JP2639017C - - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a variable discharge high pressure pump for pumping fuel to a common rail of a diesel engine. [Prior Art] A conventional variable discharge high-pressure pump (hereinafter simply referred to as a high-pressure pump) will be briefly described with reference to FIG. 9. A high-pressure pump 10 a includes a cam chamber 12 provided at a lower end of a pump housing 11 and a pump housing 11. Cylinder 13 and housing 1 fitted in
1 and includes an introduction pipe 14 for introducing low-pressure fuel supplied from a low-pressure supply pump (not shown) into the cylinder 13 and an electromagnetic valve 15 screwed to the cylinder 13. A camshaft 16 that rotates at half the rotational speed of the diesel engine is inserted into the cam chamber 12, and a substantially elliptical cam 17 is mounted on the camshaft 16. That is, the camshaft 16 is driven to make one rotation for every two rotations of the diesel engine that completes one cycle with two rotations. A plunger 18 is accommodated in the sliding hole 13a of the cylinder 13 so as to be able to reciprocate. The plunger 18 has a cylindrical shape without any leads, and a plunger chamber 19 is formed by the plunger 18 and the sliding hole 13 a of the cylinder 13. The feed hole 2 communicating with the plunger chamber 19 is provided in the cylinder 13.
A communication hole 21 that communicates with the plunger chamber 19 above the zero and the feed hole 20 is formed. The feed hole 20 communicates with a fuel reservoir 22 formed between the cylinder 13 and the pump housing 11, and the fuel reservoir 22 is supplied with low-pressure fuel from a low-pressure pump (not shown) via the introduction pipe 14 and the feed hole 20. Is done. A check valve 23 is provided in the cylinder 13, and the check valve 23 communicates with the plunger chamber 19 through a communication hole 21. In the check valve 23, the fuel pressurized inside the plunger chamber 19 pushes and opens the valve body 24 of the check valve 23 against the combined force of the return spring 25 and the fuel pressure in the common rail (not shown). As a result, fuel is discharged from the discharge port 26. The discharge port 26 communicates with a common rail via a distribution pipe (not shown). A valve seat 27 is connected to a lower portion of the plunger 18, and the valve seat 27 is pressed against a tappet 29 by a plunger spring 28. A cam roller 30 is rotatably provided on the tappet 29, and the cam roller 30 is provided with the plunger spring 2.
The urging force 8 presses the cam 17 in the cam chamber 12. Therefore, the camshaft 1
The plunger 18 reciprocates through the cam roller 30 and the valve seat 27 which move up and down following the contour 17a of the cam 17 with the rotation of the cam 6. The displacement and speed of the reciprocation of the plunger 18 with respect to the predetermined rotation angle of the cam 17 are determined by the contour 17a of the cam 17. Accordingly, when the plunger 18 reciprocates in the sliding hole 13a of the cylinder 13, the plunger 18 opens and closes the feed hole 20, and when the plunger 18 does not close the feed hole 20, low-pressure fuel is supplied through the feed hole 20 to the plunger chamber 19. Supplied to An electromagnetic valve 15 is screwed to the upper end of the cylinder 13 so as to face the plunger 18. As shown in FIG. 10, the solenoid valve 15 has a body 32 in which a low-pressure passage 31 having one end opened to the plunger chamber 19 is formed, and a biasing force of a spring 35 by a magnetic force of a solenoid 34 energized through a lead wire 33. The armature 36 is sucked in the direction indicated by the arrow A in the same drawing, and moves integrally with the armature 36 to form the plunger chamber 19 at the opening. Seat part 3
7 and a mushroom-shaped valve body 38 which is an externally opened valve that opens and closes the low-pressure passage 31 by being seated. The valve element 38 receives the fuel pressure of the plunger chamber 19 as a pressing force in the valve closing direction (the direction indicated by the arrow A in the figure). When the solenoid valve 15 is energized at a predetermined time after the plunger 18 closes the feed hole 20, the valve body 38 is seated on the seat portion 37 to set the pressurization start timing of the plunger 18 when the power is supplied at a predetermined time. Solenoid valve. In addition, as shown in FIG.
Is connected to the above-described fuel reservoir 22 through a gallery 39 and a passage 40. [Problems to be Solved by the Invention] In the high-pressure pump 10a, the feed hole 20 as a fuel suction passage to the plunger chamber 19 and the low-pressure passage 3 as a return passage which is an outlet of a return flow.
1 is different from the fuel system. For this reason, if a failure such as sticking occurs when the valve body 38 of the solenoid valve 15 is closed, it becomes impossible to control the fuel discharged from the check valve 23, and there is a danger that the common rail pressure will suddenly increase. If the pressure of the common rail exceeds a limit pressure determined by the strength and safety of the engine and the fuel injection device, each part of the fuel injection device may be damaged. An object of the present invention is to provide a structure and a control method of a high-pressure pump that does not pump fuel to a common rail even when a solenoid valve fails, and a control method of the high-pressure pump at the time of engine start. I do. [Technical Means for Solving the Problems] To solve the above problems, the present invention has the following structure and method. (1) A cylinder having a sliding hole for movably accommodating a plunger that reciprocates in synchronization with the rotation of a diesel engine, and an upper end surface of the plunger when the top dead center side of the plunger is directed upward. A plunger chamber formed by a sliding hole of the cylinder, a suction passage for introducing low-pressure fuel into the plunger chamber, and an electromagnetic valve for opening and closing an opening of the plunger chamber on the plunger top dead center side. A return passage communicating with the plunger chamber by opening a solenoid valve, and a check valve communicating with the plunger chamber at a position above a top dead center of the plunger and opening at a predetermined pressure, the solenoid valve comprising: , The low-pressure fuel is sucked into the plunger chamber, the fuel is pressurized by raising the plunger, the solenoid valve is closed, and the pressurized fuel is discharged by opening the check valve. A variable discharge high pressure pump for pumping fuel of a predetermined pressure to a common rail for a diesel engine under control, wherein the suction passage is shared with the return passage, and the solenoid valve is provided at an upper end of the cylinder. The solenoid valve is mounted opposite the upper end of the plunger and has a valve body disposed in the plunger chamber. When no power is supplied, the valve body moves toward the inside of the plunger chamber by the urging force of a spring. By projecting, the opening is opened, and when energized, the valve body closes the opening from the inside of the plunger chamber against the urging force of the spring by magnetic force.
A configuration comprising an electromagnetic valve of an outward opening type, and further, pressurization of the fuel in the plunger chamber is terminated when the plunger is lifted. (2) It is determined whether or not the pressure change rate of the common rail has become positive in the open state of the solenoid valve due to non-energization during the normal control of the variable discharge amount high pressure pump of the preceding item 1; The control method characterized in that when it is determined that the condition has been satisfied, the solenoid valve is constantly energized to keep the solenoid valve closed. (3) In the variable discharge high-pressure pump according to the above item 1, when the diesel engine is started, the solenoid valve is not synchronized with the rotation of the engine instead of the normal control when the diesel engine is started. Performing a specific control. (4) The control method according to the above item 3, wherein the energizing time T1 and the non-energizing time T2 are represented by the following equations. T1 = T3 + TC Here, T3: the time required for the plunger to rise from its bottom dead center and reach the pressure at which the solenoid valve is maintained closed at the lowest engine speed at engine start. TC: Valve closing time delay after energizing the solenoid valve. Qmax: maximum discharge amount from the high-pressure pump. C: Constant determined by fuel viscosity and the like. S: fuel passage area. Pf: supply fuel pressure. Pk: plunger chamber pressure. T0: Delay of valve opening time after de-energization of solenoid valve. [Operation] In the configuration of (1), in order to feed fuel to the common rail for a diesel engine, first, energization of the solenoid valve is stopped when the plunger is lowered. As a result, the valve body of the solenoid valve projects toward the inside of the plunger chamber by the urging force of the spring, and the opening of the plunger chamber is opened. As a result, the plunger chamber and the suction passage shared with the return passage (hereinafter, referred to as the return passage) The low pressure fuel is sucked into the plunger chamber from the common passage as the plunger descends. Also, even after the plunger has changed from descending to rising, the solenoid valve keeps the valve opened by the urging force of the spring, so that part of the fuel in the plunger chamber is returned to the outside through the shared passage. Becomes Next, at a predetermined time during which the plunger is rising, the solenoid valve is energized. Thus, the valve body of the solenoid valve closes the opening of the plunger chamber from the inside against the urging force of the spring due to the magnetic force. As a result, the plunger chamber and the above-mentioned common passage are shut off, and the fuel pressure in the plunger chamber rises as the plunger rises thereafter. When the pressure in the plunger chamber exceeds a predetermined pressure, the check valve opens, and pressurized fuel is discharged from the check valve to the common rail. In this pressurized state, the valve body of the solenoid valve receives the fuel pressure of the plunger chamber as a pressing force in the valve closing direction, so that the solenoid valve is reliably closed. Thereafter, when the plunger reaches the top dead center and the plunger ascends, the pressurization of the fuel in the plunger chamber ends, and for example, the power supply to the solenoid valve is stopped at this timing. Then, with the subsequent lowering of the plunger, low-pressure fuel is sucked into the plunger chamber again from the shared passage. As described above, according to the configuration (1), the amount of fuel discharged to the common rail can be changed depending on a period from when the solenoid valve is closed during the rising of the plunger to when the rising of the plunger ends. In particular, since the intake passage and the return passage for introducing the low-pressure fuel into the plunger chamber are shared, the plunger is lowered when a failure such as the valve body of the solenoid valve is stuck in the closed state. However, the low-pressure fuel is not sucked into the plunger chamber. Therefore, at the time of such a failure, it is possible to prevent the fuel from being fed to the common rail and to prevent the pressure of the common rail from abnormally increasing, and to reliably prevent each part of the fuel injection device of the engine from being damaged. Can be. Further, according to the above configuration (1), since the electromagnetic valve is an open-open type electromagnetic valve in which the valve body receives the fuel pressure of the plunger chamber as a pressing force in the valve closing direction, a simple configuration is used. To achieve high sealing performance, and pressurization of the fuel in the plunger chamber is completed when the plunger rises.
The pressurized fuel can be pumped to the common rail without waste, and a high-pressure pump with extremely high energy efficiency can be obtained. By the way, in the configuration of the above (1), when the spring of the solenoid valve is broken and it becomes impossible to apply the urging force in the valve opening direction to the valve body, the power supply to the solenoid valve is stopped. When the plunger moves down, the valve element of the solenoid valve moves toward the inside of the plunger chamber due to the pressure difference between the common passage and the plunger chamber, and low-pressure fuel is sucked into the plunger chamber from the common passage. When the plunger changes from lowering to rising, the valve body of the solenoid valve closes due to the increase in the pressure of the plunger chamber even if the power supply to the solenoid valve is stopped. As a result, fuel in the plunger chamber is added. Pressurized fuel is discharged from the check valve to the common rail more than necessary. Therefore, when such a spring breaks down, the common rail pressure rises abnormally,
Each part of the fuel injection device may be damaged. In order to solve this problem, the control method (2) is effective. That is, according to the control method (2), when the pressure change rate of the common rail becomes positive in spite of the state in which the energization of the solenoid valve is stopped and the solenoid valve is opened. It is determined that an abnormality has occurred in the solenoid valve, and the solenoid valve is always energized. Therefore, if the spring that urges the valve body of the solenoid valve in the valve opening direction is broken, the solenoid valve is held in the closed state, and even if the plunger is lowered, low-pressure fuel is sucked into the plunger chamber. As a result, it is possible to reliably prevent the pressure of the common rail from abnormally increasing. On the other hand, in the configuration of the above (1), when the diesel engine is started, since the reciprocating speed of the plunger is low, it takes time to increase the pressure in the common rail. In order to solve this problem, the control methods (3) and (4) are effective. That is, according to the control methods (3) and (4), when the engine is started, the solenoid valve is subjected to pulse control including an energization time T1 and a non-energization time T2 that are asynchronous with the rotation of the engine. Will be Therefore, as shown in FIG. 6, which will be described later, a sufficient amount of low-pressure fuel is sucked into the plunger chamber for each of a plurality of non-energizing times T2 during the low-speed descending stroke of the plunger at the time of engine start, The sufficient amount of fuel can be reliably pumped to the common rail. That is, in the plunger ascent stroke, the valve body of the solenoid valve receives the fuel pressure of the plunger chamber as a pressing force in the valve closing direction, so that the pressure of the plunger chamber increases the valve closing maintenance pressure capable of maintaining the valve body in the closed state. If it is larger, the solenoid valve will maintain the closed state even during the period of the non-energization time T2, and almost all the fuel sucked into the plunger chamber during the descending stroke of the plunger can be pumped to the common rail. It is. For this reason, the pressure of the common rail can be quickly increased in a low rotation range at the time of engine start. EXAMPLES The present invention will be described below with reference to the drawings showing examples. High pressure pump 10 of the present invention
Is the same as the high-pressure pump 10a except that the feed hole 20 of the conventional high-pressure pump 10a shown in FIG. 9 is eliminated and the low-pressure passage 31 of the solenoid valve 15 is also used as a fuel supply passage as shown in FIG. It is. Therefore, the same components as those in FIGS. 9 and 10 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 1, the fuel introduced into the fuel reservoir 22 is supplied to the plunger chamber 19 through the passage 40 in the cylinder 13, the gallery 39 in the solenoid valve 15, and the low-pressure passage 31. The return fuel flows from the plunger chamber 19 in the opposite direction to the supply fuel and returns to the fuel reservoir 22. FIG. 2 is an explanatory view in which main parts of the high-pressure pump 10 are simplified. As shown in FIG. 3, the introduction pipe 14 of the high-pressure pump 10 communicates with the fuel tank 4 via the low-pressure fuel passage 2 and the low-pressure supply pump 3, and the discharge port 26 of the check valve 23 via the high-pressure fuel passage 5. It communicates with the common rail 6. The common rail 6 is connected to injectors 7a to 7f corresponding to the cylinders 8a to 8f of the diesel engine 1. Reference numeral 9 denotes a control unit which includes a CPU 9a, a ROM 9b, a RAM 9c, and an input / output unit 9d, inputs necessary data from the engine 1 and the common rail 6, and outputs on-off valve signals to the high-pressure pump 10 and the injectors 7a to 7f. In the above configuration, when the plunger 18 descends, the solenoid 3 of the solenoid valve 15
4 is not energized, and the valve body 38 is opened by the urging force of the return spring 35. The low-pressure fuel from the supply pump 3 is supplied to the introduction pipe 14, the fuel reservoir 22,
It flows into the plunger chamber 19 through the return outlet 31 of the solenoid valve 15 and the valve body 38. Also, at the initial stage of the ascent of the plunger 18, the valve body 38 remains open, and a part of the fuel in the plunger chamber 19 is returned to the fuel reservoir 22 via the valve body 38, the low-pressure passage 31, and the gallery 39. At this time, when the solenoid 34 is energized, a suction force greater than the urging force of the return spring 35 acts on the solenoid 34, and the valve body 38 closes. Therefore, the fuel pressure in the plunger chamber 19 increases. When the fuel pressure becomes equal to or higher than the sum of the urging force of the return spring 25 of the check valve 23 and the fuel pressure in the common rail 6, the check valve 23 opens and fuel is fed to the common rail 6 via the high-pressure fuel passage 5. . After the completion of the pressure feeding, the power supply to the solenoid 34 of the electromagnetic valve 15 is stopped, and the valve body 38 is opened. The control of the high-pressure pump 10 by energizing and de-energizing the solenoid 34 is referred to as normal control. In this normal control, if the energizing and de-energizing timings are changed, the pressure feeding stroke of the plunger 18 changes, and the fuel pressure in the common rail changes. Can be changed. FIG. 4 shows an example of the lift amount H with respect to the time of the plunger 18 of the high-pressure pump 10 in the case of the normal control. The solenoid valve control signal instructs valve closing with a delay of the control time TF1 from the reference pulse. At this time, the plunger 18 has already been lifted by a predetermined amount. When the solenoid valve 15 closes, the high-pressure pump 10 starts to pump fuel, so that the fuel (H1 in FIG. 4) from the lift to the full lift Hmax is pumped to the common rail 6. If the solenoid valve 15 sends a valve closing signal with a delay of the control time TF2 from the reference pulse, the lift stroke of the plunger 18 at this time is already large, and the pumping stroke is reduced to only H2. Therefore, if the control time TF is lengthened, the pumping amount decreases, and if the control time TF is shortened, the pumping amount increases. In the high pressure pump 10, the plunger 1 is fixed in a state where the solenoid valve 15 is fixed in a closed state.
Even when the valve 8 is lowered, the fuel supplied from the supply pump 3 to the solenoid valve 15 does not flow into the plunger chamber 19 because the valve body 38 is closed. Therefore, even if the plunger 18 moves up, the fuel is not fed to the common rail 6 under pressure, so that the injector 7 is not damaged. Next, when the return spring 35 of the valve 15 loses the urging force against the valve body 38 due to breakage or the like, the gallery 39 and the plunger chamber 1 are moved when the plunger 18 is lowered.
The valve body 38 is opened by the pressure difference from the valve 9, and the fuel sent from the supply pump 3 to the solenoid valve 15 flows into the plunger chamber 19. When the plunger 18 rises, the pressure in the plunger chamber 19 becomes larger than the pressure in the gallery 39. At this time, since there is no urging force of the return spring 35, the valve body 38 closes, the fuel in the plunger chamber 19 is pressurized, and is fed to the common rail 6 through the check valve 23. Therefore, even if the solenoid 34 of the solenoid valve 15 is not energized, the fuel is pressure-fed to the common rail 6, and the pressure in the common rail 6 rises sharply, and each part of the fuel injection device may be damaged. FIG. 5 is a method invention made to prevent the above danger. In FIG. 5, in addition to the normal control described above, when the pressure change rate of the common rail 6 indicates a positive value in a state where the solenoid 34 is not energized, it is determined that an abnormality has occurred in the solenoid valve 15, and Always energize. A signal having a positive pressure change rate is obtained by calculating a signal from a pressure sensor 6 a provided on the common rail 6 by the control device 9, and a valve closing signal is transmitted from the control device 9 to the solenoid valve 15. This control keeps the solenoid valve 15 in the closed state and prevents fuel from flowing into the plunger chamber 19 of the high-pressure pump 10. Therefore, pressure feed of the fuel to the common rail 6 is prevented. 6 to 8 are explanatory diagrams of a method of rapidly increasing the pressure of the common rail 6 at the time of starting the engine using the high-pressure pump 10 of the present embodiment. When the engine is started, the engine is running at low speed, and if the solenoid valve 15 is normally controlled due to insufficient voltage of the CPU 9a, insufficient output of the angle sensor of the cam 17, etc., it takes time for the pressure rise in the common rail 6 to increase. Take it. Therefore, as shown in FIG. 6, pulse control of the normal time T1 and the non-energization time T2 asynchronous with the rotation speed of the high-pressure pump 10 is applied to the solenoid valve 15. The valve body 38 closes after the valve closing feed time TC has elapsed after the power has been supplied, and opens after the valve opening time delay time T0 has elapsed since the power has not been supplied. At this time, the pressure of the plunger chamber 19 increases because the plunger 18 rises while the valve body 38 is closed. The valve body 38 shown in FIG. 2 is an open-out type, and the pressure Pk of the plunger chamber 19 is controlled by the valve body 38.
Becomes larger than the valve-closing maintenance pressure P1 of the valve body 3 even if the solenoid 34 is de-energized.
8 keeps the valve closed. The valve closing maintenance pressure P1 is expressed by the following equation based on the load of the return spring 35 as FS, the diameter of the seat portion of the valve body 38 as DS, the supply fuel pressure Pf, and the pi. When the valve body 38 is maintained in the closed state, the plunger 18 rises and the plunger chamber 1 is raised.
The pressure at 9 rises, and the fuel is pumped to the common rail 6 via the check valve 23. When the plunger 18 descends and the pressure in the plunger chamber 19 becomes smaller than the valve closing maintenance pressure P1 of the valve body 38, the valve body 38 repeatedly opens and closes by the pulse current flowing through the solenoid 34, and opens the valve body 38. In the valve period, fuel flows into the plunger chamber 19 via the valve element 38. Next, the setting of the energizing time T1 and the non-energizing time T2 in the pulse control will be described. At the minimum number of revolutions at the time of engine start, a necessary power supply from when the plunger 18 of the high-pressure pump 1 starts rising from its bottom dead center to when the pressure for maintaining the valve body 38 closed in the plunger chamber 19 is generated. Time T1 is obtained. For this purpose, the ascending displacement ΔH of the plunger 18 for generating the valve-closing maintaining pressure P1 is obtained by the following equation from the supplied fuel pressure Pf, the fuel volume V, the bulk elastic modulus E of the fuel, the diameter Dk of the plunger, and the π. . By setting the valve opening pressure of the check valve 23 in FIG. 2 larger than the valve closing maintaining pressure P1 of the valve body 38, the fuel volume V becomes the volume up to the seat portion of the check valve 23. Here, the time ΔT required for the plunger 18 to be displaced by H becomes the longest at the bottom dead center of the plunger as shown in FIG. Therefore, the time ΔT required for the plunger 18 to be displaced from the bottom dead center by ΔH at the minimum rotation speed at the time of engine start is represented by time T3.
Assuming that the valve closing delay time of the valve body 38 is TC, the energization time T1 is expressed by the following equation. T1 = T3 + TC Further, from the condition based on the fuel suction, the non-energization time T2 is expressed by the following equation so that the maximum fuel discharge amount Qmax can be suctioned by one valve opening. Here, C is a constant determined by physical properties such as the viscosity of the fuel, and S is the channel area. The solid line in FIG. 8 shows the pump discharge amount Qmm ³ / st with respect to the difference TT between the time when the plunger 18 is located at the bottom dead center and the time when the solenoid valve 15 closes. Here, if the pulse control cycle (T1 + T2) is doubled, for example, as shown by the broken line, the fluctuation of the discharge amount Q increases, and the average discharge amount decreases. Therefore, the smaller the cycle (T1 + T2), the smaller the fluctuation of the discharge amount Q, the larger the average discharge amount, and the pressure of the common rail 6 can be increased in a short time. From the above examination, the normal time T1 and the non-energization time T2 of the pulse control are determined. [Effects] The present invention has the following configuration and control method, and therefore has the following excellent effects. (A) According to the high-pressure pump according to the first aspect, since the suction passage and the return passage for introducing the low-pressure fuel into the plunger chamber are shared, the valve body of the solenoid valve is fixed in a closed state. In this case, the pressure of the common rail does not increase, and therefore, each part of the fuel injection device of the engine is not damaged. In addition, since the pressurization of the fuel in the plunger chamber is terminated when the plunger is lifted, the high sealing performance and the energy efficiency can be achieved with a simple configuration. . (B) According to the control method of the second aspect, when the spring for urging the valve body of the solenoid valve in the valve opening direction is broken, the solenoid valve is held in the closed state. The same effect as in (a) can be obtained. (C) According to the control method of the third and fourth aspects, the pressure in the common rail can be rapidly increased even at the time of low rotation such as when the engine is started, and thus the startability is improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a vertical sectional front view of one embodiment. FIG. 2 is an explanatory view of a main part of FIG. FIG. 3 shows a configuration diagram of an engine fuel control device including one embodiment. FIG. 4 shows the opening / closing time of the solenoid valve and the plunger lift during the normal control using the reference pulse. FIG. 5 shows a flowchart of solenoid valve control when the return spring of the solenoid valve is broken. 6 to 8 are diagrams relating to the start of the engine, and FIG. 6 shows the drive current to the solenoid valve, the operating (opening / closing) state of the solenoid valve corresponding to the drive current, the plunger displacement and the fluctuation of the plunger chamber pressure. FIG. FIG. 7 is a diagram showing the relationship between the displacement from the bottom dead center of the plunger and the time required for the displacement. FIG. 8 shows the relationship between the difference TT between the time of the bottom dead center of the plunger and the time of closing the solenoid valve and the pump discharge amount Q. FIG. 9 is a vertical sectional front view of a conventional high-pressure pump. FIG. 10 shows a vertical front view of a conventional solenoid valve. DESCRIPTION OF SYMBOLS 10 ... Variable discharge high pressure pump 15 ... Solenoid valve 18 ... Plunger 19 ... Plunger chamber 23 ... Check valve 31 ... Return outlet

Claims (1)

All Claims (1) and a cylinder having a sliding hole you accommodated movably plunger which reciprocates in synchronization with the rotation of the diesel engine, if the dead point side upward direction of the plunger and the upper The top and front of the plunger
A plunger chamber constituted by the sliding hole of the cylinder, a suction passage for introducing low-pressure fuel into the plunger chamber, and a solenoid valve for opening and closing the opening of the plunger chamber on the plunger top dead center side. A return passage communicating with the plunger chamber by opening a solenoid valve, and a check valve communicating with the plunger chamber at a position above a top dead center of the plunger and opening at a predetermined pressure, the solenoid valve comprising: , A low-pressure fuel into the plunger chamber, pressurization of the fuel by plunger elevation, closing of the solenoid valve, and discharge of the pressurized fuel by opening the check valve. a variable discharge high pressure pump for pumping the common rail to a predetermined pressure fuel in use, the provided suction passage is shared with the return passage, wherein the solenoid valve, the cylinder The end portion, taken opposite the upper end of the plunger
Ri together are attached, said solenoid valve, said opening by have a arranged valve body into the plunger chamber, the valve body when no current is projected to the inner side of the plunger chamber by the urging force of the spring Opening the portion, when energized, the valve body closes the opening from the inside of the plunger chamber against the urging force of the spring by magnetic force,
A variable discharge high pressure pump, comprising an open-open solenoid valve, and further configured so that pressurization of fuel in the plunger chamber is terminated when the plunger rises. (2) It is determined whether or not the pressure change rate of the common rail has become positive in the open state of the solenoid valve due to non-energization during the normal control of the variable discharge amount high pressure pump according to claim 1; A method for controlling a variable discharge high pressure pump, characterized in that when it is determined to be positive, the solenoid valve is always energized and the solenoid valve is kept closed. (3) In the variable discharge high pressure pump according to claim 1, when the diesel engine is started, the solenoid valve is not synchronized with the rotation of the engine instead of the normal control, and the energized time T1 and the non-energized time T2 are set to the solenoid valve. Controlling the variable discharge high pressure pump. (4) The control method for a variable discharge amount high pressure pump according to claim 3, wherein the energization time T1 and the non-energization time T2 are controlled by the following formula. T1 = T3 + TC Here, T3: the time required for the plunger to rise from its bottom dead center and reach the pressure at which the solenoid valve is maintained closed at the lowest engine speed at engine start. TC: Valve closing time delay after energizing the solenoid valve. Qmax: maximum discharge amount from the high-pressure pump. C: Constant determined by fuel viscosity and the like. S: fuel passage area. Pf: supply fuel pressure. Pk: plunger chamber pressure. T0: Delay of valve opening time after de-energization of solenoid valve.