Engine rotation fluctuation suppression device

Abstract

To provide a rotation fluctuation suppressing device of an engine which can further suppress rotation fluctuation of the engine.SOLUTION: A rotation fluctuation suppressing device includes an engine and a power generation motor (generator motor) connected with a rotation shaft of the engine to suppress rotation fluctuation of the engine through torque generated by the power generation motor. The rotation fluctuation suppressing device comprises: an exhaust stroke detection part (first detection part) which detects that the engine in an exhaust stroke; and a motor drive control part (drive control part) which makes the power generation motor perform power running on condition that rotation number of the engine is a prescribed value or less and the engine is in the exhaust stroke.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an engine rotational fluctuation suppressing device.

Background Art

[0002] There is known an engine rotational speed fluctuation suppressing device that suppresses fluctuations in the rotational speed of an engine by applying a reaction force by a motor in a direction to cancel out the torque generated by the engine (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the engine rotational speed fluctuation suppressing device disclosed in Patent Document 1, for example, during the combustion stroke of the engine, the force by which the piston descends due to combustion and the reaction force by which the motor suppresses the rotational fluctuations of the engine are combined. As a result, there has been a risk that the piston vibrates and the vibration of the engine increases.

[0005] An object of the present invention is to provide an engine rotational fluctuation suppressing device capable of further suppressing rotational fluctuations of an engine.

Means for Solving the Problems

[0006] To achieve the above object, an engine rotational fluctuation suppressing device of the present invention includes an engine and a power generation motor connected to the rotational shaft of the engine, and is an engine rotational fluctuation suppressing device that suppresses rotational fluctuations of the engine by torque generated by the power generation motor, and includes a first detection unit that detects that the engine is in an exhaust stroke. A second detection unit that detects whether the engine is in the combustion stroke, and, on the condition that the engine is in the combustion stroke, the generator motor is not operated in regenerative mode.The present invention is characterized by comprising a drive control unit that causes the generator motor to operate under the condition that the rotational speed of the engine is below a predetermined value and the engine is in the exhaust stroke.

[0007] According to this configuration, When the engine is in the combustion stroke, the generator / motor does not perform control to suppress engine rotational fluctuations, thus preventing an increase in engine rotational fluctuations during the combustion stroke. This allows for even greater suppression of engine rotational fluctuations.

[0010] Furthermore, the engine rotation fluctuation suppression device according to the present invention further includes a third detection unit that detects the difference between the target rotational speed and the actual rotational speed of the engine, and the drive control unit determines the current value to be applied when the generator motor is driven based on the difference.

[0011] This configuration allows for the appropriate setting of the amount of engine speed fluctuation suppression depending on the engine's operating state.

[0012] Furthermore, the engine rotation fluctuation suppression device according to the present invention further comprises a fourth detection unit for detecting the accelerator opening of the engine, and the drive control unit determines the current value to be applied when the generator motor is driven based on the accelerator opening.

[0013] This configuration allows for the appropriate setting of the amount of engine speed fluctuation suppression in response to the driver's instructions to the engine. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide an engine rotation fluctuation suppression device that can further suppress engine rotation fluctuations. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is a block diagram showing a schematic configuration of an engine rotation fluctuation suppression device according to an embodiment. [Figure 2] Figure 2 is a functional block diagram showing an example of the functional configuration of the ECU included in the engine speed fluctuation suppression device. [Figure 3A] FIG. 3A is a graph showing an example of the engine speed and the vibration acceleration of the engine mount when the rotation speed fluctuation suppression control by the rotation fluctuation suppression device is not performed. [Figure 3B] FIG. 3B is a graph showing an example of the suppression effect of the rotation speed fluctuation by the rotation fluctuation suppression device. [Figure 4] FIG. 4 is a graph showing an example of the suppression of the rotation speed fluctuation in the comparative example. [Figure 5] FIG. 5 is a flowchart showing an example of the processing flow performed by the rotation fluctuation suppression device according to the embodiment.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0017] (Schematic Configuration of Engine Rotation Fluctuation Suppression Device) Using FIG. 1, the schematic configuration of the engine rotation fluctuation suppression device 10 according to an embodiment of the present invention will be described. FIG. 1 is a block diagram showing the schematic configuration of the engine rotation fluctuation suppression device according to the embodiment.

[0018] The engine rotation fluctuation suppression device 10 is mounted on a vehicle (not shown) and includes an engine 12, a power generation motor 13, an ECU 15, a crank angle sensor 16, a rotation speed sensor 17, an inverter 18, a converter 19, and a battery 20.

[0019] The engine 12 is, for example, a gasoline engine and is a drive source of the vehicle.

[0020] The power generation motor 13 is, for example, a permanent magnet synchronous motor connected to the engine 12. The rotating shaft of the power generation motor 13 is mechanically connected to the crankshaft 14 of the engine 12 via a gear (not shown). When starting the engine 12, the power generation motor 13 acts as a starter motor by performing a power running operation. Further, by performing a power running operation, the power generation motor 13 adds its driving torque to the driving torque of the engine 12 to assist the driving force of the vehicle, constituting a so-called mild hybrid system. Furthermore, the power generation motor 13 generates electricity by performing a regenerative operation by the rotational torque of the crankshaft 14, and charges the battery 20 described later. When the output required for the power generation motor 13 is smaller than the output of the battery 20, the engine 12 may be stopped and the vehicle may be driven only by the power generation motor 13. Note that the power generation motor 13 is an example of the power generation electric motor in the present disclosure.

[0021] The ECU 15 controls the rotational fluctuation suppression device 10 by acquiring information from various sensors and performing necessary calculations.

[0022] The crank angle sensor 16 transmits the rotational driving force of the engine 12.

[0023] The rotation speed sensor 17 detects the rotation speed of the power generation motor 13. The rotation speed sensor 17 is, for example, a resolver.

[0024] The inverter 18 converts the AC voltage output by the power generation motor 13 into a DC voltage. Also, the inverter 18 converts the DC voltage output by the converter 19 into an AC voltage.

[0025] The converter 19 steps down the DC voltage output by the inverter 18. Also, the converter 19 steps up the DC voltage output by the battery 20.

[0026] The battery 20 is a rechargeable secondary battery, for example, a lithium ion battery.

[0027] When starting the engine 12, the rotational fluctuation suppression device 10 boosts the DC voltage output from the battery 20 using a converter 19, and converts the boosted DC voltage into AC voltage using an inverter 18. The rotational fluctuation suppression device 10 then supplies the AC voltage converted by the inverter 18 to the generator motor 13. As a result, the generator motor 13 is driven, and the engine 12 is cranked by the generator motor 13. When the rotational speed of the engine 12's crankshaft has increased to the rotational speed required for starting due to the cranking, the spark plug of the engine 12 sparks, and the engine 12 starts.

[0028] Furthermore, while the engine 12 is running, the rotational fluctuation suppression device 10 drives the vehicle by powering the generator motor 13, using the driving torque generated by the engine 12 and the driving torque generated by the generator motor 13.

[0029] Furthermore, the rotational fluctuation suppression device 10 regenerates the generator motor 13 when the vehicle decelerates or when the capacity of the battery 20 falls below a predetermined value. At this time, the AC voltage from the generator motor 13 is converted to a DC voltage by the inverter 18, the DC voltage output from the inverter 18 is stepped down by the converter 19, and the stepped-down DC voltage is supplied to the battery 20, thereby charging the battery 20.

[0030] In Figure 1, the rotational fluctuation suppression device 10 may further include a drive motor powered by the battery 20.

[0031] (ECU Functional Configuration) Using Figure 2, the functional configuration of the ECU 15 included in the engine speed fluctuation suppression device 10 will be explained. Figure 2 is a functional block diagram showing an example of the functional configuration of the ECU included in the engine speed fluctuation suppression device.

[0032] The ECU 15 of the rotational fluctuation suppression device 10 includes an engine operating state detection unit 31, a crank angle detection unit 32, an engine speed detection unit 33, an exhaust stroke detection unit 34, a combustion stroke detection unit 35, a rotational speed fluctuation amount detection unit 36, an accelerator opening degree detection unit 37, and a motor drive control unit 38.

[0033] The engine operating state detection unit 31 determines whether or not the engine 12 is running. For example, the engine operating state detection unit 31 determines that the engine 12 is running when an ignition switch or power switch (not shown) mounted on the vehicle is turned ON.

[0034] The crank angle detection unit 32 detects the rotation angle of the crankshaft 14 of the engine 12. Specifically, the crank angle detection unit 32 detects the rotation angle of the crankshaft 14 by means of a crank angle sensor (not shown) which detects a plurality of protrusions formed on the outer circumference of the crankshaft 14 using an electromagnetic pickup.

[0035] The engine speed detection unit 33 detects the rotational speed of the engine 12. The engine speed detection unit 33 detects the rotational speed of the engine 12, for example, by using a rotational speed sensor that utilizes a magnetic pickup.

[0036] The exhaust stroke detection unit 34 detects that the engine 12 is in the exhaust stroke. Specifically, the exhaust stroke detection unit 34 detects that the engine 12 is in the exhaust stroke based on the crank angle detected by the crank angle detection unit 32. Note that the exhaust stroke detection unit 34 is an example of the first detection unit in this disclosure.

[0037] The combustion stroke detection unit 35 detects that the engine 12 is in the combustion stroke. Specifically, the combustion stroke detection unit 35 detects that the engine 12 is in the combustion stroke based on the crank angle detected by the crank angle detection unit 32. Note that the combustion stroke detection unit 35 is an example of a second detection unit in this disclosure.

[0038] The rotational speed fluctuation detection unit 36 ​​detects the difference between the target rotational speed and the actual rotational speed of the engine 12. The rotational speed fluctuation detection unit 36 ​​is an example of a third detection unit in this disclosure.

[0039] The accelerator pedal position detection unit 37 detects the accelerator pedal position in accordance with the amount the accelerator pedal is pressed. Specifically, the accelerator pedal position detection unit 37 detects the accelerator pedal position using an accelerator position sensor (not shown) or the like, which detects the amount the accelerator pedal is operated. The accelerator pedal position detection unit 37 is an example of a fourth detection unit in this disclosure.

[0040] The motor drive control unit 38 controls the operating state of the generator motor 13 according to the operating state of the engine 12. Specifically, the motor drive control unit 38 operates the generator motor 13 under the condition that the rotational speed of the engine 12 is below a predetermined value and the engine 12 is in the exhaust stroke. The motor drive control unit 38 also does not operate the generator motor 13 under regenerative operation if the engine 12 is in the combustion stroke. Furthermore, the motor drive control unit 38 determines the current value to be applied when operating the generator motor 13 under power based on the difference between the target rotational speed and the actual rotational speed of the engine 12. The motor drive control unit 38 also determines the current value to be applied when operating the generator motor 13 under power based on the accelerator opening.

[0041] (Effect of suppressing engine speed fluctuations) The effect of the rotational speed fluctuation suppression device 10 on suppressing rotational speed fluctuations will be explained using Figures 3A, 3B, and 4. Figure 3A is a graph showing an example of engine rotational speed and engine mount vibration acceleration when rotational speed fluctuation suppression control is not performed by the rotational speed fluctuation suppression device. Figure 3B is a graph showing an example of the effect of the rotational speed fluctuation suppression device on suppressing rotational speed fluctuations. Figure 4 is a graph showing an example of the effect of suppressing rotational speed fluctuations in a comparative example.

[0042] Figures 3A and 3B show an example of the operation of the rotational fluctuation suppression device 10 of this embodiment. The horizontal axis in Figures 3A and 3B represents time t. The vertical axis in Figure 3A shows the engine speed R and the vibration acceleration a of the vehicle's front engine mount. The vertical axis in Figure 3B shows the engine speed R, the currents Id and Iq flowing to the generator motor 13, and the vibration acceleration a of the vehicle's front engine mount. Note that currents Id and Iq are obtained by converting the three-phase current to orthogonal two-phase current when the generator motor 13 is a three-phase AC motor. This conversion is performed by the well-known Clark transformation.

[0043] As shown in Figure 3A, if the rotational speed fluctuation suppression device 10 does not suppress rotational speed fluctuations, the engine speed R will fluctuate over time. The vibrations generated by the fluctuations in engine speed R are then transmitted to the engine mount. As a result, a vibration acceleration a, as shown in Figure 3A, is generated in the engine mount. This vibration acceleration a is transmitted to the vehicle occupants and may cause them discomfort.

[0044] In this embodiment, the rotational fluctuation suppression device 10 operates the generator motor 13 under power during the exhaust stroke of the engine 12. Furthermore, the rotational fluctuation suppression device 10 does not supply currents Id and Iq to the generator motor 13 during the combustion stroke of the engine 12.

[0045] As a result, as shown in Figure 3B, the vibration (speed fluctuation) of the engine speed R is reduced compared to Figure 3A, where the speed fluctuation suppression device 10 is not in operation. Although the horizontal axis scales of Figure 3A and Figure 3B are different, making it appear as if the phase of the engine speed R is different, it can be seen that the amplitude of the engine speed R in Figure 3B is clearly smaller than in Figure 3A.

[0046] Furthermore, in Figure 3B, compared to Figure 3A, the vibration (speed fluctuation) of the engine speed R is reduced, and as a result, the vibration acceleration a of the engine mount is also reduced. Therefore, the vibration transmitted to the vehicle occupants is also reduced.

[0047] As shown in Figure 3B, the rotational fluctuation suppression device 10 supplies currents Id and Iq to the generator motor 13 during the exhaust stroke of the engine 12 to perform power operation. The rotational fluctuation suppression device 10 then stops supplying power to the generator motor 13 during the combustion stroke of the engine 12.

[0048] The rotational fluctuation suppression device 10 of this embodiment determines the amount of current Id and current Iq (current value) to be supplied to the generator motor 13 during the exhaust stroke, for example, according to the difference between the target rotational speed and the actual rotational speed of the engine 12. For example, the larger the difference, the greater the amount of current Id and current Iq. The difference between the target rotational speed and the actual rotational speed of the engine 12 is detected by the rotational speed fluctuation detection unit 36 ​​(see Figure 2) described above. The rotational fluctuation suppression device 10 then applies the applied current determined according to the detected difference to the generator motor 13 in the exhaust stroke of the next cycle of the engine 12, for example, by reflecting it in PI control.

[0049] Furthermore, the rotational fluctuation suppression device 10 of this embodiment determines the amount (current value) of current Id and current Iq to be supplied to the generator motor 13 during the exhaust stroke, according to the accelerator opening. For example, the larger the accelerator opening, the greater the amount of current Id and current Iq. The accelerator opening is detected by the accelerator opening detection unit 37 (see Figure 2) described above. The rotational fluctuation suppression device 10 then applies the applied current determined according to the detected accelerator opening to the generator motor 13 in the exhaust stroke of the next cycle of the engine 12, for example, by reflecting it in PI control.

[0050] Furthermore, it is desirable that the rotational fluctuation suppression device 10 performs the rotational fluctuation suppression control of the engine 12 only in the range below a predetermined rotational speed (for example, the range below 2000 revolutions per minute). This is to prevent the generator motor 13 from operating unnecessarily in the high-speed range of the engine 12 in order to charge the battery 20 from the generator motor 13. Note that the predetermined rotational speed will vary depending on the specifications of the engine 12 and will be set as appropriate.

[0051] (Example of suppression of engine speed fluctuations in comparative example) Using Figure 4, we will explain an example of suppressing rotational speed fluctuations in engine 12 using a comparative example. Figure 4 is a graph showing an example of suppressing rotational speed fluctuations in a comparative example.

[0052] In Figure 4, the engine 12 operates the generator motor 13 with power during the exhaust stroke, and the engine 12 operates the generator motor 13 with regenerative braking during the combustion stroke. As a result, the vibration (speed fluctuation) of the engine speed R is indeed reduced.

[0053] However, during the combustion stroke of engine 12, the vibration acceleration a of the engine mount increases drastically. As mentioned above, this vibration is caused by the combination of the downward force of the piston due to engine combustion and the reaction force of the motor suppressing the rotational fluctuations of the engine.

[0054] Comparing Figure 4 with Figure 3B, it can be seen that operating the rotational fluctuation suppression device 10 of this embodiment suppresses the increase in the vibration acceleration a of the engine mount during the combustion stroke.

[0055] (Process flow performed by the rotational fluctuation suppression device) The processing flow of the rotational fluctuation suppression device 10 will be explained using Figure 5. Figure 5 is a flowchart showing an example of the processing flow of the rotational fluctuation suppression device according to this embodiment.

[0056] The engine operating state detection unit 31 determines whether the engine 12 is running (step S11). If it is determined that the engine 12 is running (step S11: Yes), the process proceeds to step S12. On the other hand, if it is not determined that the engine 12 is running (step S11: No), the determination in step S11 is repeated.

[0057] In step S11, if it is determined that the engine 12 is running, the engine speed detection unit 33 determines whether the rotational speed of the engine 12 is less than or equal to a predetermined value (for example, 2000 revolutions per second) (step S12). If it is determined that the rotational speed of the engine 12 is less than or equal to the predetermined value (step S12: Yes), the process proceeds to step S13. On the other hand, if it is not determined that the rotational speed of the engine 12 is less than or equal to the predetermined value (step S12: No), the process proceeds to step S14.

[0058] In step S12, if it is determined that the rotational speed of the engine 12 is below a predetermined value, the exhaust stroke detection unit 34 determines whether the engine 12 is in the exhaust stroke (step S13). If it is determined that the engine 12 is in the exhaust stroke (step S13: Yes), the process proceeds to step S15. On the other hand, if it is not determined that the engine 12 is in the exhaust stroke (step S13: No), the process proceeds to step S19.

[0059] Returning to step S12, if it is determined in step S12 that the rotational speed of the engine 12 is not below a predetermined value, the motor drive control unit 38 causes the generator motor 13 to operate regeneratively (step S14). Then, return to step S12.

[0060] Returning to step S13, if it is determined in step S13 that the engine 12 is in the exhaust stroke, the rotational speed fluctuation detection unit 36 ​​obtains the difference between the target rotational speed and the actual rotational speed of the engine 12 (step S15).

[0061] Next, the motor drive control unit 38 determines the current applied to the generator motor 13 according to the difference between the target rotational speed and the actual rotational speed of the engine 12 (step S16).

[0062] Then, the motor drive control unit 38 operates the generator motor 13 by applying the current determined in step S16 to the generator motor 13 (step S17). More specifically, the motor drive control unit 38 applies a current to the generator motor 13 corresponding to the difference between the target rotational speed and the actual rotational speed of the engine 12 during the exhaust stroke of the next cycle of the engine 12.

[0063] Next, the engine operating state detection unit 31 determines whether the engine 12 is running (step S18). If it is determined that the engine 12 is running (step S18: Yes), the process returns to step S12. On the other hand, if it is not determined that the engine 12 is running (step S18: No), the rotational fluctuation suppression device 10 terminates the process shown in Figure 5.

[0064] Returning to step S13, if it is determined in step S13 that the engine 12 is not in the exhaust stroke, the motor drive control unit 38 reduces the current applied to the generator motor 13 to 0 (step S19).

[0065] Next, the engine operating state detection unit 31 determines whether the engine 12 is running (step S20). If it is determined that the engine 12 is running (step S20: Yes), the process returns to step S12. On the other hand, if it is not determined that the engine 12 is running (step S20: No), the rotational fluctuation suppression device 10 terminates the process shown in Figure 5.

[0066] Note that the processing flow shown in Figure 5 is just one example, and the processing flow performed by the rotational fluctuation suppression device 10 is not limited to the flow shown in Figure 5.

[0067] For example, instead of the rotational speed fluctuation detection unit 36 ​​acquiring the difference between the target rotational speed and the actual rotational speed of the engine 12, the accelerator opening detection unit 37 may detect the accelerator opening. The motor drive control unit 38 may then determine the current to be applied to the generator motor 13 according to the accelerator opening, and operate the generator motor 13 by applying the determined current to the generator motor 13. Furthermore, the motor drive control unit 38 may determine the current to be applied to the generator motor 13 using both the difference between the target rotational speed and the actual rotational speed of the engine 12 detected by the rotational speed fluctuation detection unit 36 ​​and the accelerator opening detected by the accelerator opening detection unit 37.

[0068] (Effects of the embodiment) As described above, the rotational fluctuation suppression device 10 of the embodiment comprises an engine 12 and a generator motor 13 (generator motor) connected to the rotating shaft of the engine 12, and suppresses rotational fluctuations of the engine 12 by the torque generated by the generator motor 13, and comprises an exhaust stroke detection unit 34 (first detection unit) that detects when the engine 12 is in the exhaust stroke, and a motor drive control unit 38 (drive control unit) that causes the generator motor 13 to operate under the condition that the rotational speed of the engine 12 is below a predetermined value and the engine 12 is in the exhaust stroke.Therefore, rotational fluctuations of the engine 12 can be further suppressed.

[0069] Furthermore, the rotational fluctuation suppression device 10 of this embodiment is further equipped with a combustion stroke detection unit 35 (second detection unit) that detects whether the engine 12 is in the combustion stroke, and the motor drive control unit 38 (drive control unit) does not operate the generator motor 13 in regenerative mode on the condition that the engine 12 is in the combustion stroke. Therefore, when the engine 12 is in the combustion stroke, the generator motor 13 does not perform control to suppress rotational fluctuations of the engine 12, thereby preventing an increase in rotational fluctuations of the engine 12 during the combustion stroke.

[0070] Furthermore, the rotational fluctuation suppression device 10 of this embodiment is further equipped with a rotational speed fluctuation detection unit 36 ​​(third detection unit) that detects the difference between the target rotational speed and the actual rotational speed of the engine 12. The motor drive control unit 38 (drive control unit) determines the current value to be applied when powering the generator motor 13 based on the difference. Therefore, the amount of rotational fluctuation suppression of the engine 12 can be appropriately set according to the operating state of the engine 12.

[0071] Furthermore, the rotational fluctuation suppression device 10 of this embodiment is further equipped with an accelerator opening detection unit 37 (fourth detection unit) that detects the accelerator opening of the engine 12, and the motor drive control unit 38 (drive control unit) determines the current value to be applied when the generator motor 13 is driven based on the accelerator opening.Therefore, the amount of rotational fluctuation suppression of the engine 12 can be changed according to the driver's driving instructions to the engine 12.

[0072] Although embodiments of the present invention have been described above, these embodiments are presented as examples only and are not intended to limit the scope of the invention. This novel embodiment can be implemented in various other forms. Furthermore, various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. Moreover, this embodiment is included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0073] 10. Rotational fluctuation suppression device 12 Engines 13. Generator motor (generator-motor) 14 Crankshaft 15 ECU 16 Crank angle sensor 17. Rotation speed sensor 18 Inverters 19 Converters 20 batteries 31 Engine operating state detection unit 32 Crank angle detection unit 33 Engine speed detection unit 34 Exhaust stroke detection unit (first detection unit) 35 Combustion Stroke Detection Unit (Second Detection Unit) 36. Rotational speed fluctuation detection unit (third detection unit) 37. Accelerator opening detection unit (fourth detection unit) 38 Motor drive control unit (drive control unit)

Claims

1. An engine rotation fluctuation suppression device comprising an engine and a generator-motor connected to the rotating shaft of the engine, wherein the rotation fluctuation of the engine is suppressed by the torque generated by the generator-motor, A first detection unit that detects that the engine is in the exhaust stroke, A second detection unit that detects whether the engine is in the combustion stroke, The system includes a drive control unit that, under the condition that the engine is in the combustion stroke, does not perform regenerative operation on the generator motor, and under the condition that the engine speed is below a predetermined value and the engine is in the exhaust stroke, causes the generator motor to perform power operation. An engine speed fluctuation suppression device.

2. The engine is further equipped with a third detection unit that detects the difference between the target rotational speed and the actual rotational speed. The drive control unit determines the current value to be applied when powering the generator motor based on the difference amount. The engine rotation fluctuation suppression device according to claim 1.

3. The engine is further provided with a fourth detection unit for detecting the throttle opening of the engine, The drive control unit determines the current value to be applied when the generator motor is driven into operation, based on the accelerator opening. The engine rotation fluctuation suppression device according to claim 1.

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