GB2303403A - Fuel injector with piezo-electric element to vary the size or shape of the ou t passage - Google Patents
Fuel injector with piezo-electric element to vary the size or shape of the ou t passage Download PDFInfo
- Publication number
- GB2303403A GB2303403A GB9514306A GB9514306A GB2303403A GB 2303403 A GB2303403 A GB 2303403A GB 9514306 A GB9514306 A GB 9514306A GB 9514306 A GB9514306 A GB 9514306A GB 2303403 A GB2303403 A GB 2303403A
- Authority
- GB
- United Kingdom
- Prior art keywords
- piezo
- fuel
- nozzle
- fuel injector
- injection
- 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.)
- Withdrawn
Links
- 239000000446 fuel Substances 0.000 title claims description 50
- 238000002347 injection Methods 0.000 claims description 40
- 239000007924 injection Substances 0.000 claims description 40
- 238000002485 combustion reaction Methods 0.000 claims description 9
- 239000012530 fluid Substances 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 239000007921 spray Substances 0.000 description 4
- 239000002033 PVDF binder Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000002305 electric material Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 238000011144 upstream manufacturing Methods 0.000 description 2
- 230000003321 amplification Effects 0.000 description 1
- 238000000889 atomisation Methods 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 238000004939 coking Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 239000011796 hollow space material Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- VIKNJXKGJWUCNN-XGXHKTLJSA-N norethisterone Chemical compound O=C1CC[C@@H]2[C@H]3CC[C@](C)([C@](CC4)(O)C#C)[C@@H]4[C@@H]3CCC2=C1 VIKNJXKGJWUCNN-XGXHKTLJSA-N 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
Classifications
-
- 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
- F02M61/00—Fuel-injectors not provided for in groups F02M39/00 - F02M57/00 or F02M67/00
- F02M61/16—Details not provided for in, or of interest apart from, the apparatus of groups F02M61/02 - F02M61/14
- F02M61/18—Injection nozzles, e.g. having valve seats; Details of valve member seated ends, not otherwise provided for
- F02M61/1886—Details of valve seats not covered by groups F02M61/1866 - F02M61/188
-
- 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
- F02M2200/00—Details of fuel-injection apparatus, not otherwise provided for
- F02M2200/21—Fuel-injection apparatus with piezoelectric or magnetostrictive elements
Description
FUEL INJECTORS
The present invention relates to fuel injectors, particularly for use in internal combustion engines, and to fuel injection nozzles forming part of fuel injectors and is concerned with varying the cross-sectional area of the orifice through which the fuel is discharged.
In fuel injectors currently used in internal combustion engines the fuel is typically injected into a port or chamber of the engine through one or more fixed geometry holes in the fuel injection nozzle. The required turndown ratio, that is the ratio of maximum to minimum fuel flow rate, of certain fuel injectors, such as those used in heavy duty diesel engines, is considerable and may be typically 40:1. The area of the fixed geometry holes is therefore a compromise that must give acceptable fuel spray characteristics over the entire engine speed and load range but remain within the mechanical limitations of the system.
The hole or orifice size and the fuel injection pressure have a direct effect on the fuel spray characteristics, such as droplet size, velocity, momentum, evaporation rate, penetration into the combustion chamber and injection duration and consequently also have a direct effect on the combustion efficiency and subsequent exhaust emissions and fuel consumption. It is therefore apparent that for optimum combustion efficiency and minimised exhaust emissions the orifice size should preferably be varied across the engine speed and load operation range in order to control the spray characteristics. Typically an orifice cross-sectional area change of 20-50t would be useful and could allow the combustion system to be better optimised.
A known solution to this problem is to mechanically vary the nozzle orifice geometry, and JP-A-57-068555 (Diesel
Kiki) discloses a fuel injection nozzle for direct injection type diesel engines, in which the area of the nozzle hole is changed in dependence on the injection quantity and thereby restricts the fuel flow at low flow rates. This known fuel injection nozzle is illustrated in Figures 1 and 2 of the accompanying drawings, in which
Figure 1 is a longitudinal sectional view of the nozzle and Figure 2 is a similar view on an enlarged scale of the downstream end of the nozzle. The nozzle includes a hollow body 1 which accommodates a valve needle 4 at whose lower end is a pin shaft 10 which is a sliding sealed fit in a hollow protuberance which is formed at the bottom of the nozzle body and in which two nozzle holes 12 are formed.The interior of the pin shaft 10 is provided with a longitudinal hollow space 14 which communicates with the peripheral surface of the pin shaft through two upper ports 16 and two lower control holes 18. The valve needle is movable longitudinally and cooperates with the interior of the nozzle body to control the flow of fuel through a dispensing passage comprising the lower portion of the interior of the nozzle body, the ports 16, the longitudinal space 14, the holes 18 and the nozzle holes 12. As the needle is moved longitudinally, the degree of overlap of the holes 12 and 18 is varied which means that the effective nozzle orifice area is varied also.
Such a system is inherently complex and relatively expensive to manufacture, and lacks sufficient flexibility and response characteristics necessary to respond fully to demands for significant fuelling changes. It is limited by the mechanical nature of its operation.
The object of the present invention is to provide a fuel injection nozzle with variable orifice geometry that is mechanically simple and inherently cheaper to manufacture and easier to calibrate than current fuel injection nozzles, and achieves increased flexibility in terms of cross-sectional area changes and provides a faster response to demands for fuelling changes.
According to the present invention a fuel injector includes a nozzle body which defines an internal space accommodating a valve needle, one or more injection holes being formed in the nozzle body and the valve needle being movable longitudinally to vary the flow of fuel through an outlet passage which includes the or each injection hole, characterised by one or more piezoelectric elements which at least partially define the outlet passage and which may be acted on by an electric potential to vary the area and/or the shape of the outlet passage.
If there is only a single injection hole, there may be two or more piezo-electric elements which partially define or extend wholly around the outlet passage but in the simplest embodiment there is a single piezo-electric element with a single hole in it which wholly defines a portion of the length of the outlet passage or even two or more such piezo-electric elements. If there are two or more injection holes one or more or all of them may be associated with one or more respective piezo-electric elements or a single such element may be arranged to vary the flow characteristics through more than one injection hole simultaneously.
A fuel injector may consist substantially only of a fuel injection nozzle or it may also include a number of other components and the present invention thus also embraces a fuel injection nozzle constructed as described above.
The invention also embraces an internal combustion engine of either spark-ignition or compression-ignition type employing direct in-cylinder injection or indirect injection into or either a prechamber or an inlet port including at least one fuel injector as described above.
In practice, the or each piezo-electric element will be connected to electrical leads which are in turn connected to electronic control means arranged to supply appropriate electric potentials to them to vary the cross-sectional area or shape of the outlet passage. The voltage applied to the or each piezo-electric element can be supplied by existing conventional engine management systems thereby allowing an instantaneous response to changes in the engine load and speed.
It is known that for the flow of fluid through an orifice or nozzle, there is a direct relationship between the cross-sectional area, the pressure drop and flow rate.
By varying the cross-sectional area, the flow rate and/or the pressure drop can be regulated. It is known that by applying an electrical potential difference across a piezo-electric material, such as ceramic, quartz or a polymer such as polyvinylidene fluoride (PVDF), the material dimensions can be altered in response to the potential difference. Thus the application of an electric potential across the or each piezo-electric element causes the material to respond to vary the size of the associated hole and thereby alter the crosssectional area of the nozzle orifice and thereby the fuel flow rate and/or fuel pressure drop.
For quartz, a change in the applied potential difference of 100V will typically result in a dimensional change of lHm. Higher sensitivities are exhibited by piezo-ceramic materials, with typical dimensional changes of 100pm for the same applied potential difference. Because a wider range of movement or a lower applied voltage may be desirable, some means of electrical or mechanical amplification may be incorporated. This may be achieved, for example, by using a number of elements in series.
Piezo-electric elements have response times in the order of a few micro (y) seconds. This fast response provides a significant advantage over most mechanically operated devices. The response time for a variable area orifice is thus fast enough to follow the response times of the engine. The orifice area needs to be controlled only for the injection period, or a portion of the injection period, and not necessarily for the entire engine cycle.
Typically injection periods vary in the range 1-3 milli(m) seconds. Also, the fuelling rate must be capable of a typical increase from 0-50% within one engine cycle at a given speed. For example, at 2,000 revolutions per minute engine speed, a 50% change in fuelling must be achieved in 60 ms. These response times are well within the capability of piezo-electric materials.
For conventional cam-driven fuel injection equipment, the fuel pressure that can be obtained at the injector orifice is directly related to the orifice area, cam rate and engine speed. This characteristic is not desirable and alternative systems have been developed to decouple the fuel pressure from engine speed, e.g. common rail systems. The present invention overcomes the limitations of cam-driven fuel injection equipment in that the orifice area can be continuously varied to maintain a constant pressure, if required, regardless of engine speed. Additionally, for cam-driven injection systems, it is possible according to the present invention to size the nozzle orifice so that it is sufficiently large to limit the maximum injection pressure at the highest speed/fuelling condition according to the mechanical constraints of the engine and fuel injection system.
Before the start of injection the orifice area can be reduced to give a higher pressure and better atomisation of the fuel at the start of injection.
In practice the piezo-electric element(s) could be inserted into redesigned nozzle tips of essentially conventional type, with the hole diameters cut to nominal size. At that stage, it would not be necessary to achieve the very high dimensional precision associated with conventional fuel injector nozzles. During manufacture, each nozzle could be calibrated using a suitable calibration fluid and the actual nozzle flow rate monitored on a rig. The electronic engine management system would be programmed to ensure a consistent performance across the complete set of fuel injector nozzles by individually matching the applied voltage to the or each piezo-electric element.This would enable cheaper and faster manufacture of the nozzles and could limit the number of different types of nozzle required for a range of engine applications by varying either or both the holes in the piezo-electric element and the nozzle cone angle only. Also, by monitoring the injection pressure and/or injection period, the nozzle area may be varied over the life of the engine to compensate for any nozzle coking or wear.
Further features and details of the invention will be apparent from the following description of one specific embodiment of a variable geometry fuel injection nozzle in accordance with the invention which is given with reference to Figure 3 of the accompanying diagrammatic illustration, which is a sectional view through the tip of a fuel injection nozzle according to the present invention.
Figure 3 shows the tip of a fuel injection nozzle which, in use, would be connected to a fuel injection pump, needle valve operating means and electronic control means (not shown) and mounted in one cylinder for direct injection applications, or in one prechamber or one inlet port of a common manifold for indirect injection applications, of an internal combustion engine of either spark-ignition or compression-ignition type, employing gasoline, diesel or a combustible gas as a fuel. The nozzle body 1 is of essentially conventional type, differing in that it is specifically designed to accommodate a piezo-electric element or elements 2 in which a respective circular hole 3 is formed therethrough. A conventional valve needle 4 serves to control the admission of fuel through the orifice 3.
Electronic control means are connected electrically to the piezo-electric element 2 via electrical leads 5 and 6. The nozzle hole 7 in the nozzle body 1 is in alignment with the hole 3 and its diameter, at least at its upstream end is the same as that of the hole 3. In this case the hole 7 is outwardly flared, i.e. of conical shape and the degree of conicity may be selected according to the specific application. When a potential difference is applied to the leads 5,6, the piezoelectric element 2 changes its shape thereby reducing the diameter of the hole 3.
The piezo-electric element 2 is of disc shape and may comprise a single element or a plurality of superposed elements and in this event the individual elements may be connected in series or parallel. Alternatively, there may be two more piezo-electric elements distributed around the passage or space immediately upstream of the nozzle hole 7 which may have a voltage applied to them simultaneously or at different times.
The precise number and position of the piezo-electric elements is not limited and the present invention contemplates any fuel injector or injection nozzle whose fuel spray characteristics may be modified by one or more piezo-electric elements. Indeed, the present invention is applicable also to any fluid flow device in which control of the fluid flow rate and/or pressure is required.
Claims (4)
1. A fuel injector including a nozzle body, which defines an internal space accommodating a valve needle, one or more injection holes being formed in the nozzle body and the valve needle being movable longitudinally to vary the flow of fuel through an outlet passage which includes the or each injection hole, characterised by one or more piezo-electric elements which at least partially define the outlet passage and which may be acted on by an electric potential to vary the area and/or the shape of the outlet passage.
2. A fuel injector as claimed in Claim 1 including two or more piezo-electric elements which partially define or extend wholly around the outlet passage.
3. A fuel injector as claimed in Claim 1 in which there is a single piezo-electric element with a single hole in it which wholly defines a portion of the length of the outlet passage.
4. An internal combustion engine of spark-ignition or compression-ignition type including at least one fuel injector as claimed in any one of the preceding claims.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9514306A GB2303403A (en) | 1995-07-13 | 1995-07-13 | Fuel injector with piezo-electric element to vary the size or shape of the ou t passage |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9514306A GB2303403A (en) | 1995-07-13 | 1995-07-13 | Fuel injector with piezo-electric element to vary the size or shape of the ou t passage |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9514306D0 GB9514306D0 (en) | 1995-09-13 |
| GB2303403A true GB2303403A (en) | 1997-02-19 |
Family
ID=10777576
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9514306A Withdrawn GB2303403A (en) | 1995-07-13 | 1995-07-13 | Fuel injector with piezo-electric element to vary the size or shape of the ou t passage |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2303403A (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4101076A (en) * | 1975-04-03 | 1978-07-18 | Teledyne Industries, Inc. | Piezoelectric fuel injector valve |
| US4750706A (en) * | 1985-09-24 | 1988-06-14 | Robert Bosch Gmbh | Valve for dosing liquids or gases |
-
1995
- 1995-07-13 GB GB9514306A patent/GB2303403A/en not_active Withdrawn
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4101076A (en) * | 1975-04-03 | 1978-07-18 | Teledyne Industries, Inc. | Piezoelectric fuel injector valve |
| US4750706A (en) * | 1985-09-24 | 1988-06-14 | Robert Bosch Gmbh | Valve for dosing liquids or gases |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9514306D0 (en) | 1995-09-13 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |