KR20060020000A - Vacuum pressure control method of hybrid vehicle - Google Patents

Abstract

The present invention relates to a negative pressure control method of a hybrid vehicle capable of securing a stable braking force by maintaining a constant negative pressure of the vehicle by using a motor of the hybrid vehicle, wherein the motor of the hybrid vehicle assists the engine force when the vehicle accelerates, Apart from the inherent function of the hybrid motor that recovers the power of the vehicle when decelerating, the brake underpressure of the vehicle is prevented from falling below the target underpressure, and the brake underpressure is kept below a certain value to maintain a constant underpressure of the vehicle to ensure stable braking force. At the time of falling, the motor assist torque value is calculated and the motor control is started to compensate for the negative pressure reduction caused by the vehicle load.

Hybrid, vehicle, negative pressure, control

Description

Negative pressure control method of hybrid vehicle {VACUUM PRESSURE CONTROL METHOD OF HYBRID VEHICLE}

1 is a view illustrating an operation principle of a booster applied to a hybrid vehicle according to the prior art.

2 is a view showing a basic configuration of a hybrid vehicle equipped with a continuously variable transmission (CVT).

3 shows the relationship between brake underpressure and motor assist time.

4 is a signal flow diagram illustrating negative pressure improvement logic of a hybrid vehicle according to an embodiment of the present invention.

The present invention relates to a negative pressure control method of a hybrid vehicle.

Typically, a hybrid vehicle includes an engine for generating power of a vehicle, a motor for assisting the power of the engine, and a transmission for transmitting power of the engine and the motor to a wheel (stepless transmission CVT).

The motor has only the function of assisting the engine power during acceleration or driving the engine during initial start-up.

However, in the hybrid vehicle according to the prior art, it is difficult to form a negative pressure due to the characteristics of the vehicle, thereby making it difficult to secure a stable braking force of the vehicle.

The main causes of the difficulty of negative pressure formation are

Atkinson cycles (high efficiency cycles with larger expansion ratios than conventional auto cycles) are used, with CVT loads and alternator loads.

1 is a view illustrating an operation principle of a booster applied to a hybrid vehicle according to the prior art.

Referring to Figure 1, the booster according to the prior art by applying the atmospheric pressure and the vacuum principle, amplified (about 7 times) by using the negative pressure on the engine intake side to the force transmitted to the wheel.

First, assuming that the booster is connected to the brake, the valve is moved from the beginning by pressing the vacuum pedal inside the booster.

At this time, the relay valve opens the air valve to introduce air.

Then, the introduced air moves the master cylinder.

The booster using the movement of the atmosphere (the property of moving the air to the vacuum) by the pressure difference amplifies the pedaling force.

An object of the present invention is to provide a negative pressure control method of a hybrid vehicle that can ensure a stable braking force by maintaining a constant negative pressure of the vehicle using a motor of the hybrid vehicle.

In order to achieve the above object, the present invention provides a negative pressure control method of a hybrid vehicle, in which the motor of the hybrid vehicle assists the engine power when the vehicle accelerates or recovers the power of the vehicle when decelerating. Separately, the brake auxiliary pressure of the vehicle is prevented from falling below the target negative pressure, and the motor auxiliary torque value is calculated by starting the motor control torque when the brake negative pressure falls below a certain value so as to maintain a constant negative pressure of the vehicle to secure a stable braking force. It is characterized by compensating for the negative pressure due to the load of the vehicle through the motor assistance.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. While many specific details, such as the following description and the annexed drawings, are shown to provide a more general understanding of the invention, these specific details are illustrated for the purpose of explanation of the invention and are not meant to limit the invention thereto. And a detailed description of known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

An embodiment of the present invention is to enable a vehicle to maintain a constant negative pressure by using a motor of the hybrid vehicle, to ensure a stable braking force by maintaining a constant negative pressure of the vehicle by using a motor in addition to the function of the existing hybrid vehicle.

2 is a diagram illustrating a basic configuration of a hybrid vehicle equipped with a CVT, and FIG. 3 is a diagram illustrating a relationship between a brake negative pressure and a motor assist time.

As shown in FIG. 3, when the brake negative pressure starts to fall below a predetermined value, motor control is started.

This is not because the motor assists the power of the vehicle to generate the driving force but compensates for the negative pressure reduction due to the load of the vehicle through the motor assistance.

The principle that negative pressure is generated through the motor assistance is as follows.

Generate motor auxiliary torque → Decrease required engine torque → Decrease opening amount of idle speed controller (ISC) → Increase negative pressure in intake port → Increase negative pressure of booster

All necessary motor auxiliary torque calculations are as follows.

Control starts when the brake negative pressure starts to fall below the target negative pressure and reaches the low judgment negative pressure.

The engine resistance torque and CVT clutch load value at which engine starting can be maintained are received from the control unit ECU.

The auxiliary torque value is calculated by subtracting the engine torque value required to maintain the target negative pressure and engine speed (RPM) from the engine idle demand torque including all loads.

The calculated auxiliary torque value is the torque that the motor should support the vehicle, and adds a PI control value using the difference between the target negative pressure and the current negative pressure.

In order to prevent overload of the motor and fluctuations in the engine speed, the maximum and minimum values are set and the motor torque increase rate is limited.

The motor control unit MCU transmits a torque value that the motor should support to the engine to the engine control unit ECU and the hybrid control unit HCU.

The control ends when the brake negative pressure reaches the end negative pressure.

4 is a signal flow diagram illustrating negative pressure improving logic of a hybrid vehicle according to an exemplary embodiment of the present invention.

Referring to FIG. 4, a flow of control operations will be described by dividing a signal supplied from a motor control unit MCU to an engine control unit ECU and a signal supplied to a hybrid control unit HCU.

First, the flow of control operation according to the signal supplied from the motor control unit MCU to the engine control unit ECU will be described.

Negative pressure maintenance Motor auxiliary torque (To ECU) → Required engine torque decrease → ISC opening amount decrease → Negative pressure rise in the intake port → Booster negative pressure rise → Brake pedal can be activated by negative pressure rise in the booster.

In this state, the control operation flow according to the signal supplied from the motor control unit MCU to the hybrid control unit HCU is as follows.

Negative pressure maintenance Motor auxiliary torque (To HCU) → Increase motor drive torque → Compensate engine torque decrease by increasing motor drive torque.

As described above, the hybrid vehicle negative pressure improvement logic according to an embodiment of the present invention is a brake negative pressure of the vehicle separate from the original function of the hybrid motor in which the motor assists the engine power when the vehicle accelerates or recovers the power of the vehicle when the motor decelerates. Prevents falling below the target negative pressure.

As described above, the negative pressure control method of the hybrid vehicle according to the present invention can improve the braking performance of the hybrid vehicle, and a separate braking assistance device is unnecessary.

Claims (6)

In the negative pressure control method of a hybrid vehicle, In addition to the inherent function of the hybrid motor, in which the motor of the hybrid vehicle assists the engine power when the vehicle accelerates or recovers the vehicle's power when decelerating, the brake underpressure of the vehicle is prevented from falling below the target negative pressure, and the vehicle negative pressure is kept constant Hybrid vehicle, characterized by calculating the motor auxiliary torque value at the time when the brake negative pressure falls below a certain value to ensure stable braking force to start the motor control to compensate for the negative pressure reduction due to the load of the vehicle through the motor assistance Negative pressure control method. The method of claim 1, Comparing whether the brake negative pressure starts to fall below the target negative pressure to reach a low determination negative pressure; Receiving engine resistance torque and continuously variable transmission (CVT) clutch load value from the control unit ECU, where the engine starting can be maintained when the brake negative pressure reaches the low determination negative pressure; Calculating an auxiliary torque value by subtracting an engine torque value necessary to maintain a target negative pressure and an engine speed (RPM) to an engine idle demand torque including all loads; A method for controlling the negative pressure of a hybrid vehicle, characterized by comprising the step of assisting torque to the vehicle with the calculated auxiliary torque value. The method of claim 2, And a PI control value using a difference between a target negative pressure and a current negative pressure to the calculated auxiliary torque value. The method of claim 3, A method of controlling a negative pressure of a hybrid vehicle, the method further comprising: setting a maximum and a minimum value and limiting a motor torque increase rate to prevent an overload of the motor and a change in engine speed. The method of claim 2, A method for controlling a negative pressure of a hybrid vehicle, characterized by further comprising the step of supplying a torque value that the motor should assist the engine to the engine control unit and the hybrid control unit. The method of claim 2, And ending the negative pressure control when the brake negative pressure reaches the termination negative pressure.

Images