Patent Application
20190003436
The present invention relates to a fuel injection device, and particularly to a fuel injection device used for an internal combustion engine.
In a fuel injection device that injects fuel to an internal combustion engine, PTL 1 is known as an invention for improving controllability of a fuel spray shape. PTL 1 describes a fuel injection device including a valve element, a plurality of fuel passages formed around the valve element, a plurality of swirl passages parallel to a direction perpendicular to the valve element, and a valve element guide hole to guide the valve element.
PTL 1: JP H10-331739 A
In a fuel injection device, in order to improve combustion stability of an internal combustion engine, it is required to reduce variations in a flow rate for each injection of the fuel injection device. When a radial force acting on the valve element at a time of valve opening is not stable, the valve element moves in an unspecified direction with a slight gap existing between the valve element and the valve element guide hole. Therefore, a flow of fuel flowing into an injection hole may vary every time the fuel injection device injects, causing variations in an injection flow rate.
In view of the problem above, it is an object of the present invention to provide a fuel injection device in which variations in an injection flow rate for each injection is suppressed and the injection amount is stabilized.
In order to achieve the above object, the fuel injection device according to the present invention is formed with a guide member to generate a pressure difference in a specific radial direction with respect to the valve element at a time of valve opening. Specifically, in the fuel injection device including: a valve element that is seated on or unseated from a valve seat; a plurality of guide parts that slidably guide the valve element; and a flow path sandwiched between the guide parts in a circumferential direction, one guide part among the plurality of guide parts is formed to have a longer circumferential length than that of other guide parts.
According to a configuration of the present invention, it is possible to provide a fuel injection device in which variations in an injection flow rate for each injection is suppressed and the injection amount is stabilized.
Hereinafter, examples of a fuel injection device according to the present invention will be described with reference to the drawings. Same elements are denoted by same reference numerals in each figure, and redundant explanations are omitted. Note that the present invention is not limited to the examples described below, and various modifications may be included. For example, the examples described below are illustrated in detail to facilitate description of the present invention for easy understanding, and are not necessarily limited to the examples that include all the configurations. Additionally, a part of a configuration of an example may be replaced with a configuration of another example, and a configuration of an example may be added with a configuration of another example. Moreover, a part of a configuration of each example may be deleted, replaced, or added with another configuration.
A configuration of a fuel injection device 100 according to Example 1 will be described with reference to
The fuel injection device 100 has a fuel supply part 200 that supplies fuel, a nozzle part 300, and an electromagnetic drive part 400. The nozzle part 300 is provided with a valve part 300a that allows and interrupts a distribution of fuel, at a tip portion. The electromagnetic drive part 400 drives the valve part 300a. In this example, the fuel supply part 200 is disposed at an upper end side in the figure, and the nozzle part 300 is disposed at a lower end side in the figure. The electromagnetic drive part 400 is disposed between the fuel supply part 200 and the nozzle part 300. That is, the fuel supply part 200, the electromagnetic drive part 400, and the nozzle part 300 are arranged in this order along a direction of the center axis 100a. Hereinafter, description will be given while referring a side disposed with the fuel supply part 200 with respect to the nozzle part 300 as an upstream side, and a side disposed with the nozzle part 300 side with respect to the fuel supply part 200 as a downstream side, according to the fuel flow direction. Note that the fuel supply part 200, the valve part 300a, the nozzle part 300, and the electromagnetic drive part 400 indicate corresponding portions with respect to the cross section shown in
In the fuel supply part 200, a fuel pipe (not shown) is connected to the upstream side of the fuel supply part 200. The nozzle part 300 is inserted into a mounting hole (insertion hole) formed in an intake pipe (not shown) or a combustion-chamber forming member (cylinder block, cylinder head, or the like) of the internal combustion engine. The electromagnetic fuel injection device 100 receives fuel from the fuel pipe through the fuel supply part 200, and injects fuel from a tip portion of the nozzle part 300 into the intake pipe or the combustion chamber. Inside the fuel injection device 100, a fuel passage 101 (101a to 101f) is formed such that the fuel flows substantially along the center axis 100a direction of the electromagnetic fuel injection device 100 from the upstream side of the fuel supply part 200 to the downstream side of the nozzle part 300.
In the following description, both end portions in a direction along the center axis 100a of the fuel injection device 100 will be described with an end portion side on the upstream side as a base end side while referring an end portion side on the downstream side as a tip end side. An end portion on the base end side of the fuel supply part 200 is a base end portion, and an end portion on a tip end side of the nozzle part 300 is a tip portion. In the following description, “upper” or “lower” will be described with reference to the vertical direction in
The fuel supply part 200 is configured to include a fuel pipe 201. At an upper end portion of the fuel pipe 201, a fuel supply port 201a is provided. On an inner peripheral side of the fuel pipe 201, the fuel passage 101a is formed. The fuel passage 101a penetrates the fuel pipe 201 along the center axis 100a. A fixed iron core 401 to be described later is joined to a lower end portion of the fuel pipe 201.
On an outer peripheral side of the upper end portion of the fuel pipe 201, an O-ring 202 and a backup ring 203 are provided. The O-ring 202 functions as a seal to prevent fuel leakage when the fuel supply port 201a is mounted to the fuel pipe. The backup ring 203 is for backing up the O-ring 202. The backup ring 203 may be formed with a plurality of ring-shaped members laminated. On the inner peripheral side of the fuel supply port 201a, there is disposed a filter 204 that filters foreign matter mixed in the fuel.
The nozzle part 300 is configured to include the valve part 300a and a nozzle body 300b. The valve part 300a is formed at a lower end portion of the nozzle body 300b. The nozzle body 300b is a hollow cylindrical body. On an inner peripheral side of the nozzle body 300b, the fuel passage 101f is formed. The fuel passage 101f is formed on the upstream side of the valve part 300a. A tip seal 103 is provided on an outer peripheral surface of the nozzle body 300b. The tip seal 103 is provided to maintain airtightness at a time of mounting on an internal combustion engine.
The valve part 300a includes an injection hole forming member 301, a guide part 302, and a valve element 303. The valve element 303 is provided on a tip end side of a plunger rod 102.
The injection hole forming member 301 is inserted into a recess inner peripheral surface 300ba formed at the tip portion of the nozzle body 300b. An outer periphery of a tip end face of the injection hole forming member 301 and an inner periphery of a tip end face of the nozzle body 300b are fixed by welding. This causes the fuel to be sealed between the injection hole forming member 301 and the nozzle body 300b. A configuration of the valve part 300a will be described in detail with reference to
The electromagnetic drive part 400 has the fixed iron core 401, a coil 402, a housing 403, a movable iron core 404, a first spring member 405, a third spring member 406, a second spring member 407, a plunger cap 410, and an intermediate member 414. The fixed iron core 401 is also referred to as a fixed core. The movable iron core 404 is also referred to as a movable core, a movable element, or an armature. A configuration of the electromagnetic drive part 400 will be described in detail with reference to
The fixed iron core 401 has the fuel passage 101c in a center portion, and a joint part 401a with the fuel pipe 201. A spring force adjusting member 106 abutting against the first spring member 405 is disposed on an inner peripheral side of the fixed iron core 401. In addition, the nozzle body 300b has a movable iron core receiving part 300e below the movable iron core 404.
In this example, a seat surface 304 and an injection hole opening surface 304a are flush with each other. However, an embodiment is not limited to this. For example, the injection hole opening surface 304a may be on the downstream side of the seat surface 304. This enables change of a length of the fuel injection hole 305, and improves flexibility in designing the injection hole forming portion 301.
The guide part 302 is on an inner peripheral side of the injection hole forming member 301 and has a slight gap with a tip end side (lower end side) of the plunger rod 102 while forming a guide surface, and serves as a guide when the plunger rod 102 moves in the direction along the center axis 100a (direction of the opening and closing valve). Although the tip of the valve element 303 has a tapered shape, a spherical shape may be used.
The fixed iron core 401 is fitted and joined to the inner circumference of a large diameter part 300c of the nozzle body 300b, with an outer peripheral surface 401b. The fixed iron core 401 is fitted and joined to an outer-peripheral-side fixed iron core 401d, with an outer peripheral surface 401e having a diameter larger than the outer peripheral surface 401b.
The coil 402 is wound around an outer peripheral side of the fixed iron core 401 and the large diameter part 300c of a cylindrical member. In a state of being wound around a bobbin, the coil 402 is assembled to the outer peripheral side of the fixed iron core 401 and the large diameter part 300b of the cylindrical member. A resin material is molded around its periphery. By the resin material used for this molding, a connector 105 having a terminal 104 drawn out from the coil 402 is integrally molded.
The housing 403 is provided so as to surround an outer peripheral side of the coil 402. The housing 403 constitutes an outer periphery of the fuel injection device 100. The housing 403 is connected to an outer peripheral surface 401f of the outer-peripheral-side fixed iron core 401d on an upper-end-side inner peripheral surface 403a.
The movable iron core 404 is disposed on a lower end face 401g side of the fixed iron core 401. An upper end face 404c of the movable iron core 404 is opposed to the lower end face 401g of the fixed iron core 401 via a gap g2. An outer peripheral surface of the movable iron core 404 is opposed to the inner peripheral surface of the large diameter part 300c of the nozzle body 300b via a slight gap. The movable iron core 404 is provided inside the large diameter part 300c of the cylindrical member so as to be movable in the direction along the center axis 100a. When a current is applied to the coil 402, a magnetic path is formed such that a magnetic flux circulates around the fixed iron core 401, the movable iron core 404, the large diameter part 300c of the cylindrical member, and the housing 403. Magnetic attraction force is generated by the magnetic flux flowing between the lower end face 401g of the fixed iron core 401 and the upper end face 404c of the movable iron core 404. The movable iron core 404 is attracted toward the fixed iron core 401 by the magnetic attraction force.
In a central portion of the movable iron core 404, a recessed part 404b recessed from the upper end face 404c side to the lower end face 404a side is formed. Providing the recessed part 404b of the movable iron core 404 allows the intermediate member 414 to be arranged further downward, so that a vertical length of the plunger rod 102 can be shortened. In this example, such a configuration is adopted in order to improve accuracy of the plunger rod 102. However, it is also possible to form one plane with the upper end face 404c without providing the recessed part 404b.
The movable iron core 404 is formed with a fuel passage hole 404d and a through hole 404e that penetrate in the direction along the center axis 100a. The fuel passage hole 404d penetrates from the upper end face 404c to the lower end face 404a of the movable iron core 404, and also penetrates from a bottom surface 404b′ of the recessed part 404b to the lower end face 404a. The fuel passage hole 404d functions as the fuel passage 101d. The through hole 404e penetrates from the bottom surface 404b′ of the recessed part 404b to the lower end face 404a. The through hole 404e is a through hole passing through the center axis 100a. The plunger rod 102 is passed through the through hole 404e.
On the downstream side of the movable iron core 404, the fuel passage 101e is formed. The lower end face 404a of the movable iron core 404 is opposed to the movable iron core receiving part 300e of the nozzle body 300b. The movable iron core receiving part 300e is formed on an outer peripheral side of a diameter 311a. In the nozzle body 300b, a hollow portion is formed on an inner peripheral side of the diameter 311a, as illustrated.
The movable iron core receiving part 300e is formed integrally with the nozzle body 300b. Therefore, a gap g3 between a lower surface 404a of the movable iron core 404 and the movable iron core receiving part 300e can be determined by processing of the nozzle body 300b. This enables improvement of the performance with a simple method without adding a component or the like.
The first spring member 405, the third spring member 406, and the second spring member 407 are arranged in this order from the upstream side to the downstream side. A lower end portion of the first spring member 405 urges the plunger rod 102 downward via the plunger cap 410. A lower end portion of the third spring member 406 abuts against an upper surface 414c of the intermediate member 414, to urge the intermediate member 414 in a downward direction. A lower end portion of the second spring 407 abuts against a stepped portion 300d of the nozzle body 300b. An upper end portion of the second spring member 407 abuts against the lower surface 404a of the movable iron core 404, to urge the movable iron core 404 in an upward direction.
The plunger cap 410 is fitted to the tip on the upstream side of the plunger rod 102. The plunger rod 102 has a thick diameter part 102a. The plunger cap 410 has an upper spring bearing 410a and a lower spring bearing 410b. The upper spring bearing 410a of the plunger cap 410 abuts against the lower end portion of the first spring member 405. The lower spring bearing 410b of the plunger cap 410 abuts against an upper end portion of the third spring member 406. A lower end portion 410d of the plunger cap 410 is opposed to the upper surface 414c of the intermediate member 414.
The intermediate member 414 is a cylindrical member having a recessed part. An inner peripheral surface 414a of the recessed part abuts against an upper surface 102b of the thick diameter part 102a of the plunger rod 102. An outer peripheral surface 414b of the recessed part abuts against the bottom surface 404b′ of the recessed part 404b of the movable iron core 404. A gap g1 is formed between the lower surface 102c of the thick diameter part 102a of the plunger rod 102 and the bottom surface 404b′ of the recessed part 404b of the movable iron core 404. A height h of the thick diameter part 102a of the plunger rod 102 is represented by a height from the upper surface 102b to 102c of the thick diameter part 102a. The gap g1 is a length obtained by subtracting the height h of the thick diameter part 102a of the plunger rod 102 from the height 414h of the step of the recessed part of the intermediate member 414.
An outer diameter 414D of the intermediate member 414 is formed to be smaller than an inner diameter 401D of the fixed iron core 401. This configuration enables insertion of the plunger rod 102 in a state in which the intermediate member 414, the third spring member 406, and the plunger cap 410 are assembled in advance, through the inner diameter 401D of the fixed iron core 401. Since an assembling work can be performed after the gap g1 is determined by the step height 414h of the intermediate member and the height h of the thick diameter part of the plunger rod, it is possible to stably manage the gap g1 while facilitating the assembly. In this example, the outer diameter 414D of the intermediate member 414 is made smaller than the inner diameter 401D of the fixed iron core 401. However, it is only necessary that an outermost diameter of a member to be assembled in advance is small. For example, when an outer diameter of the plunger cap 410 is larger than the outer diameter 414D of the intermediate member 414, the outer diameter of the plunger cap 410 may be made smaller than the inner diameter 401D of the fixed iron core 401.
In a state in which the coil 402 is not energized, the plunger rod 102 abuts against the seat 304 with the urging force of the first spring member 405 and the third spring member 406 in the valve closing direction, against the urging force of the second spring member 407 in the valve opening direction. This state is called a valve-closed stationary state. In the valve-closed stationary state, the movable iron core 404 abuts against the outer peripheral surface 414b of the intermediate member 414.
In the valve-closed stationary state, the gap g1 is formed between the bottom surface 404b′ of the recessed part 404b of the movable iron core 404 and the lower surface 102c of the thick diameter part 102a of the plunger rod 102. The gap g2 is formed between the lower end face 401g of the fixed iron core 401 and the upper end face 404c of the movable iron core 404. A relationship between the gaps g1 and g2 is g2>g1. The gap g3 is formed between the lower surface 404a of the movable iron core 404 and the movable iron core receiving part 300e of the nozzle body 300b.
After energization to the coil 402 (P1 in
After the movable iron core 404 abuts against the lower surface 102c of the thick diameter part 102a of the plunger rod 102 at the timing of t1, the plunger rod 102 is pulled up by an impact force from the movable iron core 404. The plunger rod 102 moves away from the seat 304 and starts a valve opening operation. A gap is formed between the seat and the valve element 303 formed at a tip portion of the plunger rod 102, and the fuel passage is opened. Since the plunger rod 102 starts to open the valve by receiving the impact force, the plunger rod 102 rises sharply (3A). Thereafter, the movable iron core 404 is displaced by g2-g1 and abuts against the lower surface 401g of the fixed iron core 401 at a timing of t2.
After the movable iron core 404 abuts against the lower surface 401g of the fixed iron core 401 at the timing of t2, the plunger rod 102 is further displaced upward (3B). Whereas, the movable iron core 404 is displaced downward (3B′) by reaction of collision with the lower surface 401g of the fixed iron core 401. Thereafter, the movable iron core 404 comes into contact with the fixed iron core 401 again with the magnetic attraction force, and displacement is stabilized at g2-g1 (3C).
At a timing of t3, when the energization to the coil 402 is interrupted (P2), the magnetic force starts to disappear. Then, the valve closing operation is started by the urging force of the spring moving in the downward direction.
After the displacement of the plunger rod 102 becomes zero at a timing of t4, the plunger rod abuts against the seat 304, to complete the valve closing (102D2). The movable iron core 404 moves to the initial position g1 after closing of the valve (404D2). The movable iron core 404 is further displaced in the downward direction by inertia, and then stops at the position g1 (404D3).
As shown in
Returning to
As a characteristic configuration of the fuel injection device 100 according to this example, the guide part 302a has a longer circumferential length than that of the other guide parts 302b and 302c. That is, the flow paths 306a to 306c are arranged such that an interval between the flow path 306b and the flow path 306c is larger than an interval between other flow paths. It can be also said that individual centers of the plurality of flow paths 306a to 306c are arranged unevenly in the circumferential direction.
At a time of the valve opening operation, fuel flows through the guide part 302 and the flow path 306 by a side of the valve element 303. A flow velocity of the fuel flowing by the side of the valve element 303 causes a fluid force acting in the radial direction on the valve element 303. When the flow velocity flowing by the side of the valve element 303 is high, a pressure loss of the fuel flowing by the side increases. This causes a pressure difference in the radial direction, and generates a force so as to draw the valve element 303.
As a comparative example, a case will be described in which a plurality of flow paths and guide parts formed by the side of the valve element are arranged symmetrically in the circumferential direction. In such a configuration, a fluid force acting on the valve element is substantially equilibrium. Then, a movement of the valve element in the direction orthogonal to a direction of the valve opening operation may not be kept constant, and the valve element may be displaced in a different direction at each injection of the fuel injection device. Since the seat in contact with the valve element is typically formed by a conical surface, the gap between the valve element and the seat varies also by a radial movement of the valve element. The gap between the valve element and the seat is formed on the upstream side of the fuel injection hole, and is related to the flow rate of the fuel flowing into the fuel injection hole. Therefore, it is important that the gap becomes constant for each injection. If the displacement of the valve element is unstable, the flow rate of the fuel flowing into the fuel injection hole varies for each injection.
In a case of this example, among the plurality of guide parts 302, the guide part 302a disposed between the flow path 306b and the flow path 306c is formed to be the longest. The fluid force generated between the guide part 302a and the valve element 303 becomes relatively large. Therefore, the valve element 303 is drawn in the right direction in
Specifically, in the fuel injection device 100 of this example, the guide part 302a and the flow path 306a are arranged diametrically opposed to each other with the central axis 100a of the fuel injection device 100 interposed in between. In addition, the flow path 306b and the flow path 306c are arranged so as to sandwich the valve element 303 along a direction orthogonal to the direction in which the guide part 302a and the flow path 306a are disposed (a direction parallel to the symmetric plane 501 of spray).
As described above, in the fuel injection device 100 of this example, the circumferential arrangement of the flow path 306 formed by the side of the valve element 303 is intentionally uneven. The force acting on the valve element 303 acts in a specific direction during the valve opening operation. This prevents variations in the fluid gap formed between the seat 304 and the valve element 303 for each valve opening operation. Since the flow of the fuel flowing into the fuel injection hole does not vary for each injection, variations in an injection flow rate can be reduced.
In this example, as described above, one of major objectives is to reduce variations in an injection flow rate at a time of valve opening operation. In the fuel injection device according to this example, as described in
In this example, since the circumferential interval between the flow paths 306b and 306c is formed to be wider than other intervals, it is easier for fuel to flow on the flow path 306a side (the left side in the figure) than the guide part 302a side (the right side in the figure). That is, the fuel is more likely to flow toward the fuel injection hole inlet 305a than the fuel injection hole inlet 305d.
As shown in
In this way, unevenly disposing the guide part 302 causes the fuel to easily flow into the fuel injection hole inlet 305a. However, by bringing the boring direction from the fuel injection hole inlet 305a to the fuel injection hole outlet 305a′ close to the central axis 100a of the fuel injection device 100, the delamination area can be suppressed to be small, and variations in the fuel injection amount can be reduced. Therefore, it is possible to further improve the reduction effect on variations in the injection amount.
In this example, hole diameters of the fuel injection holes 305 are all the same, but the hole diameters of the fuel injection holes 305 may be individually changed. For example, the hole diameter on the fuel injection hole 305a side having a relatively large fuel flow rate can be made larger than the hole diameter on the fuel injection hole 305d side. Even in this case, the delamination area can be made relatively small, and variations in the flow rate of the fuel injection device as a whole can be reduced.
In this example, the circumferential lengths of the guide parts 302b and 302c are made equal. However, as long as the length of the guide part 302a is the longest, there is no particular difference in the operational effect even if there is a difference in the lengths of the guide parts 302b and 302c.
A configuration of a fuel injection device 100 according to Example 2 will be described with reference to
Since a circumferential length of a guide part 2302a is longer than that of other guide parts 2302b and 2302c, an amount of fuel flowing into the fuel injection hole 2305a formed on an opposite side to the guide part 2302a is relatively large. On the contrary, no fuel injection hole is provided on the guide part 2302a side.
An angle θ1 formed by a central axis 100a of a fuel injection device 100 and an injection hole axis connecting a center of the fuel injection hole inlet 2305a and a center of the fuel injection hole outlet 2305a′ is formed to be smaller than an angle of other fuel injection holes.
Even in such an example, as in Example 1, it is possible to reduce variations in the fuel injection amount for each injection.
A configuration of a fuel injection device 100 according to Example 3 will be described with reference to
A configuration of a fuel injection device according to Example 4 will be described with reference to
Even in this case, a guide part 4302a is formed to have a longer circumferential length than that of other guide parts 4302b and 4302c. In this example as well, as in Example 1, a fluid force generated in the guide part 4302a becomes large, and a valve element 303 performs a valve opening operation while moving to the guide part 4302a side (the right direction in the figure). This allows a fluid gap formed between a seat 304 and the valve element 303 to be constant for each valve operation, enabling reduction of variations in the injection amount of the fuel injection device 100 for each drive.
In this example, fuel is more likely to flow into the fuel injection holes 4305a and 4305g than a fuel injection hole 4305d. Since the fuel injection holes 4305a and 4305g are provided, not only the reduction in variations in the injection amount is improved, but also spray shape controllability can also be improved.
An example different from the above will be further described with reference to
Each of Examples 1 to 4 described above is characterized in that one guide part among the plurality of guide parts is formed to have a longer circumferential length than that of other guide parts. However, such a configuration is one example as a configuration for directing a radial force acting on a valve element in a specific direction. In each of the above-described examples, the fuel injection device is configured such that a fluid force acts around the valve element with fuel, and a pressure difference around the valve element acts to a specific direction. Various modifications are possible without departing from such a technical concept, and this example is one example thereof.
By forming a flow path having a minute cross-sectional area in a partial region around a valve element 303 as in this example, it is also possible to apply a force to the valve element 303 toward the right direction in the figure. According to this example, it is possible to reduce variations in the injection amount as the fuel injection device while supplying a minimum necessary amount of fuel to a fuel injection hole 5305d as well. In addition, abrasion between the valve element and the guide part can be suppressed. Further, it is also conceivable that a plurality of flow paths are arranged at unequal intervals in a circumferential direction by a side of the valve element, as a modification.
In each of Examples 1 to 5 described above, the guide part and the flow path are formed integrally with the injection hole forming member 305 on which the fuel injection hole is formed. In the injection hole forming member 305, the plurality of fuel injection holes are formed circumferentially. However, the invention in the present application is not limited to such an embodiment. For example, there may be separately formed a guide part to regulate a radial movement of the valve element 303, a valve seat on which the valve element 303 is seated, and the injection hole forming member formed with the fuel injection hole. Alternatively, the present invention can also be applied to a fuel injection device in which fuel flows downstream from a single fuel distribution opening formed at an apex of a conical surface constituting the valve seat.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-003172 | Jan 2016 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/083629 | 11/14/2016 | WO | 00 |
