JP2009208686A - Engine start control method and engine start control device of hybrid driving electric vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain speed-up pattern of engine rotation speed constant in starting an internal combustion engine of a hybrid driving electric vehicle. <P>SOLUTION: The internal combustion engine 1 and an electric motor 2 are connected through a first clutch CL 1, and an electric motor 2 and a driving wheel are connected through a second clutch CL 2. The second clutch CL 2 is made into a half-clutch status, the first clutch CL 1 is fastened by fastening pressure according to predetermined transmission torque, and the internal combustion engine 1 is started into operation by running torque of electric motor 2. If engine rotation speed hereat is at a target rotation speed or lower and the second clutch CL 2 does not reach a slip limit, the rotation speed of the electric motor 2 is increased and if the engine rotation speed is at the target rotation speed or lower and the second clutch CL 2 has reached the slip limit, the fastening pressure of the first clutch CL 1 is boosted. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to start control of a running internal combustion engine of a hybrid drive electric vehicle using an internal combustion engine and an electric motor as power sources.

  In a hybrid electric drive vehicle that uses an internal combustion engine and an electric motor as power sources, the engine is started using the rotational torque of the electric motor. When it is necessary to start the internal combustion engine while the vehicle is traveling, a rotational torque for cranking is applied to the engine by fastening a clutch that connects the electric motor and the engine.

Regarding engine start control in such a case, Patent Document 1 proposes to control the clutch engagement hydraulic pressure so that the engine rotation speed during the start operation matches the target rotation speed.
JP 2006-298078 A

  Even if the hydraulic pressure for clutch engagement is the same, the torque actually transmitted from the electric motor to the engine is not necessarily the same due to wear of the clutch or the like. Even if only the clutch hydraulic pressure is controlled, the torque acting on the engine varies depending on the rotational speed of the electric motor when the engine is started.

  For this reason, it is difficult to keep the rotational speed increase pattern constant at all times with the conventional engine starting method. However, if the rotational speed varies, the air-fuel ratio of the air-fuel mixture supplied to the engine also varies, which causes exhaust emission to deteriorate.

  Accordingly, it is an object of the present invention to ensure that the engine rotational speed is always increased in a constant pattern when the engine is started while the hybrid drive electric vehicle is traveling.

  To achieve the above object, the present invention provides a hybrid drive electric vehicle in which an internal combustion engine and an electric motor are connected via a first clutch, and the electric motor and drive wheels are connected via a second clutch. In the engine start control method of a hybrid drive electric vehicle that is applied to the above and starts the internal combustion engine with the rotational torque of the electric motor while the vehicle is running, the second clutch is set to a half-clutch state and the first clutch is engaged at a predetermined pressure. Then, the engine rotational speed after engaging the first clutch is compared with a preset target rotational speed to determine whether the second clutch has reached the slip limit, and the engine rotational speed is equal to or lower than the target rotational speed. If the second clutch does not reach the slip limit, the rotational speed of the electric motor is increased so that the engine rotational speed during startup If equal to or less than the target rotational speed and the second clutch has reached the slip limit, pressure increasing the engagement pressure of the first clutch, and so.

  The present invention is also applied to a hybrid drive electric vehicle in which an internal combustion engine and an electric motor are connected via a first clutch, and the electric motor and a drive wheel are connected via a second clutch. In the engine start control device for a hybrid electric vehicle that starts the internal combustion engine with the rotational torque of the electric motor, means for bringing the second clutch into a half-clutch state, means for fastening the first clutch at a predetermined pressure, Means for comparing the engine speed after engaging the first clutch with a preset target speed, means for determining whether the second clutch has reached the slip limit, and the engine speed is the target speed And means for increasing the rotational speed of the electric motor and the starting engine when the second clutch has not reached the slip limit. If the gin rotational speed and equal to or less than the target rotational speed is a second clutch reaches the slip limit, and includes a means for pressure increase the engagement pressure of the first clutch, the.

  When the engine rotation speed is equal to or lower than the target rotation speed and the second clutch has not reached the slip limit, the engine rotation speed is controlled to the target rotation speed by increasing the rotation speed of the electric motor. . On the other hand, when the engine rotational speed is equal to or lower than the target rotational speed and the second clutch has reached the slip limit, the rotational speed of the electric motor can be increased by increasing the engagement pressure of the first clutch. Instead, the torque transmitted to the internal combustion engine is increased to control the engine speed to the target speed.

  Therefore, even if the transmission torque of the first clutch varies, the rotational speed of the electric motor and the engagement pressure of the first clutch are selectively controlled according to the slip condition of the second clutch. It is possible to always match the rotational speed at the start of the engine with a predetermined acceleration pattern. Therefore, it is possible to prevent the exhaust emission from deteriorating due to the engine starting while the vehicle is running.

  FIG. 1 shows a schematic configuration of a drive system of a hybrid drive electric vehicle to which the present invention is applied. FIG. 2 shows an engine start routine while the vehicle is running, which is executed by the controller according to the present invention.

  Referring to (a) of FIG. 1, the hybrid drive electric vehicle includes an internal combustion engine 1 and an electric motor 2 as a driving power source.

  The internal combustion engine 1 is connected to the electric motor 2 via the first clutch CL1. The output of the electric motor 2 is input to the automatic transmission 3 via the second clutch CL2. The output of the automatic transmission 3 drives the drive wheels of the hybrid drive electric vehicle via the deceleration rare 4. The electric motor 3 functions as a generator by the rotational torque input from the automatic transmission 3 when the vehicle is braking or coasting.

  Referring to FIG. 1B, the hybrid drive electric vehicle controls the operation of the internal combustion engine 1, the operation of the electric motor 2, the engagement and release of the first clutch, and the engagement and release of the second clutch. The controller 5 is provided.

  The controller 5 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). It is also possible to configure the controller 5 with a plurality of microcomputers.

  The present invention relates to an internal combustion engine 1 when the hybrid drive electric vehicle constructed as described above is running while being driven by the power of the electric motor 2 or while driving the electric motor 2 as a generator by braking or inertia running. The present invention relates to control when starting the engine.

  For this control, detection signals are input to the controller 5 from a speed sensor 11 that detects the rotational speed of the internal combustion engine 1 and a rotational speed sensor 13 that detects the output rotational speed of the automatic transmission 3. Further, the rotational speed of the electric motor 2 is input from the inverter 12 that controls the operation of the electric motor 2.

  With reference to FIG. 2, a start routine of the internal combustion engine 1 executed by the controller 5 based on these input signals while the hybrid drive electric vehicle is traveling will be described. This routine is executed based on a request for starting the internal combustion engine 1.

  In step S1, the controller 5 puts the second clutch CL2 in a half-clutch state, while increasing the target rotational speed of the electric motor 2 to compensate for a decrease in the transmission torque of the clutch CL2.

  In step S2, the first clutch CL1 is engaged with a predetermined engagement pressure. Thereby, the rotation of the electric motor 2 is transmitted to the internal combustion engine 1, and cranking of the internal combustion engine 1 is started. Here, the predetermined engagement pressure means an engagement pressure at which the first clutch CL1 is engaged in a state where a certain amount of slip is permitted.

  The reason why the second clutch CL2 is set to the half-clutch state in step S1 is to prevent the shock caused by the engagement of the first clutch CL1 from being transmitted to the automatic transmission 3. Note that the controller 5 causes the internal combustion engine 1 to start combustion of the air-fuel mixture by supplying fuel and igniting the air-fuel mixture by separate routines with respect to the internal combustion engine 1 that has started cranking.

  In step S3, the rotational speed of the internal combustion engine 1 is compared with a predetermined target rotational speed. The target rotation speed is a value corresponding to a speed increase pattern set in advance according to the elapsed time from the execution of step S2. Each time step S3 is executed, the controller 5 obtains a target rotational speed by referring to a map stored in advance in the ROM based on the elapsed time from the execution of step S2.

  When the rotation speed of the internal combustion engine 1 is equal to or lower than the target rotation speed, the process of step S4 is performed. When the rotation speed of the internal combustion engine 1 exceeds the target rotation speed, the process of step S8 is performed.

  In step S4, a correction value for the rotational speed of the electric motor 2 is calculated based on the difference between the target rotational speed of the internal combustion engine 1 and the actual rotational speed. Specifically, the correction value of the rotational speed of the electric motor 2 is increased as the difference between the target rotational speed of the internal combustion engine 1 and the actual rotational speed is larger. For this purpose, a map defining these relationships is stored in the ROM of the controller 5 in advance, and the controller 5 searches the map based on the difference between the target rotational speed and the actual rotational speed of the internal combustion engine 1 to search the electric motor. A correction value for the rotational speed of 2 is obtained.

  In step S5, the slip ratio of the second clutch CL2 is calculated, and it is determined whether or not the slip ratio has reached the slip limit value.

  When the slip ratio of the second clutch CL2 is equal to or less than the slip limit value, the controller 5 increases the rotational speed of the electric motor 3 based on the correction value obtained in step S4 in step S6. An increase in the rotational speed of the electric motor 3 causes an increase in the rotational speed of the internal combustion engine 1. After the process of step S6, the controller 5 performs the process of step S8.

  If the slip ratio of the second clutch CL2 has reached the slip limit value, the controller 5 increases the engagement pressure of the first clutch in step S7. As a result, slippage of the first clutch is reduced, so that the rotational speed of the internal combustion engine 1 increases even if the rotational speed of the electric motor 2 remains the same. After the process of step S7, the controller 5 performs the process of step S8.

  In step S8, the controller 5 compares the rotational speed of the internal combustion engine 1 with a predetermined complete explosion speed.

  When the rotation speed of the internal combustion engine 1 is equal to or lower than the complete explosion speed, the processes after step S3 are repeated. When the rotational speed of the internal combustion engine 1 exceeds the complete explosion speed, the controller 5 ends the routine.

  With reference to FIG. 3 to FIG. 6, the effect of the above control will be described.

  FIG. 3 shows a start pattern when the internal combustion engine start control according to the prior art is applied to the above hybrid drive electric vehicle.

  In this case, first, as shown in (e), the second clutch CL2 is put into a half-clutch state, and as shown in (d), the target line speed of the electric motor 2 is increased, and the transmission torque of the clutch CL2 is increased. Compensate for the decline. This process is the same as the process in step S1 of FIG.

  The prior art starts to engage the first clutch CL1 in this state. (B) shows the transmission torque of the first clutch CL1. As shown by the solid line in the figure, when the internal combustion engine 1 is started, the first clutch CL1 is engaged in two stages. That is, the internal combustion engine 1 is engaged under a first-stage fastening force that allows a certain amount of slip until the complete explosion occurs, and after the internal combustion engine 1 is completely exploded, a complete engagement state is achieved.

  As the first clutch CL1 is engaged to the first stage, the internal combustion engine 1 is cranked by the rotational torque of the electric motor 2 via the first clutch CL1, and is shown by a solid line in (a). Thus, the rotational speed of the internal combustion engine 1 increases. Along with this, the suction negative pressure of the internal combustion engine 1 decreases as shown by the solid line in (c). Note that a decrease in the negative suction pressure means that the absolute value of the negative pressure increases. Further, as shown by the solid line in (f), fuel injection is performed in the internal combustion engine 1. The change in the air-fuel ratio A / F of the air-fuel mixture combusted in the internal combustion engine 1 at this time is shown by a solid line in (g). Since the start is performed under a rich air-fuel ratio, the fuel injection amount at the start is set to be larger than the fuel injection amount after the complete explosion, as shown by the solid line in (f). On the other hand, after the complete explosion, the fuel injection amount decreases and combustion is performed at an air-fuel ratio A / F in the vicinity of the theoretical air-fuel ratio, so the solid line in (g) shows the air-fuel ratio A / F of the air-fuel mixture from start to complete explosion. Shows changes.

  The changes indicated by the solid lines (a)-(c), (f), and (g) in FIG. 4 are designed based on the cranking torque input from the electric motor 2 to the internal combustion engine 1 via the first clutch CL1. This is the case when the street changes. If the first clutch CL1 always transmits the same rotational torque under the same engagement pressure, the internal combustion engine 1 always starts with a constant start pattern by this control.

  Actually, even if the fastening pressure of the first clutch CL1 is constant, the first clutch CL1 is not able to be used due to wear of members constituting the first clutch CL1 or torque transmission status of the second clutch CL2. There may be a delay as shown by the broken line in FIG.

  When a delay as shown by a broken line in (b) occurs in an increase in the transmission torque of the first clutch CL1, a delay also occurs in an increase in the rotational speed of the internal combustion engine 1 as shown by a broken line in (a). As a result, the start of fuel injection is delayed as shown by the broken line in (f). Furthermore, since the time until the internal combustion engine 1 reaches the complete explosion state also becomes longer, the operation period of the internal combustion engine 1 with the rich air-fuel ratio becomes longer as shown by the broken line in (g). Prolonged operation by the rich air-fuel ratio adversely affects the exhaust emission of the internal combustion engine 1.

  4 to 6 show the start pattern of the internal combustion engine 1 under the engine start control device of the hybrid drive electric vehicle according to the present invention.

  Referring to FIG. 4, when a request for starting the internal combustion engine 1 is generated while the vehicle is traveling, the controller 5 first performs the process of step S1 in FIG. That is, as shown in (e), the second clutch CL2 is set to a half-clutch state, and as shown in (d), the target line speed of the electric motor 2 is increased to compensate for the decrease in the transmission torque of the clutch CL2. .

  Next, in step S2, the first clutch CL1 is engaged to the first stage, and cranking of the internal combustion engine 1 is started. The processing so far is the same as that of the prior art of FIG.

  After the internal combustion engine 1 starts cranking, the controller 5 compares the rotational speed of the internal combustion engine 1 detected by the rotational speed sensor 11 with a predetermined target rotational speed in step S3. Here, the predetermined target rotational speed is determined in advance as a value corresponding to the elapsed time from the engagement of the first clutch CL1, that is, the elapsed time from the start of cranking of the internal combustion engine 1, and is stored in the ROM of the controller 5 as a map. Stored in In step S <b> 3, the controller searches the map based on the elapsed time from the execution of step S <b> 2 to obtain the target rotational speed, and compares the obtained target rotational speed with the rotational speed of the internal combustion engine 1.

  If the result of determination in step S3 is that the rotational speed of the internal combustion engine 1 has reached a predetermined target rotational speed, the routine is terminated after confirming that the internal combustion engine 1 has completely exploded in step S8. The starting state in this case is shown by a solid line in the figure. Thus, when the first clutch CL1 transmits the assumed rotational torque, the engine start control according to the present invention brings the same result as the control according to the prior art of FIG.

  The engine start control according to the present invention is different from the control according to the prior art when the transmission torque of the first clutch CL1 varies as shown by the broken line in FIG.

  In this case, the transmission torque of the first clutch CL1 does not increase so much even though the same engagement pressure as the solid line in the drawing is supplied to the first clutch CL1. Therefore, the increase in the rotational speed of the internal combustion engine 1 that is cranked by the transmission torque of the first clutch CL1 should also be slow.

  However, if the controller 5 determines in step S3 in FIG. 2 that the engine rotation speed is equal to or lower than the target rotation speed, in step S4, the controller 5 causes the electric motor 2 to follow the engine rotation speed increase pattern. Calculate the correction value of the rotation speed. On the other hand, in step S5, it is determined whether or not the second clutch CL2 has reached the slip limit.

  FIG. 4 shows a start pattern when the slip ratio of the second clutch CL2 is equal to or less than the slip limit value in step S5, that is, when the second clutch CL2 has not reached the slip limit. In this case, the controller 5 increases the rotation speed of the electric motor 2 based on the correction value as shown in FIG.

  As a result, the shortage of the transmission torque of the first clutch CL1 indicated by the broken line in FIG. 5B is compensated, and the transmission torque indicated by the solid line in FIG. Thus, when the transmission torque of the first clutch CL1 is insufficient and the slip ratio of CL2 is equal to or less than the slip limit value, the internal combustion engine 1 is corrected by correcting the rotational speed of the drive motor 2 to be increased. Can be made to follow a predetermined acceleration pattern.

  5, as in the broken line in FIGS. 3 and 4, the transmission torque of the first clutch CL1 is insufficient, and as a result of the determination in step S5, the slip ratio of the second clutch CL2 is as shown in FIG. The starting pattern in the case where the slip limit value shown in FIG.

  In this case, the controller 5 does not correct the increase in the rotational speed of the electric motor 2 but instead increases the engagement pressure of the first clutch CL1 in step S6. Specifically, as shown in FIG. 5C, the engagement pressure of the first clutch CL1 is increased by increasing the target transmission torque. As a result of this process, the transmission torque of the first clutch CL1 that has been insufficient as shown by the broken line in FIG. 5B is corrected to the state of the solid line in the figure.

  As described above, when the transmission torque of the first clutch CL1 is insufficient and the slip ratio of the second clutch CL2 reaches the slip limit value, the speed increase correction of the rotation speed of the electric motor 2 is performed. First, the rotational speed of the internal combustion engine 1 can be made to follow a predetermined speed increasing pattern by correcting the engagement pressure of the first clutch CL1 to be increased.

  FIG. 6 shows a start pattern when the slip rate of the second clutch CL2 reaches the slip limit value during the start control as a result of the correction of the increase in the rotational speed of the electric motor 2.

  In this case, it is determined in step S3 that the rotational speed of the internal combustion engine 1 is equal to or lower than a predetermined target rotational speed. If it is determined in step S5 that the slip ratio of the second clutch CL2 is equal to or less than the slip limit, the controller 5 corrects the rotational speed of the electric motor 2 in step S6 as in the case of FIG.

  As a result, the transmission torque of the first clutch CL1, which was insufficient as shown by the broken line in FIG. 5B, recovers to the position indicated by the solid line in the drawing, and the rotational speed of the internal combustion engine 1 is also shown in FIG. Thus, it follows the target rising pattern.

  However, as a result of correcting the rotational speed of the electric motor 2 to increase, the slip ratio of the second clutch CL2 increases and eventually reaches the slip limit as shown by the broken line in FIG.

  This will be described with reference to the flowchart of FIG. 2. While the controller 5 repeats the processes of steps S3 to S8, the determination in step S5 turns from positive to negative. As a result, the controller 5 stops the correction of the rotational speed of the electric motor 2 and increases the engagement pressure of the first clutch CL1 in step S7. That is, as shown by the broken line in (c) of the figure, the engagement pressure of the first clutch CL1 is increased by increasing the target transmission torque.

  As a result of this processing, the transmission torque of the first clutch CL1 further increases as shown by the solid line in FIG. 5B, and the rotational speed of the internal combustion engine 1 also increases along a predetermined acceleration pattern, resulting in a complete explosion. .

  As described above, according to the present invention, even if the transmission torque of the first clutch CL1 varies, the rotational speed of the electric motor 2 according to the slip of the second clutch CL2 and the first clutch CL1. By selectively controlling the fastening pressure, the internal combustion engine 1 can always be started under a constant acceleration pattern.

  Therefore, the control relating to the combustion of the internal combustion engine 1 such as the fuel injection amount, the injection timing, and the ignition timing is also performed under a certain pattern. As a result, the internal combustion engine 1 is always started in a stable process without deteriorating exhaust emissions. In addition, since the speed increase pattern of the internal combustion engine 1 at the time of starting is made constant in this way, the combustion control itself of the internal combustion engine 1 becomes easy.

  In the present invention, with the boundary of reaching the slip limit of the second clutch CL2, the rotational speed of the electric motor 2 and the engagement pressure of the first clutch CL1 are controlled to maintain the acceleration pattern at the start of the internal combustion engine 1. These two types of control are selectively applied. Therefore, as compared with the case where the acceleration pattern of the internal combustion engine 1 is maintained with only one of them, the acceleration pattern at the start of the internal combustion engine 1 can be maintained with respect to a wider range of operating condition changes.

  As described above, the present invention has been described through specific embodiments. However, the present invention is not limited to the above embodiments. Those skilled in the art can make various modifications or changes to these embodiments within the scope of the claims.

It is a schematic block diagram of the drive system of the hybrid drive electric vehicle to which this invention is applied. It is a flowchart explaining the engine starting routine which the controller by this invention performs. It is a timing chart which shows the starting pattern of the internal combustion engine at the time of applying the conventional internal combustion engine start control. 3 is a timing chart showing a start pattern of an internal combustion engine under the correction of acceleration of the electric motor according to the present invention. 3 is a timing chart showing a start pattern of an internal combustion engine under a correction for increasing the engagement pressure of the first clutch according to the present invention. 3 is a timing chart showing a start pattern of the internal combustion engine under the correction for increasing the speed of the electric motor and the correction for increasing the engagement pressure of the first clutch according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Electric motor 3 Automatic transmission 5 Controllers 11 and 13 Rotational speed sensor 12 Inverter CL1 1st clutch CL2 2nd clutch

Claims (7)

The present invention is applied to a hybrid drive electric vehicle in which an internal combustion engine and an electric motor are connected via a first clutch, and the electric motor and drive wheels are connected via a second clutch, and the electric motor rotates while the vehicle is running. In an engine start control method of a hybrid drive electric vehicle for starting an internal combustion engine with torque,
(A) Put the second clutch in the half-clutch state,
(A) The first clutch is engaged at a predetermined pressure,
(C) comparing the engine speed after engaging the first clutch with a preset target speed;
(D) Determine whether the second clutch has reached the slip limit;
(E) When the engine rotational speed is equal to or lower than the target rotational speed and the second clutch has not reached the slip limit, the rotational speed of the electric motor is increased,
(F) Increasing the engagement pressure of the first clutch when the engine rotational speed during startup is equal to or lower than the target rotational speed and the second clutch has reached the slip limit;
An engine start control method for a hybrid drive electric vehicle. 2. The engine start control of the hybrid drive electric vehicle according to claim 1, wherein the target rotation speed is a value set in advance in accordance with an elapsed time from the engagement of the first clutch in (a). Method. 3. The engine start control method for a hybrid drive electric vehicle according to claim 1, wherein the second clutch is connected to drive wheels via an automatic transmission. 4. In the determination of (d), when the ratio between the rotational speed of the electric motor and the input rotational speed of the automatic transmission exceeds a predetermined slip limit value, it is determined that the second clutch has reached the slip limit. The engine start control method for a hybrid drive electric vehicle according to any one of claims 1 to 3. As a result of increasing the rotation speed of the electric motor, when the second clutch reaches the slip limit, further increase of the rotation speed of the electric motor is stopped and the engagement pressure of the first clutch is increased. The engine start control method of a hybrid drive electric vehicle according to any one of claims 1 to 4, wherein the engine start control method is performed. The process from (c) to (f) is repeatedly executed until the rotational speed of the engine reaches a predetermined complete explosion determination speed, according to any one of claims 1 to 5, The engine start control method of the hybrid drive electric vehicle of description. The present invention is applied to a hybrid drive electric vehicle in which an internal combustion engine and an electric motor are connected via a first clutch, and the electric motor and drive wheels are connected via a second clutch, and the electric motor rotates while the vehicle is running. In an engine start control device for a hybrid drive electric vehicle that starts an internal combustion engine with torque,
Means for bringing the second clutch into a half-clutch state;
Means for fastening the first clutch at a predetermined pressure;
Means for comparing the engine speed after engaging the first clutch with a preset target speed;
Means for determining whether the second clutch has reached a slip limit;
Means for increasing the rotational speed of the electric motor when the engine rotational speed is below the target rotational speed and the second clutch has not reached the slip limit;
Means for increasing the engagement pressure of the first clutch when the engine rotation speed is equal to or lower than the target rotation speed and the second clutch has reached the slip limit;
An engine start control device for a hybrid drive electric vehicle, comprising:

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