JP2013076364A - Air cleaner device of internal combustion engine, and control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel air cleaner device capable of detecting a pressure fluctuation of an intake passage on the downstream side of an air filter using a strain sensor.SOLUTION: An air cleaner 21 is installed in the intake passage 20 of an internal combustion engine and collects foreign matters within the intake air by an air filter 72 contained inside a filter case 71. The strain sensor 80 is installed on a case bottom wall section 77 of the filter case 71 on the downstream side of the air filter 72. The strain of the case bottom wall section 77 caused by the pressure fluctuation on the downstream side of the air filter 72 is detected by the strain sensor 80.

Description

  The present invention relates to an air cleaner device for an internal combustion engine and a control device for an internal combustion engine provided with the air cleaner device.

  In the intake passage of the internal combustion engine, an air cleaner is provided in which an air filter that collects foreign matters such as dust in the air is housed in a filter case. In such an air cleaner, if the air filter is clogged, the engine output is reduced and the fuel consumption is deteriorated. For example, as described in Patent Document 1, a flow meter provided on the downstream side of the air cleaner is used. 2. Description of the Related Art Conventionally, there has been known a device that detects the clogging of an air filter by using the detected intake air amount and notifies the driver of the clogging of the air filter and prompts the air filter to be replaced.

  On the other hand, as described in Patent Document 2 and the like, a semiconductor in which a Wheatstone bridge circuit composed of a plurality of diffusion resistors is formed on a semiconductor substrate instead of a conventional resistance wire strain gauge and an amplifier circuit is formed on the same substrate Various types of strain sensors have been proposed by the present applicant.

JP 2011-080421 A JP 2005-114443 A

  When the air filter is clogged, the airflow resistance increases and the negative pressure in the intake passage on the downstream side of the air filter increases. Although it is conceivable that the negative pressure downstream of the filter is directly detected by a pressure sensor, such a pressure sensor needs to be assembled to a filter case or the like with the sensor element facing the internal space to be detected. For this reason, it is necessary to increase the number of processing steps and the number of parts, and it is necessary to secure a certain installation space, and the degree of freedom in layout is low.

  The present invention has been made in view of such circumstances, and an internal combustion engine provided with an air cleaner that is provided in an intake passage of an internal combustion engine and collects foreign matter in intake air by an air filter housed in a filter case. In this air cleaner apparatus, a strain sensor is attached to the wall of the filter case on the downstream side of the air filter.

  If the pressure in the intake passage on the downstream side of the air filter fluctuates due to clogging of the air filter, blow-back of intake air, etc., the wall of the filter case on the downstream side of the filter is distorted due to the pressure difference from the atmospheric pressure. Therefore, by detecting this distortion with a distortion sensor, it is possible to determine and detect pressure fluctuations in the intake passage on the downstream side of the filter due to clogging of the air filter, blow-back of intake air, and the like.

  As the strain sensor, a semiconductor strain sensor in which a Wheatstone bridge circuit composed of a plurality of diffusion resistors is formed on a semiconductor substrate is suitable. Since such a semiconductor strain sensor can obtain extremely high sensitivity, it is possible to detect a very slight strain of the filter case with high accuracy. Further, such a semiconductor strain sensor has a small and light configuration of about 1 to 2 mm square or less and can be directly attached to the wall of the filter case, so that the layout is free. High degree of installation, easy installation work, and little increase in ventilation resistance.

  ADVANTAGE OF THE INVENTION According to this invention, the air cleaner apparatus of the novel internal combustion engine which can detect the pressure fluctuation in the intake passage downstream from an air filter can be provided.

The block diagram which shows the system configuration | structure of the internal combustion engine to which the air cleaner apparatus which concerns on one Example of this invention was applied. The block diagram which shows the input / output system of an engine control unit. The top view (A) and sectional drawing (B) which show simply the air cleaner apparatus provided with the strain sensor. Explanatory drawing which shows the relationship between the amount of intake air and distortion in a fouling air cleaner and a new air cleaner. The flowchart which shows the flow of the diagnostic process of an air cleaner. The flowchart which shows the flow of correction | amendment control of EGR amount. The flowchart which shows the flow of an estimation process of an intake flow direction. The flowchart which shows the flow of the determination process of a backfire.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Referring to FIG. 1, this internal combustion engine 10 is a so-called MPI (multi-cylinder fuel injection) type in-line four-cylinder spark ignition gasoline internal combustion engine that injects fuel toward an intake port of each cylinder. The combustion chamber 11 of each cylinder is provided with an ignition plug 12 for spark-igniting the air-fuel mixture, and an intake port 14 is connected via an intake valve 13 and an exhaust port 16 is connected via an exhaust valve 15. In the intake passage 20, in order from the upstream side, an air cleaner 21 that collects foreign matters such as dust in the intake air, a hot wire type air flow sensor 22 that detects the intake air amount, and a throttle that adjusts the intake air amount A valve 23 and an injector 24 for injecting fuel toward the intake port 14 of each cylinder are provided. An outside air introduction duct (not shown) is provided on the upstream side of the air cleaner 21, and the air cleaner 21 and the throttle valve 23 are connected by a clean side intake duct 25. The throttle valve 23 is an electric type driven by a throttle drive motor 26, and is provided with a throttle opening sensor 27 for detecting the throttle opening. An intake collector 28 is provided on the downstream side of the throttle valve 23, and the air passing through the intake collector 28 is distributed to the intake port 14 of each cylinder by the intake manifold 29 and supplied to the combustion chamber 11 through the intake valve 13. Is done.

  A catalyst 32 such as a three-way catalyst for purifying exhaust gas is provided in the exhaust passage 31, and a muffler 33 for noise reduction is provided on the downstream side of the catalyst 32. An air-fuel ratio sensor 34 such as an oxygen concentration sensor that detects the air-fuel ratio of the exhaust is attached upstream of the catalyst 32. Based on the signal from the air-fuel ratio sensor 34, air-fuel ratio feedback control is performed to adjust the fuel injection amount so as to maintain the target air-fuel ratio (theoretical air-fuel ratio).

  Further, as an EGR (exhaust gas recirculation) device that recirculates exhaust gas in the exhaust passage 31 to the intake passage 20 downstream of the air cleaner 21 and upstream of the throttle valve 23, a bypass that connects the exhaust passage 31 and the intake passage 20 An EGR valve 37 is provided in the passage 36. The EGR valve 37 is an electric type that can adjust the EGR amount (EGR rate) according to the engine operating state.

  As the valve driving system, variable valve timing mechanisms 38 and 39 that can change the valve timing are provided for the intake valve 13 and the exhaust valve 15 respectively. These variable valve timing mechanisms 38 and 39 drive and control the valve timings of the intake valve 13 and the exhaust valve 15 in accordance with the engine operating state. The valve drive system is not limited to such a variable type, and may be a fixed valve drive system having a constant valve lift characteristic. The fuel system is provided with a fuel pump 42 for supplying the fuel in the fuel tank 40 to the fuel pipe 41 and a pressure regulator 43 for adjusting the fuel in the fuel pipe 41 to a constant pressure.

  The cylinder block 10A of the internal combustion engine 10 includes a crank angle sensor 44 that detects the engine speed (rotation speed), an oil temperature sensor 45 that detects the temperature of the engine oil, and a water temperature sensor that detects the cooling water temperature in the water jacket. 46 are attached. A cam angle sensor 47 for detecting the rotation angle of the camshaft is attached to the cylinder head 10B of the internal combustion engine 10. Furthermore, an air conditioner switch 48, a neutral switch 49 incorporated in the transmission, a battery temperature sensor 51 for detecting the temperature of the on-vehicle battery power unit 50, an accelerator opening sensor 53 for detecting the opening of the accelerator pedal 52, and the like are provided. Yes.

  The control unit 60 is of a microcomputer type having a CPU 61 that executes various arithmetic processes and a power supply IC 62 that supplies power to the CPU 61. When signals and the like input to the control unit 60 are arranged using FIG. 2, the control unit 60 detects an ignition switch 63 for starting / stopping the engine and an intake air temperature in addition to the sensors and switches described above. Sensor signals or switch signals are input from the intake air temperature sensor 64, the auxiliary load switch 65, the strain sensor 80 described later, and the like.

  Based on the signals input from these sensors and switches, the control unit 60 is provided with the injector 24 of each cylinder and the power transistor (ignition switch) 12A of the spark plug 12, the throttle drive motor 26, the variable valve timing mechanisms 38, 39. A signal is output to each of the solenoid and the fuel pump 42 to control the operation thereof.

  Next, an air cleaner apparatus provided with a strain sensor that forms the main part of the present embodiment will be described with reference to FIG. The air cleaner 21 is roughly constituted by a filter case 71 having a box shape that is divided into two by injection molding of a synthetic resin material and the like, and an air filter 72 accommodated inside the filter case 71. An inlet pipe portion 73 connected to an outside air introduction duct (not shown) is provided at one end side in the ventilation direction (left and right direction in FIG. 3) of the filter case 71, and clean side intake air is provided at the other end side in the ventilation direction. An outlet pipe portion 74 connected to the duct 25 is provided.

  The air filter 72 is disposed obliquely along the diagonal line of the filter case 71, and the air filter 72 disposed obliquely in this way causes the internal space of the filter case 71 to be upstream of the passage communicating with the inlet pipe portion 73. Side dust side 75 and a clean side 76 on the downstream side of the passage communicating with the outlet pipe portion 74, and dust or the like when the intake air introduced from the inlet pipe portion 73 passes through the air filter 72. It is configured to collect the foreign matter. The filter case 71 only needs to be capable of being slightly elastically deformed, and may be formed of a metal material such as thin aluminum in addition to the synthetic resin material as in the present embodiment. The air filter 72 is made of a filter medium made of paper or non-woven fabric with appropriate roughness.

  In this embodiment, at least one strain sensor 80 is attached to the case bottom wall 77 of the filter case 71 that forms the clean side 76 on the downstream side of the air filter 72. The strain sensor 80 detects a detection signal corresponding to a strain that is a minute elastic deformation of the filter case 71 and outputs the detection signal to the control unit 60.

  For example, when the air filter 72 is clogged to increase the airflow resistance and a negative pressure is generated on the clean side 76 on the downstream side of the air filter 72, the case bottom wall 77 moves inward due to the pressure difference from the atmospheric pressure. Since a distorted distortion is generated, the distortion of the air filter 72 can be detected by detecting the distortion with the distortion sensor 80.

  The strain sensor 80 is attached to the inner surface or the outer surface of the wall portion of the filter case 71 by using an adhesive, for example, or attached by bonding or fitting. In the example of FIG. 3, the strain sensor 80 is attached to the inner surface of the wall portion of the filter case 71, and in this case, the strain sensor 80 is not affected by contamination by rainwater or the like, and thus is excellent in reliability and durability. When the strain sensor 80 is attached to the inner surface side in this manner, it is preferable that the strain sensor 80 can be wirelessly supplied with power and the output signal can be transmitted to the control unit 60. On the other hand, when the strain sensor 80 is attached to the outer surface of the wall portion of the filter case 71, an increase in ventilation resistance can be avoided, and attachment work and wiring work can be facilitated as compared with the case where the strain sensor 80 is attached to the inner surface side.

  The strain sensor 80 is preferably provided in a portion of the wall portion of the filter case 71 that is likely to be distorted or bent in accordance with fluctuations in internal pressure. In the example of FIG. 3, the strain sensor 80 has the largest area. It is attached to the center of the wide case bottom wall 77. However, the installation position of the strain sensor is not limited to this. For example, the strain sensor may be attached to the front and rear wall portions and the side wall portions where the inlet pipe portion 73 and the outlet pipe portion 74 are provided. In order to increase the detection sensitivity, the wall of the filter case to which the strain sensor is attached may be thinned or the reinforcing ribs may be omitted to weaken its rigidity and facilitate deformation.

  Since the specific structure of the strain sensor 80 is known as described in Japanese Patent Application Laid-Open No. 2006-220574, a detailed description thereof will be omitted here. And a semiconductor strain sensor in which an amplifier circuit is formed on the same substrate.

  The sensitivity of such a semiconductor strain sensor 80 is very high, and a very slight distortion of the filter case 71 can be measured with high accuracy. Moreover, since it is a small and lightweight structure of about 1 to 2 mm square, the degree of freedom in layout is high and the mounting work is easy. In particular, the semiconductor strain sensor 80 integrated with an amplifier circuit has high noise resistance and is not affected by noise from an ignition system of an internal combustion engine.

  In particular, in the air cleaner device of this embodiment, the case bottom wall 77 to which the strain sensor 80 is attached functions as a wide pressure receiving surface, and the wide pressure receiving surface detects the internal pressure as an average pressure. For example, even when the pressure distribution is non-uniform due to occurrence of local clogging, stable pressure determination is possible.

  As an example of the control process using the detection signal of the strain sensor 80, first, diagnosis of air cleaner contamination and clogging will be described with reference to FIGS. As shown in FIG. 4, in the fouled air cleaner clogged due to fouling, the airflow resistance is increased compared to a new air cleaner without fouling, so the negative pressure on the clean side 76 on the downstream side of the filter is increased, The distortion of the case bottom wall 77 is increased. Further, as the intake air amount increases, the flow rate of the intake air passing through the air filter 72 increases, and the negative pressure increases, so the above distortion increases. From this, the intake air amount is detected and estimated using the air flow sensor 22 and the like, and the clogging of the air cleaner 21 is diagnosed using the intake air amount and the distortion obtained by the distortion sensor 80. be able to.

  FIG. 5 is a flowchart schematically showing the flow of the diagnostic process of the air cleaner 21 as described above. In step S <b> 11, the distortion of the case bottom wall 77 that forms the clean side 76 is measured based on the detection signal of the distortion sensor 80. In step S12, a contamination coefficient corresponding to the contamination degree of the air cleaner 21 is calculated based on this distortion and the intake air amount detected and estimated by the airflow sensor 22 and the like. This contamination coefficient is an index of the degree of contamination of the air cleaner, and is obtained by correcting the detected distortion by correcting the amount of intake air. Under the same intake air amount, the value of the contamination coefficient increases as the distortion increases. There is a relationship. In step S13, it is determined whether or not the contamination coefficient exceeds a predetermined threshold value set in advance. If the contamination coefficient exceeds the threshold value, it is determined that clogging has occurred due to contamination, the process proceeds to step S14, and a replacement request for the air filter 72 is output. In response to the output of the replacement request, the driver is notified of the replacement request by a warning light or voice, and fail-safe control is performed as necessary.

  Next, the EGR amount correction control using the detection signal of the strain sensor 80 will be described with reference to FIG. If the negative pressure in the intake passage 20 into which EGR is introduced becomes large due to clogging of the air filter 72 or the like, the EGR amount may increase carelessly due to the negative pressure, which may deteriorate combustion stability. Therefore, in this example, the detection signal of the strain sensor 80 is used to detect the pressure (negative pressure) state of the intake passage downstream of the air cleaner 21 and the EGR amount is corrected accordingly. .

  FIG. 6 is a flowchart schematically showing the flow of such EGR amount correction control. In steps S21 and S22, the contamination coefficient of the air cleaner 21 is calculated based on the detection signal of the strain sensor 80, as in the above-described steps S11 and S12. In step S23, an EGR correction amount is calculated based on the stain coefficient. Specifically, as the contamination coefficient increases, the air cleaner becomes more fouled, and the negative pressure in the intake passage on the downstream side of the filter increases, so that the EGR amount decreases toward the decrease side of the EGR amount. Increase the correction amount. Thereby, it is possible to suppress the EGR amount from becoming excessive due to air cleaner contamination, and to supply an appropriate EGR amount according to the engine operating state regardless of the air cleaner contamination state.

  Next, an intake flow direction estimation process using the strain sensor 80 will be described with reference to FIG. In step S31, similarly to steps S11 and S21 described above, the detection signal of the strain sensor 80 corresponding to the strain of the case bottom wall 77 is measured. In step S32, the pressure in the intake passage on the downstream side of the filter is estimated based on the detection signal of the strain sensor 80. In step S33, the intake flow direction in the intake passage is estimated based on the estimated pressure.

  Here, blowback from the combustion chamber 11 to the intake passage 20 occurs according to the valve timing of the intake valve 13 or the like. For example, if the intake valve opens before exhaust ends, blowback to the intake side occurs, and the intake valve closes to the intake side during the compression stroke even when the closing timing of the intake valve is retarded from the bottom dead center. Blowback occurs. Such blowback to the intake side occurs periodically according to the combustion cycle of each cylinder. When the flow direction in the intake passage on the downstream side of the filter changes due to the effect of such blowback, the pressure in the intake passage changes accordingly, and the distortion of the case bottom wall 77 and the state of occurrence of stress also change. To do. Therefore, by estimating the pressure fluctuation using the detection signal of the strain sensor 80, the intake flow direction in the intake passage can be estimated. Based on the intake flow direction thus estimated, for example, the intake air amount detected by the hot wire airflow sensor 22 is corrected. Further, by correcting the valve timing of the intake valve based on the intake flow direction, it is possible to improve the volume efficiency using the intake pulsation effect and to suppress the occurrence of excessive blowback from the combustion chamber to the intake passage.

  FIG. 8 shows a so-called backfire determination process in which a flame flows backward from the combustion chamber to the intake passage side using the strain sensor 80. When backfire occurs, a rapid backflow from the combustion chamber to the intake passage occurs, and a large pressure acts on the intake passage. Therefore, the occurrence of backfire is detected from the pressure in the intake passage obtained by the strain sensor 80.・ Can be estimated.

  In steps S41 and S42, the pressure in the intake passage 20 on the downstream side of the filter is estimated based on the detection signal of the strain sensor 80, as in steps S31 and S32. In step S43, it is determined whether or not the estimated pressure exceeds a predetermined threshold value set in advance for determination of the backfire. When the estimated pressure exceeds the threshold value, the process proceeds to step S44, and it is determined that a backfire has occurred. When the occurrence of backfire is detected in this way, for example, ignition timing correction control is performed in order to suppress and eliminate the backfire.

  As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes. For example, in the above embodiment, the present invention is applied to a port injection type internal combustion engine. However, the present invention is applied to a cylinder injection type internal combustion engine that directly injects fuel into a cylinder and a compression self-ignition type diesel internal combustion engine. Can also be applied.

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine 20 ... Intake passage 21 ... Air cleaner 22 ... Hot wire type air flow sensor 23 ... Throttle valve 60 ... Control unit 71 ... Filter case 72 ... Air filter 80 ... Strain sensor

Claims (6)

In an air cleaner device of an internal combustion engine provided with an air cleaner that is provided in an intake passage of an internal combustion engine and collects foreign matter in intake air by an air filter housed in a filter case,
An air cleaner device for an internal combustion engine, wherein a strain sensor is attached to a wall portion of a filter case on the downstream side of the air filter. The strain sensor is a semiconductor strain sensor in which a Wheatstone bridge circuit composed of a plurality of diffusion resistors is formed on a semiconductor substrate,
2. The air cleaner apparatus for an internal combustion engine according to claim 1, wherein the semiconductor strain sensor is attached to a wall portion of the filter case.   The control device for an internal combustion engine provided with the air cleaner device according to claim 1 or 2, wherein clogging of the air filter is determined based on a detection signal of the strain sensor. An EGR valve capable of adjusting the EGR amount of the exhaust gas recirculated to the intake passage downstream of the air cleaner according to the engine operating state;
3. The control device for an internal combustion engine provided with the air cleaner device according to claim 1, wherein the EGR amount is corrected based on a detection signal of the strain sensor.   3. The control device for an internal combustion engine having an air cleaner device according to claim 1, wherein an intake flow direction in the intake passage is detected based on a detection signal of the strain sensor.   3. Control of an internal combustion engine equipped with an air cleaner device according to claim 1, wherein the occurrence of backfire in which a flame flows backward from the combustion chamber to the intake passage side is determined based on a detection signal of the strain sensor. apparatus.

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