The present invention relates to a fuel injector and more particularly to a cap to be plugged over the normal connector of the injector, said cap being provided with an electronic PCB able to process sensor signals. BACKGROUND OF THE INVENTION

Control of high pressure fuel injection equipment, such as common rail injection equipment, takes into account fuel pressure and other characteristics measured by a sensor arranged on the common rail. EP2694795, JP2013007341 and EP2188517 further disclose embodiments of fuel injectors comprising a pressure sensor arranged directly in their housing, so that the actual pressure inside the injector is determined and sent to the control unit of the injection equipment. To achieve more demanding performances accelerometer's, temperature sensors and other type of sensors than pressure sensors may be arranged on fuel injector's body.

The downside of these added sensors is the electrical connection which requires wires and added terminals in the injector's connector or even added specific connector.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to solve the above mentioned problems in providing an electronic printed circuit board (PCB) adapted to receive and process sensor signals. The PCB is provided with connecting means for connecting the electronic circuit of the PCB to electrical drive terminals of an actuator of a fuel injector. The drive terminals are themselves connectable to a control unit piloting the actuator via complementary engagement of a connector of the control unit to the connector of the injector so that, the sensor signals may be transmitted to the control unit. In an embodiment, the connecting means are sprung conductive blades directly extending from the PCB and adapted to be sprung over the drive terminals.

In another alternative, the connecting means are wire cables extending from the PCB and adapted to be soldered or welded on the drive terminals.

Also, the PCB may be provided with an electronic chip loaded with trim data characterizing the injector so that, said trim data are available to the control unit.

Furthermore, the PCB may be provided with an electronic memory chip to temporarily store the sensor signals so that, said signal are transmitted to the control unit between sequences of injections therefore avoiding over-lap of sensor signal transmission and the injector drive current.

The PCB can further be provided with a sensor, such as an accelerometer, directly fixed on the PCB.

The invention extends to a cap of a connector of a fuel injector, the connector receiving electrical terminals of the actuator of the fuel injector and being adapted to connect said electrical terminals to a control unit piloting the actuator. The cap defines an internal volume in which is arranged an electronic

PCB as described in the preceding paragraphs.

The cap is further provided with locking means adapted to lock the cap on the connector, the locking means comprising a plurality of elastic tabs arranged around the cap and adapted to hook with complementary means provided on the connector.

The cap is further provided with sealing means, such as an O-ring, ensuring in use, sealing interface with the connector.

The invention also extends to an arrangement comprising a cap as previously described and a sensor remotely connected to the PCB via a conductor arranged externally to the connector.

The sensor can be a pressure sensor or a temperature sensor or a flow sensor or a strain gauge or any type of sensor used in fuel injection equipment.

Also, the PCB can be remotely connected to a plurality of sensors. The invention also extends to a connector of a fuel injector provided with a cap or with an arrangement as previously described.

The invention also extends to a fuel injector provided with such a connector.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now described by way of example with reference to the accompanying drawings in which:

Figure 1 is an axial view of a fuel injector provided with a sensor and the necessary electronics as per the invention.

Figure 2 is a top view of the injector of figure 1.

Figure 3 is an axial cross section of the head portion of the injector of figures 1 and 2.

Figure 4 is a magnified detail of figure 3.

Figure 5 is a bottom view of the cap of the connector of the injector of figures 1 to 4.

Figure 6 is a view of an electronic printed circuit board arranged in the cap of figure 5.

Figures 7, 8 and 9 are three examples of arrangement of sensors on a fuel injector, each sensor being connected to an electronic PCB as shown in figure 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A fuel injector 10 is described in reference to figures 1, 2, 3 and 4. The injector 10 has a body 12 extending along a main axis A. In the body 12 is arranged a coil actuating a valve, which hydraulically pilots the displacements of a needle in order to enable or to prevent fuel injection events through a nozzle 14 drawn at the bottom of the figure.

The body 12 further comprises a high pressure fuel inlet 16 and a low pressure fuel outlet 18 for high pressure fuel to enter the injector 10 via the inlet 16 and either be injected via the nozzle 14 or be recirculated toward a low pressure tank, exiting the body 12 via the outlet 18. The inlet 16 radially extends from the body 12 and, as represented on the figure, it is fluidly connected to a high pressure pipe 20. In the vicinity of the inlet 16, the injector 10 of figure 1 is further provided with a sensor 22 arranged in housing protruding from the body 12 and closed by a cap screwed on the body 12. The sensor 22 can be an accelerometer, a pressure sensor, a strain gauge, a temperature sensor, a flow sensor, or a combination of several sensors.

To the opposite end of the nozzle 14, the body 12 is provided with an electrical connector assembly 24 comprising a connector body 26 having an axial extension 28 which lower end is fixedly engaged in a bore 30 of the injector body 12 and which upper end 32 is open. The connector body 26 further comprises a radial extension 34 forming connection means adapted to complementary engage with another electrical connector of an external control unit.

In the axial extension 28 protrude terminals 36, such as rigid cables, upwardly extending in the injector body 12 from the coil and which upper ends are clamped into sprung blades and therefor electrically connected to radial electrical pins extending in the radial extension 34. Alternatively, the pins can be crimped or brazed or welded, onto the ends of the terminals 36.

The upper open end 32 of the connector body 26 is sealingly capped with a cap assembly 38 comprising a cap body 40 for complementary engagement with said upper open end 32 of the connector body 26, an electronic printed circuit board (PCB) 42 arranged in the cap body 40 and further connection means 44 for connecting said PCB 42 to the sensor 22. As represented on the figures, said further connection means 44 may be a wire extending from the sensor 22 to the cap assembly 38. The routing of the wire around the injectors' body 12 depends on the relative orientation of the sensor 22 and of the cap assembly 38. As shown, said routing may comprise several curvatures in order to follow the body 12 of the injector.

The upper open end 32 of the connector body 26 is cylindrical with a flat section oriented just above the radial extension 34 forming connection means. Alternatively, said upper end 32 could be totally cylindrical or have any other shape.

Nearby the upper open end 32, the connector body 26 comprises a double wall formed with an inner wall 46 provided with a small shoulder 48 receiving an O-ring seal 50 and, an outer wall 52, radially parallel and distant from the inner wall 46, the external face of the outer wall 52 being provided with a circular protrusion 54 defining under it a groove 56.

The cap body 40 has a complementary shape and comprises an annular base 58 and a hat 60. From the annular base 58 downwardly extend a complementary double wall formed with an inner wall 62 and a plurality of regularly spaced tabs 64, all together forming an outer wall. More visible on the detail of figure 4, the tabs 64 are provided on their inner face with a protrusion 66 adapted to complementary engage in the groove 56 formed in the outer wall 52 of the connector body and therefore forming locking means for fixedly attaching the cap on the connector body. Downwardly extending from the annular base 58, the tabs 64 are slightly resilient, able to minor radial bending.

The inner wall 62 of the cap body 40 engages in the annular space of the connector body 26 between its own inner wall 46 and outer wall 52. Said inner wall 62 of the cap body defines with the annular base 58 another shoulder 68, the O-ring 50 being arranged between the two shoulders 48, 68, and between the two inner walls 46, 62.

Over the annular base 58 is placed the hat 60 of the cap body which has a peripheral wall 70 upwardly extending from said annular base 58 and, an upper transverse face 72 closing the hat 60.

As visible in the section of figure 3 and also on figures 5 and 6, the PCB 42 is arranged in the volume defined inside the hat 60. An exemplary PCB 42 is represented on figure 6 and it is upwardly held from the annular base 58 thanks to upward legs 74, four being represented on the figure. From the PCB downwardly extend two sprung conductive blades 76 forming electrical connection means to the PCB 42. Although it might not be needed, in an alternative represented on the figures, the hatching inside the hat 60 represent potting of the PCB 42 with material such as an epoxy, silicone or fluorosilicone resin or gel.

The cap assembly 38 is arranged over the connector body 26 by

downwardly engaging the inner wall 62 of the cap body in the connector body between its inner and outer walls 46, 52. Simultaneously, the tabs 64 surrounds the outer wall 52 of the connector body, until engagement of the locking means 66, 56, that fixedly maintain the cap on the connector. Inside the assembly, the two sprung conductive blades 76 engage in the central hole of the connector body 26 and force their way by elastically outwardly deforming to come in electrical contact with the upper ends of the coil terminals 36 so that, the PCB 42 is in contact with the coil terminals 36 and therefore with the radial electrical pins extending in the radial extension 34 of the connector.

While the arrangement of the sensor 22 has been described in reference to figures 1 and 2, the injector 10 may be provided with other type of sensors. For instance, the PCB 42 can be directly provided with a sensor such as an

accelerometer 78 enabling to measure the axial sudden opening and closing of the needle. In this case, the accelerometer 78 being directly on the PCB, there is no need for wires 44, unless the injector 10 is provided with several sensors.

In reference to figure 7 is represented another sensor 80 screwed directly into the injector. This is convenient for small sensors such as a pressure sensor 80 which reads the movement of a diaphragm using fibre-optics.

In reference to figure 8 is represented yet another sensor 82 clamped to a cylindrical surface of the injector using a screw in a similar manner to a hose clip to tighten the sensor around a cylindrical surface. This is particularly suitable for a strain gauge used to measure the dilation of surface under internal injector pressure. The inlet of the injector is a convenient location for such a sensor as the high pressure bore here can be relatively large and it is possible to attach the sensor with little or no modification to the injector. Such a sensor is detailed in application GB1415839.

In reference to figure 9 is yet another sensor 84 incorporated into a plastic clip. The advantage of such a clip is that is flexible enough in diameter to assemble into a groove machined into the injector. Such a groove enables a larger strain signal to be seen by the sensor since it is closer to the bore, wherein flows high pressure fuel, than is the clamped sensor of figure 8. In the case of a plastic clip, it is likely that glue would be used in addition to ensure that the sensor remains firmly coupled to the surface over life. Such a sensor 84 is also detailed in application GB1415839.

The PCB 42 is provided with the electronic components needed to acquire process and transmit the signals coming from the various sensors. Furthermore, the PCB 42 can be provided with an electronic chip 86 in which are recorded the trim data characterizing the injector 10. Said trim data are measured at the end of the production line and are specific to each injector and therefore, the external control unit piloting several injectors takes into account said data to command each one of the injectors.

In addition, in order to avoid conflict between the commands from the control unit to the coil and the sensors' signals from the PCB to the control unit, the PCB 42 may be provided with an electronic memory component 88 wherein the sensors' signals are recorded and kept when the control unit sends commands to the coil, said sensors' signals being sent to the control unit between the commands to the coil.

The following references have been utilized in this description:

A main axis

10 fuel injector

12 head o f the inj ector

14 nozzle of the injector

16 high pressure inlet

18 low pressure outlet

20 pressure pipe

22 sensor

24 connector assembly

26 connector body

28 axial extension of the connector assembly

30 bore

32 upper end of the connector body

34 radial extension of the connector assembly

36 coil terminals

38 cap assembly

40 cap body

42 PCB

44 connection means

46 inner wall of the upper open end of the connector body

48 shoulder 50 O-ring

52 outer wall

54 circular protrusion

56 groove

58 annular base of the cap boc

60 hat

62 inner wall of the cap body

64 tabs

66 protrusion

68 shoulder of the cap body

70 peripheral wall of the hat

72 upper face of the hat

74 legs

76 sprung conductive blades

78 accelerometer

80 pressure sensor

82 sensor

84 sensor

86 electronic chip

88 electronic memory