Vehicle control system

Abstract

To prevent the vehicle from sliding backward. [Solution] A vehicle control device (100) for controlling a vehicle comprising an engine (1), an electric motor (2) connected to the engine (1) so as to transmit power, and a battery (8) that serves as the power source for the electric motor (2), comprising: an assist control means (102) that performs engine assist by the electric motor (2) on the condition that the State of Charge (SOC) of the battery (8) is equal to or greater than an assist permission threshold; and a threshold changing means (105) that reduces the assist permission threshold when the SOC of the battery (8) is less than the assist permission threshold and the vehicle slides backward.

Description

Technical Field

[0001] The present invention relates to a vehicle control device for controlling a vehicle equipped with an engine, an electric motor, and a battery.

Background Art

[0002] Patent Document 1 discloses a vehicle control device that executes an assist mode in which the driving forces of an engine and an electric motor are transmitted to wheels on condition that the SOC (State Of Charge) of a battery exceeds a predetermined lower limit value.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a vehicle equipped with an engine, output limitation of the engine may be performed in order to suppress deterioration of exhaust gas at the time of cold start when an exhaust gas purification catalyst has not reached an activation temperature. When an assist mode is executed on condition that the SOC of a battery exceeds a predetermined lower limit value as in Patent Document 1, for example, in a state where a vehicle is at a location with a gradient such as a slope, the SOC is smaller than the predetermined lower limit value (that is, the assist mode is not executed), and vehicle creep may occur due to the output limitation of the engine.

[0005] The present invention has been made in view of such circumstances, and an object thereof is to prevent vehicle creep.

Means for Solving the Problems

[0006] The vehicle control device of the present invention is a vehicle control device for controlling a vehicle comprising an engine, an electric motor connected to the engine so as to transmit power, and a battery that serves as a power source for the electric motor, and is characterized by comprising: an assist control means for performing engine assist by the electric motor on the condition that the State of Charge (SOC) of the battery is equal to or greater than an assist permission threshold; and a threshold changing means for reducing the assist permission threshold when the SOC of the battery is less than the assist permission threshold and the vehicle slides backward. [Effects of the Invention]

[0007] According to the present invention, it is possible to prevent the vehicle from sliding downwards. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows the schematic configuration of the main parts of an automobile according to an embodiment. [Figure 2] This diagram shows the functional configuration of ECM. [Figure 3] This is a flowchart showing the processes performed by ECM. [Modes for carrying out the invention]

[0009] A vehicle control device (100) according to one embodiment of the present invention is a vehicle control device for controlling a vehicle comprising an engine (1), an electric motor (2) connected to the engine (1) so as to transmit power, and a battery (8) that serves as a power source for the electric motor (2), and comprises assist control means (102) that performs engine assist by the electric motor (2) on the condition that the State of Charge (SOC) of the battery (8) is equal to or greater than an assist permission threshold, and threshold changing means (105) that reduces the assist permission threshold when the SOC of the battery (8) is less than the assist permission threshold and the vehicle slides backward. This makes it possible to prevent the vehicle from sliding backward. [Examples]

[0010] Hereinafter, preferred embodiments of the present invention will be described with reference to the attached drawings. Figure 1 shows a schematic configuration of the main parts of an automobile according to an embodiment. As shown in Figure 1, the automobile is a hybrid vehicle equipped with an engine 1 and a motor generator 2.

[0011] Engine 1 is an internal combustion engine having multiple cylinders, and is configured to burn gasoline fuel and produce power by performing a series of four strokes for each cylinder: an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. The power output from the output shaft of engine 1 is transmitted to the drive wheels 5 via the transmission 3 and output shaft 4.

[0012] The motor-generator 2 is connected to the engine 1 via pulleys 6a, 6b and a belt 7 so as to be able to transmit power. The motor-generator 2 is connected to the battery 8. The motor-generator 2 functions as an electric motor that rotates the output shaft of the engine 1 when driven by the battery 8 as a power source. The motor-generator 2 also functions as a generator that generates electricity to charge the battery 8 when driven by the output shaft of the engine 1. Although the motor-generator 2 is shown as being connected to the engine 1 via pulleys 6a, 6b and a belt 7, it is not limited to this configuration, and may be connected to the engine 1 via a clutch, gears, or the like so as to be able to transmit power.

[0013] Furthermore, automobiles are equipped with an ECM (Engine Control Module) 100 (see Figure 2). The ECM 100 controls the engine, including fuel supply control and ignition timing control. The ECM 100 is composed of a computer unit that includes, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), flash memory for storing backup data, input ports, and output ports.

[0014] In this embodiment, the ECM 100 functions as a control device for a vehicle to which the present invention is applied. Hereinafter, the description will focus on the functions as a control device for a vehicle to which the present invention is applied. Fig. 2 shows the functional configuration for the ECM 100 to function as a control device for a vehicle to which the present invention is applied. As shown in Fig. 2, the ECM 100 includes a SOC acquisition unit 101, an assist control unit 102, an output limitation unit 103, a slip-down determination unit 104, and a threshold change unit 105.

[0015] The SOC acquisition unit 101 acquires the SOC, which is an index representing the charge rate or charge state of the battery 8.

[0016] The assist control unit 102 performs engine assist by the motor generator 2 on the condition that the SOC of the battery is not less than a preset assist permission threshold.

[0017] The output limitation unit 103 limits the output of the engine 1 to suppress exhaust gas deterioration during cold start when the exhaust gas purification catalyst has not reached the activation temperature. The output limitation unit 103 releases the output limitation of the engine when the exhaust gas purification catalyst reaches the activation temperature.

[0018] The slip-down determination unit 104 determines the occurrence of vehicle slip-down. The determination of the occurrence of vehicle slip-down may be to determine that the occurrence of slip-down is expected, or to determine that slip-down actually occurs. For example, the gradient is detected by a gradient sensor mounted on the vehicle, and when the detected gradient is not less than a predetermined gradient, it is determined that slip-down occurs. Alternatively, after the brake is released, the traveling direction of the vehicle is detected by an acceleration sensor mounted on the vehicle, and it is determined that slip-down occurs.

[0019] The threshold change unit 105 reduces the assist permission threshold when the SOC of the battery 8 is less than the assist permission threshold and the vehicle slips down due to the output limitation of the engine by the output limitation unit 103. How much the assist permission threshold is reduced is preset.

[0020] Figure 3 is a flowchart showing the processing executed by the ECM 100 that functions as a control device for a vehicle. In step S1, the SOC acquisition unit 101 acquires the SOC of the battery 8.

[0021] In step S2, the assist control unit 102 determines whether the SOC of the battery 8 acquired in step S1 is less than the assist permission threshold. If the SOC is less than the assist permission threshold, the process proceeds to step S3. If the SOC is greater than or equal to the assist permission threshold, the flowchart ends.

[0022] In step S3, the output limit unit 103 determines whether to limit the output of the engine 1. If the output of the engine 1 is to be limited, the output of the engine 1 is limited and the process proceeds to step S4. If the output of the engine 1 is not to be limited, the flowchart ends.

[0023] In step S4, the slip-down determination unit 104 determines whether a slip-down of the automobile has occurred. If a slip-down of the automobile has occurred, the process proceeds to step S5. If a slip-down of the automobile has not occurred, the flowchart ends.

[0024] In step S5, the threshold change unit 105 decreases the assist permission threshold.

[0025] Through the above process, if the State of Charge (SOC) of the battery 8 is lower than the assist permission threshold, and the output limiting unit 103 limits the engine output, causing the vehicle to roll backward, the assist permission threshold is reduced. For example, if the vehicle is parked on a slope or other incline and starts moving during a cold start, the output limiting unit 103 may limit the engine output, potentially causing the vehicle to roll backward. In this case, reducing the assist permission threshold enables engine assist by the motor generator 2. By providing engine assist, it is possible to maintain the output limit of the engine 1 (while suppressing the deterioration of exhaust emissions) and prevent the vehicle from rolling backward due to the output limit of the engine 1. In addition, the motor generator 2 helps to accelerate the warming up of the engine by leading the engine 1 in.

[0026] Now, let's discuss the assist permission threshold. The assist permission threshold is set to the SOC of the battery 8 sufficient for engine assist by the motor generator 2 and for a predetermined function. The predetermined function is, for example, the restart of the engine 1 by the motor generator 2 after idling stop. The threshold modification unit 105 then reduces the assist permission threshold so that the SOC of the battery 8 is sufficient for engine assist by the motor generator 2 but insufficient for the predetermined function. For example, the assist permission threshold is reduced by the amount of SOC required to restart the engine 1 during idling stop. In this case, if idling stop itself is disabled, restarting the engine 1 becomes unnecessary.

[0027] In this way, when the threshold changing unit 105 reduces the assist permission threshold, the battery 8 is made to ensure that the minimum power necessary for engine assist by the motor generator 2 is secured, but a power shortage is permitted for a predetermined function, that is, the predetermined function is not performed. The predetermined function is one that does not contribute to preventing the vehicle from rolling backward and is not essential for the vehicle to run. Examples of predetermined functions include the restart of the engine 1 during idling stop as described above, as well as the operation of the air conditioning, sound equipment, and car navigation. The predetermined function may be a single function or may include multiple functions.

[0028] In this embodiment, the assist permission threshold is reduced when the engine output is limited by the output limiting unit 103, but it is not limited to this. The assist permission threshold may also be reduced when the State of Charge (SOC) of the battery 8 is lower than the assist permission threshold and the vehicle is sliding backward. In the flowchart of Figure 3, the processing in step S3 may be omitted.

[0029] Although embodiments of the present invention have been described in detail above with reference to the drawings, each embodiment is merely a specific example of how the present invention can be implemented. The technical scope of the present invention is not limited to each embodiment. Various modifications of the present invention are possible without departing from its spirit, and these modifications are also included within the technical scope of the present invention. A vehicle control device to which the present invention is applied is composed of a computer device equipped with, for example, a CPU, ROM, RAM, etc., and the functions of each means are realized when the CPU executes a predetermined program stored in, for example, ROM. [Explanation of symbols]

[0030] 1: Engine, 2: Motor Generator, 8: Battery, 100: ECM, 101: SOC Acquisition Unit, 102: Assist Control Unit, 103: Output Limiting Unit, 104: Slip-down Detection Unit, 105: Threshold Change Unit

Claims

1. A vehicle control device for controlling a vehicle comprising an engine, an electric motor connected to the engine so as to transmit power, and a battery that serves as the power source for the electric motor, An assist control means that performs engine assist by the electric motor, provided that the State of Control (SOC) of the battery is equal to or greater than the assist permission threshold, A vehicle control device characterized by comprising a threshold changing means for reducing the assist permission threshold when the State of Control (SOC) of the battery is smaller than the assist permission threshold and the vehicle slides backward.

2. The engine is equipped with an output limiting means for limiting the output of the engine, The vehicle control device according to claim 1, characterized in that the threshold changing means reduces the assist permission threshold when the SOC of the battery is smaller than the assist permission threshold and the output limiting means limits the output of the engine, causing the vehicle to slide backward.

3. The assist permission threshold is set as the SOC of the battery sufficient for engine assist by the electric motor and for a predetermined function. The vehicle control device according to claim 1 or 2, characterized in that the threshold changing means reduces the assist permission threshold so that the State of Charge (SOC) of the battery is sufficient for engine assist by the electric motor, but insufficient for the predetermined function.

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