream side of a throttle valve of an intake passage of an internal combustion engine,
The pressure detection device includes a sensor element that converts pressure into an electrical signal, a signal processing circuit element that processes an electrical signal from the sensor element, a pressure detection chamber that houses the sensor element and the signal processing circuit element, A pressure introduction pipe that communicates and connects the pressure detection chamber and the pressure introduction path, and an insulating gel-like protective member that separates the pressure sensor element and the signal processing circuit element from the pressure detection chamber,
The signal processing circuit element includes a floating gate formed on a semiconductor substrate via a gate insulating film, a metal shield electrode formed on the floating gate via an interlayer insulating film, and on the metal shield electrode EPROM having a surface protective film,
The pressure detection chamber is positioned on the surface protective film via the gel-like protective member.

Further, it is assumed that a protective portion is provided inside the pressure introduction pipe so as to substantially block the entrance of the pressure detection chamber in a state where the pressure detection chamber and the intake passage are in circulation.

  The sensor element and the signal processing circuit element are integrated on the same semiconductor substrate.

  Further, it is assumed that the sensor element and the signal processing circuit element are formed in separate semiconductor substrates.

  The EPROM includes an n-type control gate region formed in a surface layer of a p-type semiconductor substrate, a control gate electrode connected to the n-type control gate region, and the interlayer insulating film on the n-type control gate region. And the n-type MOS transistor using the floating gate as a gate electrode.

  Further, the metal shield electrode and the control gate electrode are made of the same material.

  Further, the metal shield electrode is grounded.

  Further, the metal shield electrode is connected to the power source of the EPROM.

Alternatively, a throttle valve provided in an intake passage of an internal combustion engine, a fuel injection device provided in the intake passage, and provided in the intake passage between the throttle valve and the fuel injection device on the downstream side of the throttle valve. A pressure introduction path,
A sensor element for converting pressure into an electrical signal, a signal processing circuit element for processing an electrical signal from the sensor element, and a pressure detection chamber for housing the sensor element and the signal processing circuit element , provided in the pressure introduction path A pressure introduction pipe that communicates the pressure detection chamber and the pressure introduction path, and an insulating gel-like protective member that separates the pressure sensor element and the signal processing circuit element from the pressure detection chamber, The signal processing circuit element includes a floating gate formed on a semiconductor substrate via a gate insulating film, a metal shield electrode formed on the floating gate via an interlayer insulating film, and on the metal shield electrode comprising a EPROM having a surface protective film, provided with a pressure detecting device which positions the pressure detection chamber through the gel protective member on the surface protective film And an intake passage of the combustion engine.

  With the above solution, in the pressure detection device disposed near the fuel injection device because a quick response is required for a pressure sensor for a motorcycle, particularly for a sports motorcycle, EPROM trimming is used to adjust sensitivity, offset and temperature characteristics. In this case, by providing a metal shield electrode in the upper layer of the floating gate, the charged gasoline adheres to the surface of the sensing part of the negative pressure detecting pressure detecting device provided in the intake passage, and the phenomenon of deteriorating the sensor performance does not occur. It is possible to provide a highly reliable pressure detection device and an intake passage for an internal combustion engine.

[Example 1]
In the pressure detection device shown in FIGS. 4, 5 and 6, the following EPROM was manufactured.

  FIG. 1 is a cross-sectional view of an essential part of the EPROM of the pressure detection device of the present invention, and FIG. 2 is an equivalent circuit diagram of FIG.

  The same parts as those shown in FIG. The difference from FIG. 10 is that a metal shield electrode 12 is provided on the floating gate 7. The metal shield electrode 12 is formed by sputtering simultaneously with the control gate electrode 9, the drain electrode 10 and the source electrode 11. Although only one cell is shown in FIG. 1, there are a plurality of other cells, and in other cells, the metal shield electrode 12 is formed on the floating gate 7, and all the metal shield electrodes 12 are the same. It should be held at a potential. As shown in FIG. 2, the potential of the metal shield electrode 12 is grounded. Thus, by providing the metal shield electrode 12 on the floating gate 7, as shown in FIG. 2, the metal shield electrode 12 provided on the upper layer of the floating gate 7, a fluorine-based gel (for example, fluorosilicone gel). By blocking the path that had affected the floating gate 7 from the surface of the gel-like protective member 14 made of, etc., and forcibly bypassing it to GND, it has the effect of eliminating the influence (path) on the floating gate. ing. Therefore, in this pressure detection device, even if charged gasoline adheres to the surface of the gel-like protection member 14, the fluctuation of the output is suppressed and the phenomenon of deteriorating the sensor performance does not occur. Further, in this embodiment, the metal film forming process for the metal shield electrode 12 and the metal film forming process used for wiring for electrical connection on the chip such as the control gate electrode 9, the drain electrode 10 and the source electrode 11 are performed. By implementing this in one process (simultaneously), no additional man-hours are required for the conventional process.

  Further, in this embodiment, since the pressure detection device shown in FIGS. 4, 5, and 6 is used, the protective portion 73 is formed, and it is possible to suppress the charged gasoline from adhering to the gel-like protective member 14. This can more reliably prevent fluctuations in the output of the pressure detection device. In addition, even if it is a pressure detection apparatus in which the protection part 73 is not formed, there can exist the effect of this invention.

  In this embodiment, the metal shield electrode 12 is grounded, but may be held at a predetermined potential by connecting to the power source of the EPROM.

Further, this embodiment can be applied to a case in which an insulating film such as the interlayer insulating film 8, the surface protective film 13, and the gel-like protective member 14 is provided between the EPROM floating gate 7 and the pressure detection chamber 68. Therefore, in this embodiment, the semiconductor pressure sensor chip 63 is used as the sensor element. However, the signal processing circuit includes the sensor element that converts the surface pressure into an electrical signal and the EPROM that processes the electrical signal from the sensor element. The element may be formed as a separate semiconductor chip.

Principal step diagram of EPROM of Embodiment 1 of the present invention Equivalent circuit diagram of FIG. Schematic diagram of automotive engine External view showing pressure detector Sectional view taken along II in FIG. Plan view of the semiconductor pressure sensor chip shown in FIG. Cross section of the main part of the EPROM after the write operation is performed Equivalent circuit diagram of FIG. The figure which shows the relationship between the threshold voltage and drain current of each MOSFET after the initial state of EPROM and after writing Cross section of the main part of EPROM when charged gasoline adheres to the surface Equivalent circuit diagram of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Control gate area | region 3 Drain area | region 4 Source area | region 5 Gate insulating film 6 LOCOS
7 Floating gate 8 Interlayer insulating film 9 Control gate electrode 10 Drain electrode 11 Source electrode 12 Metal shield electrode 13 Surface protective film 14, 67 Gel-like protective member

Claims (9)

A pressure detection device disposed in a pressure introduction path connected to a downstream side of a throttle valve of an intake passage of an internal combustion engine,
The pressure detection device includes a sensor element that converts pressure into an electrical signal, a signal processing circuit element that processes an electrical signal from the sensor element, a pressure detection chamber that houses the sensor element and the signal processing circuit element, A pressure introduction pipe that communicates and connects the pressure detection chamber and the pressure introduction path, and an insulating gel-like protective member that separates the pressure sensor element and the signal processing circuit element from the pressure detection chamber,
The signal processing circuit element includes a floating gate formed on a semiconductor substrate via a gate insulating film, a metal shield electrode formed on the floating gate via an interlayer insulating film, and on the metal shield electrode EPROM having a surface protective film,
The pressure detection device, wherein the pressure detection chamber is located on the surface protective film via the gel-like protective member . 3. The protection unit provided inside the pressure introduction pipe so as to substantially block an inlet of the pressure detection chamber in a state where the pressure detection chamber and the intake passage are in circulation. The pressure detection apparatus as described. The pressure detection device according to claim 1, wherein the sensor element and the signal processing circuit element are integrated in the same semiconductor substrate . The pressure detection device according to claim 1, wherein the sensor element and the signal processing circuit element are formed in different semiconductor substrates . The EPROM includes an n-type control gate region formed in a surface layer of a p-type semiconductor substrate, a control gate electrode connected to the n-type control gate region, and the interlayer insulating film on the n-type control gate region. 5. The pressure detection device according to claim 1, further comprising: the floating gate made of polysilicon formed of n-type and an n-type MOS transistor using the floating gate as a gate electrode. 6. . The pressure detection device according to claim 5 , wherein the metal shield electrode and the control gate electrode are made of the same material . The pressure detection apparatus according to claim 1, wherein the metal shield electrode is grounded . The pressure detection apparatus according to claim 1, wherein the metal shield electrode is connected to a power source of the EPROM . A throttle valve provided in an intake passage of an internal combustion engine; a fuel injection device provided in the intake passage; and provided in the intake passage between the throttle valve and the fuel injection device downstream of the throttle valve. A pressure introduction path;
  A sensor element for converting pressure into an electrical signal, a signal processing circuit element for processing an electrical signal from the sensor element, and a pressure detection chamber for housing the sensor element and the signal processing circuit element, provided in the pressure introduction path A pressure introduction pipe that communicates the pressure detection chamber and the pressure introduction path, and an insulating gel-like protective member that separates the pressure sensor element and the signal processing circuit element from the pressure detection chamber, The signal processing circuit element includes a floating gate formed on a semiconductor substrate via a gate insulating film, a metal shield electrode formed on the floating gate via an interlayer insulating film, and on the metal shield electrode An EPROM having a surface protective film, and a pressure detection device in which the pressure detection chamber is located on the surface protective film via the gel-like protective member;
An intake passage for an internal combustion engine, comprising:

Images