HK1142648A - Multiple intensifier injectors with positive needle control and methods of injection - Google Patents

Description

Multi-stage intensifier injector with active needle control and method of injection

Cross Reference to Related Applications

This application claims priority from U.S. provisional patent application No.60/928,578 filed on 9/5/2007.

Technical Field

The present invention relates to the field of fuel injectors.

Background

Enhanced fuel injectors are well known in the art. Such injectors utilize a larger first piston driven by pressurized working fluid to drive a smaller piston to pressurize fuel for injection. A piston area ratio of typically 10 to 1 (and hence a intensification ratio of typically 10 to 1) allows high injection pressures to be achieved with only a modest pressure of the working fluid. Diesel fuel can be properly compressed at applicable pressures. For example, diesel fuel compresses approximately 1% per applied 1000 pounds per square foot (psi). At injection pressures of 30000 psig and above 30000 psig, the fuel can be fully compressed. The energy required for compression of fuel not used for injection is typically wasted by venting the working fluid through the larger piston of the intensifier to a low pressure reservoir. Thus, when the engine is operating at substantially less than full power, a significant portion of the energy used to compress the entire injected fuel is wasted.

In addition, in the diesel fuel injector, it is important to realize rapid start and stop of injection. A slower termination of injection, for example, caused by a slow reduction in injection pressure, will result in less effective atomization, or even failure to achieve true atomization at the end of injection, resulting in incomplete combustion of the fuel and unacceptable unburned hydrocarbon emissions.

Drawings

FIG. 1 is a cross-sectional view of one embodiment of the present invention.

Fig. 2 is a cross-sectional view of the embodiment of fig. 1, showing a half section at 90 degrees apart.

Fig. 3 is a cross-sectional view of another embodiment of the present invention.

Detailed Description

Figures 1 and 2 show an injector according to the invention. These figures show the injector in the needle open position during injection. Fig. 1 is a cross-sectional view of an ejector with two intensifiers, while fig. 2 is a cross-sectional view of the same ejector, the right side of the figure representing the same cross-section, and the left side of the figure representing a cross-section that is 90 degrees turned over from the right side. In this injector, a needle 20 is provided, which needle 20 is almost pressure-balanced, so that when fuel at the injection pressure is present in the needle chamber surrounding the needle 20, a relatively moderate upward force will be present on the needle.

Fuel is supplied to the needle chamber 21 in the injector cup 22 from either or both of the intensifier chambers 28 and 29 through the port 24 and the recess 26. Intensifier pistons 30 and 32 have return springs 34 and 36 and are fueled when intensifier pistons 30 and 32 return to the upper position through check valves 38 and 40. The intensifier is actuated by pistons 42 and 44 controlled by control valves 46 and 48, respectively, the control valves 46 and 48 preferably being solenoid actuated spool valves. If fuel is provided to the needle chamber 21 by only one intensifier through the passage controlled by the check valve and passage 24, the other of the check valves 50 and 52 will close, preventing the intensified pressure from combining with the non-operating intensifier.

The use of two intensifiers spaced radially outward from the center of the injector has the advantage of allowing direct control of the needle through the axis of the injector. Specifically, a member 54, which may include one or more portions (more than one portion shown), extends from the top of the needle 20 all the way to a pressure chamber 56 at the top of the injector. Thus, when fluid control valve 58 is actuated to apply pressure to pressure chamber 56, member 54 is hydraulically urged downward to close the needle by fluid pressure acting on the top piston area of member 54, the components being proportioned in the preferred embodiment to ensure that the needle is positively closed against the increased pressure in the needle chamber.

For the initial needle closing process, an acceleration system is used, ensuring a rapid needle closing process. In particular, the hydraulic pressure in the chamber 56 also acts on the top of the member 60, accelerating the piston (as can be seen from the left in fig. 2) pushing the pins 62 downwards (only one of the pins 62 is shown in fig. 2, since the other half-section is turned 90 degrees from this section). Pin 62 in turn pushes pin 64, pin 64 pushes member 66, and member 66 pushes needle 20 toward the closed position. However, the bottom of the part 66 will hit the top of the part 26 before the needle is finally closed, which substantially reduces the impact of the needle closing process, allowing the needle to be closed very quickly without the risk of the spray head falling out of the needle chamber. It is noted that the stop of the acceleration assembly is relatively close to the needle, thereby minimizing the effects of differential expansion so that the acceleration assembly can be repeatedly operated before the needle closes. However, the control valve 58 is located at the top of the injector, simplifying the electrical connection to the control valve. In addition, since all control valves, preferably solenoid actuated spool valves, are similarly positioned, the actuation coils for the three valves may be printed on a multilayer printed circuit board, further simplifying the electrical interconnection of the components to one another. Also, the use of two intensifier assemblies allows for a smaller (faster) control valve to be used.

Needle 20 may be urged downward to a closed position, independent of the pressure in the needle chamber surrounding the needle, by control of control valve 58. Coil spring 68 (a relatively light coil spring) merely ensures that needle closing pin 54 remains stationary against the needle regardless of whether the needle is open or closed.

Thus, when closing the needle in the presence of intensified fuel, control valve 58 is opened to provide fluid pressure in chamber 56 to accelerate pin 54 and the aforementioned acceleration assembly toward the closed position, stopping the acceleration assembly just before the needle reaches the closed position, thereby greatly reducing inertia and thus reducing shock during needle closure. In a preferred embodiment, the activation fluid for intensifier pistons 42 and 44, pin 54, and member 60 is engine oil (engine oil), although other fluids (e.g., fuel) may be used if desired.

As previously mentioned, the use of two intensifier assemblies has many advantages. If the intensification ratios are different, two different injection pressures may be selectively achieved by operating one or the other intensifier with one actuation fluid pressure. Even if the two intensifier assemblies have the same intensification ratio, they still have advantages. In particular, fuel injectors generally require sufficient power. In the prior art, the intensifier is typically operated once each injection is made, and then the pressure is reduced to refill the intensifier chamber with fuel. Obviously, the intensification chamber must be large enough to intensify enough fuel for one injection at the maximum demand of the engine. Since injection pressures of 30000 psi or higher are used or required, fuel is typically compressed by approximately 1% per 1000 psi, so that the fuel to be injected is compressed by approximately 20% -30%. In addition, to compress the injected fuel, there is some general space (overlap volume) associated with the intensified fuel, including the passage that carries the intensified fuel to the needle chamber and the needle chamber itself. In the prior art, all of the energy required to pressurize the fuel for maximum injection is used regardless of engine operating conditions, even when the engine is idling.

In the present invention, however, it is possible to operate only one intensifier assembly at lighter engine loads where only less fuel must be provided to the combustion chamber, thereby enabling a 50% reduction in the power required by the injector given that not only the intensification ratios of the two intensifier assemblies are the same, but also the diameters of the intensifier pistons are the same.

Alternatively, the intensification ratios of the two intensifier assemblies may be the same, although one may have twice the area or stroke of the other (FIG. 3), or some combination of different areas and strokes to have twice the intensified fuel volume of the other. Now, when full injection is required, two intensifier assemblies may be used. When the engine is operating at a lighter load, only a larger intensifier assembly may need to be used, and when the engine is operating at a lighter load, only a smaller intensifier injection assembly may need to be used, thereby saving a significant amount of energy compared to that required by prior art injectors.

Another manner of operation of the injector according to the present invention or a single intensifier assembly injector with direct needle control will now be described. First, a sufficient amount of fuel is intensified to at least meet the maximum injection demand for one injection of the engine. (one injection event may include, for example, a pilot injection followed by a main injection.) however, when the engine is operating at a lighter load, the drive fluid pressure on the intensifier is simply maintained, but the injection itself is controlled by controlling the injection needle, as in the manner shown in FIGS. 1, 2 and 3; rather than depressurizing and re-pressurizing the fuel for injection by depressurizing and re-pressurizing the intensifier assembly as is done today.

This operation saves most of the power required to operate the injector by simply boosting once for multiple injections, the number of injections depending on the engine load and simply determined by the controller controlling the amount of fuel injected at each injection. For example, when using the present invention at idle, perhaps only one intensifier assembly may need to be operated before the intensifier pressure needs to be reduced to refill the fuel for intensification required for a subsequent injection, and one intensification may provide six or more injections. Therefore, the energy used in the strengthening process can be easily obtained according to the engine load situation, and the energy is greatly reduced when the engine load is greatly reduced. Thus, while the prior art intensifies the maximum amount of fuel required by the engine, whether or not maximum fuel injection is required, the present invention may either only intensify a roughly required amount of fuel, or intensify a greater amount of fuel than required for one injection, but the intensification will remain for two or more injections, or both. The electronic control system for the injector valve can easily keep track of the amount of fuel injected per injection and thus predict when re-intensification is needed without the need for feedback measurements. For example, the electronic control may determine whether sufficient intensified fuel remains for an equal injection after one injection. If so, boosting continues after the needle controller closes the injection needle and the next injection is completed by the needle controller, the injection is limited to the amount of fuel that can be injected at the boost pressure if the engine power setting has increased.

Thus, while certain preferred embodiments of the present invention have been disclosed and described herein for purposes of illustration and not for purposes of limitation, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

Claims (15)

1. A fuel injector, comprising:

a needle positioned in the needle chamber;

a first booster and a second booster;

first and second check valves configured to prevent either intensifier from intensifying fuel in the other intensifier;

first and second control valves for controllably connecting pressurized activation fluid to the first and second intensifiers, respectively;

a needle control pin extending between the first and second intensifiers and to a top of the injection needle; and

a needle control valve for controllably connecting an activation fluid to an end of the needle control pin opposite the top of the needle, the needle and the needle control pin being proportioned to maintain the needle closed when a pressurized activation fluid is connected to the end of the needle control pin opposite the top of the needle and the needle chamber contains fuel at an intensified pressure.

2. The fuel injector of claim 1, further comprising an acceleration piston, the needle control valve further controllably connecting an activation fluid to the acceleration piston, the acceleration piston connected to move the needle from an open position toward a closed position, the acceleration piston limited in movement as the needle approaches the closed position to stop moving the needle toward the closed position.

3. The fuel injector of claim 1, wherein the first and second intensifiers are the same size.

4. The fuel injector of claim 1, wherein the first and second intensifiers have the same intensification ratio.

5. The fuel injector of claim 4, wherein the first and second intensifiers have different intensified fuel volumes.

6. The fuel injector of claim 5, wherein the different intensification volumes are caused, at least in part, by different areas of the first and second intensifiers.

7. The fuel injector of claim 5, wherein the different intensification volumes are caused at least in part by different strokes of the first and second intensifiers.

8. A method of operating a fuel injector having a direct needle controller in an engine, the method comprising:

a) pressurizing an amount of fuel to injection pressure when the engine is operating at full power, the amount of fuel being sufficient for at least one injection;

b) controlling injection by the direct needle controller;

c) maintaining the pressure of the fuel for a subsequent injection when the amount of pressurized fuel remaining after the injection is at least sufficient for the subsequent injection; and

d) when the amount of pressurized fuel remaining after injection is insufficient for a subsequent injection, the pressure of the fuel is reduced and steps a) through d) are repeated.

9. The method of claim 8, wherein the fuel injector is an intensifier injector and in step a) the pressurization is controlled by controlling the activation fluid for the intensifier.

10. The method of claim 9, wherein the priming fluid is engine oil.

11. The method of claim 9, wherein the starting fluid is fuel.

12. A method of operating a fuel injector having a direct needle controller in a diesel engine, the method comprising:

a) pressurizing an amount of fuel to injection pressure when the diesel engine is operating at full power, the amount of fuel being sufficient for at least one injection;

b) controlling injection by the direct needle controller;

c) maintaining the pressure of the fuel for a subsequent injection when the amount of pressurized fuel remaining after the injection is at least sufficient for the subsequent equivalent injection; and

d) when the amount of pressurized fuel remaining after injection is insufficient for a subsequent equivalent injection, the pressure of the fuel is reduced and steps a) to d) are repeated.

13. The method of claim 12, wherein the fuel injector is an intensifier injector and in step a) the pressurization is controlled by controlling the activation fluid for the intensifier.

14. The method of claim 13, wherein the priming fluid is engine oil.

15. The method of claim 13, wherein the starting fluid is fuel.