TECHNICAL FIELD

The present invention relates to a diesel injector for an internal combustion engine of an automotive vehicle that drastically reduces the risks of corrosion of a valve assembly.

BACKGROUND OF THE INVENTION

Usually, a diesel injector comprises a body provided with a bore, in which a needle is configured to reciprocate from a closed position of the injector to an open position of the injector. An electromagnetic coil is arranged to urge the reciprocating of the needle in the bore of the body by varying diesel pressure in a control chamber via a valve actuator. As is known, the valve comprises a body provided with a bore, in which a rod is configured to reciprocate depending on whether the coil is supplied with electrical current or not. Preferably, a sleeve is disposed in the valve bore to reduce the diesel leaks when the diesel pressure level is high.

In normal use, the quantity of water in diesel is not higher than 200 ppm. But, when the quantity of water in diesel accidentally increases, for instance, because of peculiar meteorological conditions, water can stagnate between the sleeve and the valve body and can provoke oxidation of the valve that can generate cracks of the valve in the oxidized areas.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to resolve the above mentioned problems in providing a control valve assembly for a diesel fuel injector, the control valve assembly comprising a valve body, a tubular sleeve and a valve spool, the valve body being provided with a channel opening into a bore, said bore extending along a longitudinal axis, the tubular sleeve being press-fitted in the bore, the sleeve having a wall defining an inner bore, said wall being provided with a radial hole to enable fuel to flow from the channel to said sleeve inner bore, the spool comprising a rod configured to reciprocate into said sleeve inner bore between a closed position of a valve seat preventing fuel to flow and an open position of the valve seat enabling fuel to flow from the channel toward an outlet fuel, the valve body being further provided with a first annular groove surrounding the body bore and wherein the channel opens and, wherein an interface between the sleeve and the valve body comprises a second annular groove contiguous to said first groove, the second groove having a substantially triangular cross-section comprising a chamfer forming an acute angle with said longitudinal axis within said first annular groove.

Thanks to the claimed arrangement, tensile stresses on the sleeve valve actuator decrease as well as uncertain contact lengths between the sleeve and the valve body. The circulation of water is improved, so that water does not stagnate between the sleeve and the valve body.

Said acute angle may be comprised between 40° and 75°.

Said angle may be of 50°.

Said second groove may be machined in the valve body.

Said second groove may be machined in the sleeve.

Said second groove may be machined in the valve body and in the sleeve.

The valve assembly may comprise a third groove under the first groove, said third groove having a substantially triangular section comprising a chamfer with an acute angle.

Said acute angle of the third groove chamfer may be comprised between 20° and 40°.

The angle of the sleeve groove chamfer may be of 30°.

It is another object of the invention to provide a diesel fuel injector for an internal combustion engine, said injector comprising: a body and a needle, the body being provided with a bore extending along a longitudinal axis, and comprising a diesel inlet and a diesel outlet, the needle extending from a head to a tip, and being configured to reciprocate in the bore along said longitudinal axis from a closed position to an open position, such that, in the closed position, the tip of the needle closes the diesel outlet, and, in the open position, the tip of the needle is spaced apart from the diesel outlet, a control chamber arranged to control said reciprocating of the needle in the bore, and control valve assembly as already described, the control valve assembly being arranged to control the pressure of the diesel in a control chamber. 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 a longitudinal view of an injector with a valve assembly according to the prior art.

Figure 2 is a perspective view of a valve assembly as per the invention configured to equip the injector of figure 1.

Figure 3 is a perspective view of a valve body of the valve assembly of figure 2.

Figure 4 is a longitudinal view of a detail of the valve body of figure 3. Figure 5 is a perspective view of a sleeve of the valve assembly of figure

2

Figure 6 is a longitudinal view of a detail of the sleeve of figure 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As can be seen from figure 1, a diesel injector 10 for an internal combustion engine comprises a body 12 and a needle 14. The body 12 comprises an elongated bore 16 extending longitudinally along a longitudinal axis, the bore 16 being provided with a diesel inlet 18 and a diesel outlet 20.

As also shown in figure 1, the needle extends from a head 22 to a tip 24 and is arranged to reciprocate in the bore 16 along the longitudinal axis X from a closed position to an open position.

In the closed position, the tip 24 of the needle 14 closes the diesel outlet 20, and, in the open position, the tip 24 of the needle 14 is spaced apart from the diesel outlet 20.

The injector 10 also comprises a control chamber 26 arranged to control the reciprocating of the needle 14 in the bore 16 via a valve assembly 28 that controls the pressure of the diesel in the control chamber 26.

As illustrated in figure 1, the valve assembly 28 comprises a valve body 30 and a rod 32.

The valve body 30 is provided with an elongated bore 34 extending along a longitudinal axis L preferably parallel to the longitudinal axis X of the injector bore 16. The valve body 30 also comprises a diesel entrance channel 36 and a diesel seat 38.

As can be seen from figure 1, the channel 36 is arranged to lead diesel from the control chamber 26 to the valve assembly 34. As particularly seen from figures 1 and 3, the channel 26 ends in the valve assembly 28 in a first annular groove 39 protruding from the valve body 30.

The rod 32 extends along the longitudinal axis L in the bore 34 to reciprocate between a closed position and an open position, such that the reciprocating of the rod 32 controls the diesel charge and discharge in the control chamber 26.

The valve assembly 28 also comprises a magnetic frame 40 fixed to the rod 32 and arranged to cooperate with a magnetic coil (not illustrated). When the coil is supplied with electrical current, the frame 40 lifts in the bore 34 and diesel flows from the diesel exit 38 to the diesel tank. The diesel pressure in the control chamber quickly reduces and this discharge leads to the lifting of the needle 14 in the bore 16, opening the diesel outlet 20. When is the coil is not supplied with electrical current, a spring (not illustrated) reinstate the sealing in the actuator, which closes the diesel outlet 20.

As can be seen from figures 1, 2 and 5-6, the valve actuator 28 comprises a tubular sleeve 42 disposed in the bore 34 around the rod 32 to limit leaks that could happen when the pressure in the injector is high (2000 bars for instance).

The sleeve 42 is press-fitted in the valve body 30.

The sleeve 42 comprises a wall 440 defining an inner bore 460, the wall 440 being provided with a radial hole 480 to enable fuel to flow from the channel 36 to said sleeve inner bore 460.

As already explained, the valve assembly 28 of the prior art can be damaged because of oxidation of the valve.

The valve assembly 44 as per the present invention is now detailed in reference to figures 2 to 6. Indeed, the actuator 44 can be installed in the injector 10 of figure 1 instead of the known valve assembly 28, the functioning of the injector, and, in particular, the charge and discharge if the diesel in the injector 10 being left unchanged. The valve body 30 of the valve assembly 44 is configured to reduce any risk of corrosion of the valve, as is now described.

As particularly seen in figures 3 and 4, the valve body 30 presents a general cylindrical shape extending along the longitudinal axis L. The interface between the valve body 30 and the sleeve 42 comprises an annular grove 46. On the illustrated embodiment, the annular groove 46 is made in the valve body 30.

As can be seen from figure 3, the groove 46 of the valve body 30 is disposed in a first contact zone Z between the sleeve 42 and the valve body 30, also called top ring. In the contact zone Z, the annular groove 46 is disposed just below a plain bearing P between the sleeve 42 and the valve body 30.

As can also be seen from figure 3, the annular groove 46 is contiguous to the first annular groove 39. In other words, the annular grooves 39 and 46 are disposed in contact, next to each other such that the annular groove 46 opens in the first annular groove 39.

The groove 46 is provided with a chamfer 48 forming an angle A with the longitudinal axis L in the direction of the needle 14 of the injector 10, as best seen in figure 4.

Differently said, the angle A is formed by the initiation between the plain bearing P and the beginning of the groove 46.

The angle A is preferably comprised between 40° and 75°. The angle A ensures a reduction of the tensile stresses between the sleeve and the valve body 30 and a decrease of uncertain contact length that can generate fretting corrosion. Also, the angle A improves the circulation of the water in the valve since it prevents dead area from existing in the valve, said dead area implying stagnant water in the valve, and hence risk of oxidation of the valve.

The angle A further guarantees a gradual reduction of pressure of the diesel in the first contact zone Z.

Advantageously, the angle A is comprised between 42° and 65°, specifically of 50°, which value particularly reducing risk of corrosion and damage, as tests led by the Proprietor have shown.

A depth D of the annular groove 46 is preferably chosen between 0.1 mm and 0.2 mm, advantageously 0.15 mm. An associated angle B between a down end 49 of the annular groove 46 and the longitudinal axis L in a direction opposed to the needle is consequently between 10° to 20°, preferably 15°. The angle B and the depth D allow the control the volume of the annular groove 46.

The sleeve 42 of the valve assembly 46 is configured to reduce any risk of corrosion of the valve, as is now described.

As can be seen from figures 5 and 6, the sleeve 42 is of a general cylindrical shape longitudinally extending along the longitudinal axis L. The sleeve 42 comprises an annular groove 50.

As can be seen from figure 3, the groove 50 of the sleeve 42 is disposed in a second contact zone ZZ between the sleeve 42 and the valve body 30, also called bottom ring. In the contact zone ZZ, the annular groove 50 is disposed just above a plain bearing PP between the sleeve 42 and the valve body 30.

The groove 50 is provided with a chamfer 52 forming an angle AA with the longitudinal axis L in the direction opposite to that of the needle 14 of the injector 10, as best seen in figure 6.

Differently said, the angle A is formed by the initiation between the plain bearing PP and the beginning of the groove 50.

The angle AA is comprised between 20° and 40°, preferably 30°.

The angle AA ensures an increase circulation of backwater by reducing dead area without modifying stresses.

As can be seen from the figures, the annular grooves 46 and 50 present each a substantially triangular cross-section.

Thanks to the present invention, in particular the chamfered grooves 46 and 50, two criteria are optimized: the stagnant water and the uncertain contact length are reduced.

Thanks to the present invention, the injector 10 can be used in countries and conditions where gas oil contains more than 0.15% of water (1500 ppm to 5000 ppm), as tests led by the Proprietor have shown.

LIST OF REFERENCES

X longitudinal axis of the bore of the injector

L longitudinal axis of the bore of the valve

Z first contact zone

P first plain bearing D depth of the annular groove 46

ZZ second contact zone

PP second plain bearing

10 diesel injector

12 body

14 needle

16 bore of the body

18 diesel inlet

20 diesel outlet

22 needle head

24 needle tip

26 control chamber

28 valve assembly (prior art)

30 valve body

32 valve rod

34 valve bore

36 fuel channel

38 seat

39 first annular groove

40 magnetic armature

42 sleeve

440 sleeve wall

460 inner bore

480 radial hole

44 valve assembly (invention)

46 valve body groove

48 chamfer of valve body groove

49 end of groove

50 sleeve groove

52 chamfer of sleeve groove