Fuel injector

Abstract

A fuel injector comprising: a fluid inlet 202 at a first, upstream, longitudinal end; a fluid outlet 212 at a second, downstream, longitudinal end; a ball valve 220 biased by a resilient element 206 d

Description

TECHNICAL FIELD The present disclosure relates to a fuel injector. In particular, the disclosure relates to a “top in bottom out” fuel injector comprising a housing having a fluid inlet at a first, upstream, longitudinal end of the housing and a fluid outlet at a second, downstream, longitudinal end of the housing. A fuel injection system is also disclosed. BACKGROUND Greenhouse gas emissions from internal combustion engines (ICEs) contribute to anthropogenic climate change. To reduce greenhouse gas emissions related to ICEs, fossil fuels will likely be replaced by alternative fuels. Such alternative fuels may include biomethane, hydrogen, and ammonia. However, these alternative fuels are more complicated to use than fossil fuels. In particular, in the prior art, gas injectors have been provided for port injection. However, there are numerous problems with only using port injection, including backfire risk and limited controllability. Injectors capable of carrying more complicated alternative fuels such as biomethane, hydrogen and ammonia are required as an enabler to allow a move to low carbon fuelled ICEs. Such ICEs are expected to take a significant proportion of the diesel, gasoline and natural gas ICE market and will be applicable to automotive, marine, construction, off-highway, mining and generator markets. However, during the transition to alternative fuels, there is also still a need for improved injectors for diesel and gasoline ICEs. Top in bottom out injectors in which a fluid flows into the injector at a first end, and exits the injector at a second end opposite the first end, are favoured in both ICEs and in engines using alternative fuels. However, they require close fitting sliding surfaces which increase manufacturing complexity and costs. The inventors have appreciated the need for a “top in bottom out” fuel injector which may be produced more easily and with less close fitting sliding surfaces. SUMMARY OF THE DISCLOSURE The present disclosure provides a fuel injector and a fuel injection system, as defined in the appended claims, to which reference should now be made. According to a first aspect of the present disclosure, there is provided a fuel injector comprising a housing. The housing comprises: a fluid inlet at a first, upstream, longitudinal end of the housing; a fluid outlet at a second, downstream, longitudinal end of the housing; a valve opening disposed between the fluid inlet and the fluid outlet; and a valve seat surrounding the valve opening. The injector further comprises: a ball valve element disposed within the housing; a resilient element arranged to bias the ball valve element towards the valve seat to close the valve opening; and a plunger configured to displace the ball valve element. The fuel injector is configurable between a closed configuration, in which the ball valve element is held in the valve seat by the resilient element, and an open configuration, in which the plunger displaces the ball valve element away from the valve seat to permit fluid flow from the fluid inlet to the fluid outlet along a flow path comprising a flow path section extending along a longitudinal axis of the housing. By providing a spring and ball valve element, and a plunger configured to push the ball valve element off a valve seat upon actuation, and by providing a flow path extending along a longitudinal axis of the fuel injector, the fuel injector of the present disclosure may allow for a “top in bottom out” type injector to be provided without requiring close fitting sliding surfaces. Thus, the fuel injector of the present disclosure may be produced with reduced complexity and costs, as greater tolerances are acceptable. As used herein, the term “longitudinal axis” relates to a central axis from one longitudinal end of a body to the other longitudinal end. In other words, the longitudinal axis is the axis of a body from one end to the other end of the body which includes a central point of the body. For example, the longitudinal axis of the housing is a central axis from the upstream end of the housing to the downstream end of the housing. Optionally, the resilient element is a spring. Advantageously, springs are inexpensive and are readily available with a variety of properties. Alternatively, the resilient element may be a resilient material, such as rubber. For example, the resilient element may be a tube of rubber. Optionally, the flow path section may extend within the plunger. Advantageously, this may allow for flow to be channelled through a central portion, i.e. along a longitudinal axis, of the housing / fuel injector. Optionally, the plunger and the housing are arranged coaxially. In other words, a longitudinal axis of the plunger may be substantially aligned with a longitudinal axis of the housing. Such an arrangement may allow for the plunger to easily move within the housing, and for the flow path section to extend within the plunger, and along a longitudinal axis of the housing. The plunger may comprise a fluid flow channel, the flow path section extending at least through the fluid flow channel. This may allow for fluid flow through the plunger and along a central longitudinal axis of the injector / housing. Indeed, it may also allow for the injector to be lighter. Further optionally, the fluid flow channel of the plunger terminates at a downstream opening. Advantageously, this may allow for flow to easily exit the plunger. It may also facilitate manufacturing of the hollow plunger. The plunger may comprise at least one upstream opening to permit fluid flow between a, or the, fluid flow channel of the plunger and the valve opening. Advantageously, such an upstream opening may allow fluid to easily flow between the fluid inlet and the fluid outlet via the interior of the plunger when the injector is in the open configuration. Optionally the plunger may comprise two or more upstream openings. Advantageously, providing two or more upstream openings may allow for increased fluid flow. Further optionally, the two or more upstream openings are arranged annularly around the longitudinal axis of the plunger. Advantageously, annularly arranged upstream openings may allow for an even fluid flow. Yet further optionally, the two or more upstream openings are annularly spaced substantially evenly about a circumference of the plunger. Advantageously, evenly spacing the annular upstream openings may further improve uniformity of fluid flow. Optionally, an upstream end of the plunger is configured to directly displace the ball valve element. Advantageously, directly displacing the ball valve may allow for improved control over reconfiguration between open and closed configuration. Optionally, the plunger comprises an integral drive pin aligned with the valve opening. Alternatively, an upstream end of the plunger is configured to indirectly displace the ball valve element. For example, a further element coupled to the upstream end of the plunger may act to displace the ball valve element, or a further element may be provided which the upstream end of the plunger engages to displace the ball valve element. Optionally, a drive pin is coupled to the plunger and aligned with the valve opening. Alternatively, the plunger is configured to act on a drive pin, the drive pin being aligned with the valve opening. Optionally, the drive pin may be solid. Advantageously, a solid drive pin may prevent any backflow of fluid from the hollow plunger into the drive pin. It may also improve reliability. Optionally, in the open configuration, at least a portion of the drive pin extends through the valve opening to push the ball valve element away from the valve seat. Advantageously, this may allow for the ball valve element to be reliably and repeatedly displaced away from the valve seat. Indeed, it may also allow for large manufacturing tolerances. Optionally, the fuel injector further comprising a guide arranged to surround an upstream portion of the plunger, or the drive pin. The guide is for aligning the drive pin, or upstream portion of the plunger, with the valve opening, so that the drive pin or upstream portion of the plunger may reliably extend through the valve opening to push the ball valve element away from the valve seat. Optionally, the guide comprises at least one guide opening for permitting fluid to flow through the guide. Further optionally, the or each guide opening is configured to permit fluid flow through the guide along an axis that is parallel to the longitudinal axis. Advantageously, this may allow for improved and more uniform fluid flow. Optionally, the resilient element, ball valve element, valve seat, and valve opening are arranged adjacent the fluid inlet. Advantageously, this may allow for fluid to be intermittently allowed to flow into the injector at the upstream end. The fuel injector may comprise a passive valve for preventing upstream fluid flow from the fluid outlet towards the fluid inlet. Advantageously, the passive valve may prevent any upstream flow through the housing. For example, any build-up of pressure during the combustion phase is prevented from affecting the injector. Thus, the injector may directly inject into a cylinder, but still be protected from any combustion pressures. The passive valve may be a pressure-operated control valve. Such a pressure-operated control valve may prevent upstream fluid flow while allowing downstream fluid flow if a downstream fluid pressure exceeds a pressure threshold. Optionally, the passive valve may be a passive ball valve. Further optionally, the passive ball valve comprises a second resilient element, a second ball valve element, and a second valve seat, wherein the second resilient element is arranged to bias the second ball valve element towards the second valve seat to close the second valve opening. Thus, the nonreturn valve is normally closed. Advantageously, such a passive ball valve may allow for relatively large manufacturing tolerances. Further, a passive ball valve is reliable and therefore may require less maintenance. The passive valve may be a non-return valve. The second resilient element may be configured so that a biasing force exerted by the second resilient element on the second ball valve element is such that fluid flow from the fluid inlet to the fluid outlet pushes the second ball valve element off the second valve seat, thus opening the second valve opening. Optionally, the second resilient element may be a spring. The passive valve may be arranged adjacent the fluid outlet. Advantageously, this arrangement may prevent combustion pressures from affecting any portion of the injector. Optionally, the fluid inlet comprises at least one inlet opening in the first, upstream, longitudinal end of the housing. This may allow fluid flow into a upstream longitudinal end surface of the housing. Further optionally, the fluid inlet comprises a plurality of inlet openings in the first, upstream, longitudinal end of the housing. Advantageously, a plurality of inlet openings may allow for increased fluid flow. Optionally, the plurality of inlet openings is arranged in the first, upstream, longitudinal end of the housing annularly around the longitudinal axis of the housing. Advantageously, such an arrangement may allow for more even fluid flow. Optionally, the plurality of inlet openings is annularly spaced in the first, upstream, longitudinal end of the housing, substantially evenly around the longitudinal axis of the housing. Advantageously, this may allow for uniform fluid flow. The or each inlet opening may be configured to permit fluid flow through the first, upstream, longitudinal end of the housing along an axis that is parallel to the longitudinal axis. This may allow for controlled flow of fluid into the injector housing. Optionally, the fluid outlet comprises at least one outlet opening in the second, downstream, longitudinal end of the housing. This may allow fluid flow out of a downstream longitudinal end surface of the housing. Further optionally, the fluid outlet comprises a plurality of outlet openings in the second, downstream, longitudinal end of the housing. Advantageously, a plurality of outlet openings may allow for increased fluid flow out of the injector. Optionally, the plurality of outlet openings is arranged in the second, downstream, longitudinal end of the housing annularly around the longitudinal axis of the housing. Advantageously, such an arrangement may allow for more even fluid flow. Optionally, the plurality of outlet openings is annularly spaced in the second, downstream, longitudinal end of the housing, substantially evenly around the longitudinal axis of the housing. Advantageously, this may allow for uniform fluid flow. The or each outlet opening may be configured to permit fluid flow through the second, downstream, longitudinal end of the housing along an axis that is parallel to the longitudinal axis. This may allow for controlled flow of fluid out of the injector housing. Optionally, the fuel injector further comprises: a coil; a first magnetic element arranged to surround at least a portion of the plunger; and a second magnetic element forming at least part of the plunger, such that energisation of the coil energises the first magnetic element and causes the plunger to move, actuating the fuel injector from the closed configuration to the open configuration. Advantageously, such an arrangement allows for displacement of the plunger to be controlled reliably and precisely. Optionally, the housing, towards the second, downstream, longitudinal end, may comprise a coupling configured to engage an outlet insert comprising a fuel injector tip. Advantageously, such a coupling may allow for different outlet inserts having different fuel injector tips for specific applications and spray patterns to be coupled to the injector. Optionally, the coupling comprises a thread configured to engage a corresponding thread of the outlet insert. Advantageously, a thread is a simple type of a coupling that may maintain secure engagement between the injector and the outlet insert. Optionally the fuel injector comprises a, or the, outlet insert comprising a, or the, injector tip. It is noted that while an “upstream end” or “fluid inlet” and a “downstream end” and “fluid outlet” of the injector are referred to herein, if the fuel injector comprises a, or the, outlet insert, the injector comprises elements downstream of its “downstream end” or “fluid outlet”. However, in this case, the term “downstream end” or “fluid outlet” of the injector refers merely to the “downstream end” or “fluid outlet” of the injector proper, or core of the injector, without the outlet insert. Optionally, the outlet insert may comprise an outlet insert passive valve for preventing upstream fluid flow from the injector tip towards the fluid outlet. The outlet insert passive valve may be an outlet insert pressure-operated control valve, or an outlet insert non-return valve. Advantageously, a pressure-operated control valve may prevent upstream fluid flow while allowing downstream fluid flow if a downstream fluid pressure exceeds a pressure threshold. A removable housing portion may be coupled reversibly to a remainder of the housing. Advantageously, having a portion of the housing, i.e. the removable housing portion, which is coupled reversibly to a remainder of the housing allows for increased versatility of the injector, thus allowing for the injector to be usable in a broader range of applications. Optionally, the remainder of the housing comprises a housing coupling configured to engage with a corresponding housing coupling of the removable housing portion. Advantageously, such a housing coupling may allow for easy coupling and decoupling of the removable housing portion and the remainder of the housing. Further optionally, the housing coupling comprises at least one of: a thread; a connecting portion configured to engage with the removable housing portion in a swaged manner; and a ferrule. Advantageously, a thread is a simple type of coupling that can maintain secure engagement between the injector and the outlet insert. Further advantageously, a connecting portion configured to engage with the housing portion in a swaged manner, and a ferrule, may allow for a secure yet releasable connection between the removable housing portion and the remainder of the housing. The removable housing portion may comprise the valve seat, the valve opening, the ball valve element, and the resilient element. Advantageously, by providing the valve seat, valve opening, ball valve element, and resilient element as part of the removable housing portion, appropriate selections of these elements may be made for each application. In particular, the size of the vale opening and ball valve element, and properties of the resilient element, may be adjusted to control the rate and amount of fluid flow per displacement of the ball valve element. A majority of the flow path may extend along the longitudinal axis of the housing. Optionally, at least 60 %, or at least 65 %, or at least 70 %, or at least 75 % of the flow path may extend along the longitudinal axis of the housing. According to a second aspect of the present disclosure, there is provided a fuel injection system comprising: a source of pressurised fuel, and a fuel injector according to any preceding claim, the source of fuel being connected to the fluid inlet. Advantageously, such a fuel injection system may be suitable for injection of a variety of different fuels. Optionally, the source of pressurised fuel is a source of hydrogen, a source of ammonia, a source of natural gas, a source of diesel, or a source of gasoline. The fuel injector of the first aspect, and the fuel injection system of the second aspect, may be suitable for direct injection of fuel. That is, they may be suitable for, or configured to, directly inject fuel into an engine. It will be appreciated that features described in relation to one aspect of the present disclosure may also be applied equally to all of the other aspects of the present disclosure. Features described in relation to the first aspect of the present disclosure may be applied equally to the second aspect of the present disclosure and vice versa. BRIEF DESCRIPTION OF DRAWINGS The disclosure will be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a side view of an example fuel injector; Figure 2 shows a cross-sectional perspective view of the example fuel injector of Figure 1; Figure 3 shows a top view of the example fuel injector of Figures 1 and 2; Figure 4a shows a cross-sectional side view of the example fuel injector of Figures 1, 2, and 3 in a closed configuration; Figure 4b shows a cross-sectional side view of the example fuel injector of Figures 1 to 4a in an open configuration; Figure 5a shows a partial cross-sectional bottom view along axis Y-Y’ of the example fuel injector of Figures 1 to 4b; and Figure 5b shows a cross-sectional bottom view along axis X-X’ of the example fuel injector of Figures 1 to 5a. DETAILED DESCRIPTION OF DRAWINGS Figure 1 shows a side view of a fuel injector 100, comprising a housing 102, which is made up of a first housing portion 104, which forms a permanent portion, or core, of the fuel injector 100, and a second, removable housing portion 106, coupled upstream to the first housing portion 104. Downstream of the housing 102 and coupled to the first housing portion 104 is an outlet insert 108 having a fuel injector tip 110. The fuel injector tip 110 has an opening 112 shaped to provide a desired spray pattern. As shown in Figure 2, at an upstream, longitudinal, end 200, the fuel injector 100 comprises five openings 202 (best seen in Figures 3) in an upstream end surface 204, which act as a fluid inlet. The fluid inlet allows fluid to flow into the housing 102 of the injector 100. Adjacent the fluid inlet, within the housing 102, the fuel injector 100 comprises a spring 206 arranged around a pin 208. Between the fluid inlet at the upstream end 200 of the injector 100, and a fluid outlet at a downstream end 210 of the injector 100 which comprises five openings 212 in a downstream end surface 214 of the injector 100, the housing 102 comprises a valve opening 216 and, around an upstream end of the valve opening 216, a valve seat 218. Arranged within the housing 102 and between the valve seat 218 and the spring 206 is a ball valve element 220. The spring 206 is configured to bias the ball valve element 220 towards the valve seat 218, to hold the ball valve element 220 in the valve seat 218 to close the valve opening 216. The injector 100 further comprises a plunger 222. The plunger 222 has a hollow cylindrical portion 224 and a downstream end portion 226 formed of a highly magnetic material. At an upstream end, the plunger 222 comprises a drive pin 228, which is provided press-fit into an upstream end of the plunger 222. The drive pin 228, at an upstream end, has a narrowed portion 229 arranged to extend through the valve opening 216. The drive pin 228 is held in the plunger 222 by a broadened connecting region 232. Surrounding the narrowed portion 229 of the drive pin 228 is a guide 230 which ensures alignment between the drive pin 228 and the valve opening 216. The guide 230 comprises five guide openings 231 which permit fluid flow from the valve opening 216 in a downstream direction. A central cavity 234 of the plunger 222 within the cylindrical portion 224 and the downstream end portion 226 extends along a (central) longitudinal axis A of the injector 100. As can be clearly seen from Figure 2, the injector 100, housing 102, and plunger 222 are all arranged coaxially around the longitudinal axis A. In other words, the longitudinal axis A of the injector 100, housing 102, and plunger 222 are the same. The central cavity 234 terminates in a downstream opening 236. At an upstream end, the cylindrical portion 224 comprises openings 238 in the wall of the hollow cylindrical portion 224, allowing fluid flow between the central cavity 234 and the upstream end 200 of the housing 102. Surrounding the plunger 222, the injector 100 further comprises an electrically conductive coil 240, and, attached to the electrically conductive coil 240, a magnetic portion 242, surrounding portions of the cylindrical portion 224 and the drive pin 228. Upon energisation, the electrically conductive coil 240 and magnetic portion 242 cause the plunger 222 to move in an upstream direction. Between the downstream end 210 of the injector 100 and the downstream opening 236 of the central cavity 234 of the plunger 222, and adjacent the fluid outlet, the injector 100 comprises a passive valve 244, configured to prevent upstream fluid flow from the fluid outlet towards the central cavity 234 of the plunger 222. The passive valve 244 is a pressure-operated control valve 244 that permits downstream fluid flow if a downstream fluid pressure exceeds a threshold, but prevents upstream fluid flow. The pressure-operated control valve 244 is a ball valve comprising a second spring 246 arranged around a second pin 248. The second spring 246 is configured to bias a second ball valve element 250 towards a second valve seat 252 surrounding a second valve opening 254 between the downstream opening 236 of the central cavity 234 and a downstream end 210 of the injector 100. The second spring 246, second valve seat 252 and second ball valve element 250 are arranged such that downstream fluid flow may displace the second ball valve element 250 from the second valve seat 252, but the second spring 246 biases the second ball valve element 250 back onto the second valve seat 252 when there is no downstream fluid flow. Upstream fluid flow is prevented as any upstream pressure, e.g. due to combustion pressures entering the injector 100, biases the second ball valve element 250 towards the second valve seat 252. The outlet insert 108 having the fuel injector tip 110 is arranged adjacent the downstream end 210 of the fuel injector 100. A central, cylindrical cavity 255 is formed in the hollow outlet insert 108, and is connected to the five openings 212 of the fluid outlet at the downstream end 210 of the injector 100 via a funnel 256. A portion 258 of the outlet insert 108 extends in a upstream direction over the downstream end 210 of the fuel injector 100. Said portion 258 is screwed onto the housing by means of a pair of threads 260 on the inside of the portion 258 and the outside of the downstream end 210 of the injector 100. The housing 102 comprises a removable, upstream, portion 262 and a core 264 formed of the remainder of the housing 102. The removable portion 262 and the core 264 are coupled by engagement of an annular grove in the core 264 and a corresponding annular projection 268 of the removable portion. As shown in Figure 3, the five inlet openings 202 are annularly distributed about the longitudinal axis A of the injector 100. The five inlet openings 202 are evenly distributed / spaced about the longitudinal axis A, meaning that each of the five inlet openings 202 is equidistant from the longitudinal axis A, and from one another. Also apparent from Figure 3 is that each inlet opening 202 extends through the upstream end surface 204 in a longitudinal direction. In other words, each opening 202 extends along an axis which is parallel to the longitudinal axis A, and perpendicular to the plane of the page. As best seen in Figure 2, the five outlet openings 212 are also annularly distributed about the longitudinal axis A of the injector 100, evenly distributed about the longitudinal axis A, and extending through the downstream end surface 214 in a longitudinal direction. Similarly, as best appreciated from Figure 2, the five guide openings 231 are also annularly distributed about the longitudinal axis A of the injector 100, evenly distributed about the longitudinal axis A, and extending through the guide 230 in a longitudinal direction. The upstream end of the cylindrical portion 224 comprises four upstream openings 238 in the cylinder wall, as best appreciated from Figure 5b. The four upstream openings 238 are annularly distributed evenly about a circumference of the cylindrical portion 224. Figure 4a shows the injector 100 in the closed configuration, or default configuration. In the closed configuration, the spring 206 biases the ball valve element 220 towards the valve seat 218, thus closing the valve opening 216. This prevents fluid from flowing through the valve opening 216. At the same time, the second spring 246 of the pressure-operated control valve 244 biases the second ball valve element 250 towards the second valve seat 252 to close the second valve opening 254. This prevents fluid from flowing through the second valve opening 254. Figure 4b shows the injector 100 in the open configuration, or actuated configuration. In the open configuration, a portion of the narrowed portion 229 of the drive pin 228 extends through the valve opening 216, moving the ball valve element 220 off the valve seat 218. A fluid flow path, indicated in Figure 4b by the arrows, leads from the inlet opening 202 (only one shown in Figures 4a and 4b), past the ball valve element 220 and the valve seat 218, and through the valve opening 216. The fluid flow path continues through the guide openings 231 (only one shown in Figure 4b) and into the magnetic portion 242 and, through the upstream openings 238, into the central cavity 234 within the plunger 222. From the central cavity 234, the fluid flow path leads out of the downstream opening 236 of the central cavity 234, and through the second valve opening 254 (which is opened by fluid flow pushing the second ball valve element 250 off the second valve seat 252, against the biasing force of the second spring 246). From the second valve opening 254, the fluid flow path extends, via the five outlet openings 212 (only one shown in Figure 4b), into and through the funnel 256 and into the cylindrical cavity 255 of the outlet insert 108, and out of the opening 112 (not shown in Figure 4b) of the fuel injector tip 110. In use, a fluid, such as hydrogen, may flowthrough the openings 202 in the upstream end surface 204 of the injector 100. In a default configuration, the valve opening 216 is closed by the ball valve element 220 being biased against the valve seat 218 by the compression spring 206. This prevents the fluid from flowing through the valve opening 216. Upon energisation of the electrically conductive coil 240, the magnetic portion 242 is energised and attracts the highly-magnetic downstream end portion 226 of the plunger 222. This movement of the plunger 222 in an upstream direction causes movement of the drive pin 228, pushing the narrowed portion 229 of the drive pin 228 through the valve opening 216 so that a portion of the narrowed portion 229 extends through the valve opening 216. This movement reconfigures the injector 100 into an open configuration, as the drive pin 228 moves the ball valve element 220 off the valve seat 218, against the biasing force of the spring 206. The pin 208 limits the movement of the ball valve element 220 in an upstream direction. Pushing the ball valve element 220 off the valve seat 218 permits fluid to flow through the valve opening 216, through the guide openings 231 in the guide 230 and into the central cavity 234 of the plunger 222 via the upstream openings 238 in the wall of the cylindrical portion 224 of the plunger 222. Within the plunger 222, the fluid flows via a flow path extending along the longitudinal axis A of the injector 100, and out through the downstream opening 236. The downstream fluid pressure then opens the pressure-operated control ball valve 244, as the fluid flow pushes the ball valve element 250 off the valve seat 252 to open the valve opening 254, against the biasing force of the spring 246. The pin 248 limits the downstream movement of the ball valve element 250. The ball valve element 250 being pushed away from the valve seat 252 allows fluid to flow towards the downstream end 210 of the injector 100 and out of the downstream end surface 214 via the outlet openings 212. Once the fluid has left the injector 100 proper, or “core” of the injector 100, it is funnelled into the cylindrical cavity 255 of the outlet insert 108 by the funnel 256, and exits the outlet insert 108 via the opening 112 of the fuel injector tip 110 to provide a desired spray pattern. Once a desired amount of fuel has been injected (or rather, the injector has been in an open configuration for a desired amount of time), the electrically conductive coil 240 is deenergised, de-energising the magnetic portion 242. As a result, the biasing force of the spring 206 returns the ball valve element 220 to the valve seat 218, thus closing valve opening 216, and preventing any further fluid from flowing through the valve opening 216. By pushing the ball valve element 220 in a downstream direction, the spring 206 also pushes the plunger 222 into the downstream direction. As there is no more fluid flowing through the plunger 222, the biasing force of the spring 246 returns the ball valve element 250 to the valve seat 252, thus closing the valve opening 254. 20 01 25

Claims

1. A fuel injector, comprising:a housing comprising:a fluid inlet at a first, upstream, longitudinal end of the housing;a fluid outlet at a second, downstream, longitudinal end of the housing;a valve opening disposed between the fluid inlet and the fluid outlet; and a valve seat surrounding the valve opening;a spherical ball valve element disposed within the housing;a resilient element arranged to directly bias the ball valve element towards the valve seat to close the valve opening; anda plunger configured to displace the ball valve element, wherein the fuel injector is configurable between a closed configuration, in which the ball valve element is held in the valve seat by the resilient element, and an open configuration, in which the plunger displaces the ball valve element away from the valve seat to permit fluid flow from the fluid inlet to the fluid outlet along a flow path comprising a flow path section extending along a longitudinal axis of the housing.

2. A fuel injector according to claim 1, wherein the flow path section extends within the plunger.

3. A fuel injector according to claim 1 or 2, wherein the plunger comprises a fluid flow channel, the flow path section extending at least through the fluid flow channel.

4. A fuel injector according to claim 3, wherein the fluid flow channel of the plunger terminates at a downstream opening.

5. A fuel injector according to claim 3 or 4, wherein the plunger comprises at least one upstream opening to permit fluid flow between the fluid flow channel of the plunger and the valve opening.

6. A fuel injector according to any preceding claim, wherein an upstream end of the plunger is configured to directly displace the ball valve element.20 01 257. A fuel injector according to any of claims 1 to 5, wherein an upstream end of the plunger is configured to indirectly displace the ball valve element.

8. A fuel injector according to claim 6, wherein the plunger comprises an integral drive pin aligned with the valve opening, or a fuel injector according to claim 7, wherein a drive pin is coupled to the plunger and aligned with the valve opening.

9. A fuel injector according to claim 8, wherein, in the open configuration, at least a portion of the drive pin extends through the valve opening to push the ball valve element away from the valve seat10. A fuel injector according to claim 8 or 9, further comprising a guide arranged to surround an upstream portion of the plunger, or the drive pin.

11. A fuel injector according to any preceding claim, wherein the resilient element, ball valve element, valve seat, and valve opening are arranged adjacent the fluid inlet.

12. A fuel injector according to any preceding claim, further comprising a passive valve for preventing upstream fluid flow from the fluid outlet towards the fluid inlet.

13. A fuel injector according to claim 12, wherein the passive valve is a passive ball valve; optionally wherein the passive ball valve comprises a second resilient element, a second ball valve element, and a second valve seat, wherein the second resilient element is arranged to bias the second ball valve element towards the second valve seat to close the second valve opening.

14. A fuel injector according to claim 12 or 13, wherein the passive valve is arranged adjacent the fluid outlet.

15. A fuel injector according to any preceding claim, wherein the fluid inlet comprises at least one inlet opening in the first, upstream, longitudinal end of the housing..

16. A fuel injector according to any preceding claim, wherein the fluid outlet comprises at least one outlet opening in the second, downstream, longitudinal end of the housing.

17. A fuel injector according to any preceding claim, further comprising: a coil;20 01 25a first magnetic element coupled to the coil and arranged to surround at least a portion of the plunger;and a second magnetic element forming at least part of the plunger,such that energisation of the coil energises the first magnetic element and causes the plunger to move, actuating the fuel injector from the closed configuration to the open configuration.

18. A fuel injector according to any preceding claim, wherein the housing, towards the second, downstream, longitudinal end, comprises a coupling configured to engage an outlet insert comprising a fuel injector tip.

19. A fuel injector according to claim 18, wherein the coupling comprises a thread configured to engage a corresponding thread of the outlet insert.

20. A fuel injector according to any preceding claim, further comprising a, or the, outlet insert comprising a, or the, injector tip.

21. A fuel injector according to any preceding claim, wherein a removable housing portion is coupled reversibly to a remainder of the housing.

22. A fuel injector according to claim 21, wherein the remainder of the housing comprises a housing coupling configured to engage with a corresponding housing coupling of the removable housing portion.;23. A fuel injector according to claim 21 or 22, wherein the removable housing portion comprises the valve seat, the valve opening, the ball valve element, and the resilient element.

24. A fuel injector according to any preceding claim, wherein a majority of the flow path extends along the longitudinal axis of the housing.

25. A fuel injection system, the system comprising:a source of pressurised fuel, anda fuel injector according to any preceding claim, the source of fuel being connected to the fluid inlet

Images