Injector

An injector is disclosed which comprises a nozzle body arranged to receive fuel under pressure from a pumping chamber. An injection control arrangement in the form of a valve controls injection timing, and a drain control arrangement in the form of a valve controls communication between the pumping chamber and a fuel reservoir. An electromagnetic actuator controls operation of both valves, the actuator including a single, common armature which is associated with both of the valves.

This invention relates to an injector for use in supplying fuel to a 
cylinder of an internal combustion engine. In particular, the invention 
relates to an injector capable of being operated so that the fuel pressure 
at the time of injection is controllable independently of the timing of 
injection. 
An injector capable of being operated as set out above comprises a drain 
valve operable to control communication between a suitable low pressure 
reservoir and a supply line for supplying fuel at high pressure to an 
injection nozzle, and a control valve arranged to permit control of the 
movement of a valve needle provided in the injection nozzle. The timing of 
injection is controlled by the control valve, the injection pressure being 
determined by the timing of operation of the drain valve with respect to 
the timing of operation of the control valve. Electromagnetic actuators 
are provided for controlling operation of the drain and control valves. 
The electromagnetic actuators may comprise individual armatures associated 
with the drain and control valves, the armatures being moveable under the 
influence of a single stator arrangement. 
It is an object of the invention to provide an injector of the type 
described hereinbefore of relatively simple construction. 
In accordance with the invention there is provided an injector for 
injecting fuel into a combustion chamber of an engine during an injection 
sequence comprising: 
pump means including a pumping chamber; 
an nozzle body having an outlet orifice; 
a fuel line interconnecting the pumping chamber and the nozzle body; 
drain control means controlling communication between the pumping chamber 
and a fuel reservoir; 
injection control means for controlling the injection of pressurized fuel 
through the orifice to the engine combustion chamber; and 
an electromagnetic actuator including a common armature for controlling the 
operation of the injection control means and the drain control means. 
The provision of a single, common electromagnetic actuator including a 
single, common armature reduces the complexity of the injector, the 
electrical connections to the controller only requiring the connection of 
one electromagnetic actuator. 
The injector conveniently comprises a pump/injector, the pump means forming 
part of the injector.

The injectors illustrated in the accompanying drawings are very similar to 
one another and apart from where indicated, the description hereinafter is 
applicable to both injectors. In the drawings, like reference numerals are 
used to denote like parts. 
The injectors illustrated in the accompanying drawings each comprise a 
valve needle 10 which is slidable within a bore 12 formed in a nozzle body 
70 (see FIG. 2). The bore 12 includes an annular chamber 14, the part of 
the needle 10 received within the annular chamber 14 including a thrust 
surface 16 arranged such that the application of high pressure fuel to the 
chamber 14 tends to lift the valve needle 10 away from a seating 18, the 
needle 10 being biased into engagement with the seating 18 by means of a 
spring 20 which is located in a spring chamber 22. As illustrated in FIG. 
2, the spring chamber 22 may be defined, in part, by a bore provided in a 
spring housing 72. An end region of the needle 10 extends into the chamber 
22. The chamber 14 communicates through a supply passage 24 with a pump 
chamber 26 within which a pumping plunger 28 is reciprocable. The pumping 
plunger 28 is conveniently arranged to be moved under the action of a cam 
and tappet arrangement (not shown) to compress the fuel within the pumping 
chamber 26, outward movement of the pumping plunger 28 conveniently 
occurring under the action of a spring (not shown). The supply passage 24 
communicates through a restrictor 30 with the chamber 22. 
A valve arrangement is provided in order to control the operation of the 
injector, the valve arrangement comprising a bore 32 provided in a control 
valve housing 73 (see FIG. 2) within which a control valve member 34 is 
slidable, a spring 36 being arranged to bias the valve member 34 into 
engagement with a seating defined by part of the bore 32. The control 
valve member 34 is of relatively large diameter, and the spring 36 is 
engaged between the control valve member 34 and a step defined between the 
control valve housing 73 and a drain valve housing (described 
hereinafter). Downstream of the seating, the bore 32 communicates through 
a passage 38 with a suitable low pressure drain 74 (see FIG. 2). Upstream 
of the seating, the bore 32 defines an annular chamber 40 which 
communicates with the chamber 22. It will be appreciated, therefore, that 
the position of the control valve member 34 determines whether or not the 
chamber 22 communicates with the low pressure drain. 
A drain valve housing 42 is mounted upon the control valve housing 73, a 
bore 44 being provided in the drain valve housing 42, the bore 44 being 
coaxial with the bore 32. A drain valve member 46 is slidable within the 
bore 44, the drain valve member 46 being biased towards a seating defined 
by part of the bore 44 by means of a spring 48 engaged between the drain 
valve member 46 and the control valve member 34. Upstream of the seating, 
the bore 44 and drain valve member 46 define an annular chamber 50 which 
communicates with the passage 24, the part of the bore 44 downstream of 
the seating communicating through a passage 52 with the low pressure drain 
74. 
In order to control the positions of the drain and control valve members 
34, 46, an electromagnetic actuator is provided. The electromagnetic 
actuator comprises a stator 54 provided with a winding, and an armature 56 
which is moveable under the influence of the magnetic field generated by 
applying an electrical current to the winding. A helical spring 58 is 
provided to bias the armature 56 away from the stator 54. 
The armature 56 is located coaxially with the bores 32, 44, the armature 56 
being provided with a rod 60 which extends into the bore 44, the rod 60 
sealingly engaging the bore 44 downstream of the connection of the bore 44 
and passage 52 to substantially prevent leakage of fuel from the bore 44. 
The rod 60 is a piston-like sliding fit within an axially extending bore 
provided in the drain valve member 46, and similarly is a sliding fit 
within an axially extending bore provided in the control valve member 34. 
The rod 60 includes a region 60a of relatively large diameter and a region 
60b of relatively small diameter, a shoulder defining the connection of 
the parts 60a and 60b. The drain valve member 46 is biased into engagement 
with the shoulder by means of the spring 48. The lowermost part of the rod 
60 includes an outwardly extending flange 64, and in use, as described 
hereinafter, the flange 64 is engageable with the lowermost part of the 
control valve member 34. 
In use, starting from the position illustrated in the accompanying 
drawings, the winding is not energised thus the armature 56 is biased by 
means of the spring 58 away from the stator 54 and the engagement of the 
drain valve member 46 with the shoulder of the rod 60 results in the drain 
valve member 46 occupying a position in which it is spaced from its 
seating. The pump chamber 26 therefore communicates with the low pressure 
drain. The position of the rod 60 is such that the flange 64 is spaced 
from the lower end of the control valve member 34, and the control valve 
member 34 is biased into engagement with its seating by the spring 36. The 
chamber 22 therefore does not communicate with the low pressure drain and 
the fuel pressure within the chamber 22 is substantially equal to that 
within the pumping chamber 26. Similarly, the pressure applied to the 
annular chamber 14 is substantially equal to the pressure within the 
pumping chamber 26, and as the area of the thrust surface 16 is smaller 
than the effective area of the part of the needle 10 exposed to the fuel 
pressure within the chamber 22, the effect of the fuel pressure on the 
needle 10 together with the effect of the spring 20 results in the needle 
10 occupying a position in which it is in engagement with the seating 18. 
The pumping plunger 28 is being pushed outwardly under the action of the 
spring (not shown) thus increasing the volume of the pumping chamber 26 
and drawing fuel into the pumping chamber 26 through the passage 52 past 
the drain valve member 46. 
Subsequently, the plunger 28 will commence inward movement under the action 
of the cam arrangement. The inward movement of the pumping plunger 28 
results in fuel from the pumping chamber 26 being displaced back past the 
drain valve member 46 to the passage 52 and from there to the low pressure 
drain. When it is desired to commence pressurizing the fuel within the 
chamber 26, a current is applied to the winding to generate a magnetic 
field resulting in movement of the armature 56 against the action of the 
spring 58 to a sufficient extent to permit the drain valve member 46 to 
move into engagement with its seating under the action of the spring 48. 
The current is subsequently allowed to fall to a first holding current 
level sufficient to maintain the armature in this position. The movement 
of the armature 56 may be sufficient to bring the flange 64 into 
engagement with the lower surface of the control valve member 34 but is 
insufficient to lift the control valve member 34 away from its seating 
against the action of the spring 36 which, conveniently, is relatively 
highly pre-loaded. The movement of the armature 56 is therefore sufficient 
to break the communication between the pumping chamber 26 and the low 
pressure drain, but is insufficient to cause the chamber 22 to communicate 
with the low pressure drain. 
As the pumping chamber 26 no longer communicates with the low pressure 
drain, further inward movement of the pumping plunger 28 results in the 
pressure within the pumping chamber 26 increasing. As the pressure applied 
to the chamber 22 is substantially equal to that applied to the chamber 
14, the needle 10 remains in contact with its seating as described 
hereinbefore thus injection does not commence. 
When injection is to commence, the winding is fully energised to lift the 
armature 56 against the action of the springs 36, 48, 58 by a further 
amount, the engagement of the flange 64 with the lower end of the control 
valve member 34 resulting in the control valve member 34 being lifted from 
its seating thus permitting communication between the chamber 22 and the 
low pressure drain. The current is subsequently allowed to fall to a 
second holding current level sufficient to maintain the armature in this 
position. As the chamber 22 now communicates with the low pressure drain, 
the pressure applied to the part of the valve needle 10 exposed to the 
pressure within the chamber 22 is insufficient to maintain the needle 10 
in engagement with its seating thus the needle 10 is moved against the 
action of the spring 20 and fuel is supplied from the pumping chamber 26 
past the seating 18 to be injected through outlet orifices provided in the 
end of the nozzle body. It will be appreciated that the provision of the 
restrictor 30 restricts the flow of fuel to the chamber 22 thus as the 
chamber 22 communicates with the low pressure drain, the flow of fuel to 
the chamber 22 is insufficient to raise the pressure therein to a level 
great enough to result in movement of the needle 10 into engagement with 
its seating. 
In order to terminate the injection, the current applied to the winding is 
reduced thus the armature 56 moves under the action of the springs 36, 48, 
58 away from the stator 54 to an extent sufficient to permit the control 
valve member 34 to move into engagement with its seating. Such movement of 
the control valve member 34 breaks the communication between the chamber 
22 and low pressure drain thus the restricted flow of fuel to the chamber 
22 results in the pressure therein increasing to an extent sufficient to 
assist the spring 20 in returning the needle 10 into engagement with its 
seating. Injection is then terminated. 
If another injection is required while the plunger 28 continues to move 
inwards, for example where a pilot injection is to be followed by a main 
injection, the winding is fully energised once more to lift the control 
valve member 34 away from its seating thus commencing injection again as 
described hereinbefore. Such injection is terminated in the same manner as 
described hereinbefore. 
After injection has been terminated, the winding is fully de-energised and 
the armature 56 moves under the action of the spring 58 to the position 
shown. Such movement of the armature 56 results in the drain valve member 
46 being lifted from its seating thus permitting fuel to flow from the 
pumping chamber 26 to the low pressure drain. The pressure in the pumping 
chamber 26 is therefore relieved. Continued inward movement of the pumping 
plunger 28 results in further fuel from the pumping chamber 26 being 
displaced past the drain valve member 46 to the low pressure drain. 
Subsequently the pumping plunger 28 will commence outward movement under 
the action of the spring and filling of the pumping chamber 26 will occur 
as described hereinbefore ready for another pumping cycle to commence. 
It will be appreciated that the presence of the separate drain and control 
valve arrangements permits the pressure of fuel within the pumping chamber 
26 at the commencement of injection to be controlled independently of the 
timing of injection, the pressure within the pumping chamber 26 being 
dependent upon the timing at which the drain valve member 46 closes with 
respect to the timing at which the control valve member 34 is lifted from 
its seating to commence injection. As control of both of the valve members 
is achieved using a single electromagnetic actuator including a single, 
common armature 56, it will be appreciated that the only electrical 
connections required to control operation of the injector are the 
connections of the winding. Manufacture and installation of the injector 
are therefore relatively simple.