Hybrid vehicle control device

Abstract

To improve engine restart performance and enable a speed range in which engine assist can be performed to be expanded.SOLUTION: A control device 100 is for a hybrid vehicle which comprises: an engine 1; an electric motor 2; and a transmission mechanism 3 provided with a crank pulley 4 connected to a crank shaft 1a of the engine 1 and having a variable pulley diameter, an electric motor pulley 5 connected to a rotary shaft 2a of the electric motor 2 and having a variable pulley diameter, and a belt 6 connecting the crank pulley 4 and the electric motor pulley 5. The control device has pulley ratio change means 103 which, when the engine 1 is restarted using the electric motor 2, sets a pulley ratio, a ratio of the pulley diameter of the electric motor pulley 5 to the pulley diameter of the crank pulley 4, to a predetermined value enabling the engine 1 to be restarted, and decreases the pulley ratio to a value smaller than a predetermined value according to a rotation speed of the engine 1 when the electric motor 2 assists driving of the engine 1.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a control device for a hybrid vehicle.

Background Art

[0002] Patent Document 1 discloses a hybrid vehicle that connects a propeller shaft connecting a transmission connected to a diesel engine and a differential that drives drive wheels, and a rotating shaft of a motor generator via a continuously variable transmission mechanism. When performing regenerative power generation by the motor generator, by making the diameter of the pulley attached to the rotating shaft of the motor generator smaller than the diameter of the pulley attached to the propeller shaft, high-efficiency regenerative power generation can be performed in a wide speed range.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Document 1 focuses on improving the efficiency of regenerative power generation in a hybrid vehicle, but has not considered the configuration for transmitting power from the electric motor to the engine for engine restart or engine assist, and there is room for improvement.

[0005] The present invention has been made in view of such circumstances, and an object thereof is to improve the restartability of the engine and to expand the speed range in which engine assist can be performed.

Means for Solving the Problems

[0006] The control device for a hybrid vehicle according to the present invention includes an engine, an electric motor, a crank pulley connected to the crankshaft of the engine and having a variable pulley diameter, an electric motor pulley connected to the rotating shaft of the electric motor and having a variable pulley diameter, and a transmission mechanism including a belt connecting the crank pulley and the electric motor pulley. When restarting the engine by the electric motor, the pulley ratio, which is the ratio of the pulley diameter of the crank pulley to the pulley diameter of the electric motor pulley, is set to a predetermined value at which the restart of the engine is possible. When assisting the driving of the engine by the electric motor, pulley ratio changing means is provided for making the pulley ratio smaller than the predetermined value according to the rotational speed of the engine.

Advantages of the Invention

[0007] According to the present invention, it is possible to improve the restartability of the engine and expand the speed range in which engine assist can be performed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0009] A control device 100 for a hybrid vehicle according to an embodiment of the present invention includes an engine 1, an electric motor 2, a crank pulley 4 connected to a crankshaft 1a of the engine 1 and having a variable pulley diameter, an electric motor pulley 5 connected to a rotating shaft 2a of the electric motor 2 and having a variable pulley diameter, and a transmission mechanism 3 including a belt 6 connecting the crank pulley 4 and the electric motor pulley 5. When the engine 1 is restarted by the electric motor 2, a pulley ratio, which is a ratio of the pulley diameter of the crank pulley 4 to the pulley diameter of the electric motor pulley 5, is set to a predetermined value at which the engine 1 can be restarted. When the electric motor 2 assists in driving the engine 1, the pulley ratio is made smaller than the predetermined value according to the rotational speed of the engine 1 by a pulley ratio changing means 103. Thereby, it is possible to improve the restartability of the engine 1 and expand the speed range in which engine assist can be performed.

Example

[0010] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a schematic configuration of a main part of an automobile which is a hybrid vehicle according to an embodiment. As shown in FIG. 1, the automobile is equipped with an engine 1, an ISG (Integrated Starter Generator) 2, and a transmission mechanism 3 connecting the engine 1 and the ISG 2.

[0011] The engine 1 is an internal combustion engine having a plurality of cylinders, and is configured to perform a series of four strokes including an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke for each cylinder and output power. The power output from the crankshaft 1a by the engine 1 is transmitted through a clutch 7 to a transmission 8 for speed change, and then transmitted to drive wheels 11 through a differential gear 9 and a drive shaft 10, and used for driving the automobile.

[0012] ISG2 functions as a generator that generates electricity using deceleration energy and charges the battery 12. Also, ISG2 functions as an electric motor for engine assist that uses the battery 12 as a power source to restart the engine 1 during idling stop and assist in driving the engine 1.

[0013] The transmission mechanism 3 includes a crank pulley 4 that is connected to the crankshaft 1a of the engine 1 and has a variable pulley diameter, an ISG pulley 5 that is connected to the rotating shaft 2a of ISG2 and has a variable pulley diameter, and a belt 6 that connects the crank pulley 4 and the ISG pulley 5. The crank pulley 4 and the ISG pulley 5 each have a V-shaped groove, and by changing the groove width, the position of the ring-shaped belt 6 stretched between the two pulleys 4 and 5 can be moved to change the pulley diameter. In this embodiment, ISG2 is an example of the electric motor referred to in the present invention, and the ISG pulley 5 corresponds to the electric motor pulley referred to in the present invention.

[0014] Also, an automobile is equipped with an ECU (Electronic Control Unit) 100 that electronically controls various functions (see Figure 2). The ECU 100 controls engine operation and performs fuel supply control and ignition timing control. The thus-configured ECU 100 is composed of, for example, a computer unit equipped with a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory for storing backup data, an input port, and an output port.

[0015] In this embodiment, the ECU 100 functions as a control device for a hybrid vehicle to which the present invention is applied. Hereinafter, the description will focus on the functions as a control device for a hybrid vehicle to which the present invention is applied. Figure 2 shows the functional configuration for the ECU 100 to function as a control device for a hybrid vehicle to which the present invention is applied. The ECU 100 includes an idling stop control unit 101, an assist control unit 102, and a pulley ratio change unit 103. Also, various information, such as the rotational speed of engine 1, vehicle speed, information indicating the state of battery 12, etc., is input to the ECU 100.

[0016] The idling stop control unit 101 controls the idling stop. For example, when decelerating and the vehicle speed becomes equal to or lower than a predetermined speed, the idling stop control unit 101 stops engine 1. Then, the idling stop control unit 101 restarts engine 1 by ISG2 on the condition that the driver performs an operation such as releasing the brake.

[0017] The assist control unit 102 controls engine assist. For example, according to the vehicle speed, the state of battery 12, the rotational speed of engine 1, etc., the assist control unit 102 assists the driving of engine 1 by ISG2.

[0018] The pulley ratio change unit 103 changes the pulley ratio, which is the ratio of the pulley diameter of crank pulley 4 to the pulley diameter of ISG pulley 5. When restarting engine 1 by ISG2, the pulley ratio change unit 103 sets the pulley ratio to a predetermined value at which the restart of engine 1 is possible. The predetermined value is a relatively large pulley ratio such that the starting torque required for the restart of engine 1 can be transmitted from ISG2. On the other hand, when the pulley ratio is large, when the rotational speed of engine 1 increases, the rotational speed of ISG2 tends to increase. When it is desired to perform engine assist when the rotational speed of engine 1 is high, since ISG2 rotates at a high speed, high output (large power) is required, and there is a possibility that ISG2 cannot cope. Therefore, when assisting the driving of engine 1 by ISG2, the pulley ratio change unit 103 makes the pulley ratio smaller than the predetermined value according to the rotational speed of engine 1, in other words, makes it a relatively small pulley ratio.

[0019] Figure 3 is a flowchart showing an example of the process executed by the ECU 100. In step S1, the idling stop control unit 101 determines whether the conditions for idling stop are satisfied. If the conditions for idling stop are satisfied, the process proceeds to step S2. The conditions for idling stop are, for example, conditions such as during deceleration when the vehicle speed becomes equal to or lower than a predetermined speed.

[0020] In step S2, the pulley ratio change unit 103 increases the pulley diameter of the crank pulley 4 and decreases the pulley diameter of the ISG pulley 5 to set the pulley ratio to a predetermined value at which the engine 1 can be restarted.

[0021] In step S3, the idling stop control unit 101 performs idling stop and stops the engine 1. In step S4, the idling stop control unit 101 restarts the engine 1 by the ISG2 on the condition of an operation such as releasing the brake. By setting the pulley ratio to a predetermined value in step S2, a relatively large pulley ratio can be set when restarting the engine 1 so that the starting torque required for re-braking the engine 1 can be transmitted from the ISG2. Thereby, the restartability of the engine 1 can be improved.

[0022] In step S5, the assist control unit 102 performs assist by the ISG2 according to, for example, the vehicle speed, the state of the battery 12, the rotational speed of the engine 1, and the like. In step S6, the assist control unit 102 waits in the assist state until the rotational speed of the engine 1 reaches a predetermined rotational speed. When the rotational speed of the engine 1 becomes equal to or higher than the predetermined rotational speed, the process proceeds to step S7. Until the rotational speed of the engine 1 reaches the predetermined rotational speed, engine assist is continued without changing the pulley ratio.

[0023] In step S7, the pulley ratio change unit 103 decreases the pulley diameter of the crank pulley 4 and increases the pulley diameter of the ISG pulley 5 to make the pulley ratio smaller than the predetermined value. In step S8, the assist control unit 102 continues engine assist. By making the pulley ratio smaller than a predetermined value in step S7, when power (assist torque) is transmitted from ISG2 to engine 1 while engine 1 is rotating to some extent, a pulley ratio that can also handle a high-output rotation range can be achieved. Thereby, the speed range in which engine assist can be performed can be expanded.

[0024] Here, there is a range in which the operation of the ISG can be guaranteed from the viewpoints of durability and the like, and one of them is the allowable rotational speed. The higher the rotational speed when operating the ISG, the higher the load on the ISG, so the allowable rotational speed, which is the upper limit of the rotational speed, is set. Therefore, when the pulley ratio changing unit 103 changes the pulley ratio in step S7, the rotational speed of ISG2 calculated based on the rotational speed of engine 1 and the pulley ratio is such that it does not exceed the allowable rotational speed of ISG2, in other words, the pulley ratio is changed so that it stays within the allowable rotational speed of ISG2. Thereby, while expanding the speed range in which engine assist can be performed, it is possible to avoid applying a high load to ISG2.

[0025] As described above, when restarting engine 1 by ISG2, the pulley ratio is set to a predetermined value at which restarting of engine 1 is possible, and when assisting the driving of engine 1 by ISG2, according to the rotational speed of engine 1, by making the pulley ratio smaller than a predetermined value, it is possible to improve the restartability of engine 1 and expand the speed range in which engine assist can be performed. Also, when restarting engine 1 by ISG2, by making the pulley ratio relatively large, it also leads to a reduction in NVH (noise and vibration) and power consumption during restarting of engine 1. On the other hand, when assisting the driving of engine 1 by ISG2, by making the pulley ratio relatively large, it also leads to a reduction in fan noise and electromagnetic noise due to a reduction in the rotation of ISG2.

[0026] In addition, when assisting the driving of the engine 1 by the ISG2, the pulley ratio is set to be smaller than a predetermined value. However, in the case of having a function of traveling only by the ISG2 (single - motor traveling), the pulley ratio may also be set to be smaller than the predetermined value even when traveling only by the ISG2.

[0027] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, each embodiment merely shows a specific example in implementing the present invention. The technical scope of the present invention is not limited to each embodiment. The present invention can be variously modified without departing from its gist, and those are also included in the technical scope of the present invention. The control device for a hybrid vehicle to which the present invention is applied is constituted by, for example, a computer device including a CPU, a ROM, a RAM, etc. The functions of each means are realized when the CPU executes a predetermined program stored in the ROM, for example.

Explanation of Reference Numerals

[0028] 1: Engine, 1a: Crankshaft, 2: ISG, 2a: Rotating shaft, 3: Transmission mechanism, 4: Crank pulley, 5: ISG pulley, 6: Belt, 100: ECU, 101: Idling stop control unit, 102: Assist control unit, 103: Pulley ratio change unit

Claims

1. An engine, an electric motor, a hybrid vehicle control device comprising a transmission mechanism including a crank pulley connected to a crankshaft of the engine and having a variable pulley diameter, an electric motor pulley connected to a rotating shaft of the electric motor and having a variable pulley diameter, and a belt connecting the crank pulley and the electric motor pulley, when restarting the engine by the electric motor, setting a pulley ratio, which is a ratio of the pulley diameter of the crank pulley to the pulley diameter of the electric motor pulley, to a predetermined value at which the engine can be restarted, when assisting the driving of the engine by the electric motor, comprising pulley ratio changing means for making the pulley ratio smaller than the predetermined value according to the rotational speed of the engine. A hybrid vehicle control device characterized by this.

2. The pulley ratio changing means changes the pulley ratio so that the rotational speed of the electric motor calculated based on the rotational speed of the engine and the pulley ratio does not exceed the allowable rotational speed of the electric motor. The hybrid vehicle control device according to Claim 1, characterized by this.

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