WO2015126687A1

WO2015126687A1 - Control module for common rail fuel injection

Info

Publication number: WO2015126687A1
Application number: PCT/US2015/015328
Authority: WO
Inventors: Shiqiang LU; Jiubo Ma
Original assignee: Caterpillar Inc.
Priority date: 2014-02-19
Filing date: 2015-02-11
Publication date: 2015-08-27
Also published as: CN104847512B; CN104847512A

Abstract

The present disclosure discloses a control module (100) for common rail fuel injection. The control module (100) comprises a pilot valve (10) and an actuating mechanism (20), wherein the pilot valve (10) is operable to fluidly connect the actuating mechanism (20) to a common rail (5) maintaining high-pressure fuel or a low-pressure container (3) supplying low-pressure fuel, and the actuating mechanism (20) is configured to permit or inhibit fuel supply from the common rail (5) to the fuel injector (2) in response to operation of the pilot valve (10).

Description

CONTROL MODULE FOR COMMON RAIL FUEL INJECTION Technical Field

The present disclosure relates to a control module for common rail fuel injection, and further to a common rail fuel injection system having such control module.

Background

As compared with a conventional mechanical fuel injection system, a common rail fuel injection system achieves separate control of fuel pressure and timing, so it exhibits a broad prospect for providing diversity to improve performance and meanwhile reduces undesired emission. The common rail fuel system usually employs a plurality of fuel injectors to inject

highly-pressurized fuel to a combustion chamber of an engine.

In the common rail fuel injection system, it is critical that the amount of fuel supplied to the fuel injector is precisely controlled and the high pressure flow of the fuel can be cut off and resumed at a high speed. In a typical common rail system, at the beginning of injection, a desired high pressure for injection is almost achieved immediately.

Currently, a fuel injector integrated with an electrical control device is used universally in the industry. For example, in a fuel injector, a bi-way needle control valve operated by an electrical actuator is used to control a motion of a valve needle for opening and closing a nozzle bore to start and stop the injection event. That is to say, an electromagnetic valve is built in the fuel injector to control the timing of the injection event. Although such structure can achieve the purpose, such integrated structure is relatively complicated and correspondingly the manufacturing and maintenance cost is high. Besides, this unitary structure is relatively precise and imposes a very high requirement for fuel quality. In the event of undesirable fuel quality (e.g., the fuel with high sulfur content), malfunction might occur and undesired emission is caused.

To reduce the cost, there is proposed a solution of using an individual three-way valve to directly control the conventional fuel injector. Fuel injection and cutoff is achieved by connecting the fuel injector to a low-pressure fuel tank or a high-pressure common rail via the three-way valve. Although this structure is simple and easy to operate, a desired high pressure for injection cannot be achieved in a required short time period (a transient switching pressure for communicating with a supply passage is insufficient), and the resultant effect is not satisfactory.

The present disclosure aims to propose an alternative solution to address one or more problems mentioned above and other problems existing in the technical field.

Summary of the Disclosure

According to one aspect, the present disclosure relates to a control module for common rail fuel injection. The control module comprises a pilot valve and an actuating mechanism, wherein the pilot valve is operable to fluidly connect the actuating mechanism to a common rail maintaining high-pressure fuel or a low-pressure container storing low-pressure fuel, and the actuating mechanism is configured to permit or inhibit fuel supply from the common rail to the fuel injector in response to operation of the pilot valve. In an embodiment, the actuating mechanism comprises an actuating member movable in the actuating mechanism between an actuated position in which the actuating member allows supply of the high-pressure fuel from the common rail to the fuel injector and an unactuated position in which the actuating member blocks fluid communication between the common rail and the fuel injector in response to the operation of the pilot valve.

In an embodiment, an injection supply pipeline is provided between the common rail and the actuating mechanism, and in the actuating member is provided an internal passage communicated with the fuel injector so that movement of the actuating member from the unactuated position to the actuated position changes the internal passage and the injection supply pipeline from isolation to communication.

In an embodiment, the pilot valve is a three-way valve operated by a solenoid. The three-way valve selectively communicates the actuating mechanism with the common rail or the low-pressure container via a control pipeline, wherein when the actuating mechanism is communicated with the common rail via the control pipeline, the actuating member is actuated to the actuated position, and when the actuating mechanism is communicated with the low-pressure container via the control pipeline, the actuating member returns to the unactuated position.

Preferably, a pressure relief valve is disposed between the pilot value and the common rail, and the pressure relief valve is located to enable the high-pressure fuel from the common rail to flow into the pilot valve through the pressure relief valve. In an embodiment, the pressure relief valve is located downstream the injection supply pipeline. Preferably, a diameter of the injection supply pipeline is greater than a diameter of the control pipeline.

According to an embodiment, the actuating mechanism further comprises an upper control chamber fluidly connected to the control pipeline and a lower control chamber fluidly connected to the fuel injector, and the actuating member has an opening hydraulic surface exposing to a pressure in the upper control chamber and a closing hydraulic surface exposing to a pressure in the lower control chamber, and an effective action area of the opening hydraulic surface is greater than an effective action area of the closing hydraulic surface.

According to an embodiment, in a main body of the actuating mechanism is further formed an internal passage communicated with the injection pipe pipeline, and when the actuating member is in the actuated position, the internal passage of the actuating member is communicated with the internal passage in the main body.

According to another aspect, the present disclosure relates to a common rail fuel injection system, comprising a low-pressure container for housing low-pressure fuel, a common rail for receiving high-pressure fuel which comes from the low-pressure container and is subjected to pressurization, a fuel injector for injecting the high-pressure fuel received from the common rail on demand, and the above-mentioned control module for controlling injection of the fuel injector.

Brief Description of Drawings

Other features and advantages of the present disclosure will be made more apparent by the following description of embodiments which are exemplary but non-limiting with reference to the drawings, in which: Fig. 1 is a schematic diagram of a common rail fuel injection system according to the present disclosure;

Fig. 2 is a schematic diagram in which a control module for the common rail fuel injection system of the present disclosure is in a closed position; and

Fig. 3 is a schematic diagram illustrating that the control module of Fig. 2 is in an open position.

Detailed Description

Exemplary embodiments of the present disclosure are described in detail below with reference to figures. In the figures, the same reference numerals denote the same element. It may be appreciated that figures are for illustration purpose and are not drawn in scale.

Referring to Fig. 1 , it shows a common rail fuel system 1. The common rail fuel system 1 comprises fuel injectors 2 associated with each of a plurality of cylinders (not shown) of the engine. Fuel may be compressed for ignition in the cylinders in a conventional manner. Although the figure shows six rail passages for use in a fuel common rail system of an engine having six cylinders, the present disclosure may be applied to an engine with any number of cylinders. The common rail fuel system 1 comprises a low-pressure container 3 (namely, fuel tank) for receiving fuel, the low-pressure container 3 supplies low-pressure fuel to a high-pressure pump 4 via a pump supply pipeline LI, the pump supply pipeline LI may comprise a delivery pump, a filter, a cooler (not shown), and the like. The high-pressure pump 4 is controlled to supply pressurized fuel to the common rail 5 via a rail supply pipeline L2. The respective fuel injectors 2 are selectively communicated with the high-pressure common rail 5 via a control module 100 connected at a high pressure inlet of each fuel injector 2 to execute or cutoff injection event according to needs.

Each fuel injector 2 may be equipped with a control module 100.

Referring to Fig. 2, it illustrates a schematic diagram of the control module 100 according to the present disclosure. As shown in the figure, the control module 100 comprises a pilot valve 10 and an actuating mechanism 20. In the illustrated embodiment, the pilot valve 10 is a three-way valve 10 actuated by a solenoid 40, and it comprises a first port 50 connected to the common rail 5, a second port 60 connected to the low-pressure container 3, and a common third port 70. A valve plug of the valve 10 is operated by energization or

de-energization of the solenoid 40 to, in combination with action of a return spring 41, achieve selective communication of the third port 70 with the first port 50 or the second port 60. The control module 100 may be put in an open position by energization of the solenoid 40 and put in a closed position by de-energization of the solenoid. In the illustrated embodiment, energization and de-energization of the solenoid 40 may be achieved by an operating mechanism 7 as shown in Fig. 1. It may be appreciated that although the figure shows a three-way valve operated by the solenoid, those skilled in the art may envisage other specific valve structures. Furthermore, the three-way valve operated by the solenoid 40 is also known and it will not be described in detail herein.

Further referring to Fig. 2, an injection supply pipeline L3 is provided between the common rail 5 and the actuating mechanism 20, and a control pipeline L4 is provided between the pilot valve 10 and the actuating mechanism 20. Specifically, the actuating mechanism 20 comprises an actuating member 21 axially mo vably disposed in a main body 90. The actuating member 21 partitions an interior of the actuating mechanism 20 into an upper control chamber 31 and a lower control chamber 32 isolated from each other, and has an opening hydraulic surface 22 exposing to the fluid pressure in the upper control chamber 31 and a closing hydraulic surface 23 exposing to the fluid pressure in the lower control chamber 32. The upper control chamber 31 is fluidly connected to the third port 70 of the valve 10 via the control pipeline L4. The lower control chamber 32 is in fluid communication with the fuel injector 2. The actuating member 21 is moveable in the main body 90 between an unactuated position (as shown in Fig. 2) and an actuated position (as shown in Fig. 3) under action of fluid pressure in the upper control chamber 31 and the lower control chamber 32. In the illustrated embodiment, the actuating member 21 is axially movably disposed in a plunger 21. In the actuating member 21 is formed an internal passage L5 for connecting outlet fluid to the fuel injector 2, and an internal passage L6 is formed in main body 90. The injection supply pipeline L3 is in fluid communication with the internal passage L6.

As can be seen from the above, when the control module 100 is closed as shown in Fig. 2, the actuating member 21 is in an unactuated position, whereupon the internal passages L5 and L6 are not aligned, the high-pressure fuel from the common rail 5 cannot be communicated to the fuel injector 2. When the control module 100 is open as shown in Fig. 3, the actuating member 21 is in the actuated position, an inlet of the internal passage L5 aligns with an outlet of the internal passage L6 so that fluid communication is achieved between two internal passages such that the high-pressure fuel is communicated to the fuel injector from the common rail 5 via the injection supply pipeline L3 and the internal passages L5, L6.

As shown in the figure, the pilot value 10 and the actuating member 20 are formed as a one-piece member, but those skilled in the art may understand that the pilot valve 10 and the actuating member 20 may also be formed as separate members which are then connected together.

In an embodiment, a pressure release valve 6 is provided between the common rail 5 and the first port 50 of the valve 10 and located downstream of the supply pipeline L3 to reduce pressure of the control fluid flowing through the value 10, and meanwhile the high-pressure fuel coming from the common rail and used for injection is not affected by the pressure release valve 6. As known from the above, the fuel which comes from the common rail and which pressure is reduced is used as the control fluid here. As an example, the fuel pressure in the common rail may be for example 106MPa, and the pressure of the control fluid for example may be in a range of 1-lOMPa. Since the pressure of the control fluid is substantially reduced via the pressure relief valve 6, a diameter of the control pipeline L4 may be preferably formed less than a diameter of the supply pipeline L3 to reduce pressure fluctuation of the injection fuel caused by the control pipeline and ensure transient supply of the high-pressure fuel for injection.

In addition, the opening hydraulic surface 22 may be designed in a way that an effective action area is greater than an effective action area of the closing hydraulic surface 23 so that the actuating member 21 is movable back and forth between the unactuated position and the actuated position only under action of differential pressure of the upper control chamber 31 and the low control chamber 32. In an example, a ratio of area of the opening hydraulic surface 22 to the closing hydraulic surface 23 may be greater than 10: 1. Certainly, those skilled in the art may envisage providing an additional return spring to assist the actuating member 21 in returning to the unactuated position. Industrial applicability

The control module of the present disclosure may be specifically applied to a common rail fuel injection system having universal performance requirements, and these performance requirements include a capability to precisely control fuel injection amount and a capability to quickly open or cut off fuel supply in a very short time period. Operation of the control module 100 according to the present disclosure will be described with reference to the figures.

When fuel injection is desired, the control module 100 is put in the open position as shown in Fig. 3 by energizing the solenoid 40. Specifically, the solenoid 40 is energized so that the valve plug of the valve 10 moves to a position allowing for fluid communication of the third port 70 and the first port 50. At this time, the high-pressure fuel coming from the high pressure common rail 5, after being subjected to pressure reduction by the pressure relief valve 6, passes through the valve 10, and then enters the upper control chamber 31 of the actuating mechanism 20 through the control pipeline L4. As the control fluid enters the upper control chamber 31 , a pressure acting upon the opening hydraulic surface 22 of the actuating member 21 is made greater than a pressure acting upon the closing hydraulic surface 23 so that the actuating member 21 axially moves from the unactuated position shown in Fig. 2 to the actuated position shown in Fig. 3 to align and communicate the internal passage L5 with the internal passage L6. As such, the high-pressure fuel may enter the fuel injector 2 from the common rail 5 via the injection supply pipeline L3 and the internal passages L5, L6 so as to activate the injection event of the fuel injector and inject fuel into the combustion chamber of the engine.

When the fuel injection is desired to be stopped, the control module 100 is put in the closed position as shown in Fig. 2 by de-energizing the solenoid 40. Specifically, the de-energization of the solenoid 40 causes the valve plug of the valve 10 to move due to action of the return spring 41 to make the third port 70 in fluid communication with the second port 60. As such, the fluid in the upper control chamber 31 is discharged to the low-pressure container 3 via the control pipeline L4 and the valve 10. As the pressure of the fluid in the upper control chamber 31 decreases, the actuating member 21 returns, under the prevailing pressure of the fuel in the lower control chamber 32, from the actuated position shown in Fig. 3 to the unactuated position as shown in Fig. 2 so that the internal passages L5, L6 no longer align and communicate with each other such that the fluid communication between the fuel injector 4 and the supply pipeline L3 is cut off and the fuel injector stops injecting.

Due to the control module of the present disclosure, any standard conventional mechanical injector of a lower cost may be used in the common rail fuel injection system, and a unitary valve controlled by the solenoid needn't be built inside the injector. This not only substantially cuts the cost, and

furthermore, the common rail fuel injection system better suits fuel of poorer quality and reduces occurrence of malfunctions. More importantly, due to use of the control module of the present disclosure, the pressure of the fuel supplied to the injector may have an excellent response to the action of the control module, supply and cutoff of the high-pressure fuel satisfying the injection pressure may be achieved in a period of milliseconds or a period less than one millisecond, and meanwhile, undesired emission is reduced.

Therefore, present disclosure proposes an alternative which is of lower cost than, exhibits a stronger adaption to fuel quality than and meanwhile has a comparable performance with the unitary electronic controlled fuel injector. Although the present disclosure is described by way of exemplary embodiments, the present disclosure is not limited to the details described as above. Hence, corresponding modifications and variations to the present disclosure made by those skilled in the art according to the teaching here all fall within the scope of the present disclosure.

Claims

1. A control module (100) for common rail fuel injection, comprising:

a pilot valve (10); and

an actuating mechanism (20),

wherein the pilot valve (10) is operable to fluidly connect the actuating mechanism (20) to a common rail (5) maintaining high-pressure fuel or a low-pressure container (3) storing low-pressure fuel, and the actuating mechanism (20) is configured to permit or inhibit fuel supply from the common rail (5) to a fuel injector (2) in response to operation of the pilot valve (10).

2. The control module (100) according to claim 1, wherein the actuating mechanism (20) comprises an actuating member (21) movable in the actuating mechanism between an actuated position in which the actuating member (21) allows supply of the high-pressure fuel from the common rail (5) to the fuel injector (2) and an unactuated position in which the actuating member (21) blocks fluid communication between the common rail (5) and the fuel injector (2) in response to the operation of the pilot valve (10).

3. The control module (100) according to claim 2, wherein an injection supply pipeline (L3) is provided between the common rail (5) and the actuating mechanism (20), and in the actuating member (21) is provided an internal passage (L5) communicated with the fuel injector (2) so that movement of the actuating member (21) from the unactuated position to the actuated -Im

position changes the internal passage (L5) and the injection supply pipeline (L3) from isolation to communication.

4. The control module (100) according to any one of claims 1-3, wherein the pilot valve (10) is a three-way valve operated by a solenoid (40), the three-way valve selectively communicates the actuating mechanism (20) with the common rail (5) or the low-pressure container (3) via a control pipeline (L4), wherein when the actuating mechanism (20) is communicated with the common rail (5) via the control pipeline (L4), the actuating member (21) is actuated to the actuated position, and when the actuating mechanism (20) is communicated with the low-pressure container (3) via the control pipeline (L4), the actuating member (21) returns to the unactuated position.

5. The control module (100) according to any one of claims 1-3, wherein a pressure relief valve (6) is disposed between the pilot value (10) and the common rail (5), and the pressure relief valve (6) is located to enable the high-pressure fuel from the common rail (5) to flow into the pilot valve (10) through the pressure relief valve (6).

6. The control module (100) according to any one of claims 1-3, wherein a diameter of the injection supply pipeline (L3) is greater than a diameter of the control pipeline (L4).

7. The control module (100) according to any one of claims 1-3, wherein the actuating mechanism (20) further comprises an upper control chamber (31) fluidly connected to the control pipeline (L4) and a lower control chamber (32) fluidly connected to the fuel injector, and the actuating member (21) has an opening hydraulic surface (22) exposing to a pressure in the upper control chamber (31) and a closing hydraulic surface (23) exposing to a pressure in the lower control chamber (32), and an effective action area of the opening hydraulic surface (22) is greater than an effective action area of the closing hydraulic surface (23).

8. The control module (100) according to claim 3, wherein in a main body (90) of the actuating mechanism (20) is further formed an internal passage (L6) communicated with the injection pipe pipeline (L3), and when the actuating member (21) is in the actuated position, the internal passage (L5) of the actuating member is communicated with the internal passage (L6) in the main body (90).

9. A common rail fuel injection system (1), comprising:

a low-pressure container (3) for housing low-pressure fuel;

a common rail (5) for receiving high-pressure fuel which comes from the low-pressure container (3) and is subjected to pressurization;

a fuel injector (2) for injecting the high-pressure fuel received from the common rail (5) on demand; and

a control module (100) for controlling injection of the fuel injector (2) according to any one of claims 1-8.