This application is the U.S. national phase of International Application No. PCT/JP2014/003967 filed Jul. 29, 2014 which designated the U.S. and claims priority to Japanese Patent Application No. 2013-161594 filed on Aug. 2, 2013, the entire contents of each of which are hereby incorporated by reference.
The present disclosure relates to a fuel injector that injects fuel toward the inside of a combustion chamber of an internal combustion engine.
In the fuel injector disclosed in Patent Literatures 1 and 2, a plurality of injection ports which inject fuel toward the inside of the combustion chamber are formed. In the fuel injector of Patent Literature 2 in particular, the inside diameter of one injection port is different from the inside diameter of the other injection port. According to the configuration in which the inside diameter of the injection ports is made to differ from each other thus, the shape of the spray injected from the fuel injector becomes easily suitable to the shape of the combustion chamber of the internal combustion engine.
However, when the inside diameter of one injection port is different from the inside diameter of the other injection hole as the fuel injector disclosed in Patent Literature 2, the property of the spray injected from each injection hole also possibly differs from each other. Therefore, the particle diameter of the fuel injected from each injection hole possibly differs from each other, or the spreading style of the spray injected from each injection hole possibly differs from each other.
It is an object of the present disclosure to provide a fuel injector that can make the property of the spray injected from each injection hole approximate to each other even when the inside diameter of the injection holes formed in the fuel injector may differ from each other.
[Patent Literature 1] Japanese Patent No. 5,033,735
[Patent Literature 2] JP-2008-202483A
According to a first aspect of the present disclosure, a plurality of injection holes formed in a fuel injector include a first injection hole and a second injection hole having the reference inside diameter different from each other. A value obtained by dividing the flow channel length of the first injection hole by the reference inside diameter of the first injection hole becomes equal to a value obtained by dividing the flow channel length of the second injection hole by the reference inside diameter of the second injection hole.
The present inventors found out that the atomizing property of the spray in the fuel injector was related to the ratio of the flow channel length and the reference inside diameter of the injection hole. Therefore, in the first aspect, the value obtained by dividing the flow channel length by the reference inside diameter is the same as in the first injection hole and the second injection hole. Accordingly, even when the reference inside diameter in these injection holes may differ from each other, the atomizing properties of the first injection hole and the second injection hole possibly approximate to each other. The fuel injector can reduce the dispersion of the particle diameter with respect to the spray injected from each injection hole also while forming the spray shape that is suitable to the combustion chamber of the internal combustion engine.
Also, the present inventors found out the relationship between the change rate of the spray injected from the injection hole and the value obtained by dividing the flow channel length by the reference inside diameter. According to a second aspect of the present disclosure, the first injection hole and the second injection hole have a tubular hole shape that extends while maintaining each reference inside diameter, and both of the value obtained by dividing the flow channel length of the first injection hole by the reference inside diameter of the first injection hole and the value obtained by dividing the flow channel length of the second injection hole by the reference inside diameter of the second injection hole are 1.45 or more.
According to a third aspect of the present disclosure, the first injection hole and the second injection hole have a tapered hole shape that expands the diameter from each reference inside diameter starting from the fuel upstream side toward the fuel downstream side, and both of the value obtained by dividing the flow channel length of the first injection hole by the reference inside diameter of the first injection hole and the value obtained by dividing the flow channel length of the second injection hole by the reference inside diameter of the second injection hole are 2.0 or more.
When the flow channel length with respect to the reference inside diameter has been secured, the rectifying action occurs in the fuel that flows inside the injection hole. Therefore, the spray injected from the injection hole is stably formed in the center line direction of the injection hole. By securing the predetermined value described above or more of the value obtained by dividing the flow channel length by the reference inside diameter, even when the reference inside diameter of the first injection hole and the second injection hole may differ from each other, the change rate of the spray injected from these injection holes becomes a value that is approximate to each other and stable. Therefore, the fuel injector can stably form the spray of the shape that is suitable to the combustion chamber of the internal combustion engine.
Also, the present inventors found out that there was a correlation between the length of the spray (hereinafter referred to as “spray length”) injected from the injection hole whose reference inside diameter was maintained and the value obtained by dividing the flow channel length by the reference inside diameter. Therefore, according to a fourth aspect of the present disclosure, both of the value obtained by dividing the flow channel length of the first injection hole by the reference inside diameter of the first injection hole and the value obtained by dividing the flow channel length of the second injection hole by the reference inside diameter of the second injection hole are made 1.85 or less.
By stipulating the upper limit of the flow channel length with respect to the reference inside diameter, the event that the fuel flowing inside the injection hole is rectified excessively can be avoided. By setting the upper limit of the value obtained by dividing the flow channel length by the reference inside diameter, even when the reference inside diameters of the first injection hole and the second injection hole may differ from each other, the spray length of the fuel injected from these injection holes can be suppressed for the both. Therefore, the fuel injector can form the spray of the shape more suitable to the combustion chamber of the internal combustion engine.
The object described above, other objects, the features and advantages with respect to the present disclosure will be clarified more by detailed description below while referring to the attached drawings.
Below, embodiments will be explained based on the drawings. By giving a same reference sign to a corresponding configuration element in each embodiment, there is a case of omitting duplicated explanation. When only a portion of the configuration is explained in each embodiment, with respect to the other portion of the configuration in question, the configuration of other embodiment explained previously can be applied. Also, not only the combination of the configurations explicitly shown in the explanation of each embodiment, the configurations of embodiments can be combined with each other partially even it is not explicitly shown unless a problem occurs particularly in the combination. Further, the combination not explicitly shown of the configurations described in embodiments and modifications also is to be understood to have been disclosed by the explanation below.
A fuel injector 10 according to a first embodiment shown in
The fuel injector 10 includes a valve body 11, a fixed core 20, a movable core 30, a valve member 40, an elastic member 50, and a drive unit 60.
The valve body 11 is formed of a core housing 12, an inlet member 13, a nozzle holder 14, a nozzle body 15, and the like. The core housing 12 is formed into a cylindrical shape, and includes a first magnetic section 12a, a non-magnetic section 12b, and a second magnetic section 12c in this order from one end side to the other end side of the axial direction. The respective magnetic sections 12a, 12c formed of a magnetic material and the non-magnetic section 12b formed of a non-magnetic material are joined with each other by laser welding and the like. The non-magnetic section 12b prevents the magnetic flux from being short-circuited between the first magnetic section 12a and the second magnetic section 12c.
To one end of the first magnetic section 12a, the inlet member 13 of a cylindrical shape is fixed. The inlet member 13 forms a fuel inlet 13a to which the fuel is supplied from a fuel pump (not illustrated). A fuel filter 16 is fixed to the inner peripheral side of the inlet member 13 in order to filter the supply fuel to the fuel inlet 13a and to introduce the supply fuel into the core housing 12 of the downstream side.
To one end of the first magnetic section 12a, the nozzle body 15 is fixed through the nozzle holder 14 that is formed into a cylindrical shape by a magnetic material. The nozzle body 15 is formed into a bottomed cylindrical shape, and forms a fuel passage 17 on the inner peripheral side jointly with the core housing 12 and the nozzle holder 14. As shown in
The valve seat section 150 forms a valve seat surface 151 by the inner peripheral surface of a tapered surface shape that reduces the diameter at a constant diameter reduction rate toward the fuel downstream side. The sack section 152 is formed on the fuel downstream side of the valve seat section 150. The sack section 152 forms a recess 153 that opens toward the fuel passage 17. To the inner surface of a sack chamber 154, injection holes 155 that communicate with the sack chamber 154 open. As shown in
As shown in
The movable core 30 is formed into a stepped cylindrical shape by a magnetic material, is disposed on the inner peripheral side of the core housing 12 coaxially, and opposes the fixed core 20 of the fuel upstream side in the axial direction. The movable core 30 is capable of executing precise reciprocating motion to both sides in the axial direction by being guided by the inner peripheral wall of the non-magnetic section 12b out of the core housing 12. In the movable core 30, a first through hole 30a that penetrates the center part in the radial direction thereof in the axial direction and a second through hole 30b that penetrates the middle part in the axial direction in the radial direction and communicates with the first through hole 30a are arranged. The fuel having flowed out from the through hole 20a of the fixed core 20 flows in to the first through hole 30a of the movable core 30, and flows from the second through hole 30b to the fuel passage 17 of the inside of the core housing 12.
The valve member 40 is formed into a needle shape with the circular cross section by a non-magnetic material. The elements 12, 14, 15 out of the body member 11 are disposed inside the fuel passage 17 coaxially. One end of the valve member 40 is fixed to the inner peripheral surface of the first through hole 30a of the movable core 30 coaxially. Also, as shown in
As shown in
The drive unit 60 is formed of a coil 61, a resin bobbin 62, a magnetic yoke 63, a connector 64, and the like. The coil 61 is formed by winding a metal wire around the resin bobbin 62, and the magnetic yoke is disposed on the outer peripheral side thereof. The coil 61 is fixed coaxially to the outer peripheral surfaces of the non-magnetic section 12b and the second magnetic section 12c which become the outer peripheral side of the fixed core 20 out of the core housing 12 through the resin bobbin 62. The coil 61 is electrically connected to the external control circuit (not illustrated) through a terminal 64a arranged in the connector 64, and is configured to be energization-controlled by the control circuit.
Here, when the coil 61 is magnetized by energization, the magnetic flux flows in a magnetic circuit that is formed jointly by the magnetic yoke 63, the nozzle holder 14, the first magnetic section 12a, the movable core 30, the fixed core 20, and the second magnetic section 12c. As a result, a magnetic attraction force that attracts the movable core 30 toward the fixed core 20 of the fuel upstream side is generated between the movable core 30 and the fixed core 20. On the other hand, when the coil is demagnetized by stop of energization, the magnetic flux does not flow in the magnetic circuit described above, and the magnetic attraction force is eliminated between the movable core 30 and the fixed core 20.
In the valve opening operation of the fuel injector 10, the magnetic attraction force is applied to the movable core 30 by start of energization to the coil 61. Then, the movable core 30 moves to the fixed core 20 side along with the valve member 40 resisting the restoring force of the elastic member 50, thereby abuts upon the fixed core 20, and stops. As a result, because the abutting section 41 becomes a state of departing from the valve seat surface 151, the fuel comes to be injected from the respective injection holes 155.
In the valve closing operation of the fuel injector 10 after the valve opening operation, the magnetic attraction force applied to the movable core 30 is eliminated by stopping energization of the coil 61. The movable core 30 moves to the energizing side along with the valve member 40 by the restoring force of the elastic member 50, and makes the valve member 40 abut upon the valve seat surface 151 and stop. As a result, the abutting section 41 becomes a state of sitting on the valve seat surface 151, and fuel injection from the respective injection holes 155 stops.
Next, the configuration of the vicinity of the recess 153 shown in
In the bottom surface of the bottom wall 160, a center surface section 161 and a tapered surface section 162 are formed. Also, on the outer peripheral side of the bottom surface, a connecting surface 168 is formed. The center surface section 161 is a flat surface formed into a complete round shape, and is positioned coaxially with the axis 18. The tapered surface section 162 is formed into a tapered surface shape that reduces the diameter with a constant diameter reduction rate toward the center surface section 161 that becomes the fuel downstream side out of the axial direction. The connecting surface 168 is formed into a recessed curved surface shape that increases the diameter reduction rate toward the fuel downstream side, and connects the outer peripheral side of the tapered surface section 162 and the inner peripheral side of the valve seat surface 151 with each other.
In the bottom wall 160, the injection holes 155 including a first injection hole 155a and a second injection hole 155b are formed. Both of the first injection hole 155a and the second injection hole 155b are formed into a cylindrical hole shape. The first injection hole 155a and the second injection hole 155b extend inside the bottom wall 160 with an attitude making the respective axes (hereinafter referred to as “injection hole axis”) cross the tapered surface section 162. Respective injection hole axes 159a and 159b cross with the tapered surface section 162 diagonally, and incline toward the outer periphery of the nozzle body 15 as they go from the inlet side opening 156 toward the outlet side opening 157. The inside diameter that is maintained substantially constant in the first injection hole 155a shown in
The flow channel length of the first injection hole 155a is expressed as Ln1, and the flow channel length of the second injection hole 155b is expressed as Ln2. In the present embodiment, the flow channel length Ln1 of the first injection hole 155a is longer than the flow channel length Ln2 of the second injection hole 155b. The value obtained by dividing the flow channel length Ln1 in the first injection hole 155a by the reference inside diameter Dn1 thereof (hereinafter referred to as “L/D value”) is equal to the L/D value obtained by dividing the flow channel length Ln2 in the second injection hole 155b by the reference inside diameter Dn2 thereof.
In order to achieve each shape of the first injection hole 155a and the second injection hole 155b described above, in the bottom wall 160, a first expanded diameter hole 164 and a second expanded diameter hole 165 are formed so as to continue to the respective injection holes 155a, 155b. The first expanded diameter hole 164 and the second expanded diameter hole 165 shown in
The first expanded diameter hole 164 of
The second expanded diameter hole 165 of
Next, respective L/D values of the first injection hole 155a and the second injection hole 155b will be explained in detail based on
As shown in the part (A) of
In addition, as shown in the part (B) of
Further, as shown in the part (C) of
In the first embodiment, the respective L/D values of the first injection hole 155a and the second injection hole 155b are equalized to approximately 1.65 that is the middle value of two boundary values described above (1.45, 1.85). Therefore, even if the reference inside diameters Dn1, Dn2 are different from each other, the atomizing property of the first injection hole 155a and the second injection hole 155b can approximate to each other. Accordingly, the fuel injector 10 can reduce the dispersion of the particle diameter with respect to the spray injected from the respective injection holes 155a, 155b also while forming the spray shape suitable to the combustion chamber of the internal combustion engine.
In addition, in the first embodiment, because both of the respective L/D values of the first injection hole 155a and the second injection hole 155b exceed 1.45, sufficient rectifying action can be caused in the fuel that flows inside the respective injection holes 155a, 155b. Therefore, the spray injected from the respective injection holes 155a, 155b is stably formed in the direction the respective injection hole axes 159a, 159b are directed. According to the above, the change rate of the spray injected from the respective injection holes 155a, 155b becomes a value that is approximate to each other and stable. Therefore, the fuel injector 10 can stably form the spray of the shape that is suitable to the combustion chamber of the internal combustion engine.
Also, according to the first embodiment, because both of the respective L/D values of the first injection hole 155a and the second injection hole 155b are 1.85 or less, the event that the fuel flowing inside the respective injection holes 155a, 155b is rectified excessively can be avoided. Therefore, both of the length of the spray injected from the respective injection holes 155a, 155b can be suppressed so that the spray does not adhere to the cylinder wall surface and the piston top face. Accordingly, the fuel injector 10 can form the spray that is more suitable to the combustion chamber of the internal combustion engine.
Also, according to the first embodiment, the difference of the respective flow channel lengths Ln1, Ln2 and the wall thickness of the bottom wall 160 is supplemented by the respective expanded diameter holes 164, 165. Therefore, the respective flow channel lengths Ln1, Ln2 can be stipulated so that the respective L/D values in the respective injection holes 155a, 155b are optimized even when the wall thickness of the bottom wall 160 is constant. As described above, the configuration of arranging the respective expanded diameter holes 164, 165 and adjusting the respective flow channel lengths Ln1, Ln2 is particularly suitable to the fuel injector 10 that optimizes the respective L/D values of the respective injection holes 155a, 155b.
In addition, according to the first embodiment, because the respective expanded diameter holes 164, 165 are formed on the fuel downstream side of the respective injection holes 155a, 155b, the event that the flow of the fuel that is going to flow in to the respective injection holes 155a, 155b is disrupted inside the respective expanded diameter holes 164, 165 can be avoided. Because the fuel inside the sack chamber 154 can be made to flow in smoothly to the respective injection holes 155a, 155b, the shape of the spray injected from these injection holes 155a, 155b can be stabilized more.
Furthermore, according to the first embodiment, because the respective expanded diameter holes 164, 165 are disposed coaxially with the respective injection holes 155a, 155b, the spray injected from the respective injection holes 155a, 155b can be formed without hitting the inner peripheral wall surface of the respective expanded diameter holes 164, 165. Therefore, the event that the shape of the spray is disrupted because the respective expanded diameter holes 164, 165 have been formed is avoided.
Also, in the first embodiment, the bottom wall 160 corresponds to “injection hole wall”.
A second embodiment of the present invention shown in
On the other hand, the bottom wall 260 has not the configuration corresponding to the first expanded diameter hole 164 and the second expanded diameter hole 165 of the first embodiment (refer to
More specifically, as shown in
In the second embodiment also, by equalizing the respective L/D values of the first injection hole 255a and the second injection hole 255b within a predetermined range, the effect similar to that of the first embodiment comes to be exerted. Therefore, even when reference inside diameters Dn201, Dn202 of the respective injection holes 255a, 255b may be different from each other, the property of the spray injected from them can be made to approximate to each other.
In addition, the difference of the respective flow channel lengths Ln 201, Ln 202 may be achieved by making the wall thicknesses t1, t2 of the first region 260a and the second region 260b that make the respective injection holes 255a, 255b penetrate therethrough differ from each other as the second embodiment. With such a configuration, the possibility of the configuration optimizing the respective L/D values further improves. Also, in the second embodiment, the bottom wall 260 corresponds to “injection hole wall”.
A third embodiment of the present invention shown in
On the other hand, the first expanded diameter hole 364 and the second expanded diameter hole 365 correspond to the respective expanded diameter holes 164, 165 of the first embodiment (refer to
Next, the L/D value in the injection hole having the tapered hole shape as the respective injection holes 355a, 355b of the third embodiment will be explained in detail below based on
As shown in the part (A) of
As shown in the part (B) of
As shown in the part (C) of
In the third embodiment, the respective L/D values of the first injection hole 355a and the second injection hole 355b are set to approximately 2.5 for example which is a value in the middle of two boundary values described above (2.0, 3.0) and at which the particle diameter of the spray becomes smallest. By setting thus the respective L/D values of the first injection hole 355a and the second injection hole 355b to within a predetermined range, the effect similar to that of the first embodiment comes to be exerted. Therefore, even when reference inside diameters Dn301, Dn302 of the respective injection holes 355a, 355b may be different from each other, the property of the spray injected from them can be made to approximate to each other. Also, in the third embodiment, the bottom wall 360 corresponds to “injection hole wall”.
Although embodiments according to the present invention have been explained above, the present disclosure is not to be interpreted so as to be limited to the embodiments described above, and can be adapted to various embodiments and combinations within the range not departing from the substance of the present disclosure.
According to the embodiments described above, two injection holes having different reference inside diameter were set so that the respective L/D values became equal to each other. However, in three or more injection holes having different reference inside diameter, the respective L/D values may not be the same. In addition, the respective L/D values of the respective injection holes may not be strictly equal to each other, and only have to be set so as to be equal to each other to a degree the property of the spray can be made to approximate to each other. Further, although it is preferable that the L/D values of all injection holes formed in the nozzle body agree to each other, the L/D value of a part of the injection holes may not agree to the L/D values of other injection holes.
According to the embodiments described above, the respective L/D values were stipulated within the range between the upper limit value and the lower limit value which were stipulated based on the shape of the injection hole. However, the respective L/D values of the respective injection holes may agree to each other in the outside of the range between the upper limit value and the lower limit value. Further, the respective L/D values of the respective injection holes may be stipulated to be the values different from each other within the range between the upper limit value and the lower limit value.
In the embodiments described above, the injection holes were arrayed along the same imaginal circle 19 (refer to
In the first and third embodiments described above, the axial direction of the expanded diameter hole was the same as the injection hole axis. However, the axial direction of the expanded diameter hole may cross the injection hole axis. Also, the center of the expanded diameter hole may be positioned so as to shift from the injection hole axis. Further, the expanded diameter hole is not limited to the cylindrical hole shape as described above, and may be of a tapered hole shape in which the diameter is expanded toward the fuel downstream side, or of a semi-spherical shape in which the outer surface of the nozzle body is recessed, and so on. Furthermore, the expanded diameter hole may be arranged in the form of communicating with the sack chamber in the fuel upstream side of the injection hole instead of the fuel downstream side of the injection hole.
According to the second embodiment described above, the injection holes with different flow channel length were achieved by changing the machining thickness for machining the outer surface of the nozzle body for each region. With such a configuration, the step surface in the radial direction is not formed between the injection hole and the expanded diameter hole. Therefore, the event that the deposit is deposited in the outer peripheral part of the step surface can be avoided. The method of arranging the difference between the wall thickness of the first region and the wall thickness of the second region in the nozzle body thus is not limited to such machining as described above. For example, it is also permissible that the difference of the wall thickness of the first region and the second region has already been arranged at the time of forming the nozzle body. Further, as far as the wall thickness before machining in the first region has already been corresponding to the flow channel length of the first injection hole, only the second region may be formed by machining out of the first region and the second region.
Number | Date | Country | Kind |
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2013-161594 | Aug 2013 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2014/003967 | 7/29/2014 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2015/015797 | 2/5/2015 | WO | A |
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20080196691 | Kihara et al. | Aug 2008 | A1 |
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H1-208563 | Aug 1989 | JP |
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Entry |
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International Search Report for PCT/JP2014/003967 dated Oct. 28, 2014, 5 pages. |
Written Opinion of the ISA for PCT/JP2014/003967 dated Oct. 28, 2014, 8 pages. |
Number | Date | Country | |
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20160195052 A1 | Jul 2016 | US |