JP4492377B2 - Engine supercharger - Google Patents

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 obtained quickly 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 quickly obtained 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. As a cause for increasing the intake air temperature during the pre-rotation control, for example, there are the following.

  That is, at the time of rotation control, since the electric supercharger is operated with the bypass valve opened, the intake air is circulated through the bypass passage, and this circulation is caused by the operation of the electric supercharger. The temperature gradually rises as it repeatedly receives heat.

  Further, at the time of preload control, the pressure difference before and after the bypass valve which is set to be closed causes the intake air temperature to rise. 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 includes an electric supercharger provided in an intake passage, a first bypass passage that communicates the electric supercharger in the intake passage with the downstream side, and the bypass passage. And a supercharging control means for controlling the rotational speed of the electric supercharger and the bypass valve so as to obtain a predetermined supercharging pressure when the engine operating state is in the supercharging region. A determination device 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 by the determination 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 Provided downstream of the electric supercharger in the intake passage A turbine generator that generates power by the air flow generated by the supercharger, the pre-rotation-controlled in accordance with the pre-rotation control means, and having a power generation control means for generating said turbine generator.

  Of the pre-rotation control, in the pre-pressure control, a relatively high supercharging pressure is generated by the electric supercharger, but it is controlled in a range not exceeding the supercharging pressure in the supercharging region, and in the rotation control, Since the bypass valve is open, the supercharging pressure is not so high. Therefore, in any control, the supercharging pressure during the pre-rotation control is lower than the supercharging pressure in the supercharging region.

  Further, the invention according to claim 2 is the engine bypassing device according to claim 1, wherein the turbine generator is connected to the downstream side of the turbocharger downstream of the electric supercharger in the intake passage. A passage, an on-off valve that opens and closes the second bypass passage, and an intake air temperature detection means that detects an intake air temperature. The power generation control means detects the intake air temperature during pre-rotation control by the pre-rotation control means. When the intake air temperature detected by the means is below a predetermined value, the on-off valve is opened and power generation by the turbine generator is restricted.

  According to a third aspect of the present invention, in the engine supercharging device according to the first aspect, the pre-rotation control means closes the bypass valve during pre-rotation control, and the power generation control means During the rotation control, the power generation amount of the turbine generator is controlled so as to become the highest in a range where surging of the electric supercharger does not occur.

  According to the first aspect of the present invention, a turbine generator is disposed downstream of the electric supercharger in the intake passage, and the turbine of the generator is supplied by air pumped by the electric supercharger during pre-rotation control. Is driven to generate electricity. And in this electric power generation, the thermal energy which the air pumped by the electric supercharger has is converted into the kinetic energy which drives a turbine. As a result of the consumption of heat energy for power generation, the intake air temperature as a whole intake system is lowered or increased, and knocking is prevented. Furthermore, since the electric power consumption by the electric supercharger is supplemented by the power generation by the turbine generator, the fuel efficiency can be improved.

  By the way, the bypass valve etc. which open and close the 1st bypass passage may freeze up at the time of low temperature. At this time, the ice layer covering the bypass valve or the like peels off and is sucked into the combustion chamber, which may cause bad effects such as poor combustion.

  On the other hand, according to the invention described in claim 2, the open / close valve that restricts the power generation by the turbine generator at the low temperature during the pre-rotation control and communicates the upper and downstream sides of the generator. Since it is controlled to be opened, the intake air temperature is quickly raised by the heat generation action by the electric supercharger and the heat is suppressed from being taken away by the driving of the turbine, so the ice layer covering the bypass valve etc. It is quickly thawed to eliminate the above-mentioned adverse effects.

  Further, as a characteristic of the electric supercharger, when the pressure ratio before and after the electric supercharger is high and the flow rate of air is small, a phenomenon called surging in which air flows back through the electric supercharger is likely to occur. When the power generation amount by the turbine generator is increased during the preload control, the power generation efficiency is good, but the air flow rate downstream of the electric supercharger decreases, and surging is likely to occur.

  On the other hand, according to the third aspect of the present invention, the power generation amount of the turbine generator is controlled to be the highest in a range where surging does not occur according to the characteristics of the electric supercharger. The generation of surging is prevented by securing a limited air flow rate, and the power generation amount of the generator is set as large as possible to increase the efficiency of power generation.

  Embodiments of the present invention will be described below.

  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 the intake system 1, an air cleaner 3, an electric supercharger 4, a turbine generator 5, a throttle valve 6, and a surge tank 7 are provided in the intake passage 2 from the upstream side, and each cylinder # 1 is provided from the surge tank 7. A plurality of independent intake passages 8... 8 respectively leading to .about. # 4 are branched.

  In addition, a first bypass passage 9 that directly communicates the upstream side and the downstream side of the electric supercharger 4 in the intake passage 2 is provided, and the first bypass passage 9 has a flow rate of air passing through the passage 9. A bypass valve 10 is provided for controlling the above. Further, a second bypass passage 11 that directly communicates the upstream and downstream sides of the turbine generator 5 in the intake passage 2 is provided. The second bypass passage 11 has a flow rate of air passing through the passage 10. A generator bypass valve 12 to be controlled 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.

  The turbine generator 5 includes a turbine 5a and a generator 5b. The turbine 5a is driven by thermal energy of air pumped by the electric supercharger 4, and the generator 5b uses kinetic energy generated by driving the turbine 5a as electric power. Convert. The power generation amount of the generator 5 is variable by controlling the field current, and the rotational resistance of the turbine 5a increases or decreases according to the power generation amount.

  Further, the engine includes an alternator 20 that generates electric power by driving the engine, and a battery 21 that stores electric power generated by the alternator 20. The battery 21 also stores the electric power converted by the generator 5b of the turbine generator 5.

  Further, an engine control device 100 for controlling the engine is provided, and a signal from the accelerator opening sensor 30 for detecting the amount of depression of the accelerator pedal 30a (engine load) by the driver and the engine speed are controlled by the control device 100. A signal from the engine speed sensor 31 to be detected, a signal from the intake air temperature sensor 32 to detect the intake air temperature, and the like are input.

  The throttle actuator 33 that opens and closes the throttle valve 6 based on the input signals, the spark plugs 34... 34 provided in each cylinder # 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 includes a generator 5 b of the generator 5, a generator bypass valve 12, a bypass actuator 35 that opens and closes the bypass valve 10, and an electric supercharger controller 102 that controls the rotational speed of the electric supercharger 4. A control signal is output to The electric supercharger controller 102 is supplied with power from the battery 21.

  The intake passage 2, the electric supercharger 4, the first bypass passage 9, and the bypass valve 10 correspond to the constituent elements that are the premise of the supercharging device according to claim 1. Further, the engine control device 100 corresponds to a determination unit in the supercharging device according to claim 1, and an intake system controller 101 includes a supercharging control unit, a pre-rotation control unit, and the like in the supercharging device according to claim 1. It corresponds to power generation control means. The generator bypass valve 12 corresponds to an on-off valve in the supercharging device according to a second aspect, and the intake air temperature sensor 32 corresponds to an intake air temperature detecting means in the supercharging device according to the second aspect.

  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 operated with the bypass valve 10 opened, and the generator bypass valve 12 is opened. The air introduced into the intake passage 2 flows in the forward direction through the first bypass passage 9 as indicated by the arrow A in FIG. 1 and is supplied to the cylinders # 1 to # 4.

  In the preload control performed in the pre-rotation region, the electric supercharger 4 is operated in a state where the bypass valve 10 is closed, and the opening and closing of the generator bypass valve 12 is controlled according to the intake air temperature. As a result, the pressure on the downstream side of the electric supercharger 4 in the intake passage 2 is increased in advance, and the responsiveness of the supercharging pressure when the engine operating state shifts to the supercharging region can be improved. it can. At this time, the throttle control of the throttle valve 6 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. When the generator bypass valve 12 is closed, the air pumped from the electric supercharger 4 passes through the turbine 5a of the turbine generator 5 as shown by the arrow D in FIG. 2, when the valve 12 is open, the air pumped from the electric supercharger 4 bypasses the turbine 5 a of the generator 5 as indicated by an arrow E, and passes through the second bypass passage. 11 and flows downstream of the intake passage 2.

  In the supercharging region, the electric supercharger 4 is operated with the bypass valve 10 closed, and the generator bypass valve 12 is opened. The air introduced into the intake passage 2 passes through the second bypass passage 11 as shown by an arrow E in FIG. 1 and flows through the intake passage 2 as shown by an arrow B.

  In the surging region, the electric supercharger 4 is operated with the bypass valve 10 half open, and the generator bypass valve 12 is opened. This surging region is a region where the pressure on the downstream side of the electric supercharger 4 is high and the flow rate of the intake air is small. Therefore, surging where the intake air flows back through the electric supercharger 4 may occur. By partially opening the bypass valve 10, as shown by the arrow C in FIG. 1, a part of the intake air is circulated in the first bypass passage 9 in the reverse direction.

  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 the present embodiment is 2 kW, and when the power consumption of the electric supercharger 4 exceeds 1 kW, which is half of the rated power, as shown in FIG. 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 an alternator (not shown) increases in accordance with the power consumption of the electric supercharger 4, the actually obtained torque is further suppressed. As a result, in the region where the power consumption of the supercharger 4 is 1 kW or more Even if the power consumption of the supercharger 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 30 and the engine speed detected by the engine speed sensor 31. 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 10 is fully opened in step S4. In step S5, the electric supercharger 4 is stopped. Next, the generator bypass valve 12 is controlled to open at step S6. 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 first bypass passage 9 is executed.

  On the other hand, when the engine speed is N1 or less in step S3, the process proceeds to step S7 to determine whether the engine load is α1 or more. Here, when the engine load is larger than α1, the operating state of the engine 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 S8, the process proceeds to step S9, the bypass valve 10 is closed, and 1 kW operation control is performed in step S10. 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. In step S11, the generator bypass valve 12 is controlled to open.

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 S8, the process proceeds to step S12, the bypass valve 10 is half opened, the 1 kW operation control is performed in step S13, and the process proceeds to step S11. As a result, a part of the air discharged from the electric supercharger 4 flows back through the first bypass passage 9, and the downstream pressure of the supercharger 4 is lowered to avoid surging.

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 first bypass passage 9 is β, it is assumed that an intake air amount increased by an amount corresponding to β is required in order to supplement the air amount β during 1 kW operation control. The map of FIG. 3 is applied. 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 S7, since the operating state belongs to the pre-rotation region (pre-load region), the bypass valve 10 is controlled to be almost closed in step S14, and the electric supercharger in step S15. The rotational speed of 4 is controlled to a preset rotational speed for preload control. 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.

  Next, in step S16, the field current of the generator 5b is controlled so that the amount of power generated by the turbine generator 5 becomes the surging limit. As described above, the rotational resistance of the turbine 5a increases or decreases according to the amount of power generated by the generator 5. For example, when the power generation amount of the generator 5 is large, the rotational resistance of the turbine 5a increases, and accordingly, the resistance received by the air pumped from the electric supercharger 4 increases and the air flow rate decreases. On the other hand, when the power generation amount of the generator 5 is small, the rotational resistance of the turbine 5a decreases, and accordingly, the resistance received by the air pumped from the electric supercharger 4 decreases, so the air flow rate increases. .

  In the characteristic map of the electric supercharger 4 shown in FIG. 3, the air flow rate corresponds to the intake air amount, and the surging region Y is located on the low intake air amount side of the region X as described above. Here, in the region X, the vicinity of the boundary with the region Y is the surging limit line L, and the power generation amount of the turbine generator 5 is set so that the intake air amount is located on the line L.

By the way, in step S15, the rotation speed of the electric supercharger 4 may be set to the rotation speed of the 1 kW operation control. For example, at the time of 1 kW operation control, as shown in FIG. 3, when the intake air amount is 3 m ³ / min, the rotation speed (53000 rpm) of the supercharger 4 is set corresponding to the point S on the region h. . On the other hand, in step S16, the power generation amount of the turbine generator 5 is set so as to be the point S ′ on the surging limit line L at the same rotational speed (53000 rpm) of the supercharger 4, and the intake air amount γ Is realized. In this way, by executing the 1 kW operation also in the preload control, the rotational speed of the supercharger 4 is increased in advance to be equal to the rotational speed in the supercharging region, and the engine operating region is changed from the prerotating region to the supercharging region. The responsiveness of the supercharging pressure at the time of shifting can be improved.

  Step S16 corresponds to the gist of the invention described in claims 1 and 3.

  On the other hand, in step S17, it is determined whether or not the intake air temperature detected by the intake air temperature sensor 32 is lower than T1. Here, when the intake air temperature is lower than T1, the generator bypass valve 12 is controlled to open. As a result, the air pumped from the electric supercharger 4 flows downstream of the intake passage 2 through the second bypass passage 11.

  Further, when the intake air temperature is equal to or higher than T1, the generator bypass valve 12 is controlled to be closed. As a result, the air pumped from the electric supercharger 4 passes through the turbine 5 a of the generator 5 and flows downstream of the intake passage 2.

  Steps S17 to S19 correspond 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. 6 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 the pre-rotation region is performed when the electric supercharger 4 is operated with the bypass valve 10 opened, and the intake air is circulated through the first bypass passage 9 so that the operation state shifts to the supercharging region. Improves the supercharging pressure response. In this rotation region, since the bypass valve 10 is in an open state, no preload is performed, and the supercharging pressure is smaller than the supercharging pressure in the supercharging region.

  In this embodiment, the intake system 1 is controlled according to the flowchart shown in FIG. In this flowchart, steps S21 to S33 and steps S37 to S39 are the same controls as steps S1 to S13 and steps S17 to 19 in the flowchart of FIG. 5 in the first embodiment. Omitted, here, only steps S34 and S35 related to rotation control will be described.

  That is, after it is determined that the intake air temperature is higher than T1, the bypass valve 10 is controlled to be fully opened in step S34, and the rotational speed of the electric supercharger 4 is controlled to the rotational speed for rotation control in step S35. . At this time, the rotation speed of the supercharger 4 may be set to the rotation speed of 1 kW operation control.

  As described above, the turbine generator 5 is disposed downstream of the electric supercharger 4 in the intake passage 2, and the turbine 5a of the generator 5 is moved by the air pumped by the electric supercharger 4 during the pre-rotation control. Drive to generate electricity. And in this electric power generation, the thermal energy which the air pumped by the electric supercharger 4 has is converted into the kinetic energy which drives the turbine 5a. As a result of the heat energy being consumed by power generation, the intake air temperature as a whole is reduced or the rise is suppressed, and the occurrence of knocking is prevented. Furthermore, since the electric power consumption by the electric supercharger 4 is supplemented by the power generation by the turbine generator 5, it is possible to achieve both improved fuel efficiency.

  By the way, when the temperature is low, the bypass valve 10 that opens and closes the first bypass passage 9 may freeze. At this time, the ice layer covering the bypass valve 10 and the like peels off and is sucked into the combustion chamber, which may cause adverse effects such as poor combustion.

  On the other hand, at the time of pre-rotation control, at a low temperature, the power generation by the turbine generator 5 is stopped and the generator bypass valve 12 that communicates the generator 5 with the downstream side is controlled to be opened. As a result, the intake air temperature is quickly raised by the heat generating action of the electric supercharger 4 and the heat is suppressed from being removed by driving the turbine 5a, so that the ice layer covering the bypass valve 10 and the like is quickly thawed. Thus, the above-described adverse effects are eliminated.

  In addition, as a characteristic of the electric supercharger 4, a phenomenon called surging occurs in which air flows backward through the electric supercharger 4 when the pressure ratio upstream and downstream of the electric supercharger 4 is high and the flow rate of air is small. It becomes easy to do. When the power generation amount by the turbine generator 5 is increased during the preload control, the power generation efficiency is good, but the air flow rate downstream of the electric supercharger 4 decreases, so surging is likely to occur.

  On the other hand, according to the characteristics of the electric supercharger 4, the power generation amount of the turbine generator 5 is controlled so as to be the highest in a range where surging does not occur. Is prevented, and the power generation amount of the generator 5 is set as large as possible to improve the power generation efficiency.

  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 concerning control of an intake system. 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 5 Turbine generator 9 Bypass passage 10 Bypass valve 32 Intake temperature sensor 100 Engine control device 101 Intake system controller

Claims (3)

If the engine is in an overrun state, an electric supercharger provided in the intake passage, a first bypass passage that communicates the upstream and downstream sides of the electric supercharger in the intake passage, a bypass valve that opens and closes the bypass passage, and A supercharging device for an engine provided with a supercharging control means for controlling the rotational speed of the electric supercharger and a bypass valve so as to obtain a predetermined supercharging pressure when in a charging region,
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;
A turbine-type generator that is provided downstream of the electric supercharger in the intake passage and generates power by an air flow generated by the supercharger;
A supercharging device for an engine, comprising: power generation control means for causing the turbine generator to generate electric power during prerotation control by the prerotation control means. The engine supercharging device according to claim 1,
A second bypass passage for communicating the upper and downstream sides of the turbine generator downstream of the electric supercharger in the intake passage;
An on-off valve for opening and closing the second bypass passage;
An intake air temperature detecting means for detecting the intake air temperature,
The power generation control means opens the on-off valve when the intake air temperature detected by the intake air temperature detection means is lower than a predetermined value during the pre-rotation control by the pre-rotation control means, and generates power by the turbine generator. An engine supercharging device characterized by limiting the engine. The engine supercharging device according to claim 1,
The pre-rotation control means closes the bypass valve during pre-rotation control, and
The supercharging device for an engine characterized in that the power generation control means controls the power generation amount of the turbine generator to become the highest in a range where surging of the electric supercharger does not occur during pre-rotation control.

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