JP6562505B2 - Electric turbocharger - Google Patents

Description

  The present invention relates to an electric supercharger including a motor that rotationally drives a compressor wheel. In particular, the present invention relates to an electric supercharger that can reduce damage to the clutch when a clutch interposed between a turbine wheel and a motor is connected and the drive of the compressor wheel is switched from the drive by the motor to the drive by the turbine wheel.

  As one of the devices for increasing the output of an internal combustion engine (engine), the exhaust energy (exhaust pressure) of exhaust gas discharged from the internal combustion engine is used to compress and supercharge the air sucked into the internal combustion engine. A turbocharger is known. A conventional general supercharger rotates a turbine wheel provided in an exhaust passage by exhaust to rotate a compressor wheel provided in an intake passage to supercharge intake air. Such a supercharger requires exhaust of the internal combustion engine to drive the compressor wheel, and sufficient exhaust energy necessary to drive the compressor wheel cannot be obtained at the start of the internal combustion engine or in a low rotation range. There may be cases where sufficient supercharging cannot be performed. Therefore, recently, an electric supercharger that incorporates a motor into the supercharger and is driven by the motor has been developed (see, for example, Patent Document 1).

  Patent Document 1 discloses an electric supercharger in which a motor is connected between an intake side turbine (compressor wheel) and an exhaust side turbine (turbine wheel), and a clutch mechanism is provided between the motor and each turbine. (See FIGS. 1 and 2 of Patent Document 1). In the electric supercharger disclosed in Patent Document 1, the intake side clutch between the intake side turbine and the motor is connected and the exhaust side clutch between the exhaust side turbine and the motor is connected at the start of the internal combustion engine or in a low rotation range. The intake side turbine is rotated by driving the motor. When the rotational speed of the internal combustion engine exceeds a predetermined value, it is determined that sufficient exhaust pressure is obtained, the exhaust side clutch is connected, and the exhaust side turbine is driven by exhaust to rotate the intake side turbine. At the same time, the motor is stopped. In other words, at the start of the internal combustion engine or in a low rotation range, the intake side turbine is driven by a motor to perform supercharging by the motor, and when the rotation speed of the internal combustion engine exceeds a certain level, the intake side turbine is driven. Switch from driving by turbine to driving by turbine wheel, and perform supercharging by exhaust.

JP 2013-185547 A

  In an electric supercharger that can be driven by exhaust and driven by a motor, further improvement in reliability is desired. In the electric supercharger of Patent Document 1 described above, a clutch is connected between the exhaust side turbine (turbine wheel) and the motor when the rotational speed of the internal combustion engine exceeds a predetermined value. The clutch is connected regardless of the number of rotations of the wheel and the motor. Therefore, when the rotational speed of the turbine wheel and the rotational speed of the motor are different and the difference between the rotational speeds of the two is large, the load applied to the clutch is large and the damage to the clutch is large. Therefore, in order to avoid this, it is required to reduce damage to the clutch. Further, when the clutch is connected in a state where the rotation speeds of the turbine wheel and the motor are not synchronized, the fluctuation of the rotation speed of the compressor wheel becomes large, which may cause a decrease in supercharging performance.

  The present invention has been made in view of the above circumstances, and one of its purposes is to connect a clutch interposed between the turbine wheel and the motor, and to drive the compressor wheel from the motor to the turbine wheel. An object of the present invention is to provide an electric supercharger capable of reducing damage to a clutch when switching to driving.

  An electric supercharger according to an aspect of the present invention is disposed between a compressor wheel provided in an intake passage of an internal combustion engine, a turbine wheel provided in an exhaust passage of the internal combustion engine, and the compressor wheel and the turbine wheel. And a motor that rotationally drives the compressor wheel. The electric supercharger includes a clutch interposed between the turbine wheel and the motor, and a clutch control unit that connects and disconnects the clutch. The clutch control unit connects the clutch in a state where the turbine wheel and the rotation speed of the motor are synchronized.

  According to the above electric supercharger, when the clutch control unit connects the clutch in a state where the rotation speeds of the turbine wheel and the motor are synchronized, the drive of the compressor wheel is switched from the drive by the motor to the drive by the turbine wheel. , The damage to the clutch can be reduced. Therefore, damage to the clutch can be suppressed, and the reliability of the electric supercharger can be improved. Further, by connecting the clutch in a state where the rotation speeds of the turbine wheel and the motor are synchronized, the clutch can be connected smoothly, and fluctuations in the rotation speed of the compressor wheel can be reduced. Therefore, it is possible to suppress a decrease in supercharging performance.

It is a lineblock diagram showing an example of a system of an internal-combustion engine provided with an electric supercharger concerning an embodiment. It is a block diagram which shows another example of the system of an internal combustion engine provided with the electric supercharger which concerns on embodiment.

  Hereinafter, a specific example of an electric supercharger according to an embodiment of the present invention will be described with reference to the drawings. The same reference numerals in the figure indicate the same names. FIG. 1 is a diagram illustrating an example of a system configuration of an internal combustion engine in a vehicle such as an automobile. First, an outline of a system of an internal combustion engine including an electric supercharger will be described with reference to FIG. 1, and then the electric supercharger according to the embodiment will be described in detail.

[Embodiment 1]
The internal combustion engine (engine) system shown in FIG. 1 includes an engine 100, an intake passage 110, an exhaust passage 130, an electric supercharger 10, and a control device (for example, ECU: engine control unit) 200.

(engine)
The engine 100 is, for example, a gasoline engine, and burns a mixed gas obtained by mixing the air sucked through the intake passage 110 and fuel in the combustion chamber, and outputs rotational power by the expansion force. Gas (exhaust gas) combusted in the combustion chamber is exhausted through the exhaust passage 130.

(Intake passage)
Intake passage 110 supplies engine 100 with air (intake air) taken from the outside. In the intake passage 110, an air cleaner 111 that removes foreign matters in the intake air, a compressor wheel 20 of the electric supercharger 10, an intercooler 112 that cools the intake air compressed by the compressor wheel 20, and the engine 100, in order from the upstream side. And a throttle valve 120 for adjusting the amount of intake air. The throttle valve 120 opens and closes according to the amount of depression of an accelerator pedal (also referred to as a throttle pedal), and the larger the amount of depression of the accelerator pedal, the more the throttle valve 120 opens and the intake amount increases and the engine 100 speed increases. On the downstream side of the air cleaner 111 and the upstream side of the compressor wheel 20, an airflow sensor 121 that detects the amount of intake air taken into the engine 100 is provided.

(Exhaust passage)
The exhaust passage 130 sends out exhaust generated by the engine 100. A turbine wheel 30 of the electric supercharger 10 is provided in the exhaust passage 130. Exhaust gas is guided to a purification device (not shown) through the exhaust passage 130, purified, and then discharged into the atmosphere. An A / F sensor 131 that detects the oxygen concentration in the exhaust gas is provided downstream of the turbine wheel 30 and upstream of the purification device. The air-fuel ratio (A / F) can be calculated from the oxygen concentration detected by the A / F sensor 131. A turbine inlet temperature sensor 61 for detecting the temperature of the exhaust gas flowing into the turbine wheel 30 and a turbine for detecting the exhaust pressure of the exhaust gas are provided on the exhaust gas inlet side (upstream side of the turbine wheel 30) of the electric supercharger 10. An inlet exhaust pressure sensor 62 is provided. Further, a turbine outlet exhaust pressure sensor 63 that detects the exhaust pressure of the exhaust gas flowing out from the turbine wheel 30 is provided on the exhaust outlet side (downstream of the turbine wheel 30) of the electric supercharger 10.

(Control device)
The control device 200 controls various devices such as the engine 100 and the electric supercharger 10. The control device 200 executes a control program for various devices and processes data, a CPU (Central Processing Unit), a memory for storing control programs and data, an input interface for acquiring information from various sensors, and various devices It is comprised by the computer provided with the output interface etc. which send a control signal to.

(Electric supercharger)
The electric supercharger 10 is a device (so-called turbocharger) that compresses intake air using exhaust (exhaust pressure) of the engine 100. The electric supercharger 10 shown in FIG. 1 includes a compressor wheel 20, a turbine wheel 30, a motor 40, a clutch 50, and a clutch control unit 250.

<Compressor wheel / turbine wheel>
The compressor wheel 20 is provided in the intake passage 110 and supercharges intake air by rotating. The turbine wheel 30 is provided in the exhaust passage 130 and rotates by exhaust.

<motor>
The motor 40 is disposed between the compressor wheel 20 and the turbine wheel 30 and can drive the compressor wheel 20 to rotate. The motor 40 is driven by power supplied from a battery (not shown). The power supplied to the motor 40 is controlled by the control device 200, and the rotational speed of the motor 40 can be controlled by the amount of power supplied.

<clutch>
The clutch 50 is interposed between the turbine wheel 30 and the motor 40, and can transmit or cut off the rotational force between the turbine wheel 30 and the motor 40. In the electric supercharger 10 shown in FIG. 1, the compressor wheel 20 is connected to one end of a drive shaft 41 of a motor 40, and the turbine wheel 30 is connected to the other end of the drive shaft 41 via a clutch 50. Yes. Specifically, the other end of the drive shaft 41 is connected to one end of the clutch 50, and the rotating shaft 31 of the turbine wheel 30 is connected to the other end of the clutch 50. When the clutch 50 is connected, the rotational force of the turbine wheel 30 is transmitted to the motor 40 (drive shaft 41), and is transmitted to the compressor wheel 20 via the drive shaft 41. When the clutch 50 is disconnected, the transmission of the rotational force between the turbine wheel 30 and the motor 40 is interrupted.

<Clutch control unit>
The clutch control unit 250 instructs the clutch 50 to be connected and disconnected, and connects and disconnects the clutch 50. The clutch control unit 250 connects the clutch 50 in a state where the rotation speeds of the turbine wheel 30 and the motor 40 are synchronized. In this example, the clutch control unit 250 is incorporated in the control device 200. “Synchronized state” means that the difference in rotational speed between the turbine wheel 30 and the motor 40 is within a predetermined range. For example, the difference in rotational speed between the turbine wheel 30 and the motor 40 is It is mentioned that it is within 10%, and further within 5% with respect to the number of rotations.

The number of revolutions of the motor 40 can be calculated from the amount of power supplied to the motor 40. The rotational speed of the turbine wheel 30 can be acquired from the rotational sensor 32 by providing a rotational sensor 32 that detects the rotational speed of the turbine wheel 30 (rotating shaft 31), for example, as shown in FIG. The rotation speed of the turbine wheel 30 is acquired from the intake air amount (A) acquired from the airflow sensor 121, the air-fuel ratio (A / F) acquired from the A / F sensor 131, and the turbine inlet temperature sensor 61, for example. It is also possible to calculate using the inlet temperature (T _i ), the inlet exhaust pressure (P _i ) acquired from the turbine inlet exhaust pressure sensor 62, and the outlet exhaust pressure (P _o ) acquired from the turbine outlet exhaust pressure sensor 63. Is possible. A method for calculating the rotational speed of the turbine wheel 30 using information from these various sensors will be described below.

When the turbine wheel 30 rotates, the following corrected flow rate and expansion ratio change depending on the rotational speed. There is a fixed relationship between the rotational speed of the turbine wheel 30, the corrected flow rate, and the expansion ratio, and these relationships are determined by the specifications of the electric supercharger 10. Therefore, if the corrected flow rate and the expansion ratio are known, the rotational speed of the turbine wheel 30 can be estimated. Here, the corrected flow rate and the expansion ratio are obtained as follows.
Corrected flow rate = [exhaust flow rate G × √T _i ] / P _i
Expansion ratio = P _i / P _o

  The exhaust flow rate (G) can be regarded as the same as the mixed gas amount burned by the engine 100, and is obtained by adding (A + F) the intake air amount (A) and the fuel amount (F). The fuel amount (F) is obtained by dividing the intake air amount (A) by the air-fuel ratio (A / F) (A / [A / F]).

  Data related to the rotational speed of the turbine wheel 30, the corrected flow rate and the expansion ratio, which are determined in the specification of the electric supercharger 10, are stored in advance in the memory of the control device 200. Then, the rotational speed is calculated from the calculated corrected flow rate and expansion ratio based on the relation data.

  As described above, the rotational speed of the turbine wheel 30 is determined using information from various sensors such as the airflow sensor 121, the A / F sensor 131, the turbine inlet temperature sensor 61, the turbine inlet exhaust pressure sensor 62, and the turbine outlet exhaust pressure sensor 63. It is possible to get. Usually, these various sensors are used in an engine system including a supercharger. In general, the rotation sensor is expensive, which causes an increase in cost. Therefore, by using the above-described various sensors, the rotational speed of the turbine wheel 30 can be obtained without using the rotation sensor 32 that causes an increase in cost, and the cost can be reduced.

(Operation of electric supercharger)
The operation of the electric supercharger 10 will be described. The electric supercharger 10 can rotate the compressor wheel 20 by driving the motor 40 and can connect the clutch 50 to rotate the compressor wheel 20 by driving the turbine wheel 30 by exhaust. That is, the electric supercharger 10 can be driven by exhaust and driven by a motor, and can perform supercharge by exhaust and supercharge by a motor. For example, when the clutch 50 is in a disconnected state, the compressor wheel 20 can be driven only by the motor 40. When the clutch 50 is in the connected state, the compressor wheel 20 is driven by the motor 40 and the turbine wheel 30. In this state, the power supplied to the motor 40 is stopped and the motor 40 is idled, so that the compressor wheel 20 is turned into the turbine wheel. 30 can be driven only. Therefore, the drive of the compressor wheel 20 can be shifted from the drive by the motor 40 to the drive by the turbine wheel 30 by switching the connection and disconnection of the clutch 50 by the clutch control unit 250. That is, it is possible to shift from supercharging by the motor to supercharging by exhaust. Hereinafter, the operation of the electric supercharger 10 will be specifically described.

  At the time of starting the engine 100 or in a low rotation range, the clutch 50 is disconnected by the clutch control unit 250 and the compressor wheel 20 is rotated by driving the motor 40 to perform supercharging by the motor 40.

  Next, in a high speed range where the engine 100 reaches a certain rotational speed, the amount of exhaust discharged from the engine 100 increases, and high exhaust pressure is generated, the clutch control unit 250 connects the clutch 50 and the motor 40 To stop. Thereby, the rotational force of the turbine wheel 30 is transmitted to the compressor wheel 20 via the drive shaft 41, the compressor wheel 20 is rotated by driving the turbine wheel 30, and supercharging by exhaust is performed. That is, the driving of the compressor wheel 20 is switched from the driving by the motor 40 to the driving by the turbine wheel 30, and the supercharging by the motor is shifted to the supercharging by the exhaust. At this time, the clutch control unit 250 connects the clutch 50 in a state where the rotation speeds of the turbine wheel 30 and the motor 40 are synchronized. When shifting from the high rotation range to the low rotation range, the operation shifts to supercharging by the motor again.

(Function and effect)
The electric supercharger 10 according to the above-described embodiment includes the motor 40, so that the motor 40 can compress the compressor wheel 20 even when sufficient exhaust pressure such as at the start of the engine 100 or a low rotation range cannot be obtained. Can be rotated for supercharging. At this time, by disengaging the clutch 50, transmission of the rotational force from the motor 40 to the turbine wheel 30 is cut off, so that the rotation loss of the turbine wheel 30 can be eliminated. Therefore, the drive loss of the motor 40 can be reduced and the supercharging efficiency is improved.

  By connecting the clutch 50 by the clutch control unit 250, the drive of the compressor wheel 20 can be switched from the drive by the motor 40 to the drive by the turbine wheel 30. At that time, by connecting the turbine wheel 30 and the motor 40 in a synchronized state, the clutch 50 can be connected smoothly and damage to the clutch 50 can be reduced. Moreover, compared with the case where it connects without synchronizing the rotation speed of the turbine wheel 30 and the motor 40, the fluctuation | variation of the rotation speed of the compressor wheel 20 can be reduced, and the fall of supercharging performance can be suppressed.

  Further, when the rotational speed of the engine 100 is above a certain level and the throttle valve 120 is closed (for example, when the vehicle is in a deceleration state) while the vehicle is running, the motor 40 is caused to function as a generator. It is also possible to generate electricity. Specifically, the electric circuit is switched so that the motor 40 functions as a generator with the clutch 50 connected. Thereby, the rotational force of the turbine wheel 30 can be transmitted to rotate the motor 40 to generate electric power, and the battery can be charged with the generated electric power.

[Embodiment 2]
With reference to FIG. 2, another example of the system of an internal combustion engine provided with an electric supercharger will be described. The internal combustion engine system of the second embodiment shown in FIG. 2 differs from the above-described internal combustion engine system of the first embodiment shown in FIG. 1 in the configuration of the exhaust passage. Below, it demonstrates centering on difference with Embodiment 1, about the structure similar to Embodiment 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  The exhaust passage 130 shown in FIG. 2 has an exhaust bypass passage 140 that bypasses the turbine wheel 30 in the electric supercharger 10. The exhaust bypass passage 140 branches from the exhaust passage 130 and flows into the exhaust bypass passage 140. A waste gate valve 141 is provided for adjusting the flow rate. The waste gate valve 141 can be controlled by the control device 200.

  By adjusting the flow rate of the exhaust gas flowing into the exhaust bypass passage 140 by the waste gate valve 141, the flow rate of the exhaust gas flowing into the turbine wheel 30 can be adjusted, and the rotation speed of the turbine wheel 30 can be adjusted. Specifically, by opening the waste gate valve 141, the flow rate of the exhaust gas flowing into the turbine wheel 30 is reduced, and the rotational speed of the turbine wheel 30 can be reduced. By closing the waste gate valve 141, the flow rate of the exhaust gas flowing into the turbine wheel 30 is increased, and the rotational speed of the turbine wheel 30 can be increased. That is, the rotational speed of the turbine wheel 30 can be adjusted by adjusting the opening degree of the waste gate valve 141.

  In the engine system shown in FIG. 2, the waste gate valve 141 is opened when the engine 100 is started or in a low rotation range. When the rotational speed of the engine 100 exceeds a certain level, the waste gate valve 141 is gradually closed. Then, when shifting from supercharging by the motor to supercharging by exhaust, the clutch control unit 250 adjusts the opening degree of the waste gate valve 141 so that the rotational speed of the turbine wheel 30 matches the rotational speed of the motor 40. The clutch 50 is connected in a state where the rotation speeds of the turbine wheel 30 and the motor 40 are synchronized. In this system, since the number of revolutions of the turbine wheel 30 can be adjusted by the waste gate valve 141, the number of revolutions of the turbine wheel 30 can be stabilized when shifting from supercharging by the motor to supercharging by exhaust. Therefore, since the clutch 50 can be connected in a state where the rotation speed of the turbine wheel 30 is stable, the clutch 50 can be connected more smoothly, and damage to the clutch 50 can be further reduced. Moreover, the rotation fluctuation of the compressor wheel 20 when the clutch 50 is connected is further reduced, and the deterioration of the supercharging performance is more easily suppressed.

[Modification]
In the electric supercharger 10 shown in FIGS. 1 and 2, the embodiment in which the compressor wheel 20 is connected to one end of the drive shaft 41 of the motor 40 has been described as an example. A clutch may be interposed between the motor 20 and the motor 40. In this case, when the motor 40 functions as a generator, such as in a deceleration state, the clutch between the compressor wheel 20 and the motor 40 is disconnected by the clutch control unit. Thereby, since the rotational force of the turbine wheel 30 is not transmitted to the compressor wheel 20, the rotation loss of the compressor wheel 20 can be eliminated. Therefore, compared with the case where the compressor wheel 20 and the motor 40 are connected and rotate integrally, the power generation efficiency by the motor 40 is improved.

  The present invention is not limited to these exemplifications, is shown by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

  The electric supercharger of the present invention can be suitably used for an automobile engine system.

DESCRIPTION OF SYMBOLS 10 Electric supercharger 20 Compressor wheel 30 Turbine wheel 31 Rotating shaft 32 Rotation sensor 40 Motor 41 Drive shaft 50 Clutch 61 Turbine inlet temperature sensor 62 Turbine inlet pressure sensor 63 Turbine outlet pressure sensor 100 Engine (internal combustion engine)
DESCRIPTION OF SYMBOLS 110 Intake passage 111 Air cleaner 112 Intercooler 120 Throttle valve 121 Air flow sensor 130 Exhaust passage 131 A / F sensor 140 Exhaust bypass passage 141 Wastegate valve 200 Controller 250 Clutch control part

Claims (1)

A compressor wheel provided in an intake passage of the internal combustion engine;
A turbine wheel provided in an exhaust passage of the internal combustion engine;
An electric supercharger provided between the compressor wheel and the turbine wheel, and a motor for rotationally driving the compressor wheel,
A clutch interposed between the turbine wheel and the motor;
A clutch control unit for connecting and disconnecting the clutch,
The exhaust passage has an exhaust bypass passage that bypasses the turbine wheel,
The exhaust bypass passage is provided with a waste gate valve that adjusts the flow rate of the exhaust gas flowing through the exhaust bypass passage.
The clutch control unit adjusts the rotation speed of the turbine wheel by adjusting the flow rate of the exhaust gas flowing into the turbine wheel by the waste gate valve, and the rotation speed of the turbine wheel and the motor is synchronized, Electric supercharger that connects the clutch.

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