GB2366664A - Control method for a piezoelectric fuel injector - Google Patents
Control method for a piezoelectric fuel injector Download PDFInfo
- Publication number
- GB2366664A GB2366664A GB0022045A GB0022045A GB2366664A GB 2366664 A GB2366664 A GB 2366664A GB 0022045 A GB0022045 A GB 0022045A GB 0022045 A GB0022045 A GB 0022045A GB 2366664 A GB2366664 A GB 2366664A
- Authority
- GB
- United Kingdom
- Prior art keywords
- valve needle
- piezoelectric actuator
- voltage waveform
- priming
- piezoelectric
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000000446 fuel Substances 0.000 title claims abstract description 74
- 238000000034 method Methods 0.000 title claims abstract description 27
- 230000037452 priming Effects 0.000 claims abstract description 53
- 238000002347 injection Methods 0.000 claims abstract description 18
- 239000007924 injection Substances 0.000 claims abstract description 18
- 238000010438 heat treatment Methods 0.000 claims abstract description 11
- 230000000694 effects Effects 0.000 claims abstract description 9
- 230000004323 axial length Effects 0.000 description 15
- 238000006073 displacement reaction Methods 0.000 description 9
- 239000000463 material Substances 0.000 description 9
- 230000003111 delayed effect Effects 0.000 description 4
- 238000002485 combustion reaction Methods 0.000 description 3
- 230000001419 dependent effect Effects 0.000 description 2
- 230000000977 initiatory effect Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 230000009118 appropriate response Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000005553 drilling Methods 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000008542 thermal sensitivity Effects 0.000 description 1
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M47/00—Fuel-injection apparatus operated cyclically with fuel-injection valves actuated by fluid pressure
- F02M47/02—Fuel-injection apparatus operated cyclically with fuel-injection valves actuated by fluid pressure of accumulator-injector type, i.e. having fuel pressure of accumulator tending to open, and fuel pressure in other chamber tending to close, injection valves and having means for periodically releasing that closing pressure
- F02M47/027—Electrically actuated valves draining the chamber to release the closing pressure
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/20—Output circuits, e.g. for controlling currents in command coils
- F02D41/2096—Output circuits, e.g. for controlling currents in command coils for controlling piezoelectric injectors
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M51/00—Fuel-injection apparatus characterised by being operated electrically
- F02M51/06—Injectors peculiar thereto with means directly operating the valve needle
- F02M51/0603—Injectors peculiar thereto with means directly operating the valve needle using piezoelectric or magnetostrictive operating means
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Fuel-Injection Apparatus (AREA)
Abstract
A control method for controlling operation of a piezoelectrically actuated fuel injector comprising a piezoelectric actuator 34 and a valve needle 12 which is engageable with a valve needle seating to control fuel delivery through an outlet opening 13, movement of the valve needle 12 being controlled by controlling the energisation level the piezoelectric actuator, the method comprising the steps of applying a priming voltage across the piezoelectric actuator 34 to induce a thermal heating effect within the piezoelectric actuator 34, and subsequently applying a drive voltage across the piezoelectric actuator 34 to initiate valve needle movement away from the valve needle seating, so as to initiate injection of fuel. The priming voltage takes the form of a variously-shaped pulse train.
Description
2366664 CONTROL METHOD This invention relates to a controlmethod for
controlling operation of a fuel injector for use in the delivery of fuel to a combustion space of an internal combustion engine. In particular, the invention relates to a control method for controlling operation of a fuel injector'of the type intended for use in a fuel system of the accumulator or common rail type, the injector being of the type controlled using a piezoelectric actuator.
In known piezoelectrically actuated fuel injectors, a piezoelectric actuator arrangement is operable to control movement of a valve needle of the injector. The valve needle is slidable within a bore and is engageable with a valve needle seating to control fuel delivery through one or more outlet openings of the injector located downstream of the seating. The piezoelectric actuator arrangement typically comprises a stack of piezoelectric elements, the energisation level, and hence the axial length, of the piezoelectric stack being controlled by controlling a voltage applied across the piezoelectric stack.
In "servo hydraulically-controlled" piezoelectrically actuated injectors, the piezoelectric stack is cooperable with a servo control valve which is moveable to control the pressure of fuel within a control chamber. For example, a typical servo hydraulically controlled fuel injector is described in EP 0 798 459 A. Fuel pressure within the control chamber acts on a surface of the valve needle such that, by controlling fuel pressure within the control chamber, the force urging the valve needle towards its seating due to fuel pressure within the control chamber can be varied, thereby controlling movement of the valve needle towards and away from its seating.
Alternatively, in "direct-control" Piezoelectrically actuated injectors, the piezoelectric actuator arrangement comprises a piezoelectric stack which is coupled directly to the valve needle, through a mechanical or hydraulic load transmitting arrangement, so as to control movement of the valve needle.
The range of engine operating temperatures over which piezoelectrically actuated injectors are required to give stable and consistent performance is, typically, between -40 and + 150 IC. However, due to the thermal sensitivity of piezoelectric materials, the voltage-displacement characteristics of the piezoelectric stack vary with engine operating temperature such that, as the temperature is reduced, the amount by which the stack is displaced as the voltage is varied is also reduced. The stiffness of the piezoelectric stack also varies with temperature such that, for lower engine operating temperature, the stiffness of the piezoelectric stack is increased.
Such variations in the voltage-displacement characteristic can have a detrimental effect on fuel injector performance. By way of example, as the voltage-displacement characteristic of the piezoelectric stack is dependent on engine temperature, opening and closing movement of the valve needle can be delayed following engine start up when the engine is cold. This problem arises in both servo hydraulically-controlled piezoelectrically actuated in ectors and in direct-control piezoelectrically actuated injectors. Furthermore, in direct-control h1jectors, operation under conditions in which fuel pressure is especially high may be prohibited as the voltage-displacement characteristic at relatively low operating temperatures prevents a sufficient actuating force being applied to the piston member and the valve needle to cause the valve needle to lift away from the seating. A further potential problem is that the extent of movement of the valve needle away from the seating at lower operating temperatures can be limited.
In order to overcome the problem of delayed opening and closing movement of the valve needle in servo hydraulically-controlled piezoelectrically actuated injectors, it is known to apply a timing correction factor in software. It is also known to increase the drive voltage across the piezoelectric stack at lower operating temperatures to ensure a sufficient actuation force is applied to the piston member and the valve needle to cause valve needle lift. However, it is undesirable to increase the drive voltage as the increase in electrical field strength increases the stresses applied to the stack. Increasing the drive voltage also has cost implications on the design of the control circuit for the drive voltage.
It is an object of the present invention to provide a control method for controlling operation of a piezoelectrically actuated fuel injector which alleviates or removes at least one of the aforementioned problems.
According to a first aspect of the present invention, there is provided a control method for controlling operation of a piezoelectrically actuated fuel injector comprising a piezoelectric actuator and a valve needle which is engageable with a valve needle seating to control fuel delivery through an outlet opening, movement of the valve needle being controlled by controlling the energisation level of the piezoelectric actuator, the method comprising the steps of applying a priming voltage waveforin across the piezoelectric actuator to induce a thermal heating effect within the piezoelectric actuator, and subsequently applying a drive voltage waveform across the piezoelectric actuator to initiate valve needle movement away from the valve needle seating, so as to initiate injection of fuel.
By applying a priming voltage waveform across the piezoelectric actuator, a thermal heating effect is induced in the piezoelectric actuator. The temperature of the piezoelectric actuator is therefore increased prior to application of the drive voltage waveform, thereby ensuring the piezoelectric actuator has a more desirable voltage-displacement characteristic upon initiation of valve needle movement.
In one embodiment of the invention, the method may be used to control operation of an injector in which the piezoelectric actuator comprises a stack of piezoelectric elements. It will be appreciated, however, that the injector may include a piezoelectric actuator having only a single piezoelectric element.
In particular, in servo hydraulically-controlled piezoelectrically actuated injectors, the method of the present invention provides the advantage that any delay in opening movement of the valve needle, which would otherwise occur at relatively low operating temperatures, such as upon engine start-up, is reduced or avoided.
The method may comprise the step of applying a priming voltage waveform across the piezoelectric actuator, whereby the priming voltage waveform has an opposite polarity to that of the drive voltage waveform. Thus, the application of the priming voltage waveform causes a variation in the axial length of the piezoelectric actuator which opposes the variation in axial length of the piezoelectric actuator which occurs when the drive voltage waveform is applied thereto.
For example, if a positive drive voltage waveform causes an increase in the axial length of the piezoelectric actuator and an increase in the axial length of the piezoelectric actuator causes the valve needle to move in an opening direction away from the valve needle seating, a negative priming voltage may be applied across the piezoelectric stack.
Alternatively, the method may comprise the step of applying a priming voltage waveform across the piezoelectric actuator, whereby the priming voltage waveform causes the axial length of the piezoelectric actuator to be varied in the same direction as when the drive voltage waveform is applied across the piezoelectric actuator. In this embodiment of the invention, it is preferable to ensure the amplitude of the priming voltage waveform is selected so that valve needle movement away from the seating is not initiated during application of the priming voltage waveform, valve needle movement only being initiated upon application of the drive voltage waveform. The amplitude of the priming voltage waveform. must therefore be selected such that it is of sufficient magnitude to induce a self-heating effect within the piezoelectric actuator whilst avoiding unwanted injection.
By way of example, the priming voltage waveforni may have a waveform of sinusoidal, triangular, flat-topped triangular or square form.
The method of the present invention may be applied to a servo hydraulicallycontrolled piezoelectrically actuated fuel injector or may be applied to a direct-control piezoelectrically actuated fuel injector.
According to a further aspect of the present invention, there is provided a fuel injector comprising a valve needle which is engageable with a valve needle seating to control fuel delivery through an outlet opening, a piezoelectric actuator comprising one or more piezoelectric elements, whereby movement of the valve needle is controlled, in use, by controlling the energisation level of the piezoelectric actuator, first voltage supply means arranged to supply a priming voltage waveform across the piezoelectric actuator to induce a thermal heating effect within the piezoelectric actuator, and second voltage supply means arranged to supply a drive voltage across the piezoelectric actuator following application of the priming voltage waveform so as to initiate valve needle movement away from the valve needle seating to initiate injection of fuel.
Preferably, the first and second voltage supply means may be a common voltage source.
The invention will be described, by way of example, with reference to the accompanying drawings, in which; Figure I is a sectional view of a fuel injector which may be operated using the method of the present invention; and Figures 2 to 6 show example waveforms in accordance with different embodiments of the present invention.
The accompanying drawing shows a piezoelectrically actuated fuel injector comprising a nozzle body 10 provided with a blind bore 11 within which a valve needle 12 is reciprocable. The valve needle 12 is engageable with a valve needle seating defined by the blind end of the bore 11 to control fuel delivery from the injector through outlet openings 13 provided in the nozzle body 10. The bore I I is shaped to define an annular chamber 14 to which fuel under high pressure is delivered through a supply passage 15 defined, in part, by drillings provided in various housing parts of the injector. Fuel delivered to the annular chamber 14 is able to flow, via flats, slots or grooves provided on the surface of the valve needle 12 into a delivery chamber 16. When the valve needle 12 is seated against the valve needle seating, the fuel in the delivery chamber 16 is unable to flow out through the outlet openings 13 into the engine cylinder or other combustion space, movement of the valve needle 12 away from the valve needle seating permitting fuel to flow from the delivery chamber 16, past the valve needle seating and out through the outlet openings 13.
The valve needle is provided with one or more thrust surfaces which are exposed to fuel pressure within the delivery chamber 16 such that, when fuel under high pressure is supplied to the delivery chamber 16, the action of fuel applies a force to the thrust surfaces which serves to urge the valve needle 12 away from the valve needle seating. The end of the valve needle 12 remote from the valve needle seating is exposed to fuel pressure within a control chamber 18, a force due to fuel pressure within the control chamber 18 acting on the valve needle 12 so as to urge the needle into engagement with the valve needle seating.
The nozzle body 10 abuts a distance piece 20 provided with a through bore within which a piston member 22 of tubular form is slidable. A screw threaded rod 24 is engaged within a passage defined by the piston member 22. A spring 26 is engaged between the screw threaded rod 24 and the end surface of the valve needle 12, the spring 26 applying a balancing force to the valve needle 12 which serves to urge the valve needle 12 towards its seating so as to avoid unwanted leakage of fuel when fuel under high pressure is not being supplied to the injector (i.e. prior to engine start-up).
The distance piece 20 abuts an end of an actuator housing 28 which is provided with a bore which defines an accumulator chamber 30. The actuator housing 28 is provided with an inlet region, referred to generally as 32, which is arranged to be coupled to a high pressure fuel supply (not shown), for example a common rail charged to an appropriate high pressure by means of a suitable high pressure fuel pump. In use, fuel under high pressure is supplied through the inlet region 32 to the accumulator chamber 30 and from the accumulator chamber 30 into the supply passage 15 for delivery to the annular chamber 14 and the delivery chamber 16.
A piezoelectric actuator arrangement is arranged within the accumulator chamber 30. The actuator arrangement includes a stack of piezoelectric elements 34, the axial length of the piezoelectric stack 34 being controlled, in use, by applying a drive voltage across the stack 34 to vary the energisation level, and hence the axial length, of the stack 34. One end of the piezoelectric stack 34 carries an anvil member 36 which cooperates with a load transmitting member 38, the load transmitting member 38 being in engagement with the piston member 22 and the screw threaded rod 24 such that, upon a variation in the axial length of the piezoelectric stack 34, the anvil member 36 and the load transmitting member 38 cause movement of the piston member 22. By moving the piston member 22, the volume of the control chamber 18 at the uppermost end of the valve needle 12, and hence the pressure of fuel therein, can be varied. It will be appreciated that the fuel pressure within the control chamber 18 assists the force due to the spring 26 in urging the valve needle 12 against the valve needle seating In use, with the injector supplied with fuel under high pressure, and with the piezoelectric stack 34 occupying a first energisation state in which it has a relatively great length, the piston member 22 occupies a position in which the fuel within the control chamber 18 is pressurised to an extent sufficient to ensure that the force applied to the thrust surfaces of the valve needle 12 due to fuel pressure within the delivery chamber 16 is insufficient to overcome the force due to fuel pressure within the control chamber 18 in combination with the force due to the spring 26. The valve needle 12 is therefore held in engagement with the valve needle seating and fuel injection does not take place.
In order to commence injection, the piezoelectric stack 34 is deenergised to a second, lower energisation state by applying a drive voltage waveform. across the stack 34. By driving the piezoelectric stack 34 into the second energisation state, the axial length of the stack 34 is reduced, resulting in upward movement of the lowermost end of the stack 34. Movement of the lowermost end of the stack 34 in an upward direction in the illustration shown in Figure 1 causes the anvil member 36 to move in an upward direction. The anvil member 36 and the load transmitting member 38 are arranged such that a seal is formed between these parts, the movement of the anvil member 36 causing fuel pressure within a volume defined between the components to be reduced such that the load transmitting member 38 is drawn in an upward direction to move with the anvil member 36 and the stack 34. As the piston member 22 is secured to the load transmitting member 38, by driving the piezoelectric stack 34 into the second energisation state, the piston member 22 is caused to move in a direction which increases the volume of the control chamber 18. Fuel pressure within the control chamber 18 is therefore reduced and a point will be reached at which the force due to fuel pressure within the control chamber 18, in combination with the force due to the spring 26, is no longer sufficient to overcome the force acting on the thrust surfaces of the valve needle 12 due to fuel pressure within the delivery chamber 16. In such circumstances, the valve needle 12 is urged away from the valve needle seating to permit fuel delivery through the outlet openings 13 into the enizine cylinder.
Prior to applying the drive voltage waveform across the piezoelectric stack 34 to drive the piezoelectric stack 34 into the second energisation state so as to initiate fuel injection, an alternating preconditioning or priming voltage waveform is applied to the piezoelectric stack 34, thereby causing an increase in the temperature of the stack 34. As the voltage-displacement characteristics of the piezoelectric stack 34 are dependent upon the temperature of the piezoelectric material from which the stack is formed, by heating the stack 34 prior to applying a drive voltage waveform, the voltagedisplacement characteristics can be tailored to provide an appropriate response. For example, upon engine start up under relatively cold conditions, the change in axial length of the stack for a given drive voltage is reduced. Thus, when the drive voltage waveform is applied across the stack 34 to drive the piezoelectric stack into the second energisation state, valve needle movement away from the valve needle seating is slightly delayed. A delay is also incurred when it is required to cease fuel injection and the valve needle is moved towards its seating by driving the piezoelectric stack back into the first energisation state. By applying the priming voltage waveform across the piezoelectric stack 34 prior to application of the drive voltage waveform, the temperature of the stack is increased sufficiently to ensure the voltage-displacement characteristic provides the required displacement for a given drive voltage to ensure valve needle opening and closing movement is not substantially delayed.
The duration and/or frequency of the priming voltage waveform. may be modified depending on the temperature of the surroundings, such that, for example, in particularly cold conditions, it may be preferable to apply the priming voltage across the stack 34 for a longer period of time to ensure the temperature of the piezoelectric material is increased sufficiently prior to application of the drive voltage waveform. In a servo hydraulically controlled piezoelectrically controlled injector of the type shown in Figure 1, it is important to ensure that the priming voltage applied across the stack 34 does not exceed an amount which is sufficient to cause fuel pressure within the control chamber 18 to be reduced to such an extent that the valve needle is caused to move away from the valve needle seating. It may therefore be preferable to apply the priming voltage waveform across the stack in a reverse direction to that required in order to initiate injection. For example,,. if the piezoelectric stack 34 is arranged such that application of a positive drive voltage waveform causes the axial length of the piezoelectric stack to be reduced, thereby giving rise to valve needle movement away from the valve needle seating to initiate injection, the priming voltage waveform applied across the stack may be a negative voltage waveform. The voltage waveform of the priming voltage may take any suitable form. For example, the priming voltage may have a sinusoidal, triangular, flat-topped triangular or square wave form. It will be appreciated, however, that the priming voltage waveform may take an alternative form.
Figure 2 shows an example of the priming and driving voltage waveforms, which may be applied across the stack 34 in a direct control injector (as shown in Figure 1) of the de-energise to inject type, in which the piezoelectric stack is de-energised to initiate valve needle movement away from its seating to commence injection. For a "cold" engine start up (typically a fuel temperature of between -20'C and -40'C), the priming voltage waveform 40 is applied for a duration (Q of, typically, between 5 and 30 s, although the preferred duration will also depend upon the ambient temperature. Typically, the priming voltage waveform 40 has a frequency of approximately 10 kHz. The peak to peak voltage, AVP, of the priming voltage waveform is approximately 15 percent of the peak to peak voltage, AVd, of the drive voltage waveform. The priming voltage is removed from the stack and the drive voltage across the stack is switched to its lower state over a period of approximately 200 ts. In practice, the permissible relative amplitudes of the drive voltage and the priming voltage will depend upon the control hydraulics and the mechanical losses in the actuator assembly.
For a servo-controlled piezoelectrically actuated injector, the peak to peak voltage, AVP. of the priming voltage waveform may be of larger magnitude relative to the peak to peak voltage, AVd, of the drive voltage waveform, for example AVP may be approximately 75 % of AVd, depending on the control hydraulics and mechanical losses within the actuator assembly.
As an alternative waveform to that shown in Figure 2, the priming voltage waveform may have a lower frequency (typically 5 kHz) but a larger peak to peak voltage, AVP, as shown in Figure 3.
Figure 4 shows an example waveform which may be applied across a piezoelectric stack in an energise to inject injector, in which energisation of the piezoelectric stack causes vale needle movement away from its seating to commence injection. In this embodiment of the invention, the priming voltage waveform is applied in a forward field direction, the priming voltage and the drive voltage both having positive values.
An alternative waveform which may be applied to an injector of the energise to inject type is shown in Figure 5 in which the voltage, AVP,, is the difference in voltage between the lower voltage level of the drive voltage waveform and the lower voltage level of the priming voltage waveform. Typically, AVP is selected so that the lower voltage level (a negative voltage level) is greater than the voltage corresponding to the reverse coercive field strength for the particular piezoelectric material from which the stack is formed, so as to avoid the risk of depolarisation. In this embodiment of the invention, the drive voltage is positive and the priming voltage is applied in both forward and reverse field directions. It will be appreciated that it would also be possible to control operation of an injector by applying the priming voltage in both forward and reverse field directions with a negative drive voltage.
For any injector, the preferred priming voltage waveform will depend on several factors. For example, the characteristics of the piezoelectric material, such as the hysteresis characteristics and the electrical efficiency, the shape of the piezoelectric actuator and the capacitance of the actuator will all influence the voltage-displacement characteristics. Generally, however, the application of a relatively high frequency priming voltage waveform and a relative large peak to peak voltage will encourage a greater degree of self-heating of the piezoelectric material. It is important, however, to ensure that priming voltage waveform does not have a frequency which corresponds to the natural frequency of vibration of the piezoelectric material, or higher harmonics of the natural frequency, as this can lead to destruction of the piezoelectric material.
It will be appreciated that the method of the present invention is not limited to use in a piezoelectrically actuated fuel injector in which valve needle movement is controlled by means of a piston member, operable in response to changes in the axial length of the piezoelectric stack, to control fuel pressure within a control chamber acting on a surface of the valve needle. The method of the present invention may also be used in a direct-control piezoelectrically actuated fuel injector in which the piezoelectric stack is coupled directly to the valve needle, through a mechanical load transmitting arrangement, such that a reduction in the axial length of the stack is directly transmitted to the valve needle to cause the valve needle to move away from the valve needle seating. The method of the present invention may also be used in a servo-controlled injector in which the piezoelectric actuator is coupled directly or indirectly via a mechanical or hydraulic motion amplifier to a control valve to control fuel pressure within a control chamber, fuel pressure within the control chamber being varied, in use, so as to control movement of the injector valve needle.
It will further be appreciated that, depending on the configuration of the piezoelectric stack 34 and the piezoelectric material from which the stack 34 is formed, either de-energisation or energisation of the stack 34 into the second energisation state may cause a reduction in the axial length of the stack and, hence, initiation of fuel injection. Additionally, it will be appreciated that the priming and drive voltages may originate from separate voltage sources, or may be applied by means of a common voltage source.
Claims (12)
1. A control method for controlling operation of a piezoelectrically actuated fuel injector comprising a piezoelectric actuator and a valve needle which is engageable with a valve needle seating to control fuel delivery through an outlet opening, movement of the valve needle being controlled by controlling the energisation level of the piezoelectric actuator, the method comprising the steps of applying a priming voltage waveform across the piezoelectric actuator to induce a thermal heating effect within the piezoelectric actuator, and subsequently applying a drive voltage waveform across the piezoelectric actuator to initiate valve needle movement away from the valve needle seating, so as to initiate injection of fuel.
2. The control method as claimed in Claim 1, comprising the step of applying a priming voltage waveforin across the piezoelectric actuator which has an opposite polarity to that of the drive voltage waveform which is applied to initiate injection.
3. The control method as claimed in Claim 2, comprising the step of applying a negative priming voltage waveform across the piezoelectric actuator to induce a thermal heating effect within the piezoelectric actuator and subsequently applying a positive drive voltage waveform across the piezoelectric stack so as to initiate injection.
4. The control method as claimed in Claim 1, comprising the step of applying a priming voltage waveform across the piezoelectric actuator which is of the same polarity as the drive voltage waveform which is applied to initiate injection.
5. The control method as claimed in Claim 1, comprising the step of applying a priming voltage in both a forward and a reverse field direction to induce a thermal heating effect within the piezoelectric actuator.
6. The control method as claimed in Claim 4 or Claim 5, whereby the amplitude of the priming voltage waveform is selected to ensure valve needle movement away from the seating is not initiated during application of the priming voltage waveform.
7. The control method as claimed in any of Claims 1 to 6, wherein the priming voltage waveform is of sinusoidal, triangular, flat-topped triangular or square form.
8. The control method as claimed in any of Claims 1 to 7, wherein the piezoelectric actuator comprises a stack of piezoelectric elements.
9. A fuel injector comprising a valve needle which is engageable with a valve needle seating to control fuel delivery through an outlet opening, a piezoelectric actuator comprising one or more piezoelectric elements, whereby movement of the valve needle is controlled, in use, by controlling the energisation level of the piezoelectric actuator, first voltage supply means arranged to supply a priming voltage waveform across the piezoelectric actuator to induce a thermal heating effect within the piezoelectric actuator, and second voltage supply means arranged to supply a drive voltage waveform across the piezoelectric actuator following application of the priming voltage waveform. so as to initiate valve needle movement away from the valve needle seating to initiate injection of fuel.
10. The fuel injector as claimed in Claim 9, wherein the first and second voltage supply means take the form of a common voltage source.
11. A method of operating a piezoelectrically actuated fuel injector substantially as herein described with reference to the accompanying drawing.
12. A fuel injector substantially as herein described with reference to the accompanying drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0022045A GB2366664B (en) | 2000-09-08 | 2000-09-08 | Control method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0022045A GB2366664B (en) | 2000-09-08 | 2000-09-08 | Control method |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB0022045D0 GB0022045D0 (en) | 2000-10-25 |
| GB2366664A true GB2366664A (en) | 2002-03-13 |
| GB2366664B GB2366664B (en) | 2004-03-24 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0022045A Expired - Fee Related GB2366664B (en) | 2000-09-08 | 2000-09-08 | Control method |
Country Status (1)
| Country | Link |
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| GB (1) | GB2366664B (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102004053349A1 (en) * | 2004-11-04 | 2006-05-18 | Siemens Ag | Fuel injector controlling method for internal combustion engine, involves actuating fuel injection by supplying control pulse to actuator, and supplying conditioning pulse to actuator before fuel injection, during injecting interval |
| US7258109B2 (en) | 2004-07-31 | 2007-08-21 | Robert Bosch Gmbh | Method for operating a fuel injection device, especially for a motor vehicle |
| WO2008071507A1 (en) * | 2006-12-12 | 2008-06-19 | Robert Bosch Gmbh | Method for operating an injection valve |
| EP1956221A1 (en) * | 2007-02-02 | 2008-08-13 | Delphi Technologies, Inc. | A method of operating a piezoelectric actuator |
| EP2083158A1 (en) * | 2008-01-22 | 2009-07-29 | Delphi Technologies, Inc. | Piezoelectrically actuated fuel injector and operating method thereof |
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| EP0509488A1 (en) * | 1991-04-15 | 1992-10-21 | Nec Corporation | Method for protecting the piezoelectric element of a piezoelectric actuator against moisture |
| GB2334164A (en) * | 1998-02-10 | 1999-08-11 | Bosch Gmbh Robert | A drift-compensated piezoelectric fuel injector actuator |
| WO1999066194A1 (en) * | 1998-06-12 | 1999-12-23 | Robert Bosch Gmbh | Liquid control valve |
| EP1044326A1 (en) * | 1998-10-23 | 2000-10-18 | DaimlerChrysler AG | Device and constant control of piezoelectric actuators for fuel injection systems |
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2000
- 2000-09-08 GB GB0022045A patent/GB2366664B/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0509488A1 (en) * | 1991-04-15 | 1992-10-21 | Nec Corporation | Method for protecting the piezoelectric element of a piezoelectric actuator against moisture |
| GB2334164A (en) * | 1998-02-10 | 1999-08-11 | Bosch Gmbh Robert | A drift-compensated piezoelectric fuel injector actuator |
| WO1999066194A1 (en) * | 1998-06-12 | 1999-12-23 | Robert Bosch Gmbh | Liquid control valve |
| EP1044326A1 (en) * | 1998-10-23 | 2000-10-18 | DaimlerChrysler AG | Device and constant control of piezoelectric actuators for fuel injection systems |
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7258109B2 (en) | 2004-07-31 | 2007-08-21 | Robert Bosch Gmbh | Method for operating a fuel injection device, especially for a motor vehicle |
| DE102004037255B4 (en) * | 2004-07-31 | 2016-06-09 | Robert Bosch Gmbh | Method for operating a fuel injection device, in particular for a motor vehicle |
| DE102004053349A1 (en) * | 2004-11-04 | 2006-05-18 | Siemens Ag | Fuel injector controlling method for internal combustion engine, involves actuating fuel injection by supplying control pulse to actuator, and supplying conditioning pulse to actuator before fuel injection, during injecting interval |
| WO2008071507A1 (en) * | 2006-12-12 | 2008-06-19 | Robert Bosch Gmbh | Method for operating an injection valve |
| US8082903B2 (en) | 2006-12-12 | 2011-12-27 | Robert Bosch Gmbh | Method for operating an injector |
| CN101558228B (en) * | 2006-12-12 | 2013-07-10 | 罗伯特.博世有限公司 | Method for operating an injection valve |
| EP1956221A1 (en) * | 2007-02-02 | 2008-08-13 | Delphi Technologies, Inc. | A method of operating a piezoelectric actuator |
| US7576473B2 (en) | 2007-02-02 | 2009-08-18 | Delphi Technologies, Inc. | Method of operating a piezoelectric actuator |
| EP2083158A1 (en) * | 2008-01-22 | 2009-07-29 | Delphi Technologies, Inc. | Piezoelectrically actuated fuel injector and operating method thereof |
| JP2009174534A (en) * | 2008-01-22 | 2009-08-06 | Delphi Technologies Inc | Fuel injector and operating method thereof |
| US8544764B2 (en) | 2008-01-22 | 2013-10-01 | Delphi Technologies Holding S.Arl | Fuel injector and operating method therefor |
Also Published As
| Publication number | Publication date |
|---|---|
| GB0022045D0 (en) | 2000-10-25 |
| GB2366664B (en) | 2004-03-24 |
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| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) |
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