JP2010203286A - Fuel supply system, diesel engine, and fuel supply method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the startability of a diesel engine in which dimethyl ether (DME) is used as fuel. <P>SOLUTION: Fuel composed of DME in a fuel tank 1 is returned to the fuel tank 1 through a supply pipe 2a, a supply pump P2, a second return pipe 2g, and a main return pipe 2e by opening a first, a second and a third solenoid valve MV1-MV3 under a condition where a pressure feed pump P1 is operated to push and circulate fuel in a gaseous state remaining in the supply pump P2. The third solenoid valve MV3 is closed with the pressure feed pump P1 kept operating after a preset time elapses, and pressure is applied on the fuel through the action of a pressure regulating valve on an outlet side of the supply pump P2. When it is determined that fuel pressure detected by a sensor S1 is not less than preset pressure, the rotation of a starter motor of a diesel engine E is permitted, and the engine is started by rotating the starter motor. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel supply system, a diesel engine, and a fuel supply method. More specifically, the startability of a diesel engine (hereinafter also referred to as an engine) using dimethyl ether (hereinafter abbreviated as DME) as fuel can be improved. The present invention relates to a fuel supply system, a diesel engine, and a fuel supply method.

  Diesel engines using DME are attracting attention as clean engines because they do not emit soot. When DME is applied to a diesel engine, it is desirable from the viewpoint of thermal efficiency that DME is directly injected into the combustion chamber of the engine and compression ignition is performed. As a method for supplying DME, a common rail type is used as a fuel injection device in the same manner as a diesel engine using light oil as a fuel. This method is a method in which fuel is pressurized by a fuel pressurization pump (hereinafter referred to as a supply pump) attached to the engine, the pressurized fuel is held in a common rail, and the fuel is injected into the engine combustion chamber by an injector. .

  In this method, there is no need to pressurize between the fuel tank and the supply pump in the case of light oil because it is liquid at room temperature, but in the case of DME, it is a gas at room temperature, so it is in a liquid state. Must be sent to supply pump. Therefore, it is necessary to provide a pressure pump on the fuel tank side and pressurize to a pressure slightly higher than the vapor pressure due to the fuel temperature at that time. At this time, since the fuel in the fuel tank is pressurized to about 5 atm, it is filled in a liquid state. During the operation of the engine, the required fuel flow rate, fuel temperature, etc. may be monitored and controlled to an appropriate supply pressure that does not vaporize the DME, depending on the operating conditions.

  However, when the engine is stopped for a long time, the fuel pressure in the fuel pipe may drop and the DME may be in a gaseous state. There is a case where DME is not liquefied. In this state, since DME is not pumped to the common rail, it is not injected from the injector, and even if an attempt is made to start the engine with a starter, there is a problem that the engine does not start.

  Therefore, a method has been proposed in which, prior to starting the engine, pressure is applied to the fuel in the supply pump in the front stage of the engine, and the starter is driven when it is detected that the fuel pressure is the target pressure value (see Patent Document 1). ).

  Further, in an engine using DME as a fuel, a technique is disclosed in which a cut valve is provided in a return pipe for returning leaked fuel to a fuel container and the fuel is pressurized by closing the valve at the start (see Patent Document 2).

  In addition, a method may be considered in which the fuel pump on the fuel tank side is operated before the starter motor rotates, the fuel is circulated to some extent, the fuel in the piping is made into a liquid state, and then the starter motor is rotated to start the engine. It is done.

  However, in any of the methods, the DME may not be completely replaced with a liquid state on the supply pump side. FIG. 7 shows a cross-sectional view of a conventional supply pump 50. In this case, the fuel f made of DME flows from the fuel inlet 51 to the fuel outlet 52 through the fuel gallery around the plunger, and returns to the fuel tank through the return pipe 53. For this reason, gaseous fuel may remain in the periphery of the poppet valve 54a of the electromagnetic valve 54 disposed in the upper part of the supply pump 50.

  Thus, if the DME on the supply pump 50 side is not completely replaced with the liquid state, the starter motor cannot be started. As a result, the cranking time becomes longer, which causes a problem in engine startability such as battery consumption, starter motor failure, and complicated engine start operation.

JP 2005-98260 A JP 2006-250136 A

  An object of the present invention is to provide a fuel supply system, a diesel engine, and a fuel supply method capable of improving startability of a diesel engine using DME as a fuel.

  In order to achieve the above object, a fuel supply system of the present invention supplies a fuel made of dimethyl ether stored in a fuel tank to a second pump by a first pump, and further from the second pump to a diesel engine via a common rail. In a fuel supply system for a common rail type diesel engine to be supplied, a first opening / closing means provided in a supply pipe connecting the first pump and the second pump, and pressure and temperature at an inlet of the second pump are detected. First detecting means for performing the operation, second opening / closing means provided in a first return pipe for connecting the second pump and the common rail to the fuel tank, and a second for detecting the pressure inside the first return pipe. Connected in the middle of the pipe connecting the detection means, the second pump and the common rail, and connected to the first return pipe Two return pipes, a third opening / closing means provided in the second return pipe, and a control means for controlling the first and second pumps and the first, second and third opening / closing means. The means opens the first, second, and third opening / closing means in a state where the first pump is operated, and supplies the fuel in the fuel tank to the supply pipe, the second pump, the second return pipe, and Through the first return pipe, the fuel is returned to the fuel tank and circulated so as to push the gaseous fuel remaining in the second pump, and when the preset time has elapsed, the first pump remains operated. By closing the third opening / closing means, pressure is applied to the fuel by the action of the pressure regulating valve on the outlet side of the second pump, and the pressure of the fuel is detected by the first detection means, and a preset pressure is detected. If it is determined that this is the case, Serial to allow rotation of the starter motor of a diesel engine, and has a structure to start the engine by rotating the starter motor.

  Moreover, the diesel engine of this invention for achieving said objective is comprised using said fuel supply system.

  Further, the fuel supply method of the present invention for achieving the above object is to supply a fuel made of dimethyl ether stored in a fuel tank to the second pump by the first pump, and further from the second pump to the diesel via the common rail. In a fuel supply method for a common rail type diesel engine supplied to an engine, first opening and closing means provided in a supply pipe connecting the first pump and the second pump, and pressure and temperature at an inlet of the second pump A first detecting means for detecting the second pump, a second opening / closing means provided in a first return pipe connecting the second pump and the common rail and the fuel tank, and a pressure inside the first return pipe. Second detection means is connected in the middle of the pipe connecting the second pump and the common rail, and is connected to the first return pipe. And a control means for controlling the first and second pumps and the first, second and third opening and closing means, and a first opening and closing means provided on the second return pipe. With the pump activated, the first, second, and third opening / closing means are opened to supply fuel in the fuel tank to the supply pipe, the second pump, the second return pipe, and the first return pipe. Then, after returning to the fuel tank and circulating the fuel in the gaseous state remaining in the second pump, the fuel circulation step is performed for a preset time, and then the first pump is operated. In this state, by closing the third opening / closing means, a fuel pressurizing step of applying pressure to the fuel by the action of a pressure regulating valve on the outlet side of the second pump, and the fuel pressurized by the fuel pressurizing step The first detection means More detected If it is determined that a preset pressure or more, the permit rotation of the starter motor of a diesel engine, and a step of starting the engine by rotating the starter motor.

  According to the fuel supply system, diesel engine, and fuel supply method of the present invention, the second return pipe is provided in the middle of the pipe connecting the second pump and the common rail, and the third opening / closing means provided in the second return pipe is used. In the second pump of the prior art, the fuel can be circulated even in a portion where the fuel cannot be circulated before starting the engine. The fuel can be circulated, and the engine can be started after the fuel in the gaseous state is sufficiently exhausted.

  For this reason, the starting operation of the diesel engine using DME as fuel can be facilitated, and the engine starting failure can be reduced, so that the engine can be started smoothly. In addition, since the cranking time in the starter motor of the diesel engine using DME as fuel can be shortened, it is possible to reduce or prevent the starter motor from failing and the battery consumption at the time of starting the engine. Therefore, the startability of the engine can be improved.

It is the figure which showed the structure of the fuel supply system which is embodiment of this invention. It is a principal part expanded sectional view of the supply pump and 3rd solenoid valve of the fuel supply system of FIG. It is the figure which showed the flow of the fuel supply method of embodiment of this invention. It is the figure which showed the state of the fuel supply system at the time of a fuel circulation process. It is the figure which showed the state of the fuel supply system at the time of a fuel pressurization process. It is the graph which showed together the vapor pressure line of DME, and the target fuel pressure line. It is a partial expanded sectional view of the supply pump of the conventional fuel supply system.

  Hereinafter, a fuel supply system, a diesel engine, and a fuel supply method according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  The fuel supply system of the present embodiment illustrated in FIG. 1 is configured such that fuel in a fuel tank 1 is supplied to a fuel pressurization pump (first pump: hereinafter simply referred to as a pressure pump) P1 by a fuel pressurization pump ( The second pump (hereinafter referred to as a supply pump) P2 is supplied to a combustion chamber of each cylinder of a diesel engine (hereinafter simply referred to as an engine) E from a supply pump P2 via a common rail CR. It is a fuel supply system. The fuel supply system and the engine E are mounted on a vehicle such as a truck, but are not limited thereto, and may be mounted on a ship, for example.

The fuel tank 1 stores a fuel made of dimethyl ether (DME: C ₂ H ₆ O). DME has a melting point of 138.5 ° C., a boiling point of −23.7 ° C. (1 atm), a cetane number comparable to that of light oil, a specific gravity greater than that of air, and is generally easily decomposed in air. is doing. The DME in the fuel tank 1 is in a liquid state when the inside of the fuel tank 1 is maintained in a high pressure state (pressurized at about 5 atm). Although FIG. 1 illustrates the case where there is one fuel tank 1, the present invention is not limited to this, and a plurality of fuel tanks 1 may be provided.

  The pressure pump P1 in the fuel tank 1 is connected to the supply pipe 2a through the outlet valve V1 and the first electromagnetic valve (first opening / closing means) MV1 in order, and further connected to the supply pump P2 through the supply pipe 2a. Yes. The pressure feed pump P1 is provided with a pressure regulator that adjusts the fuel supply pressure (feed pressure), and the fuel in the fuel tank 1 is in a state in which the fuel supply pressure is adjusted by the pressure regulator of the pressure feed pump P1. It is pumped to the supply pump P2.

  The pressure pump P1 is electrically connected to a control device (control means) C, and the operation of the pressure pump P1 is controlled by the control device C. That is, the control device C controls the supply of fuel from the fuel tank 1 to the supply pump P2, the fuel supply pressure, the fuel supply amount per unit time, the supply stop, and the like by controlling the operation of the pressure pump P1.

  The first electromagnetic valve MV1 is provided immediately after the outlet valve V1 of the pressure pump P1. The first electromagnetic valve MV1 is electrically connected to the control device C, and the opening / closing operation of the electromagnetic valve is controlled by the control device C. That is, the control device C controls the supply and shutoff of fuel from the fuel tank 1 to the supply pump P2 by controlling the opening / closing operation of the first electromagnetic valve MV1.

  In addition, a sensor (first detection means) S1 is provided at the inlet of the supply pump P2 in the supply pipe 2a. This sensor S1 is a sensor for detecting the fuel pressure and the fuel temperature at the inlet of the supply pump P2. The sensor S1 is electrically connected to the control device C, and a signal detected by the sensor S1 is transmitted to the control device C.

  The supply pump P2 is a pressure regulating pump that raises the pressure up to a pressure (several tens to several hundreds of MPa) suitable for injecting fuel into the combustion chamber of each cylinder of the engine E, and sends the fuel to the common rail CR. And a pressure adjusting valve capable of adjusting the discharge pressure.

  The supply pump P2 is connected to the common rail CR through a plurality of pipes 2b. A plurality of injectors (fuel injection valves) J are connected to the common rail CR through a plurality of pipes 2c. The common rail CR is a component for stocking the fuel to be supplied to the injector J.

  The injector J is a component for injecting fuel into the fuel chamber of each cylinder of the engine E, and has an injection nozzle and an electromagnetic valve. The injection nozzle of the injector J is a component that injects and supplies high-pressure fuel into the combustion chamber. The electromagnetic valve of the injector J is a component that performs lift control of the needle in the injection nozzle, and is electrically connected to the control device C to control its operation.

  The engine E is a power source when the vehicle travels, and includes a starter motor for forcibly rotating the crankshaft when the engine is started. This starter motor is electrically connected to the control device C, and its operation is controlled. The engine E is provided with a rotation sensor (not shown) that detects the rotation of the engine E. The rotation sensor is electrically connected to the control device C, and the rotation detection signal detected by the rotation sensor is transmitted to the control signal C. The control device C detects the start of the engine E based on the rotation detection signal from the rotation sensor.

  A main return pipe 2e to the fuel tank 1 is connected to the supply pump P2 through a return pipe 2d connected to the fuel inlet. A check valve 3a is interposed in the middle of the return pipe 2d as a pressure regulating valve on the outlet side of the supply pump P2, so that the fuel flowing from the supply pump P2 to the main return pipe 2e does not flow back to the supply pump P2. .

  A return pipe 2f is connected to the common rail CR via a pressure control valve 3b and a solenoid valve V2. The return pipe 2f is connected to the return pipe 2d and the main return pipe 2e. The pressure control valve 3b is a pressure safety valve that opens when the fuel pressure in the common rail CR exceeds the limit set pressure, and keeps the pressure in the common rail CR below the limit set pressure. The electromagnetic valve V2 is installed so that it can be opened when the fuel pressure in the common rail CR is lowered depending on the operating state of the engine E.

  In the main return pipe 2e to the fuel tank 1, a second electromagnetic valve (second opening / closing means) MV2 is provided immediately before the return valve V3 of the fuel tank 1. The second electromagnetic valve MV2 is electrically connected to the control device C, and the opening / closing operation of the electromagnetic valve is controlled by the control device C. That is, the control device C permits or blocks the fuel on the engine E side from returning to the fuel tank 1 by controlling the opening / closing operation of the second electromagnetic valve MV2.

  The main return pipe 2e is provided with a pressure sensor (second detection means) S2. The pressure sensor S2 is a sensor that detects the fuel pressure in the return pipe 2e. The pressure sensor S2 is electrically connected to the control device C, and a signal detected by the pressure sensor S2 is transmitted to the control device C. Note that F denotes a filter.

  In the present embodiment, a return pipe 2g is connected via a third electromagnetic valve (third opening / closing means) MV3 in the middle of the pipe connecting the outlet of the supply pump P2 and the common rail CR.

  The return pipe 2g is further connected to the main return pipe 2e, and serves as a fuel flow path in a fuel circulation process described later. The third electromagnetic valve MV3 is a means for opening and closing the flow path. The third electromagnetic valve MV3 is electrically connected to the control device C, and the opening / closing operation of the electromagnetic valve is controlled by the control device C. That is, the control device C controls the opening / closing operation of the third electromagnetic valve MV3, thereby permitting or blocking the fuel supplied to the supply pump P2 from returning to the fuel tank 1 through the return pipe 2g. The supply pump P2, the return pipe 2g, and the third electromagnetic valve MV3 will be described later.

  The control device C is an electronic control unit such as an ECU (Engine Control Unit). The control device C includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a timer, and the like, and a program recorded in the ROM and DME vapor pressure diagram information described later. Various arithmetic processes are performed based on various sensor (detection) information read into the RAM, and the operations of the fuel supply system, the engine E, and the like can be controlled.

  The control device C opens the first, second, and third electromagnetic valves MV1, MV2, and MV3 in a state where the pressure feed pump P1 is operated, and supplies the fuel in the fuel tank 1 to the supply pipe 2a and the supply pump P2. Then, the gas is returned to the fuel tank 1 through the return pipe 2g and the main return pipe 2e and circulated so as to flush the fuel in the gaseous state remaining in the supply pump P2 (fuel circulation operation).

  Further, the control device C measures the time by the timer of the control device C after starting the fuel circulation operation, and when the preset time has elapsed, the third electromagnetic valve is operated with the pressure pump P1 being operated. By closing MV3, pressure is applied to the fuel by the pressure regulating action of the check valve 3a on the outlet side of the supply pump P2 (fuel pressurizing operation).

  Further, the control device C detects the fuel pressure by the sensor S1 during the fuel pressurizing operation, and determines that the pressure is equal to or higher than a preset pressure, permits the rotation of the starter motor of the engine E, and starts the starter motor. Start the engine by rotating the motor.

  Next, the configuration of the supply pump P2, the return pipe 2g, and the third electromagnetic valve MV3 of the fuel supply system of the present embodiment will be described with reference to FIG. FIG. 2 shows an enlarged cross-sectional view of the main parts of the supply pump P2, the return pipe 2g, and the third electromagnetic valve MV3.

  The supply pump P2 has a pump body 5 and an electromagnetic valve 6 installed above the pump body 5, and is driven by the engine E through a coupling (not shown). The pump body 5 includes a fuel inlet 5a, a fuel outlet 5b, a fuel passage 5c, a fuel storage chamber 5d, a cam 5e, a plunger 5f, and a plunger sliding chamber 5g.

  The pump body 5 has first and second fuel flow paths. The first fuel flow path is a flow path connected to the pipe 2b through the fuel inlet 5a, the fuel passage 5c, the fuel storage chamber 5d, and the plunger sliding chamber 5g in this order, and is connected to the common rail CR. On the other hand, the second fuel channel is a channel connected to the return pipe 2d from the fuel inlet 5a through the fuel outlet 5b, and is connected to the fuel tank 1 through the main return pipe 2e.

  In the pump main body 5, the plunger 5f is reciprocated in the vertical direction in FIG. 2 along the inner peripheral wall of the plunger sliding chamber 5g by the rotation of the cam 5e. Thereby, the fuel suction to the supply pump P2 and the fuel pressure feed to the common rail CR are alternately repeated. The fuel pressure in the common rail CR is controlled by the fuel discharge amount of the supply pump P2.

  The electromagnetic valve 6 is a control means for controlling the fuel discharge amount of the supply pump P2, and has a poppet valve 6a and an electromagnetic coil portion 6b. The poppet valve 6a is means for opening and closing a flow path between the fuel storage chamber 5c and the plunger sliding chamber 5d. The electromagnetic coil section 6b is means for controlling the vertical movement of the poppet valve 6a according to the energization timing from the control device C.

  In the fuel suction process of the supply pump P2, the poppet valve 6a of the electromagnetic valve 6 is opened, and the plunger 5f moves downward in FIG. 2, so that the fuel supplied to the fuel inlet 5a is stored in the fuel passage 5c and the fuel reservoir. It is sucked into the plunger sliding chamber 5g through the chamber 5d. On the other hand, in the fuel pumping process of the supply pump P2, when the poppet valve 6a of the electromagnetic valve 6 is closed and the plunger 5f moves upward in FIG. 2, the fuel in the plunger sliding chamber 5g is pushed out by the plunger 5f. It is pumped to the common rail CR through the pipe 2b.

  Moreover, in this Embodiment, return piping 2g is connected to the middle of piping 2b. The third electromagnetic valve MV3 is installed in the middle of the return pipe 2g. The third electromagnetic valve MV3 is formed in the fuel gallery of the supply pump P2. The third electromagnetic valve MV3 has a poppet valve MV3a and an electromagnetic coil part MV3b, and is a control means for controlling the fuel circulation operation according to the energization timing from the control device C. The poppet valve MV3a is means for opening and closing a flow path between the pipe 2b (plunger sliding chamber 5g) and the return pipe 2g. The electromagnetic coil unit MV3b is means for controlling the vertical movement of the poppet valve MV3a according to the energization timing from the control device C. That is, the pipe 2b (plunger sliding chamber 5g) and the return pipe 2g are connected or disconnected by moving the poppet valve MV3a in the vertical direction in FIG. 2 by energizing the electromagnetic coil portion MV3b from the control device C. .

  By the way, in the conventional supply pump 50 shown in FIG. 7, when the fuel made of DME is returned to the fuel tank, the fuel f is formed from the fuel inlet 51 to the fuel gallery around the plunger (the outer periphery of the portion around the plunger). Flow to the fuel outlet 52 through the grooved passage) and return to the fuel tank through the return pipe 53. That is, in this return flow path, the fuel f returns without passing through the fuel piping (the fuel passage 55, the fuel storage chamber 56 and the poppet valve 54a, the plunger sliding chamber 57, etc.) around the poppet valve of the electromagnetic valve 54. It flows into the pipe 53. For this reason, for example, when the vehicle is left for a long time with the engine stopped and the fuel pressure in the fuel pipe around the poppet valve decreases and the DME is in a gas state at that portion, Even when the fuel circulation operation is performed, the fuel f does not flow in the fuel pipe around the poppet valve, so that gas fuel may remain in the fuel pipe. Thus, if the DME on the supply pump 50 side is not completely replaced with the liquid state, the starter motor cannot be started. As a result, the cranking time becomes longer, which causes a problem in engine startability such as battery consumption, starter motor failure, and complicated engine start operation. 7 is a pipe connecting the plunger sliding chamber 57 and the common rail.

  On the other hand, in the present embodiment, in the fuel circulation operation, the fuel f is converted into the fuel inlet 5a, the fuel passage 5c, the fuel storage chamber 5d, the plunger sliding chamber 5g, the pipe 2b, the return pipe 2g, and It returns to the fuel tank 1 through the main return pipe 2e. For this reason, for example, the engine stop state of the vehicle lasts for a long time, and the fuel pressure in the fuel pipe (fuel passage 5c, fuel storage chamber 5d, poppet valve 6a, plunger sliding chamber 5g, etc.) around the poppet valve of the solenoid valve 6 increases. Even if gas DME remains in that portion, the fuel DME is left in the fuel pipe around the poppet valve of the solenoid valve 6 by performing the fuel circulation operation. Can be swept away. Thereby, the liquefied fuel can be pumped to the common rail CR, and can be injected from the injector J of the engine E. That is, by starting the engine E after performing the fuel circulation operation, the engine starting operation can be facilitated, and the engine starting failure can be reduced, so that the engine can be started smoothly. Further, since the cranking time can be shortened, it is possible to reduce or prevent the starter motor failure and the battery consumption at the time of starting the engine. Therefore, the startability of the engine E using DME as fuel can be improved.

  Next, the fuel supply method of the present embodiment will be described with reference to FIGS. 4 and 5 along the flow of FIG. 4 and 5 show the state of the fuel supply system during the fuel circulation process and the fuel pressurization process, respectively, and arrow A indicates the flow of fuel.

  First, when the driver turns on the engine key, the pressure pump P1 of the fuel tank 1 is activated (step 101 in FIG. 3). In this state, as shown in FIG. 4, the first, second, and third electromagnetic valves MV1, MV2, and MV3 are opened. Then, the fuel in the fuel tank 1 flows to the supply pump P2 through the supply pipe 2a. This fuel flows through the fuel inlet 5a, the fuel passage 5c, the fuel storage chamber 5d, the plunger sliding chamber 5g, the pipe 2b and the return pipe 2g of the supply pump P2, and returns to the fuel tank 1 through the main return pipe 2e. In this way, the fuel is circulated so as to push the gaseous fuel remaining in the supply pump P2 (step 102 in FIG. 3: fuel circulation step). Thereby, the liquefaction of the fuel proceeds in the fuel pipe around the poppet valve 6a of the electromagnetic valve 6 of the supply pump P2.

  Subsequently, the elapsed time of the fuel circulation step is measured by the timer of the control device C, and it is determined whether or not the elapsed time exceeds a preset time (for example, about 5 to 10 seconds) (step 103 in FIG. 3). ). If the elapsed time of the fuel circulation process does not exceed the preset time, the fuel circulation process of step 102 is continued.

  On the other hand, when the elapsed time of the fuel circulation process exceeds a preset time, the first and second electromagnetic valves MV1 and MV2 are kept open as shown in FIG. The third solenoid valve MV3 is closed. Thereby, pressure is applied to the fuel by the pressure regulating action of the check valve 3a on the outlet side of the supply pump P2, and the fuel supply pressure is increased (step 104 in FIG. 3: fuel pressurization step).

  Subsequently, it is determined whether the fuel pressure at the inlet of the supply pump P2 (that is, the fuel pressure detected by the sensor S1) is equal to or higher than the first fuel pressure set in advance by the fuel pressurization step (FIG. 3). Step 105). The first fuel pressure is calculated by the control device C based on the fuel temperature at the time of starting the engine and the DME fuel vapor pressure diagram. The control device C calculates the pressure at which the DME is in a liquid state. It is confirmed whether or not the detected pressure is higher than the pressure at which the liquid state is reached.

  If the fuel pressure detected by the sensor S1 does not become the first fuel pressure, the fuel pressurization process is continued. On the other hand, when the fuel pressure detected by the sensor S1 becomes equal to or higher than the first fuel pressure, the rotation of the starter motor is permitted. In this state, the starter motor does not operate even if the engine key is set to the starter position (step 106 in FIG. 3). At this stage, the fuel is completely liquefied by the supply pump P2 (in the fuel pipe around the poppet valve 6a of the electromagnetic valve 6).

  In such a state, when the start switch is turned on (the engine key may be substituted for the starter position), the starter motor rotates and starts cranking. The engine injection device is controlled by the control device C and starts the engine E as usual (step 107 in FIG. 3). When the engine E is started in this way, the fuel system start mode is canceled as it is, and the process returns (step 108 in FIG. 3). After returning, the mode is changed to the normal operation mode.

  Next, FIG. 6 is an example of a graph showing the DME vapor pressure diagram information and the target fuel pressure map together. In the vapor pressure diagram, the horizontal axis indicates the fuel temperature (° C.), and the vertical axis indicates the DME vapor pressure (atm). Further, in the target fuel pressure map, the horizontal axis indicates the fuel temperature (° C.), and the vertical axis indicates the DME target fuel pressure (atm).

  VP0 (solid line) indicates the DME vapor pressure line, and VP1 (broken line) indicates the target fuel pressure line in the start mode. This target fuel pressure is a target value of the fuel pressure detected by the sensor S1 at the inlet of the supply pump P2. The pressure value of the target fuel pressure line VP1 corresponds to the preset first fuel pressure.

  In the present embodiment, the fuel pressure (target fuel pressure line VP1) at the inlet of the supply pump P2 in the start mode is set to be higher than the vapor pressure (vapor pressure line VP0) so that DME is not vaporized. Yes. Note that information as illustrated in FIG. 6 is recorded in advance in the ROM of the control device C, and the control device C performs the control operation based on this information.

  According to the fuel supply system, diesel engine, and fuel supply method of the present embodiment as described above, the fuel circulation operation and the fuel pressurization operation are sequentially performed in the engine start mode prior to the actual engine start, so that the supply pump P2 side The cranking can be started by operating the starter motor after the DME is completely replaced by the liquid state. For this reason, the engine starting operation can be facilitated, and the engine starting failure can be reduced, so that the engine E can be started smoothly.

  In addition, since the starter motor is operated and cranking is started after the DME is completely replaced with liquid on the supply pump P2, the cranking time can be shortened, and the starter motor failure and the battery at the time of engine start-up can be shortened. Consumption can be reduced or prevented. Therefore, the startability of the engine E using DME as fuel can be improved.

1 Fuel tank 2a Supply pipe 2b, 2c Pipe 2d Return pipe 2e Main return pipe (first return pipe)
2f Return pipe 2g Return pipe (second return pipe)
3a Check valve (pressure regulating valve)
3b Pressure control valve 5 Pump body 5a Fuel inlet 5b Fuel outlet 5c Fuel passage 5d Fuel storage chamber 5e Cam 5f Plunger 5g Plunger sliding chamber 6 Electromagnetic valve 6a Poppet valve 6b Electromagnetic coil part P1 Fuel pump (first pump)
P2 Fuel pressurizing pump (second pump)
CR Common rail E Diesel engine V1 Outlet valve V2 Solenoid valve V3 Return valve MV1 First solenoid valve (first opening / closing means)
MV2 second solenoid valve (second opening / closing means)
MV3 third solenoid valve (third opening / closing means)
MV3a Poppet valve MV3b Electromagnetic coil part C Control device (control means)
S1 sensor (first detection means)
S2 Pressure sensor (second detection means)
J Injector F Filter

Claims (3)

In a fuel supply system for a common rail type diesel engine, a fuel made of dimethyl ether stored in a fuel tank is supplied to a second pump by a first pump, and further supplied from the second pump to the diesel engine via a common rail.
First opening / closing means provided in a supply pipe connecting the first pump and the second pump;
First detection means for detecting pressure and temperature at the inlet of the second pump;
A second opening / closing means provided in a first return pipe connecting the second pump and the common rail to the fuel tank;
Second detection means for detecting the pressure inside the first return pipe;
A second return pipe connected in the middle of the pipe connecting the second pump and the common rail, and connected to the first return pipe;
A third opening / closing means provided in the second return pipe;
Control means for controlling the first and second pumps and the first, second and third opening and closing means;
The control means opens the first, second, and third opening / closing means in a state where the first pump is operated, and supplies the fuel in the fuel tank to the supply pipe, the second pump, and the second return. Return the fuel tank to the fuel tank through the pipe and the first return pipe, and circulate the fuel in the gaseous state remaining in the second pump. When the preset time has elapsed, the first pump is activated. In this state, by closing the third opening / closing means, pressure is applied to the fuel by the action of the pressure regulating valve on the outlet side of the second pump, and the pressure of the fuel is detected by the first detection means. A fuel supply system configured to permit rotation of the starter motor of the diesel engine and start the engine by rotating the starter motor when it is determined that the pressure is equal to or higher than the predetermined pressure.   A diesel engine using the fuel supply system according to claim 1. In a fuel supply method for a common rail type diesel engine, a fuel made of dimethyl ether stored in a fuel tank is supplied to a second pump by a first pump, and further supplied from the second pump to the diesel engine via a common rail.
First opening / closing means provided in a supply pipe connecting the first pump and the second pump;
First detection means for detecting pressure and temperature at the inlet of the second pump;
A second opening / closing means provided in a first return pipe connecting the second pump and the common rail to the fuel tank;
Second detection means for detecting the pressure inside the first return pipe;
A second return pipe connected in the middle of the pipe connecting the second pump and the common rail, and connected to the first return pipe;
A third opening / closing means provided in the second return pipe;
Control means for controlling the first and second pumps and the first, second and third opening and closing means;
In a state where the first pump is operated, the first, second, and third opening / closing means are opened, and fuel in the fuel tank is supplied to the supply pipe, the second pump, the second return pipe, and the first A fuel circulation step for circulating the fuel in a gaseous state that is returned to the fuel tank and returned to the second pump through the return pipe;
After the fuel circulation step is performed for a preset time, the third opening / closing means is closed while the first pump is operated, so that the pressure is applied to the fuel by the action of the pressure regulating valve on the outlet side of the second pump. A fuel pressurizing step for adding
When the pressure of the fuel pressurized in the fuel pressurizing step is detected by the first detection means and determined to be equal to or higher than a preset pressure, rotation of the starter motor of the diesel engine is permitted, and the starter And a fuel supply method including a step of starting an engine by rotating a motor.

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