Fuel supply pump

Abstract

The fuel supply pump includes a positive displacement feed pump (30, 50) and a high pressure pump (60) that pressurizes and pumps the fuel pumped from the feed pump. The high pressure pump includes a plunger (64) that reciprocates in a pressurization chamber (110) and a metering valve (66) that opens to open a fuel inlet side of the pressurization chamber through which the fuel pumped from the feed pump is sucked, and closes to close the fuel inlet side. The metering valve meters the amount of fuel pumped from the pressurization chamber by controlling the closing timing of the metering valve so that the metering valve is closed during a pumping stroke of the high pressure pump in which the plunger moves upward. The phase of a pumping cycle in which the feed pump pumps the fuel is synchronized with the phase of a suction cycle in which the high pressure pump sucks the fuel into the pressurization chamber.

Description

Technical Field

[0001] The present disclosure relates to a technology in which a high-pressure pump pressurizes and pumps fuel pumped from a positive displacement feed pump. Background Art

[0002] There is known a technology in which fuel pumped from a positive displacement feed pump is sucked into a pressurizing chamber of a high-pressure pump by reciprocating motion of a plunger and pressurized therein to be pumped from the high-pressure pump.

[0003] For example, Patent Document 1 (DE 102009028164 A1) discloses a gear pump as a positive displacement feed pump in which external teeth of two gears mesh with each other and rotate, whereby the gear pump pumps fuel to a high-pressure pump.

[0004] The amount of fuel pumped from the high pressure pump is metered, for example, by a pre-stroke method that controls the closing moment of a metering valve during a pumping stroke when the high pressure pump plunger is lifted. The metering valve is arranged on the fuel inlet side of the pressurization chamber. Summary of the invention

[0005] As disclosed in Patent Document 1, in a positive displacement feed pump, the pressure of the fuel pumped from the feed pump to the high-pressure pump repeatedly increases and decreases. When the fuel pressure changed in this way is low, and the fuel is sucked into the boosting chamber during the suction stroke in which the plunger moves downward, the amount of fuel sucked into the boosting chamber decreases, and this poor suction causes negative pressure in the boosting chamber.

[0006] In particular, in the high speed rotation range of the engine, the time required for the suction stroke becomes shorter, thereby further reducing the amount of fuel sucked into the supercharging chamber. As a result, the supercharging chamber forms a negative pressure.

[0007] If the metering valve is closed when the pressure in the boosting chamber is negative due to poor suction of the fuel in the boosting chamber, water hammer pressure occurs and pressure pulsation is generated on the fuel inlet side of the boosting chamber. According to detailed studies by the inventors of the present application, a problem has been found that this pressure pulsation causes a large pressure change applied to the components constituting the fuel supply system that supplies the fuel from the feed pump to the boosting chamber. In addition, a problem has been found that the amount of fuel pumped by the high-pressure pump is reduced due to poor suction of the fuel in the boosting chamber.

[0008] In the technology described in Patent Document 1, a damper is arranged in parallel with a feed pump in a fuel supply system on the fuel inlet side of a pressurizing chamber, and reduces pressure pulsation generated on the fuel inlet side of the pressurizing chamber.

[0009] However, if a damper is provided to suppress the pressure pulsation generated on the fuel inlet side of the boost chamber as in the technique described in Patent Document 1, the number of components increases. Furthermore, even if a damper is installed to reduce the pressure pulsation generated on the fuel inlet side of the boost chamber, the problem of a reduction in the amount of fuel pumped from the high-pressure pump due to poor fuel suction in the boost chamber is not solved.

[0010] In one aspect of the present disclosure, it is desirable to provide a technique for reducing poor ingestion of fuel into a boost chamber without adding new components.

[0011] According to one aspect of the present disclosure, a fuel supply pump includes a positive displacement feed pump, and a high-pressure pump pressurizes and pumps fuel pumped from the feed pump.

[0012] The high-pressure pump includes a plunger that reciprocates by the rotation of the cam and draws the fuel pumped from the feed pump into the pressurization chamber and pressurizes it. The high-pressure pump includes a metering valve that opens to open the fuel inlet side of the pressurization chamber through which the fuel pumped from the feed pump is sucked, and closes to close the fuel inlet side. The metering valve meters the amount of fuel pumped from the pressurization chamber by controlling the closing timing of the metering valve so that the metering valve is closed during the pumping stroke when the plunger of the high-pressure pump moves upward. The phase of the pumping cycle of the feed pump pumping the fuel is synchronized with the phase of the suction cycle of the high-pressure pump sucking the fuel into the pressurization chamber.

[0013] According to this aspect, the pumping cycle of the feed pump and the suction cycle of the high-pressure pump are synchronized so that the feed pump pumps fuel according to the suction stroke in which the plunger of the high-pressure pump moves downward and sucks in the fuel. Therefore, the bad suction of the fuel in the boosting chamber during the suction stroke of the high-pressure pump can be reduced without additional components. Therefore, the generation of negative pressure in the boosting chamber can be reduced.

[0014] As a result, even if the metering valve is closed to meter the amount of fuel in the pumping stroke, pressure pulsation generated in the fuel supply system that supplies the fuel from the feed pump to the pressurizing chamber can be reduced.

[0015] Furthermore, since poor suction of fuel in the pressurizing chamber is reduced, a decrease in the amount of fuel pumped from the high-pressure pump can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a block diagram showing a fuel supply system according to a first embodiment.

[0017] Figure 2 is a schematic diagram showing the configuration of a feed pump.

[0018] Figure 3 is a schematic diagram showing the structure of a cam.

[0019] Figure 4 is a schematic diagram showing another configuration of the feed pump.

[0020] Figure 5 is a timing chart showing the pressure on the fuel inlet side of the pressurizing chamber and the degree of plunger lift.

[0021] Figure 6 is a characteristic diagram showing the relationship between the pressure pulsation and the phase difference between the start of the pumping chamber to suck in fuel and the completion of the feed pump's pumping.

[0022] Figure 7 is a block diagram showing a fuel supply system according to a second embodiment.

[0023] Figure 8 is a timing chart showing the pressure of the fuel pumped by the feed pump, the pressure on the fuel inlet side of the pressurizing chamber, and the plunger lift. DETAILED DESCRIPTION

[0024] Embodiments of the present disclosure will be described hereinafter with reference to the accompanying drawings. In the embodiments, the same reference numerals may be assigned to portions corresponding to the contents described in the previous embodiments, and repeated descriptions of the portions may be omitted. When only a portion of a structure is described in an embodiment, another previous embodiment may be applied to other portions of the structure. Even if it is not explicitly described that the portions may be combined, the portions may be combined. Even if it is not explicitly described that the embodiments may be combined, the embodiments may be partially combined as long as the combination is not detrimental.

[0025] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0026] [1. First embodiment]

[0027] [1-1. Structure]

[0028] like Figure 1 As shown, a fuel supply system 2 according to a first embodiment of the present invention supplies fuel to, for example, a common rail of a diesel engine (not shown). The fuel supply system 2 includes a fuel tank 4 and a fuel supply pump 10.

[0029] The fuel supply pump 10 includes housings 12, 14, a safety valve 22, a feed pump 30 and two high-pressure pumps 60. The number of the high-pressure pumps 60 may be one or more.

[0030] The safety valve 22 and the feed pump 30 are accommodated in the housing 12. When the pressure of the fuel pumped from the feed pump 30 exceeds a predetermined pressure, the safety valve 22 opens.

[0031] like Figure 2As shown, the feed pump 30 is a positive displacement cycloid gear pump. A positive displacement pump (positive displacement pump) is a pump that pumps fluid by changing the volume of a pump chamber according to reciprocating motion or rotary motion.

[0032] The feed pump 30 includes an external gear 32 and an internal gear 36. The external gear 32 has six external teeth 34 that protrude radially outward and are arranged at equal angular intervals. The angular position of the external gear 32 relative to the camshaft 6 in the rotational direction is determined by the key 6a of the camshaft 6 assembled to the inner circumference side of the external gear 32.

[0033] The inner gear 36 has seven inner teeth 38 which protrude radially inward and are arranged at equal angular intervals. The inner gear 36 is eccentrically mounted on the outer gear 32.

[0034] When the outer gear 32 rotates by the rotation of the camshaft 6, the inner gear 36 also rotates with the rotation of the outer gear 32. According to the increase or decrease of the volume formed between the outer gear 32 and the inner gear 36, the fuel sucked from the fuel tank through the suction port (not shown) of the feed pump 30 is pressurized and supplied to the fuel supply passage 100 leading to the high-pressure pump 60.

[0035] In the first embodiment, a fuel supply passage 100 for supplying fuel from the feed pump 30 to the high-pressure pump 60 is formed in the housings 12 , 14 .

[0036] like Figure 1 As shown, both high-pressure pumps 60 include a tappet 62 , a plunger 64 , a metering valve 66 , and a discharge valve 68 .

[0037] The tappets 62 of the two high-pressure pumps 60 are in contact with any one of the two cams 8 provided on the camshaft 6. Figure 3 As shown, each cam 8 has three cam ridges formed at equal angle intervals. Therefore, the total number of cam ridges of the two cams 8 is six. The two cams 8 are mounted on the camshaft 6 while being offset from each other by 60° in the rotation direction with respect to the positions of the cam ridges.

[0038] During one rotation of the camshaft 6 according to the rotation of the cam 8 , each tappet 62 reciprocates three times in the linear direction.

[0039] One end of the plunger 64 is attached to the tappet 62. The plunger 64 reciprocates together with the tappet 62. The other end of the plunger 64 is provided with a pressurizing chamber 110 for sucking the fuel pumped from the feed pump 30.

[0040] The metering valve 66 is a solenoid valve that is fully opened in the suction stroke in which the plunger 64 of the high-pressure pump 60 moves downward, and the closing timing of the metering valve 66 is controlled in the pumping stroke in which the plunger 64 is lifted. When the metering valve 66 is opened, the fuel inlet side of the pressurizing chamber 110 is opened. When the metering valve 66 is closed, the fuel inlet side of the pressurizing chamber 110 is closed.

[0041] The timing of opening and closing of the metering valve 66 is controlled by an electronic controller (not shown). When the plunger 64 is lifted in a state where the metering valve 66 is closed, the fuel in the pressurizing chamber 110 is pressurized.

[0042] The amount of fuel pumped from the high-pressure pump 60 is metered during the pumping stroke by the timing at which the metering valve 66 is closed. The earlier the metering valve 66 is closed during the pumping stroke, the more the amount of fuel pressurized in the pressurizing chamber 110 increases. Therefore, the pumping amount increases.

[0043] When the pressure in the pressurizing chamber 110 exceeds a predetermined pressure, the discharge valve 68 opens. When the discharge valve 68 opens, the fuel pressurized in the pressurizing chamber 110 passes through the fuel supply passage 120 and is pumped from the high pressure pump 60 to a common rail (not shown).

[0044] Figure 2 The number of external teeth 34 of the external gear 32 of the feed pump 30 shown in FIG. 1 is six, which is the same as the total number of cam ridges of the two cams 8. The number of external teeth of the external gear of the feed pump is not limited to being the same as the total number of cam ridges of the cam 8, but may be a multiple of the total number of cam ridges of the cam 8. For example, Figure 4 In the feed pump 50 shown, the number of the external teeth 54 of the external gear 52 may be twelve. In this case, the number of the external teeth 54 of the external gear 52 is twice the total number of the cam ridges of the two cams 8, which is six.

[0045] [1-2. Phase Synchronization between Pumping Cycle of Feed Pump 30 and Suction Cycle of High-Pressure Pump 60]

[0046] Next, a description will be given of phase synchronization between the pumping cycle of the feed pump 30 and the suction cycle of the high pressure pump 60. Here, the pumping cycle of the feed pump 30 means, for example, a cycle from when the pressure of the fuel pumped by the feed pump 30 becomes maximum.

[0047] In addition, the suction cycle of the high-pressure pump 60 represents, for example, a cycle of the time when the plungers 64 of the two high-pressure pumps 60 reach the top dead center and each high-pressure pump 60 starts the suction stroke. Therefore, when the number of high-pressure pumps 60 is n, the suction cycle of the high-pressure pump 60 is 1 / n of the cycle of the time when one high-pressure pump 60 starts the suction stroke.

[0048] The phase synchronization between the pumping cycle of the feed pump 30 and the suction cycle of the high-pressure pump 60 refers to the synchronization between the time when the pressure of the fuel pumped from the feed pump 30 becomes maximum and the time when each high-pressure pump 60 starts the suction stroke.

[0049] In the first embodiment, a fuel supply passage 100 for pumping fuel from the feed pump 30 to the high pressure pump 60 is formed in the housing 12, 14. Therefore, the length of the fuel supply passage 100 for supplying fuel from the feed pump 30 to the high pressure pump 60 can be shortened as much as possible.

[0050] Therefore, in the first embodiment, the delay time required for the fuel pumped from the feed pump 30 to reach the pressurization chamber 110 of the high-pressure pump 60 is within a negligible range. That is, it is considered that there is no phase difference between the pressure change in the fuel pumped from the feed pump 30 and the pressure change in the fuel sucked into the pressurization chamber 110.

[0051] Therefore, if Figure 5 As shown, in the first embodiment, phase synchronization is achieved between the pumping cycle of the feed pump 30 pumping fuel and the suction cycle of the high-pressure pump 60 sucking fuel into the pressurizing chamber 110. More specifically, the moment when the feed pump 30 completes fuel pumping and the pressure 200 of the fuel pumped by the feed pump 30 becomes maximum coincides with the moment when the lift 210, 212 of each plunger 64 of the high-pressure pump 60 reaches the top dead center (i.e., the starting point of the suction stroke).

[0052] That is, the angular position of the external gear 32 and the internal gear 36 of the feed pump 30 is set relative to the angular position of the cam 8 in the rotation direction so that the moment when the fuel pressure pumped out from the feed pump 30 becomes the maximum coincides with the moment when the lift degrees 210, 212 of the plunger 64 of the high-pressure pump 60 reach the top dead center.

[0053] [1-3. Effect]

[0054] The above-described first embodiment produces the following effects.

[0055] (1a) Since the time when the pressure of the fuel pumped from the feed pump 30 becomes maximum coincides with the start time of the suction stroke of the high-pressure pump 60, poor suction of fuel in the boosting chamber 110 during the suction stroke of the high-pressure pump 60 can be reduced without adding new components.

[0056] As a result, negative pressure generated in the pressurizing chamber 110 can be reduced. Even if the metering valve 66 is closed to meter the amount of fuel pumped from the high pressure pump 60 in the pumping stroke, pressure pulsation generated in the fuel supply system supplying fuel from the feed pump 30 to the pressurizing chamber 110 can be reduced.

[0057] In the first embodiment, the pumping completion timing of the feed pump 30 and the start timing of the suction stroke coincide with each other. Figure 6 As shown, the suction stroke start time of the high pressure pump 60 can be within 5° ahead of the pumping completion time of the feed pump 30. In this case as well, the maximum pressure of the pressure pulsation generated in the fuel supply system supplying fuel to the boost chamber 110 can be reduced as much as possible.

[0058] (1b) Since poor suction of fuel in the pressurizing chamber 110 is reduced, a decrease in the amount of fuel pumped from the high-pressure pump 60 can be reduced.

[0059] [2. Second embodiment]

[0060] [2-1. Differences from the first embodiment]

[0061] Since the basic structure of the second embodiment is similar to that of the first embodiment, the differences between the two will be described below. Note that the same reference numerals as those in the first embodiment denote the same structures, and reference is made to the previous description.

[0062] In the above-described first embodiment, a fuel supply passage 100 for supplying fuel from the feed pump 30 to the high-pressure pump 60 is formed in the housings 12, 14. On the other hand, the second embodiment is different from the first embodiment in that, in the fuel supply system 70, the fuel supply passage 100 for supplying fuel from the feed pump 30 to the high-pressure pump 60 extends from the interior of the housing 12 to the outside through the fuel filter 72 and the external pipes of the housings 12, 14, and then extends through the interior of the housing 14, thereby supplying fuel to the pressurization chamber 110.

[0063] [2-2. Phase Synchronization between Pumping Cycle of Feed Pump 30 and Suction Cycle of High-Pressure Pump 60]

[0064] In the second embodiment, the fuel supply passage 100 supplies fuel to the pressurizing chamber 110 from the inside of the housing 12 through the outside of the housings 12, 14. Therefore, the fuel supply passage 100 is longer than the passage length of the first embodiment. Therefore, the delay time required for the fuel pumped from the feed pump 30 to reach the pressurizing chamber 110 of the high-pressure pump 60 cannot be ignored.

[0065] Therefore, it is necessary to consider the delay time for the fuel pumped from the feed pump 30 to reach the pressurizing chamber 110 of the high-pressure pump 60 through the fuel supply passage 100 of Lm.

[0066] That is, it is necessary to synchronize the phase of the pumping cycle of the feed pump 30 with the phase of the suction cycle of the high-pressure pump 60 by advancing the moment when the pressure of the fuel pumped from the feed pump 30 becomes maximum to coincide with the start moment of the suction stroke of the high-pressure pump 60.

[0067] Therefore, the expression (1) shown below is established, where the advance angle of the pumping cycle of the feed pump 30 from the suction cycle of the high-pressure pump 60 is θ°, the path length of the fuel supply channel 100 is Lm, the rated speed of the feed pump 30 is 3000 rpm, and the pressure propagation speed in the fuel is 1500 m / s.

[0068] L / 1500=θ / {(3000 / 60)×360}...(1)

[0069] For example, when L=1 m, θ=12°.

[0070] When the channel length of the fuel supply channel 100 is 1 m, Figure 8 The timing chart shows the state of pressure 222 when the pumping cycle of the feed pump 30 is advanced by 12° from the state of pressure 220 where the timing at which the pressure of the fuel pumped by the feed pump 30 becomes maximum coincides with the start timing of the suction stroke of the high-pressure pump 60 .

[0071] Considering the channel length of the fuel supply channel 100, the time when the pressure of the fuel pumped from the feed pump 30 becomes maximum is 12° earlier than the state where the phases of the pumping cycle of the feed pump 30 and the suction cycle of the high-pressure pump 60 are consistent with each other. Therefore, the time when the pressure of the fuel pumped by the feed pump 30 becomes maximum when reaching the pressurizing chamber 110 coincides with the start time of the suction stroke of the high-pressure pump 60.

[0072] [2-3. Effect]

[0073] According to the above-described second embodiment, the timing of the pumping cycle of the feed pump 30 is advanced by 12° in consideration of the delay time required for the fuel supplied from the feed pump 30 to reach the pressurizing chamber 110 of the high-pressure pump 60 through the fuel supply passage 100. Therefore, the same effects as those of the effects (1a) and (1b) of the first embodiment can be obtained.

[0074] [3. Other embodiments]

[0075] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications may be made to implement the present disclosure.

[0076] (3a) In the above-described embodiment, as the positive displacement feed pump 30, for example, an internal cycloid pump in which the inner periphery of the internal gear 36 and the outer periphery of the external gear 32 are in contact with each other has been introduced. The positive displacement pump used as the feed pump is not limited to this, and for example, it may be an external gear pump in which the outer peripheries of two gears are in contact with each other, and it may be a vane pump in which vanes that can reciprocate in the radial direction are provided on the outer periphery of the rotor.

[0077] (3b) As long as it is possible to reduce the poor suction of fuel in the pressurizing chamber 110, the phase of the pumping cycle of the feed pump 30 may be synchronized with the phase of the suction cycle of the high-pressure pump 60 so that the fuel pumped from the feed pump 30 reaches the pressurizing chamber 110 at the start of the suction stroke of the high-pressure pump 60. The fuel pumped from the feed pump 30 refers to the fuel that is pressurized or has the highest pressure by the feed pump pressurization.

[0078] (3c) In the above-described embodiment, the feed pump 30 and the high-pressure pump 60 have been described as being driven by the same camshaft 6 as the drive shaft. Figure 1 and 7 As shown, the feed pump 30 and the high pressure pump 60 may be driven by different drive shafts.

[0079] However, even if the drive shafts are different, it is necessary to synchronize the rotation of the drive shafts with each other so that the phases of the pumping cycle of the feed pump and the suction cycle of the high-pressure pump are synchronized. For example, the feed pump 30 may be driven by a drive shaft of a motor different from the camshaft 6. The rotation of the motor is controlled to be synchronized with the rotation of the camshaft 6.

[0080] (3d) In the above embodiments, multiple functions of one component may be implemented by multiple components, or one function of one component may be implemented by multiple components. In addition, multiple functions of multiple components may be implemented by one component, or a single function implemented by multiple components may be implemented by one component. A part of the structure of the above embodiments may be omitted. At least a part of the structure of the above embodiments may be added to or replaced by another structure of the above embodiments.

[0081] (3e) In addition to the above-described fuel supply pump 10 , the present disclosure can be implemented in various forms such as a system including the fuel supply pump 10 as a component.

Claims

1. A fuel supply pump, comprising: Positive displacement feed pump (30, 50); and a high-pressure pump (60) which pressurizes and pumps the fuel pumped from the feed pump, wherein The high pressure pump comprises: a plunger (64) which reciprocates by the rotation of the cam (8) and draws the fuel pumped from the feed pump into the pressurizing chamber (110) and pressurizes the fuel; and a metering valve (66) which opens to open a fuel inlet side of the pressurizing chamber through which the fuel pumped from the feed pump is sucked, and closes to close the fuel inlet side, the metering valve being configured to meter the amount of fuel pumped from the pressurizing chamber by controlling the closing timing of the metering valve so that the metering valve is closed during a pumping stroke in which the plunger moves upward in the high-pressure pump, and The phase of the pumping cycle of the feed pump pumping the fuel and the phase of the suction cycle of the high-pressure pump sucking the fuel into the boost chamber are synchronized, so that the moment when the pressure of the fuel pumped by the feed pump (30) becomes maximum when reaching the boost chamber (110) coincides with the start moment of the suction stroke of the high-pressure pump (60).

2. The fuel supply pump according to claim 1, wherein The feed pump is a positive displacement gear pump, and The number of teeth of the gear of the feed pump is a multiple of the number of cam ridges that reciprocate the plunger.

3. The fuel supply pump according to claim 1, wherein The phase of the pumping cycle of the feed pump and the phase of the suction cycle of the high-pressure pump are synchronized so that the fuel pumped from the feed pump reaches the boosting chamber at the beginning of the suction stroke of the high-pressure pump, and during the suction stroke of the high-pressure pump, the plunger moves downward and the fuel is sucked into the boosting chamber.

4. The fuel supply pump according to claim 3, wherein The starting timing of the suction stroke of the high-pressure pump is at the top dead center of the plunger.

5. The fuel supply pump according to any one of claims 1 to 4, wherein A fuel supply passage (100) for supplying the fuel from the feed pump to the pressurizing chamber is formed in a housing of the fuel supply pump. The time when the pressure of the fuel pumped from the feed pump becomes maximum is defined as 0°, and By setting the start timing of the suction stroke of the high-pressure pump to -5° to 0°, the phase of the pumping cycle of the feed pump is synchronized with the phase of the suction cycle of the high-pressure pump.

6. The fuel supply pump according to any one of claims 1 to 4, wherein The timing at which the pressure of the fuel pumped from the feed pump becomes maximum is advanced from the start timing of the suction stroke of the high-pressure pump based on a fuel supply delay caused by the length of the fuel supply passage from the feed pump to the pressurizing chamber.

7. The fuel supply pump according to any one of claims 1 to 4, wherein The feed pump and the high-pressure pump are driven by different drive shafts, and By synchronizing the phases of the drive shafts, the phase of the pumping cycle of the feed pump and the phase of the suction cycle of the high-pressure pump are synchronized.

Images