KR100828818B1 - Engine stop position control method of hybrid electric vehicle - Google Patents

Abstract

A method for controlling an engine stop position of a hybrid electric vehicle is provided to minimize torque pulsation generated in the compression/expansion process of introduced air during initial engine restarting and engine restarting while driving a vehicle. A method for controlling an engine stop position of a hybrid electric vehicle comprises a step of reducing an engine speed under the control of a controller through a motor according to a first engine speed reduction rate in a state in which fuel supplied to an engine is cutoff when the engine stops. After reducing the engine speed up to a first preset speed, the engine speed is reduced according to a second engine speed reduction rate through the motor, and simultaneously the number of times by which the present crank position mates with a preset target engine stop position is counted by processing signals of a crank sensor and a cam sensor. If the counted number of times is greater than a preset number of times and the engine speed is reduced below a second preset speed, the engine is stopped through the motor.

Description

Engine Stop Position Control Method of Hybrid Electric Vehicle

1 is a schematic view showing a drive unit of a hybrid electric vehicle,

2 is a view showing a change in starting torque according to the engine stop position;

3 is a flow chart showing an engine stop position control method according to the present invention;

Figure 4 is a schematic diagram showing a state in which the engine speed is controlled in the control process according to the present invention,

5 is a view showing the signals of the crank sensor and the cam sensor in the VVT engine,

Figure 6 is a test result when applying the engine stop position control method according to the present invention.

<Explanation of symbols for main parts of the drawings>

1: engine 2: clutch

3: electric motor 4: transmission

5: ISG

The present invention relates to a method for controlling an engine stop position of a hybrid electric vehicle, and more particularly, in a hybrid electric vehicle having a motor capable of starting an engine, in the compression / expansion process of intake air during initial engine start and engine restart during driving. A method for controlling the position of the crankshaft at engine stop in order to minimize the generated torque pulsation and to suppress the vibration generated at the start of the engine from the maximum.

In general, a hybrid vehicle in a broad sense means driving a vehicle by efficiently combining two or more different power sources, but in most cases, a driving force is obtained by an electric motor driven by a fuel-powered engine and a battery. A vehicle, which is called a hybrid electric vehicle, that is, a hybrid electric vehicle (HEV).

In response to the recent demand for improving fuel economy and developing more environmentally friendly products, research on hybrid electric vehicles is being actively conducted.

Hybrid electric vehicles can form a variety of structures using engines and electric motors as power sources. Most of the vehicles studied so far employ either parallel or series.

The hybrid electric vehicle is basically equipped with a vehicle control unit (HCU), which is responsible for overall vehicle control, and has a controller for each device constituting the system.

For example, an engine control unit (ECU) for controlling the overall operation of the engine, a motor control unit (MCU) for controlling the overall operation of the electric motor, a transmission control unit (TCU) for controlling the transmission The battery management system (Battery Management System, BMS) for controlling the operation of the battery, the air conditioning controller (Full Auto Temperature Controller, FATC) in charge of the room temperature control is provided.

These controllers are connected to a high-speed CAN communication line (eg 500kbps) around the HCU, and the upper controller transmits commands to the lower controller while exchanging information between the controllers.

As described above, in the hybrid electric vehicle, a plurality of controllers perform cooperative control with each other using the HCU as the upper controller.

The HCU exchanges information with each controller through CAN communication and also controls subordinate controllers. The ECU has an engine torque and engine speed information, start key information, throttle / engine temperature (cooling water temperature) from the ECU. Information), and the HCU is also configured to transmit fuel injection command, engine stop command, fuel injection prohibition command, electric motor start information, idle stop information, etc. to the ECU.

In addition, the HCU substantially controls the driving of the electric motor through the MCU. At this time, the MCU maintains the driveability by controlling the driving torque and the driving speed of the electric motor as the driving source according to the control signal applied from the HCU, which is the upper controller.

As described above, cooperative control between controllers is very important in a hybrid electric vehicle, and cooperative control between controllers is performed in all cases from startup to when the user turns off the ignition key.

On the other hand, Figure 1 is a schematic diagram showing a drive unit of the hybrid electric vehicle, the electric motor 3 is connected to the engine 1 via the clutch 2, the output end of the electric motor 3 is a transmission ( It is connected to 4) to output the driving force through the transmission (4).

Reference numeral 5 denotes an integrated starter generator (ISG) having a function of a starter motor for starting an engine and a function of a generator for charging a battery.

The ISG 5 is connected to the engine by a belt and rotates at the same time as the engine. The rotation speed is determined according to the pulley ratio from the engine speed. It is to perform a function of generating a high power for charging the battery with the rotational force, the function of stopping the engine in the state that the fuel of the engine is cut off (fuel injection blocking) when the engine off.

In such a hybrid electric vehicle having a motor capable of starting the engine, that is, the ISG 5, the engine stop request signal is output while the HCU cuts fuel supplied to the engine when the engine is stopped. The ISG MCU then controls the ISG, the starter motor, to finally stop the engine.

However, since the position of the piston and the crankshaft (engine stop position) changes every time the engine stops, if the ISG provides a constant starting torque to the engine for subsequent engine start, the torque pulsation and Vibration will occur.

That is, the deviation of the torque pulsation occurs in the compression / expansion process of the intake air at the initial engine start or when the engine is restarted while driving due to the difference of the engine stop position, thereby causing vibration at the engine start.

Therefore, in order to suppress the generation of vibration of the engine, it is necessary to constantly control the stop position (position of the piston and the crankshaft) at the time of engine stop.

Torque pulsations occurring at the start of the engine consist of a friction force generated between the piston and the cylinder wall and a pumping force generated by the movement of the piston.

The frictional force varies depending on the surface friction coefficient and the lubricating oil temperature, but the difference is small in a low rotational region such as engine starting, while the pumping force is largely changed as shown in FIG. 2 according to the initial piston starting position.

This change not only generates engine vibration but also impairs operability due to shock and can adversely affect the durability of the engine mounting.

As a result, there is an urgent need for a method of minimizing torque pulsation and vibration generated when the engine is started by constantly controlling the engine stop position in the hybrid electric vehicle.

Accordingly, the present invention has been invented to solve the above problems, and in a hybrid electric vehicle having a motor capable of starting the engine, torque generated during compression / expansion of intake air during initial engine start and engine restart during driving. It is an object of the present invention to provide a method of controlling the position of the crankshaft at the time of engine stop in order to minimize the pulsation and to suppress the vibration generated at the start of the engine.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

In order to achieve the above object, the present invention, in the engine stop position control method of a hybrid electric vehicle having a motor capable of controlling the engine speed,

(a) decelerating and controlling the engine speed according to the engine speed reduction rate 1 through the motor in a state in which the fuel supplied to the engine is shut off by the controller;

(b) After the engine speed is reduced to the set speed 1, the engine speed reduction rate is adjusted low to control the engine speed according to the engine speed reduction rate 2 through the motor, and process the signals of the crank sensor and cam sensor to process the crank position. Counting the number of times that the current crank position matches a preset target engine stop position by monitoring a;

(c) stopping the engine through the motor at the time when the crank position matches the target engine stop position, when the engine speed is reduced to the set speed 2 or less while the number of matches exceeds a preset number;

It provides an engine stop position control method for a hybrid electric vehicle comprising a.

Here, in step (b), the missing tooth of the crank sensor is detected from the signals of the crank sensor and the cam sensor, and after the missing tooth is detected, the pulse falling edge of the crank sensor signal is counted from the missing tooth, and the counted pulse falling is performed. When the number of edges is set as the number of falling edges set as the target engine stop position, it is determined that the current crank position matches the target engine stop position.

In addition, in the process of detecting the missing tooth, the pulse falling edge of the crank sensor signal is counted from the time when the falling edge of the cam sensor signal is input, and when the counted number of falling edges is a preset number, the detection is performed as a missing tooth. Characterized in that.

Also preferably, in the engine speed deceleration control process of step (b), in order to obtain a target engine speed according to the engine speed reduction rate 2, the controller may calculate a speed gain value according to the current coolant temperature obtained from the input map data. PID control of the engine speed by using.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an engine stop position of a hybrid electric vehicle, the torque being generated during compression / expansion of intake air during initial engine start and engine restart while driving in a hybrid electric vehicle having a motor capable of starting the engine. A method for controlling the position of the crankshaft at engine standstill in order to minimize pulsation and to suppress as much as possible vibration from the engine starting therefrom.

Conventionally, the position of the piston and the crankshaft (engine stop position) changes every time the engine stops, and the torque pulsation and vibration of the engine occur when the ISG provides a constant starting torque to the engine for subsequent engine start due to such stop position deviation. There was a problem.

Therefore, in order to suppress the occurrence of torque pulsation and vibration of the engine as much as possible, it is necessary to control the stop position of the crankshaft, that is, the engine stop position at all times, every time the engine stops. If the condition is satisfied by monitoring the Crankshaft, the main point is to control the stop position of the crankshaft constantly by stopping the engine momentarily with the starter motor (ISG) when the crankshaft position reaches the set target stop position. will be.

3 is a flowchart illustrating an engine stop position control method according to the present invention, which shows a control process performed by the engine stop position control module of the controller according to the present invention. Here, the control unit may be a vehicle controller, that is, an HCU of the hybrid electric vehicle.

First, when the engine is stopped, the HCU stops the fuel supplied to the engine (fuel injection command output, fuel injection cutoff), and the stop position control module of the HCU is driven by the engine off flag input. When the vehicle enters the off state, the stop position control module controls the starting motor (ISG) through the MCU (motor controller) to decelerate and control the engine speed (engine rotational speed, rpm) according to a preset engine speed reduction rate 1. .

Then, when the current actual engine speed (or estimated engine speed calculated from the speed of the starting motor connected to the engine) matches the set speed 1, that is, when the engine speed decreases to the set speed 1 through deceleration control, the stop position The control module processes the signals of the crank sensor and the cam sensor to monitor the position of the crankshaft (hereinafter referred to as crank position).

Here, the engine speed reduction rate by the starting motor is adjusted to the engine speed reduction rate 2 which is set relatively low. While the engine speed is controlled by the starting motor according to the adjusted engine speed reduction rate 2, while the deceleration control is performed. The crank position is monitored to count the number of times the current crank position matches the preset target engine stop position.

After that, the stop position control module has a preset number of times corresponding to the target engine stop position more than a preset number, and the current actual engine speed (or estimated engine speed calculated from the speed of the starting motor) according to the deceleration control is less than or equal to the set speed 2. When the current crank position is equal to the target engine stop position, the engine stop request signal is output to the MCU.

As a result, the MCU controls the starting motor to momentarily stop the engine, which causes the engine to stop at the target stop position (engine speed = 0).

Here, the set speed 2 is determined as an engine speed at which the starting motor (ISG) can overcome the torque pulsation and regulate the engine at a constant rotational speed, which is determined as the minimum engine speed capable of processing the crank signal in the HCU. .

As described above, in the present invention, the crank position is controlled to be the target engine stop position through the starting motor when the engine is turned off, and the target engine is always stopped at the crank position (engine stop position) by performing the above control process every time the engine is turned off. Will remain constant in position.

4 is a schematic view showing a state in which the engine speed is controlled in the control process according to the present invention.

In FIG. 4, 'Eng_rpm' represents the actual engine speed, 'Est_Eng_rpm' represents the engine speed calculated from the speed of the starting motor, 'Cntl_St_rpm' represents the set speed 1, and 'Eng_stp_rpm_min' represents the set speed 2.

Meanwhile, a process of counting the number of times that the current crank position is equal to the target engine stop position by monitoring the crank position during the deceleration control of the engine speed will be described in detail with reference to FIGS. 5 and 6.

In the present invention, the HCU monitors the crank position, that is, the position of the crankshaft by using the signals of the crank sensor and the cam sensor of the engine, and starts when the crank position becomes a predetermined target stop position when the predetermined condition is satisfied as described above. The motor is used to stop the engine.

FIG. 5 is a diagram illustrating signals of a crank sensor and a cam sensor in a VVT (Variable Valve Timing) engine.

In general, 58 teeth are formed on the sensor wheel of a crank sensor (crank position sensor, ckp sensor), and two teeth (hereinafter, referred to as missing teeth) are removed. Since the sensor wheel rotates two times (720 °) during one engine cycle, a total of 118 pulse signals are output from the crank sensor except for two missing tooth portions as shown in FIG.

In an engine to which a half moon type cam is applied, the signal of the cam sensor is in the form of a signal having a falling edge and a rising edging once per cycle as shown in FIG. 5. It is.

In general, an ECU (engine controller) finds a missing tooth from a signal of a crank sensor and uses a signal change of a cam sensor to find an engine No. 1 cylinder.

If the existing complicated process applied to the ECU is applied to the HCU for the engine stop position control of the present invention as it is, the execution time becomes excessive.

Therefore, in the present invention, a new method is applied in which the HCU can easily and quickly obtain the engine position information necessary for stopping the engine from the signals of the crank sensor and the cam sensor in controlling the engine stop position.

Looking at the cam behavior of the VVT engine, when the engine is stopped, the cam is in the maximum retard position, and the cam position is advanced and moved as the engine is started and the engine load increases.

When the engine generates torque under a specific load condition and the vehicle driving mode is switched to the motor driving mode (EV mode), the fuel supplied to the engine is first interrupted by the HCU, and the engine is stopped by the starting motor. Will be.

The cam position of the VVT engine is always at the maximum perceptual position as shown in FIG. 5 in a state where fuel injection is interrupted at the engine stop (before the constant pulse number (pulse falling edge number) of the crank sensor signal). The falling edge of the cam sensor signal is located).

Thus, when the fuel is cut off when the engine is turned off and no more torque is generated in the engine, the HCU can easily detect the missing tooth and stop the engine by using the cam position always positioned at the maximum perceptual position shown in FIG. 5. It can be used as a synchronization signal for position control.

First, in the present invention, the HCU (stop position control module) detects a missing tooth from the signals of the crank sensor and the cam sensor as shown in FIG. 5, where the HCU inputs the falling edge of the cam sensor signal and then drops the pulse of the crank sensor signal. When the number of falling edges is counted and the number of falling edges reaches the set number 1, the position is determined as a missing tooth position.

This means that as described above, when the fuel to the engine is cut off and no further torque is generated in the engine, the cam is always in the maximum perceptual position, with the falling edge of the cam sensor signal falling from the missing tooth position to a constant drop in the crank sensor signal. It is always used before the number of edges.When the number of falling edges of the crank sensor signal reaches the set number 1 from the falling edge of the cam sensor signal, the HCU detects the sewing machine position and generates a synchronization signal. The number of falling edges of the signal is counted again.

The set number 1 is a preset value that is preset and input. The set number 1 may vary for each engine, and the position where the number of falling edges of the crank sensor signal becomes the set number 1 from the input point of the falling edge of the cam sensor signal is always the missing tooth position. do.

In the example of FIG. 5, when four falling edges of the crank sensor signal are input after the falling edge of the cam sensor signal, the missing tooth is detected, and the set number 1 is four.

That is, if four falling edges of the crank sensor signal are input after the falling edge of the cam sensor is input, it is determined as a missing tooth.

Next, after the missing tooth is detected as described above, the falling edge of the crank sensor signal is counted again from the detected missing tooth, and when the counted number of falling edges reaches the set number 2, the current crank position matches the target engine stop position. Will be judged.

Here, the set number 2 is a set value for defining the target engine stop position in the control process of the present invention. For example, if the set number 2 is set to 10, the position at which 10 falling edges of the crank sensor signal are input after the missing tooth is detected. Means the target engine stop position, and the engine is to be stopped at the crank position where 10 falling edges are input.

In addition, when 10 falling edges are actually counted from the signal of the crank sensor, it means that the current crank position has reached the target engine stop position. Therefore, after the detection of the missing tooth in the control process of the present invention, the falling edge of the crank sensor signal is counted. When the number is 10, it is determined that the current crank position matches the target engine stop position, and the number of times the current crank position matches the target engine stop position is counted.

Then, while the engine speed is controlled from the set speed 1 as described above, the number of counts becomes equal to or more than the preset number as described above, and the engine speed (the estimated engine speed calculated from the actual engine speed or the speed of the starting motor) becomes the set speed 2. After decelerating to, i.e., if the engine speed is lower than or equal to the set speed 2, the HCU will turn on the MCU at the point when the crank position equals the target engine stop position (the falling edge of the crank sensor signal after the missed tooth detection becomes the set number 2). The engine is stopped by controlling the motor for starting.

In a preferred embodiment, in the process of the HCU control unit of the present invention to control the engine speed from the set speed 1 to the set speed 2 according to the engine speed reduction rate 2 using the starting motor, the HCU is set from the set speed 1 to the set speed 2 PID control is performed to obtain a target engine speed according to the engine speed reduction rate 2 in the interval of, that is, to obtain an engine speed following the speed diagram from the set speed 1 (Cntl_St_rpm) to the set speed 2 (Eng_stop_rpm_min) shown in FIG. In this case, map data obtained by mapping a speed gain value according to the coolant temperature may be used. That is, the HCU obtains a speed gain value according to the current engine coolant temperature detected and input by the water temperature sensor from the previously input map data, and uses the same to control the engine speed according to the engine speed reduction rate 2.

Since the engine friction is dependent on the engine temperature, that is, the coolant temperature, the HCU controls the engine speed PID from the set speed 1 to the set speed 2 according to the engine speed reduction rate 2, so that the speed gain value according to the coolant temperature is determined. If the engine speed is controlled in consideration, it is possible to improve the vehicle ride comfort during the deceleration control and also improve the accuracy of the final engine stop position.

Thus, according to the engine stop position control method of the present invention, it is possible to stop the engine constantly at a predetermined position every time the engine stops, and the conventional torque generated while the starting motor provides a constant starting torque at engine start-up. It is possible to suppress pulsation and engine vibration as much as possible.

In the above description, the motor for stopping the engine has been described as a starting motor, but in a broad sense, the motor should be understood as a motor that can control the engine speed, and has an ISG, an engine starting motor, and a power generation function for charging the battery. The generator can be used as a motor for starting the engine.

6 is an experimental result diagram when the engine stop position control method according to the present invention is applied, in which a blue line represents a tooth number (Y-axis indication) of a crank sensor, and a tooth number 0 represents a missing tooth. It can be seen that the cumulative counted number of teeth during the 1 cycle and 2 revolutions from the tooth becomes 118, and then the sewing machine teeth becomes 0 again.

The green line indicates the set target engine stop position.

In the example of Fig. 6, the number of teeth is set to 118, and the set number 2 indicating the target engine stop position is set to 10 (the crank position input of 10 falling edges after the missing tooth detection is set as the target engine stop position).

Accordingly, after detecting the missing tooth of the tooth number 0 from the crank sensor signal, the number of falling edge 10 input positions coincides with the target engine stop position, that is, the current crank position (blue line) and the target engine stop position (green line). When the number of matches is 8, the engine is stopped at the next target engine stop position (10 falling edge input positions).

As described above, according to the engine stop position control method according to the present invention, the crank sensor and the cam sensor by monitoring the crank position by processing the signal of the crank sensor and the cam sensor in the state that the HCU cut off the fuel supplied to the engine when the engine stops, If the predetermined condition is satisfied, the engine is momentarily stopped by the starting motor at the time when the crank position reaches the predetermined target stop position, so that the engine can be stopped constantly at the specified stop position at every engine stop. At the same time, it is possible to suppress the occurrence of torque pulsation and engine vibration as much as possible due to the stop position deviation.

Claims (4)

In the engine stop position control method of a hybrid electric vehicle having a motor capable of controlling the engine speed, (a) decelerating and controlling the engine speed according to the engine speed reduction rate 1 through the motor in a state in which the fuel supplied to the engine is shut off by the controller; (b) After the engine speed is reduced to the set speed 1, the engine speed reduction rate is adjusted low to control the engine speed according to the engine speed reduction rate 2 through the motor, and process the signals of the crank sensor and cam sensor to process the crank position. Counting the number of times that the current crank position matches a preset target engine stop position by monitoring a; (c) stopping the engine through the motor at the time when the crank position matches the target engine stop position, when the engine speed is reduced to the set speed 2 or less while the number of matches exceeds a preset number; Engine stop position control method for a hybrid electric vehicle comprising a. The method according to claim 1, In step (b), a missing tooth of the crank sensor is detected from the signals of the crank sensor and the cam sensor, and after the missing tooth is detected, the pulse falling edge of the crank sensor signal is counted from the missing tooth, and the counted number of pulse falling edges is counted. The engine stop position control method for a hybrid electric vehicle according to claim 1, wherein when the set number of falling edges is set to the target engine stop position, the current crank position is determined to match the target engine stop position. The method according to claim 2, In the process of detecting the missing tooth, the pulse falling edge of the crank sensor signal is counted from a time point at which the falling edge of the cam sensor signal is input, and when the counted number of falling edges is a preset number, it is detected as a missing tooth. Engine stop position control method for a hybrid electric vehicle, characterized in that. The method according to claim 1, In the engine speed deceleration control process of step (b), in order to obtain a target engine speed according to the engine speed reduction rate 2, the controller calculates the engine speed by using the speed gain value according to the current coolant temperature obtained from the input map data. Engine stop position control method for a hybrid electric vehicle, characterized in that the PID control.

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