JP2013036378A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively suppress deterioration of an intake pressure sensor caused by stuck soot while enabling a large amount of EGR gas to merge into intake air.SOLUTION: There is adopted an internal combustion engine 0 that includes: a drive turbine 52 installed in an exhaust passage 4; a compressor 51 driven by the drive turbine; an EGR apparatus 2 which is a low-pressure loop type exhaust gas recycling apparatus where an EGR valve 22 is installed on an EGR passage 20 connecting the downstream side of the drive turbine and the upstream side of the compressor; a throttle valve 33 installed on the downstream side of the compressor in an intake passage 3; a fresh air bypass passage 7 connecting the upstream side of an outlet 20b of the EGR passage in the intake passage and the downstream side of the throttle valve; a bypass valve 71 which is a flow adjusting valve to control the flow rate of the fresh air and is installed on the fresh air bypass passage; and an intake pressure sensor 8 which is a pressure sensor installed between the bypass valve and an outlet 7b in the fresh air bypass passage.

Description

  The present invention relates to an internal combustion engine accompanied by an exhaust turbocharger and an exhaust gas recirculation device.

Conventionally, to reduce the combustion temperature in the cylinders, than Te to reduce the emissions of the NO _x which is a harmful substance exhaust gas recirculation (Exhaust Gas Recirculation) system has been known. The EGR device mixes a part of exhaust gas generated by combustion into intake air.

  In an internal combustion engine equipped with such an EGR device, there is a problem that a sensor such as an intake pressure sensor provided in the intake passage is contaminated and deteriorated by soot in exhaust gas introduced into the intake passage through the EGR passage. Various configurations have been considered for suppression. As an example thereof, a mode in which a deflection member that deflects the flow direction of the intake air is provided upstream of the sensor in the intake passage and downstream of the outlet of the EGR passage, and a part of the soot is attached to the deflection member, An aspect in which a sensor is provided at a location where the soot distribution density is small is considered (for example, see Patent Document 1).

  Here, in the internal combustion engine described in Patent Document 1, a high-pressure loop EGR that recirculates the high-temperature and high-pressure exhaust gas immediately after being discharged from the cylinder to the intake passage is employed. The low-pressure loop EGR that recirculates the low-temperature and low-pressure exhaust gas that has passed through the turbine and the exhaust gas purifying catalyst to the intake passage is advantageous in that a large amount of EGR gas can be mixed into the intake air. In the low pressure loop EGR, the outlet of the EGR passage is connected to the upstream side of the compressor of the exhaust turbocharger for the purpose of recirculating the EGR gas close to the atmospheric pressure. In an internal combustion engine that employs such a low-pressure loop EGR, a large amount of EGR gas can be mixed into the intake air, so that the amount of soot in the exhaust gas introduced into the intake passage via the EGR passage may be larger.

  In the configuration described in Patent Document 1, the amount of soot contained in the air passing through the vicinity of the sensor can surely be suppressed. However, in the internal combustion engine employing the low pressure loop EGR, as described above, the intake passage is not provided. Since the absolute amount of soot passing therethrough is large, there is a possibility that a problem that the sensor provided in the intake passage is contaminated and deteriorated by soot cannot be sufficiently suppressed.

  Furthermore, in order to suppress the occurrence of a problem that the sensor becomes dirty and deteriorates, there may be a mode in which a filter for removing soot is provided on the upstream side of the sensor in the intake passage. In this case, the removed soot is filtered. As a result, another problem arises in that it takes time to periodically replace the filter.

JP-A-10-141113

  The present invention focuses on the above points, and an object thereof is to effectively suppress the occurrence of a problem that the intake pressure sensor is contaminated and deteriorated by soot while allowing a large amount of EGR gas to be mixed into the intake air.

  That is, an internal combustion engine according to the present invention includes a turbine provided in an exhaust passage, a compressor provided in an intake passage and driven by the turbine, a downstream side of the turbine in the exhaust passage, and an upstream of the compressor in the intake passage. A low-pressure loop type exhaust gas recirculation device in which an EGR valve is provided on an EGR passage connecting the side, a throttle valve provided downstream of the compressor in the intake passage, and the EGR in the intake passage A fresh air bypass passage connecting the upstream side of the outlet of the passage and the downstream side of the throttle valve, a flow rate adjusting valve provided in the fresh air bypass passage for controlling the flow rate of fresh air, and the fresh air bypass passage And a pressure sensor provided between the flow rate adjusting valve and the outlet.

  If it is such, since a pressure sensor can be cleaned using the flow of fresh air every time fresh air flows through the fresh air bypass passage, a large amount of EGR gas is introduced into the combustion chamber. In this way, deterioration due to soot contained in the EGR gas of the pressure sensor can be suppressed without providing a filter in the intake passage. In addition, since the pressure sensor is provided in the fresh air bypass passage deviated from the flow of the intake air including the EGR gas, the deterioration of the pressure sensor due to the soot contained in the EGR gas can be suppressed also from this point.

  Furthermore, if a control device that performs idle speed control by adjusting the opening of the flow rate adjusting valve is provided, the pressure sensor can be cleaned every time the idle operation is performed, which is more effective. In addition, it is possible to suppress deterioration due to contamination of the pressure sensor. In addition, by cleaning the pressure sensor during idle operation when the driver is not driving, fresh air flows in regardless of the driver's intention, and the fuel injection amount and engine speed increase accordingly. It is also possible to suppress the occurrence of a problem that gives the person a sense of discomfort.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the malfunction which an intake pressure sensor becomes dirty and deteriorates by soot can be suppressed effectively, enabling it to mix a lot of EGR gas into intake air.

The figure which shows the structure of the internal combustion engine and exhaust-gas recirculation apparatus in one Embodiment of this invention. The figure which shows the bypass valve in the same embodiment. The figure which shows the bypass valve in the other embodiment of this invention. The figure which shows the bypass valve in the other embodiment of this invention.

  An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, the outline | summary of the internal combustion engine 0 for vehicles in this embodiment is shown. The internal combustion engine 0 of the present embodiment includes a plurality of cylinders 1 (one of which is shown in FIG. 1), an injector 11 that injects fuel into each cylinder 1, and supplies intake air to each cylinder 1. An intake passage 3 for exhausting the exhaust gas, an exhaust passage 4 for discharging exhaust gas from each cylinder 1, an exhaust turbocharger 5 for supercharging intake air flowing through the intake passage 3, and an exhaust passage 4 to the intake passage 3. An exhaust gas recirculation device (hereinafter referred to as EGR device 2) that recirculates EGR gas toward the vehicle and a fresh air bypass passage 7 that bypasses the midway of the intake passage 3 are provided.

  The internal combustion engine 0 in this embodiment is a two-cylinder four-cycle engine, and there is a phase difference of 360 ° CA (crank angle) between the stroke of the first cylinder 1 and the stroke of the second cylinder 1. That is, the piston 12 of the first cylinder 1 and the piston 12 of the second cylinder 1 are simultaneously raised and simultaneously lowered.

  The intake passage 3 takes in air from the outside and guides it to the intake port of the cylinder 1. On the intake passage 3, an air cleaner 31, an intake throttle valve 35, a compressor 51 of the supercharger 5, an intercooler 32, an electronic throttle valve 33, a surge tank 34, and an intake manifold 36 are arranged in this order from the upstream.

  The exhaust turbocharger 5 is configured such that the drive turbine 52 and the compressor 51 are connected and linked in a coaxial manner. Then, the driving turbine 52 is rotationally driven by using the energy of the exhaust gas, and the compressor 51 is pumped by using the rotational force, whereby the intake air is pressurized and compressed (supercharged) and sent to the cylinder 1.

  The EGR device 2 realizes a so-called low pressure loop EGR. The pressure loss in the low-pressure loop EGR passage is as small as several hundred Pa. The EGR device 2 has an inlet 20 a connected to a predetermined position downstream of the drive turbine 52, more specifically, a downstream side of the three-way catalyst 41 in the exhaust passage 4, and an outlet 20 b connected to the intake air in the intake passage 3. An EGR passage 20 connected to a predetermined location downstream of the throttle valve 35 and upstream of the compressor 51, and an EGR cooler 21 and an EGR valve 22 provided on the EGR passage 20 are provided.

  In the low-pressure loop EGR, low-pressure exhaust gas close to atmospheric pressure is recirculated to the intake passage 3 through the EGR passage 2. For this purpose, the pressure around the outlet 20b of the EGR passage 20 is reduced to a negative pressure by restricting the intake throttle valve 35 upstream of the outlet 20b of the EGR passage 20. It should be noted that the pressure upstream of the intake throttle valve 35 in the intake passage 3 becomes substantially atmospheric pressure or becomes somewhat negative due to the operation of the compressor 51.

  The fresh air bypass passage 7 avoids the compressor 51, the intercooler 32, and the throttle valve 33 and guides air to the intake port of the cylinder 1. The inlet 7 a of the fresh air bypass passage 7 is connected to a predetermined location upstream of the outlet 20 b of the EGR passage 20, more specifically, upstream of the intake throttle valve 35 in the intake passage 3. The outlet 7 b of the fresh air bypass passage 7 is connected to a predetermined location on the downstream side of the throttle valve 33 in the intake passage 3, more specifically, to the surge tank 34. On the fresh air bypass passage 7, a bypass valve 71 serving as a flow rate adjusting valve for controlling the flow rate of fresh air is provided. In the present embodiment, the fresh air bypass passage 7 also has a function as a bypass passage for introducing fresh air into the cylinder 1 during idle operation, and the amount of fresh air introduced by the bypass valve 71 during idle operation is reduced. It also has a function as an ISC valve for adjustment.

  The bypass valve 71 incorporates at least a valve body 711, a valve seat 712a on which the valve body 711 is seated when the valve is closed, and a driving device 712b such as a stepping motor for driving the valve body 711, and an inflow port opened upstream. 712x and a housing 712 provided with an outflow port 712y opened on the downstream side. The bypass valve 71 operates when the drive device 712 receives an opening operation signal l from an ECU (Electronic Control Device) 6 described later. More specifically, the amount of air passing through the bypass valve 71 is controlled by the distance of advancement / retraction of the valve body 711 according to the duty ratio of the pulse current (or voltage) input to the solenoid as the opening operation signal l. This is done by changing An intake pressure sensor 8, which is a pressure sensor that measures the pressure of air flowing through the intake passage 3, is provided on the downstream side of the bypass valve 71 and on the upstream side of the outlet 7 b of the fresh air bypass passage 7.

  The ECU 6 that controls the operation of the internal combustion engine 0 is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like. The input interface outputs a vehicle speed signal a output from a vehicle speed sensor that detects the vehicle speed, a rotation speed signal b output from a rotation speed sensor that detects the engine rotation speed, and an accelerator sensor that detects the amount of depression of the accelerator pedal. The accelerator opening request signal c, the intake pressure signal d output from the intake pressure sensor 8 that detects the intake pressure (supercharging pressure), and the intake air temperature signal e that is output from the temperature sensor that detects the intake temperature of the surge tank 34 The IDL signal f output from the idle switch for detecting the open / close state of the throttle valve 33 is input. From the output interface, the fuel injection signal g for the injector 11, the ignition signal h for the ignition plug (ignition coil), the opening operation signal i for the EGR valve 22, and the opening degree for the intake throttle valve 35. An opening operation signal k is output to the operation signal j, the throttle valve 33, and an opening operation signal l is output to the bypass valve 71 (drive device 712). The ECU 6 has a function as a control device in claims.

  The processor of the ECU 6 interprets and executes a program stored in the memory in advance, and controls the operation of the internal combustion engine 0. The ECU 6 obtains various information a, b, c, d, e, and f necessary for operation control of the internal combustion engine 0 via the input interface, and based on them, the intake air amount, the required fuel injection amount, the ignition timing, the request EGR amount, target idle speed, etc. are calculated. Then, various control signals g, h, i, j, k, and l corresponding to the calculation result are applied through the output interface.

  Here, in the idle operation state, the ECU 6 performs the idle rotation speed control that causes the bypass valve 71 to function as an ISC valve as described above and converges the rotation speed to the target idle rotation speed. This idle speed control is performed in the same manner as the conventionally known idle speed control. That is, when the engine speed indicated by the speed signal b exceeds the target idle speed, the opening degree of the bypass valve 71 is increased and the fuel injection amount is increased so that more air-fuel mixture is introduced into the cylinder 1. When the engine speed indicated by the rotation speed signal b is lower than the target idle speed, the opening degree of the bypass valve 71 is reduced and the fuel injection amount is reduced to reduce the amount of air-fuel mixture introduced into the cylinder 1. Control.

  According to the configuration of the present embodiment, the intake pressure sensor 8 can be cleaned using the flow of fresh air every time fresh air flows through the fresh air bypass passage 7, so that a large amount of EGR gas is discharged from the cylinder. The deterioration due to the soot contained in the EGR gas of the intake pressure sensor 8 can be suppressed without providing a filter in the intake passage 3 while being introduced into the combustion chamber in 1. Further, since the intake pressure sensor 8 is provided in the fresh air bypass passage 7 deviated from the flow of the intake air including the EGR gas, the deterioration of the intake pressure sensor 8 due to the soot contained in the EGR gas can be suppressed also from this point. .

  Further, since the ECU 6 that performs idle speed control by adjusting the opening degree of the bypass valve 71 is provided, the intake pressure sensor 8 can be cleaned each time the idle operation is performed. Therefore, it is possible to more effectively suppress the deterioration due to the dirt of the intake pressure sensor 8. Furthermore, by cleaning the intake pressure sensor 8 during idling when the driver is not performing driving operation, fresh air flows into the cylinder 1 through the fresh air bypass passage 7 regardless of the driver's intention. As a result, the fuel injection amount and the engine speed increase, and the occurrence of a problem that makes the driver feel uncomfortable can be suppressed.

  The present invention is not limited to the embodiment described above.

  For example, as shown in FIG. 3, a sub chamber A72 communicating with the hole 3a provided in the intake passage 3 is provided in a portion adjacent to the downstream side of the throttle valve 33, and the fresh air bypass passage 7 is connected to the sub chamber A72. In addition, an aspect in which an intake pressure sensor 8 for measuring the pressure in the sub chamber A72 is provided can be considered.

  Further, as shown in FIG. 4, a sub chamber B73 communicating with the internal space of the surge tank 34 through a hole provided in the surge tank 34 is integrally provided on the outer wall of the surge tank 34. It is conceivable to provide an intake pressure sensor 7 for connecting the air bypass passage 7 and measuring the pressure in the sub chamber B73.

  In addition, in description of the embodiment which concerns on FIG.3 and FIG.4, each part other than subchamber A72, B73 is attached | subjected with the same name and code | symbol as the thing in embodiment mentioned above. Further, the internal combustion engine of each embodiment described above with reference to FIGS. 3 and 4 is the embodiment described above except that the attachment position of the intake pressure sensor 8 is different and that the sub chambers A72 and B73 are provided. The internal combustion engine 0 in FIG.

  Even in these modes, the sub chamber is located outside the air flow including the EGR gas in the intake passage, and fresh air is introduced into the sub chamber when the bypass valve (flow control valve) is opened. The intake pressure sensor provided in the sub chamber is not easily contaminated by soot, and the intake pressure sensor can be cleaned by the flow of fresh air. Therefore, deterioration of the intake pressure sensor due to soot contained in the EGR gas can be suppressed.

  In addition, at the time of deceleration request, that is, fuel cut control accompanying a decrease in the amount of operation of the accelerator pedal, the bypass valve is temporarily opened so that air that does not contain EGR gas is taken into the cylinder via the fresh air bypass passage. Also good. Since the opening of the throttle valve is reduced during deceleration, the pressure in the surge tank becomes negative, and by performing such control, the air flows through the fresh air bypass passage at a high speed just by opening the bypass valve. It becomes possible to clean the pressure sensor efficiently.

  The inlet of the fresh air bypass passage may be connected to any location as long as it is upstream of the outlet of the EGR passage, and the outlet of the fresh air bypass passage may be downstream of the throttle valve in the intake passage. For example, you may connect to arbitrary places.

  In addition, various changes may be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 0 ... Internal combustion engine 2 ... EGR passage 22 ... EGR valve 3 ... Intake passage 33 ... Throttle valve 4 ... Exhaust passage 51 ... Compressor 52 ... Drive turbine (turbine)
7 ... Fresh air bypass passage 71 ... Bypass valve (flow control valve)
8 ... Intake pressure sensor (pressure sensor)

Claims (2)

A turbine provided in the exhaust passage;
A compressor provided in the intake passage and driven by the turbine;
A low-pressure loop exhaust gas recirculation device in which an EGR valve is provided on an EGR passage connecting the downstream side of the turbine in the exhaust passage and the upstream side of the compressor in the intake passage;
A throttle valve provided on the downstream side of the compressor in the intake passage;
A fresh air bypass passage connecting the upstream side of the outlet of the EGR passage in the intake passage and the downstream side of the throttle valve;
A flow rate adjusting valve provided in the fresh air bypass passage for controlling the flow rate of fresh air;
An internal combustion engine comprising: a pressure sensor provided between the flow rate adjusting valve and the outlet in the fresh air bypass passage. The internal combustion engine according to claim 1, further comprising a control device that performs idle speed control by adjusting an opening of the flow rate adjusting valve.

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