JP5679185B2 - Control device for internal combustion engine - Google Patents

Description

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

  An internal combustion engine equipped with an exhaust turbocharger, equipped with a waste gate valve to adjust the amount of exhaust gas flowing into the turbine by diverting a part of the exhaust gas, thereby obtaining a stable supercharging pressure It has been known.

  Further, in an internal combustion engine equipped with this waste gate valve, the throttle valve opening is fully opened in accordance with the amount of depression of the accelerator pedal, and the waste gate valve opening is controlled so that the target boost pressure is reached during supercharging. Thus, a technique for reducing the pumping loss at the time of supercharging is known (see, for example, Patent Document 1).

On the other hand, lowering 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 the exhaust gas generated by combustion into the intake air, and is generally a high-pressure loop EGR that recirculates the exhaust gas immediately after being exhausted from the cylinder to the intake passage.

  However, if the high-pressure loop EGR is applied to the internal combustion engine that fully opens the throttle valve, the intake pressure exceeds the exhaust pressure at the time of supercharging, and the exhaust gas cannot be recirculated to the intake passage. There is a problem that the effect of the EGR device cannot be expected.

JP-A-5-141258

  An object of the present invention is to improve fuel efficiency in an internal combustion engine with an exhaust turbocharger and a high-pressure loop exhaust gas recirculation device.

  In the present invention, the turbine provided in the exhaust passage, the compressor provided in the intake passage and driven by the turbine, and the upstream side of the turbine in the exhaust passage and the downstream side of the compressor in the intake passage are connected. A high-pressure loop exhaust gas recirculation device in which an EGR valve is provided in the EGR passage; a bypass passage connecting the upstream side and the downstream side of the turbine in the exhaust passage; Control of an internal combustion engine comprising a bypass valve capable of opening control and a throttle valve provided upstream of the exhaust gas recirculation device in the intake passage and capable of opening control independently of the amount of depression of an accelerator pedal A device for forcibly opening the throttle valve opening when detecting an acceleration request, A control of an internal combustion engine characterized by controlling the output by operating a valve and the EGR valve, and at the time of supercharging by the compressor, the opening of the throttle valve is throttled so that the exhaust pressure becomes larger than the intake pressure. Configured the device.

If this is the case, it is possible to reduce the pumping loss by increasing the opening of the throttle valve as much as possible regardless of whether it is non-supercharging or supercharging, and at the time of supercharging, EGR is necessary. under circumstances, the supercharged intake pressure is made smaller than the exhaust pressure allowed to flow back exhaust gases to the intake passage, fuel efficiency by the EGR device, to obtain the emission reduction and knocking prevention effect of the NO _x it can.

  ADVANTAGE OF THE INVENTION According to this invention, a fuel consumption can be improved in the internal combustion engine attached with the exhaust turbo supercharger and the high pressure loop exhaust gas recirculation device.

The figure which shows the structure of the internal combustion engine and exhaust-gas recirculation apparatus in one Embodiment of this invention. The flowchart which shows an example of the control method in the embodiment.

  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. And an external EGR passage 2 that recirculates the exhaust gas.

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

  The exhaust passage 4 guides exhaust generated as a result of burning fuel in the cylinder 1 from the exhaust port of the cylinder 1 to the outside. An exhaust manifold 42, a drive turbine 52 for the supercharger 5, and a three-way catalyst 41 are disposed on the exhaust passage 4. In addition, an exhaust bypass passage 43 that bypasses the turbine 52 and a waste gate valve 44 that is a bypass valve that opens and closes the inlet of the bypass passage 43 are provided. The waste gate valve 44 is an electric waste gate valve that can be opened and closed by inputting a control signal m to the actuator. In this embodiment, a servo motor is used as the actuator.

  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 external EGR passage 2 realizes a so-called high pressure loop EGR. The inlet of the external EGR passage 2 is connected to a predetermined location in the exhaust passage 4 upstream of the three-way catalyst 41 and the turbine 52 and downstream of the exhaust port of the cylinder 1. The outlet of the external EGR passage 2 is connected to the intake passage 3 downstream of the throttle valve 33, specifically to a predetermined location of the surge tank 34. An EGR cooler 21 and an EGR valve 22 are provided on the external EGR passage 2.

  In the high-pressure loop EGR, high-pressure exhaust gas is recirculated to the intake passage 3 through the EGR passage 2. Therefore, when performing EGR, the throttle valve 33 upstream of the outlet of the EGR passage 2 is normally throttled to reduce the pressure around the outlet of the EGR passage 2.

  An ECU (electronic control unit) 6 that controls 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 includes a vehicle speed signal a output from the vehicle speed sensor that detects the vehicle speed, a rotation speed signal b output from the rotation speed sensor that detects the engine rotation speed, and the amount of depression of the accelerator pedal (so-called required load, required output). ) Accelerator opening request signal c output from the accelerator sensor that detects the intake pressure, intake pressure signal d output from the pressure sensor that detects the pressure (supercharging pressure) of the intake air in the surge tank 34, and the intake air temperature of the surge tank 34 An intake air temperature signal e output from the temperature sensor that detects the exhaust gas, a back pressure signal l output from the pressure sensor that detects the pressure of the exhaust gas (before passing through the turbine 52) that flows through the exhaust passage 4, and the like. From the output interface, the fuel injection signal f for the injector 11, the ignition signal g for the ignition plug (ignition coil thereof), the opening operation signal h for the EGR valve 22, and the opening operation for the throttle valve 33. An opening operation signal m and the like are output to the signal j and the waste gate valve 44.

  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 l required for operation control of the internal combustion engine 0 through the input interface, and based on them, the intake air amount, the required fuel injection amount, the ignition timing, the required EGR amount and the like are calculated. Then, various control signals f, g, h, j, m corresponding to the calculation result are applied via the output interface.

  In the present embodiment, when the acceleration request is detected, that is, when the accelerator pedal is depressed by the driver, the opening of the throttle valve 33 is forcibly opened regardless of the depression amount of the accelerator pedal. The opening degree of the waste gate valve 44 and / or the EGR valve 22 is operated so that the cylinder 1 can be filled with a fresh air amount and an EGR gas amount corresponding to the load.

  Further, in the operation region where EGR is required at the time of supercharging in which the pressure in the surge tank 34 indicates a positive pressure, the opening degree of the throttle valve 33 is not excessively increased so that the exhaust pressure becomes larger than the intake pressure. The opening degree of the waste gate valve 44 and the EGR valve 22 is manipulated while the throttle is narrower than that during supply.

  FIG. 2 shows a procedure of processing executed by the ECU 6. First, the ECU 6 detects whether there is an acceleration request (step S1). Specifically, it is detected that the driver is stepping on the accelerator pedal based on the accelerator opening request signal c output from the accelerator sensor. While the acceleration request is being made, the waste gate valve 44 and the EGR valve 22 are opened so that the required load and the required EGR rate can be achieved while the throttle valve 33 is opened larger than the opening corresponding to the depression amount of the accelerator pedal. The degree is manipulated (step S3, step S5).

  Further, using a pressure sensor provided in the surge tank 34, it is determined whether the current supercharging region or the non-supercharging region (step S2). More specifically, the intake pressure signal d output from the pressure sensor measures whether the pressure in the surge tank 34 is a positive pressure greater than a predetermined pressure (for example, atmospheric pressure) or a negative pressure smaller than the predetermined pressure. If there is a supercharged area, if it is negative pressure, it is a non-supercharged area.

  If it is in the non-supercharging range, the throttle valve 33 may be fully opened or opened to a predetermined opening close to full opening (step S3). In the memory of the ECU 6, map data defining the relationship between the engine speed and the required load (or intake air amount) and the respective opening degrees of the throttle valve 33, the waste gate valve 44 and the EGR valve 22 is stored in advance. . The map is determined by conformance. The ECU 6 searches this map to know the respective openings of the throttle valve 33, the waste gate valve 44 and the EGR valve 22, and operates these valves 33, 44 and 22.

  On the other hand, when in the supercharging region, the throttle valve 33 cannot always be opened to the predetermined opening. This is because if the supercharging pressure in the surge tank 34 exceeds the exhaust gas pressure in the exhaust manifold 42, the EGR gas cannot be recirculated to the intake system via the EGR passage 2. Therefore, in the supercharging region, it is necessary to control the valves 22, 33, 44 so that the exhaust pressure becomes larger than the intake pressure (step S5).

  That is, the opening degree of the waste gate valve 44 and the EGR valve 22 is manipulated while the opening degree of the throttle valve 33 is narrower than the predetermined opening degree in the non-supercharging region. However, the opening of the throttle valve 33 is nevertheless opened as much as possible. In the memory of the ECU 6, the engine speed and the required load (or intake air amount) and the opening amounts of the throttle valve 33, the waste gate valve 44 and the EGR valve 22 at which the exhaust pressure becomes larger than the intake air pressure are stored in advance. Map data defining the relationship is stored. The map is determined by conformance. The ECU 6 searches this map to know the respective openings of the throttle valve 33, the waste gate valve 44 and the EGR valve 22, and operates these valves 33, 44 and 22.

  If the control of each valve 22, 33, 44 in the supercharging region is specifically described, the EGR valve 22 is controlled so as to achieve the target EGR rate corresponding to the required load, and the exhaust gas enters the surge tank 34. The throttle valve 33 upstream of the outlet of the EGR passage 2 is controlled so as to be slightly throttled from the substantially fully opened state so that it can flow in. As a result, a negative pressure is generated around the outlet of the EGR passage 2 connected to the intake passage 3. This is necessary in order to reduce the pressure around the outlet of the EGR passage 2 to ensure the reflux amount of the external EGR gas.

  Further, it is necessary to adjust the supercharging pressure as the opening of the throttle valve 33 becomes smaller. Therefore, the exhaust gas amount fed into the turbine 52 is adjusted by the waste gate valve 44. The control of the EGR valve 22, the throttle valve 33, and the waste gate valve 44 is executed substantially simultaneously.

  Even in the supercharging region, when the required load is larger than a certain level, the throttle valve 33 is maintained at the predetermined opening. For example, in a region where the target EGR rate is 0 (e.g., when the EGR valve 22 is fully closed), such as during a high demand load and high rotation, there is no need to recirculate exhaust gas to the intake passage 3 side. It is not necessary to control each valve 22, 33, 44 so that becomes greater than the intake pressure (step S4).

  In the present embodiment, the turbine 52 provided in the exhaust passage 4, the compressor 51 provided in the intake passage 3 and driven by the turbine 52, the upstream side of the turbine 52 in the exhaust passage 4, and the intake passage 3 A high-pressure loop type exhaust gas recirculation device in which an EGR valve 22 is provided in the EGR passage 2 connecting the downstream side of the compressor 51, and the upstream side and the downstream side of the turbine 52 in the exhaust passage 4 are connected. A bypass passage 43, a waste gate valve 44 which is a bypass valve provided in the bypass passage 43 and can be electrically controlled, and an accelerator pedal provided upstream of the exhaust gas recirculation device in the intake passage 3. Control device for internal combustion engine 0 provided with throttle valve 33 capable of controlling the opening degree independently of the amount of depression When the acceleration request is detected, the opening of the throttle valve 33 is forcibly opened, and when the supercharging by the compressor 51 is performed, the waste gate valve 44 and / or the EGR valve 22 is operated to control the output. In addition, since the opening of the throttle valve 33 is controlled so that the exhaust pressure becomes larger than the intake pressure, the high-pressure EGR gas can flow into the intake passage 3 even in the supercharging region. It becomes possible. Therefore, the cooling loss can be reduced and the fuel consumption can be improved. Further, by controlling the opening degree of the throttle valve 33 to be more open than the opening degree corresponding to the normal depression amount of the accelerator pedal, the pumping loss can be reduced and the fuel consumption can be improved.

  The present invention is not limited to the embodiment described in detail above. For example, when determining the opening degree of each valve 22, 33, 44 in the supercharging region, the back pressure signal l output from the pressure sensor that detects the pressure of the exhaust gas flowing through the exhaust passage (before passing through the turbine) is also used. It is also possible to refer to the valves 22, 33, and 44 so that the intake pressure in the surge tank 34 is smaller than the back pressure. However, it is advantageous in terms of responsiveness to determine the opening degree of each valve 22, 33, 44 with reference to the map as in the above embodiment.

  Other specific configurations of each part can be variously modified without departing from the spirit of the present invention.

  The present invention can be applied to an internal combustion engine with a supercharger mounted on a vehicle or the like.

DESCRIPTION OF SYMBOLS 0 ... Internal combustion engine 2 ... EGR passage 22 ... EGR valve 3 ... Intake passage 33 ... Throttle valve 4 ... Exhaust passage 43 ... Bypass passage 44 ... Bypass valve (waste gate valve)
51 ... Compressor 52 ... Turbine

Claims (1)

A turbine provided in the exhaust passage;
A compressor provided in the intake passage and driven by the turbine;
A high-pressure loop type exhaust gas recirculation device in which an EGR valve is provided in an EGR passage connecting the upstream side of the turbine in the exhaust passage and the downstream side of the compressor in the intake passage;
A bypass passage connecting the upstream side and the downstream side of the turbine in the exhaust passage;
A bypass valve provided in the bypass passage and electrically openable;
A control device for an internal combustion engine, comprising a throttle valve provided upstream of the exhaust gas recirculation device in the intake passage and capable of opening control independently of an accelerator pedal depression amount;
While controlling the output by operating the bypass valve and the EGR valve while forcibly opening the opening of the throttle valve when an acceleration request is detected,
A control device for an internal combustion engine, wherein an opening of the throttle valve is throttled so that an exhaust pressure becomes larger than an intake pressure at the time of supercharging by the compressor.

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