JP2012067727A - Start auxiliary device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively secure the starting performance of an internal combustion engine even under a low-temperature condition, in a start auxiliary device of the internal combustion engine.SOLUTION: The start auxiliary device of the internal combustion engaged includes: a turbocharger 11 which is provided at an intake passage 10 of an internal combustion engine 30 and performs compression and a temperature rise of intake air at a start; an outside air temperature detection means 15 for detecting an outside air temperature; a compressed intake air return passage 13 for returning a part of compressed intake air fed out of the turbocharger 11 at the start to an intake air passage 10 on the upstream side from the turbocharger 11; and a return ratio adjusting means 14 for adjusting the return ratio of the compressed intake air returned by the compressed intake air return passage 13 at the start according to the detection value of the outside air temperature detection means 15.

Description

  The present invention relates to an internal combustion engine start assist device, and more particularly to an internal combustion engine start assist device having a supercharger that compresses and heats intake air when the internal combustion engine is started.

  2. Description of the Related Art Conventionally, as a start assist device for an internal combustion engine such as a diesel engine (hereinafter referred to as an engine), a technique for raising the temperature of intake air at the start with a heater provided in the intake system is known in order to improve startability at the time of engine start. ing. Also known is a technique for improving engine startability by reducing the start torque by narrowing the intake throttle provided in the intake passage at the time of start (for example, Patent Document 1).

Japanese Patent No. 2704650

  In recent years, engine downsizing has been performed from the viewpoint of improving the thermal efficiency of the engine. In general, downsizing of an engine requires an engine having a small displacement and an output equivalent to that of a large displacement engine, so that the engine inevitably becomes highly supercharged. Therefore, when the downsizing of the engine is promoted, the degree of supercharging of the engine is increased and the maximum in-cylinder pressure is increased, but it is necessary to reduce the compression ratio of the engine from the viewpoint of durability.

  However, if the compression ratio of the engine is lowered, the in-cylinder temperature of the engine is lowered, so that the startability of the engine may be deteriorated particularly under a low temperature condition (for example, below freezing point such as minus 25 ° C.).

  The present invention has been made in view of these points, and an object thereof is to provide an internal combustion engine start assist device that can effectively ensure the startability of the internal combustion engine even under low temperature conditions. .

  In order to achieve the above object, an internal combustion engine start assist device according to the present invention is provided in an intake passage of an internal combustion engine and compresses and raises intake air when the internal combustion engine is started, and an external device that detects an outside air temperature. A temperature detecting means, a compressed intake air recirculation passage for returning a part of the compressed intake air sent from the supercharger to the intake passage upstream of the supercharger when starting the internal combustion engine, and the compressed intake air A recirculation rate adjusting means that is provided in the recirculation passage and adjusts the recirculation rate of the compressed intake air recirculated by the compressed intake air recirculation passage according to the detected value of the outside air temperature detecting means when the internal combustion engine is started. Features.

  In addition, a turbocharger that is driven by exhaust from the internal combustion engine and an intercooler that cools the intake air compressed by the turbocharger, and the intake passage is a bypass passage that bypasses the intercooler. Also good.

  The supercharger may be a supercharger driven by the internal combustion engine via an electromagnetic clutch.

  The reflux rate adjusting means may set the reflux rate to 10% when the detected value of the outside air temperature detecting means is minus 25 ° C.

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

1 is a schematic overall configuration diagram showing a start assist device for an internal combustion engine according to an embodiment of the present invention. It is a flowchart which shows the control content by the starting auxiliary device of the internal combustion engine which concerns on one Embodiment of this invention. It is a figure which shows the relationship between the supercharger rotation frequency by the starting auxiliary device of the internal combustion engine which concerns on one Embodiment of this invention, and intake air temperature rise. It is a figure which shows the relationship between the intake manifold inlet temperature by the starting auxiliary device of the internal combustion engine which concerns on one Embodiment of this invention, and the cylinder maximum temperature.

  Hereinafter, an embodiment according to the present invention will be described with reference to FIGS.

  FIG. 1 is an overall configuration diagram showing an internal combustion engine start assist device 1 according to an embodiment of the present invention. 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.

  As shown in FIG. 1, an internal combustion engine (hereinafter referred to as an engine) 30 such as a diesel engine is provided with an intake manifold 31 and an exhaust manifold 32. The intake manifold 31 is connected to a first intake passage 34 for introducing intake air sent from a turbocharger 33 described later by opening an intake valve (not shown), and the exhaust manifold 32 is connected to an exhaust valve (not shown). A first exhaust passage 35 for discharging exhaust gas by opening the valve (shown) is connected.

  As shown in FIG. 1, an intercooler 38 that cools the intake air sent from the turbocharger 33 by heat exchange with cooling water is interposed in the first intake passage 34. A switching valve 39 for switching the intake air flow path is provided in a first intake passage 34 between a bypass passage 10 and an intercooler 38 described later. The opening / closing drive of the switching valve 39 is controlled by an ECU 20 described later.

  As shown in FIG. 1, the turbocharger 33 includes a compressor 33 a provided on the upstream side of the first intake passage 34 and a turbine 33 b provided on the downstream side of the first exhaust passage 35. The compressor 33a is connected to a second intake passage 36 for introducing fresh air via an air cleaner (not shown), and a second exhaust passage 37 for sending exhaust to an exhaust purification device (not shown) downstream of the turbine 33b. It is connected. That is, the turbocharger 33 drives the turbine 33b with the exhaust energy from the engine 30, and compresses fresh air introduced from the air cleaner through the second intake passage 36 by the compressor 33a provided coaxially. It is configured to send to 30.

  Next, the start assist device 1 according to the present embodiment will be described. As shown in FIG. 1, the start assist device 1 includes a bypass passage (intake passage) 10, a supercharger (supercharger) 11, an electromagnetic clutch 12, a compressed intake recirculation passage 13, a bypass valve 14, An air temperature sensor (outside air temperature detecting means) 15 and an ECU 20 are provided. In the present embodiment, the bypass valve 14 and a bypass valve control unit 22 of the ECU 20 to be described later constitute a reflux rate adjusting means of the present invention.

  As shown in FIG. 1, the bypass passage 10 has one end connected to the first intake passage 34 between the compressor 33a and the intercooler 38 and the other end connected to the intercooler 38 and the intake manifold so as to bypass the intercooler 38. 31 is connected to a first intake passage 34 between them.

  The supercharger 11 is a positive displacement mechanical supercharger, and is interposed in the bypass passage 10 as shown in FIG. The supercharger 11 is rotationally driven via an electromagnetic clutch 12 by a crankshaft (not shown) of the engine 30.

  As shown in FIG. 1, the electromagnetic clutch 12 is provided between the crankshaft and the supercharger 11. The electromagnetic clutch 12 is connected to the ECU 20 via electric wiring. That is, when the electromagnetic clutch 12 is controlled to be turned on by the ECU 20 and the supercharger 11 is operated, the intake air that is sent from the compressor 33a of the turbocharger 33 and flows into the bypass passage 10 is compressed and heated by the supercharger 11 and then the engine 30. Supplied to.

  As shown in FIG. 1, the compressed intake recirculation passage 13 has one end connected to the bypass passage 10 located downstream of the supercharger 11 and the other end connected to the bypass passage 10 located upstream of the supercharger 11. It is connected.

  As shown in FIG. 1, the bypass valve 14 is provided in the compressed intake air recirculation passage 13 and adjusts the recirculation rate of the compressed intake air sent from the supercharger 11. The opening degree of the bypass valve 14 is controlled by a bypass valve control unit 22 of the ECU 20.

  The outside air temperature sensor 15 detects the outside air temperature and outputs it to the ECU 20, and is connected to the ECU 20 via an electrical wiring as shown in FIG.

  The ECU 20 performs various controls such as a fuel injection period and a fuel injection amount according to the operating state of the engine 30, and includes a known CPU, ROM, RAM, input port, output port, and the like. In order to perform these various controls, the output signals of various sensors such as an outside air temperature sensor 15, an accelerator sensor (not shown), and an engine speed sensor (not shown) are input to the ECU 20 after A / D conversion. .

  Further, the ECU 20 includes a switching valve control unit 21, a bypass valve control unit 22, and an electromagnetic clutch control unit 23 as some functional elements. In the present embodiment, these functional elements are described as being included in the ECU 20 that is an integral hardware, but any one of these functional elements may be provided in separate hardware.

The switching valve control unit 21 controls opening and closing of the switching valve 39 according to the detected value of the outside air temperature sensor 15 when the engine 30 is started. Specifically, when the detected value T _IN of the outside air temperature sensor 15 is smaller than a predetermined threshold value (for example, 25 ° C.) (T _IN <25 ° C.) when the engine 30 is started, the switching valve 39 is closed. Output a control signal. On the other hand, when the detected value T _IN of the outside air temperature sensor 15 is equal to or higher than a predetermined threshold (for example, 25 ° C.) (T _IN ≧ 25 ° C.) when the engine 30 is started, a control signal for opening the switching valve 39 is output. To do. Further, the switching valve control unit 21 outputs a control signal for opening the switching valve 39 during normal operation after the engine 30 is started.

The bypass valve control unit 22 adjusts and controls the opening degree of the bypass valve 14 according to the detection value T _IN of the outside air temperature sensor 15 when the engine 30 is started. The ECU 20 includes a first map (not shown) showing the relationship between the outside air temperature created in advance by experiments and the like and the recirculation rate of the compressed intake air recirculated to the supercharger 11, and the recirculation rate and the valve opening of the bypass valve 14. A second map (not shown) showing the relationship with the is stored. In this first map, for example, when the outside air temperature is minus 25 ° C., the recirculation rate of the compressed intake air is set to 10%, and when the outside air temperature is 25 ° C., the recirculation rate of the compressed intake air is set to 0%. Yes. The bypass valve control section 22, at the start of the engine 30, when the detection value T _IN of the outside air temperature sensor 15 is smaller than a predetermined threshold (e.g., _{25 ℃) (T IN <25} ℃) is the detected value T _IN Is read from the first map, and the valve opening corresponding to the reflux rate is read from the second map and output to the bypass valve 14. Further, when the detected value T _IN of the outside air temperature sensor 15 is equal to or higher than a predetermined threshold (for example, 25 ° C.) (T _IN ≧ 25 ° C.), the bypass valve control unit 22 sets the valve opening to 0 when the engine 30 is started. % (Closed state) is output to the bypass valve 14. The bypass valve control unit 22 outputs a control signal for setting the opening degree of the bypass valve 14 to 0% (closed state) during normal operation after the engine 30 is started.

The electromagnetic clutch control unit 23 controls the operation of the supercharger 11 when the engine 30 is started. That is, when the detected value T _IN of the outside air temperature sensor 15 is smaller than a predetermined threshold value (for example, 25 ° C.) (T _IN <25 ° C.) when the engine 30 is started, the electromagnetic clutch control unit 23 turns off the electromagnetic clutch 12. A control signal to turn ON is output. When the engine 30 is started, if the detected value T _IN of the outside air temperature sensor 15 is equal to or higher than a predetermined threshold (for example, 25 ° C.) (T _IN ≧ 25 ° C.), a control signal for turning off the electromagnetic clutch 12 is output. . During normal operation after the engine 30 is started, a control signal for turning off the electromagnetic clutch 12 is output.

  Since the start assist device 1 according to an embodiment of the present invention is configured as described above, for example, when the engine 30 is started under a low temperature condition, the following control is performed according to the flow shown in FIG. .

  In step (hereinafter, simply referred to as “S”) 100, when the ignition switch is operated and the key switch is turned on, electric power is supplied from a battery (not shown) to the electric system of the vehicle, and the electric system is turned on. Be controlled.

In S110, the detected value T _IN of the outside air temperature sensor 15 is read into the ECU 20, and the starting temperature is determined. If the detected value T _IN of the outside air temperature sensor 15 is smaller than a predetermined threshold value (for example, 25 ° C.), it is determined that the start assist of the engine 30 by the start assist device 1 is necessary, and the process proceeds to S120. On the other hand, when the detected value T _IN of the outside air temperature sensor 15 is equal to or greater than a predetermined threshold (25 ° C.), it is determined that the starting assistance of the engine 30 by the starting assistance device 1 is unnecessary, and this control is returned. That is, the switching valve 39 is controlled to be in an open state, the bypass valve 14 is controlled to be in a closed state, and the electromagnetic clutch 12 is controlled to be turned off to complete this control.

  In S120, a control signal is output from the switching valve control unit 21 of the ECU 20 to the switching valve 39, and the switching valve 39 is controlled to be closed. That is, the flow path of the low-temperature intake air (the low-temperature intake air substantially equal to the outside air) flowing through the first intake passage 34 is switched to the bypass passage 10 that bypasses the intercooler 38.

  In S130, the bypass valve control unit 22 of the ECU 20 bypasses the control signal for the valve opening degree that sets the recirculation rate of the compressed intake air sent from the supercharger 11 to a predetermined value (10% when the outside air temperature is minus 25 ° C.). It is output to the valve 14.

  In S140, a control signal for turning on the connection is output from the electromagnetic clutch control unit 23 of the ECU 20 to the electromagnetic clutch 12. That is, the supercharger 11 is connected to the crankshaft of the engine 30 via the electromagnetic clutch 12. In addition, you may make it perform these operation | movement of S120-140 simultaneously.

  In S150, it is determined whether an engine start condition is satisfied. In S120 to 140 described above, the switching valve 39 is controlled to be closed, the recirculation rate of the compressed intake air to the supercharger 11 is set to a predetermined value (10%), and the connection of the electromagnetic clutch 12 is controlled to be ON. If YES, the process proceeds to S160 assuming that all the start conditions are satisfied. On the other hand, if any of the conditions is not satisfied, it is determined that the engine start condition is not satisfied, and the present control is returned to S120 described above.

  In S160, cranking of the engine 30 by a starter motor (not shown) is executed in response to the establishment of the engine start condition. That is, cranking by the starter motor is continued and the supercharger 11 is driven to rotate. Then, a predetermined amount (10% when the outside air temperature is minus 25 ° C.) of the compressed intake air sent out by the supercharger 11 is returned to the inlet of the supercharger 11 by the compressed intake air recirculation passage 13 and further compressed and heated. It is supplied to the engine 30.

  In S160, the in-cylinder temperature of the engine 30 is raised to the engine start temperature (for example, 400 ° C.) by the compressed intake air sent from the supercharger 11, and the engine 30 is started and the control is returned.

  During normal running of the engine 30, the switching valve 39 is controlled to be in the open state, the opening degree of the bypass valve 14 is set to 0%, and the connection of the electromagnetic clutch 12 is controlled to be OFF. That is, the intake air compressed by the compressor 33 a of the turbocharger 33 flows through the first intake passage 34, is cooled by the intercooler 38, and then is supplied to the engine 30.

  With the configuration as described above, the internal combustion engine start assist device 1 according to one embodiment of the present invention has the following operational effects.

  For example, when the engine 30 is started under a low temperature condition of minus 25 ° C., the switching valve 39 is controlled to be closed, the recirculation rate of the compressed intake air to the supercharger 11 is set to 10%, and the electromagnetic clutch 12 is connected. Is controlled to ON. That is, the intake air flowing through the first intake passage 34 bypasses the intercooler 38 and flows to the bypass passage 10, and is compressed and heated by the supercharger 11. Then, 10% of the compressed intake air delivered from the supercharger 11 is returned to the inlet of the supercharger 11 again by the compressed intake air recirculation passage 13, and is further heated to the compression temperature, and then supplied to the engine 30. The Thereafter, the in-cylinder temperature of the engine 30 is quickly raised to the engine start temperature (for example, 400 ° C.) by the intake air whose temperature has been increased by compression.

  Therefore, the in-cylinder temperature of the engine 30 is quickly raised to the engine start temperature even under a low temperature condition of minus 25 ° C., so that the startability of the engine 30 can be effectively ensured.

  In addition, since the startability of the engine 30 can be ensured even at a low compression ratio under low temperature conditions, the in-cylinder maximum pressure of the engine 30 can be maintained at a low state, and the influence on the durability of the engine 30 is also effective. Can be reduced.

  Here, FIG. 3 shows the relationship between the number of rotations of the supercharger 11 by the start assist device 1 according to this embodiment and the intake air temperature rise. FIG. 4 shows the relationship between the inlet temperature of the intake manifold 31 and the in-cylinder maximum temperature of the engine 30 by the start assisting device 1 according to this embodiment (compression ratio: 11.5, cranking rotation speed: 100 rpm).

  In FIG. 3, a broken line α indicates an increase in intake air temperature when the intake air is simply compressed by the supercharger 11, and an alternate long and short dash line β returns 10% of the intake air compressed by the supercharger 11 to the supercharger 11 again. The intake air temperature rise when it is made to show is shown. As shown in FIG. 3, the intake air temperature is saturated at about 35 ° C. at the broken line α, but the intake air temperature is the number of rotations of the supercharger 11 at the alternate long and short dash line β (when 10% is returned to the supercharger 11). It turns out that it rises rapidly to about 55 degreeC with a raise.

  Further, as shown in FIG. 4, when the inlet temperature of the intake manifold 31 is minus 25 ° C., the in-cylinder maximum temperature is about 325 ° C. That is, in order to increase the in-cylinder temperature to the engine start temperature of 400 ° C. in order to ensure the startability of the engine 30 under a low temperature condition of minus 25 ° C., the inlet temperature of the intake manifold 31 can be increased by about 50 ° C. I understand that

  Here, in the start assist device 1 according to the present embodiment, even when the inlet temperature of the intake manifold 31 is minus 25 ° C., 10% of compressed intake air is recirculated to the supercharger 11 to reduce the intake air temperature. The effect of the present invention can also be seen from the fact that the temperature quickly rises to about 55 ° C. (see FIG. 3) and the in-cylinder temperature can be quickly raised to the engine starting temperature of 400 ° C. (see FIG. 4).

  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.

  In the above-described embodiment, the intake air flowing through the bypass passage 10 has been described as being compressed and heated by the supercharger 11. However, instead of the supercharger 11, for example, a centrifugal charger such as a turbocharger driven by the exhaust energy of the engine 30 is used. A compressor may be applied. In this case, an open / close valve that closes the bypass passage 10 during normal operation of the engine 30 may be provided in either the upstream or downstream bypass passage 10 of the centrifugal compressor.

In the above-described embodiment, the recirculation rate of the compressed intake air to the supercharger 11 has been described as being adjusted based on the value read from the map according to the detection value T _IN of the outside air temperature sensor 15. For example, the reflux rate may always be set to 10% when the engine 30 is started. Further, the reflux rate can be set to a value larger than 10%.

  In the above-described embodiment, the start assist device 1 has been described as being applied to a one-stage turbocharging system including one turbocharger 33. For example, a two-stage turbocharging system including a low-pressure turbo and a high-pressure turbo is used. It can also be applied to. In this case, the same effects as those of the above-described embodiment can be obtained.

1 Start assist device 10 Bypass passage (intake passage)
11 Supercharger (supercharger)
13 Compressed intake air recirculation passage 14 Bypass valve (reflux rate adjusting means)
15 Outside air temperature sensor (outside air temperature detecting means)
20 ECU
30 engine (internal combustion engine)

Claims (4)

A supercharger that is provided in an intake passage of the internal combustion engine and compresses and heats the intake air when starting the internal combustion engine;
An outside air temperature detecting means for detecting the outside air temperature;
A compressed intake air recirculation passage that recirculates a portion of the compressed intake air delivered from the supercharger to the intake passage upstream of the supercharger when starting the internal combustion engine;
A recirculation rate adjusting means that is provided in the compressed intake recirculation passage and adjusts a recirculation rate of the compressed intake air recirculated by the compressed intake recirculation passage according to a detected value of the outside air temperature detecting means when the internal combustion engine is started; A start assist device for an internal combustion engine. A turbocharger that is driven by exhaust from the internal combustion engine, and an intercooler that cools the intake air compressed by the turbocharger;
The start assisting device for an internal combustion engine according to claim 1, wherein the intake passage is a bypass passage that bypasses the intercooler. The internal combustion engine start assist device according to claim 1 or 2, wherein the supercharger is a supercharger driven by the internal combustion engine via an electromagnetic clutch. The internal combustion engine according to any one of claims 1 to 3, wherein the recirculation rate adjusting means sets the recirculation rate to 10% when the detected value of the outside air temperature detecting means is minus 25 ° C. Starting aids.

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