JP2000038971A - Positive displacement pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive displacement type pump equipped with a means driving a pump plunger to the direction of return. SOLUTION: A high pressure positive displacement type pump suitable for feeding fuel to a fuel injection system, includes one or more than one of pump assemblies 2, 3 and 4. Each pump assembly is equipped with a cylinder block 1 partitioning a pump cylinder 12. In the inside of the pump cylinder 12, a pump plunger 13 is provided in such a way that it can be moved while being slid. The respective pump plungers 13 are connected with each tappet assembly 20. Each tappet assembly 20 includes a tappet shell 21 provided in such a way that it can be moved while being slid in the inside of a hole 22. When it use, each tappet assembly 20 is engaged with a cam 6 so as to allow the pump planger 13 to be driven to the pump feeding direction. Each working fluid chamber 30 is partitioned at the opposite side of the cam 6 in the respective tappet assemblies 20. When in use, pressurized working fluid is fed to each working fluid chamber 30 so as to allow each tappet and each pump planger to be driven to the direction of return. In this constitution, any return spring for the pump planger is not required.

Description

DETAILED DESCRIPTION OF THE INVENTION

TECHNICAL FIELD The present invention relates to a positive displacement pump. In a preferred embodiment, the present invention provides a pump suitable for use in delivering high pressure fuel to a fuel injection system of an internal combustion engine. However, the invention is not limited to this particular type of pump, but is substantially applicable to a wide range of positive displacement pumps.

BACKGROUND OF THE INVENTION In a positive displacement pump, a pump plunger reciprocates in a cylinder, changing the volume of the pump chamber and pumping fluid with the aid of appropriate valving. During the feed stroke of the plunger, a force is applied to the plunger so that fluid is discharged from the pump chamber. After each feeding stroke, there is a return stroke. In the return stroke, the plunger moves in the opposite direction to increase the volume of the pump chamber. For a larger pump,
Typically, a crankshaft or cam arrangement is used to drive the pump plunger, the pump plunger being connected to the crankshaft or cam and driven in both the forward pumping stroke and the return filling stroke. However, for smaller pumps, it is not possible to provide a mechanical link between the pump plunger and the drive crank or cam. In such situations, it is common to use a spring to drive the pump plunger during the return (fill) stroke. However, the use of springs may not be desirable.

SUMMARY OF THE INVENTION The present invention provides a novel means for driving the pump plunger of a positive displacement pump in the return direction.

According to the present invention, there is provided a cylinder; a pump plunger slidably provided in the cylinder to define a pump chamber together with the cylinder; and driving the pump plunger forward. Drive means for delivering pump fluid by reducing the volume of the pump chamber by means of: a piston connected to the pump plunger; the piston being formed in the pump. Slidably mounted within a bore defining a working chamber, the volume of the working chamber being adapted to increase as the volume of the pump chamber increases; Pressurized working fluid supply means for supplying the working fluid is further provided,
The pressurized working fluid supply means is adapted to generate a return force on the piston that tends to increase the volume of the pump chamber. The pressurized working fluid may be supplied to the working chamber only during a return stroke of the piston. However, in a preferred configuration, the pressurized working fluid is always present in the working chamber, and the drive means moves the pump plunger against the force generated by the working fluid during the forward stroke of the pump plunger. It is made to move. Preferably, the working fluid is a hydraulic fluid, and in a particularly preferred embodiment of the present invention, the working fluid is a lubricating oil. If the pump is used in conjunction with an internal combustion engine, for example, using a pump to deliver fuel to the internal combustion engine, lubricating oil is advantageously obtained from the lubrication system of the internal combustion engine. It is. In a particularly preferred embodiment of the invention, the piston is formed by a tappet assembly, which not only functions as a piston, but also moves from the drive cam during the forward stroke of the pump plunger. It is configured to perform a function of transmitting a force to the pump plunger. In a preferred embodiment of the present invention, when the piston is a tappet assembly,
The presence of pressurized lubricating oil in the working chamber not only provides the required return force, but also lubricates the tappet assembly. Under these circumstances, some oil may escape from the working chamber and pass through the tappet assembly into the pump's cam chamber, thereby lubricating the cam and ideally the pump's It is desirable that the drive shaft bearings also be lubricated. In a particularly preferred embodiment of the invention in which a plurality of pump plungers are provided, the working chambers associated with each pump plunger are preferably interconnected, whereby each pump plunger reciprocates. Sometimes the working fluid is allowed to flow between the working chambers. An accumulator that maintains the pressure of the working fluid and receives excess working fluid when the total volume of the working chamber changes while the drive shaft of the pump is rotating. You may. In a particularly preferred embodiment of the invention, a head is formed on each of said pump plungers, said head being attached to and forming part of said tappet assembly. The head can close the interior space of the tappet assembly, thereby allowing the tappet assembly to act as a piston. Preferably, the tappet includes a tappet shell, the head is received in the tappet shell, and a slip member is interposed between the head and the tappet shell. Preferably the lubricating member has a complementary flat surface engaging with the flat surface of the tappet shell and a complementary partial spherical surface or partial cone engaging with the partial spherical surface of the head of the pump plunger. Surface. Such a configuration can absorb any misalignment between the pump cylinder and the tappet. The present invention
It is particularly suited for application to a fuel pump suitable for delivering high pressure fuel to a fuel injection system of an internal combustion engine, but is not limited to such an application. further,
The invention is substantially applicable to a wide range of plunger shapes, and is applicable both when the plungers are arranged in an axial direction (parallel) and when they are arranged in a fan or cone shape. The present invention is also applicable to a wide range of drive mechanisms. For example, the present invention is applicable to driving mechanisms such as an outer cam, an inner cam, and a swash plate driving device.
Further, while lubricating oils and (especially) engine oils are preferred working fluids in preferred embodiments of the present invention, others may be used. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood from the following description of an embodiment thereof, given by way of example only.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The high-pressure fuel pump shown in FIGS. 1 to 3 is suitable for use in a fuel injection system of an internal combustion engine, and in particular, a high-pressure fuel pump in an accumulator or a common rail of a common rail fuel injection system. Suitable for feeding. The illustrated pump 1
Includes three pump assemblies 2, 3 and 4,
They are located in a common radius zone and are arranged at an angular distance of 120 degrees from one another about the drive shaft 5. The shaft 5 carries a single cam 6 for driving a pump assembly to deliver high pressure fuel from an outlet 7. The drive shaft 5 is supported in the pump body 8 by a front bearing 9 and a rear bearing 10. In use, the pump body 8 is mounted on an internal combustion engine, and a suitable rotational drive from the engine is used to rotate the shaft 5. Pump assembly 2,
3 and 4 are substantially identical to one another, and therefore for the sake of brevity, the following description details only the pump assembly 3. The pump assembly 3 includes a pump cylinder 12
Is included. The pump plunger 13 is slidably mounted in the cylinder 12 and reciprocates along the cylinder 12 when used, changing the volume of the pump chamber. The pump chamber is sequentially defined by a plunger, a cylinder, and a cylinder head 14. The cylinder head 14 is attached to the cylinder block 11. Feed valve 15 is cylinder head 1
4 is mounted. The feed valve 15 is normally biased to be pressed against the cylinder block by a spring. This spring is located in a bore 16 in the cylinder head, by means of which the delivery valve closes the end of the cylinder 12. The feed valve 15 is surrounded by a gallery 17. Gallery 1
7 is connected via a passage 18 in the cylinder block 11 and the pump body 8 to a corresponding gallery surrounding the feed valve of another pump assembly. Passage 18
It is connected to the feed outlet 7 by a branch passage 19. In use, as each pump plunger 13 is driven toward its associated cylinder head 14, the fuel in the pump chamber is pressurized and the pressure of fuel in cylinder 12 exceeds the pressure of fuel in gallery 17 and passage 18. And the feed valve 15
Opens to allow fuel to flow from pump chamber 12 to passage 18 and ultimately to outlet 7 via branch passage 19. The delivery valve 15 automatically closes under the influence of the associated spring force when the pump plunger reaches the top dead center. The closing of the delivery valve 15 is aided by the pressure differential created by the plunger starting to move inward after reaching upper dead center. Each plunger 13 is connected to an associated tappet assembly 20. Each tappet assembly 20 includes a tappet shell 21. Tappet shell 21
It is slidably mounted in a hole 2 formed in the main body 8. A roller 23 is rotatably mounted on a shaft 24. The shaft 24 is attached to the tappet shell 21. At the end of each tappet shell 21 remote from the shaft 5, the tappet shell 21 is provided with a counterbore to form a shoulder 25. A slip member 26 is mounted within the counterbore portion of each tappet shell. The thrust surface of the lubricating member 26 is the shoulder 25
Is engaged. Since the diameter of the slip member is slightly smaller than the diameter of the counterbore portion of the tappet shell, the slip member can move somewhat laterally with respect to the tappet shell. Each lubricating member 26 has a spherical seat (seat) 27
Is defined. The spherical seat 27 engages a complementary spherical surface 28 provided on the head 29 of the associated plunger 13. Instead of a partial spherical surface, a partial conical surface can also be used. Each plunger 13 is attached to the associated tappet shell by any suitable method. The method allows for proper sealing while retaining the degree of freedom required for articulation. For example, an elastic circlip can be used. The circlip may have one or more washers, or may not have washers. In use, the pump plunger 13 cannot be substantially separated from its associated tappet shell. As an effect of the configuration of the slip member described above,
An axial thrust load is transmitted from the tappet shell to the pump plunger 13 while allowing some lateral movement of the tappet shell relative to the plunger 13. Thus, some eccentricity and misalignment of the cylinder 12 with respect to the bore 22 can be accommodated by the movement of the slipper relative to the tappet shell.
In use, if the plunger is in the lower dead center position, rotation of the shaft 5 causes the cam 6 to act on the roller 23, which drives the tappet shell, and the plunger 13 is moved together with the tappet shell. It is driven radially outward toward the upper dead center. With this movement, fuel is supplied to the outlet 7 as described above. Means are provided for supplying pressurized fluid to chamber 30 to return each pump plunger from its upper dead center position to its lower dead center position. The chamber 30 is partially defined by the bore 22, another part is defined by a radially outer surface of the tappet assembly, and another part is defined by the cylinder block 11. Advantageously, the pressurized fluid is pressurized lubricating oil obtained from a lubrication system of the engine that is acted upon by the illustrated pump.
Such lubricating oil is supplied through the inlet fitting 31 and is supplied to the chamber 30 through the drill hole 32 and the slot 33. It can be seen that the pressurized lubricating oil in the chamber 30 acts over the area of the tappet assembly (less than the area of the pump plunger 13) and generates a radially inward force on the pump plunger 13.
When none of the rollers 23 is driven by the cam 6, when the associated plunger moves from the upper dead center position to the lower dead center position, the oil pressure in the associated chamber 30 increases.
Roller 23 is used to maintain contact with cam 6. In the illustrated pump, the inlet valve is not provided on the cylinder head 14 or at a position adjacent to the cylinder head 14. However, on the other hand, one or more passages 34 extend from the fuel gallery 35 defined between the cylinder block 11 and the cylinder head 14 and are located just below the lower dead center of the radially outer end of the pump plunger 13. It reaches a point inside the hole 12 that is radially outward. Fuel at a pressure slightly above atmospheric pressure is maintained in the gallery 35 by a transfer pump. When the pump plunger moves from the upper dead center position to the lower dead center position, the feed valve 15 closes, and then the cylinder 1
A vacuum is generated in 2. Pump plunger 13
As soon as its radially outer end passes through the port 36 at the junction of the passage 34 and the cylinder 12, the combination of the vacuum created in the cylinder 12 with the pressure above the atmospheric pressure present in the gallery 35. Under the influence, fuel flows from the gallery 35 through the passage 34 into the cylinder 12. Typically, the engine oil pressure when the engine is at idling speed is sufficient to drive the plunger 13 from the upper dead center position to the lower dead center as required when applied over the area of the tappet assembly. Give power. As the pump assembly operates, the volume of the associated working chamber 30 changes periodically. When a pump plunger is driven from the lower dead center position to the upper dead center position,
The volume of the associated working chamber 30 decreases, while at the same time the volume of at least one working chamber 30 of the other pump assembly increases. Thus, when the pump operates, oil tends to flow from one chamber 30 through the drill hole 32 to the other chamber 30. There may be some variation in the total volume of the chamber 30 when the pump operates. Thus, a somewhat smaller net flow of oil may enter and exit the inlet 31. Desirably, some lubricating oil may be allowed to leak out of the chamber 30 and into the cam chamber 37 to lubricate the tappet assembly or lubricate the rollers 23 and cam 6. The leaked oil further lubricates the bearings 9 and 10 and desirably flows through the front bearing 10 back to the crankcase of the engine where the fuel pump is mounted. It is actually desirable that some net amount of loss flow through the tappet assembly and into the cam chamber 37. The flow of lubricating oil is allowed to flow through the pump, thereby tending to overheat the lubricating oil due to being driven into and out of the chamber 30 when the pump operates. It is because it can reduce. The above-described embodiments of the present invention not only provide a simple and reliable means for returning the pump plunger from its upper dead center position to its lower dead center position, but also provide various internal parts of the pump assembly. High quality lubrication can also be performed on the components. Lubrication is provided by pressurized lubricating oil. Pressurized lubricating oil is an ideal medium for performing such lubrication. Although the invention has been described with respect to particular embodiments,
The present invention is substantially applicable to a wide range of positive displacement pumps and, therefore, the invention is not limited to the embodiments described. Moreover, the present invention is substantially applicable to any positive displacement pump in which the pump plunger is required to be driven from an upper dead center position to a lower dead center position. Although the use of lubricating oil to drive the pump plunger from the upper dead center position to the lower dead center position will provide many advantages, the invention is not limited to such fluids. The pressurized fluid required to operate the pump plunger can be obtained from any suitable source. If desired, a pressure accumulator may be used to absorb variations in the total volume of the pressurized fluid system as the pump operates. The present invention may be applied to a pump having only a single pump plunger. In this case, a pressure accumulator having a sufficient volume to receive the entire discharge volume of the working fluid is required. Such a pressure accumulator is powered by a spring. The spring drives a pump plunger that uses hydraulic fluid as the working medium.
Such an arrangement is similar to the use of a spring that directly drives the pump plunger in the filling direction, but does not impose the design limitations associated with using a spring directly for this purpose. . Under appropriate circumstances, a non-return
A valve may be provided and used so that the accumulator can determine the operating pressure. The working pressure is
Exceeding the oil supply pressure in part of the reciprocation of the accumulator piston. At such higher pressures, the pump can handle increasing tappet accelerations and operate at higher speeds. Alternatively, utilizing a non-circular cam may result in increased acceleration. Such a cam may include one or more lobes. In order to obtain a quick return stroke by reducing the driving torque, the pumping action may be arranged to be slow. FIGS. 4 to 6 are views schematically showing another embodiment of the present invention. In this embodiment, three substantially identical pump assemblies 102, 103, 104 are axially spaced along a camshaft 105. The camshaft 105 has three cams 106 arranged with a phase shift of 120 degrees from each other. Each cam is associated with a respective one of the pump assemblies 102, 103, 104. The camshaft 105 is supported on the pump body 108 by a front bearing 109 and a rear bearing 110. In use, the pump body 108 can be mounted on an internal combustion engine, and a suitable rotary drive from the engine is used to rotate the camshaft 105. Each of the pump assemblies 102, 103, 104 is substantially identical to one another, and is also substantially identical to the pump assemblies 2, 3, 4 in the embodiment of the present invention shown in FIGS. is there. For simplicity, the pump assembly 102
Only the details will be described. The pump assembly 102
It includes a cylinder block 11 that defines a pump chamber 112. A pump plunger 113 is operatively mounted on the cylinder 112. In use, the pump plunger 13 reciprocates along the cylinder, changing the volume of the pump chamber defined by the pump plunger and cylinder block 111. A delivery valve 115 is provided for discharging the fluid pumped from the pump chamber. Appropriate passages provided in the cylinder block 111 are provided for the respective pump assemblies 102, 10, 10
4 and provide a discharge passage for the pumped fluid. Each pump plunger 113 has an associated tappet assembly 1
20. The tappet assembly and the means for coupling between the tappet assembly and the pump plunger can be similar to those described above in connection with FIG. However, the invention is not limited to such an arrangement, and any suitable arrangement can be used to connect the pump plunger to the tappet assembly.
Rollers 123 are carried by tappet assembly 120 and engage the surface of cam 106. Working chamber 11
3 is the tappet assembly 120 and the cylinder block 111
Is defined between The working chamber 130 has a volume that increases as the volume of the pump chamber increases,
It decreases as the volume of the plunger chamber increases. Suitable means are provided for supplying the pressurized working fluid to the working chamber 130. The working fluid may be pressurized lubricating oil, and the working fluid delivery means may be a lubricating oil pump associated with the engine. The high-pressure pump of the present invention is attached to this engine. However, any suitable working fluid may be supplied by any suitable means to pressurize the working chamber 130. The working fluid has an area based on the diameter of the hole 122 in which the tappet assembly 120 operates and the pump plunger 1.
13 acts on the tappet assembly 120 over an operating area substantially equal to the difference in area of the cylinder 112 in which it operates. This area is larger than the area of the operation area of the pump plunger 113, and a sufficiently large force can be generated on the pump plunger 113 by applying lubricating oil as a working fluid at an intermediate pressure. Thereby, the pump plunger is moved from its second position (upper dead center position) to the first position (lower dead center position). During the forward stroke of the pump plunger (pump feed stroke), the pump plunger is driven by an associated cam 106 from a first position (lower dead center position) to a second position (upper dead center position). You. Desirably, the pressurized working fluid is maintained in the working chamber 130 during the forward stroke of the pump plunger. The force obtained by the cam is
Sufficient to overcome the force created by the pressurized working fluid within zero and also provide the necessary force to drive the high pressure fluid from the pump chamber of the pump. Working fluid chamber 130
May be combined as a trough to allow for fluid exchange with low flow resistance. For this purpose, a suitable connection between the chambers may be formed by drill holes and / or slots, as in the embodiment of FIGS. As in the embodiment of FIGS. 1-3, an accumulator is provided to maintain the working fluid pressure within the working chamber and to receive fluid from the working chamber when the volume of the working chamber fluctuates during use. It may be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a high-pressure fuel pump, taken along a line II in FIG.

FIG. 2 is a longitudinal sectional view of the pump of FIG. 1, and is a II-II sectional view of FIG.

FIG. 3 is a sectional view taken along the line III-III in FIG. 2;

4 is a schematic sectional view showing a second embodiment of the present invention, and is a sectional view taken along line IV-IV in FIG. 5;

5 is a schematic longitudinal sectional view of the pump of FIG. 4, and FIG.
FIG.

FIG. 6 is a diagram showing a phase configuration of the pump of FIGS. 4 and 5;

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Michael Peter Cook UK 7.1 M. Kent, Gillingham, Burnt Oak Terrace 52 (72) Inventor Iron Roy Thornswait M.E. 7.3 PJ Kent, Gillingham, Hempstead, Old Barn Close 1 (72) Inventor Peter Alban George Collingbourne MM 8.8 REX Kent, Gillingham, Raynham, Burnham Walk 82

Claims (11)

[Claims] A cylinder (12); and a pump plunger (13) slidably provided in the cylinder and defining a pump chamber together with the cylinder, wherein the pump chamber has a maximum volume. A pump plunger (13) having a first position relative to the cylinder and a second position relative to the cylinder to minimize the volume of the pump chamber;
Driving means (6, 23, 2) for driving the pump fluid by driving 3) forward from the first position to the second position to reduce the volume of the pump chamber;
0) and: a piston (20) is connected to the pump plunger (13); the piston is formed in the pump and has a working chamber (3).
0) is slidably provided in a bore (22) defining the working chamber (30), wherein the volume of the working chamber (30) is such that the pump plunger returns from the second position to the first position. Increased as one moves in the direction;
Pressurized working fluid supply means for supplying a working fluid pressurized to the working chamber (30) is further provided,
The pressurized working fluid supply means is configured to generate a force on the piston (20) to move the pump plunger (13) from the second position to the first position in a return direction. Yes: positive displacement pump. 2. A positive displacement pump according to claim 1, wherein said pressurized working fluid supply means supplies working fluid to said working chamber whenever said pump is in an operating state. A positive displacement pump, wherein the drive means is adapted to move the pump plunger (13) against a force generated by a working fluid during a forward movement stroke of the pump plunger. 3. A positive displacement pump according to claim 1, wherein said pressurized working fluid supply means includes pressurized lubricating oil supply means. 4. The positive displacement pump according to claim 3, wherein said pressurized lubricating oil supply means includes a lubricating oil pump for an internal combustion engine. 5. A positive displacement pump according to claim 1, wherein said piston (20) is formed by a tappet assembly, said tappet assembly comprising:
Not only serving as a piston, but also acting to transmit force from the drive cam (6) to the pump plunger (13) during the forward travel of the pump plunger (13). Positive displacement pump. 6. A positive displacement pump according to claim 5, wherein a leakage flow path is defined through said tappet assembly (20), whereby lubricating oil is removed from said working chamber (30). A positive displacement pump adapted to leak and lubricate internal components of the pump. 7. The positive displacement pump according to claim 5, wherein a head (29) is formed on each of the pump plungers (13).
Is attached to and forms part of the tappet assembly, and wherein the head (29) causes the tappet assembly to act as a piston by closing the interior space of the tappet assembly. , A positive displacement pump. 8. The pump according to claim 7, wherein said tappet assembly includes a tappet shell (21), and said head (29) of said pump plunger is received within said tappet shell. A positive displacement pump having a slip member (26) inserted between the head and the tappet shell. 9. A positive displacement pump according to claim 8, wherein said lubricating member (26) is complementary to a flat surface of said tappet shell and said head of said pump plunger. A positive displacement pump having a complementary partial spherical surface (27) or a partial conical surface that engages the partial spherical surface (28) of (29). 10. A positive displacement pump according to claim 1, wherein said pump plunger (13).
Are provided, and the working chambers (30) associated with the respective pump plungers are configured such that a working fluid flows between the working chambers (30) when the respective pump plungers reciprocate. Positive displacement pumps interconnected so that they can. 11. The positive displacement pump according to claim 1, further comprising an accumulator, said accumulator being adapted to drive said working chamber (30) while the drive shaft of said pump is rotating. The positive displacement pump is adapted to maintain the pressure of the working fluid and receive excess working fluid when the total volume of the fluid changes.