JP5574922B2 - Internal combustion engine - Google Patents

Description

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

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 exhaust gas generated by combustion into intake air.

  For the 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, the low-temperature and low-pressure exhaust gas that has passed through the turbine of the exhaust turbocharger and the exhaust gas purification catalyst enters the intake passage. A low-pressure loop EGR that recirculates (see, for example, Patent Document 1 below) is advantageous in that a large amount of EGR gas can be mixed into the intake air.

  When the internal combustion engine is idle, the EGR valve is fully closed to stop the EGR completely. When the driver makes an acceleration request to depress the accelerator pedal during idling, it is necessary to increase the intake air amount quickly and increase the amount of EGR gas mixed into the intake air.

  However, 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. That is, the EGR gas that has merged from the EGR passage to the intake passage reaches the cylinder through a long route that passes through the compressor, the throttle valve, the surge tank, and the intake manifold.

  Therefore, even when the EGR valve is opened in response to an acceleration request, the path from the downstream of the EGR valve to the cylinder is filled with air (fresh air) that does not contain EGR gas, and the EGR gas immediately enters the cylinder. Not supplied. Therefore, the increase in the EGR rate of intake air is delayed, which may cause deterioration of fuel consumption.

  Although it is conceivable to increase the internal EGR rate during acceleration by changing the opening / closing timing (valve timing) of the intake / exhaust valve, it may lead to a decrease in drivability. In addition, since the internal EGR gas has a higher temperature than the external EGR gas, relying on this may induce knocking. If the ignition timing is retarded to prevent knocking, the engine output torque is suppressed against the acceleration request.

JP 2007-2111767 A

  The present invention has been made by paying attention to the above-mentioned event for the first time, and an object of the present invention is to eliminate the delay of EGR control when shifting from the idle state to acceleration.

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 downstream side of the turbine in the exhaust passage and the upstream side of the compressor in the intake passage are connected. A low-pressure loop exhaust gas recirculation device in which an EGR valve is provided in the EGR passage; an intake throttle valve provided upstream of the connection portion of the EGR passage in the intake passage; and the compressor in the intake passage A throttle valve provided downstream, a bypass passage connecting the upstream side of the intake throttle valve and the downstream side of the throttle valve in the intake passage, a bypass valve provided in the bypass passage, and an idle state The EGR valve is opened, and on the path from the downstream of the EGR valve to the upstream of the throttle valve The EGR valve is throttled or fully closed after elapse of a required time for confining and storing EGR gas, the throttle valve is throttled or fully closed, the intake throttle valve is fully closed, and the bypass valve An internal combustion engine comprising a control unit that performs an operation of opening the engine is configured.

  That is, during idling, the EGR gas is confined and stored on the path from the downstream of the EGR valve to the upstream of the throttle valve while supplying air to the cylinder via the bypass passage. If this is the case, it is possible to quickly supply EGR gas to the cylinder and increase the intake EGR rate by opening the throttle valve when acceleration is requested.

  According to the present invention, the delay of EGR control at the time of transition from the idle state to acceleration can be effectively eliminated.

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 the example of a procedure of the process which the control part in the embodiment performs.

  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 external EGR passage 2 that recirculates the EGR gas 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 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.

  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 low pressure loop EGR. The pressure loss in the low-pressure loop EGR passage 2 is as small as several hundred Pa. The inlet of the external EGR passage 2 is connected to a predetermined location downstream of the three-way catalyst 41 in the exhaust passage 4. The outlet of the external EGR passage 2 is connected to a predetermined location in the intake passage 3 downstream of the intake throttle valve 35 and upstream of the compressor 51. An EGR cooler 21 and an EGR valve 22 are provided on the external EGR passage 2.

  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 of the EGR passage 2 is reduced to a negative pressure by restricting the intake throttle valve 35 upstream of the outlet of the EGR passage 2. 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 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 of the bypass passage 7 is connected to a predetermined location upstream of the intake throttle valve 35 in the intake passage 3. The outlet of the bypass passage 7 is connected to a predetermined location (which may be a surge tank 34) downstream of the throttle valve 33 in the intake passage 3. A bypass valve 71 is provided on the bypass passage 7.

  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 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. An accelerator opening request signal c, an intake pressure signal d output from a pressure sensor for detecting intake pressure (supercharging pressure) in the surge tank 34, and an intake pressure output from a temperature sensor for detecting the intake temperature of the surge tank 34 The temperature signal e and the like are input. 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 degree for the intake throttle valve 35. An opening operation signal j is output to the operation signal i and the throttle valve 33, and an opening operation signal k is output to the bypass valve 71.

  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 acquires various information a, b, c, d, and e 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, and the required EGR amount And so on. Then, various control signals f, g, h, i, j, and k corresponding to the calculation result are applied through the output interface.

  In addition, according to the present embodiment, EGR gas is stored in the intake passage 3 by performing a predetermined operation during idle operation, and then the EGR rate of the gas filled in the cylinder 1 is quickly determined when an acceleration request is received. I try to increase it.

  FIG. 2 shows a procedure of processing executed by the ECU 6 serving as the control unit. When the ECU 6 determines to shift to idle operation (step S1), the ECU 6 opens the EGR valve 22 (step S2), and after the required time has elapsed from the opening (step S3), the EGR valve 22 is opened. The degree is narrowed or fully closed (step S5). In step S1, for example, on the condition that the amount of depression of the accelerator pedal is 0 or less than a threshold value close to 0 and the engine speed is equal to or less than a predetermined speed (return speed at which fuel cut is finished), Judged to enter.

  Further, after a predetermined time has elapsed since the EGR valve 22 was opened (step S3), the throttle valve 33 is throttled or fully closed (step S4), and the intake throttle valve 35 is fully closed (step S4). S6). By these operation steps S2 to S6, the EGR gas is filled in the range from the downstream of the EGR valve 22 to the upstream of the throttle valve 33 in the intake passage 3, and the required EGR rate at the time of re-acceleration can be achieved immediately after the end of idle operation. Like that.

  During the idling operation, the opening amount of the bypass valve 71 is manipulated to adjust the intake air amount, and the fuel injection amount and / or the ignition timing are also adjusted, so that the engine speed is set to the target idle speed (usually 700 rpm or less). Feedback control to about 800 rpm). For this purpose, the bypass valve 71 that has been fully closed is opened almost simultaneously with steps S4 to S6 (step S7).

  Thus, when it is determined that the operation is to be shifted from the idle operation to the acceleration operation (step S9), the fully closed intake throttle valve 35 and throttle valve 33 are opened (steps S10 and S11). In step S9, for example, it is determined that the idling operation is ended and the reacceleration is started on the condition that the accelerator pedal is depressed by the driver. If there is no acceleration request, it goes without saying that the rotational speed control for idle operation is continued (step S8). In step S11, the opening degree of the throttle valve 33 is gradually increased and the EGR gas confined on the path from the downstream side of the EGR valve 22 to the upstream side of the throttle valve 33 in the intake passage 3 is immediately transferred to the cylinder 1. Inflowing into the combustion chamber is suppressed. Otherwise, excessive EGR may cause misfire.

  At the same time as steps S10 and S11, the bypass valve 71 is fully closed (step S12). In step S12, the opening degree of the bypass valve 71 is gradually reduced.

  Incidentally, the bypass passage 7 also functions to prevent misfire during deceleration of the vehicle. When the driver requests to decelerate to depress the accelerator pedal, it is necessary to reduce the amount of EGR gas mixed into the intake air as the intake air amount decreases. However, even if the EGR valve 22 is closed, a considerable amount of EGR gas remains on the path from the downstream side of the EGR valve 22 to the cylinder 1, and it is difficult to immediately reduce the EGR rate to zero. There was a problem.

  Therefore, when a deceleration request is made, the bypass valve 71 is temporarily opened to take in air that does not contain EGR gas via the bypass passage 7 and effectively reduce the EGR rate of the gas filled in the cylinder 1. Therefore, misfire due to excessive EGR is prevented. Since the opening of the throttle valve 33 is reduced during deceleration, the pressure in the surge tank 34 becomes negative, and air can be circulated through the bypass passage 7 simply by opening the bypass valve 71.

  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 downstream side of the turbine 51 in the exhaust passage 4, and the intake passage 3 A low-pressure loop exhaust gas recirculation device in which an EGR valve 22 is provided in the EGR passage 2 that connects the upstream side of the compressor 51, and an upstream side of the connection location of the EGR passage 2 in the intake passage 3 An intake throttle valve 35 provided; a throttle valve 33 provided on the downstream side of the compressor 51 in the intake passage 3; an upstream side of the intake throttle valve 35 in the intake passage 3; and a downstream side of the throttle valve 33. A bypass passage 7 connecting to the bypass passage 71, a bypass valve 71 provided in the bypass passage 7, and an idle state The EGR valve 22 is opened, and then the EGR valve 22 is throttled or fully closed, the throttle valve 33 is throttled or fully closed, the intake throttle valve 35 is fully closed, and the bypass valve 71 is closed. Since the internal combustion engine 0 including the control unit 6 that performs the opening operation is configured, air is supplied from the EGR valve 22 to the upstream of the throttle valve 33 while supplying air to the cylinder 1 via the bypass passage 7 during idle operation. The EGR gas can be confined and stored on the path. Then, when the acceleration is requested, the throttle valve 33 can be opened to quickly supply the stored EGR gas to the cylinder 1 and increase the EGR rate of the intake air.

  According to the present embodiment, it is possible to effectively solve the problem that the EGR rate does not immediately increase even when the EGR valve 22 is opened when shifting from idle operation to acceleration operation. Therefore, it is effective in improving fuel consumption and can prevent occurrence of knocking and the like. The actual intake EGR rate can be quickly converged to the required EGR rate, that is, the responsiveness of the control of the external EGR rate can be improved, so that it does not depend on the internal EGR. The degree of freedom of variable valve timing is also improved.

  The present invention is not limited to the embodiment described in detail above. The specific configuration 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 3 ... Intake passage 33 ... Throttle valve 35 ... Intake throttle valve 4 ... Exhaust passage 5 ... Supercharger 51 ... Compressor 6 ... Control part (ECU)
7 ... Bypass passage 71 ... Bypass valve

Claims (1)

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 in 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;
An intake throttle valve provided on the upstream side of the connection portion of the EGR passage in the intake passage;
A throttle valve provided on the downstream side of the compressor in the intake passage;
A bypass passage connecting the upstream side of the intake throttle valve and the downstream side of the throttle valve in the intake passage;
A bypass valve provided in the bypass passage;
When transitioning to the idle state, the EGR valve is opened, and after a predetermined time for confining and storing EGR gas on the path from the downstream of the EGR valve to the upstream of the throttle valve , the EGR valve is throttled or fully closed. And a control unit that performs an operation of closing or fully closing the throttle valve, fully closing the intake throttle valve, and opening the bypass valve.

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