JP2009208746A - Vibration control device for engine in hybrid car - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the vibration of an engine when the engine starts and stops in a hybrid car. <P>SOLUTION: When the engine stops, the torque command value of the engine is calculated based on a crank angle, crank angular acceleration, and target stop crank angle, to control an engine (S1 to S5), and the torque command value of a motor is calculated based on the torque command value and estimated torque of the engine, to control the motor. Thus, engine roll vibration is reduced when the engine stops by canceling engine torque fluctuation by motor torque, and to reduce engine roll vibration when the engine starts by stopping the engine at the target stop crank angle. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for suppressing engine vibration at the time of start and stop in a hybrid vehicle having an engine (internal combustion engine) and a motor (electric motor) as prime movers.

In Patent Document 1, in a hybrid vehicle, when the engine is stopped, a variation pattern of a motor torque command is set based on a crank angle when the engine rotation speed reaches a predetermined value, and the hybrid vehicle is stopped at a target stop position. Such a technique is disclosed. For example, a standard pattern is set when the crank angle is within a predetermined range, a pattern for suppressing engine rotation is set when the crank angle is larger than the predetermined range, and a pattern for promoting engine rotation is set when the crank angle is smaller than the predetermined range. Control motor torque.
JP 2005-42560 A

  However, in Patent Document 1, since it is open control that determines the subsequent torque pattern based on the crank angle when the predetermined engine rotation speed is reached, it is difficult to stop at an accurate target stop position. .

  In addition, there is a problem in that it cannot cope with changes in engine friction due to engine water temperature or the like, and further, deterioration of vibration due to passing through the resonance point of the engine mount cannot be reduced when the engine is stopped.

  The present invention has been made by paying attention to such a conventional problem, and by suppressing the vibration at the time of stopping the engine well, by accurately stopping at the target crank angle, the vibration at the time of starting is also suppressed well. The purpose is to be able to.

For this reason, the present invention
Set the target stop crank angle when the engine stops,
Detect or estimate engine crank angle, crank angular speed, crank angular acceleration,
Based on the crank angle, crank angular speed, crank angular acceleration, and target stop crank angle, engine torque command value is calculated to control the engine,
Estimate the engine torque,
The motor is controlled by calculating the torque command value of the motor based on the torque command value of the engine and the estimated torque.

  When the engine is stopped, engine control and torque control corresponding to the engine control are performed based on the detected or estimated engine crank angle, crank angular speed, crank angular acceleration, and target stop crank angle. The vibration at the time of starting can also be suppressed satisfactorily by accurately stopping at the target stop crank angle while suppressing the vibration at the same time.

FIG. 1 shows an example of a power train for a hybrid vehicle to which the present invention is applied.
An output shaft of an engine (for example, a diesel engine) 1 is connected to a motor 2, and an output shaft of the motor 2 is connected to an automatic transmission 3 with a torque converter.

The engine 1 is supported on the vehicle body via the mount 4.
The controller 5 receives signals from various sensors and controls the engine 1 and the motor 2 based on the signals. A crank angle sensor 6 for detecting the crank angle of the engine 1 is used as a signal related to the present invention. Only the input of the crank angle signal from is shown.

  In the above system configuration, when the engine is started / stopped, the engine rotational speed Ne passes through the engine mount resonance frequency, so that the engine roll vibration is deteriorated, which is transmitted to the vehicle body via the mount 4, and the vehicle body vibration is deteriorated. .

When the engine is started, as shown in FIG. 2, the vibration level changes depending on the initial crank angle (crank angle when stopped), and an optimum initial crank angle exists.
In particular, in the case of a diesel engine, as indicated by a dotted line in FIG. 3, torque fluctuation is large and vibration deterioration is large because of a high compression ratio and no throttle. Especially when the vehicle is stopped, it is much worse because it is throttle-less.

In a gasoline engine, a decompression mechanism that retards the intake valve closing timing is used to reduce vibration. However, a diesel engine is difficult to adopt due to responsiveness and HC deterioration.
Therefore, when the engine is stopped, it is necessary to simultaneously perform stop position control for stopping the motor 2 at an optimal crank angle and vibration suppression control for canceling engine torque fluctuation with motor torque.

Hereinafter, control when the engine is stopped in the first embodiment will be described with reference to the flow of FIG.
When there is an engine stop command, as shown in FIG. 5, the target top crank angle θt is set to 0 as the top dead center next to the crank angle at the time of engine stop command, and after a predetermined angle (1010 ° for a 6-cylinder engine). The angle is determined (S1 to S3).

  When the target stop crank angle θt is controlled to stop at the crank angle θt, the target stop crank angle θt is set as a crank angle that can suppress vibration even when the crank angle at the time of the stop is started as the initial crank angle.

From the crank angle θ detected by the crank angle sensor 7, the crank angular velocity and crank angular acceleration are estimated by an observer (S4, see FIG. 6).

  A torque command value Tp to the engine 1 relating to stop position control is obtained by multiplying the integral value of the crank angular velocity, crank angle θ−target stop crank angle θt, and crank angle θ−target stop crank angle θt estimated by the observer with a gain. Calculate and output. The gain is determined based on the LQ control theory as described later (S5).

Based on the crank angular acceleration and the motor torque Tm one step before, the actual torque Te of the engine 1 is estimated by the following equation (S6).

The difference (= Tp−Te) between the torque command value Tp for the engine 1 and the estimated actual torque Te is output as the torque command value Tm for the motor 2 (S7).
When the engine rotation speed Ne decreases and becomes equal to or less than a predetermined rotation speed (for example, 50 rpm), a predetermined range in which the crank angle θ _t1 at that time is sandwiched between two angles set before and after the target stop crank angle θt Among these, for example, if it is in the range from the top dead center before the target stop crank angle to the top dead center after, the above control is performed without changing the target stop crank angle.

Meanwhile, the predetermined crank angle at the rotational speed or less and since the time t1 theta _t1 is, when is out of the predetermined range, changes the target stop crank angle as follows (S8 to S10).

  For example, when the initial target stop crank angle is set to 1010 ° in a 6-cylinder engine, the relative angle from the top dead center before that is 50 °, and the relative angle from the top dead center after that is 120 °. It is −50 ° (= 70 °). Here, with respect to an arbitrary top dead center, a crank angle whose relative angle to the top dead center is the same as the target stop crank angle is represented by 120n + 50, and the top dead centers before and after the crank angle are 120n, 120 (n + 1). It is.

Therefore, the target stop crank angle θt is changed to (120 m + 50) with respect to top dead centers 120 m and 120 (m + 1) before and after sandwiching the crank angle θ _t1 .
Specifically, when the crank angle θ _t1 is in the range of 840 ° to 960 °, the crank angle θ _t1 is changed to 1010 ° −120 ° = 890 °, and when the crank angle θ _t1 is in the range of 960 ° to 1080 °. If it is in the range of 1080 ° to 1200 ° without being changed, it is changed to 1010 ° + 120 ° = 1130 °.

  Then, the difference between the detected crank angle and the target stop crank angle becomes a predetermined value (for example, 1 °) or less, and when this state elapses for a predetermined time (for example, 10 seconds), the control is stopped (S11, S12). .

  In this way, fluctuations in the engine torque at the time of stopping can be accurately approximated to the target stop crank angle θt while canceling out the vibration at the time of stopping by offsetting the torque Tm (= Tp−Te) of the motor 2, The vibration when starting next time can also be reduced.

FIG. 3 shows the vibration reduction effect at the time of start and stop as compared with the case where this control is not performed.
Next, formation of a state space model leading to gain calculation in the feedback control of the present embodiment will be described.

As a system model, the equation of motion of the crankshaft + motor rotation system is shown as follows.

If the output is θ and this is expressed in the state space,

When an integral term is added to (2) and (3) and the output is changed,

For this state space model, a gain is set based on the LQ control theory of the modern control theory.
Next, a second embodiment will be described.

In this embodiment, in addition to detecting the crank angle, the roll acceleration of the engine body (rotational angular acceleration around the crankshaft of the engine body) is detected and used for control.
For this reason, as shown in FIG. 7, the lateral acceleration sensors 7 and 8 are attached to the upper end and the lower end of the engine 1, respectively, and the difference between the detected lateral accelerations is divided by the distance between the sensors 7 and 8. Thus, roll acceleration is detected.

Using the roll acceleration detected in this way, an observer is configured as follows.
In the present embodiment, the system model can be expressed as the following equation as an equation of motion of the engine body + crankshaft + motor rotation system.

Rewrite equations (7) and (8)

For the discretization of this, if you construct an observer based on modern control theory,

(12)

When rewriting and adding the estimation of acceleration and integral,

A torque command value of the motor 2 is obtained from this estimated value and gain.

  As in the second embodiment, by detecting and using the roll acceleration of the engine body, the estimation accuracy of the crank angular velocity and crank angular acceleration by the observer is improved, and even when the detection signal includes noise. These values can be estimated with high accuracy.

1 is a diagram showing a system configuration of a hybrid vehicle according to an embodiment of the present invention. The figure which shows the relationship between the crank angle at the time of a start, and an engine roll vibration. The figure which shows the vibration reduction effect at the time of a start and a stop compared with the case where the control which concerns on this invention is not performed. The flowchart of the control concerning the present invention same as the above. The figure which shows the setting method of a target stop crank angle. The control block diagram of 1st Embodiment. The figure which shows the installation location of the sensor used for 2nd Embodiment. The control block diagram of 2nd Embodiment.

Explanation of symbols

1 Engine 2 Motor 3 Automatic transmission 4 Mount 5 Controller 7 Crank angle sensor

Claims (8)

In an engine vibration control device in a hybrid vehicle using an engine and a motor as a prime mover,
Set the target stop crank angle when the engine stops,
Detect or estimate engine crank angle, crank angular speed, crank angular acceleration,
Based on the crank angle, crank angular speed, crank angular acceleration, and target stop crank angle, a torque command value to the engine is calculated to control the engine,
Estimate the actual torque of the engine,
An engine vibration control apparatus for a hybrid vehicle, which controls a motor by calculating a torque command value for a motor based on a torque command value for the engine and an estimated actual torque.   2. The engine vibration control apparatus for a hybrid vehicle according to claim 1, wherein the calculation of the torque command value of the engine includes an integral part of a deviation between a target stop crank angle and a crank angle.   3. The engine vibration control apparatus according to claim 1, wherein the crank angle is detected, and a crank angular velocity and a crank angular acceleration are estimated based on a detected value of the crank angle. 4.   The crank angular velocity and the crank angular acceleration are estimated based on detected values of the crank angle and the rotational angular acceleration around the crankshaft of the engine body, and the detected values of the crank angle and the rotational angular acceleration. The vibration control device for an engine in the hybrid vehicle according to any one of claims 1 to 3.   The actual torque of the engine is estimated based on a crank angular acceleration and a motor torque command value calculated one time before. Engine vibration control device for hybrid vehicles.   6. The target stop crank angle is set to a first predetermined angle ahead of a top dead center that comes after the time when an engine stop command is received. The vibration control device for the engine in the hybrid vehicle described in 1.   The second and third predetermined angles are set before and after the target stop crank angle, and when the engine speed becomes a predetermined value or less, the crank angle is set between the second predetermined angle and the third predetermined angle. Otherwise, the target crank angle is the same relative to the top dead center, and the current crank angle is included between the second predetermined angle and the third predetermined angle. The engine vibration control device for a hybrid vehicle according to claim 6, wherein the vibration control device is set to an angle.   The second predetermined angle is an angle that becomes a top dead center immediately before the current crank angle, and the third predetermined angle is an angle that becomes a top dead center immediately after the current crank angle. Item 8. A vibration control device for an engine in a hybrid vehicle according to Item 7.

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