Patent Application
20170002782
This application is based on and incorporates herein by reference Japanese Patent Application No. 2015-133663 filed on Jul. 2, 2015.
The present disclosure relates to a fuel injection valve that injects fuel into an internal combustion engine.
A conventional fuel injection valve includes a nozzle needle that opens or closes an injection hole through which a fuel is injected into an internal combustion engine, a control room into which a high-pressure fuel is introduced to urge the nozzle needle in a valve closing direction, an orifice body having a discharge passage through which the fuel in the control room is discharged to a low pressure portion, and a valve body that opens or closes the discharge passage by contacting with or separating from a flat sheet surface formed on the orifice body.
Upon opening of the discharge passage, the high-pressure fuel in the control room is released to the low pressure portion through the discharge passage. Accordingly, a pressure in the control room decreases, and the nozzle needle is driven to move in a valve opening direction, thereby opening the injection hole (refer to JP H10-153155 A corresponding to U.S. Pat. No. 5,839,661, U.S. Pat. No. 6,027,037, for example).
Fuel containing various foreign objects, i.e. low-quality fuel is anticipated to be widely used. When a foreign object of the fuel is stuck between the valve body and the sheet surface in vicinity of a corner part (i.e. outlet edge part) in which the sheet surface intersects with the discharge passage, the corner part escapes toward the discharge passage easily, i.e. deforms easily. Accordingly, a crack is likely to be generated in the corner part. Subsequently, damage of the sheet surface may progress from the crack of the corner part by fluid abrasive action of fine foreign objects contained in the fuel discharged through the discharge passage to the low pressure portion.
As a result, even when the valve body is in contact with the sheet surface, and the discharge passage is closed, the high-pressure fuel may leak through the damaged part of the sheet surface to the low pressure portion. Hence, a fuel injection amount and a fuel leakage amount may increase.
It is an objective of the present disclosure to limit generation of a crack caused by foreign objects stuck in a fuel injection valve.
According to an aspect of the present disclosure, a fuel injection valve includes a nozzle needle, a control room, an orifice body, a valve body, and a chamfered part. The nozzle needle opens or closes an injection hole through which a fuel is injected into an internal combustion engine. A high-pressure fuel is introduced into the control room to urge the nozzle needle in a valve closing direction. The orifice body includes a discharge passage through which the fuel is discharged from the control room to a low pressure portion, and an orifice-body sheet surface that is flat and surrounds a downstream end part of the discharge passage. The valve body contacts with or separates from the orifice-body sheet surface to close or open the discharge passage. The chamfered part is provided on a corner part in which the orifice-body sheet surface intersects with the discharge passage.
The chamfered part is provided in the corner part where the orifice-body sheet surface intersects with the discharge passage. Hence, the corner part is unlikely to be deformed toward the discharge passage even when a foreign object is stuck between the valve body and the orifice-body sheet surface in vicinity of the corner part. Therefore, generation of crack can be restricted.
Furthermore, if the chamfered part is not provided in the corner part where the orifice-body sheet surface intersects with the discharge passage, a flow direction of the fuel discharged through the discharge passage to the low pressure portion is drastically changed in vicinity of the corner part. Hence, fluid abrasive action force becomes large. On the other hand, when the chamfered part is provided in the corner part where the orifice-body sheet surface intersects with the discharge passage, a flow direction of the discharged fuel is changed moderately. Therefore, the fluid abrasive action force can be reduced.
The disclosure, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings, in which:
Embodiments of the present disclosure will be described hereinafter referring to drawings. In the embodiments, a part that corresponds to a matter described in a preceding embodiment may be assigned with the same reference numeral, and redundant explanation for the part may be omitted. When only a part of a configuration is described in an embodiment, another preceding embodiment may be applied to the other parts of the configuration. The parts may be combined even if it is not explicitly described that the parts can be combined. The embodiments may be partially combined even if it is not explicitly described that the embodiments can be combined, provided there is no harm in the combination.
A first embodiment of the present disclosure will be described below. A fuel injection valve according to the present embodiment is attached to a cylinder head of an internal combustion engine (e.g., a compression ignition internal combustion engine). The fuel injection valve injects a high-pressure fuel accumulated in a common rail into a combustion chamber of the internal combustion engine.
As shown in
The lower body 12 includes an inflow port 120 through which the high-pressure fuel supplied from the common rail is introduced into the body 1 as shown by an arrow in
The nozzle body 10 includes an injection hole 102 through which the high-pressure fuel introduced into the fuel accumulation room 101 is injected into the combustion chamber of the internal combustion engine, and a nozzle-body sheet portion 103 that has a tapered shape and is provided on an upstream side of the injection hole 102 in a flow direction of the fuel.
A nozzle needle 2 having a step cylinder shape is disposed inside the nozzle body 10 and the lower body 12.
The nozzle needle 2 includes a nozzle-needle sheet portion 21 having a tapered shape, a small-diameter cylindrical portion 22, a pressure receiving portion 23, a large-diameter cylindrical portion 24 and a pin portion 25, which are arranged in this order in a direction away from the injection hole 102, as shown in
The large-diameter cylindrical portion 24 of the nozzle needle 2 is supported by the nozzle body 10 and the lower body 12 slidably and liquid-tightly.
The nozzle-needle sheet portion 21, the small-diameter cylindrical portion 22 and the pressure receiving portion 23 are arranged in the fuel accumulation room 101.
The pin portion 25 is arranged in a spring room 122 provided in the lower body 12. An end part of the pin portion 25 is located in a low pressure room 124, and an end surface of the end part of the pin portion 25 is in contact with a command piston 4.
The spring room 122 is connected to a fuel tank through a low pressure passage 123 provided in the lower body 12, a low-pressure fuel passage 140 provided in the orifice body 14, an actuator room 141 (low pressure portion) defined by the orifice body 14 and the upper body 16, and an outflow port 160 provided in the upper body 16.
The injection hole 102 is opened or closed by separation or contact of the nozzle-needle sheet portion 21 from or with the nozzle-body sheet portion 103. Pressure of the high-pressure fuel in the fuel accumulation room 101 is applied on the pressure receiving portion 23, and accordingly the nozzle needle 2 is urged in a valve opening direction to open the injection hole 102. The nozzle needle 2 is urged in a valve closing direction to close the injection hole 102 by a nozzle spring 3 disposed in the spring room 122.
The lower body 12 includes the low pressure room 124 and a control room 125 which are separated by the command piston 4 having a step cylindrical shape.
The low pressure room 124 is connected to the spring room 122 through a gap between a partition wall 126 of the lower body 12 and the pin portion 25.
The control room 125 is connected to the inflow port 120 through an introduction passage 127 provided in the lower body 12 and an introduction passage 142 provided in the orifice body 14. Thus, the high-pressure fuel is supplied from the common rail to the control room 125 through the introduction passages 127 and 142. The command piston 4 is subjected to a pressure of the high-pressure fuel introduced into the control room 125 and urges the nozzle needle 2 in the valve closing direction.
The control room 125 is connected to the actuator room 141 through a discharge passage 143 provided in the orifice body 14. The high-pressure fuel in the control room 125 is discharged to the actuator room 141 through the discharge passage 143. The discharge passage 143 is a cylindrical space having an even diameter.
As shown in
An electromagnetic control valve 5 is disposed in the actuator room 141. The control valve 5 includes a solenoid 51 that generates a magnetic attraction force upon energization, an armature 52 attracted by the magnetic attraction force, the valve body 53 that is joined to the armature 52 and opens or closes the discharge passage 143 in accordance with separation or contact of a flat valve-body sheet surface 530 of the valve body 53 from or with the orifice-body sheet surface 144, and a valve spring 54 urging the armature 52. The valve-body sheet surface 530 may be perpendicular to an axial direction of the discharge passage 143.
The armature 52 and the valve body 53 are attracted by the solenoid 51 in a direction away from the orifice-body sheet surface 144, and urged by the valve spring 54 toward the orifice-body sheet surface 144.
As shown in
Next, detailed configurations and processing procedures of the orifice body 14 will be described. First, as shown in
The chamfered part 6 is tapered. An inner circumferential surface 145a of the orifice-body recess portion 145 is also tapered.
Next, as shown in
An angle θ between the chamfered part 6 and the orifice-body sheet surface 144 is 30°. In other words, the chamfered part 6 is not a C-chamfered part, and is a tapered surface inclined at an angle other than 45° with respect to the orifice-body sheet surface 144. More specifically, the chamfered part 6 is a tapered surface inclined at an angle less than 45° with respect to the orifice-body sheet surface 144.
When a largest diameter of the chamfered part 6 is defined as D1, and a smallest diameter of the chambered part 6 is defined as D2, (D1−D2)/2 is defined as a chamfered dimension L. The chamfered dimension L may be set within a range from 0.005 to 0.04 millimeter.
After the orifice-body sheet surface 144 is formed by polishing, the coating layer 7 is formed on the orifice-body sheet surface 144 and the chamfered part 6, as shown in
Next, operations of the above-described fuel injection valve will be described below. When a drive current is supplied to the solenoid 51, the armature 52 and the valve body 53 are attracted. Accordingly, the valve body 53 is separated from the orifice-body sheet surface 144, and the discharge passage 143 is opened.
Therefore, the fuel in the control room 125 is returned to the fuel tank through the discharge passage 143 and the actuator room 141. As a result, a pressure in the control room 125 is reduced, and a force urging the nozzle needle 2 through the command piston 4 in the valve closing direction decreases. The nozzle needle 2 is driven in the valve opening direction by a pressure of the fuel acting on the pressure receiving portion 23. Accordingly, the nozzle-needle sheet portion 21 is separated from the nozzle-body sheet portion 103, and thereby the injection hole 102 is opened. The fuel is injected from the injection hole 102 into the combustion chamber of the internal combustion engine.
The chamfered part 6 is provided on the corner part of the orifice-body sheet surface 144 and the discharge passage 143. Thus, a flow of the fuel adjacent to the corner part in which the orifice-body sheet surface 144 intersects with the discharge passage 143 changes its flow direction gently as shown by an arrow A of
The discharged-fuel flow rates Q1 and Q2 are calculated under conditions where a pressure of the high-pressure fuel accumulated in the common rail is 200 MPa, and a valve lift that is a gap size between the valve body 53 and the orifice-body sheet surface 144 is 5 μm, 25 μm, and 45 μm. From the calculated discharged-fuel flow rates Q1 and Q2, the flow rate ratio Rq is obtained.
As is clear from
When the supply of the drive current to the solenoid 51 is stopped, the attraction force dissipates, and the armature 52 and the valve body 53 are urged by the valve spring 54. Accordingly, the valve body 53 contacts the orifice-body sheet surface 144, thereby closing the discharge passage 143.
Thus, the pressure in the control room 125 increases due to the high-pressure fuel supplied through the introduction passages 127 and 142, and a force urging the nozzle needle 2 through the command piston 4 in the valve closing direction becomes large. Hence, the nozzle needle 2 is driven in the valve closing direction, and the nozzle-needle sheet portion 21 contacts the nozzle-body sheet portion 103 and closes the injection hole 102. Accordingly, fuel injection is stopped.
The chamfered part 6 is provided in the corner part where the orifice-body sheet surface 144 intersects with the discharge passage 143. When the valve body 53 contacts the orifice-body sheet surface 144 upon stopping supply of the drive current to the solenoid 51, a foreign object may be stuck between the valve body 53 and the orifice-body sheet surface 144. However, even when the foreign object is stuck therebetween, the corner part where the orifice-body sheet surface 144 intersects with the discharge passage 143 is unlikely to be deformed toward the discharge passage 143 because of the chamfered part 6. Accordingly, a crack is unlikely to be generated on the corner part.
As described above, according to the present embodiment, since the chamfered part 6 is provided in the corner part where the orifice-body sheet surface 144 intersects with the discharge passage 143, generation of cracks caused by the foreign objects can be limited, and the fluid abrasive action force can be reduced.
In the above-described embodiment, the chamfered part 6 is constituted by a single tapered surface, but, as shown in a first modification of
In the above-described embodiment, the diameter of the discharge passage 143 is constant along the axial direction of the discharge passage 143, but, as shown in a second modification of
In the above-described embodiment, the inner circumferential surface 145a of the orifice-body recess portion 145 is tapered, but, as shown in a third modification of
Accordingly, a processing accuracy in inner diameter D3 of the orifice-body recess portion 145 can be improved, and a variation in area of the orifice-body sheet surface 144 can be reduced.
A second embodiment will be described referring to
As shown in
According to the present embodiment, similar effects to the first embodiment can be obtained.
A third embodiment will be described referring to
As shown in
The discharge passage 143 includes a counterbore part 143a on an outlet end, and a small-diameter discharge path 143b that is smaller than the counterbore part 143a in diameter.
According to the present embodiment, similar effects to the first embodiment can be obtained.
According to the third embodiment, the cross-sectional shape of the chamfered part 6 arcs, but the chamfered part 6 may have a curved shape other than the arc shape in cross-sectional surface along the axial direction of the discharge passage 143. More specifically, when a dimension of the chamfered part 6 having the curved cross-sectional shape in a radial direction of the discharge passage 143 is defined as a radial chamfered dimension L1, and a dimension of the chamfered part 6 in the axial direction of the discharge passage 143 is defined as an axial chamfered dimension L2, the radial chamfered dimension L1 is different from the axial chamfered dimension L2. Further, the radial chamfered dimension L1 may be larger than or equal to 0.005 millimeter. The radial chamfered dimension L1 may be set within a range from 0.005 to 0.04 millimeter.
The present disclosure is not limited to the above-described embodiments, and can be modified arbitrarily within a scope of the present disclosure.
The above-described embodiments are not unrelated to each other, and can be combined with each other unless the combination of embodiments is obviously impossible.
In the above-described embodiments, an element of each embodiment is not necessarily required unless the element is clearly described as particularly essential or the element is essential in principle.
In the above-described embodiments, when a specific number, such as value, amount, or range, of the element is mentioned, a number of the element is not limited to the specific number unless the number is clearly described as particularly essential or the number is limited to the specific number in principle.
In the above-described embodiments, when a shape or position of the element is mentioned, the shape or position of the element is not limited unless the shape or position is clearly described as particularly essential or the shape or position is essential in principle.
Additional advantages and modifications will readily occur to those skilled in the art. The disclosure in its broader terms is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-133663 | Jul 2015 | JP | national |
