JP6107201B2 - Engine start control device for hybrid vehicle - Google Patents

Description

  The present invention relates to an engine start control device applied to a hybrid vehicle provided with a traveling engine and an electric motor.

  An example of a hybrid vehicle includes a traveling engine (internal combustion engine) and an electric motor (hereinafter simply referred to as a motor), and traveling using only the motor according to traveling conditions or the like, It is configured so that it can be switched to traveling only by the engine. For example, in the hybrid vehicle of Patent Document 1, the vehicle travels using only the motor at the start, and the output clutch of the motor used for traveling is transmitted to the engine by connecting the input clutch when the vehicle speed increases to some extent. ing.

  In the hybrid vehicle of Patent Document 2, when the vehicle is running by a motor, torque input from the rotating wheels is transmitted to the engine, thereby being used as assist torque for starting the engine. Thus, it is described that the engine can be started without using a starter motor.

Japanese Patent No. 3214427 JP 2011-201415 A

  In the case of the hybrid vehicle of Patent Document 1, the engine is configured to start with the torque of the motor when the vehicle is running with the motor, and the engine is started when the vehicle is stopped. is not. The hybrid vehicle of Patent Document 2 is also applied when the engine is started during traveling, and assist torque due to wheel rotation cannot be obtained when the vehicle is stopped.

  However, depending on the situation of use of the hybrid vehicle, the engine may be started with the vehicle completely stopped. For example, the engine may be forcibly started to charge a battery mounted on the hybrid vehicle, or warm up to activate a catalyst provided in the engine exhaust pipe. Since the engine repeats compression and expansion according to the position of the piston, for example, during cranking for starting, the rotation speed of the crankshaft changes while the crankshaft makes one revolution. For example, in the expansion stroke toward the bottom dead center, the rotational speed of the crankshaft increases. That is, the acceleration is positive. On the other hand, in the compression process in which the piston moves toward top dead center, the rotational speed of the crankshaft decreases. That is, it becomes a negative acceleration (deceleration).

  For this reason, large vibrations may be transmitted to the vehicle body due to uneven rotation of the engine during low rotation, from cranking to a stable idling state, and this vibration can be felt uncomfortable or vibration can be a source of sound. It becomes. In particular, when the engine is started while the vehicle is stopped, the vibration transmitted to the vehicle body at the beginning of the start is felt to be greater than during traveling. In addition, a diesel engine has a higher compression ratio than a gasoline engine, and the friction of moving parts is large.

  Accordingly, it is an object of the present invention to provide an engine start control device capable of suppressing vibrations when the engine is started in a state where the vehicle is stopped in a hybrid vehicle including an engine and a motor.

One embodiment of the present invention is an engine start control device for a hybrid vehicle comprising a traveling engine (11) and a motor (12), and means for detecting the rotational speed of the engine (11) (31 ), Stop determination means (ST1) for determining whether or not the engine (11) and the motor (12) are stopped, and start start determination means (ST2) for determining start of the engine (11) And means for rotating the motor (12) with the indicated torque when it is determined that both the engine (11) and the motor (12) are stopped and the start of the engine (11) is determined ( ST5), a means (ST6) for calculating the rate of change (ΔV) of the rotational speed of the engine (11), the rate of change (ΔV) is compared with a first threshold (Sh1), and the rate of change (ΔV ) Exceeds the first threshold (Sh1), torque adding means (ST7, ST8) for adding a predetermined torque to the indicated torque, and the engine (11) The rotational speed than the second threshold value (Sh2), and means (ST9) ending with the rotational speed is greater than said second threshold value (Sh2) the addition of the predetermined torque, the first The threshold value (Sh1) is a negative value, and when the rate of change (ΔV) of the rotational speed is a negative value, the absolute value of the rate of change (ΔV) is the first threshold value (Sh1). The predetermined torque is added when the absolute value is larger than the absolute value .

  In one embodiment, the torque adding means (ST7, ST8) adds the predetermined torque when the rate of change (ΔV) in the rotational speed becomes smaller than the first threshold (Sh1). The predetermined torque is added when the first threshold (Sh1) is a negative value and the rate of change (ΔV) is a negative acceleration. An example of the start start determination means (ST2) detects the start of the engine (11) when the start switch (30) of the vehicle is turned on. An example of the engine (11) is a diesel engine.

  ADVANTAGE OF THE INVENTION According to this invention, in the hybrid vehicle provided with the engine and motor for driving | running | working, the vibration generate | occur | produced when starting an engine at the time of a stop can be made small, and an engine can be started smoothly.

The figure which shows typically the structure of the hybrid vehicle provided with the engine starting control apparatus which concerns on the 1st Embodiment of this invention. The time chart which shows the relationship between the change rate of the engine speed of the hybrid vehicle shown by FIG. 1, and a motor torque. The flowchart which shows the flow of a process of the engine starting control apparatus of the hybrid vehicle shown by FIG. The figure which shows typically the structure of the hybrid vehicle provided with the engine starting control apparatus which concerns on the 2nd Embodiment of this invention. The flowchart which shows the flow of a process of the engine starting control apparatus of the hybrid vehicle shown by FIG.

Hereinafter, a hybrid vehicle including an engine start control device according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 3.
A hybrid vehicle 10 shown in FIG. 1 includes a traveling engine 11 and a traveling motor 12. The motor 12 is rotated by electric power supplied from the driving battery. A clutch 13 is disposed between the engine 11 and the motor 12. A power transmission mechanism 17 including a transmission 15 and a differential 16 is connected to the output shaft 14 of the motor 12. The rotation of the output shaft 14 is transmitted to the wheel 18 via the power transmission mechanism 17. An example of the engine 11 is a diesel engine.

  The clutch 13 is controlled by the control unit 20 according to the driving situation of the vehicle 10. When the clutch 13 is connected, the engine 11 and the motor 12 are connected in series, so that the output shaft 14 is rotated by the torque output by the engine 11 and the torque output by the motor 12. When the clutch 13 is disengaged, the wheel 18 is rotated only by the output of the motor 12. The clutch 13 is disengaged by, for example, hydraulic pressure, but an actuator other than hydraulic pressure may be used.

  The hybrid vehicle 10 includes a control unit 20 that electronically controls the engine 11, the motor 12, and the like. The control unit 20 includes an engine control unit 21 that controls the engine 11, a motor control unit 22 that controls the motor 12, an ECU (Electrical Control Unit) 23 that also functions as an engine start control device, and the like. The motor control unit 22 changes the output torque (motor actual torque) generated by the motor 12 by controlling the current supplied to the motor 12 based on the instruction torque (motor instruction torque) applied to the motor 12.

  The hybrid vehicle 10 also has a start switch (main key switch) 30 that is turned on when the engine 11 is started, and a rotational speed that functions as a means for detecting the rotational speed of the engine 11 (the rotational speed of the crankshaft 11a). A sensor 31 and a sensor 32 that can detect whether or not the clutch 13 is connected are provided. Information regarding the rotational speed of the engine 11 detected by the rotational speed sensor 31 is input to the ECU 23 of the control unit 20. As will be described below, the control unit 20 also functions as an engine start control device for smoothly starting the engine 11 when the hybrid vehicle 10 is stopped.

  The ECU 23 of the control unit 20 has a rotational speed change rate Δv (acceleration in the rotational direction) based on a change in the rotational speed of the engine 11 (referred to as engine rotational speed in this specification) output from the rotational speed sensor 31. A computer program for calculating is incorporated. The engine rotation speed may be converted into the number of rotations (rpm) of the crankshaft 11a per minute for convenience of calculation.

  (A), (B), and (C) in FIG. 2 schematically show examples of the motor torque with respect to the time axis (horizontal axis), the change rate Δv of the rotational speed, and the engine rotational speed, respectively. The change rate Δv shown in FIG. 2B corresponds to the slope θ of the tangent line for every minute time of the curve P1 showing the change in the engine rotation speed shown in FIG.

  The control unit 20 constantly monitors whether the change rate Δv of the rotational speed is decreasing or increasing, and temporarily supplies the current supplied to the motor 12 when the change rate Δv becomes smaller than the first threshold value Sh1. Increase. That is, a computer program for performing torque addition control (assist control) for adding a predetermined torque M1 ′ to the indicated torque of the motor 12 indicated by a broken line M1 in FIG. Further, the control unit 20 incorporates a computer program for ending the torque addition control when the engine speed (engine speed) exceeds the second threshold value Sh2.

The process flow of the engine start control device provided with the control unit 20 of the present embodiment will be described below with reference to the flowchart of FIG.
In step ST1 of FIG. 3, it is determined whether the engine 11 is stopped and the motor 12 is stopped. For example, whether or not the vehicle 10 is in a stopped state is determined by a stop determination unit that uses signals indicating the states of the engine control unit 21 and the motor control unit 22. If both the engine 11 and the motor 12 are stopped ("YES" in step ST1), the process proceeds to step ST2. If at least one of engine 11 and motor 12 is moving ("NO" in step ST1), the process is terminated without performing engine start control described below.

  In step ST2, it is determined whether or not the engine 11 has been started. For example, it is determined whether the start switch 30 is turned on. In the case of this embodiment, the start switch 30 and step ST2 function as start start determination means. When it is determined that the engine 11 has started ("YES" in step ST2), the process proceeds to step ST3. If the engine 11 is not started ("NO" in step ST2), the process is terminated without performing the engine start control described below.

  In step ST3, whether or not the clutch 13 is connected is determined by the sensor 32 or the like that detects the operation of the clutch. If the clutch 13 is not connected (“NO” in step ST3), the process proceeds to step ST4, where the clutch 13 is connected. If the clutch 13 is connected (“YES” in step ST3), the process proceeds to step ST5.

  In step ST5, in order to start the engine 11, a current corresponding to the motor command torque (indicated by a broken line M1 in FIG. 2A) is supplied to the motor 12. Based on this command torque (motor), the motor 12 rotates with actual torque (indicated by a solid line M2 in FIG. 2A). That is, this step ST5 functions as a means for rotating the motor 12 based on the command torque when it is determined that the engine has started. When the engine 11 is ignited and the engine 11 rotates on its own, the engine speed (engine speed) increases.

  In step ST6, the rotational speed of the engine 11 is detected by the rotational speed sensor 31, and the output of the rotational speed sensor 31 for every minute time is input to the control unit 20, whereby the rotational speed change rate Δv is calculated. That is, step ST6 functions as a means for calculating the rotational speed change rate Δv. Since the engine 11 repeats compression and expansion according to the position of the piston, for example, in the compression process in which the piston moves to the top dead center, the acceleration in the rotation direction of the crankshaft 11a is reduced, so that the change rate Δv is reduced. On the contrary, in the expansion stroke toward the bottom dead center, the acceleration in the rotation direction of the crankshaft 11a increases, and the rate of change Δv increases.

  In step ST7, the change rate Δv is compared with the first threshold value Sh1. The change rate Δv of the rotational speed corresponds to, for example, the tangential slope θ of the curve P1 indicating the change of the engine rotational speed shown in FIG. Therefore, the change rate Δv takes a positive (positive) value when the acceleration in the rotational direction of the engine increases, and takes a negative (negative) value when the acceleration in the rotational direction decreases (deceleration). The first threshold value Sh1 is a negative value. Therefore, when the change rate Δv is a negative value (deceleration), the change rate Δv being smaller than the first threshold value Sh1 means that the absolute value of the change rate Δv is greater than the absolute value of the threshold value Sh1. To do.

  When the change rate Δv is smaller than the first threshold value Sh1 in step ST7 (“YES” in step ST7), the process proceeds to step ST8. If the change rate Δv is not smaller than the first threshold value Sh1 (“NO” in step ST7), the process jumps to step ST9.

  In step ST8, as shown in FIG. 2A, a predetermined torque M1 ′ is added to the motor command torque. That is, steps ST7 and ST8 function as torque addition means, and torque addition control is executed. The addition of the predetermined torque M1 ′ is performed by increasing the current supplied to the motor 12 more than the current of the indicated torque. The predetermined torque M1 ′ is added when it is detected that the change rate Δv of the rotational speed has changed from a positive value to a negative value (ie, the rotational acceleration has changed from positive to negative). It may be.

  Due to the torque addition control, variation in rotation (rippling) due to a temporary decrease in the rotation speed of the engine 11 is suppressed. Therefore, as indicated by a curve P1 in FIG. The degree of change is smaller than the change in engine speed (indicated by a two-dot chain line P2) when torque addition control is not performed, and a smooth engine start can be realized.

  In step ST9, the engine speed is compared with a second threshold value Sh2. When the rotational speed of the engine 11 is increased to some extent, the rotation of the engine 11 is stabilized and vibrations are reduced, so that the torque addition control can be terminated. Therefore, when the engine speed exceeds the second threshold value Sh2 (“YES” in step ST9), the above-described predetermined torque addition control ends. That is, when the engine rotational speed at which the rotation is stabilized (for example, 500 rpm) is reached, the instruction torque applied to the motor 12 becomes zero, and the actual motor torque for starting becomes zero. If the engine speed does not exceed the second threshold value Sh2 (“NO” in step ST9), the process returns to step ST5, and a series of processes from step ST5 to step ST9 is repeated. Step ST9 functions as means for terminating the addition of the predetermined torque when the rotational speed becomes greater than the second threshold value Sh2.

  As described above, according to the first embodiment, vibration due to rotation unevenness that occurs when the engine 11 is started in a state where the hybrid vehicle 10 is completely stopped is suppressed, and vibration transmitted to the vehicle body is reduced. Riding comfort is improved and the generated sound is reduced. In particular, in the case of a diesel engine, the compression ratio is higher than that of a gasoline engine, and the friction of moving parts is large, so that vibration and noise are likely to be increased. For this reason, the engine start control device of this embodiment is more effective than a gasoline vehicle in suppressing the vibration of a vehicle equipped with a diesel engine.

  FIG. 4 shows an outline of the hybrid vehicle 10 ′ of the second embodiment. This hybrid vehicle 10 ′ is different from the hybrid vehicle 10 of the first embodiment in that no clutch is present between the engine 11 and the motor 12, but the other configuration is the first embodiment. The hybrid vehicle 10 is common. In the hybrid vehicle 10 ′ of the second embodiment, since the engine 11 and the motor 12 are always connected in series, the engine 11 is driven to rotate when traveling by the torque of the motor 12. When traveling with only the torque of the engine 11, the motor 12 rotates in a driven manner.

  FIG. 5 shows the flow of motor control including torque addition control when starting the engine 11 of the hybrid vehicle 10 ′ (shown in FIG. 4) of the second embodiment. Since this hybrid vehicle 10 ′ does not have a clutch between the engine 11 and the motor 12, the hybrid vehicle 10 ′ does not have steps ST3 and ST4 related to the clutch shown in the flowchart (FIG. 3) of the first embodiment. . Since the other processing flow is the same as that of the hybrid vehicle 10 of the first embodiment, the same steps as those in FIG.

  Needless to say, in carrying out the present invention, the specific mode of the engine start control device can be variously changed, including the configuration and arrangement of the engine, motor or various sensors mounted on the hybrid vehicle. For example, a signal from a sensor that detects the operation of a parking brake may be used as a stop determination unit that determines whether or not the vehicle is stopped. In addition to detecting the start operation of the start switch described in the above embodiment, the start start determining means is, for example, an ECU when automatically starting the engine to heat the catalyst to the activation temperature when the engine is cold. A signal output from the ECU or the like may be detected when the engine is automatically started from the idle stop state. Further, the value related to the engine speed may be converted into the number of rotations of the crankshaft per minute (engine speed).

  DESCRIPTION OF SYMBOLS 10,10 '... Hybrid vehicle, 11 ... Engine, 11a ... Crankshaft, 12 ... Motor, 13 ... Clutch, 20 ... Control part, 23 ... ECU, 30 ... Start switch, 31 ... Rotational speed sensor, Δv ... Rotational speed Rate of change, Sh1... First threshold, Sh2.

Claims (3)

A start control device for an engine of a hybrid vehicle including a traveling engine and a motor,
Means for detecting the rotational speed of the engine;
Stop determination means for determining whether or not the engine and the motor are stopped;
Start start determining means for determining start of the engine;
Means for rotating the motor at an indicated torque when it is determined that both the engine and the motor are stopped and the start of the engine is determined;
Means for calculating a rate of change of the rotational speed of the engine;
Torque addition means for comparing the rate of change with a first threshold and adding a predetermined torque to the indicated torque when the rate of change exceeds the first threshold;
Means for comparing the rotational speed of the engine with a second threshold value and terminating the addition of the predetermined torque when the rotational speed is greater than the second threshold value;
Have,
When the first threshold value is a negative value and the rate of change of the rotational speed is a negative acceleration with a negative value, and the absolute value of the rate of change is greater than the absolute value of the first threshold value An engine start control device for a hybrid vehicle, wherein the predetermined torque is added . 2. The engine start control device for a hybrid vehicle according to claim 1 , wherein the start start determination means detects the start of the engine when a start switch of the vehicle is turned on. The engine start control device for a hybrid vehicle according to claim 1 or 2 , wherein the engine is a diesel engine.

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