JP2014237365A - Engine control unit of hybrid vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a hybrid vehicle in which an engine using liquefied gas fuel and a motor are mounted become capable of appropriately controlling a fuel injection amount in starting the engine without deteriorating NV performance.SOLUTION: A hybrid vehicle comprises: an engine 12 which uses liquefied gas fuel; a tank 52; a fuel pump 54; a fuel injection device 56; a fuel supply passage 58; a fuel return passage 60 which returns the liquefied gas fuel to the tank; and a control valve 62 provided for the fuel return passage; and a motor which receives electric power supply from an on-vehicle battery and outputs power. The control unit, when vehicle speed Sv reaches a first threshold value or more V1 in an EV travel mode in which the vehicle travels only by motor output in an engine stop state, executes fuel return control in which the control valve is set to an open state to activate the fuel pump, and the liquefied gas fuel in the fuel supply passage is returned to the tank via the fuel return passage.

Description

  The present invention relates to an engine control device for a hybrid vehicle, and more particularly to an engine control device for a hybrid vehicle equipped with an engine and a motor that use liquefied gas fuel such as LPG (liquefied petroleum gas).

  Conventionally, for example, Japanese Patent Laid-Open No. 9-184459 (hereinafter referred to as Patent Document 1) discloses a start-up control device for an internal combustion engine. In this internal combustion engine start-up control, after the engine is stopped, the fuel temperature rises in the delivery pipe that supplies the fuel to the fuel injection device and the fuel is vaporized, thereby avoiding variations in the fuel injection amount to the engine gin. Therefore, it is described that when there is an engine start request, the engine start is delayed and the fuel in the delivery pipe is returned to the fuel tank via the fuel return path.

  Japanese Unexamined Patent Application Publication No. 2010-894 (hereinafter referred to as Patent Document 2) includes an LPG equipped with an engine that uses LPG as fuel and a motor that is driven by a drive current supplied from a vehicle-mounted battery to output power. A hybrid vehicle is disclosed.

Japanese Patent Laid-Open No. 9-184459 JP 2010-894 A

  In vehicles using liquefied gas such as LPG as fuel, if fuel vaporization is a problem due to engine heat, fuel return control is performed to return the fuel in the delivery pipe to the fuel tank before starting the engine. A technique for suppressing the vaporization of is generally known. In a hybrid vehicle equipped with an engine using liquefied gas fuel, it is necessary to suppress fuel vaporization even when the engine is started during EV traveling. However, as in Patent Document 1, a vehicle that the driver feels when the engine start is delayed. Driving performance (hereinafter referred to as “drivability”) is significantly deteriorated.

  Further, it is conceivable to switch on and off of a fuel pump that sends fuel from the fuel tank to the fuel injection device in accordance with the temperature and pressure of the fuel supplied to the fuel injection device. Since it is difficult to accurately estimate the fuel temperature in the inside, drivability may deteriorate due to variations in the fuel injection amount.

  Furthermore, if the fuel pump is always driven while the vehicle is running with the EV stopped, the power consumption of the fuel pump increases and fuel consumption deteriorates, and the operating sound of the fuel pump is uncomfortable for the driver in the passenger compartment. May be perceived as noise.

  An object of the present invention is a hybrid vehicle equipped with an engine and a motor that uses liquefied gas fuel, and a state in which the fuel injection amount at the start of the engine can be appropriately controlled without deteriorating noise vibration performance (so-called NV performance). It is an object of the present invention to provide an engine control device for a hybrid vehicle.

  An engine control apparatus for a hybrid vehicle according to the present invention includes an engine that uses liquefied gas fuel, a tank that stores the liquefied gas fuel, a fuel pump that delivers the liquefied gas fuel from the tank, and the liquefied gas fuel directed to the engine. A fuel injection device for injecting the liquefied gas fuel from the tank to the fuel injection device, a fuel return channel for returning the liquefied gas fuel from the fuel injection device side to the tank, and An engine control device for a hybrid vehicle comprising: an electrically controllable control valve provided in the fuel return path; and a motor that outputs power by receiving power supplied from an in-vehicle battery, wherein the liquefied gas fuel When the vehicle satisfies a predetermined condition, the hybrid vehicle travels only with the output of the motor when the engine is stopped. When the vehicle speed exceeds the first threshold during the EV traveling mode, the control valve is opened and the fuel pump is operated so that the liquefied gas fuel in the fuel supply path passes through the fuel return path to the tank. The fuel return control is executed to return to, and when the vehicle speed becomes equal to or higher than the second threshold value greater than the first threshold value in the EV travel mode, the control valve is closed and the fuel pump and the fuel injection device are operated. The engine is started.

  In the engine control apparatus for a hybrid vehicle according to the present invention, when the vehicle speed is equal to or higher than the first threshold and the fuel pump is allowed to drive, the fuel pump is driven when the vehicle speed is equal to or lower than a third threshold that is lower than the first threshold. It may be prohibited.

  In this case, the third threshold value may be changed to a larger value when there is a vehicle brake operation during the execution of the fuel return control.

  Further, in the engine control apparatus for a hybrid vehicle according to the present invention, when there is an accelerator operation of the vehicle during execution of the fuel return control, the first threshold value is changed to a small value when the accelerator opening is larger than a predetermined value. May be.

  In the engine control device for a hybrid vehicle according to the present invention, the fuel pump is driven prior to starting the engine when the driving sound of the fuel pump is less likely to be a problem and the vehicle speed is equal to or higher than a first threshold value at which an engine start request is likely to occur. The fuel return control is performed, and the engine is started when the fuel is further accelerated and exceeds the second threshold value. Therefore, even during EV running while the engine is stopped, the drive noise of the fuel pump is not easily generated by road noise or the like, and the liquefied gas fuel in the fuel supply path is not vaporized by the fuel return control before starting the engine. It becomes a state. Therefore, according to the present invention, the fuel injection amount at the time of engine start can be appropriately controlled without deteriorating the NV performance, and the engine can be started smoothly.

1 is a diagram schematically showing an overall configuration of a hybrid vehicle according to an embodiment of the present invention. It is a figure which shows roughly the engine system mounted in the hybrid vehicle of FIG. Fig. 3 is a flowchart showing a processing procedure of fuel return control executed in an engine ECU shown in Fig. 2. It is a flowchart which shows the process sequence of a fuel pump drive control routine. 2 is a flowchart showing a processing procedure of an engine start control routine executed in the hybrid ECU shown in FIG. 6 is a flowchart showing a modification of a fuel pump drive control routine executed in the engine ECU. It is a flowchart which shows the control which changes the 2nd threshold value used by a fuel pump drive control routine. It is a flowchart which shows the control which changes the 1st threshold value used by a fuel pump drive control routine.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings. In this description, specific shapes, materials, numerical values, directions, and the like are examples for facilitating the understanding of the present invention, and can be appropriately changed according to the application, purpose, specification, and the like. In addition, when a plurality of embodiments and modifications are included in the following, it is assumed from the beginning that these characteristic portions are used in appropriate combinations.

  In the following description, the hybrid vehicle on which the engine control device of the present embodiment is mounted will be described as one using two motors / generators having a motor function and a generator function. One motor having only a motor function and one motor having only a generator function may be used, or only one motor / generator may be used, or three or more motors / generators may be used.

  In the following description, the engine is described as an internal combustion engine using LPG (liquefied petroleum gas) as a fuel. However, the engine fuel is liquefied gas fuel other than LPG (for example, LNG (liquefied natural gas), hydrogen, etc.). ).

  FIG. 1 shows a schematic configuration of a hybrid vehicle 10 to which the engine control device of the present embodiment is applied. In FIG. 1, the power transmission system is illustrated as a round bar-shaped shaft element, the power system is illustrated by a solid line, and the signal system is illustrated by a broken line.

  As shown in FIG. 1, the hybrid vehicle 10 is connected to an engine 12 as a driving power source, a motor 14 (denoted as MG2 in the figure) as another driving power source, and an output shaft 16 of the engine 12. A motor 22 to which the rotary shaft 20 is connected via the power distribution mechanism 18 (denoted as MG1 in the figure), an in-vehicle battery 24 capable of supplying driving power to each of the motors 14 and 22, the engine 12 and A control unit 90 that controls each operation of the motors 14 and 22 and controls charging / discharging of the battery 24 is provided.

  Control unit 90 includes an engine ECU 92 and a hybrid ECU 94. The engine ECU 92 has a function of controlling the operation of the engine system including the engine 12. This engine system will be described later with reference to FIG. The hybrid ECU 94 corresponds to a host ECU of the engine ECU 92 and has a function of comprehensively controlling the operations of the motors 14 and 22 and the engine 12 of the hybrid vehicle 10. As will be described later, each of the ECUs 92 and 94 is preferably configured by a microcomputer, but may be configured by a single microcomputer. The control unit 90 corresponds to the engine control device in the present invention.

  The engine 12 is an internal combustion engine that uses LPG as fuel. Based on a command from the engine ECU 92 of the control unit 90, cracking, throttle opening, fuel injection amount, ignition timing, and the like are controlled to start the engine 12, Operation, stop, etc. are controlled.

  A crankshaft sensor 28 for detecting the engine speed Ne is provided in the vicinity of the output shaft 16 extending from the engine 12 to the power distribution mechanism 18. Further, the engine 12 is provided with a temperature sensor 13 that detects a temperature Tw of cooling water that is an engine cooling medium, and a knock sensor 17 that detects knocking of the engine 12. The detection signals from the crankshaft sensor 28, the temperature sensor 13, and the knock sensor 17 are transmitted to the control unit 90.

  The power distribution mechanism 18 can be suitably configured by, for example, a planetary gear mechanism. The power input from the engine 12 to the power distribution mechanism 18 via the output shaft 16 is transmitted to the drive wheels 34 via the transmission 30 and the axle 32 so that the vehicle 10 can travel with the engine power.

  The power distribution mechanism 18 can input a part or all of the power of the engine 12 input via the output shaft 16 to the motor 22 via the rotary shaft 20. The motor 22 is preferably configured by a three-phase synchronous AC motor, for example, and can function as a generator. The three-phase AC voltage generated by the motor 22 is converted into a DC voltage by the inverter 36 and charged in the battery 24 or used as a drive voltage for the motor 14.

  The motor 22 can also function as an electric motor that is rotationally driven by electric power supplied from the battery 24 via the converter 35 and the inverter 36. Power that is driven to rotate the motor 22 and is output to the rotating shaft 20 can be input to the engine 12 via the power distribution mechanism 18 and the output shaft 16 to perform cranking. Furthermore, the motor 22 can be used as driving power by rotating the motor 22 with electric power supplied from the battery 24 and outputting the power to the axle 32 via the power distribution mechanism 18 and the transmission 30.

  The motor 14 that mainly functions as an electric motor is preferably configured by, for example, a three-phase synchronous AC motor. The motor 14 is rotationally driven by the DC voltage supplied from the battery 24 being boosted by the converter 35 as necessary, and then converted into a three-phase AC voltage by the inverter 38 and applied as a drive voltage. The power that is output to the rotating shaft 15 by driving the motor 14 is transmitted to the drive wheels 34 via the transmission 30 and the axle 32, and so-called EV traveling is performed in a state where the engine 12 is stopped. The motor 14 also has a function of assisting engine output by outputting driving power when there is a sudden acceleration request by the driver's accelerator operation.

  The engine ECU 92 and the hybrid ECU 94 constituting the control unit 90 include a CPU for executing various control programs, a ROM for storing a control program and a control map in advance, a control program read from the ROM, and each sensor. It is preferably configured by a microcomputer comprising a RAM or the like that temporarily stores detection values and the like.

  The control unit 90 includes an engine speed Ne, a battery current Ib, a battery voltage Vb, a battery temperature Tb, a vehicle speed Sv, an accelerator opening signal Acc, a brake operation signal Br, an engine cooling water temperature Tw, an output voltage of the converter 35 or A system voltage that is an input voltage of the inverters 36 and 38, a motor current flowing through the motors 14 and 22, and the like are input. The control unit 90 outputs a control signal for controlling the operation or operation of the engine 12, the converter 35, the inverters 36, 38, and the like.

  Here, as shown in FIG. 2, the accelerator opening signal Acc is detected by an accelerator position sensor 80 provided on the accelerator pedal, and the brake operation signal Br is detected by a brake position sensor 82 provided on the brake pedal. Further, the vehicle speed Sv is input from, for example, a vehicle speed sensor (not shown) that detects the vehicle speed Sv based on the rotational speed of the axle 32. However, the vehicle speed Sv may be acquired by other methods. For example, when the vehicle 10 is running with the power of the engine 12 and power is not distributed to the motor 22, the calculation may be made based on the engine speed Ne, or the vehicle may be powered by the motor 14. May be calculated based on the rotational speed of the rotating shaft 15 of the motor 14.

  The hybrid ECU 94 of the control unit 90 calculates the required vehicle output based on the vehicle speed Sv and the accelerator opening signal Acc. In the hybrid vehicle 10 of the present embodiment, for example, when the vehicle speed Sv is a low speed region less than a predetermined threshold value and EV driving is possible with the power supplied from the battery 24, the motor 14 is stopped with the engine 12 stopped. EV can be driven only by the power of When the vehicle speed Sv becomes equal to or higher than the threshold value, the hybrid ECU 94 generates an engine start request and transmits it to the engine ECU 92.

  In response to the engine start request from the hybrid ECU 94, the engine ECU 92 performs cranking by the motor 22 to start the engine 12, and controls the engine speed Ne and torque to generate a vehicle request output. Control the operation.

  Next, the engine system 50 in the hybrid vehicle 10 of the present embodiment will be described with reference to FIG. As shown in FIG. 2, the engine system 50 includes a tank 52, a fuel pump 54, a fuel injection device 56, a fuel supply path 58, and a fuel return path 60 in addition to the engine 12 and the engine ECU 92 described with reference to FIG. And an electromagnetic valve (control valve) 62.

  The tank 52 is a container that stores LPG as fuel supplied to the engine 12. In the present embodiment, a fuel pump 54 that delivers LPG from the tank 52 is disposed in the tank 52. The operation of the fuel pump 54 is controlled according to a drive signal transmitted from the engine ECU 92. In addition, although this embodiment demonstrates the example which provides the fuel pump 54 in the tank 52, it is not limited to this. For example, the fuel pump 54 may be disposed in a fuel supply path 58 outside the tank.

  The fuel supply path 58 is a pipe line for supplying the LPG delivered from the tank 52 by the fuel pump 54 to the fuel injection device 56. One end of the fuel supply path 58 passes through the wall of the tank 52 in an airtight manner and is connected to the fuel pump 54, and the other end is connected to the fuel injection device 56.

  The fuel injection device 56 is an injector that injects LPG toward the intake pipe 64 connected to the cylinder head of the engine 12. The fuel injection device 56 includes a valve body (not shown), and the opening degree, opening timing, opening time, etc. of the valve body are controlled in accordance with a control signal from the engine ECU 92, whereby the LPG injection amount and injection timing are controlled. It has come to be adjusted.

  In the present embodiment, the LPG injected from the fuel injection device 56 is indirectly injected toward the engine 12 via the intake pipe 64. However, the present invention is not limited to this, and the fuel injection device is not limited thereto. The LPG from 56 may be directly injected into the cylinder of the engine 12.

  The fuel return path 60 is a pipe line for returning the LPG from the fuel injection device 56 side to the tank. One end of the fuel return path 60 is connected to the fuel injection device 56, and the other end is connected to the tank 52. However, the fuel return path 60 may be configured such that one end portion branches from the fuel supply path 58 at a position near the fuel injection device 56 and is connected to the tank 52.

  An electromagnetic valve 62 is provided in the fuel return path 60. The electromagnetic valve 62 is an electrically controllable control valve that is controlled to open and close in accordance with a drive signal from the engine ECU 92. The solenoid valve 62 is opened in response to a command from the engine ECU 92 when fuel return control is executed as described later, and is closed in other cases.

  Further, the fuel return path 60 is provided with a fuel temperature sensor 66 for detecting the temperature of the LPG as fuel, and a fuel pressure sensor 68 for detecting the pressure of the LPG. Detection signals from the fuel temperature sensor 66 and the fuel pressure sensor 68 are input to the engine ECU 92 and used for fuel return control described later. In the present embodiment, the fuel temperature sensor 66 and the fuel pressure sensor 68 are provided in the fuel return path 60. However, instead of or in addition to this, the fuel temperature sensor and the fuel pressure sensor may be provided in the fuel supply path 58. Good.

  A fuel temperature sensor 84 and a fuel pressure sensor 86 for detecting the temperature and pressure of the LPG in the tank are provided at the bottom of the tank 52. Detection signals from these sensors 84 and 86 are input to the engine ECU 92 and used for monitoring the fuel state in the tank 52.

  An intake valve 65 is provided in the cylinder head 12 a of the engine 12, and an intake pipe 64 is connected to the installation position of the intake valve 65. The intake valve 65 is driven to open and close in response to a control signal from the engine ECU 92. Thus, the LPG injected from the fuel injection device 56 is mixed with the air taken in from the outside of the vehicle via the air cleaner 70 and the throttle valve 72 and is sucked into the cylinder of the engine 12.

  Further, an exhaust valve 67 is provided in the cylinder head of the engine 12, and an exhaust pipe 74 is connected to an installation position of the exhaust valve 67. The exhaust valve 67 is driven to open and close in response to a control signal from the engine ECU 92. As a result, the exhaust gas generated by the combustion of the LPG mixture in the cylinder of the engine 12 is exhausted through the exhaust pipe 74. The exhaust pipe 74 is provided with a catalyst 76 such as a three-way catalyst. Therefore, the exhaust gas exhausted from the engine 12 is released outside the vehicle after hydrocarbons and the like are removed by the catalyst 76.

  Next, the fuel return control executed by the engine ECU 92 will be described with reference to FIG. FIG. 3 is a flowchart showing a processing procedure of fuel return control executed in engine ECU 92 shown in FIG. This fuel return control routine is repeatedly executed in the EV travel mode in which the hybrid vehicle 10 travels only with motor power.

  Referring to FIG. 3, engine ECU 92 first acquires vehicle information in step S10. This vehicle information includes the engine speed Ne, the fuel temperature and fuel pressure of the LPG detected by the fuel temperature sensor 66 and the fuel pressure sensor 68, and the like.

  Next, the engine ECU 92 determines in step S12 whether or not the engine 12 is stopped. In this determination, for example, it may be confirmed that the engine speed Ne is zero, or it may be confirmed that a control signal for operating the fuel injection device 56 is not generated. Here, it is confirmed that the engine 12 is in a stopped state by operating the engine 12 and generating power by the motor 22 even during EV traveling, and charging the battery 24 and driving the motor 14 with the generated power. It is because there are times when it is done.

  When it is determined in step S12 that the engine is operating (NO in S12), the process is terminated without performing fuel return control. On the other hand, when it is determined in step S12 that the engine is stopped (YES in S12), the engine ECU 92 determines in step S14 whether the LPG as the fuel is hot.

  Specifically, the determination is made based on whether or not the LPG temperature in the fuel return path 60 detected by the fuel temperature sensor 66 is equal to or higher than a predetermined value. This predetermined value can be stored in advance in the engine ECU 92 as a temperature obtained by experiment, simulation, or the like as a temperature at which LPG as liquefied gas fuel is highly likely to vaporize in the fuel supply path 58. Here, in the present embodiment, it is determined whether or not the fuel is hot based on the LPG temperature detected in the fuel return path 60. However, the fuel supply path 58 and the fuel return path 60 are determined by heat transfer from the engine 12 or the like. Is heated approximately equally, so that the LPG temperature in the fuel return path 60 can be regarded as being substantially equal to the LPG temperature in the fuel supply path 58.

  In the present embodiment, the vaporization of the liquefied gas fuel in the fuel supply path 58 is determined based only on the LPG temperature, but it is also considered whether the fuel pressure detected by the fuel pressure sensor 68 is a predetermined value or more. May be. Then, the fuel vaporization state in the fuel supply path 58 can be estimated more accurately. As for the predetermined value, which is a criterion for determining the fuel pressure, a value obtained by experiment, simulation, or the like can be stored in the engine ECU 92 in advance. Further, the fuel vaporization state in the fuel supply path 58 may be determined only by the fuel pressure.

  When it is determined in step S14 that the LPG is not high temperature (NO in step S14), the process is terminated as it is without executing the fuel return control. On the other hand, when it is determined in step S14 that the LPG temperature is high (YES in step S14), it is determined in step S16 whether the fuel pump 54 is permitted to be driven. This determination is set by a fuel pump drive control routine executed in the hybrid ECU 94 separately from this control routine. This will be described later with reference to FIG.

  If it is determined in step S16 that driving of the fuel pump 54 is prohibited (NO in step S16), the process is terminated without executing the fuel return control. On the other hand, if it is determined in step S16 that driving of the fuel pump 54 is permitted (YES in step S16), the engine ECU 92 opens the electromagnetic valve 62 and drives the fuel pump 54 in subsequent step S18. To do. Thus, fuel return control is performed in which the LPG in the fuel supply path 58 is returned to the tank 52 via the fuel injection device 56 and the fuel return path 60. As a result, the LPG temperature in the fuel supply path 58 is lowered by replacing the LPG in the fuel supply path 58 with the LPG sent out from the tank 52.

  In step S20, engine ECU 92 determines whether or not the LPG temperature has decreased. Here, it is confirmed whether or not the LPG temperature detected by the fuel temperature sensor 66 is lower than the predetermined value, and the open state of the electromagnetic valve 62 and the driving of the fuel pump 54 are continued until the LPG temperature becomes lower than the predetermined value. To do. If it is determined that the LPG temperature has become lower than the predetermined value (YES in step S20), engine ECU 92 closes electromagnetic valve 62 and stops driving fuel pump 54 in subsequent step S22.

  Thus, by executing the fuel return control when the LPG temperature is high, the LPG temperature in the fuel supply path 58 can be lowered to eliminate the fuel vaporization state. As a result, an appropriate amount of fuel can be injected in advance by the fuel injection device 56 at the time of subsequent engine start, and the engine can be started smoothly and stably.

  Next, a fuel pump drive control routine executed by the hybrid ECU 94 will be described with reference to FIG.

  As shown in FIG. 4, first, in step S30, the hybrid ECU 94 determines whether or not the hybrid vehicle 10 is in an EV travel mode in which the vehicle travels only with a motor output while the engine is stopped. Here, if it is determined that the vehicle is not in the EV travel mode (NO in step S30), the process is terminated as it is. On the other hand, if it is determined that the vehicle is in the EV travel mode (YES in step S30), hybrid ECU 94 determines in step S32 whether vehicle speed Sv is equal to or higher than first threshold value V1.

  If it is determined in step S32 that the vehicle speed Sv has become equal to or higher than the first threshold value V1 (YES in step S32), the drive of the fuel pump 54 is permitted in the subsequent step S34, and a drive permission signal is sent to the engine ECU 92 in the subsequent step S38. Send. Upon receiving this drive permission signal, the engine ECU 92 can make a positive determination in step S16 as described above, and drive the fuel pump 54 to execute fuel return control.

  On the other hand, when it is determined that the vehicle speed Sv is less than the first threshold value V1 (NO in step S32), the hybrid ECU 94 prohibits driving of the fuel pump 54 in step S36, and in the subsequent step S38, sends a drive prohibition signal to the engine ECU 92. Send to. Upon receiving this drive inhibition signal, the engine ECU 92 makes a negative determination in step S16 and does not perform fuel return control.

  Here, the first threshold value V1 is a vehicle speed region in which an engine start request is likely to occur, and even if the fuel pump 54 is driven when the vehicle is running in an EV stopped state, the fuel pump is caused by road noise or the like. The drive sound 54 is preset to a vehicle speed at which it is difficult for the driver to feel noise, and is stored in the hybrid ECU 94. The first threshold value V1 can be set to 40 km / h, for example.

  In this way, when the vehicle speed Sv becomes equal to or higher than the first threshold value V1 during EV traveling with the engine stopped, the fuel pump 54 is driven and fuel return control is performed, so that the NV performance of the vehicle is not deteriorated. The fuel injection amount at the start can be appropriately controlled.

  The fuel pump drive control routine shown in FIG. 4 has been described as being executed by the hybrid ECU 94, but is not limited to this and may be executed by the engine ECU 92. In this case, the transmission process to the engine ECU 92 in step S38 is omitted.

  Next, an engine start control routine executed in the hybrid ECU 94 will be described with reference to FIG.

  First, in step S40, the hybrid ECU 94 determines whether or not the hybrid vehicle 10 is in the EV traveling mode with the engine stopped. This determination is the same as step S30 in the fuel pump drive control routine described above.

  If it is determined in step S40 that the vehicle is not in the EV travel mode (NO in step S40), the process is terminated as it is. On the other hand, if it is determined in step S40 that the vehicle is in the EV travel mode (YES in step S40), it is determined in subsequent step S42 whether the vehicle speed Sv is equal to or higher than the second threshold value V2. Here, the second threshold value V2 is preset as a value larger than the first threshold value V1, and is stored in the hybrid ECU 94. The second threshold value V2 can be set at, for example, 50 km / h.

  If it is determined in step S42 that the vehicle speed Sv is less than the second threshold value V2 (NO in step S42), the process is terminated as it is. On the other hand, when it is determined that the vehicle speed Sv is equal to or higher than the second threshold value V2 (YES in step S42), an engine start request is generated in the subsequent step S44.

  In response to this engine start request, the engine ECU 92 operates the fuel pump 54, the fuel injection device 56, the ignition coil 78, the intake valve 65, the exhaust valve 67, etc. and performs cranking with the motor 22, thereby 12 is started. Thereafter, the hybrid vehicle 10 shifts to an engine travel mode in which the vehicle travels with engine power.

  As described above, according to the hybrid vehicle 10 of the present embodiment, the engine starts when the drive sound of the fuel pump 54 is less likely to be a problem and the vehicle speed Sv is equal to or higher than the first threshold value V1 at which an engine start request is likely to occur. In advance, the fuel pump 54 is driven to perform fuel return control, and the engine is started when the fuel pump 54 is further accelerated and becomes equal to or higher than the second threshold value V2. As a result, even in the EV traveling mode when the engine is stopped, the driving sound of the fuel pump 54 is hardly generated by road noise or the like, and the LPG in the fuel supply path 58 is not vaporized by the fuel return control before starting the engine. It becomes a state. Therefore, according to the present embodiment, the fuel injection amount at the time of starting the engine can be appropriately controlled without deteriorating the NV performance. As a result, it is possible to smoothly start the engine without a feeling of stagnation, and to suppress deterioration in drivability of the vehicle.

  Next, a modification of the fuel pump drive control routine will be described with reference to FIG. In this modification, only the step S46 is different from that described above with reference to FIG. 4, and the other processes are the same. Therefore, the difference will be mainly described here.

  As shown in FIG. 6, when the vehicle speed Sv is equal to or higher than the first threshold value V1 and the drive of the fuel pump 54 is permitted in step S32, the vehicle speed Sv reaches the first threshold value V1 even if the fuel return control routine is repeatedly executed. As long as it exceeds the upper limit, the drive permission state of the fuel pump 54 is continued.

  On the other hand, when the vehicle decelerates and the vehicle speed Sv becomes less than the first threshold value V1 (NO in step S32), in the subsequent step S46, it is determined whether or not the vehicle speed Sv is equal to or less than the third threshold value V3. Here, the third threshold value V3 can be set in advance to a value smaller than the first threshold value V1, and can be stored in the hybrid ECU 94. The third threshold value V3 can be set at, for example, 30 km / h. If it is determined that the vehicle speed Sv has become equal to or lower than the third threshold value V3, the drive of the fuel pump 54 is prohibited in the subsequent step S36. In response to this drive prohibition, the engine ECU 92 stops the fuel pump 54.

  Thus, by setting the third threshold value, which is the determination criterion V3 for prohibiting driving, to be smaller than the first threshold value V1, which is the criterion for permitting driving of the fuel pump 54, hunting between operation and stop of the fuel pump 54 is performed. Can be prevented.

  Next, the threshold value change control routine (1) executed by the hybrid ECU 94 will be described with reference to FIG. FIG. 7 is a flowchart showing control for changing the third threshold value V3 used in the fuel pump drive control described with reference to FIG. This threshold value change control routine (1) is repeatedly executed while the fuel pump drive control routine shown in FIG. 6 is being executed.

  Referring to FIG. 7, the hybrid ECU 94 determines whether or not there is a brake operation in step S50. Here, the presence or absence of a brake operation can be determined based on a brake operation signal Br input to the control unit 90.

  If it is determined in step S50 that there is no brake operation (NO in step S50), the process is terminated without changing the second threshold value V2. On the other hand, if it is determined that there is a brake operation (YES in step S50), in the subsequent step S52, the third threshold value V3 is changed to a larger value. For example, when there is a brake operation, the third threshold value V3 is changed from 30 km / h to 35 km / h. Note that after the driving of the fuel pump 54 is stopped, the third threshold value V3 can be returned to the normal value (here, 30 km / h).

  Since the vehicle is expected to decelerate and stop when there is a brake operation as described above, the fuel pump 54 can be made earlier by changing the third threshold value V3 to a larger value to make the fuel pump 54 stop earlier. It is possible to reliably prevent the operation sound 54 from being felt as noise.

  Next, the threshold value change control routine (2) will be described with reference to FIG. FIG. 8 is a flowchart showing the control for changing the first threshold value V1 used in the fuel pump drive control routine described with reference to FIGS. 4 and 6. This threshold value change control routine (2) is repeatedly executed while the fuel pump drive control routine is being executed.

  Referring to FIG. 8, the hybrid ECU 94 determines whether or not there is an accelerator operation in step S60. Here, the presence / absence of the accelerator operation and the accelerator opening can be determined based on the accelerator opening signal Acc input to the control unit 90.

  If it is determined in step S60 that there is no accelerator operation (NO in step S60), the process is terminated without changing the threshold value. On the other hand, if it is determined that there is an accelerator operation (YES in step S60), it is determined in subsequent step S62 whether the accelerator opening is larger than a predetermined value.

  If it is determined in step S62 that the accelerator opening is equal to or smaller than the predetermined value (NO in step S62), it can be determined that the acceleration request of the vehicle is small, and thus the process is performed without changing the first threshold value V1. finish. On the other hand, if it is determined that the accelerator opening is larger than the predetermined value (YES in step S62), the first threshold value V1 is changed to a smaller value in the subsequent step S64. For example, when the accelerator opening is larger than a predetermined value, the first threshold value V1 is changed from 40 km / h to 35 km / h. In addition, after the drive of the fuel pump 54 is started, the first threshold value V1 can be returned to the normal value (here, 40 km / h).

  As described above, when the accelerator opening signal Acc is larger than the predetermined value, the vehicle is requested to accelerate rapidly, and the vehicle speed Sv rises quickly. Therefore, in this case, by changing the first threshold value V1 to a small value and making the timing for permitting the drive of the fuel pump 54 earlier, it is possible to secure the time for performing the fuel return control in preparation for the engine start. It becomes possible. In this case, since the time interval from the start of driving of the fuel pump 54 to the start of the engine is shortened, even if the fuel pump 54 is started earlier, the NV performance of the vehicle is not significantly deteriorated. The impact on usability is small.

  The present invention is not limited to the configuration of the above-described embodiment and its modifications, and various modifications and improvements can be made within the matters described in the claims of the present application and the equivalent scope thereof. Of course there is.

  DESCRIPTION OF SYMBOLS 10 Hybrid vehicle, 12 Engine, 12a Cylinder head, 13 Temperature sensor, 14, 22 Motor, 15, 20 Rotating shaft, 16 Output shaft, 17 Knock sensor, 18 Power distribution mechanism, 24 Battery, 28 Crankshaft sensor, 30 Transmission , 32 axles, 34 drive wheels, 35 converters, 36, 38 inverters, 50 engine systems, 52 tanks, 54 fuel pumps, 56 fuel injection devices, 58 fuel supply passages, 60 fuel return passages, 62 solenoid valves (control valves), 64 Intake pipe, 65 Intake valve, 66, 84 Fuel temperature sensor, 67 Exhaust valve, 68, 86 Fuel pressure sensor, 70 Air cleaner, 72 Throttle valve, 74 Exhaust pipe, 76 Catalyst, 78 Ignition coil, 80 Accelerator position sensor, 82 brake Position sensor, 90 control unit (engine control device), 92 engine ECU, 94 hybrid ECU, Acc accelerator opening signal, Br brake operation signal, Ib battery current, Ne engine speed, Sv vehicle speed, Tb battery temperature, Tw water temperature, V1 first threshold, V2 second threshold, V3 third threshold, Vb battery voltage.

Claims (4)

An engine that uses liquefied gas fuel, a tank that stores the liquefied gas fuel, a fuel pump that delivers the liquefied gas fuel from the tank, a fuel injection device that injects the liquefied gas fuel toward the engine, and the liquefied gas fuel A fuel supply path for supplying fuel from the tank to the fuel injection device, a fuel return path for returning the liquefied gas fuel from the fuel injection device side to the tank, and electrically provided in the fuel return path A controllable control valve;
An engine control device for a hybrid vehicle comprising: a motor that receives power supply from an in-vehicle battery and outputs power;
When the liquefied gas fuel satisfies a predetermined condition, the control valve is opened when the vehicle speed becomes equal to or higher than a first threshold during the EV travel mode in which the hybrid vehicle travels only with the output of the motor while the engine is stopped. A fuel return control is performed to return the liquefied gas fuel in the fuel supply path to the tank via the fuel return path by operating the fuel pump in a state;
When the vehicle speed is equal to or higher than a second threshold value greater than the first threshold value in the EV travel mode, the control valve is closed and the fuel pump and the fuel injection device are operated to start the engine;
An engine control device for a hybrid vehicle. The engine control apparatus for a hybrid vehicle according to claim 1,
An engine control apparatus for a hybrid vehicle that permits driving of the fuel pump when the vehicle speed is equal to or higher than the first threshold, and prohibits driving of the fuel pump when the vehicle speed is equal to or lower than a third threshold that is lower than the first threshold. The engine control apparatus for a hybrid vehicle according to claim 2,
An engine control apparatus for a hybrid vehicle that changes the third threshold value to a larger value when a vehicle brake operation is performed during execution of the fuel return control. In the engine control device for a hybrid vehicle according to any one of claims 1 to 3,
An engine control apparatus for a hybrid vehicle that changes the first threshold value to a smaller value when the accelerator opening is larger than a predetermined value when the accelerator operation of the vehicle is performed during execution of the fuel return control.

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