CN113250874A

CN113250874A - Fuel supply pump

Info

Publication number: CN113250874A
Application number: CN202011449375.8A
Authority: CN
Inventors: 盐原健太郎
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2020-02-07
Filing date: 2020-12-09
Publication date: 2021-08-13
Also published as: DE102020128113A1; JP2021124092A; JP7367548B2

Abstract

The fuel supply pump includes a positive displacement charge pump (30, 50) and a high pressure pump (60) that pressurizes and pumps fuel pumped from the charge pump. The high-pressure pump includes a plunger (64) reciprocating in a pressurizing chamber (110) and a metering valve (66) that opens to open a fuel inlet side of the pressurizing chamber through which fuel pumped from the feed pump is sucked; and shut off to close off the fuel inlet side. The metering valve meters an amount of fuel pumped from the pressurizing chamber by controlling a closing timing of the metering valve such that the metering valve is closed during a pumping stroke of the high-pressure pump in which the plunger is moved upward. The phase of the pumping cycle during which the feed pump pumps fuel is synchronized with the phase of the suction cycle during which the high pressure pump draws fuel into the pumping chamber.

Description

Fuel supply pump

Technical Field

The present disclosure relates to a technique in which a high-pressure pump pressurizes and pumps fuel pumped from a volumetric feed pump.

Background

A technique is known in which fuel pumped from a positive displacement feed pump is drawn into a pressurizing chamber of a high-pressure pump by reciprocating movement of a plunger and pressurized therein to be pumped from the high-pressure pump.

For example, patent document 1(DE 102009028164 a1) discloses a gear pump as a positive displacement feed pump, in which outer teeth of two gears are meshed with each other and rotated, so that the gear pump pumps fuel to a high-pressure pump.

The amount of fuel pumped from the high-pressure pump is metered, for example, by a pre-stroke method which controls the closing timing of the metering valve during the pumping stroke in which the high-pressure pump plunger is lifted. The metering valve is disposed on a fuel inlet side of the plenum.

Disclosure of Invention

As disclosed in patent document 1, in the positive displacement feed pump, the pressure of the fuel pumped from the feed pump to the high-pressure pump repeatedly rises and falls. When the fuel pressure changed in this way is low and fuel is drawn into the pressurizing chamber during the suction stroke in which the plunger moves downward, the amount of fuel drawn into the pressurizing chamber decreases, and this poor suction causes a negative pressure in the pressurizing chamber.

In particular, in the high speed rotation range of the engine, the time required for the intake stroke becomes short, thereby further reducing the amount of fuel drawn into the pressurizing chamber. As a result, the pumping chamber is more negatively pressurized.

If the metering valve is closed when the plenum chamber pressure is negative due to poor suction of fuel in the plenum chamber, a water hammer pressure occurs and pressure pulsation occurs at the fuel inlet side of the plenum chamber. According to a detailed study of the inventors of the present application, it has been found that such pressure pulsation causes a large pressure variation applied to a component constituting a fuel supply system that supplies fuel from a feed pump to a pressurizing chamber. Furthermore, it has been found a problem that the amount of fuel pumped by the high-pressure pump decreases due to poor suction of fuel in the pressurizing chamber.

In the technique described in patent document 1, in the fuel supply system on the fuel inlet side of the pressurizing chamber, a damper is arranged in parallel with the feed pump, and pressure pulsation generated on the fuel inlet side of the pressurizing chamber is reduced.

However, if a damper is provided for suppressing pressure pulsation generated at the fuel inlet side of the pressurizing chamber as in the technique described in patent document 1, the number of parts increases. Further, even if the damper is installed to reduce the pressure pulsation generated at the fuel inlet side of the pressurizing chamber, the problem of a decrease in the amount of fuel pumped from the high-pressure pump due to poor suction of the fuel in the pressurizing chamber is not solved.

In one aspect of the present disclosure, it is desirable to provide a technique for reducing poor suction of fuel drawn into a plenum without adding new components.

According to one aspect of the present disclosure, a fuel supply pump includes a positive displacement charge pump (positive displacement charge pump), and a high-pressure pump pressurizes and pumps fuel pumped from the charge pump.

The high-pressure pump includes a plunger that reciprocates by rotation of a cam, and sucks fuel pumped from the feed pump into a pressurizing chamber and pressurizes the fuel. The high-pressure pump includes a metering valve that is opened to open a fuel inlet side of the pressurizing chamber through which fuel pumped from the feed pump is sucked, and that is closed to close the fuel inlet side. The metering valve meters the amount of fuel pumped from the pressurizing chamber by controlling the timing of closing of the metering valve such that the metering valve closes during a pumping stroke in which the high-pressure pump plunger moves upward. The phase of the pumping cycle during which the feed pump pumps fuel is synchronized with the phase of the suction cycle during which the high pressure pump draws fuel into the pumping chamber.

According to this aspect, the pumping period of the feed pump and the suction period of the high-pressure pump are synchronized so that the feed pump pumps the fuel according to the suction stroke in which the high-pressure pump plunger moves downward and sucks in the fuel. Therefore, it is possible to reduce poor suction of fuel in the pressurizing chamber during the suction stroke of the high-pressure pump without an additional component. Therefore, the negative pressure generated in the pressurizing chamber can be reduced.

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 fuel from the feed pump to the pressurizing chamber can be reduced.

Further, since poor suction of fuel in the pressurizing chamber is reduced, a drop in the amount of fuel pumped from the high-pressure pump can be reduced.

Drawings

Fig. 1 is a block diagram showing a fuel supply system according to a first embodiment.

Fig. 2 is a schematic diagram showing the configuration of the feed pump.

Fig. 3 is a schematic diagram showing the configuration of the cam.

Fig. 4 is a schematic diagram showing another configuration of the feed pump.

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

Fig. 6 is a characteristic diagram showing the relationship between the pressure pulsation and the phase difference between the start of the suction of fuel into the pressurizing chamber and the completion of pumping by the feed pump.

Fig. 7 is a block diagram showing a fuel supply system according to a second embodiment.

Fig. 8 is a timing diagram showing the pressure of fuel pumped by the feed pump, the pressure on the fuel inlet side of the pumping chamber, and the plunger lift.

Detailed Description

Embodiments of the present disclosure will be described hereinafter with reference to the accompanying drawings. In the embodiment, the same reference numerals may be assigned to portions corresponding to the contents described in the previous embodiment, and repeated explanation of the portions may be omitted. While only a part of the structure is described in the embodiment, another previous embodiment may be applied to other parts of the structure. Parts may be combined even if they are not explicitly described. Even if the embodiment can be combined is not explicitly described, the embodiment may be partially combined as long as the combination is not impaired.

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

[1. first embodiment ]

[1-1. Structure ]

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

The fuel supply pump 10 includes

housings

12, 14, a relief 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.

A relief valve 22 and a feed pump 30 are housed in the housing 12. The relief valve 22 opens when the pressure of the fuel pumped from the feed pump 30 exceeds a predetermined pressure.

As shown in fig. 2, the charge pump 30 is a positive displacement gerotor 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 rotational motion.

The charge pump 30 includes an outer gear 32 and an inner gear 36. The external gear 32 has six external teeth 34 that project radially outward and are arranged at equal angular intervals. The angular position of the external gear 32 in the rotational direction relative to the camshaft 6 is determined by the key 6a of the camshaft 6 fitted to the inner peripheral side of the external gear 32.

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

When the external gear 32 is rotated by the rotation of the camshaft 6, the internal gear 36 is also rotated along with the rotation of the external gear 32. According to the increase and decrease of the volume formed between the external gear 32 and the internal gear 36, the fuel sucked from the fuel tank through the suction port (not shown) of the charge pump 30 is pressurized and supplied to the fuel supply passage 100 leading to the high-pressure pump 60.

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.

As shown in fig. 1, both high-pressure pumps 60 include a tappet 62, a plunger 64, a metering valve 66, and a discharge valve 68.

The tappets 62 of the two high-pressure pumps 60 are in contact with either of the two cams 8 provided on the camshaft 6. As shown in fig. 3, each cam 8 has three cam ridges formed at equal angular 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 rotational direction with respect to the position of the cam ridges.

Each tappet 62 reciprocates three times in a linear direction during one rotation of the camshaft 6 in accordance with the rotation of the cam 8.

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 plunger 64 is provided with a pumping chamber 110 for drawing in fuel pumped from charge pump 30.

The metering valve 66 is a solenoid valve that is fully opened in an intake 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 a pumping stroke in which the plunger 64 is lifted. When metering valve 66 is open, the fuel inlet side of plenum 110 is open. When metering valve 66 is closed, the fuel inlet side of plenum 110 is closed.

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

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

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

The number of the outer teeth 34 of the outer gear 32 of the feed pump 30 shown in fig. 2 is six, which is the same as the total number of the cam ridges of the two cams 8. The number of external teeth of the external gear of the feed pump is not limited to the same as the total number of cam ridges of the cam 8, and may be a multiple of the total number of cam ridges of the cam 8. For example, in the charge pump 50 shown in FIG. 4, the outer teeth 54 of the outer gear 52 may be twelve in number. In this case, the number of the external teeth 54 of the external gear 52 is twice as many as six as the total number of the cam ridges of the two cams 8.

[1-2. phase synchronization between the pumping cycle of the feed pump 30 and the suction cycle of the high pressure pump 60 ]

Next, phase synchronization between the pumping cycle of the feed pump 30 and the suction cycle of the high-pressure pump 60 will be described. Here, the pumping period of the feed pump 30 indicates, for example, a period of time when the pressure of the fuel pumped from the feed pump 30 becomes maximum.

Further, the suction cycle of the high-pressure pump 60 indicates, for example, a cycle at a timing at which the plungers 64 of the two high-pressure pumps 60 reach the top dead center and each high-pressure pump 60 starts a suction stroke. Therefore, in the case where the number of high-pressure pumps 60 is n, the suction cycle of the high-pressure pump 60 is 1/n of the cycle at the time when one high-pressure pump 60 starts the suction stroke.

The phase synchronization between the pumping period of the feed pump 30 and the suction period of the high-pressure pump 60 refers to the synchronization between the timing at which the pressure of the fuel pumped from the feed pump 30 becomes maximum and the timing at which each high-pressure pump 60 starts the suction stroke.

In the first embodiment, a fuel supply passage 100 that pumps fuel from the feed pump 30 to the high-pressure pump 60 is formed in the

housings

12, 14. Therefore, the length of the fuel supply passage 100 that supplies fuel from the feed pump 30 to the high-pressure pump 60 can be shortened as much as possible.

Therefore, in the first embodiment, 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 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 pressurizing chamber 110.

Thus, as shown in fig. 5, in the first embodiment, phase synchronization is achieved between the pumping cycle in which the feed pump 30 pumps fuel and the suction cycle in which the high-pressure pump 60 sucks fuel into the pressurizing chamber 110. More specifically, the timing at which the feed pump 30 completes the fuel pumping and the fuel pressure 200 pumped by the feed pump 30 becomes maximum coincides with the timing at which the

lift

210, 212 of each plunger 64 of the high-pressure pump 60 reaches the top dead center (i.e., the start of the intake stroke).

That is, the angular positions of the outer gear 32 and the inner gear 36 of the feed pump 30 are set in the rotational direction with respect to the angular position of the cam 8 so that the timing at which the pressure of the fuel pumped out from the feed pump 30 becomes maximum coincides with the timing at which the

lift degrees

210, 212 of the plunger 64 of the high-pressure pump 60 reach the top dead center.

[1-3. Effect ]

The first embodiment described above produces the following effects.

(1a) Since the timing at which the pressure of the fuel pumped from the feed pump 30 becomes maximum coincides with the start timing of the suction stroke of the high-pressure pump 60, poor suction of the fuel into the pressurizing chamber 110 in the suction stroke of the high-pressure pump 60 can be reduced without adding new components.

As a result, the negative pressure generated in the plenum 110 can be reduced. Even if metering valve 66 is closed to meter the amount of fuel pumped from high-pressure pump 60 during the pumping stroke, pressure pulsations that occur in the fuel supply system supplying fuel from charge pump 30 to pressurizing chamber 110 may be reduced.

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. On the other hand, as shown in fig. 6, the suction stroke start timing of the high-pressure pump 60 may be advanced by an angle within 5 ° from the pumping completion timing of the feed pump 30. Also in this case, the maximum pressure of the pressure pulsation generated in the fuel supply system that supplies fuel to pressurizing chamber 110 can be reduced as much as possible.

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

[2. second embodiment ]

[2-1. difference from the first embodiment ]

Since the basic structure of the second embodiment is similar to that of the first embodiment, the difference between the two will be described below. Note that the same reference numerals as those in the first embodiment denote the same structures, and the foregoing description is referred to.

In the first embodiment described above, the fuel supply passage 100 for feeding the 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 differs from the first embodiment in that, in the fuel supply system 70, a 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 outward through the fuel filter 72 and the outer piping of the

housings

12, 14, and then extends through the interior of the housing 14, thereby supplying the fuel to the pressurizing chamber 110.

[2-2. phase synchronization between the pumping cycle of the feed pump 30 and the suction cycle of the high pressure pump 60 ]

In the second embodiment, the fuel supply passage 100 supplies fuel from inside the housing 12 to the pressurizing chamber 110 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 charge pump 30 to reach the pressurizing chamber 110 of the high-pressure pump 60 is not negligible.

Therefore, it is necessary to consider a delay time of 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.

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 state in which the timing at which the fuel pressure pumped from the feed pump 30 becomes maximum and the timing at which the fuel pressure pumped from the feed pump 30 becomes maximum coincide with the start timing of the suction stroke of the high-pressure pump 60.

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

L/1500＝θ/{(3000/60)×360}...(1)

For example, when L is 1m, θ is 12 °.

When the passage length of fuel supply passage 100 is 1m, the timing chart of fig. 8 shows the state of pressure 222 at the time when the pumping cycle of feed pump 30 is advanced by 12 ° from the state of pressure 220 in which the pressure of fuel pumped by feed pump 30 becomes maximum and the suction stroke start time of high-pressure pump 60.

The timing at which the pressure of the fuel pumped from the feed pump 30 becomes maximum is advanced by 12 ° in advance of the state in which the pumping period of the feed pump 30 and the suction period of the high-pressure pump 60 are in phase with each other, taking into account the passage length of the fuel supply passage 100. Therefore, the timing at which the pressure of the fuel pumped by feed pump 30 becomes maximum upon reaching pressurizing chamber 110 coincides with the start timing of the suction stroke of high-pressure pump 60.

[2-3. Effect ]

According to the second embodiment described above, 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 the effects (1a) and (1b) of the first embodiment can be obtained.

[3. other examples ]

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.

(3a) In the above embodiment, as the positive displacement feed pump 30, for example, an inscribed trochoid pump in which the inner periphery of the inner gear 36 and the outer periphery of the outer gear 32 contact each other has been described. The positive displacement pump used as the feed pump is not limited thereto, and may be, for example, a circumscribed-gear pump in which the outer peripheries of two gears contact each other, and a vane pump in which vanes that are reciprocatable in the radial direction are provided on the outer periphery of a rotor.

(3b) As long as poor suction of fuel in pressurizing chamber 110 can be reduced, the phase of the pumping cycle of feed pump 30 and the phase of the suction cycle of high-pressure pump 60 may be synchronized so that fuel pumped from feed pump 30 reaches pressurizing chamber 110 at the start of the suction stroke of high-pressure pump 60. The fuel pumped from the feed pump 30 refers to the fuel that is pressurized or at its greatest pressure by the feed pump.

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

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

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

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

Claims

1. A fuel supply pump comprising:

a positive displacement feed pump (30, 50); and

a high-pressure pump (60) that pressurizes and pumps the fuel pumped from the feed pump, wherein

The high pressure pump includes:

a plunger (64) that reciprocates by rotation of a cam (8) and sucks the fuel pumped from the feed pump into a pressurizing chamber (110) and pressurizes it; and

a metering valve (66) that opens to open a fuel inlet side of the pressurizing chamber through which the fuel pumped from the feed pump is sucked; and close to close the fuel inlet side, the metering valve being configured to meter an amount of fuel pumped from the pressurizing chamber by controlling a closing timing of the metering valve such that the metering valve is closed during a pumping stroke of the high-pressure pump in which the plunger is moved upward, and

the phase of a pumping cycle in which the charge pump pumps the fuel and the phase of a suction cycle in which the high pressure pump draws the fuel into the pumping chamber are synchronized.

2. The fuel supply pump of claim 1, wherein

The feed pump is a gear positive displacement pump, and

the number of teeth of the gears of the feed pump is a multiple of the number of cam ridges that reciprocate the plunger.

3. The fuel supply pump of claim 1, wherein

The phase of the pumping cycle of the charge pump and the phase of the suction cycle of the high pressure pump are synchronized such that the fuel pumped from the charge pump reaches the pumping chamber at the beginning of a suction stroke of the high pressure pump during which the plunger moves down and the fuel is drawn into the pumping chamber.

4. The fuel supply pump of claim 3, wherein

The start time of the intake stroke of the high-pressure pump is at a 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 timing at which the pressure of the fuel pumped from the feed pump becomes maximum is defined as 0 °, and

synchronizing the phase of the pumping cycle of the charge pump with the phase of the suction cycle of the high pressure pump by setting a start timing of a suction stroke of the high pressure pump to-5 ° to 0 °.

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 a 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, an

By synchronizing the phase of the drive shaft, the phase of the pumping cycle of the charge pump and the phase of the suction cycle of the high pressure pump are synchronized.