JP3648992B2 - Engine starter for hybrid vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel pump control device for an engine of a hybrid vehicle, and more particularly to appropriate control of the start of operation of a fuel pump when starting the engine.
[0002]
[Prior art]
A hybrid vehicle is a kind of electric vehicle, has an engine and an electric motor as a propulsion power source, and has attracted attention as a technology that meets the demand for low pollution. In contrast to starting an engine with a dedicated starter motor in a vehicle equipped with an engine, in a hybrid vehicle, the engine can be started with an electric motor for propulsion and the starter motor can be eliminated.
[0003]
In a hybrid vehicle, for example, the engine is started by the following procedure;
(1) When the driver turns on the ignition start switch,
(2) The electric motor rotates, the rotational force is transmitted to the engine, the engine rotates,
(3) With the detection of engine rotation as a trigger, the fuel pump operates, fuel injection and ignition start.
[0004]
[Problems to be solved by the invention]
In the above procedure, the fuel pump is activated and fuel injection is started with detection of engine rotation as a trigger. However, when the hybrid vehicle is not used for a long time, the fuel pressure in the fuel pump connecting the fuel tank and the engine is lowered. There is a time lag from the start of operation of the fuel pump until the fuel pressure increases. Therefore, the fuel pressure may not be sufficiently increased at the start of fuel injection.
[0005]
Thus, conventionally, although it is a short period from the start of fuel injection, the fuel pressure may not be sufficiently increased. When the fuel pressure is low, the air-fuel ratio does not become an appropriate value, and as a result, the emission value, engine startability and drivability may be adversely affected. It is desirable to reduce this kind of adverse effect as much as possible.
[0006]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel pump control device capable of quickly increasing the fuel pressure when starting the engine.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention includes an engine and an electric motor. When the engine is started, a rotational force of the electric motor is applied to the engine and fuel for supplying fuel to the engine is provided. An engine starter for a hybrid vehicle for operating a pump , wherein after the rotation control of the electric motor is started in response to the generation of an engine start request, the operation of the fuel pump is started, and the electric motor rotation by that to increase the fuel pressure to the fuel pressure before the engine rotational speed rises reaches the predetermined value or a value close required to perform the fuel injection, the rotation control is started to start the engine rotation of the electric motor the fuel pressure is increased during the lag time between, to control the fuel injection system and the ignition device according to the engine speed ene Drives the emissions characterized Rukoto.
[0008]
According to the present invention, since the fuel pump is started in response to the generation of the engine start request without waiting for detection of engine rotation, the fuel pressure can be increased at an early stage. As a result, an appropriate amount of fuel can be supplied to the engine from an early stage, and exhaust characteristics, engine startability, and drivability can be improved.
[0009]
The engine start request is generated, for example, when an ignition start switch is turned on. Preferably, after the operation of the fuel pump, the operation of the fuel pump is continued until the fuel pressure during normal pump operation is secured. For example, even when an engine stop request is generated immediately after the pump is operated, the pump is not stopped until the fuel pressure is raised to a sufficient level. Therefore, at the next generation of the engine start request, the pressure increase can be started from the high fuel pressure as a starting point, and a faster fuel pressure increase can be expected. Note that whether or not the necessary fuel pressure is secured is determined, for example, based on whether or not a predetermined time has elapsed since the start of the pump operation.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments (hereinafter referred to as embodiments) of the invention will be described with reference to the drawings. FIG. 1 shows a drive system for a hybrid vehicle to which the fuel pump control device of the present invention is applied. This system has an engine 10 and first and second motor generators 12 and 14 as power sources. Each motor generator functions as a motor or a generator as required. The engine 10 is connected to a planetary gear carrier 18 of the planetary gear mechanism 16, and the rotors of the first and second motor generators 12 and 14 are connected to a sun gear 20 and a ring gear 22, respectively. The ring gear 22 is connected to the wheels 24 via a power transmission mechanism.
[0011]
In the planetary gear mechanism 16, if the rotation speed Ns of the sun gear, the rotation speed Nc of the planetary carrier, and the rotation speed Nr of the ring gear are the gear ratio ρ of the sun gear and the ring gear,
[Expression 1]
Ns = Nr− (Nr−Nc) (1 + ρ) / ρ (1)
It has the relationship shown by. That is, if two of the three rotation speeds Ns, Nc, and Nr are determined, another rotation speed is determined. Since the rotation speed Nr of the ring gear is determined by the vehicle speed, if one of the planetary carrier rotation speed Nc (engine rotation speed) and the sun gear rotation speed Ns (first motor generator rotation speed) is determined, the other Is determined.
[0012]
In the present hybrid system, the engine and the two motor generators are controlled using the relationship of the above formula (1). The engine output is distributed by the planetary gear mechanism, and is used for driving the wheels and generating electricity by the motor generator. The motor generator functions as a motor for rotating the wheels or functions as a generator for charging the main battery 26.
[0013]
The above two motor generators are controlled by the hybrid ECU 28. Specifically, the hybrid ECU 28 sends a switching control signal to an inverter (not shown) of each motor generator. The hybrid ECU 28 controls both motor generators, so that the engine speed is determined according to the equation (1). In other words, the hybrid ECU 28 controls the engine speed.
[0014]
The engine ECU 30 detects the current engine speed Ne using the engine speed sensor 32, and controls the engine 10, particularly the fuel injection device 34 and the ignition device 36, according to the speed Ne. As the rotation speed sensor 32, it is preferable to provide a resolver in the engine output section (planetary carrier section).
[0015]
The fuel pump 40 installed in the fuel tank 38 is also controlled by the engine ECU 30. The engine ECU 30 turns on / off the pump operation switch 41 of the fuel pump 40. When the pump operation switch 41 is closed (ON), the power of the auxiliary battery 42 is supplied to the fuel pump 40, the fuel pump 40 is operated, and fuel is supplied to the engine 10 via the fuel pipe 43. During operation of the engine 10, the fuel pump 40 is always operating, and a substantially constant fuel pressure (hereinafter referred to as a specified pressure P0) is generated in the fuel pipe 43. The specifications of the fuel pump 40 and other configurations are set so that the specified pressure P0 necessary for the fuel injection device 34 to perform appropriate fuel injection can be obtained.
[0016]
Next, the engine start of the system of FIG. 1, particularly the engine start when the driver turns on the ignition start switch 44 by key operation will be described.
[0017]
Schematically, the hybrid ECU 28 rotates the motor generator 12 to increase the engine speed Ne, while the engine ECU 10 starts driving the fuel pump 40, the fuel injection device 34, and the ignition device 36. Conventionally, the engine ECU 10 knows the start of engine rotation based on the detection signal of the engine rotation sensor 32 and then operates the fuel pump 40, so that the increase in fuel pressure is delayed. Therefore, in the present embodiment, the following fuel pump control is performed in order to increase the fuel pressure early.
[0018]
Referring to FIG. 2, when the ignition start switch 44 is turned on, an ignition start signal Sst is input to the hybrid ECU 28 (S10). The hybrid ECU 28 generates an engine activation request Rst and transmits it to the engine ECU 30 (S12). At this point, the engine ECU 30 side can know the necessity of starting the engine at an early stage. Almost simultaneously with S12, the hybrid ECU 28 starts processing for rotating the engine (S14). Here, when the hybrid ECU 28 rotates the motor generator 12 as a motor, the rotational force is transmitted to the engine 10 via the planetary gear mechanism 16 and the engine 10 rotates. There is a time lag for various control processes of the hybrid system, although it is relatively short, from the generation of the engine start request Rst to the actual start of rotation of the motor and the engine.
[0019]
On the other hand, the engine ECU 30 that has received the engine start request Rst from the hybrid ECU 28 in S12 immediately operates the fuel pump 40 as follows. First, it is determined whether or not Rst is on and Fst is off (S20). Fst is an engine start storage flag, and is used to determine whether or not the engine is first started.
[0020]
At the Rst reception stage, S20 is YES. The engine ECU 30 clears the fuel pressure increase counter Tfp (S22), and turns on the engine start storage flag Fst (S24). The fuel pressure increase counter Tfp is automatically incremented every predetermined period, and is used as a timer for measuring an elapsed time from the start of operation of the fuel pump 40.
[0021]
In S26, the fuel pressure increase counter Tfp is compared with a predetermined threshold value T0. Here, since Tfp has just been cleared, Tfp is less than T0. Therefore, the engine ECU 30 sends a signal to the pump operation switch 41 to operate the fuel pump 40 (S28).
[0022]
Returning to S20, the engine ECU 30 checks the states of the engine start request Rst and the engine start storage flag Fst again. Since Fst is now on, the process proceeds to S26, where the fuel pressure increase counter Tfp is again compared with the threshold value T0. While the counter Tfp is less than the threshold value T0, the operation of the fuel pump 40 is always continued, that is, the stop of the fuel pump 40 is prohibited.
[0023]
When counter Tfp is equal to or greater than threshold value T0, engine ECU 30 determines whether a fuel cut request or an engine stop request has occurred (S30). If there is no such request, the fuel pump 40 is continuously driven (S28). On the other hand, if S30 is YES, the fuel pump 40 is stopped (S32).
[0024]
FIG. 3 shows a time chart of the engine start process. When the ignition start signal Sst is turned on, the hybrid ECU 28 generates an engine start request Rst and sends it to the engine ECU 30. Simultaneously with the generation of Rst, motor rotation control is started. After the delay time Td for the hybrid system related control processing has elapsed, the motor actually rotates and the engine speed Ne rises.
[0025]
On the other hand, on the engine side, the fuel pump 40 is operated immediately after receiving the engine start request Rst. When the vehicle has not been used for a long time, the fuel pressure in the fuel pipe 43 gradually decreases and decreases. The fuel pressure is increased by the operation of the fuel pump 40. When engine rotation is detected, the fuel injection device 34 and the ignition device 36 are driven, and the engine 10 is started.
[0026]
Here, conventionally, a notification regarding engine start such as an engine start request Rst is not sent from the hybrid ECU 28 to the engine ECU 30. The engine ECU 30 determines the necessity of starting the engine by itself based on the input of the engine rotation sensor 32. Then, the fuel pump 40 is started with the detection of engine rotation as a trigger, but it takes some time for the fuel pressure to rise. Therefore, as shown by a dotted line in FIG. 3, there is a period during which the fuel pressure is low, although it is a short time after the start of fuel injection. If the fuel pressure is low, the air-fuel ratio does not become an appropriate value, and the emission value, engine startability, and drivability may be adversely affected.
[0027]
However, in this embodiment, the hybrid ECU 28 transmits an engine start request Rst to the engine ECU 30. Prior to engine rotation detection, the engine ECU 30 immediately operates the fuel pump 40 in response to the generation of the engine start request Rst. Therefore, the fuel pressure can be increased during this period by using the delay time Td until the engine rotation starts. When the engine speed Ne rises, it can be expected that the fuel pressure reaches the specified value P0 or a value close thereto as shown in the figure. As a result, appropriate fuel supply is performed from an early stage, the air-fuel ratio becomes an appropriate value, and the emission value, engine startability, and drivability can be improved.
[0028]
Further, in the present embodiment, the advantage described below is obtained by providing the determination step of S26 in FIG.
[0029]
The threshold value T0 of S26 is determined based on the time required for the fuel pressure to rise. When the fuel pump 40 is started in a state in which the fuel pressure can be regarded as the most drastically reduced, the time taken until the fuel pressure has finished rising and becomes constant (until stabilization) is defined as the rising time t0 (msec). . That is, the rising time t0 is a time from when the pump is operated until the fuel pressure reliably reaches the specified pressure P0. Based on the rising time t0, the threshold value T0 is determined such that at least the time t0 has elapsed from the pump operation when the fuel pressure increase counter Tfp = T0. Therefore, the operation of the fuel pump 40 is continued until the fuel pressure of the specified value P0 (the fuel pressure during normal pump operation) is secured by the determination in S26, that is, the stop of the fuel pump 40 is prohibited.
[0030]
Here, it is assumed that an engine stop request or a fuel cut request is generated before the completion of the increase in fuel pressure. Even if these requests occur, the fuel pressure is raised to the specified pressure P0 by the above control, and then the fuel pump 40 is stopped. Therefore, when the engine start request is generated next time, the fuel pressure can be increased starting from a higher fuel pressure, so that the fuel pressure can reach the specified pressure P0 again at an early stage. As a result, an appropriate amount of fuel can be supplied more reliably immediately after the engine is started.
[0031]
The preferred embodiment of the present invention has been described above. As a modification, a pressure sensor for detecting the fuel pressure may be provided in the fuel pipe or other appropriate location. When the engine start request is generated and the fuel pressure is reduced, the above-described control is performed and the fuel pump is started. If the fuel pressure has not dropped, the fuel pump is started with the detection of engine rotation as a trigger. According to this embodiment, the fuel pump can be operated more efficiently. The determination of the fuel pressure drop is performed by comparing the detected value of the fuel pressure sensor with a predetermined threshold value. The threshold value for determination is set to a value that is equal to or slightly lower than the specified value P0 of the fuel pressure, for example.
[0032]
2 may be performed not only when the ignition start switch is turned on, but also when another engine is started. In a hybrid vehicle, the engine is turned on / off according to the state of charge of the battery and the driving conditions of the vehicle. Even when the engine is started during traveling, the fuel pump may be activated at an early stage in response to the generation of an engine start request.
[0033]
Further, the present invention is not limited to the configuration shown in FIG. 1, and can be applied to any type of hybrid vehicle. The present invention applies to both a parallel hybrid (a vehicle is driven by both an engine and a motor) and a series hybrid (a generator is driven by an engine, a motor is driven by generated power, and a vehicle is driven by the rotational force of the motor). Applicable.
[0034]
【The invention's effect】
As described above, according to the present invention, when starting the engine, the fuel pump can be started at an early stage to increase the fuel pressure, and the exhaust characteristics, engine startability, and drivability are improved by appropriate fuel supply. Can be achieved.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a hybrid system to which a fuel pump control device according to an embodiment of the present invention is applied.
FIG. 2 is a flowchart showing an engine start process of the system of FIG.
FIG. 3 is a time chart when the engine is started according to FIG. 2;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Engine, 12 1st motor generator, 14 2nd motor generator, 16 planetary gear mechanism, 24 wheels, 28 hybrid ECU, 30 engine ECU, 32 engine rotation sensor, 40 fuel pump, 41 pump operation switch, 43 fuel pipe, 44 Ignition start switch, Ne engine speed, Rst engine start request, Sst ignition start signal.

Claims (3)

Has an engine and an electric motor, when starting the engine, together with providing a rotational force of the electric motor to the engine, engine starting for a hybrid vehicle for operating the fuel pump for fuel supply to the engine A device ,
In response to the generation of an engine start request, after the rotation control of the electric motor is started , the operation of the fuel pump is started, and the fuel pressure injects fuel before the engine speed rises due to the rotation of the electric motor. by raising the fuel pressure to reach a predetermined value or a value close required, the fuel pressure is increased during the lag time until the start engine speed from the rotation control start of the electric motor, engine and controlling the fuel injection system and the ignition system in accordance with the number, the hybrid vehicle engine start system according to claim Rukoto to drive the engine. The apparatus of claim 1.
The engine start apparatus for a hybrid vehicle, wherein the engine start request is generated when an ignition start switch is turned on. The apparatus of claim 2.
Wherein after actuation of the fuel pump, until fuel pressure during normal pump operation is ensured, the engine starting system of the hybrid vehicle, characterized by continuing the operation of the fuel pump.

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