JP2006207438A - Supercharging device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress rise in intake temperature and prevent knocking when an operating condition of an engine is in a pre-rotation region, in a supercharging device for the engine. <P>SOLUTION: This supercharging device for the engine is provided with an electric supercharger provided on an intake passage; a bypass passage communicating upstream and downstream sides of the electric supercharger on the intake passage with each other; a bypass valve opening/closing the bypass passage; and an intake system controller controlling rotational frequency of the electric supercharger and the bypass valve such that predetermined supercharging pressure can be obtained when the operating condition of the engine is in a supercharging region. The supercharging device for the engine is further provided with an engine control device controlling the rotational frequency of the electric supercharger and the bypass valve, such that lower supercharging pressure is obtained compared to the case where the operating condition of the engine is in the supercharging region, when it is determined that the operating condition is in the pre-rotation region set in a low load side of the supercharging region. When the intake temperature exceeds a predetermined value, the control device reduces and corrects the rotational frequency of the electric supercharger. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention belongs to the technical field of an engine supercharging device that increases engine torque by supercharging.

  Conventionally, superchargers and turbochargers that supercharge intake air as means for increasing engine torque are well known. However, as a result of the supercharging ability being greatly affected by the engine speed, the supercharging pressure is low. There is a drawback of lacking. On the other hand, the electrically driven electric supercharger can control the rotational speed without being affected by the engine rotational speed, and therefore has an advantage that a sufficient supercharging pressure can be generated even in a low rotational speed region.

  For example, an engine supercharger described in Patent Document 1 is provided on an electric supercharger disposed on an intake passage, a bypass passage communicating with the upstream side of the supercharger, and a bypass passage. When the engine operating state is in the supercharging region, supercharging is performed by operating the supercharger and closing the bypass valve. In the engine supercharging device having such a configuration, pre-rotation control has been proposed as a method for further improving the responsiveness at the time of rapid acceleration or the like.

As this pre-rotation control, for example, the electric supercharger is operated with the bypass valve opened in advance before the engine operating state shifts to the supercharging region, and the number of rotations of the electric supercharger is increased in advance. Therefore, there is a rotation control that allows a required supercharging pressure to be quickly obtained when the supercharging region is entered. In addition, by operating the electric supercharger in a state where the bypass valve is closed and made clear before the operating state of the engine shifts to the supercharging region, the pressure on the downstream side of the electric supercharger is increased in advance. There is a preload control that allows a required supercharging pressure to be obtained quickly when shifting to a region.
JP 2003-227342 A

  However, the intake air temperature rises during the pre-rotation control, and there is a problem that high-temperature intake air is introduced into the combustion chamber and knocking is likely to occur. The cause of the rise in the intake air temperature during the pre-rotation control is considered as follows.

  That is, at the time of rotation control, the electric supercharger is operated with the bypass valve opened, so that intake air circulates through the bypass passage, but the circulated intake air receives heat generated by the operation of the electric supercharger. The main reason for the rise in intake air temperature is that the temperature rises.

  Further, during the preload control, the pressure difference before and after the bypass valve set to be closed is a main cause of the rise in the intake air temperature. That is, by this pressure difference, the potential energy of the high intake air downstream of the electric supercharger is converted into kinetic energy as a flow velocity when flowing upstream of the turbocharger through the clearance of the bypass valve, and this kinetic energy is When the flow velocity is lost due to, for example, a collision with fresh air upstream of the supercharger, it is converted into thermal energy, which increases the intake air temperature.

  Accordingly, an object of the present invention is to suppress an increase in intake air temperature and prevent occurrence of knocking when an engine operating state is in a pre-rotation region in an engine supercharging device.

  In order to solve the above problems, the present invention is configured as follows.

  First, the invention according to claim 1 of the present application is directed to an electric supercharger provided in an intake passage, a bypass passage communicating with the downstream side of the electric supercharger in the intake passage, and opening and closing the bypass passage. And a supercharging control means for controlling the rotational speed of the electric supercharger and the bypass valve so that a predetermined supercharging pressure is obtained when the operating state of the engine is in the supercharging region. And determining means for determining whether or not the engine operating state is in a pre-rotation region set on the low load side of the supercharging region, and the engine operating state is preliminarily determined by the determining unit. Pre-rotation control means for controlling the rotational speed of the electric supercharger and the bypass valve so that the supercharging pressure is lower than when the operation state is in the supercharging region when it is determined that the engine is in the rotational region; And intake air temperature detecting means for detecting Is, the pre-rotation control means, the intake air temperature detected by the intake air temperature detecting means when the predetermined value or more, characterized in that it reduces compensation for the rotational speed of the electric supercharger.

  Of the pre-rotation control, in the pre-pressure control, the rotation speed and bypass valve of the electric supercharger are controlled so that a supercharging pressure lower than the supercharging pressure in the supercharging region is obtained. Then, although the preload is not performed, the rotational speed of the electric supercharger is controlled so that the supercharging pressure immediately downstream of the electric supercharger is lower than the supercharging pressure in the supercharging region.

  According to a second aspect of the present invention, in the supercharging device for an engine according to the first aspect, the prerotation control performed by the prerotation control means controls the throttle of the bypass valve and the electric supercharger. In addition to preload control for operating to obtain a supercharging pressure, and during the preload control, when the intake air temperature detected by the intake air temperature detecting means is equal to or higher than a predetermined value, in addition to correcting the decrease in the rotational speed of the electric supercharger The bypass valve is controlled to be closed.

  According to a third aspect of the present invention, in the engine supercharging device according to the first aspect, the pre-rotation control means sets a reduction correction amount for the rotational speed of the electric supercharger in accordance with a knocking occurrence factor. It is characterized by correction.

  First, according to the first aspect of the invention, when the engine operating state is in the pre-rotation region, the rotational speed of the electric supercharger is corrected to decrease, so that the driving power of the supercharger is reduced. Heat generation of the supercharger is suppressed. As a result, particularly in rotation control, the amount of heat received by the circulated intake air is reduced, and an increase in intake air temperature is suppressed. Further, in the preload control, the pressure downstream of the supercharger is reduced by lowering the rotational speed of the electric supercharger. As a result, the pressure difference before and after the bypass valve can be reduced, and the intake temperature rises. It is suppressed. Thus, according to the present invention, an increase in the intake air temperature during the pre-rotation control is suppressed, and the occurrence of knocking is prevented.

  According to the second aspect of the invention, since the opening degree of the bypass valve is further controlled in the closing direction in addition to lowering the rotational speed of the electric supercharger during the preload control, it is circulated from the gap of the bypass valve. The degree of intake air that receives heat generated by the electric supercharger is reduced, and an increase in intake air temperature is effectively suppressed.

  According to the third aspect of the present invention, when it is determined that knocking is likely to occur according to knocking factors such as intake air temperature and fuel properties, the reduction correction amount for the rotational speed of the electric supercharger is determined. When it is determined that knocking is unlikely to occur, it is possible to prevent the occurrence of knocking by increasing the value of the electric supercharger. It is possible to prevent the responsiveness of the supercharging pressure from being lowered by reducing the rotational speed of the engine.

  Hereinafter, embodiments of the present invention will be described.

  First, a first embodiment of the present invention will be described. FIG. 1 shows an engine intake system 1 according to the present embodiment. In this intake system 1, an air cleaner 3, an electric supercharger 4, a throttle valve 5, and a surge tank 6 are provided in the intake passage 2 from the upstream side, and each of the cylinders # 1 to # 4 is provided from the surge tank 6. A plurality of independent intake passages 7...

  In addition, a bypass passage 8 that directly communicates the upstream side and the downstream side of the electric supercharger 4 in the intake passage 2 is provided, and a bypass valve that controls the flow rate of air passing through the passage 8 is provided in the bypass passage 8. 9 is provided.

  The electric supercharger 4 includes a compressor 4a and a motor 4b. When the motor 4b is driven, the compressor 4a sucks air and pumps the air to each of the cylinders # 1 to # 4. Increase.

  Further, an engine control device 100 for controlling the engine is provided, and a signal from the accelerator opening sensor 10 for detecting the amount of depression of the accelerator pedal 10a (engine load) by the driver and the engine speed are controlled by the control device 100. A signal from the engine speed sensor 11 to be detected, a signal from the intake air temperature sensor 12 to detect the intake air temperature, and the like are input.

  The throttle actuator 13 that opens and closes the throttle valve 5 based on the input signals, the spark plugs 14... 14 provided in the cylinders # 1 to # 4, and the intake system controller 101 that controls the intake system 1 Output a control signal. Further, the intake system controller 101 outputs control signals to a bypass actuator 15 that opens and closes the bypass valve 9, an electric supercharger controller 102 that controls the rotational speed of the electric supercharger 4, and the like.

  Further, the engine is provided with an alternator 20 that generates electric power by driving the engine, and a battery 21 that stores electric power generated by the alternator 20, and electric power is supplied from the battery 21 to the electric supercharger controller 102. It comes to be supplied.

  The intake passage 2, the electric supercharger 4, the bypass passage 8, and the bypass valve 9 correspond to the constituent elements that are the premise of the supercharging device according to claim 1. The intake air temperature sensor 12 corresponds to the intake air temperature detection means of the supercharging device according to claim 1, and the engine control device 100 corresponds to the determination device and the pre-rotation control means of the supercharging device according to claim 1. The intake system controller 101 corresponds to the supercharging control means of the supercharging device according to claim 1.

  On the other hand, the engine control device 100 stores a map in which the engine operating region shown in FIG. 2 is set. In this map, four areas with the engine speed and the engine load as parameters are set. In other words, the natural intake region is on the high rotation side (engine speed is N1 or higher) of the entire engine operation region, and the prerotation region (preload) is on the low load low rotation side (engine speed is N1 or lower and engine load is α1 or lower). Area), a supercharging area is set on the high load low rotation side (engine speed is N1 or less, engine load is α1 or more), and a surging area is set on the low rotation side in the supercharging area. ing.

  In the natural intake region, the electric supercharger 4 is not operated with the bypass valve 9 open. The air introduced into the intake passage 2 flows in the forward direction in the bypass passage 8 as indicated by an arrow A in FIG. 1 and is supplied to the cylinders # 1 to # 4.

  In the pre-rotation region, in the present embodiment, pre-pressure control is performed as pre-rotation control. In the preload control, the electric supercharger 4 is operated in a state in which the bypass valve 9 is closed. As a result, the pressure on the downstream side of the electric supercharger 4 in the intake passage 2 can be increased in advance, and the responsiveness of the supercharging pressure when the engine operating state shifts to the supercharging region is improved. At this time, the throttle control of the throttle valve 5 is performed at the same time so that the intake air amount introduced into the cylinders # 1 to # 4 is not increased more than necessary, and the intake air amount is accurately realized.

  In the supercharging region, the electric supercharger 4 is operated with the bypass valve 9 closed. The air introduced into the intake passage 2 flows through the intake passage 2 as shown by an arrow B in FIG.

  In the surging region, the electric supercharger 4 is operated with the bypass valve 9 half open. This surging region is a region in which intake air may flow backward through the electric supercharger 4 when the pressure on the downstream side of the electric supercharger 4 is high and the flow rate of intake air is small. By partially opening 9, a part of the intake air is circulated in the bypass passage 8 as shown by an arrow C in FIG.

  On the other hand, the map of FIG. 3 shows the characteristics of the electric supercharger 4. In this map, the pressure ratio on the upstream and downstream sides of the electric supercharger 4 is plotted on the vertical axis with the intake air amount on the horizontal axis. Is shown in And the area | region X shown to a figure is set as a use area | region of this electric supercharger 4. FIG. Note that the region Y on the low intake air amount / high pressure ratio side of the region X is a region where the above-mentioned surging is likely to occur because the pressure on the downstream side of the electric supercharger 4 is high and the air flow rate is small.

  Further, in the area X, areas a to p corresponding to the power consumption of the electric supercharger 4 are set. These areas a to p are substantially strip-shaped areas divided by a plurality of curves in which the pressure ratio decreases as the intake air amount increases, and the region a on the low intake air amount / low pressure ratio side The power consumption increases in order.

  Further, in region X, the characteristics of the rotational speed of the electric supercharger 4 are shown. As for this characteristic, a curve with a rotational speed of 40000 rpm is set on the low intake air amount low pressure ratio side in the region X, and it is shown that the rotational speed increases as it moves to the high intake air intake high pressure ratio side.

  By the way, the rated output of the electric supercharger 4 used in this embodiment is 2 kW, and as shown in FIG. 4, when the power consumption of the electric supercharger 4 exceeds 1 kW, which is half of the rated power, It has been found that knocking is likely to occur due to a corresponding increase in discharge pressure. Since retard control of the ignition timing is performed in order to suppress this knocking, the actually obtained engine torque increases moderately. Further, since the torque consumed by the alternator 20 increases in accordance with the power consumption of the electric supercharger 4, the actually obtained torque is further suppressed. As a result, the power consumption of the supercharger 4 is excessive in the region where the power consumption is 1 kW or more. Even if the power consumption of the feeder 4 is further increased, the net actual torque hardly increases. Here, the electric power consumption of the electric supercharger 4 when knocking is likely to occur is 1 kW, but this value is changed according to the rating and characteristics of the electric supercharger 4.

  The intake system 1 is controlled by the engine control device 100, the intake system controller 101, and the electric supercharger controller 102 according to the flowchart shown in FIG.

  First, in step S1, the engine control apparatus 100 reads various signals from each sensor, and in step S2, the intake air amount is obtained based on these signals. Specifically, the intake air amount is calculated based on the engine load detected by the accelerator opening sensor 10 and the engine speed detected by the engine speed sensor 11. At this time, the intake air amount may be detected by a sensor or the like.

  Then, in step S3, it is determined whether or not the engine speed is greater than N1, and if it is greater than N1, the operating state belongs to the natural intake region shown in the map of FIG. 2, and therefore the bypass valve 9 is fully opened in step S4. In step S5, the electric supercharger 4 is stopped. As a result, the natural intake in which the air introduced from the air cleaner 3 is supplied to the cylinders # 1 to # 4 via the bypass passage 8 is executed.

  On the other hand, when the engine speed is N1 or less in step S3, the process proceeds to step S5 to determine whether the engine load is α1 or more. When the engine load is larger than α1, the engine operating state belongs to the supercharging region. At this time, it is determined whether or not the operating state belongs to the surging region.

  When the engine operating state does not belong to the surging region in step S7, the process proceeds to step S8 to close the bypass valve 9, and 1 kW operation control is performed in step S9. In the 1 kW operation control, the amount of intake air obtained in step S2 is obtained on the area h corresponding to 1 kW among the areas a to p corresponding to the power consumption of the electric supercharger 4 shown in FIG. The rotational speed of the charger 4 is read out, and the rotational speed of the supercharger 4 is controlled to this rotational speed.

For example, in the 1 kW operation control when the intake air amount obtained in step S2 is 2 m ³ / min, the rotational speed of the electric supercharger 4 at the point Z on the region h is read in the map of FIG. The point Z is at a position where the rotational speed is slightly closer to 60000 rpm from 60000 rpm, and 62000 rpm is obtained by interpolation. Then, the engine control device 100 sends a signal to the electric supercharger controller 102 via the intake system controller 101 to control the supercharger 4 to have this rotational speed, whereby the power consumption is 1 kW and the rotational speed is Operation of 62000 rpm is realized.

  On the other hand, when the engine operating state belongs to the surging region in step S7, the process proceeds to step S10, the bypass valve 9 is half-opened, and the above-described 1 kW operation control is performed in step S11. As a result, a part of the air discharged from the electric supercharger 4 flows back through the bypass passage 8, and as a result, the pressure downstream of the supercharger 4 is lowered and the occurrence of surging is avoided in advance. .

Further, since a part of the air is circulated in this way, the amount of air actually sucked becomes smaller than that required. On the other hand, if the amount of air circulating through the bypass passage 8 is β, it is assumed that the intake air amount increased by the amount corresponding to β is required in order to supplement the air amount β during the 1 kW operation control. Will apply the map. For example, when the intake air amount calculated in step S1 is 2 m ³ / min, 2 + βm ³ / min obtained by adding the amount of air to be circulated 2 + βm ³ / min is set as the value of the intake air amount and the region h corresponding to this intake air amount The rotational speed (about 58000 rpm) at the point Z ′ is read out.

  By the way, when the engine load is α1 or less in step S6, since the operating state belongs to the pre-rotation region (preload region), control is performed so that the bypass valve 9 is substantially closed in step S12, and the electric supercharger in step S13. The rotational speed of 4 is controlled to a preset rotational speed for preload control, and the process proceeds to step S14. Note that the rotational speed of the electric supercharger 4 for preload control is set to be lower than the rotational speed in the supercharging region, for example, and the obtained supercharging pressure is also low.

  In step S14, it is determined whether or not the intake air temperature detected by the intake air temperature sensor 12 is higher than T1. When the intake air temperature is equal to or lower than T1, the preload control is continued. When the intake air temperature is higher than T1, the routine proceeds to step S15, where the rotation of the electric supercharger 4 is rotated according to knocking factors (intake air temperature, fuel properties, etc.). Reduce the number. At this time, as shown in the map of FIG. 6, the rotational speed reduction correction amount of the electric supercharger 4 is zero when the intake air temperature is equal to or lower than T1, and increases as the intake air temperature increases above T1. In addition, as shown in the map of FIG. 7, when the octane number of the fuel used is high, knocking is unlikely to occur, so control is performed so as to decrease.

  Next, in step S16, the bypass valve 9 is controlled to be closed according to the knocking occurrence factor. At this time, as shown in the map of FIG. 8, the closed control amount of the bypass valve 9 is zero when the intake air temperature is equal to or lower than T1, and is controlled so as to increase as the intake air temperature increases above T1. At the same time, as shown in the map of FIG. 9, when the octane number of the fuel used is high, the fuel is controlled to be small.

  Step S15 corresponds to the gist of the invention described in claims 1 and 3, and step S16 corresponds to the gist of the invention described in claim 2.

  Next, as a second embodiment of the present invention, a case where each operation region is set as shown in the map of FIG. 10 will be described. This map is obtained by changing the preload area of the prerotation area set in the low load low rotation area of the map of FIG. 2 to the rotation area.

  The rotation control performed in this pre-rotation region is performed when the electric supercharger 4 is operated with the bypass valve 9 opened, and air is circulated through the bypass passage 8 so that the operation state is shifted to the supercharging region. Improves responsiveness of supply pressure. In this rotation region, since the bypass valve 9 is opened, no preload is performed. However, the supercharging pressure immediately downstream of the electric supercharger 4 is the supercharging pressure in the supercharging region. It is set to be smaller.

  In this embodiment, the intake system 1 is controlled according to the flowchart shown in FIG. In this flowchart, steps S21 to S31 are the same controls as steps S1 to S11 in the flowchart of FIG. 5 in the first embodiment, so that description thereof is omitted, and here, steps related to rotation control are omitted. Only S32 to 35 will be described.

  That is, in step S32, the bypass valve is controlled to be fully opened, and in step S33, the rotational speed of the electric supercharger 4 is controlled to the rotational speed for rotational control. When it is determined in step S34 that the intake air temperature is higher than T1, the process proceeds to step S35, and the rotational speed of the electric supercharger 4 is decreased according to the knocking factor (intake air temperature, fuel properties, etc.). At this time, similarly to step S15 in the flowchart of FIG. 5, the reduction correction of the rotational speed of the electric supercharger 4 according to the intake air temperature and the octane number is performed. If the intake air temperature is equal to or lower than T1 in step S34, the rotation control is continued.

  As described above, when the engine operating state is in the pre-rotation region, the rotational speed of the electric supercharger 4 is corrected to decrease, so that the driving power of the supercharger 4 is reduced and the supercharger 4 Heat generation is suppressed. As a result, particularly in rotation control, the amount of heat received by the circulated intake air is reduced, and an increase in intake air temperature is suppressed. Further, in the preload control, the pressure downstream of the supercharger 4 is reduced by reducing the rotational speed of the electric supercharger 4, and as a result, the pressure difference before and after the bypass valve 9 can be reduced. An increase in intake air temperature is suppressed. Thus, according to the present invention, an increase in the intake air temperature during the pre-rotation control is suppressed, and the occurrence of knocking is prevented.

  Further, since the opening degree of the bypass valve 9 is further controlled in the closing direction in addition to lowering the rotational speed of the electric supercharger 4 during the preload control, the intake air circulating through the gap of the bypass valve 9 is driven by the electric supercharger 4. The degree of receiving the heat is reduced, and the rise of the intake air temperature is effectively suppressed.

  When it is determined that knocking is likely to occur according to knocking factors such as intake air temperature and fuel properties, knocking is reliably generated by increasing the reduction correction amount of the rotational speed of the electric supercharger 4. On the other hand, when it is determined that knocking is unlikely to occur, the rotational speed of the electric supercharger 4 is reduced by reducing the rotational speed reduction correction amount of the electric supercharger 4 and excessively reduced. It is prevented that the responsiveness of the supply pressure is lowered.

  An object of the present invention is to suppress an increase in intake air temperature and prevent knocking when an engine operating state is in a pre-rotation region in an engine supercharging device. INDUSTRIAL APPLICABILITY The present invention is widely suitable for the technical field of an engine supercharging device that increases engine torque by supercharging.

1 is an engine intake system according to an embodiment of the present invention. It is a map which shows the driving | operation area | region of an engine. It is a map which shows the characteristic of an electric supercharger. It is a graph of the engine torque characteristic according to the power consumption of an electric supercharger. It is a flowchart which concerns on control of an intake system. It is a map of the rotation speed increase amount of the electric supercharger according to the intake air temperature. It is a map of the rotation speed increase amount of the electric supercharger according to an octane number. It is a map of the bypass valve closing control amount according to intake air temperature. It is a map of the bypass valve closing control amount according to the octane number. It is a map which shows the driving | operation area | region of the engine which concerns on the 2nd Embodiment of this invention. It is a flowchart concerning control of the same intake system.

Explanation of symbols

2 Intake passage 4 Electric supercharger 8 Bypass passage 9 Bypass valve 12 Intake temperature sensor 100 Engine control device 101 Intake system controller

Claims (3)

An electric supercharger provided in the intake passage, a bypass passage communicating the upstream side and the downstream side of the electric supercharger in the intake passage, a bypass valve that opens and closes the bypass passage, and an engine operating state is a supercharging region And a supercharging control means for controlling the rotational speed of the electric supercharger and the bypass valve so that a predetermined supercharging pressure is obtained when
Determination means for determining whether or not the operating state of the engine is in a pre-rotation region set on the low load side of the supercharging region;
When it is determined by the determination means that the engine operating state is in the pre-rotation region, the rotational speed of the electric supercharger and the bypass valve are set so that the supercharging pressure is lower than when the operating state is in the supercharging region. Pre-rotation control means for controlling;
An intake air temperature detecting means for detecting the intake air temperature,
The engine supercharging device, wherein the pre-rotation control means corrects the rotational speed of the electric supercharger to decrease when the intake air temperature detected by the intake air temperature detection means is equal to or higher than a predetermined value. The engine supercharging device according to claim 1,
The pre-rotation control performed by the pre-rotation control means is a pre-pressure control for obtaining a supercharging pressure by controlling the throttle of the bypass valve and operating the electric supercharger,
During the preload control, when the intake air temperature detected by the intake air temperature detecting means is equal to or higher than a predetermined value, the bypass valve is controlled to be closed in addition to the reduction correction of the rotational speed of the electric supercharger. The engine supercharger. The engine supercharging device according to claim 1,
The supercharger for an engine according to claim 1, wherein the pre-rotation control means corrects the reduction correction amount of the rotational speed of the electric supercharger according to a knocking occurrence factor.

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