JP4561198B2 - In-cylinder pressure detector - Google Patents

Description

  The present invention relates to an in-cylinder pressure detecting device that detects an in-cylinder pressure of an internal combustion engine.

  In an internal combustion engine control system, it is necessary to grasp the current combustion state of the internal combustion engine in order to execute ignition timing control, air-fuel ratio control, and knock control. There is a method for detecting the pressure of combustion gas in the chamber (cylinder) (hereinafter, in-cylinder pressure). An in-cylinder pressure sensor is known as a sensor for detecting the in-cylinder pressure, and this in-cylinder pressure sensor generally uses a detection element whose resistance value changes according to the applied pressure. Yes.

  FIG. 6 is a bridge type detection circuit diagram of a conventional in-cylinder pressure sensor, and FIG. 7 is a single gauge type detection circuit diagram of a conventional in-cylinder pressure sensor.

In the conventional bridge type detection circuit in the in-cylinder pressure sensor, as shown in FIG. 6, four gauge resistors 001, 002, 003, 004 are connected to form a bridge, and a constant current source 005 is connected to the input side thereof. On the other hand, an amplifier 006 is connected to the output side. Therefore, when the gauge resistance value changes due to the in-cylinder pressure and the resistance change amount of the gauge resistors 001, 003 is ΔR, the resistance change amount of the gauge resistors 002, 004 is −ΔR. Therefore, the output voltage V ₀ is obtained based on the resistance value R of each gauge resistor 001, 002, 003, 004, the resistance change ΔR, and the input voltage V _E , and is amplified and output by the amplifier 006.

In a single gauge type detection circuit in a conventional in-cylinder pressure sensor, as shown in FIG. 7, a constant current source 012 is connected to the input side of the variable resistor 011 and an amplifier 013 is connected to the output side. Accordingly, the gauge resistance value of the variable resistor 011 changes due to the in-cylinder pressure, and the output voltage V ₀ is obtained based on the resistance value R, the resistance change amount ΔR, and the input voltage V _E , and is amplified by the amplifier 013. Is output.

  In addition, as a conventional in-cylinder pressure sensor, there exists a thing described in the following patent document 1, for example.

JP-A-8-261857

However, in the conventional in-cylinder pressure sensor shown in FIGS. 6 and 7 described above, the detected output voltage V ₀ is low, so it is necessary to amplify by the amplifiers 006 and 013, which increases the cost. Invited. Therefore, it is considered to use a high-power detection element having high sensitivity characteristics as a detection element and detect the in-cylinder pressure as a voltage. However, it is difficult for this high-power detection element to ensure high sensor characteristics due to a plurality of factors such as element characteristic variations, housing machining variations, and assembly tolerance variations.

  An object of the present invention is to solve such a problem, and it is an object of the present invention to provide an in-cylinder pressure detection device that ensures high sensitivity characteristics and reduces costs.

In order to solve the above-described problems and achieve the object, the in-cylinder pressure detection device of the present invention detects the in-cylinder pressure of an internal combustion engine using a high-power detection element whose resistance value changes according to the applied pressure. In the in-cylinder pressure detecting device, an offset adjusting resistor is connected in series with the high output type sensing element, and a plurality of sensitivity adjusting resistors and switching elements having different resistance values in parallel with the high output type detecting element are provided. A switch is connected, and the connection state of the plurality of sensitivity adjustment resistors can be switched by the changeover switch according to the operating state of the internal combustion engine, and the plurality of sensitivity adjustment resistors are connected to the intake stroke of the internal combustion engine. And a low-pressure detecting resistor corresponding to the in-cylinder pressure of the exhaust stroke, and a high-pressure detecting resistor corresponding to the in-cylinder pressure of the compression stroke and the combustion stroke of the internal combustion engine, in the operation stroke of the internal combustion engine Cut according It is characterized in that there was El.

Further, the in-cylinder pressure detecting device of the present invention is the in-cylinder pressure detecting device for detecting the in-cylinder pressure of the internal combustion engine using a high-output type detecting element whose resistance value changes according to the applied pressure. A resistor for offset adjustment is connected in series with the sensing element, and a variable resistor for sensitivity adjustment capable of changing a resistance value according to the operating state of the internal combustion engine is connected in parallel with the high-power sensing element . The variable resistor for sensitivity adjustment is changed so that the resistance value becomes small corresponding to the in-cylinder pressure of the intake stroke and the exhaust stroke of the internal combustion engine, while the in-cylinder of the compression stroke and the combustion stroke of the internal combustion engine The resistance value is changed so as to increase corresponding to the pressure .

According to the in-cylinder pressure detecting device of the present invention, the offset adjusting resistor is connected in series with the high-output type sensing element, and a plurality of sensitivity adjusting resistors having different resistance values in parallel with the high-output type sensing element and A change-over switch is connected, and the connection state of the plurality of sensitivity adjustment resistors can be switched by the change-over switch according to the operating state of the internal combustion engine, and the plurality of sensitivity adjustment resistors are used for the intake stroke and the exhaust stroke of the internal combustion engine. A low pressure detecting resistor corresponding to the in-cylinder pressure and a high pressure detecting resistor corresponding to the in-cylinder pressure of the compression stroke and the combustion stroke of the internal combustion engine, and switching according to the operation stroke of the internal combustion engine. A sensitivity adjustment resistor with an appropriate resistance value will be connected according to the operating state of the engine, improving the detection accuracy by increasing the sensitivity in a specific region of in-cylinder pressure and ensuring high sensitivity characteristics be able to Both can lead to cost the amplifier and filter, etc. as required.

Further, according to the in-cylinder pressure detecting device of the present invention, the offset adjusting resistor is connected in series with the high output type detecting element, and the resistance value is set in parallel with the high output type detecting element in accordance with the operating state of the internal combustion engine. Is connected to a variable resistor for sensitivity adjustment, and the variable resistor for sensitivity adjustment is changed so that the resistance value becomes small corresponding to the in-cylinder pressure of the intake stroke and the exhaust stroke of the internal combustion engine, Since the resistance value is changed so as to increase corresponding to the in-cylinder pressure of the compression stroke and combustion stroke of the internal combustion engine, the resistance value of the variable resistor for sensitivity adjustment is appropriate according to the operating state of the internal combustion engine. Thus, by increasing the sensitivity in a specific region of the in-cylinder pressure, it is possible to improve the detection accuracy and ensure high sensitivity characteristics, and it is possible to reduce costs by eliminating the need for an amplifier, a filter, and the like.

  Further, according to the in-cylinder pressure detecting device of the present invention, the offset adjusting resistor is connected in series with the high output type sensing element, and the sensitivity adjusting variable resistor is connected in parallel with the high output type detecting element. Thus, offset and variation of the detection value are suppressed, and high sensitivity characteristics can be secured, and an amplifier, a filter, and the like are not required, and cost can be reduced.

  Embodiments of an in-cylinder pressure detecting device according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  1 is a circuit diagram illustrating an in-cylinder pressure detection device according to a first embodiment of the present invention, and FIG. 2 is a graph illustrating a sensitivity adjustment result in the in-cylinder pressure detection device according to the first embodiment.

  The in-cylinder pressure detecting device of the first embodiment is installed in a combustion chamber of an internal combustion engine and constantly detects the pressure of combustion gas in the combustion chamber (cylinder), that is, the in-cylinder pressure. The internal pressure is used for ignition timing control, air-fuel ratio control, knock control, and the like. The in-cylinder pressure detecting device is configured to detect the in-cylinder pressure using a high-power detection element whose resistance value changes according to the applied pressure, that is, the in-cylinder pressure.

  In the circuit of the in-cylinder pressure detecting device of the first embodiment, as shown in FIG. 1, an offset adjusting resistor 12 is connected in series with the high output type detecting element 11, and the high output type detecting element 11 Two sensitivity adjusting resistors 13 and 14 and changeover switches 15 and 16 having different resistance values are connected in parallel. A constant current source 17 is connected to the input side of the offset adjusting resistor 12, and an electronic control unit (ECU) 19 is connected to the output side via an A / D converter 18.

  The high output type detection element 11 is a resistance change type mesa type detection element, and is exposed to the combustion chamber via the pressure transmission member and the diaphragm, and its resistance value R + ΔR changes according to the in-cylinder pressure. The offset adjusting resistor 12 adjusts to an appropriate position when the output of the high-power detection element 11 (Rs) is offset to the increase side or the decrease side. Each of the sensitivity adjustment resistors 13 and 14 adjusts to an appropriate position when the output of the high-power detection element 11 varies on the increase side or the decrease side, and depends on the operating state of the internal combustion engine. Switching is possible.

That is, the sensitivity adjusting resistor 13 is a low pressure detecting resistor corresponding to the in-cylinder pressures of the intake stroke and the exhaust stroke of the internal combustion engine, and the sensitivity adjusting resistor 14 is the compression stroke and the combustion stroke of the internal combustion engine. It is a resistor for high pressure detection corresponding to the in-cylinder pressure. Usually, the in-cylinder pressure in the compression stroke and the combustion stroke is higher than the in-cylinder pressure in the intake stroke and the exhaust stroke of the internal combustion engine, and the resistance value Rt _{1 of the} sensitivity adjusting resistor 13 is set to be small. is, the resistance value Rt ₂ sensitivity adjustment resistor 14 is set larger.

  The crank angle is constantly input to the ECU 19 from the crank angle sensor, and the ECU 19 operates the changeover switches 15 and 16 according to the crank angle to connect the resistors 13 and 14 for sensitivity adjustment. Switch state. That is, in the intake stroke and exhaust stroke of the internal combustion engine, only the changeover switch 13 is closed and the sensitivity adjusting resistor 13 is connected, while in the compression stroke and combustion stroke of the internal combustion engine, only the changeover switch 14 is closed and the sensitivity is closed. The adjustment resistor 14 is connected.

Therefore, the resistance value of the high-power detection element 11 changes due to the in-cylinder pressure, and the output is input to the ECU 19 via the A / D converter 18. The ECU 19 can obtain the output voltage V ₀ based on the resistance value R of the high-power detection element 11, the resistance change ΔR, and the input voltage V _E. In this case, the in-cylinder pressure detecting device of the present embodiment can ensure high sensitivity characteristics to obtain an output of 400 to 500 mV by unpressing.

  However, the output of the high-power detection element 11 is caused by a plurality of factors such as variations in element characteristics, variations in housing machining, and variations in assembly tolerances. Therefore, in this embodiment, the output of the high-power detection element 11 can be adjusted by the offset adjusting resistor 12 and the sensitivity adjusting resistors 13 and 14.

As shown in FIG. 2, the output C _{1 obtained} by offsetting the output C ₀ of the high-power detection element 11 to the decreasing side can be appropriately adjusted by connecting an offset adjusting resistor 12 (Rs). Further, the output C _{2 with} which the output C _{0 of} the high-power detection element 11 varies can be appropriately adjusted by connecting the sensitivity adjusting resistors 13 and 14 (R _t ). Furthermore, the output C ₃ to output C ₀ of the high output type detection element 11 varies with offset to the decrease side, connecting an offset adjustment resistor 12 (Rs) and the sensitivity adjustment resistor 13, 14 (R _t) By doing so, it can be adjusted appropriately.

  As described above, in the in-cylinder pressure detecting device of the first embodiment, the high output type detection element 11 is applied, and the offset adjusting resistor 12 is connected in series with the high output type detection element 11 and the high output type detection element 11 is connected. Two sensitivity adjusting resistors 13 and 14 and changeover switches 15 and 16 having different resistance values are connected in parallel with the output type detection element 11, and the ECU 19 operates the changeover switches 15 and 16 according to the operating state of the internal combustion engine. Thus, the connection state of the sensitivity adjusting resistors 13 and 14 can be switched.

  Therefore, the offset output of the high output type detection element 11 can be adjusted by the offset adjustment resistor 12, and the dispersed output can be adjusted by the sensitivity adjustment resistors 13 and 14, and the high output type detection element 11 can be adjusted. The detection accuracy of the element 11 can be improved, and an appropriate resistance value is selected in accordance with the operating state of the internal combustion engine. In addition to ensuring high sensitivity characteristics, it is possible to reduce costs by eliminating the need for amplifiers and filters.

  Also, one sensitivity adjusting resistor 13 is a low pressure detecting resistor corresponding to the in-cylinder pressure of the intake stroke and the exhaust stroke of the internal combustion engine, and the sensitivity adjusting resistor 14 is a compression stroke and a combustion stroke of the internal combustion engine. This is a high-pressure detection resistor corresponding to the in-cylinder pressure. Therefore, the sensitivity adjusting resistor 13 having a low resistance value is connected in the intake stroke and the exhaust stroke having a relatively low in-cylinder pressure, and the sensitivity adjustment having a high resistance value is performed in the compression stroke and the combustion stroke having a relatively high in-cylinder pressure. The resistor 14 is connected, so that the sensitivity of the in-cylinder pressure in the region necessary for each stroke can be increased, high sensitivity characteristics can be ensured, and the followability to the target can be improved.

  In the first embodiment described above, the two sensitivity adjusting resistors 13 and 14 corresponding to the operation state are used. However, the number is not limited to two. For example, the intake stroke, the exhaust stroke, the compression stroke, Four sensitivity adjusting resistors may be used for each combustion stroke, or the sensitivity adjusting resistors are divided into a plurality of regions based on the magnitude of the in-cylinder pressure according to the operating state of the engine. A vessel may be provided.

  FIG. 3 is a circuit diagram illustrating an in-cylinder pressure detection apparatus according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the member which has the same function as what was demonstrated in the Example mentioned above, and the overlapping description is abbreviate | omitted.

  In the circuit of the in-cylinder pressure detecting device of the second embodiment, as shown in FIG. 3, an offset adjusting resistor 12 is connected in series with the high output type detection element 11, and in parallel with the high output type detection element 11. A variable resistor 21 for sensitivity adjustment is connected to this. A constant current source 17 is connected to the input side of the offset adjusting resistor 12, and an electronic control unit (ECU) 19 is connected to the output side via an A / D converter 18.

  The sensitivity adjusting variable resistor 21 adjusts to an appropriate position when the output of the high-power detection element 11 varies on the increase side or the decrease side, and has a resistance value corresponding to the operating state of the internal combustion engine. It can be changed. That is, in the intake stroke and the exhaust stroke of the internal combustion engine, the in-cylinder pressure is relatively low, and thus the resistance value of the variable resistor 21 for sensitivity adjustment is reduced. On the other hand, in the compression stroke and the combustion stroke of the internal combustion engine, Since the pressure is relatively high, the resistance value of the sensitivity adjusting variable resistor 21 is increased.

Therefore, the resistance value of the high-power detection element 11 changes due to the in-cylinder pressure, and the output is input to the ECU 19 via the A / D converter 18. At this time, the offset of the output of the high-power detection element 11 is adjusted by the offset adjusting resistor 12, and the output variation is adjusted by the sensitivity adjusting variable resistor 21. Then, the ECU 19 can obtain the output voltage V ₀ based on the resistance value R, the resistance change amount ΔR, and the input voltage V _E of the high-power detection element 11.

  As described above, in the in-cylinder pressure detecting device of the second embodiment, the high output type detection element 11 is applied, and the offset adjusting resistor 12 is connected in series with the high output type detection element 11 and the high output type detection element 11 is connected. A sensitivity adjusting variable resistor 21 is connected in parallel with the output type detection element 11, and the resistance value of the sensitivity adjusting variable resistor 21 can be changed according to the operating state of the internal combustion engine.

  Therefore, the offset output of the high output type detection element 11 can be adjusted by the offset adjustment resistor 12, and the dispersed output can be adjusted by the sensitivity adjustment variable resistor 21, so that the high output type detection element 11 can be adjusted. 11 can be improved, an appropriate resistance value is selected according to the operating state of the internal combustion engine, and the detection accuracy is improved by increasing the sensitivity in a specific region of the in-cylinder pressure. In addition to ensuring high sensitivity characteristics, it is possible to reduce costs by eliminating the need for amplifiers and filters.

  FIG. 4 is a circuit diagram illustrating an in-cylinder pressure detection device according to the third embodiment of the present invention, and FIG. 5 is a circuit diagram illustrating a modification of the in-cylinder pressure detection device according to the third embodiment. In addition, the same code | symbol is attached | subjected to the member which has the same function as what was demonstrated in the Example mentioned above, and the overlapping description is abbreviate | omitted.

  In the third embodiment, as shown in FIG. 4, for example, from the high-power detection element 11, the offset adjusting resistor 12, the sensitivity adjusting resistors 13 and 14, and the changeover switches 15 and 16 described in the first embodiment. In-cylinder pressure sensors 31a, 31b, 31c, and 31d that are configured are provided in the respective combustion chambers of the internal combustion engine. The in-cylinder pressure sensors 31a, 31b, 31c, 31d and the selection switches 32a, 32b, 32c, 32d are connected in parallel, the constant current source 17 is connected to the input side, and the ECU 19 is connected to the output side. Has been.

  Further, in a modification of the third embodiment, as shown in FIG. 5, for example, the high-power detection element 11, the offset adjusting resistor 12, the sensitivity adjusting resistors 13, 14 and the changeover switch described in the first embodiment. In-cylinder pressure sensors 31a, 31b, 31c, 31d composed of 15 and 16 are provided in the respective combustion chambers of the internal combustion engine. The in-cylinder pressure sensors 31a, 31b, 31c, and 31d are connected in series, the selection switches 32a, 32b, 32c, and 32d are connected in parallel, and the constant current source 17 is connected to the input side. The ECU 19 is connected to the output side.

  Therefore, the ECU 19 opens / closes the selection switches 32a, 32b, 32c, and 32d at a predetermined timing to drive any of the in-cylinder pressure sensors 31a, 31b, 31c, and 31d, and is necessary in the operating state of the internal combustion engine. It is possible to detect the in-cylinder pressure at an appropriate time.

  As described above, in the in-cylinder pressure detecting device of the third embodiment, the in-cylinder pressure sensors 31a, 31b, 31c, and 31d are connected in parallel or in series, and the constant current source 17 is connected to the input side. The ECU 19 is connected to the output side. Therefore, a plurality of in-cylinder pressure sensors 31a, 31b, 31c, and 31d can be driven by one constant current source 17, and the number of parts can be reduced and the cost can be reduced.

  As described above, the in-cylinder pressure detection device according to the present invention has a high sensitivity by connecting a resistance adjusting resistor whose resistance value is changed according to the operating state of the internal combustion engine in parallel with the high-power detection element. It ensures both sensitivity characteristics and cost reduction, and is useful as an in-cylinder pressure detection device for all internal combustion engines.

It is a circuit diagram showing the cylinder pressure detection apparatus which concerns on Example 1 of this invention. 6 is a graph showing a sensitivity adjustment result in the in-cylinder pressure detection apparatus of Example 1. It is a circuit diagram showing the cylinder pressure detection apparatus which concerns on Example 2 of this invention. It is a circuit diagram showing the cylinder pressure detection apparatus which concerns on Example 3 of this invention. FIG. 10 is a circuit diagram illustrating a modification of the in-cylinder pressure detection device according to the third embodiment. It is a bridge type detection circuit diagram in the conventional in-cylinder pressure sensor. It is a single gauge type detection circuit diagram in a conventional in-cylinder pressure sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 High output type detection element 12 Resistor for offset adjustment 13, 14 Resistor for sensitivity adjustment 15, 16 Changeover switch 17 Constant current source 19 Electronic control unit (ECU)
21 Variable resistor for sensitivity adjustment 31a, 31b, 31c, 31d In-cylinder pressure sensor 32a, 32b, 32c, 32d Selection switch

Claims (2)

In an in-cylinder pressure detection device that detects an in-cylinder pressure of an internal combustion engine using a high-power detection element whose resistance value changes according to an applied pressure, an offset adjustment resistor is connected in series with the high-power detection element. In addition, a plurality of sensitivity adjusting resistors and change-over switches having different resistance values are connected in parallel with the high-power detection element, and the plurality of sensitivity adjusting resistors are operated by the change-over switch according to the operating state of the internal combustion engine. The connection state of the resistor can be switched, and the plurality of sensitivity adjusting resistors include a low-pressure detection resistor corresponding to an in-cylinder pressure of the intake stroke and the exhaust stroke of the internal combustion engine, a compression stroke of the internal combustion engine, and An in-cylinder pressure detecting device having a high-pressure detecting resistor corresponding to an in-cylinder pressure of a combustion stroke, and switching according to an operation stroke of the internal combustion engine . In an in-cylinder pressure detection device that detects an in-cylinder pressure of an internal combustion engine using a high-power detection element whose resistance value changes according to an applied pressure, an offset adjustment resistor is connected in series with the high-power detection element. In addition, a sensitivity adjusting variable resistor capable of changing a resistance value in accordance with an operating state of the internal combustion engine is connected in parallel with the high-power detection element, and the sensitivity adjusting variable resistor is connected to the internal combustion engine. The resistance value is changed so as to decrease corresponding to the in-cylinder pressure in the intake stroke and the exhaust stroke of the engine, while the resistance value increases corresponding to the cylinder pressure in the compression stroke and the combustion stroke of the internal combustion engine. An in-cylinder pressure detecting device that is changed .

Images