NL1041735B1

NL1041735B1 - Rotating fuel injector assembly.

Info

Publication number: NL1041735B1
Application number: NL1041735A
Authority: NL
Inventors: Tjeerd Sijtse Ijsselstein Ing
Original assignee: Cereus Tech B V
Priority date: 2016-02-25
Filing date: 2016-02-25
Publication date: 2017-09-11

Abstract

This invention provides a method and device for engaging and disengaging the power transmission from the shaft of an actuator, the drive shaft, to the shaft of a rotatable fuel injector of an internal combustion engine, the driven shaft. In order to overcome the breakaway torque required for setting the rotatable fuel injector in motion an embodiment of the method according to the invention comprises using an assembly with a flywheel. The rotating fuel injector assembly further comprises an engagement assembly that allows a certain degree of axial movement of the driven shaft relative to the drive shaft.

Description

ROTATING FUEL INJECTOR ASSEMBLY

FIELD OF THE INVENTION

The present invention relates to a rotating fuel injector assembly for internal combustion engines. More in particular it relates to the support of the actuator that drives the rotation of the fuel injector, to the nature of the actuator, to methods of leveraging the power of the actuator in order to overcome the breakaway torque of the rotatable fuel injector and to the coupling between the actuator and the rotatable fuel injector.

BACKGROUND OF THE INVENTION

Internal combustion engines are important sources of harmful emissions such as C02, NOx and particulate matter (PM). A part of the emissions is inherent to the combustion of hydrocarbon fuels. However, the emission of for example PM can be prevented by ensuring complete combustion inside combustion chamber of engines. Dutch patent NL 2001069 describes a method and device for injecting fuel into a combustion chamber through a rotating fuel injector, which results in thorough mixing between the injected fuel and the combustion air inside the combustion chamber. If executed properly, this injection method results in complete combustion of the fuel and, hence, in the prevention of the formation and the emission of particulate matter and thermal NOx. But this new, rotating, fuel injection method presents a challenge in terms of the required starting torque to set the rotatable fuel injector in motion. Furthermore, coupling of the actuator to the fuel injector and isolating the actuator from the harsh vibratory conditions of the injector are serious concerns. Therefore, it is an object of the present invention to provide solutions for the aforementioned challenges.

SUMMARY OF THE INVENTION

This invention provides a method and device for engaging and disengaging the power transmission from the shaft of an actuator, the drive shaft, to the shaft of a rotatable fuel injector of an internal combustion engine, the driven shaft.

In order to overcome the breakaway torque required for setting the rotatable fuel injector in motion the method according to the invention comprises starting up the actuator and letting it reach a certain rotational speed with or without a flywheel before establishing an engagement between the drive shaft and the driven shaft. Furthermore, the present invention comprises an engagement assembly that allows a certain degree of axial movement of the driven shaft relative to the drive shaft while rotating and prevents or at least minimizes the axial transfer of vibrations from the fuel injector to the actuator.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings, in which: - FIG. lisa schematic representation of an embodiment of an assembly according to the invention; FIG. 2 is a schematic representation of an embodiment of an assembly according to the invention; FIG. 3 is a schematic representation of an embodiment of an assembly according to the invention with two actuators; FIG. 4 shows a schematic representation of an actuator with an embodiment of a pin coupling; - FIG. 5 is a schematic representation of an embodiment of an hydraulic suspension device for an actuator of an assembly according to the invention.

Identical or similar parts have been designated with identical or similar reference numbers.

DETAILED DESCRIPTION OF THE INVENTION

The required breakaway torque to set a rotatable fuel injector of for example a 240 kW diesel engine in motion will normally be in the range of 200 to 300 Watt. Providing each of the usually 6 or 8 fuel injectors of such an engine with an actuator with a power rating of 200 to 300 Watt is relatively expensive and difficult in view of the constraints in the space that is available for mounting the actuators. In addition, since, once the fuel injector rotates at the desired speed the required power that is exerted on the driven shaft for it to retain that rotational speed will normally be in the range of only 8 to 15 Watt, it seems rather inefficient to install actuators with a power rating that is roughly a factor twenty higher.

It is, therefore, an object of this invention to provide a means of starting up the rotation of a fuel injector using an actuator with a power of for example maximum a factor two higher than the power needed for maintaining the desired rotational speed. The invention comprises the use of any suitable type of actuator, including but not limited to for example an electric motor, an hydraulic motor or a turbine driven by a liquid or a gas, such as for example air. The method for providing the required breakaway torque for starting up the rotation of a rotatable fuel injector of an internal combustion engine according to the invention comprises using the kinetic energy stored in a flywheel, a mechanical device capable of storing rotational energy, connected to the rotating drive shaft of an actuator by creating an engagement between this rotating drive shaft and the still stationary shaft of the rotatable fuel injector. FIG. 1 is a schematic representation of a part of an embodiment of an assembly according to the invention comprising an actuator 1 with a drive shaft 2, a flywheel 3, engagement means 4 and a driven shaft 5. In selecting the flywheel 3 a compromise will have to be made with respect to the moment of inertia. In an embodiment the flywheel 3 is rigidly connected coaxially to the drive shaft 2. In an embodiment the first end, in FIG. 1 the top end, of the engagement means 4 is configured to receive and rigidly attach to the drive shaft 2 and the second end of the engagement means 4 comprises a splined or serrated hub that, when the engagement means are activated is connected rotatably to the drive shaft 2. In this embodiment the top end of the driven shaft 5 comprises a splined or serrated section which can engage with the splined or serrated hub of the engagement means 4. This provides a backlash free rotational coupling between the driven shaft 5 and the splined or serrated hub, but still allows small bidirectional axial movements of the driven shaft 5 relative to the engagement means 4. Such axial movement within the splined or serrated connection may be useful in preventing the transfer of vibratory forces from the fuel injector onto the actuator. In the embodiment discussed above the drive shaft 2 is rigidly connected to the engagement means 4 and the driven shaft is axially movable within the engagement means. It should be mentioned that the invention may include any other suitable type of engagements between respectively the drive shaft and the driven shaft and the engagement means 4.

On the one hand the moment of inertia of the flywheel 3 shall be small enough to allow a relatively low power actuator to get the flywheel rotating at the desired rotational speed as quickly as possible and on the other hand the moment of inertia shall be sufficient to overcome the breakaway torque of the rotatable fuel injector. In an embodiment of the method and assembly according to the invention the engagement means 4 comprise a locking type of engagement which creates a high impact torque on the shaft of the fuel injector upon engaging. In another embodiment the engagement means provide for a more gradual engagement for example through a slipping, clutch type of power transmission. In the latter type of power transmission the impact torque obviously will be lower than in the locking type of engagement. Since providing each rotatable fuel injector of an internal combustion engine with engagement means that have to be activated manually is impractical, various embodiments of the engagement means according to the invention comprise for example rotational speed dependent mechanisms for establishing a locking engagement between the drive shaft of an actuator and the driven shaft of a fuel injector automatically. One example of such a rotational speed dependent automatic locking mechanism comprises a mechanical locking mechanism that is operated centrifugally to provide a locking engagement between the axially-aligned drive shaft 2 and driven shaft 5. In an embodiment the engagement means 4 comprise adjustment means for setting the rotational speed threshold above which the locking engagement between the drive shaft 2 and the driven shaft 5 will be activated and remains activated until the rotational speed drops to a level below the threshold.

Instead of an automatic locking engagement and disengagement that is incorporated in the construction of the coupling, as is the case in for example a centrifugal coupling, the invention also comprises coupling means that are operated by an external signal. Examples of the latter type of couplings include, but are not limited to, liquid and magnetic couplings.

In another embodiment of the rotating fuel injector assembly according to the invention the connection between the flywheel 3 and the drive shaft 2 may disengage automatically when the rotational speed exceeds the earlier mentioned threshold rotational speed required for activating the locking engagement between the drive shaft 2 and the driven shaft 5. This may be achieved by using a so-called freewheel clutch or overrunning clutch. The disengagement of the flywheel during steady state operation of the rotating fuel injector saves energy that would otherwise be required to rotate the flywheel and may limit the amount of wear of the actuator. The engagement means to engage and disengage the flywheel may comprise a freewheel clutch which may either be installed as a separate component or may be integrated in the flywheel.

The assembly according to the invention may also comprise embodiments in which the flywheel 3 and/or the engagement means 4 are integrated in the actuator 1. FIG. 1 shows an embodiment of the assembly in which the flywheel 3 is positioned below the actuator. However, the invention also includes embodiments in which the flywheel is positioned on top of the actuator as schematically shown in FIG. 2.

While the schematic representations in FIG. 1 and FIG. 2 show embodiments of the assembly according to the invention with only one actuator, the invention also comprises embodiments of the assembly with at least two actuators. FIG. 3 is a schematic representation of an embodiment of an assembly according to the invention with two actuators. The second actuator 6 may be of any suitable type with a high torque at low rotational speeds, such as for example a stepper motor, which can provide the breakaway torque required to set the rotation of the fuel injector in motion and reach a rotational speed of for example in the order of 2000 rpm. Subsequently, the second actuator 6 can be disengaged and the first actuator 1 of a type that can achieve the high rotational speeds required for the best performance of the rotating fuel injector can be engaged. The engagement means 8, also referred to as the second engagement means 8, between the shaft 7 of the second actuator 6 and the shaft 2 of the first actuator 1 may comprise for example a freewheel or overrunning clutch. As such, it is not the aim that the shaft 7 of the second actuator is connected to the drive shaft 2 of the first actuator 1, but rather, that during start-up of the rotation of the assembly the shaft 7 of the second actuator is rotatably connected with the shaft 5 of the rotatable injector. This may be through the drive shaft 2 of the first actuator and/or through other intermediate components. Therefore, to reflect these options the connection between the drive shaft 7 of the second actuator 6 and the shaft 5 of the rotatable fuel injector may be referred to as a direct or indirect connection.

The actuators of a multi actuator embodiment of the assembly according to the invention may also be integrated into one single unit.

In the embodiment shown in FIG. 3 a sensor 9 for measuring the rotational speed has been installed on the driven shaft 5 of the rotatable fuel injector. Such a sensor may comprise for example a Hall effect sensor or any other suitable rotational speed measuring device of which the output signal can be fed to the on-board diagnostics (OBD) of the vehicle in which the engine in question is installed. The sensor can signal to the OBD whether the fuel injector is rotating and whether it is rotating within the required rotational speed range for clean combustion. The OBD can record the rpm history of each rotatable fuel injector, thereby providing traceability and proof of operating within the required rpm range for clean combustion, and hence justification of the omission of after-treatment of the exhaust gases.

In the embodiments discussed above the direct or indirect connection of the driven shaft of the rotatable fuel injector to the drive shaft of the actuator comprised splined or serrated coupling means which allow some axial movement. However, such a splined or serrated connection cannot accommodate even a minute tilt between the two shafts. Therefore, an embodiment of the assembly according to the invention comprises a pin coupling between the shaft 5 of the rotatable fuel injector and the drive shaft. FIG. 4 shows a schematic representation of an actuator with an embodiment of a pin coupling comprising two hubs and pins 14. A pin coupling allows a small axial movement of connected shafts relative to each other, a small tilt angle and/or a small misalignment.

In spite of the fact that the rotating fuel injector assembly according to the present invention comprises measures to prevent or minimize the transfer of axial vibrations from the fuel injector shaft 5 to the drive shaft 2 and the actuator 1, the actuator may still be subjected to vibrations. Depending on the nature of the actuator, e.g. electric motor or hydraulic motor, vibrations may cause increased wear of the actuator to a greater or a lesser extent.

Therefore, the present invention includes measures to minimize the transfer of any type of vibration to the actuator or actuators. In an embodiment, these measures comprise an hydraulic suspension device for the actuator of an assembly according to the invention. In this context, the term suspension may also refer to any type of support system.

This suspension device dampens or smothers the vibrations to which the actuator would normally get exposed. In an embodiment of the hydraulic suspension device, the hydraulic medium of the device comprises fuel of the internal combustion engine in which the assembly is installed. This can either be an open or a closed hydraulic circuit, whereby in this context the term 'open' may mean for example that the fuel passes through the suspension device before it is injected into the combustion chamber.

The fuel in the suspension device will also act as lubrication for the bearings of the actuator. FIG. 5 shows a schematic representation of an embodiment of an hydraulic suspension device for an actuator. In this embodiment the hydraulic suspension device comprises a housing 10 which encapsulates the actuator 1 with only the actuator shaft protruding through respectively the top and bottom wall of the housing. The external diameter of the actuator 1 is smaller than the inner diameter of the housing 10. At the bottom end of its body the actuator 1 comprises a disc la, which disc has an outer diameter which is slightly smaller than the inner diameter of the housing 10, thus allowing the disc la to make small axial movements inside the housing. The annulus 11 between the actuator 1 and the housing 10 will be filled with a liquid which provides the dampening of vibrations. The disc la at the bottom end acts as a resistor for extra vibration dampening in the axial direction.

There is a virtually unlimited number of liquids that may be used as a dampening medium in the annulus 11 of the embodiment of the suspension device shown in FIG. 5. In an embodiment the annulus 11 is filled with a thixotropic fluid which provides effective vibration dampening in all directions. The viscosity can be adapted to the motor vibrations and the motor mass that needs to be dampened.

Of course, vibration dampening for the motor of the assembly according to the invention is not necessarily confined to only the use of a liquid medium, but may also comprise active suspension in combination with dampening through a liquid medium.

Many changes can be made in the method and device described above without departing from the intent and scope thereof. It is intended therefore that the above description and accompanying drawings be interpreted as illustrative and not in a limiting sense.

Claims

An assembly for injecting fuel into the combustion chamber of an internal combustion engine comprising an actuator (1) with a drive shaft (2), coupling means (4) and a rotating fuel injector comprising a shaft (5) to be driven, the drive shaft (2) and the shaft (5) to be driven are substantially in line with each other, characterized in that the coupling means (4) comprise a blocking mechanism which is dependent on the rotational speed and which, above a speed threshold value, automatically rotates for simultaneous rotation of establishes the required connection between the drive shaft (2) and the shaft (5) to be driven.

An assembly according to claim 1, characterized in that the threshold value is selectively adjustable.

An assembly according to claim 1 or 2, characterized in that the coupling means (4) comprise a centrifugal coupling.

Assembly according to one or more of the preceding claims, characterized in that the assembly comprises a second actuator (6) and second coupling means (8), said second coupling means having a direct or indirect connection between the drive shaft (7) required for simultaneous rotation of the second actuator (6) and the shaft (5) to be driven of the rotary atomizer.

An assembly according to claim 4, characterized in that the second actuator (6) comprises a stepper motor.

Assembly according to claim 5, characterized in that the second actuator (6) or the second coupling means (8) comprise a freewheel coupling.

Assembly according to one or more of the preceding claims, characterized in that the assembly comprises a flywheel (3).

An assembly according to claim 7, characterized in that the flywheel (3) comprises a freewheel clutch.

Assembly according to one or more of the preceding claims, characterized in that the assembly comprises means for suspending or supporting one or more actuators in a low-vibration manner.

An assembly according to claim 9, characterized in that the means for low-vibration mounting or supporting the actuators comprise hydraulic means.

An assembly according to claim 9 or 10, characterized in that the hydraulic means for low-vibration suspension or support of the actuators comprise a housing (10) enclosing the actuator and located in the gap (11) between the outside of the actuator and the comprises a vibration-damping medium on the inside of the housing.

An assembly according to claim 11, characterized in that the vibration-damping medium comprises fuel.

An assembly according to claim 11, characterized in that the vibration-damping medium comprises a thixotropic liquid.

Assembly according to one or more of the preceding claims, characterized in that the assembly comprises a pin coupling (13,14).

Assembly according to one or more of the preceding claims, characterized in that the assembly comprises a device (9) for measuring the rotation speed of the shaft (5) of the rotatable atomizer.

An assembly according to claim 15, characterized in that the device (9) for measuring the rotation speed of the shaft (5) of the rotatable atomizer comprises a Hall sensor.