High-pressure pump

Abstract

To make the time to fill the inside of a high-pressure pump with fuel, shorter than before.SOLUTION: A high-pressure pump 5 comprises a cam 50 for reciprocating a plunger 52 for pumping fuel, a cam chamber 51 housing the cam 50, a low-pressure pump 3 for supplying the fuel to the cam chamber 51, and an overflow valve 60. The overflow valve 60 comprises a first valve device 71 to be opened by fuel pressure in the cam chamber 51, and a second valve device 75 arranged in the first valve device 71, and to be opened by fuel pressure on the upstream side of the low-pressure pump 3. When the inside of the high-pressure pump 5 is filled with the fuel, the fuel is supplied to the inside of the high-pressure pump 5 via a first path passing through the low-pressure pump 3, and a second path branching from the upstream side of the low-pressure pump 3, and passing through the overflow valve 60, the first valve device 71 is opened by fuel pressure in the cam chamber 51, and the second valve device 75 is opened by fuel pressure in the second path before the opening of the first valve device 71.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a high-pressure pump provided with an overflow valve for lubricating the interior with fuel and preventing the internal fuel pressure from becoming excessive.

Background Art

[0002] Conventionally, a direct-injection internal combustion engine provided with a fuel injection valve that directly injects fuel into a combustion chamber of an internal combustion engine is known. In particular, when the direct-injection internal combustion engine is a diesel engine, a common-rail fuel injection control device is widely used.

[0003] The common-rail fuel injection control device includes a low-pressure pump that supplies fuel in a fuel tank to a high-pressure pump, a high-pressure pump that pumps the fuel supplied from the low-pressure pump to a common rail, a common rail that accumulates the high-pressure fuel pumped from the high-pressure pump, a fuel injection valve that injects the high-pressure fuel supplied from the common rail into a combustion chamber of the internal combustion engine, and a control device that receives outputs of various sensors and controls electronic control elements such as the high-pressure pump and the fuel injection valve. (See Patent Document 1)

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In accumulative fuel injection control systems, a so-called fuel-lubricated pump, whose internal lubrication is provided by fuel, is sometimes used as the high-pressure pump. In a fuel-lubricated high-pressure pump, fuel is supplied to the cam chamber, which houses the cam for driving the high-pressure pump. The fuel supplied to the cam chamber is used to lubricate the area around the cam and also reaches the pressurizing chamber for pumping the fuel. The fuel that reaches the pressurizing chamber is then pumped to the common rail by the reciprocating motion of a plunger driven by the cam.

[0006] A low-pressure pump is used to supply fuel to the high-pressure pump, including the cam chamber. In some cases, the low-pressure pump is located inside the high-pressure pump. In this case, the low-pressure pump operates using the driving force of the internal combustion engine, just like the high-pressure pump.

[0007] When a fuel-lubricated pump is used as the high-pressure pump in a pressure-accumulator-type fuel injection control system, the inside of the high-pressure pump needs to be filled with fuel after the pressure-accumulator-type fuel injection control system is installed in the vehicle during the manufacturing stage, but before the first operation of the internal combustion engine. At this time, an external, electrically operated pump is connected to the fuel inlet of the high-pressure pump, and this electric pump fills the inside of the high-pressure pump with fuel.

[0008] In this case, if the low-pressure pump is located inside the high-pressure pump, the fuel supplied to the high-pressure pump by the electric pump reaches the cam chamber via the first and second paths described below. The first path is the path through which the fuel reaches the cam chamber after passing through the low-pressure pump. The second path is the path through which the fuel reaches the cam chamber after passing through an overflow valve that opens due to the fuel pressure inside the cam chamber.

[0009] However, the second path does not function as a fuel supply route until the fuel pressure in the cam chamber has risen to a certain level and the overflow valve has opened. Therefore, until the overflow valve opens, fuel is supplied to the cam chamber only by the first path. In this case, the low-pressure pump acts as resistance to fuel supply to the cam chamber in the first path. Thus, in fuel-lubricated high-pressure pumps equipped with an internal low-pressure pump, there was a problem that the time required for the process of filling the high-pressure pump with fuel using an electric pump became longer.

[0010] Furthermore, when restarting a vehicle after running out of fuel in the market, a manual pump called a hand primer is used to supply fuel to the high-pressure pump. Even then, as during the manufacturing process, there was a problem with the time it took to supply fuel to the high-pressure pump being prolonged. The same problem also occurred when the high-pressure pump was replaced at auto repair shops or dealerships.

[0011] This invention was made against the backdrop of the above-mentioned problems, and aims to shorten the time required to fill the inside of a fuel-lubricated high-pressure pump with fuel using an external device, in a fuel-lubricated high-pressure pump equipped with a low-pressure pump inside, compared to conventional methods. [Means for solving the problem]

[0012] According to the present invention, a high-pressure pump is provided, comprising a plunger for pressurizing fuel, a cam for reciprocating the plunger, a cam chamber housing the cam, a low-pressure pump for supplying fuel to the cam chamber, and an overflow valve, wherein the overflow valve comprises a first valve device that opens due to the fuel pressure in the cam chamber, and a second valve device disposed within the first valve device that opens due to the fuel pressure upstream of the low-pressure pump, and when the inside of the high-pressure pump is filled with fuel by an external device, the fuel is supplied to the inside of the high-pressure pump via a first path that passes through the low-pressure pump and a second path that branches off from the upstream side of the low-pressure pump and passes through the overflow valve, the first valve device opens when the fuel pressure in the cam chamber reaches a predetermined pressure, and the second valve device opens due to the fuel pressure in the second path before the first valve device opens. [Effects of the Invention]

[0013] According to the present invention, in a fuel-lubricated high-pressure pump equipped with an internal low-pressure pump, it is possible to shorten the time required to fill the inside of the high-pressure pump with fuel using an external device. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram showing an example configuration of a pressure-accumulating fuel injection control device 1 equipped with a high-pressure pump 5 according to an embodiment of the present invention. [Figure 2] This is a cross-sectional view of an overflow valve 60 according to an embodiment of the present invention. [Figure 3] This is a magnified view of a portion of Figure 2. [Figure 4] This is a diagram showing the cross-section of BB (Ballpoint of BB) as shown in Figure 3. [Figure 5] This diagram illustrates the operation of the overflow valve 60 when fuel is being supplied from the external device 29 to the high-pressure pump 5. [Figure 6] This diagram illustrates the operation of the overflow valve 60 when fuel is being supplied from the external device 29 to the high-pressure pump 5. [Figure 7]It is a diagram for explaining the operation of the overflow valve 60 when fuel is filled from the external device 29 into the high-pressure pump 5. [Figure 8] It is a diagram for explaining the conventional overflow valve 600. [Figure 9] It is a diagram for explaining the conventional overflow valve 600. [Figure 10] It is a diagram showing the pressure increase in the cam chamber 51 in the conventional and the present invention.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described with appropriate reference to the drawings. Note that the members, arrangements, etc. described below do not limit the present invention, and various modifications can be made within the scope of the gist of the present invention. Also, in each drawing, the same reference numerals indicate the same elements, and the description is omitted as appropriate. In addition, in each drawing, the illustration of the detailed part is appropriately simplified or omitted. Also, duplicate descriptions are appropriately simplified or omitted.

[0016] FIG. 1 is a schematic diagram showing a configuration example of a pressure accumulator type fuel injection control device 1 including a high-pressure pump 5 according to an embodiment of the present invention. The pressure accumulator type fuel injection control device 1 is a device that injects fuel into an internal combustion engine (not shown). The pressure accumulator type fuel injection control device 1 includes a fuel tank 2, a high-pressure pump 5, a common rail 6, a fuel injection valve 7, and a control device (ECU) 10. The high-pressure pump 5 according to the present embodiment includes a low-pressure pump 3 that sucks up the fuel in the fuel tank 2 inside.

[0017] The fuel tank 2 and the low-pressure pump 3 provided in the high-pressure pump 5 are connected by a low-pressure fuel passage 12. The high-pressure pump 5 and the common rail 6 are connected by a high-pressure fuel passage 13. The common rail 6 and the fuel injection valve 7 are connected by a high-pressure fuel passage 14. Return passages 16, 17, and 18 for returning surplus fuel to the fuel tank 2 are respectively connected to the high-pressure pump 5, the common rail 6, and the fuel injection valve 7. Also, a fuel filter 22 is provided between the fuel tank 2 and the high-pressure pump 5.

[0018] In FIG. 1, the portion indicated by the two-dot chain line indicates the high-pressure pump 5. The high-pressure pump 5 and the low-pressure pump 3 provided inside the high-pressure pump 5 both operate by the driving force of an internal combustion engine (not shown). The low-pressure pump 3 supplies the fuel pumped up from the fuel tank 2 to the cam chamber 51 via the passage 3a. The cam chamber 51 houses a cam 50 for driving the plunger 52 of the high-pressure pump 5. In the present embodiment, a gear pump is used as the low-pressure pump 3.

[0019] The fuel supplied to the cam chamber 51 is used for lubricating the cam chamber 51 and is also supplied to the pressurizing chamber 53 via the passage 51a. The fuel supplied to the pressurizing chamber 53 is pressure-fed to the common rail 6 by the reciprocating motion of the plunger 52 driven by the cam 50. In FIG. 1, only one plunger 52 is depicted, but a plurality of plungers 52 may be provided.

[0020] Also, a part of the fuel supplied to the cam chamber 51 is used for lubricating bearings 24 etc. around the cam chamber 51 and is then discharged via the passage 16a. The return fuel of the low-pressure pump 3 is discharged via the passage 16b. The fuel discharged to the passage 16a and the fuel discharged to the passage 16b are returned to the fuel tank 2 via the return passage 16.

[0021] Between the cam chamber 51 and the pressurizing chamber 53, there is a flow control valve 54 that adjusts the flow rate of fuel supplied to the pressurizing chamber 53 by the high-pressure pump 5. As the flow control valve 54, for example, an electromagnetic proportional control valve is used, in which the stroke amount of the valve body is adjusted by the magnitude of the supplied current value, thereby varying the area of ​​the port through which the fuel passes. The flow control valve 54 is used to control the fuel pressure inside the common rail 6 (hereinafter also referred to as rail pressure) by adjusting the flow rate of fuel supplied to the pressurizing chamber 53. In other words, the rail pressure becomes the pressure of the fuel injected from the fuel injection valve 7. The energization control of the flow control valve 54 is performed by the control device 10.

[0022] A zero-delivery throttle 55 is connected between the flow control valve 54 and the pressurizing chamber 53. When the required fuel delivery amount from the high-pressure pump 5 is zero, the fuel passing through the flow control valve 54 is restricted to the maximum extent, but even in this case, a small amount of fuel may still pass through the flow control valve 54. At this time, the small amount of fuel that has passed through the flow control valve 54 is discharged into the passage 55a through the zero-delivery throttle 55 and returned to the fuel tank 2 via the return passage 16.

[0023] An overflow valve 60 is connected between the flow control valve 54 and the cam chamber 51. During normal operation of the accumulator-type fuel injection control device 1, the overflow valve 60 discharges the fuel in the cam chamber 51 to the outside of the cam chamber 51 when the fuel pressure in the cam chamber 51 becomes excessive. In other words, the overflow valve 60 maintains the fuel pressure in the cam chamber 51 within a predetermined range. Also, when fuel is filled into the high-pressure pump by an external device, such as when the high-pressure pump 5 is started to be used, the fuel passes through the overflow valve 60. Details of the overflow valve 60 will be described later.

[0024] The common rail 6 temporarily stores high-pressure fuel pumped from the high-pressure pump 5 and supplies high-pressure fuel to the fuel injection valve 7. A rail pressure sensor 21 is attached to the common rail 6 for measuring rail pressure. The sensor signal from the rail pressure sensor 21 is sent to the control device 10 and used for controlling the rail pressure.

[0025] The common rail 6 is equipped with a mechanical safety valve 23. During normal operation, the safety valve 23 is closed when its valve body, subjected to a predetermined set force by a spring, seats on the seat. The safety valve 23 opens when the rail pressure exceeds the opening pressure of the safety valve 23, and the fuel in the common rail 6 is discharged into the return passage 17.

[0026] A fuel injector 7 is provided in each cylinder of an internal combustion engine (not shown). The fuel injector 7 comprises a nozzle body with an injection hole and a needle valve that closes the injection hole. The fuel injector 7 is configured such that the back pressure acting on the rear end of the needle valve is released by the power supply control of the back pressure control unit by the control device 10, thereby opening the injection hole and injecting fuel into the cylinder of the internal combustion engine (not shown).

[0027] The fuel injector 7 may be, for example, an electromagnetically controlled fuel injector equipped with a solenoid valve as a back pressure control unit, or an electrostrictive fuel injector equipped with a piezoelectric element as a back pressure control unit. The fuel injector 7 discharges the dynamically leaked fuel generated by the back pressure control of the needle valve and the statically leaked fuel leaking from the sliding parts such as the needle valve into the return passage 18.

[0028] An external device 29 is connected between the fuel filter 22 and the high-pressure pump 5. In this embodiment, the external device 29 is an electric pump. The external device 29 is used to fill the inside of the high-pressure pump 5 with fuel after the accumulator-type fuel injection control device 1 is assembled to the vehicle during the manufacturing stage. Therefore, the external device 29 is removed after the inside of the high-pressure pump 5 has been filled with fuel. Also, when restarting after running out of gas, or when the high-pressure pump 5 is replaced at a repair shop or dealer, a manual pump called a hand primer is used as the external device 29 instead of the electric pump, and the inside of the high-pressure pump 5 is filled with fuel.

[0029] Next, an overflow valve 60 provided in the high-pressure pump 5 according to an embodiment of the present invention will be described. Figure 2 is a cross-sectional view of the overflow valve 60 according to an embodiment of the present invention. The overflow valve 60 comprises a housing 61, a first valve device 71, and a second valve device 75.

[0030] The housing 61 is formed in a hollow cylindrical shape and has a through hole 62 that penetrates axially. The housing 61 houses the first valve gear 71 and the second valve gear 75, which will be described later, inside the through hole 62. The first valve gear 71 and the second valve gear 75 are operated by fuel pressure.

[0031] The first valve device 71 comprises a first valve body 72, a first spring 80, a plug 81, and a cap 82. The cap 82 is mounted on one end of the housing 61. The cap 82 has an axial opening 83 that penetrates axially. The axial opening 83 communicates with the cam chamber 51 via a passage 51a (see Figure 1). The cap 82 is mounted on the housing 61 by welding, crimping, or any other appropriate method.

[0032] The first valve body 72 is slidably held within the through hole 62 of the housing 61. The other end of the first valve body 72 abuts against one end of the first spring 80. The other end of the first spring 80 abuts against the plug 81.

[0033] The plug 81 is press-fitted into the through-hole 62 from the other end of the housing 61. The plug 81 is press-fitted in a position where the first spring 80 applies a predetermined set force to the first valve body 72. Thus, the area between the first valve body 72 and the plug 81 in the through-hole 62 of the housing 61 becomes a spring chamber 62a that houses the first spring 80.

[0034] The second valve device 75 comprises a second valve body 76, a second spring 77, and a support member 74. The second valve body 76, the second spring 77, and the support member 74 are housed in a housing hole 73e formed in the first valve body 72. The housing hole 73e is formed as an axial hole with one end opening toward the cap 82. A seat surface 72c is formed at the other end of the housing hole 73e, on which the second valve body 76 sits when the second valve device 75 is closed.

[0035] The second valve body 76 is slidably held within the housing hole 73e of the first valve body 72. One end of the second spring 77 abuts against the support member 74. The support member 74 is a hollow disc shape and is fixed to one end of the housing hole 73e by welding, press-fitting, or other appropriate method. The other end of the second spring 77 abuts against the second valve body 76. The second spring 77 presses the second valve body 76 against the seat surface 72c.

[0036] The housing 61 is formed radially and includes a first opening 63 that connects the through hole 62 to the outside of the housing 61. The first opening 63 communicates with the upstream side of the low-pressure pump 3 within the high-pressure pump 5 via a passage 63a (see Figure 1). The housing 61 is formed radially on the other end of the first opening 63 and includes a second opening 64 that connects the through hole 62 to the outside of the housing 61. The second opening 64 communicates with the return passage 16 of the high-pressure pump 5 (see Figure 1).

[0037] In this embodiment, four first openings 63 are formed at 90-degree intervals in the axial view of the housing 61, but the number is not limited to four. Also, if multiple first openings 63 are formed, all of the first openings 63 communicate with the passage 63a of the high-pressure pump 5.

[0038] Furthermore, although one second opening 64 is formed in this embodiment, the number is not limited to one, and multiple openings may be formed. When multiple second openings 64 are formed, all of the second openings 64 are connected to the return passage 16 of the high-pressure pump 5.

[0039] Figure 3 is a partially enlarged view of the region indicated by A in Figure 2. Figure 4 is a view of the BB cross section in Figure 3. The first valve gear 71 and the second valve gear 75 will be further described below with reference to Figures 3 and 4.

[0040] As shown in Figure 3, the second valve body 76 comprises a seating portion 76a, a connecting portion 76b, a valve body guide portion 76c, and a second spring guide portion 76d. The seating portion 76a seats on the seat surface 72c formed in the housing hole 73e of the first valve body 72 when the second valve device 75 is closed. The valve body guide portion 76c has its outer circumference in contact with the inner circumferential surface of the housing hole 73e and guides the second valve body 76 as the second valve body slides within the housing hole 73e. The connecting portion 76b is a conical portion that connects the seating portion 76a and the valve body guide portion 76c. The second spring guide portion 76d is a cylindrical projection formed on the cap 82 side end face of the valve body guide portion 76c. The valve body guide portion 76c guides the second spring 77 by fitting inside the second spring 77. Furthermore, the valve body guide portion 76c has multiple grooves formed on its outer surface, allowing fuel to pass through these grooves.

[0041] A first communication hole 73a is formed in the axial center of the first valve body 72, with one end communicating with the housing hole 73e at the center of the seat surface 72c. The diameter of the first communication hole 73a is smaller than the seat diameter when the second valve body 76 is seated on the seat surface 72c. That is, when the second valve body is closed, the second valve body 76 is seated on the seat surface 72c, blocking communication between the housing hole 73e and the first communication hole 73a. The other end of the first communication hole 73a communicates with a second communication hole 73b that penetrates the first valve body 72 radially. When one end of the first valve body 72 is in contact with the cap 82, the radial opening of the second communication hole 73b, i.e., the opening on the outer circumferential surface of the first valve body 72, communicates with the first opening 63 of the housing 61.

[0042] Furthermore, in the through hole 62 of the housing 61, in the portion where the first opening 63 is formed, an enlarged diameter portion 65 is formed, which has an enlarged inner diameter in a region that is longer in the axial direction than the diameter of the first opening 63. Because of the formation of the enlarged diameter portion 65, even if there is a phase difference between the radial opening of the second communication hole 73b and the first opening 63 of the housing 61 in the circumferential direction, the second communication hole 73b and the first opening 63 are reliably in communication.

[0043] Furthermore, as shown in Figure 4, a third communication hole 73c is formed in the first valve body 72 in the axial direction at a portion away from the central axis. In this embodiment, two third communication holes 73c are formed. One end of the third communication hole 73c communicates with the housing hole 73e. The third communication hole 73c communicates with the housing hole 73e at a point radially outward from the seat diameter when the second valve body 76 is seated on the seat surface 72c. The other end of the third communication hole 73c communicates with a fourth communication hole 73d that penetrates the first valve body radially. Here, the radial opening of the fourth communication hole 73d, that is, the opening on the outer circumferential surface of the first valve body 72, is located on the other end side of the first valve body 72, beyond the enlarged diameter portion 65, when one end of the first valve body 72 is in contact with the cap 82, and does not communicate with the first opening 63.

[0044] Furthermore, in this embodiment, the plane containing the central axes of the first communication hole 73a and the second communication hole 73b (hereinafter also referred to as the first plane) and the plane containing the central axes of the third communication hole 73c and the fourth communication hole 73d (hereinafter also referred to as the second plane) are formed to be perpendicular to each other. However, the first plane and the second plane do not have to be perpendicular to each other; it is sufficient that the communication holes with their central axes on the first plane (first communication hole 73a and the second communication hole 73b) and the communication holes with their central axes on the second plane (third communication hole 73c and the fourth communication hole 73d) are formed so that they do not intersect.

[0045] Figures 5 to 7 illustrate the operation of the overflow valve 60 when fuel is supplied to the high-pressure pump 5 from the external device 29. When fuel is supplied to the high-pressure pump 5 from the external device 29, the fuel is supplied via a first path through the low-pressure pump 3 to the cam chamber 51, and a second path through which the fuel branches upstream of the low-pressure pump 3 and reaches the cam chamber 51 via the overflow valve 60.

[0046] Before the external device 29 is driven, the first valve device 71 and the second valve device 75 are closed. Specifically, in the first valve device 71, one end of the first valve body 72 is in contact with the cap 82, and in the second valve device 75, the second valve body 76 is seated on the seat surface 72c.

[0047] When the external device 29 is started to operate, fuel is supplied to the cam chamber 51 via the low-pressure pump 3 in the first path. At this time, the low-pressure pump 3 is not operating, so the fuel passes through the gap of the gear pump of the low-pressure pump 3 to reach the cam chamber 51.

[0048] On the other hand, in the second path, fuel is supplied to the first opening 63 formed in the housing 61 of the overflow valve 60 via a passage 63a branched from the inlet side of the low-pressure pump 3. The fuel supplied to the first opening 63 reaches the first communication hole 73a via the second communication hole 73b formed in the first valve body 72. At this time, since there is no resistance caused by the low-pressure pump 3 in the second path, the fuel pressure supplied from the external device 29 acts on the first communication hole 73a. Furthermore, the opening pressure of the second valve device 75 is set lower than the fuel pressure that reaches the first communication hole 73a, in other words, the fuel pressure supplied by the external device 29. Therefore, the fuel that reaches the first communication hole 73a opens the second valve device 75 due to its fuel pressure and reaches the cam chamber 51 via the housing hole 73e, the axial opening 83 of the cap 82, and the passage 51a (see Figures 1 and 5).

[0049] Therefore, the fuel pressure in the cam chamber 51 increases due to the fuel supplied through the first and second paths. Subsequently, the first valve body 72 begins to stroke (move downwards in the plane of Figure 5) due to the fuel pressure in the cam chamber 51 received at the bottom surface 73f on the other end side (first spring 80 side) of the housing hole 73e and the seat surface 72c radially inward of the bottom surface 73f.

[0050] Subsequently, when the stroke of the first valve body 72 reaches the position shown in Figure 6, communication between the second communication hole 73b of the first valve body 72 and the first opening 63 of the housing 61 is blocked. As a result, fuel supply from the external device 29 to the first communication hole 73a is cut off. After that, the fuel pressure on the cam chamber 51 side continues to rise due to the fuel supplied from the first path. Then, the difference between the fuel pressure on the first communication hole 73a side and the fuel pressure on the cam chamber 51 side, with the second valve body 76 in between, decreases, and eventually the resultant force of the fuel pressure on the cam chamber 51 side acting on the second valve body 76 and the biasing force of the second spring 77 exceeds the force of the fuel pressure on the first communication hole 73a side acting on the second valve body, and the second valve device 75 closes.

[0051] Even after the second valve gear 75 closes, the fuel pressure in the cam chamber 51 continues to rise due to the fuel supplied from the external device 29 via the first path. Therefore, the first valve body 72 continues to stroke.

[0052] Figure 7 is a cross-sectional view of the overflow valve 60 from the same direction as in Figure 4. As the stroke of the first valve body 72 continues, as shown in Figure 7, the region between the first valve body 72 and the cap 82 in the through hole 62, formed by the stroke of the first valve body 72, communicates with the first opening 63 of the housing 61. That is, the first opening 63 communicates with the cam chamber 51. In other words, the first valve device 71 opens. At this time, fuel is again supplied from the external device 29 to the cam chamber 51 through the first opening 63.

[0053] At this time, the flow path area formed by the communication between the region between the first valve body 72 and the cap 82 in the through hole 62 and the first opening 63 of the housing 61 is larger than the flow path area formed by the opening of the second valve device 75. Therefore, after the stroke of the first valve body reaches the state shown in Figure 7, the fuel pressure in the cam chamber 51 rises rapidly compared to when fuel was supplied to the cam chamber 51 via the second valve device 75.

[0054] Furthermore, in the state shown in Figure 7, the fourth communication hole 73d of the first valve body 72 is in communication with the spring chamber 62a that houses the first spring 80. That is, the housing hole 73e of the first valve body 72 and the spring chamber 62a are in communication with the third communication hole 73c and the fourth communication hole 73d of the first valve body 72.

[0055] Since the spring chamber 62a is in communication with the return passage 16 of the high-pressure pump 5 via the second opening 64 of the housing 61, the pressure inside the spring chamber 62a is lower than that inside the housing hole 73e. Therefore, the communication between the fourth communication hole 73d and the spring chamber 62a creates a fuel flow from the first opening 63 to the return passage 16 via the housing hole 73e, the third communication hole 73c, the fourth communication hole 73d, and the second opening 64. This flow is used to vent air from inside the overflow valve 60. In other words, the third communication hole 73c and the fourth communication hole 73d function as air vents for discharging air from inside the overflow valve 60 to the outside.

[0056] Furthermore, during normal operation of the accumulator-type fuel injection control device 1, the overflow valve 60 functions to maintain the fuel pressure in the cam chamber 51 within a predetermined range. That is, when the fuel pressure in the cam chamber 51 becomes excessive, the first valve body 72 of the overflow valve 60 strokes against the set force of the first spring 80, and the fuel in the cam chamber 51 is discharged from the first opening 63 and the second opening.

[0057] Next, a conventional overflow valve 600 will be described as a comparative example. Figures 8 and 9 are diagrams illustrating the conventional overflow valve 600. The conventional overflow valve 600 comprises a housing 610 and a valve device 700. The valve device 700 comprises a valve body 720, a spring 80, a plug 81, and a cap 82.

[0058] The valve body 720 is provided with an axial hole 730 that is open at one end (the side facing the cap 82). The other end of the axial hole 730 is closed in the axial direction, and a communication hole 731 is formed in the radial direction. The communication hole 731 is a radial hole drilled from the outer circumferential surface of the valve body 720 and leading to the axial hole 730.

[0059] When the external device 29 begins to fill the high-pressure pump 5 with fuel, the fuel is sent to the cam chamber 51 via the low-pressure pump 3. On the other hand, when the valve body 720 is not in stroke, the radially outer end of the communication hole 731 is closed by the inner surface of the axial through hole 62 formed in the housing 610. Therefore, fuel is not supplied to the cam chamber 51 via the overflow valve 600.

[0060] Subsequently, as the fuel pressure in the cam chamber 51 increases, the valve body 720 strokes, and when it reaches the state shown in Figure 9, the region between the valve body 720 and the cap 82 in the through hole 62, formed by the stroke of the valve body 720, communicates with the first opening 63 of the housing 610. In other words, the first opening 63 and the cam chamber 51 communicate. In other words, at this time, the second path is established. After this, the fuel pressure in the cam chamber 51 rises rapidly.

[0061] At this time, the axial hole 730 of the valve body 720 communicates with the spring chamber 62a via the communication hole 731. As a result, a fuel flow is generated from the first opening 63, through the axial hole 730, the communication hole 731, the spring chamber 62a, and the second opening 64 to the return passage 16. This flow is used to bleed air from inside the overflow valve 600.

[0062] In the conventional overflow valve 600, until the stroke of the valve body 720 reaches the state shown in Figure 9, that is, until the first opening 63 and the cam chamber 51 are in communication, the only fuel supply path from the external device 29 to the cam chamber 51 is the path (first path) that goes to the cam chamber 51 via the low-pressure pump 3.

[0063] Figure 10 shows the pressure rise in the cam chamber 51 in the conventional and in the present invention when fuel is supplied to the high-pressure pump 5 from the external device 29.

[0064] In Figure 10, the vertical axis represents the fuel pressure in the cam chamber 51, and the horizontal axis represents the operating time of the external device 29. Also in Figure 10, the dashed line represents the pressure increase when the conventional overflow valve 600 is used, and the solid line represents the pressure increase when the overflow valve 60 according to the present invention is used. On the vertical axis, p1 represents the target fuel pressure in the cam chamber 51 when the external device 29 fills the high-pressure pump 5 with fuel.

[0065] First, let's explain the case where a conventional overflow valve 600 is used. When the external device 29 is started to operate at time t0, the fuel pressure in the cam chamber 51 rises until time t3, and at time t3, the pressure becomes p0. During this time, fuel is supplied to the cam chamber 51 only through the first path via the low-pressure pump 3.

[0066] At time t3, the first opening 63 of the housing 610 and the cam chamber 51 are in communication. That is, the second path is established. The fuel pressure in the cam chamber 51 then rises rapidly and reaches the target pressure p1.

[0067] Next, we will describe the case in which the overflow valve 60 of the present invention is used. When the external device 29 is started to operate at time t0, fuel is supplied to the cam chamber 51 from both the first path via the low-pressure pump 3 and the second path via the second valve device 75 of the overflow valve 60.

[0068] Then, at time t1, the second valve device 75 closes. Therefore, after time t1, the second path is temporarily closed, and fuel is supplied to the cam chamber 51 only from the first path, causing the rate of increase in fuel pressure in the cam chamber 51 to decrease temporarily. Then, at time t2, the fuel pressure in the cam chamber 51 becomes P0, and the first opening 63 of the housing 61 and the cam chamber 51 communicate. That is, the second path communicates again. Then, the fuel pressure in the cam chamber 51 rapidly increases and reaches the target pressure p1. Note that the fuel pressure in the cam chamber 51 when the first opening 63 and the cam chamber 51 communicate corresponds to the predetermined pressure in this invention.

[0069] When the overflow valve 60 of the present invention is used, fuel is supplied to the cam chamber 51 from both the first and second paths between time t0 and time t1. Therefore, the rate of pressure rise in this section is faster than in the conventional method.

[0070] When time t1 is reached, the second path is closed, and fuel is supplied to the cam chamber 51 only through the first path, thus reducing the rate of pressure rise in the cam chamber 51. Therefore, the slopes of the solid line and the dashed line coincide between time t1 and time t2. However, since the rate of pressure rise between time t0 and time t1 is faster in the present invention, the time until the first opening 63 and the cam chamber 51 communicate is faster in the present invention than in the conventional invention. Therefore, the time until the fuel pressure in the cam chamber 51 reaches the target pressure P1 is faster in the present invention than in the conventional invention.

[0071] As described above, by using the overflow valve 60 of the present invention, the time required to fill the high-pressure pump 5 with fuel using the external device 29 during the vehicle manufacturing stage can be shortened.

[0072] Furthermore, since the housing 61 of the overflow valve 60 according to the present invention can be manufactured by adding a process to form an enlarged diameter portion 65 around the first opening 63 compared to conventional products, there is no need to make major changes to the manufacturing process for the housing 61 according to the present invention. [Explanation of symbols]

[0073] 1: Accumulator-type fuel injection control device, 3: Low-pressure pump, 5: High-pressure pump, 29: External device, 50: Cam, 51: Cam chamber, 52: Plunger, 60: Overflow valve, 71: First valve device, 72: First valve body, 75: Second valve device, 76: Second valve body, 73a: First communication hole, 73b: Second communication hole, 73c: Third communication hole (air vent hole), 73d: Fourth communication hole (air vent hole)

Claims

1. A plunger (52) for pressurizing fuel, A cam (50) that causes the plunger (52) to reciprocate, A cam chamber (51) housing the cam (50), A low-pressure pump (3) that supplies fuel to the cam chamber (51), Overflow valve (60), In a high-pressure pump (5) equipped with, The overflow valve (60) is A first valve device (71) that opens due to the fuel pressure in the cam chamber (51), The system comprises a second valve device (75) located within the first valve device (71) and opened by the fuel pressure upstream of the low-pressure pump (3), When fuel is filled into the high-pressure pump (5) by the external device (29), The fuel is supplied into the high-pressure pump (5) via a first path that passes through the low-pressure pump (3) and a second path that branches off from the upstream side of the low-pressure pump (3) and passes through the overflow valve (60). When the fuel pressure in the cam chamber (51) reaches a predetermined pressure, the first valve device (71) opens. The second valve device (75) opens due to the fuel pressure in the second passage before the first valve device (71) opens. High-pressure pump (5).

2. The high-pressure pump according to claim 1, wherein the first valve device (71) is provided with air vents (73c, 73d) for discharging air from the overflow valve (60) to the outside.

3. The high-pressure pump (5) according to claim 1, wherein the external device (29) is an electric pump that supplies fuel into the high-pressure pump (5) after the high-pressure pump (5) has been assembled to the vehicle during the manufacturing stage.

4. The high-pressure pump according to claim 1, wherein the external device (29) is a manual pump that supplies fuel into the high-pressure pump (5) when the engine is restarted after running out of gas or after the high-pressure pump (5) has been replaced.

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