WO2009152659A1

WO2009152659A1 - High pressure pump assembly for common rail system

Info

Publication number: WO2009152659A1
Application number: PCT/CN2008/071368
Authority: WO
Inventors: Adrian Jacob; Changjun Li; Yawei Wang
Original assignee: Bosch Automotive Diesel Systems Co., Ltd.; Wuxi Weifu High-Technology Co., Ltd.
Priority date: 2008-06-19
Filing date: 2008-06-19
Publication date: 2009-12-23
Also published as: CN101828025A; CN101828025B

Abstract

A high pressure pump assembly for a common rail system comprises a casting (5), a feed pump (1) mounted to the casting for drawing fuel from a fuel reservoir and pre-pressurizing the fuel, a high pressure pumping unit (2) mounted in the casting for receiving the pre-pressurized fuel from the feed pump, further pressurizing the fuel and supplying it to a rail of the common rail system, a shared driving means (10) for operatively driving both the feed pump and the high pressure pumping unit, and a flow regulator (3) for controlling the fuel pressure in the rail and the fuel pumping procedure.

Description

High Pressure Pump Assembly for Common Rail System

Technical Field

The present invention relates to a high pressure pump assembly for Common Rail system, in which a feed pump, a high pressure pumping unit and a fuel flow regulator are integrated together by a single casting.

Background Art

In fuel injection systems for diesel engines, Common Rail technology plays a major role in meeting the present and future exhaust emission standards, such as Euro 3 and beyond. Most European automakers now have Common Rail diesels in their model line-up, even for commercial vehicles. Some Asian manufacturers have also developed Common Rail diesel engines.

In a fuel injection system equipped with a Common Rail, a high pressure pump supplies fuel at high pressure into the rail, basically a tube which in turn branches off to computer-controlled injector valves, each of which contains a precision-machined nozzle and a plunger driven by a solenoid. The injector valves control the precise moment when the fuel injection into the cylinder occurs and also allow the pressure at which the fuel is injected into the cylinders to be increased. A flow regulator controls the amount of the high pressure fuel which the pump delivers to the rail.

For supplying high pressure fuel into a rail, a pre-delivery pump and a high pressure pump may be adopted. See, for example, EP patent publication No. 0,304,741, which discloses an inline pump for fuel injection systems.

In known fuel injection systems, the pre-delivery pump, the high pressure pump and the flow regulator are connected with each other and/or other components via pipe lines, resulting in a bulk and complex structure as well as a high cost. Summary of Invention

An object of the present invention is to provide an integrated high pressure pump assembly for Common Rail system with a cost-effective compact and simple structure.

For achieving this task, according to one aspect of the invention, a high pressure pump assembly for Common Rail system comprises a casting, a feed pump mounted to the casting for drawing fuel from a fuel reservoir and pre-pressurizing the fuel, a high pressure pumping unit mounted in the casting for receiving the pre -pressurized fuel from the feed pump, further pressurizing the fuel and supplying it to a rail of the Common Rail system, a shared driving means for operatively driving both the feed pump and the high pressure pumping unit, and a flow regulator for controlling the fuel flow which will be pressurized into the rail and the fuel pumping procedure.

The high pressure pump assembly may further comprise an overflow valve, which discharges a portion of the fuel from the high pressure pumping unit when the fuel pressure in the high pressure pump assembly exceeds an upper limit.

The high pressure pumping unit may comprise only one piston type high pressure pump, and the driving means is a camshaft formed with only one cam for operatively driving the piston of the pump.

Alternatively, the high pressure pumping unit comprises at least two piston type inline high pressure pumps, and the driving means is a camshaft formed with cams for operatively driving the pistons of the pump, each cam corresponding to one of the pistons.

The or each high pressure pump may comprise a main body fixed in the casting and defining a piston chamber in which the piston moves reciprocately, an inlet valve allowing the pre-pressurized fuel to be drawn into the piston chamber, and an outlet valve allowing the fuel that has been drawn into the piston and has been further pressurized by the piston to be discharged into the rail, each of the inlet and outlet valves being a check valve, preferably, a ball/conus or flat type of check valve. The or each cam may comprise one, two or more cam lobes which are spaced around the axis of the camshaft by equal angular displacement.

If at least two inline high pressure pumps are provided, the corresponding cams are preferably regularly shifted in a circumferential direction with respect to each other around the axis of the driving shaft.

Preferably, the camshaft is driven by an output of an engine which is supplied with fuel by the Common Rail system.

Preferably, the feed pump is a blade type pump comprises blades driven by the camshaft in rotation. Other types of feed pump may also be used here, for example gear pumps, or electrical feeding pumps.

The feed pump has an inlet coupling for connecting with the fuel reservoir, and the inlet coupling may be sealed by a removable sealing cap when the high pressure pump assembly is not assembled.

According to the present invention, the feed pump, the high pressure pumping unit and the fuel flow regulator are integrated together by the single casting to form a high pressure pump assembly for Common Rail system. Meanwhile, the feed pump and the high pressure pumping unit are driven by the same driving means. Thus, the integrated high pressure pump assembly is compact and simple, and thus is cost-effective.

Brief Description of the Drawings

The foregoing and other aspects of the invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the following drawings, in which:

Fig. 1 is a cross sectional front view of a high pressure pump assembly of the invention;

Fig. 2 is a cross sectional side view of the high pressure pump assembly of Fig. 1 ;

Fig. 3 is a cross sectional front view of a part of a high pressure pumping unit used in the high pressure pump assembly of Fig. 1.

Fig. 4 is a cross sectional front view of a feed pump used in the high pressure pump assembly of Fig. 1; and

Fig. 5 is a cross sectional side view of the feed pump of Fig. 4.

Detailed Description of the Preferred Embodiments

Fig. 1 shows a general arrangement of an embodiment of a high pressure pump assembly of the invention. The high pressure pump assembly forms a component of a Common Rail system for supplying high pressure fuel into a rail (not shown), which in turn injects fuel via injectors into an engine (not shown).

As can be seen, the high pressure pump assembly comprises a feed pump 1, a high pressure pumping unit 2, a fuel flow regulator 3 and a overflow valve 4, all of them being integrated together by a casting 5.

The casting 5 comprises a first housing part 51 defining a first main cavity extending in an transverse direction (left-right direction in Fig. 1), a second housing part 52 defining a second main cavity extending in a longitudinal direction perpendicular to the transverse direction and opening into the first main cavity, and a supplementary attaching part 53 formed on a side of the second housing part 52 and defining a first supplementary cavity opening into the second main cavity and extending perpendicularly to the second main cavity, preferably in the transverse direction, i.e., parallel to the first main cavity, and a second supplementary cavity communicating with the first supplementary cavity via a through hole and extending perpendicularly to the first supplementary cavity, preferably in the longitudinal direction, i.e., parallel to the second main cavity.

The feed pump 1 may have a conventional structure and is mounted to a first end of the generally cylindrical first housing part 51. The fuel flow regulator 3 and the overflow valve 4 may each have a conventional structure and are mounted to the supplementary attaching part 53 communicating with the first and second supplementary cavities respectively. In the embodiment shown in Fig. 1 , the feed pump 1 is a blade pump driven by a driving shaft 10 which also drives the high pressure pumping unit 2. The driving shaft 10 is mounted through the first main cavity in the transverse direction and is rotatably supported near its opposite ends via bearings 14. Both ends of the driving shaft 10 protrude out from the first housing part 51. One end 12 of the driving shaft 10 is a feed pump driving end for operatively driving the blades of the feed pump in rotation and is supported via one of the bearings 14 by one end of the first housing part 51. The other end 15 of the driving shaft 10 is a driven end to be driven in rotation by an output of the engine, preferably via a transmission mechanism such as a gear, belt mechanism or Oldham coupling. The other end 15 of the driving shaft 10 is supported via the other bearing 14 by an end cap 74 fixed to the other end of the first housing part 51. Between the opposite ends of the driving shaft 10 is at least one cam 16 formed integrally on the shaft.

As shown in Fig. 2, a lubricant port 80 is formed at an upper portion of the first housing part 51 , for injecting lubricant into the first main cavity defined in the first housing part 51 to lubricate the moving parts of the high pressure pump assembly, including the driving shaft 10 and corresponding bearings, the roller type driving means 44 and the pistons 30. The lubricant port 80 is sealed by a lubricant port cap 82 which is removed for connecting the pump to the lubrication system of the engine.

The high pressure pumping unit 2 is mounted in the casting 5 and comprises at least one high pressure pump 20 operatively driven by the driving shaft 10. The or each high pressure pump 20 is a piston pump driven by a corresponding cam 16 of the driving shaft 10. The number of the high pressure pump(s) 20 corresponds to the number of the cam(s) 16. In the embodiment shown in Fig. 1, two high pressure pumps 20 are provided and are driven by two cams 16 of the driving shafts 10 respectively. The two cams 16 are formed at axial locations on the driving shaft 10 corresponding to the high pressure pumps 20 and are angularly shifted in a circumferential direction with respect to each other, at different angles, in this case preferable by 90°, around the axis of the driving shaft. Each cam 16 has a earning surface with at least one cam lobe, actually preferably two, as shown which are spaced with each other by different angles, actually preferably by 180° around the axis of the driving shaft. In the actual case,(cam with 2 lobes, spaced with each other at 180°) when the driving shaft 10 rotates one turn, each cam 16 drives the high pressure pump 20 to operate twice, and when one high pressure pump operates to draw in fuel, the other high pressure pump operates to expel out fuel, as later described in details.

If the high pressure pumping unit 2 comprises only one high pressure pump 20, then the rail will be supplied with fuel with fluctuated pressure. Thus, providing several high pressure pumps 20 may reduce the pressure fluctuation in the rail. Generally speaking, according to the present invention, when several high pressure pumps 20 are provided, corresponding number of cams are formed on the driving shaft 10 and are regularly shifted in a circumferential direction with respect to each other around the axis of the driving shaft. Each cam 16 may have one or more cam lobes, preferably two cam lobes. The cam lobes are equally spaced around the axis of the driving shaft.

In the embodiment shown in Fig. 1, the second main cavity of the second housing part 52 is divided into two sub-cavities, each high pressure pump 20 being accommodated in one of the sub-cavities. Each high pressure pump 20 comprises a main body 22 arranged in the sub-cavity and is fixed to the second housing part 52 by screws inserted through through-holes 26 (see Fig.3) formed in a flange 24 of the main body 22. The inner part (the part facing the driving shaft) of main body 22 is formed with a cylindrical piston chamber 28 for receiving a piston 30, and the outer part (the part facing outside) of main body 22 is formed with a valve cavity for receiving a inlet valve 32 and an outlet valve 34. The axis of the piston chamber intersects with and is perpendicular to the axis of the driving shaft 10, thus the piston 30 may reciprocate within the piston chamber in a direction perpendicular to the axis of the driving shaft 10. The piston 30 has a driving end protruding out from the piston camber and connected with a roller type driving means 44 which is biased by a spring 46 against the earning surface of the cam 16. Thus, when the driving shaft 10 rotates, the earning surface of the cam 16 drives the piston 30 via the roller type driving means 44 so that the piston 30 reciprocates in the piston chamber 28.

Each of the inlet valve 32 and the outlet valve 34 is a check valve. In the embodiment shown in Figs. 1 to 3, especially in Fig. 3, they are each a ball type check valve comprising a valve ball as a controlling element. The valve ball is normally biased by a spring, means to block the flow passage way in the valve until a certain pressure is reached; also other types of check valves may also be used. The inlet valve 32 is arranged between and communicates with the piston chamber 28 and the outlet valve 34. The outlet valve 34 is fixed in the main body 22, preferably by screws. The inlet valve 32 is clamped between the outlet valve 34 and the inner part of main body 22 by the outlet valve 34.

The outlet valve 34 has an outlet coupling 36 for attaching a high pressure supply line leading to the rail.

In the embodiment shown in Fig. 3, the inlet valve 32 comprises two valve bodies, i.e., a first valve body holding a spring type ball-biasing means and a valve ball 40 and a second valve body formed with an inner passage way 39 as well as a valve seat against which the valve ball 40 is pushed by the spring type ball-biasing means of the inlet valve. The outlet valve 34 comprises a single valve body, holding a spring type ball-biasing means and a valve ball 42. The outer end of the first inlet valve body is shown as formed with a valve seat against which the valve ball 42 of the outlet valve is pushed by the spring type ball-biasing means of the outlet valve.

When the piston 30 (Fig. 1) moves towards the driving shaft to create a negative pressure in the piston chamber 28, fuel is drawn into the inlet valve 32 through an inlet port 38 (Fig. 3) formed through the outer part of main body 22 and the inner passage way 39 of the inlet valve 32, and can not push up the valve ball 40 against the biasing force of the spring type ball of the inlet valve, and therefore flows only into the piston chamber 28. During this period, the outlet valve 34 is closed by its valve ball 42, and thus the high pressure fuel in the rail cannot flow back through the outlet valve 34.

On the other hand, when the piston 30 moves away from the driving shaft to create a positive pressure in the piston chamber 28, the fuel in the piston chamber is pressurized and forced out from the piston chamber through a channel 41, flows through the inlet valve 32, pushes up the valve ball 42 against the biasing force of the spring type ball of the outlet valve, and then flows towards the rail via the outlet coupling 36. During this period, the inlet is closed by its valve ball 40, and thus the fuel in the piston chamber cannot flow back through inlet port 38.

As shown in Figs. 4 and 5, the feed pump 1, which feeds fuel from a fuel reservoir (not shown) and pre-pressurizes the fuel, has an inlet port 62 for drawing fuel into the feed pump, blades 64 for moving and pre-pressurizing the fuel in the feed pump, and an outlet port 66 for discharge the pre-pressurized fuel from the feed pump. The inlet port 62 is connected with the fuel reservoir via an inlet coupling 72 and a feed line (not shown). The outlet port 66 is connected with the inlet port 38 for the inlet valve 32 via an inner duct 68 formed in the casting 5 from Fig.l. Thus, fuel is drawn from the fuel reservoir and is pre-pressurized by the feed pump l(Fig.4, Fig.5), and then the pre-pressurized fuel is supplied to the high pressure pumping unit 2 (Fig.l) to be further pressurized and supplied to the common at a high pressure, up to 2,000 bars.

The inlet coupling 72 of the feed pump 1 is to be connected with the fuel reservoir via the feed line mentioned above. When the high pressure pump assembly is not assembled in the fuel injection system, the inlet coupling 72 is not connected with the feed line. Thus, the inlet coupling 72 should be sealed to keep any foreign material from coming into the feed pump 1. To this end, a removable sealing cap 70 is attached to the inlet coupling 72. As a result, when the high pressure pump assembly is transported and handled, the feed pump 1 is protected by the removable sealing cap 70. When the high pressure pump assembly is to be assembled into the fuel injection system the removable sealing cap 70 is removed and the inlet coupling 72 is connected to the feed line.

Meanwhile, when the high pressure pump assembly is not assembled in the fuel injection system, the driven end 15 of the driving shaft 10 is protected with a removable shaft-end sealing cap 90 to protect the exposed driven end 15. The removable shaft-end sealing cap 90 is temporarily attached to the driven end 15 by a screw 92.

The flow regulator 3 may be a conventional one, which controls the high pressure in the rail as well as the fuel pumping procedure.

The overflow valve 4 (Fig.l) may also be a conventional over-pressure protection valve. In the condition that the fuel pressure inside the high pressure pump assembly exceeds an upper limit, the overflow valve 4 acts to discharge a portion of the fuel from the high pressure pump assembly. The fuel discharged from the overflow valve 4 flows back to the fuel reservoir.

According to the present invention, the feed pump, the high pressure pumping unit and the flow regulator are integrated together by the single casting to form a high pressure pump assembly for Common Rail system. Meanwhile, the feed pump and the high pressure pumping unit are driven by the same driving means. Thus, the integrated high pressure pump assembly is compact and simple, and thus is cost-effective.

Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.

Claims

1. A high pressure pump assembly for Common Rail system, comprising: a casting, a feed pump mounted to the casting for drawing fuel from a fuel reservoir and pre-pressurizing the fuel, a high pressure pumping unit mounted in the casting for receiving the pre-pressurized fuel from the feed pump, further pressurizing the fuel and supplying it to a rail of the Common Rail system, a shared driving means for operatively driving both the feed pump and the high pressure pumping unit, and a flow regulator for controlling the fuel pressure in the rail and the fuel pumping procedure.

2. The high pressure pump assembly of claim 1 further comprising an overflow valve, which discharges a portion of the fuel from the high pressure pumping unit when the fuel pressure in the high pressure pump assembly exceeds an upper limit.

3. The high pressure pump assembly of claim 1 wherein the high pressure pumping unit comprises a piston type high pressure pump, and the driving means is a camshaft formed with a cam for operatively driving the piston of the pump.

4. The high pressure pump assembly of claim 1 wherein the high pressure pumping unit comprises at least two piston type inline high pressure pumps, and the driving means is a camshaft formed with cams for operatively driving the pistons of the pump, each cam corresponding to one of the pistons.

5. The high pressure pump assembly of claim 3 or 4 wherein the or each high pressure pump comprises a main body fixed in the casting and defining a piston chamber in which the piston moves reciprocately, an inlet valve allowing the pre-pressurized fuel to be drawn into the piston chamber, and an outlet valve allowing the fuel that has been drawn into the piston and has been further pressurized by the piston to be discharged into the rail, each of the inlet and outlet valves being check valve.

6. The high pressure pump assembly of claim 5 wherein the check valve is ball type check valve.

7. The high pressure pump assembly of claim 3 or 4 wherein the or each cam comprises two or more cam lobes which are spaced around the axis of the camshaft by equal angular displacement.

8. The high pressure pump assembly of claim 4 wherein the cams are regularly shifted in a circumferential direction with respect to each other around the axis of the driving shaft.

9. The high pressure pump assembly of claim 3 or 4 wherein the camshaft is driven by an output of an engine which is supplied with fuel by the Common Rail system.

10. The high pressure pump assembly of claim 3 or 4 wherein the feed pump is a blade type pump comprising blades driven by the camshaft in rotation.

11. The high pressure pump assembly of claim 9 wherein the feed pump has an inlet coupling for connecting with the fuel reservoir, and the inlet coupling is sealed by a removable sealing cap when the high pressure pump assembly is not assembled.