JP6443306B2 - Fuel supply apparatus and control method - Google Patents

Description

  The present invention relates to a technique for supplying liquefied gas fuel from a fuel tank to an internal combustion engine.

  Conventionally, as disclosed in, for example, Patent Document 1, dimethyl ether (DME), which is a kind of liquefied gas fuel, is heated by an internal combustion engine and remains in a high-pressure gas if it remains in the common rail after the internal combustion engine is stopped. And can leak into the combustion chamber. DME leaking into the combustion chamber can cause abnormal combustion when the internal combustion engine is started.

  Therefore, the fuel supply device of Patent Document 1 once collects DME remaining in the common rail by using a purge tank whose pressure is lower than that of the fuel tank. The DME vaporized in the purge tank is reliquefied by the compressor and transferred to the fuel tank. By such an operation, DME in the common rail is recovered to the fuel tank.

JP 2005-30327 A

  However, in the configuration disclosed in Patent Document 1, a compressor that liquefies the vaporized fuel again and transfers it to the fuel tank is essential. Therefore, the configuration of the fuel supply device has to be complicated. Therefore, a technique capable of recovering liquefied gas fuel without using a configuration such as a compressor has been desired.

  The present invention has been made in view of such problems, and its object is to provide a fuel supply device capable of recovering liquefied gas fuel in a common rail to a fuel tank while avoiding complication of the configuration. Is to provide.

  In order to achieve the above object, one disclosed invention is that a part of the liquefied gas fuel supplied from the fuel tank (190) to the common rail (30) of the internal combustion engine (110) is returned to the return fuel path (85). The fuel supply device is recirculated to the fuel tank through the inflow portion (90) provided in the return fuel path, into which the liquefied gas fuel flows through the return fuel path, and the liquefied gas fuel from the common rail to the inflow portion. A first control valve (71) for controlling the flow, a second control valve (89) for controlling the flow of the liquefied gas fuel from the inflow portion to the fuel tank, and the second control valve is closed after the internal combustion engine is stopped. The first control valve is opened while the liquefied gas fuel in the common rail is moved to the inflow portion, and the second control valve is opened while the first control valve is closed, Flow in the first transfer state A valve control unit for repeatedly liquefied gas fuel has moved to the parts alternately and a second transfer state to move to a fuel tank (61), and a.

  In the first transfer state of the present invention, the liquefied gas fuel in the common rail moves to the inflow portion by opening the first control valve while closing the second control valve. Such movement can be stopped by reducing the pressure difference between the common rail and the inflow portion as the temperature in the inflow portion increases due to the liquefied gas fuel that has flowed in.

  And if it is made into the 2nd transfer state, the liquefied gas fuel which moved to the inflow part in the 1st transfer state will move to a fuel tank. As a result, the liquefied gas fuel is vaporized in the inflow portion, and the temperature in the inflow portion and thus the pressure is reduced. Therefore, when the first movement state is set again, the liquefied gas fuel in the common rail can move to the inflow portion.

  As described above, according to the repetition of the first transfer state and the second transfer state, it is possible to recover the liquefied gas fuel in the common rail to the fuel tank while avoiding complication of the configuration.

  In another disclosed invention, the common rail, the inflow portion, and the pressure acquisition unit (62) for acquiring each pressure (Pc, Ps, Pm) of the fuel tank are further provided, and the valve control unit includes the common rail. Switching from the first transfer state to the second transfer state based on the pressure difference between the inlet and the inflow part, and switching from the second transfer state to the first transfer state based on the pressure difference between the inflow part and the fuel tank It is characterized by.

  Furthermore, in another disclosed invention, a part of the liquefied gas fuel supplied from the fuel tank (190) to the common rail (30) of the internal combustion engine (110) is passed through the return fuel path (85). The first control valve (71) for controlling the flow of the liquefied gas fuel from the common rail to the inflow portion (90) provided in the return fuel path, and A control method for controlling the second control valve (89) for controlling the flow of the liquefied gas fuel by the processor (85), and after stopping the internal combustion engine, the pressures (Pc, Ps) of the common rail and the inflow portion are controlled. Based on the difference between the first pressure acquisition step (S103, S203) to be acquired and each pressure acquired in the first pressure acquisition step, the first control valve is opened while the second control valve is closed. From the first transfer state in which the liquefied gas fuel in the rail is moved to the inflow portion, the second control valve is opened while the first control valve is closed, and the liquefied gas fuel moved to the inflow portion is moved to the fuel tank. A first switching step (S104 to S106, S204 to S206) for switching to the second transfer state, and a second pressure for acquiring each pressure (Ps, Pm) of the inflow portion and the fuel tank after switching to the second transfer state. A second switching step (S108 to S110, S208 to S210) for switching from the second transfer state to the first transfer state based on the difference between the pressures acquired in the acquisition step (S107, S207) and the second pressure acquisition step. And.

  In these inventions, switching from the first transfer state to the second transfer state is performed based on the pressure difference between the common rail and the inflow portion. Therefore, the first transfer state can be appropriately terminated at a timing at which the movement of the liquefied gas fuel from the common rail to the inflow portion becomes difficult due to the decrease in the pressure difference. Similarly, switching from the second transfer state to the first transfer state is performed based on the pressure difference between the inflow portion and the fuel tank. Therefore, the second transfer state can be appropriately terminated at a timing at which the movement of the liquefied gas fuel from the inflow portion to the fuel tank becomes difficult due to the decrease in the pressure difference.

  Note that the reference numbers in the parentheses are merely examples of correspondences with specific configurations in the embodiments to be described later in order to facilitate understanding of the present invention, and limit the scope of the present invention. It is not a thing.

It is a figure showing the whole fuel supply device composition by a first embodiment of the present invention. It is a longitudinal cross-sectional view which shows the structure of a supply pump. It is a figure which shows the functional block of a control apparatus. It is a figure which shows the saturated vapor pressure line of DME fuel. It is a flowchart which shows the process implemented by the processor of a control apparatus. 3 is a time chart schematically showing changes in pressures and temperatures of a common rail, a sub fuel tank, and a main fuel tank after the internal combustion engine is stopped. It is a flowchart which shows the modification of FIG. It is a time chart which shows typically transition of each pressure and each temperature of a common rail, a sub fuel tank, and a main fuel tank when processing of Drawing 7 is carried out.

  Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings. In addition, the overlapping description may be abbreviate | omitted by attaching | subjecting the same code | symbol to the corresponding component in each embodiment. When only a part of the configuration is described in each embodiment, the configuration of the other embodiment described above can be applied to the other part of the configuration. Moreover, not only the combination of the configurations explicitly described in the description of each embodiment, but also the configuration of a plurality of embodiments can be partially combined even if they are not explicitly described, as long as there is no problem in the combination. And the combination where the structure described in several embodiment and the modification is not specified shall also be disclosed by the following description.

(First embodiment)
A fuel supply device 100 shown in FIG. 1 is mounted on a vehicle together with a main fuel tank 190 and an internal combustion engine 110. The fuel supply device 100 supplies the liquefied gas fuel stored in the main fuel tank 190 to the internal combustion engine 110. A part of the DME fuel supplied to the internal combustion engine 110 is returned to the main fuel tank 190.

  The main fuel tank 190 stores dimethyl ether (DME) which is a kind of liquefied gas fuel. The DME fuel in the main fuel tank 190 is liquefied by being pressurized at a pressure corresponding to the fuel vapor pressure. The main fuel tank 190 is provided with a safety valve. The safety valve opens when the pressure in the main fuel tank 190 exceeds a predetermined upper limit pressure. The upper limit pressure is set to about 1.8 MPa, for example.

  The internal combustion engine 110 is stored in an engine room 120 of the vehicle. The internal combustion engine 110 is specifically a diesel engine, and compresses the DME fuel injected from the injector 40 disposed in each cylinder in each cylinder. The internal combustion engine 110 converts thermal energy of DME fuel combusted by compression in each combustion chamber 111 into power.

  The internal combustion engine 110 includes a cell motor 112, a supply pump 20, a common rail 30, and an injector 40. The cell motor 112 is an electric motor for starting the internal combustion engine 110. The cell motor 112 can transmit power to the output shaft of the internal combustion engine 110 to rotate the output shaft.

  The supply pump 20 shown in FIGS. 1 and 2 is a plunger pump that pumps DME fuel by a plunger 23 that reciprocates. The supply pump 20 is connected to the common rail 30 by a high-pressure line 21. The supply pump 20 is driven by the output shaft of the internal combustion engine 110. The supply pump 20 further pressurizes the DME fuel supplied from the fuel supply device 100 and supplies the pressurized DME fuel to the common rail 30 through the high-pressure line 21.

  The supply pump 20 includes a pump body 22, a delivery valve 25, an overflow valve 27, and the like in addition to the plunger 23 described above. The pump body 22 is formed with a pump fuel passage 22e including a fuel gallery 22a and a discharge passage 22c, a plunger accommodating chamber 22b, and the like. The fuel gallery 22a is a section for supplying DME fuel to the plunger accommodating chamber 22b in the pump fuel flow path 22e. The fuel gallery 22a is formed in an annular shape surrounding the plunger housing chamber 22b. The plunger accommodating chamber 22b accommodates the plunger 23 so as to be capable of reciprocating displacement. A part of the plunger housing chamber 22 b is a pressurizing chamber 22 d that compresses DME fuel by the displacement of the plunger 23. The discharge flow path 22 c is a fuel flow path that allows the high-pressure DME fuel pressurized in the pressurizing chamber 22 d to flow to the high-pressure line 21.

  The delivery valve 25 is assembled to the pump body 22 and forms the discharge part 24 of the supply pump 20. The delivery valve 25 includes a discharge valve body 25a, a discharge valve portion 25b, and a spring 25c. The discharge valve body 25 a is formed in a bolt shape and is screwed into the pump body 22. A fuel flow path 25d is formed in the discharge valve body 25a along the axial direction. The fuel flow path 25d allows the discharge flow path 22c and the high-pressure line 21 to communicate with each other.

  The discharge valve part 25b and the spring 25c are accommodated in the discharge valve body 25a. The discharge valve portion 25b can reciprocate in the fuel flow path 25d along the axial direction of the discharge valve body 25a. When the pressure of the DME fuel acting from the pressurizing chamber 22d side is low, the discharge valve portion 25b is urged by the spring 25c to block the communication of the fuel flow path 25d. Then, when the discharge of the DME fuel from the pressurizing chamber 22d is started by the operation of the supply pump 20, the discharge valve portion 25b is opened by the pressure of the pumped DME fuel, and the DME fuel toward the common rail 30 is opened. Allow discharge.

  Here, the pressure of the DME fuel in the fuel gallery 22a immediately after the internal combustion engine 110 is stopped is referred to as a gallery pressure Pga. Further, the pressure of the DME fuel in the main fuel tank 190 is set as the main tank pressure Pm. The valve opening pressure Pdo of the discharge valve section 25b is set higher than the differential pressure between the gallery pressure Pga and the main tank pressure Pm (Pdo> Pga−Pm).

  Specifically, the gallery pressure Pga assumed when the internal combustion engine 110 is stopped is, for example, the saturated vapor pressure (about 2.0 MPa) of the DME fuel when the fuel temperature is about 70 degrees Celsius. On the other hand, the main tank pressure Pm is, for example, the saturated vapor pressure (about 0.7 MPa) of DME fuel when the fuel temperature is about 30 ° C. Therefore, the valve opening pressure Pdo of the discharge valve portion 25b is set higher than these differential pressures of about 1.3 MPa, specifically, about 1.5 MPa.

  The overflow valve 27 is assembled to the pump body 22 and forms an excess fuel discharge part 26 of the supply pump 20. The overflow valve 27 has a pressure regulating valve body 27a, a pressure regulating valve portion 27b, and a spring 27c. The pressure regulating valve body 27 a is formed in a bolt shape and is screwed into the pump body 22. A fuel passage 27d is formed in the pressure regulating valve body 27a along the axial direction. The fuel flow path 27d allows the fuel gallery 22a to communicate with an overflow line 87 described later.

  The pressure regulating valve portion 27b and the spring 27c are accommodated in the pressure regulating valve body 27a. The pressure regulating valve portion 27b can reciprocate in the fuel flow path 27d along the axial direction of the pressure regulating valve body 27a. The pressure regulating valve portion 27b is closed by the urging force of the spring 27c and regulates the maximum pressure of the fuel gallery 22a. The pressure regulating valve portion 27b opens when the pressure of the fuel gallery 22a increases, and allows the DME fuel to be discharged from the fuel gallery 22a to the overflow line 87. The valve opening pressure Pro of the pressure regulating valve portion 27b is set higher than the saturated vapor pressure of the DME fuel in the fuel gallery 22a, and specifically, is set to about 2.0 MPa. The valve opening pressure Pro of the pressure regulating valve portion 27b is set to be approximately equal to the valve opening pressure Pdo of the discharge valve portion 25b or higher than the valve opening pressure Pdo of the discharge valve portion 25b.

  The common rail 30 shown in FIG. 1 is a tubular member formed of a metal material such as a steel material. The common rail 30 accumulates the DME fuel pressurized by the supply pump 20 while maintaining the pressure. The common rail 30 can store, for example, about 30 cc of DME fuel. The common rail 30 is connected to each injector 40 by a distribution line 31. The common rail 30 supplies DME fuel to each injector 40 through each distribution line 31.

  The injector 40 supplies the DME fuel supplied from the common rail 30 into each cylinder of the internal combustion engine 110. The injector 40 is inserted into a through hole formed in the head portion of the internal combustion engine 110, thereby exposing the injection hole in the combustion chamber 111. The injector 40 injects DME fuel from the injection hole exposed in the combustion chamber 111 based on the input control signal.

  Next, the configuration of the fuel supply device 100 will be described. The fuel supply device 100 includes a fuel line 80, a feed pump 10, a sub fuel tank 90, sensors 73 to 78, a pressure reducing valve 71, a supply cutoff valve 82, a reflux cutoff valve 89, a control device 50, and the like.

  The fuel line 80 is a pipe through which DME fuel flows between the main fuel tank 190 and the internal combustion engine 110. The fuel line 80 is formed by a metal pipe member, for example. The fuel line 80 includes a supply line 81, a return fuel line 85, an injector leak line 86, and an overflow line 87.

  The supply line 81 is a pipe that connects the main fuel tank 190 and the supply pump 20. The supply line 81 forms a fuel flow path for supplying DME fuel from the feed pump 10 to the supply pump 20. The return fuel line 85 is a pipe that connects the common rail 30 and the main fuel tank 190. The return fuel line 85 forms a fuel flow path for returning surplus fuel discharged from the common rail 30 to the main fuel tank 190.

  The injector leak line 86 is a pipe connecting each injector 40 and the return fuel line 85. The injector leak line 86 forms a fuel flow path that joins the leaked fuel discharged without being injected by each injector 40 to the DME fuel flowing through the return fuel line 85. The overflow line 87 is a pipe connecting the overflow fuel discharge port of the supply pump 20 and the main fuel tank 190. The overflow line 87 forms a fuel flow path for returning the overflow fuel discharged from the supply pump 20 to the main fuel tank 190.

  The feed pump 10 is an electric pump disposed inside the main fuel tank 190. The feed pump 10 sucks in the DME fuel stored in the main fuel tank 190 using the power of the electric motor. The feed pump 10 adds a feed pressure (for example, 1 to 2 MPa) to the DME fuel to increase the pressure, and feeds it to the supply pump 20 through the supply line 81.

  The sub fuel tank 90 is a container provided in the return fuel line 85. The sub fuel tank 90 has a capacity of, for example, about 100 cc, and is larger than the capacity of the common rail 30. On the other hand, the capacity of the sub fuel tank 90 is much smaller than the capacity of the main fuel tank 190. DME fuel discharged from the common rail 30 and flowing through the return fuel line 85 flows into the sub fuel tank 90. The sub fuel tank 90 is provided at a position higher than the main fuel tank 190 in the vehicle. The sub fuel tank 90 is disposed away from the engine room 120 of the vehicle so that it is not easily affected by the heat of the internal combustion engine 110.

  For convenience, in the return fuel line 85, the common rail 30 to the sub fuel tank 90 are defined as a first section 85a, and the sub fuel tank 90 to the main fuel tank 190 are defined as a second section 85b. The first section 85 a is connected to the ceiling wall of the sub fuel tank 90. The second section 85 b is connected to the bottom wall of the sub fuel tank 90.

  The rail pressure sensor 73 and the rail temperature sensor 74 are attached to the end of the common rail 30 in an integrated form. The sub tank pressure sensor 75 and the sub tank temperature sensor 76 are attached to the wall portion of the sub fuel tank 90. The main tank pressure sensor 77 and the main tank temperature sensor 78 are attached to the main fuel tank 190. Each sensor 73 to 78 is electrically connected to the control device 50.

  Each of the pressure sensors 73, 75, and 77 includes a metal diaphragm portion that receives pressure, and a strain gauge or a resistance element that converts deformation of the diaphragm portion due to the pressure into an electric signal. The rail pressure sensor 73 outputs an electrical signal corresponding to the rail pressure Pc in the common rail 30 to the control device 50. The sub tank pressure sensor 75 outputs an electrical signal corresponding to the sub tank pressure Ps in the sub fuel tank 90 to the control device 50. The main tank pressure sensor 77 outputs an electrical signal corresponding to the main tank pressure Pm in the main fuel tank 190 to the control device 50.

  Each of the temperature sensors 74, 76, and 78 includes a thermistor that changes a resistance value according to temperature, a thermocouple that changes a voltage according to temperature, and the like. The rail temperature sensor 74 outputs an electrical signal corresponding to the rail temperature Tc in the common rail 30 to the control device 50. The sub tank temperature sensor 76 outputs an electric signal corresponding to the sub tank temperature Ts in the sub fuel tank 90 to the control device 50. The main tank temperature sensor 78 outputs an electrical signal corresponding to the main tank temperature Tm in the main fuel tank 190 to the control device 50.

  The pressure reducing valve 71 is attached to the end of the common rail 30 in the axial direction. The pressure reducing valve 71 is an electromagnetic valve electrically connected to the control device 50. By opening the pressure reducing valve 71, DME fuel is discharged from the common rail 30 to the return fuel line 85. The pressure reducing valve 71 opens when the fuel pressure in the common rail 30 exceeds a predetermined upper limit pressure. In addition, the pressure reducing valve 71 can control the flow of the DME fuel from the common rail 30 to the sub fuel tank 90 by adjusting the opening degree by the control device 50.

  The supply cutoff valve 82 is a two-way valve provided in the supply line 81. The supply shut-off valve 82 is configured by a valve main body that allows DME fuel to flow, an actuator that controls the valve main body, and the like. The valve body of the supply shutoff valve 82 is provided with an inflow port portion 82a and an outflow port portion 82b connected to the supply line 81, respectively. The supply shutoff valve 82 can shut off the flow of DME fuel in the supply line 81 based on a control signal input to the actuator.

  The reflux shut-off valve 89 is a two-way valve provided in the second section 85 b of the return fuel line 85. The reflux shut-off valve 89 includes a valve main body that allows DME fuel to flow and an actuator that controls the valve main body. The valve body of the reflux shut-off valve 89 is provided with an inflow port portion 89a and an outflow port portion 89b that are respectively connected to the second section 85b. The reflux shut-off valve 89 can shut off the flow of DME fuel in the second section 85b based on a control signal input to the actuator. In addition, the reflux shutoff valve 89 can control the flow of DME fuel from the sub fuel tank 90 to the main fuel tank 190 by adjusting the opening degree by the control device 50.

  The control device 50 includes a processor 58 as an arithmetic circuit, a RAM, a flash memory 59 as a rewritable nonvolatile storage medium, and the like. The control device 50 includes an input unit 51 and an output unit 52.

  The input unit 51 is connected to an operation unit such as an ignition switch 54 in addition to a large number of in-vehicle sensors including the sensors 73 to 78. The ignition switch 54 receives an operation for instructing start and stop of the internal combustion engine 110. When an operator such as a vehicle driver operates the ignition switch 54, either the start signal or the stop signal of the internal combustion engine 110 is input to the input unit 51.

  The output unit 52 is connected to the cell motor 112, the feed pump 10, the supply pump 20, each injector 40, the pressure reducing valve 71, the supply cutoff valve 82, and the reflux cutoff valve 89. The output unit 52 outputs the control signal generated by the processor 58 toward these components.

  Now, the DME fuel remaining in the common rail 30 after the internal combustion engine 110 shown in FIG. 1 is stopped is heated by the internal combustion engine 110 to be in a high-pressure gas state in the common rail 30. The vaporized DME fuel leaks from the injection hole of the injector 40 to the combustion chamber 111 through the distribution line 31. The DME fuel leaking into the combustion chamber 111 may cause abnormal combustion when the internal combustion engine 110 is started next time.

  Therefore, the fuel supply device 100 performs an operation of collecting the DME fuel remaining in the common rail 30 to the main fuel tank. Hereinafter, details of the recovery performed by the fuel supply apparatus 100 will be described. The control device 50 shown in FIGS. 1 and 3 executes a control program stored in the flash memory 59 by the processor 58, whereby a pressure acquisition unit 62, a temperature acquisition unit 63, a motoring control unit 64, a gas-liquid determination The unit 65 and the valve control unit 61 are provided as functional blocks.

  The pressure acquisition unit 62 acquires the rail pressure Pc measured by the rail pressure sensor 73, the sub tank pressure Ps measured by the sub tank pressure sensor 75, and the main tank pressure Pm measured by the main tank pressure sensor 77. The temperature acquisition unit 63 acquires the rail temperature Tc measured by the rail temperature sensor 74, the sub tank temperature Ts measured by the sub tank temperature sensor 76, and the main tank temperature Tm measured by the main tank temperature sensor 78.

  The motoring control unit 64 energizes the cell motor 112 based on the temperature difference between the rail temperature Tc and the sub tank temperature Ts. Thereby, the supply pump 20 is temporarily operated via the output shaft of the internal combustion engine 110. The gas-liquid determination unit 65 vaporizes the DME fuel in the common rail 30 from the rail pressure Pc and the rail temperature Tc acquired by the pressure acquisition unit 62 and the temperature acquisition unit 63 based on the saturated vapor pressure line shown in FIG. It is determined whether or not.

  The valve control unit 61 controls opening and closing of the pressure reducing valve 71, the supply cutoff valve 82, and the reflux cutoff valve 89. The valve control unit 61 is configured to open the pressure reducing valve 71 while closing the reflux shut-off valve 89 after the internal combustion engine 110 is stopped to collect DME fuel (hereinafter referred to as “first transfer state”). To do. After the first transfer state, the valve control unit 61 closes the reflux cutoff valve 89 while closing the pressure reducing valve 71 based on the pressure difference between the rail pressure Pc acquired by the pressure acquiring unit 62 and the sub tank pressure Ps. Switch to the opened state (hereinafter “second transfer state”). The valve control unit 61 switches from the second transfer state to the first transfer state based on the pressure difference between the sub tank pressure Ps and the main tank pressure Pm. The valve control unit 61 alternately repeats the first transfer state and the second transfer state, and ends the repetition when the gas-liquid determination unit 65 makes an affirmative determination of vaporization.

  Next, specific processing performed by the processor of the control device 50 will be further described with reference to FIG. 1 based on FIGS. 5 and 6. The process shown in the flowchart of FIG. 5 is started by the control device 50 that has acquired the stop signal based on the input to the ignition switch 54.

  In S101, a control signal for switching the pressure reducing valve 71 to the valve open state is output, and the process proceeds to S102. In S102, a control signal for switching the reflux shut-off valve 89 to the closed state is output, and the process proceeds to S103. By S101 and S102, the fuel supply apparatus 100 enters a first transfer state in which the DME fuel in the common rail 30 is moved to the sub fuel tank 90.

  In S103, the rail pressure Pc and the sub tank pressure Ps are acquired from the rail pressure sensor 73 and the sub tank pressure sensor 75, and the process proceeds to S104. In S104, the rail pressure Pc acquired in S103 is compared with the sub tank pressure Ps. If it is determined in S104 that the rail pressure Pc is higher than the sub tank pressure Ps, the process of S103 and S104 is repeated until the rail pressure Pc and the sub tank pressure Ps become substantially equal. Then, when the rail pressure Pc becomes equal to or lower than the sub tank pressure Ps, the process proceeds to S105.

  In the first transfer state in S101 to S104, as shown in FIG. 6, the rail pressure Pc and the rail temperature Tc in the common rail 30 decrease with the passage of time due to the outflow of DME fuel. On the other hand, in the sub fuel tank 90 into which DME fuel flows, the sub tank pressure Ps and the sub tank temperature Ts gradually increase. Then, the movement of the DME fuel from the common rail 30 to the sub fuel tank 90 is stopped when the difference between the rail pressure Pc and the sub tank pressure Ps decreases as the sub tank temperature Ts increases. Thereby, switching from the first transfer state to the second transfer state is performed. In the above first transfer state, since the capacity of the sub fuel tank 90 is larger than the capacity of the common rail 30, the increase width of the sub tank pressure Ps and the sub tank temperature Ts is smaller than the decrease width of the rail pressure Pc and the rail temperature Tc. .

  In S105 shown in FIG. 5, a control signal for switching the pressure reducing valve 71 to the closed state is output, and the process proceeds to S106. In S106, the control signal which switches the recirculation | reflux cutoff valve 89 to a valve opening state is output, and it progresses to S107. By S105 and S106, the fuel supply apparatus 100 enters the second transfer state in which the DME fuel that has moved to the sub fuel tank 90 in the first transfer state is moved to the main fuel tank 190.

  In S107, the sub tank pressure Ps and the main tank pressure Pm are acquired from the sub tank pressure sensor 75 and the main tank pressure sensor 77, and the process proceeds to S108. In S108, the sub tank pressure Ps acquired in S107 is compared with the main tank pressure Pm. If it is determined in S108 that the sub tank pressure Ps is higher than the main tank pressure Pm, the process waits until the sub tank pressure Ps and the main tank pressure Pm become substantially equal by repeating the processes of S107 and S108. Then, when the sub tank pressure Ps becomes equal to or lower than the main tank pressure Pm, the process proceeds to S109.

  In the second transfer state in S105 to S108, as shown in FIG. 6, due to the pressure difference between the sub fuel tank 90 and the main fuel tank 190 and the gravity, the DME fuel in the sub fuel tank 90 becomes the main fuel tank 190. Move to. As the DME fuel escapes from the sub fuel tank 90 to the main fuel tank 190, the DME fuel is vaporized in the sub fuel tank 90. As a result, the sub tank pressure Ps and the sub tank temperature Ts decrease with the passage of time. On the other hand, the main tank pressure Pm and the main tank temperature Tm remain substantially constant. The movement of the DME fuel from the sub fuel tank 90 to the main fuel tank 190 is stopped when the sub tank pressure Ps decreases to the main tank pressure Pm and the pressure difference between them decreases.

  In S109 shown in FIG. 5, the rail pressure Pc and the rail temperature Tc are acquired from the rail pressure sensor 73 and the rail temperature sensor 74, and the process proceeds to S110. In S110, it is confirmed whether or not the recovery of the DME fuel in the common rail 30 has been completed. Specifically, in S110, it is determined based on the saturated vapor pressure line (see FIG. 4) whether or not all the DME fuel in the common rail 30 has been vaporized.

  If it is determined in S110 that liquid DME fuel is present in the common rail 30, the process returns to S101. By repeating S101 to S110, the first transfer state and the second transfer state are alternately repeated as shown in FIG. As a result, the rail pressure Pc and the rail temperature Tc at the end of the first transfer state gradually decrease. When it is determined in S110 shown in FIG. 5 that all the DME fuel has been vaporized, the process proceeds to S111. In S111, a control signal for switching the recirculation shut-off valve 89 to the closed state is output, and the series of collection processing ends.

  In the first embodiment described so far, in the second transfer state, the DME fuel vaporized in the sub fuel tank 90 causes the sub tank temperature Ts and thus the sub tank pressure Ps to decrease. Therefore, the liquefied gas fuel in the common rail 30 can move to the sub fuel tank 90 by changing from the second transfer state to the first movement state again. Therefore, by repeating the first transfer state and the second transfer state, it is possible to recover the DME fuel in the common rail 30 to the main fuel tank 190 while avoiding the complexity of the configuration of the fuel supply device 100.

  In addition, the DME fuel sucked out from the common rail 30 due to the latent heat of vaporization of the DME fuel vaporized in the sub fuel tank 90 is cooled in the sub fuel tank 90 and then moved to the main fuel tank 190. It becomes. Therefore, an increase in the main tank temperature Tm and the main tank pressure Pm can be prevented. As a result, in the second transfer state, the DME fuel can reliably move from the sub fuel tank 90 to the main fuel tank 190.

  In the first embodiment, the switching from the first transfer state to the second transfer state is based on the pressure difference between the rail pressure Pc and the sub tank pressure Ps when these pressures Pc and Ps are substantially equal. Done. According to such control, the first transfer state can be appropriately terminated at a timing at which the DME fuel becomes difficult to move from the common rail 30 to the sub fuel tank 90.

  Similarly, switching from the second transfer state to the first transfer state is performed when these pressures Ps and Pm are substantially equal based on the pressure difference between the sub tank pressure Ps and the main tank pressure Pm. According to such control, the second transfer state can be appropriately terminated at a timing when it becomes difficult for the DME fuel to move from the sub fuel tank 90 to the main fuel tank 190.

  Further, in the first embodiment, since the sub fuel tank 90 is provided at a position higher than the main fuel tank 190, the DME fuel in the sub fuel tank 90 is further subjected to the action of gravity in the second transfer state. Then, it moves to the main fuel tank 190. As a result, the DME fuel in the sub fuel tank 90 can quickly escape, and the vaporization of the DME fuel can effectively occur. Therefore, it becomes possible to more reliably recover the DME fuel from the common rail 30.

  In the first embodiment, since the capacity of the sub fuel tank 90 is larger than the capacity of the common rail 30, a large number of DMEs are transferred from the common rail 30 to the sub fuel tank 90 in a single first transfer state. It becomes possible to move the fuel. As a result, the number of repetitions of the first movement state and the second transfer state can be reduced, so that the time required for collecting the DME fuel can be shortened.

  Furthermore, in the first embodiment, the valve opening pressure Pdo of the discharge valve portion 25b is set higher than the differential pressure between the gallery pressure Pga and the main tank pressure Pm. With such a configuration, even if the DME fuel in the common rail 30 is recovered immediately after the internal combustion engine 110 is stopped and the pressure in the common rail 30 is reduced to the vicinity of the main tank pressure Pm, the discharge valve portion 25b is in a closed state. Can be maintained. Therefore, the DME fuel in the supply line 81 can remain in the supply line 81 without being pulled out to the common rail 30 side.

  According to the above, when the internal combustion engine 110 is restarted, the time for filling the supply line 81 with DME fuel is shortened, and the pumping of DME fuel from the supply pump 20 to the injector 40 is started quickly. As described above, it is possible to smoothly restart the internal combustion engine 110 by shortening the time required to transfer the DME fuel. Even when the supply shutoff valve 82 is closed, the DME fuel remaining in the supply line 81 can remain in the supply line 81 without flowing out to the common rail 30 side.

  In addition, in the first embodiment, the valve opening pressure Pro of the pressure regulating valve portion 27b is set higher than the valve opening pressure Pdo of the discharge valve portion 25b. Therefore, it is possible to prevent the DME fuel from flowing out from the supply line 81 to the overflow line 87 through the fuel gallery 22a by opening the pressure regulating valve portion 27b. According to the above, quick restart of the internal combustion engine 110 can be more reliably performed.

  Further, in the first embodiment, the recovery of the DME fuel from the common rail 30 to the main fuel tank 190 is continued until all the DME fuel in the common rail 30 is vaporized. If all the DME fuel in the common rail 30 is vaporized, a pressure increase that leads to leakage into the combustion chamber 111 is unlikely to occur. Therefore, if the recovery operation is continued until the vaporization of the DME fuel is confirmed, the occurrence of abnormal combustion in the internal combustion engine 110 can be reliably prevented.

  And if the sub fuel tank 90 is arrange | positioned avoiding the inside of the engine room 120 like 1st embodiment, the sub fuel tank 90 will become difficult to receive to the influence of the heat discharge | released from the internal combustion engine 110. FIG. As a result, in the second transfer state, vaporization of the DME fuel in the sub fuel tank 90 surely occurs. Therefore, the function of the sub fuel tank 90 for sucking out the DME fuel in the common rail can be surely exhibited.

  In the first embodiment, the fuel gallery 22a corresponds to the “gallery section” recited in the claims, the pressure reducing valve 71 corresponds to the “first control valve” recited in the claims, and the return fuel The line 85 corresponds to a “return fuel path” recited in the claims. The recirculation cutoff valve 89 corresponds to a “second control valve” recited in the claims, and the sub fuel tank 90 corresponds to an “inflow portion” recited in the claims. Further, the engine room 120 corresponds to a “space storing an internal combustion engine” described in the claims, and the main fuel tank 190 corresponds to a “fuel tank” described in the claims.

  The process of S103 corresponds to the “first pressure acquisition step” described in the claims, and the processes of S104 to S106 correspond to the “first switching step” described in the claims. Further, the process of S107 corresponds to the “second pressure acquisition step” described in the claims, and the processes of S108 to S110 correspond to the “second switching step” described in the claims.

(Second embodiment)
The second embodiment of the present invention shown in FIGS. 7 and 8 is a modification of the first embodiment. In the second embodiment, the rail temperature Tc is raised by operating the cell motor 112 using the function of the motoring control unit 64 (see FIG. 3). The specific processing contents will be described with reference to FIG. 1 using FIG. Note that S201 to S208 and S213 to S215 in FIG. 7 are substantially the same as S101 to S108 and S109 to S111 (see FIG. 5) of the first embodiment, respectively.

  In S209, the rail temperature Tc and the sub tank temperature Ts are acquired from the rail temperature sensor 74 and the sub tank temperature sensor 76, and the process proceeds to S210. In S210, the temperature drop of the rail temperature Tc is detected by comparing the rail temperature Tc and the sub tank temperature Ts. Specifically, in S210, it is determined whether or not the temperature difference between the rail temperature Tc and the sub tank temperature Ts exceeds a preset threshold value α (for example, about 5 ° C.). If it is determined in S210 that the temperature difference between the rail temperature Tc and the sub tank temperature Ts exceeds 5 ° C., the process proceeds to S213.

  On the other hand, if it is determined in S210 that the temperature difference between the rail temperature Tc and the sub tank temperature Ts is 5 ° C. or less, the process proceeds to S211. In S211, the cell motor 112 is energized in order to increase the temperature difference between the rail temperature Tc and the sub tank temperature Ts. Under the control of S211, the output shaft of the internal combustion engine 110 driven by the cell motor 112 operates the supply pump 20. In S212, the energization is terminated to stop the cell motor 112 and the supply pump 20, and the process proceeds to S213.

  According to the motoring operation of the internal combustion engine 110 in S209 to S212 described above, the rail pressure Pc and the rail temperature Tc in the common rail 30 can be increased again as shown in FIG. Therefore, after switching from the second transfer state to the first transfer state, the DME fuel in the common rail 30 is reliably discharged to the sub fuel tank 90. As a result, the rail pressure Pc can be lowered to a value lower than the pressure immediately before being increased by motoring. On the other hand, the rail temperature Tc is higher than the previous temperature. Therefore, the DME fuel is in a vaporized state. When the vaporization of the DME fuel is confirmed, the recovery process is terminated.

  In the second embodiment described so far, the DME fuel in the common rail 30 can be recovered in the main fuel tank 190 by repeating the first transfer state and the second transfer state as in the first embodiment.

  In addition, in the second embodiment, the pressure difference between the rail pressure Pc and the sub tank pressure Ps is increased by using the high-pressure DME fuel remaining in the pressurizing chamber, the outflow passage, and the like in the supply pump 20. It is illustrated. As a result, the recovery of DME fuel from the common rail 30 to the main fuel tank 190 is reliably continued until the DME fuel in the common rail 30 is in a gaseous state.

  Furthermore, even when the supply pump 20 is operated as in the second embodiment, the DME fuel in the supply line 81 can remain in the supply line 81 without being completely removed to the common rail 30 side. Therefore, the effect of allowing the DME fuel to remain in the supply line 81 and smoothly restarting the internal combustion engine 110 can be exhibited also in the second embodiment.

  In the second embodiment, the supply pump 20 corresponds to the “high pressure pump” recited in the claims, and the motoring control unit 64 corresponds to the “pump control unit” recited in the claims. The process of S203 corresponds to the “first pressure acquisition step” described in the claims, and the processes of S204 to S206 correspond to the “first switching step” described in the claims. Further, the process of S207 corresponds to the “second pressure acquisition step” described in the claims, and the processes of S208 to S210 correspond to the “second switching step” described in the claims.

(Other embodiments)
Although a plurality of embodiments according to the present invention have been described above, the present invention is not construed as being limited to the above embodiments, and can be applied to various embodiments and combinations without departing from the gist of the present invention. can do.

  In the above embodiment, the switching between the first transfer state and the second transfer state is performed based on the pressure difference between the rail pressure Pc and the sub tank pressure Ps and the pressure difference between the sub tank pressure Ps and the main tank pressure Pm. It was. However, switching from the first transfer state to the second transfer state can be performed based on the temperature difference between the rail temperature Tc and the sub tank temperature Ts. Similarly, switching from the second transfer state to the first transfer state can be performed based on a temperature difference between the sub tank temperature Ts and the main tank temperature Tm, for example.

  Furthermore, for example, the duration of each of the first transfer state and the second transfer state may be set in advance. In such a configuration, switching between the first transfer state and the second transfer state is performed based on an excess of duration. Moreover, the timing which mutually switches a 1st transfer state and a 2nd transfer state may be determined by combining a pressure difference, a temperature difference, and duration as mentioned above.

  In the above embodiment, when the pressure difference between the rail pressure Pc and the sub tank pressure Ps is substantially eliminated, the first transfer state is switched to the second transfer state. However, when the pressure difference between the rail pressure Pc and the sub tank pressure Ps is equal to or less than a preset threshold value, it is possible to switch from the first transfer state to the second transfer state. Similarly, when the pressure difference between the sub tank pressure Ps and the main tank pressure Pm is equal to or less than a preset threshold value, it is possible to switch from the second transfer state to the first transfer state.

  In the above embodiment, the “pressure reducing valve” and the “reflux control valve” are used as the “first control valve” and the “second control valve”, respectively. It is.

  In the embodiment described above, the repetition of the first transfer state and the second transfer state has been completed based on the vaporization of the DME fuel in the common rail. Such repeated termination conditions are not limited to the gas-liquid determination of the DME fuel in the common rail, but can be changed as appropriate. For example, the end condition may be satisfied when the first transfer state and the second transfer state are repeated a predetermined number of times or more set in advance. Alternatively, the end condition may be satisfied when the first transfer state and the second transfer state are continuously repeated for a preset time or more from the stop of the internal combustion engine.

  In the above embodiment, the determination for confirming that the end condition is satisfied is performed at the timing of switching from the second transfer state to the first transfer state. However, the completion of the end condition may be confirmed at the timing of switching from the first transfer state to the second transfer state.

  In the second embodiment, when the temperature difference between the rail temperature Tc and the sub tank temperature Ts decreases, the operation of the supply pump by motoring is performed. However, the operation of the supply pump may be performed when the pressure difference between the rail pressure Pc and the sub tank pressure Ps decreases. Furthermore, the operation of the supply pump may be performed when the first transfer state and the second transfer state are repeated a predetermined number of times.

  In the configuration corresponding to the sub fuel tank in the above embodiment, the capacity, the arrangement, and the like can be appropriately changed. For example, the capacity of the sub fuel tank can be appropriately changed according to the capacity of the common rail. Further, the sub fuel tank may be arranged side by side with the tank so as to be the same height as the main fuel tank. Further, the sub fuel tank may be disposed in the engine room.

  In the above embodiment, the functions of the delivery valve 25 and the overflow valve 27 that are one-way valves allow the DME fuel in the supply line 81 not to be removed even if the DME fuel is recovered from the common rail 30 after the internal combustion engine 110 is stopped. It was left. The type of each valve can be changed as appropriate. Further, the valve opening pressure of each valve may be appropriately changed within a range exceeding the saturated vapor pressure of the main fuel tank. For example, the valve opening pressure of the overflow valve may be set slightly lower than the valve opening pressure of the delivery valve.

  In the above embodiment, the gallery pressure Pga is used as a reference for setting the valve opening pressure Pdo of the discharge valve portion 25b. However, the pressure in the section other than the fuel gallery 22a in the pump fuel flow path 22e may be used as a reference when setting the valve opening pressure Pdo. For example, the valve opening pressure Pdo of the discharge valve portion 25b may be set higher than the differential pressure between the pressure of the DME fuel in the discharge flow path 22c and the main tank pressure Pm.

  The supply pump of the above embodiment is driven by the output shaft of the internal combustion engine. However, such a “high pressure pump” may be an electric pump driven by an electric motor. If it is the above structure, it will replace with the motoring control part 64 (refer FIG. 3), and will energize an electric motor based on the temperature difference of rail temperature Tc and subtank temperature Ts, and will operate a high pressure pump temporarily. A functional block is provided.

  In the said embodiment, DME fuel was illustrated as a liquefied gas fuel supplied to an internal combustion engine by a fuel supply system. However, the liquefied gas fuel is not limited to DME fuel. For example, diesel fuel such as light oil containing DME as the main component can be used as the liquefied gas fuel.

  The function provided by the control device of the above embodiment may be a functional block of a processor that executes a predetermined program, or may be realized by a dedicated integrated circuit. Alternatively, each function for realizing the “control method” described in the claims may be provided by hardware and software different from those described above, or a combination thereof.

  In the above embodiment, the example in which the present invention is applied to the fuel supply device that supplies fuel to the internal combustion engine mounted on the vehicle has been described. However, the present invention can be applied not only to an internal combustion engine mounted on a vehicle but also to a fuel supply device that supplies fuel to an internal combustion engine mounted on a ship, a railway vehicle, an aircraft, or the like. Furthermore, the present invention can also be applied to a fuel supply device that supplies fuel consumed in an internal combustion engine for power generation.

Pc rail pressure (common rail pressure), Pm main tank pressure (main fuel tank pressure), Ps sub tank pressure (fuel tank pressure), Tc rail temperature (common rail temperature), Ts sub tank temperature (sub fuel tank temperature) , 20 supply pump (high pressure pump), 22 pump body, 22a fuel gallery (gallery section), 22e pump fuel flow path (fuel flow path), 25b discharge valve section, 27b pressure regulating valve section, 30 common rail, 58 processor, 61 valve Control unit, 62 Pressure acquisition unit, 63 Temperature acquisition unit, 64 Motoring control unit (pump control unit), 65 Gas-liquid determination unit, 71 Pressure reducing valve (first control valve), 85 Return fuel line (return fuel path), 89 Reflux shut-off valve (second control valve), 90 sub fuel tank (inflow part), 100 fuel supply 110, internal combustion engine, 120 engine room (space), 190 main fuel tank (fuel tank)

Claims (13)

A fuel supply device in which a part of the liquefied gas fuel supplied from the fuel tank (190) to the common rail (30) of the internal combustion engine (110) is returned to the fuel tank through a return fuel path (85),
An inflow portion (90) provided in the return fuel path and into which liquefied gas fuel flowing through the return fuel path flows;
A first control valve (71) for controlling the flow of liquefied gas fuel from the common rail to the inflow portion;
A second control valve (89) for controlling the flow of liquefied gas fuel from the inflow portion to the fuel tank;
After the internal combustion engine is stopped, the first control valve is opened while the second control valve is closed, and the liquefied gas fuel in the common rail is moved to the inflow portion; By alternately opening the second control valve while closing one control valve, the second transfer state in which the liquefied gas fuel that has moved to the inflow portion in the first transfer state is moved to the fuel tank is alternated. A valve control unit (61) to be repeated,
A fuel supply device comprising: A pressure acquisition unit (62) for acquiring each pressure (Pc, Ps, Pm) of the common rail, the inflow portion, and the fuel tank;
The valve control unit
Based on the pressure difference between the common rail and the inflow portion, switching from the first transfer state to the second transfer state,
2. The fuel supply device according to claim 1, wherein switching from the second transfer state to the first transfer state is performed based on a pressure difference between the inflow portion and the fuel tank.   The valve control unit switches from the first transfer state to the second transfer state when the pressure of the common rail and the pressure of the inflow portion become substantially equal in the first transfer state. The fuel supply apparatus according to claim 2, wherein   The valve control unit switches from the second transfer state to the first transfer state when the pressure difference between the pressure of the inflow portion and the fuel tank substantially disappears in the second transfer state. The fuel supply device according to claim 2, wherein:   The fuel supply device according to claim 1, wherein the inflow portion is provided at a position higher than the fuel tank.   6. The fuel supply device according to claim 1, wherein a capacity of the inflow portion is larger than a capacity of the common rail.   The fuel supply device according to any one of claims 1 to 6, further comprising a high-pressure pump (20) that pumps the liquefied gas fuel pressurized to the common rail. A temperature acquisition section (63) for acquiring each temperature (Tc, Ts) of the common rail and the inflow section;
The fuel supply device according to claim 7, further comprising: a pump control unit (64) that operates the high-pressure pump based on a temperature difference between the common rail and the inflow portion. The high-pressure pump is
A pump body that forms a fuel flow path for circulating liquefied gas fuel;
A discharge valve portion (25b) that is opened by the pressure of the liquefied gas fuel in the fuel flow path and allows the discharge of the liquefied gas fuel toward the common rail,
The valve opening pressure of the discharge valve portion is set higher than the differential pressure between the pressure of the liquefied gas fuel in the fuel flow path and the pressure of the liquefied gas fuel in the fuel tank when the internal combustion engine is in a stopped state. The fuel supply device according to claim 7, wherein the fuel supply device is a fuel supply device. The pump body further forms a pressurizing chamber (22d) for pressurizing the liquefied gas fuel,
The high-pressure pump is opened by a pressure increase in a gallery section (22a) that supplies fuel to the pressurizing chamber in the fuel flow path, and a pressure regulating valve section that allows discharge of liquefied gas fuel from the gallery section. (27b)
The fuel supply device according to claim 9, wherein the valve opening pressure of the pressure regulating valve portion is set higher than the valve opening pressure of the discharge valve portion. A gas-liquid determination unit (65) for determining whether or not the liquefied gas fuel in the common rail is vaporized,
The valve control unit ends the repetition of the first transfer state and the second transfer state when the gas-liquid determination unit determines that all of the liquefied gas fuel in the common rail has been vaporized. The fuel supply device according to any one of claims 1 to 10.   The fuel supply device according to any one of claims 1 to 11, wherein the inflow portion is arranged to avoid a space (120) in which the internal combustion engine is stored. In the fuel supply apparatus, a part of the liquefied gas fuel supplied from the fuel tank (190) to the common rail (30) of the internal combustion engine (110) is returned to the fuel tank through a return fuel path (85). A first control valve (71) for controlling the flow of the liquefied gas fuel from the common rail to the inflow portion (90) provided in the fuel path, and the flow of the liquefied gas fuel from the inflow portion to the fuel tank are controlled. A control method for controlling the second control valve (89) by the processor (58),
A first pressure acquisition step (S103, S203) for acquiring each pressure (Pc, Ps) of the common rail and the inflow portion after the internal combustion engine is stopped;
Based on the difference between the pressures acquired in the first pressure acquisition step, the first control valve is opened while the second control valve is closed, and the liquefied gas fuel in the common rail is supplied to the inflow portion. From the first transfer state to be moved, to the second transfer state in which the liquefied gas fuel moved to the inflow portion is moved to the fuel tank by opening the second control valve while closing the first control valve. A first switching step for switching (S104 to S106, S204 to S206);
A second pressure acquisition step (S107, S207) for acquiring each pressure (Ps, Pm) of the inflow portion and the fuel tank after switching to the second transfer state;
A second switching step (S108 to S110, S208 to S210) for switching from the second transfer state to the first transfer state based on the difference between the pressures acquired in the second pressure acquisition step;
The control method characterized by including.

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