JP2016011656A - Internal combustion engine starting auxiliary device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively estimate a sensor output value reflecting a response delay of a temperature sensor in relation to a sensor output value estimation device.SOLUTION: An internal combustion engine starting auxiliary device comprises: an intake passage 11 introducing intake air into a combustion chamber of an engine 10; an exhaust passage 12 discharging exhaust gas from the combustion chamber; an exhaust gas recirculation passage 21 branched off from the exhaust passage 12 and merged with the intake passage 11; an EGR valve 23 provided in the exhaust gas recirculation passage 21; an exhaust gas shutter 17 provided in the exhaust passage 12; an intake throttle valve 14 provided in the intake passage 11; a variable valve gear mechanism 30 capable of arbitrarily adjusting valve opening/closing timing of an exhaust valve EV; and a control unit 40 increasing a degree of opening of the EGR valve 23 and decreasing a degree of opening of the exhaust gas shutter 17 and the intake throttle valve 14 and controlling the variable valve gear mechanism 30 to advance the valve opening timing of the exhaust valve EV at a time of starting the engine 10.

Description

  The present invention relates to a start assist device for an internal combustion engine, and more particularly to a start assist at a low temperature start.

  In a diesel engine, which is a compression ignition type internal combustion engine, by reducing the compression ratio, it is possible to reduce the maximum in-cylinder pressure and to suppress the generation of NOx (nitrogen oxide) which is a harmful substance in exhaust gas. is there. On the other hand, since the compression end temperature decreases as the compression ratio decreases, there is a problem that the fuel injected into the combustion chamber is difficult to ignite, particularly at low temperature start, and startability is deteriorated. Under low-temperature environments, the temperature of the intake air and the engine itself is low, and further, the temperature in the combustion chamber cannot be sufficiently increased during the compression stroke due to the low compression ratio.

  As a technique for improving the deterioration of the startability, for example, Patent Document 1 discloses that the ignition performance of the fuel is improved by driving the electric supercharger during the cold start to raise the temperature in the combustion chamber. Is disclosed.

JP 2005-188484 A

  By the way, in an extremely cold environment where the outside air temperature is below the freezing point (for example, −20 ° C. or lower), the combustion chamber cannot be sufficiently heated only by supercharging by the electric supercharger, and reliable start-up cannot be ensured. there is a possibility. In recent years, the ignitability has been improved by increasing the temperature of the glow plug. However, in low temperature environments, the internal resistance of the battery has increased, and sufficient power cannot be supplied to the glow plug. May not be successful.

  An object of the present invention is to provide a start assist device for an internal combustion engine that can effectively improve startability even in a low temperature environment.

  In order to achieve the above-described object, a sensor output value estimation device according to the present invention includes an intake passage for introducing intake air into a combustion chamber of a compression ignition internal combustion engine, an exhaust passage for deriving exhaust gas from the combustion chamber, and the exhaust passage An exhaust gas recirculation passage that branches off from the exhaust gas and joins the intake air passage, a first valve that is provided in the exhaust gas recirculation passage and can adjust the exhaust gas recirculation amount, and a downstream portion of the branch portion of the exhaust gas recirculation passage A second valve which is provided in the exhaust passage on the side and can adjust the exhaust flow rate, and a third valve which is provided in the intake passage on the upstream side of the junction with the exhaust recirculation passage and can adjust the intake flow rate A variable valve mechanism that can arbitrarily adjust the opening / closing timing of the exhaust valve of the internal combustion engine, and when the internal combustion engine is started, the opening of the first valve is increased and the second and third valves are opened. And the variable valve gear And a control unit for advancing the open-starting timing of the exhaust valve by.

  Further, it is preferable that the control unit fully opens the first valve when the internal combustion engine is started.

  Further, it is preferable that the control unit fully closes the opening degree of the second and third valves when the internal combustion engine is started.

  According to the start assist device for an internal combustion engine of the present invention, startability can be effectively improved even in a low temperature environment.

It is a schematic block diagram which shows an example of the intake / exhaust system of the diesel engine which concerns on one Embodiment of this invention. It is a figure explaining the advance angle of the exhaust valve by the starting auxiliary device which concerns on one Embodiment of this invention. It is a flowchart explaining the control content by the starting auxiliary device which concerns on one Embodiment of this invention.

  Hereinafter, an internal combustion engine start assist device according to an embodiment of the present invention will be described with reference to the accompanying drawings. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  FIG. 1 is a schematic configuration diagram showing an example of an intake and exhaust system of a diesel engine (hereinafter simply referred to as an engine) 10 according to the present embodiment. In FIG. 1, symbol CB indicates a cylinder block, symbol CH indicates a cylinder head, symbol IJ indicates an injector, symbol IV indicates an intake valve, and symbol EV indicates an exhaust valve.

  An intake passage 11 for introducing intake air into the combustion chamber is connected to the intake manifold 10A. In this intake passage 11, an air cleaner 13, an intake throttle valve 14, a turbocharger compressor 15 </ b> A, an intercooler 16, and the like are provided in order from the intake upstream side. The intake throttle valve 14 is preferable as an example of the third valve of the present invention.

  An exhaust passage 12 through which exhaust is led out from the combustion chamber is connected to the exhaust manifold 10B. The exhaust passage 12 is provided with a turbocharger turbine 15B, an exhaust shutter 17 and the like in order from the exhaust upstream side. The exhaust shutter 17 is preferable as an example of the second valve of the present invention.

  The exhaust gas recirculation device 20 includes an EGR passage 21 that circulates a part of the exhaust gas to the intake passage 11, an EGR cooler 22 that cools the EGR gas, and an EGR valve 23 that adjusts the EGR gas flow rate. The EGR valve 23 is preferable as an example of the first valve of the present invention.

  The engine 10 of this embodiment includes a variable valve timing mechanism 30 that can set the opening / closing timing of the exhaust valve EV to an arbitrary timing. As the variable valve timing mechanism 30, for example, a known vane variable valve timing mechanism that continuously varies the opening / closing timing of the exhaust valve EV by adjusting the hydraulic pressure can be used. The variable valve timing mechanism 30 is not limited to the vane type, and other known variable valve mechanisms may be used.

  The cooling water temperature sensor 31 detects the temperature of cooling water flowing through a cooling water circulation path (not shown). The engine rotation sensor 32 detects the rotation speed (engine rotation speed) of a crankshaft (not shown). The outside air temperature sensor 33 detects the outside air temperature. Sensor values detected by these various sensors 31 to 33 are transmitted to an electrically connected electronic control unit (hereinafter referred to as ECU) 40.

  The ECU 40 performs various controls of the engine 10 and includes a known CPU, ROM, RAM, input port, output port, and the like. Further, the ECU 40 executes start assist control that assists the start of the engine 10 at the time of low temperature start. Specifically, when the sensor value of the cooling water temperature sensor 31 (or the outside air temperature sensor 33) indicates a predetermined low temperature state, the EGR valve 23 is fully opened simultaneously with cranking by a starter motor (not shown), and the exhaust shutter. 17 and the intake throttle valve 14 are controlled to be fully closed. As a result, the unburned gas in the combustion chamber whose temperature has been raised in the compression stroke is discharged to the exhaust passage 12 in the exhaust stroke, and is further re-introduced into the combustion chamber in the intake stroke from the EGR passage 21 through the intake passage 11. Circulation takes place.

  However, only with this exhaust gas recirculation, the unburned gas raised in the compression stroke is lowered in the expansion stroke, so that there is a possibility that ignition will not occur even if fuel is injected from the injector IJ into the combustion chamber. Therefore, the ECU 40 instructs the variable valve timing mechanism 30 to advance the opening timing of the exhaust valve EV to the compression top dead center TDC side (for example, the intermediate position of the expansion stroke) as shown in FIG. Send a signal. As a result, the unburned gas whose temperature has been raised in the compression stroke is discharged to the exhaust passage 12 before the temperature is lowered in the expansion stroke, and is again introduced from the EGR passage 21 into the combustion chamber through the intake passage 11. It becomes like this. As a result, the temperature increase in the combustion chamber is effectively promoted, and the engine 10 can be reliably started successfully.

  The advance amount of the exhaust valve EV is not limited to a fixed value. For example, according to the sensor value of the outside air temperature sensor 33 or the cooling water temperature sensor 31, the advance amount is increased as the sensor value decreases. May be.

  Next, based on FIG. 3, the control flow by the starting assistance apparatus according to the present embodiment will be described. Note that. This control starts when an unillustrated engine switch is operated to the ignition on position.

  In step S10, it is determined whether or not it is a cold start based on the sensor value of the coolant temperature sensor 31 (or the outside air temperature sensor 33). If it is during cold start (Yes), the control proceeds to step S20. On the other hand, when it is not during the cold start (No), normal start control, that is, cranking is performed by a starter motor (not shown) in response to starter on, and normal control is started to start fuel injection from the injector IJ.

  In step S20, it is determined whether or not the engine switch has been operated to the starter on position. If the starter is on (Yes), the process proceeds to step S30 and cranking by the starter motor is started.

  In step S40, the EGR valve 23 is fully opened and the exhaust shutter 17 and the intake throttle valve 14 are fully closed. Further, in step S50, the opening timing of the exhaust valve EV is advanced to the compression top dead center side than normal. Is done. These steps S30-50 are performed simultaneously. When the temperature in the combustion chamber rises to the fuel ignition temperature, the present control proceeds to step S60, starts fuel injection by the injector IJ, and then returns.

  Next, the function and effect of the start assist device according to this embodiment will be described.

  The start assist device of the present embodiment fully opens the EGR valve 23, fully closes the exhaust shutter 17 and the intake throttle valve 14 at the time of low temperature start, and advances the valve opening timing of the exhaust valve EV more than usual. That is, the unburned gas heated in the compression stroke is discharged to the exhaust passage 12 before the temperature is lowered in the expansion stroke, and is introduced again into the combustion chamber from the EGR passage 21 through the intake passage 11. A high-temperature gas is continuously supplied to the combustion chamber. Therefore, according to the start assist device of the present embodiment, the temperature increase of the combustion chamber is effectively promoted even in a low temperature environment, and the engine 10 can be reliably started.

  In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably and can implement.

10 Diesel Engine 11 Intake Passage 12 Exhaust Passage 14 Intake Throttle Valve (Third Valve)
17 Exhaust shutter (second valve)
21 EGR passage 23 EGR valve (first valve)
30 Variable valve timing mechanism 40 ECU

Claims (3)

An intake passage for introducing intake air into a combustion chamber of a compression ignition internal combustion engine;
An exhaust passage for leading exhaust from the combustion chamber;
An exhaust recirculation passage that branches off from the exhaust passage and joins the intake passage;
A first valve provided in the exhaust gas recirculation passage and capable of adjusting an exhaust gas recirculation amount;
A second valve that is provided in the exhaust passage downstream of a branching portion with the exhaust recirculation passage and is capable of adjusting an exhaust flow rate;
A third valve provided in the intake passage on the upstream side of the junction with the exhaust recirculation passage and capable of adjusting an intake flow rate;
A variable valve mechanism capable of arbitrarily adjusting the opening and closing timing of the exhaust valve of the internal combustion engine;
When starting the internal combustion engine, the opening degree of the first valve is increased, the opening degrees of the second and third valves are decreased, and the opening timing of the exhaust valve is advanced by the variable valve mechanism. A starting assist device for an internal combustion engine. 2. The start assist device for an internal combustion engine according to claim 1, wherein when the internal combustion engine is started, the control unit fully opens the opening of the first valve. The start assist device for an internal combustion engine according to claim 1 or 2, wherein the control unit fully closes the opening degree of the second and third valves when the internal combustion engine is started.

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