Patent Application
20190285039
This application is based on Japanese Patent Applications No. 2018-48408 filed on Mar. 15, 2018 and No. 2019-3979 filed on Jan. 14, 2019, the disclosure of which is incorporated herein by reference.
The present disclosure relates to a corrosion resistant device.
Conventionally, a fuel injection valve is used in an internal combustion engine. A fuel injection valve typically includes a metallic nozzle formed with an injection hole for injecting fuel.
According to an aspect of the present disclosure, a first member has a plated layer. A second member is pressed against a portion of the first member on which the plated layer is applied. The plated layer may have a specific property.
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:
To begin with, an example of the present disclosure will be described as follows. A fuel injection valve for an internal combustion engine includes a metallic nozzle. The metallic nozzle has an injection hole for injecting fuel. In the present example, plating is applied to the surface of the nozzle in order to reduce erosion of the nozzle.
It is conceivable that the nozzle has a high stress portion which is applied with plating and in which a high stress arises. In the conceivable condition, the portion of the nozzle may be presumably reduced in corrosion resistance due to the high stress, and consequently, the portion of the nozzle may not exhibit sufficient corrosion resistance. In other words, even though the high stress portion is applied with plating, the plated portion would hardly secure its corrosion resistance at a sufficient level due to, for example, occurrence of cracking. In consideration of such an issue, a configuration may be conceivable which enables to restrict occurrence of cracks in a plated layer applied to such a high stress portion. The configuration may be provided as a corrosion resistant device configured to sufficiently secure its corrosion resistance.
As follows, a description will be made on an assumable corrosion resistant device. The corrosion resistant device includes a first member having a plated layer applied to a metal base material. The corrosion resistant device further includes a second member pressed against a portion of the first member on which the plated layer is applied.
Further details of the example of the corrosion resistant device will be described. Specifically, a tensile stress is caused in the first member by pressing the second member against the first member. A breakage probability is a probability of breakage of the plated layer caused by the tensile stress. A characteristic slope is a slope of a characteristic line, which represents a relationship between an elastic modulus of the plated layer and the breakage probability. The slope is a ratio of an increase amount of the breakage probability to a decrease in the elastic modulus by a predetermined amount.
A change point appears at a characteristic change point on the characteristic line, at which the elastic slope changes from a slope, which is less than a predetermined slope, to a predetermined slope or more, as the elastic modulus gradually decreases. The elastic modulus at the characteristic change point is a characteristic change elastic modulus.
The plated layer contains at least a chromium component, and in addition, has the elastic modulus larger than the characteristic change elastic modulus.
Use of chromium as a material for plating could be effective to increase the elastic modulus of the plating. Thus, cracks are less likely to occur even when plating is applied to a high stress portion. According to the above corrosion resistant device in consideration of this point, the plated layer contains at least the chromium component and has the elastic modulus larger than the characteristic change elastic modulus. For that reason, the configuration could enable to restrict the occurrence of the crack in the plated layer applied to the portion (high stress portion) of the first member where the second member is pressed to cause the high stress, and to sufficiently secure the corrosion resistance by the plated layer.
Hereinafter, multiple embodiments of the present disclosure will be described with reference to the drawings. The same reference numerals are assigned to the corresponding components in each embodiment, and duplicate descriptions may be omitted. When only a part of the configuration is described in each embodiment, the configuration of the other embodiments described above can be applied to other parts of the configuration.
A corrosion resistant device according to the present embodiment is a fuel injection valve 10 shown in
The fuel injection valve 10 includes a valve body 20, a nozzle needle 50, a solenoid control valve 40, and a movable plate 60. The valve body 20 is formed by combining multiple metal members such as an injector body 21, a flow channel forming member 22, a nozzle body 70, and a cylinder 23 with a retaining nut 80.
The retaining nut 80 is made of metal and has a cylindrical shape extending in an axial direction of the fuel injection valve 10. A female threaded portion 80N is provided at one end of an inner peripheral surface of the retaining nut 80 in the axial direction, and a nut locking portion 80a is formed at the other end. In a state in which the nut locking portion 80a locks a body locking portion 70a which is a locking portion of the nozzle body 70, the female threaded portion 80N of the retaining nut 80 is fastened to a male threaded portion 21N formed on an outer peripheral surface of the injector body 21. As a result, the injector body 21, the flow channel forming member 22, and the nozzle body 70 are held in a state of being pressed against each other in the axial direction.
The fuel injection valve 10 is inserted into the insertion hole 2a of the cylinder head 2, and an injection hole 39 provided at a tip of the valve body 20 is exposed to the combustion chamber 1a. One end of a clamp member 3 is engaged with an engagement portion 21a of the injector body 21. The other end of the clamp member 3 is fixed to the cylinder head 2 by a screw or the like. An abutment portion 80b of the retaining nut 80 abuts against an abutment portion 2b located inside the insertion hole 2a of the cylinder head 2. The abutment restricts the fuel injection valve 10 from moving toward the combustion chamber 1a in the axial direction. In other words, the fuel injection valve 10 is attached to the insertion hole 2a of the cylinder head 2 while being sandwiched between the abutment portion 2b of the cylinder head 2 and the clamp member 3.
A high-pressure fuel passage 31, an inflow flow channel 32, an outflow flow channel 33, a control chamber 35, and a low-pressure chamber 38 are provided inside the valve body 20.
The high-pressure fuel passage 31 is provided over the injector body 21, the flow channel forming member 22, and the nozzle body 70, and allows a high-pressure fuel supplied from the common rail not shown to flow through the injection hole 39.
The inflow flow channel 32 is branched from the high-pressure fuel passage 31 by the flow channel forming member 22, and communicates the high-pressure fuel passage 31 with the control chamber 35. The inflow flow channel 32 allows a part of the high-pressure fuel flowing through the high-pressure fuel passage 31 to flow into the control chamber 35. The outflow flow channel 33 communicates the control chamber 35 with the low-pressure chamber 38 to allow the fuel to flow out of the control chamber 35.
The control chamber 35 is a space defined by the flow channel forming member 22, the cylinder 23, the nozzle needle 50, and the like. The control chamber 35 is located on the opposite side of the injection hole 39 across the nozzle needle 50. The control chamber 35 is filled with the fuel supplied through the inflow flow channel 32. The fuel pressure in the control chamber 35 is varied due to an inflow of the fuel through the inflow flow channel 32 and an outflow of the fuel through the outflow flow channel 33.
The low-pressure chamber 38 is an accommodation space provided in the injector body 21. A solenoid control valve 40 is accommodated in the low-pressure chamber 38. An excess fuel discharged through the outflow flow channel 33 flows into the low-pressure chamber 38, and the low-pressure chamber 38 is filled with the fuel having a lower pressure than that of the control chamber 35.
The nozzle needle 50 is made of a metal material in a cylindrical shape. The nozzle needle 50 is displaced relative to the valve body 20 along the axial direction by the variation of the fuel pressure in the control chamber 35, and opens and closes the injection hole 39. The tip of the nozzle needle 50 on the injection hole 39 side is formed in a conical shape. The nozzle needle 50 is accommodated in the nozzle body 70, and receives a force in a direction in which the injection hole 39 is opened (hereinafter referred to as a “valve opening direction”) from the high-pressure fuel supplied through the high-pressure fuel passage 31. The nozzle needle 50 is urged by an urging force of a needle spring 53 toward the cylinder 23 in a direction in which the injection hole 39 is closed (hereinafter referred to as a “valve closing direction”).
The solenoid control valve 40 includes a control valve body 42 that is accommodated in the low-pressure chamber 38 for opening and closing the outflow flow channel 33, and a drive unit 41 for displacing the control valve body 42 based on a drive current. When no electric power is supplied to the drive unit 41, the control valve body 42 closes the valve to interrupt fuel outflow from the control chamber 35 to the low-pressure chamber 38. On the other hand, when the electric power is supplied to the drive unit 41, the control valve body 42 opens the value to allow the fuel to flow from the control chamber 35 to the low-pressure chamber 38.
The movable plate 60 is made of a metal material in a disk shape. The movable plate 60 is disposed in the control chamber 35, and reciprocates along the axial direction of the nozzle needle 50 to open and close the outflow flow channel 33. When the outflow flow channel 33 is opened by the control valve body 42, the fuel in the control chamber 35 is discharged from the outflow flow channel 33 to the low-pressure chamber 38.
Hereinafter, a structure of the nozzle body 70 will be described in detail with reference to
As described above, the injector body 21 and the retaining nut 80 are screwed together in a state in which the retaining nut 80 and the nozzle body 70 are locked with each other. As a result, the injector body 21, the flow channel forming member 22, and the nozzle body 70 are pressed against each other in the axial direction. In this manner, the body locking portion 70a is in a state of being pressed against the nut locking portion 80a, and a pressing force (pushing force) is applied in the axial direction by a screw engagement between the female threaded portion 80N and the male threaded portion 21N. The nozzle body 70 corresponds to a “first member” and the retaining nut 80 corresponds to a “second member”.
The nozzle body 70 has a base material 71 and a plated layer 72, and the nozzle body 70 is formed by applying the plated layer 72 to an outer surface of the base material 71. The base material 71 is made of an iron based metal. The plated layer 72 is hard chromium plating based on chromium. The plated layer 72 is provided in an entire area of an outer surface of the nozzle body 70 from a portion where the injection hole 39 is provided to the body locking portion 70a, that is, in the body locking portion 70a and an entire portion on the injection hole side from the body locking portion 70a in the axial direction. In other words, the plated layer 72 is applied to an area of the outer surface of the nozzle body 70 from a portion where the injection hole 39 is provided to a portion pressed against the retaining nut 80. An inside of the injection hole 39 and an inner surface of the base material 71 are not plated.
A gap CL1 is provided between the plated layer 72 and an inner peripheral surface of the insertion hole 2a. A gap CL2 is also provided between the inner peripheral surface of the nut locking portion 80a of the retaining nut 80 and the plated layer 72. A surface 72a of the plated layer 72 in a portion forming the body locking portion 70a contacts the nut locking portion 80a and is pressed by the pressing force described above. The surface 72a has a shape extending perpendicularly to the axial direction and a shape extending annularly around the center axis.
Next, a manufacturing procedure for forming the plated layer 72 on the base material 71 will be described. First, a masking treatment is performed on a portion of the base material 71 except a portion where the plated layer 72 is to be formed (masking process). In addition, a Sargent bath made of molten chromium is prepared, and a bath temperature, which is a temperature of molten chromium, is set to a target temperature (bath temperature adjustment process). Next, the base material 71 is immersed in a temperature-adjusted Sargent bath, and the base material 71 is electrically connected to the cathode (immersion process). Next, with the energization of an anode and a cathode, the molten chromium is precipitated on a portion of the surface of the base material 71 which has not been subjected to a masking treatment (energization process).
In this case, the plated layer 72 has minute scratches such as fine cracks and voids caused in the precipitation process. The degree to which such minute scratches occur can be adjusted by adjusting a precipitation rate of the plating in the energization process. The precipitation rate can be adjusted by adjusting the bath temperature in a bath temperature adjustment process and a current value related to the energization in the energization process. An elastic modulus of the plated layer 72 can be adjusted by adjusting the precipitation rate.
The elastic modulus is an indentation elastic modulus as defined in the International Organization for Standardization (ISO) 14577. In other words, a load removal amount and a recovery amount are measured when the plated layer 72 is deformed by pressing an indenter into the plated layer 72 for giving a load and then removing the load to restore the deformation. A ratio obtained by dividing the load removal amount measured in this manner by the recovery amount is defined as the indentation elastic modulus. A portion of the plated layer 72 pressed in contact with the indenter is plastically deformed following a shape of the indenter. A portion of the plated layer 72 surrounding the portion in contact with the indenter is elastically deformed. Specific examples of the indenter used for the above measurement include a Berkovich type and a Vickers indenter defined by the International Organization for Standardization (ISO) 14577. The indentation elastic modulus is measured under the conditions that a Poisson's ratio of the plating is 0.3, a Poisson's ratio of the indenter is 0.070, and an elastic modulus of the indenter is 1.14×106 N/mm2.
The indentation elastic modulus of the plated layer 72 is set to be larger than 1.6×105 N/mm2 (refer to
As indicated by arrows in
In particular, the combustion chamber la contains moisture generated by combustion, and the moisture contains acidic components such as a nitrogen compound and a sulfur compound. For that reason, when the moisture reaches the bent portion 70b and the body locking portion 70a through the gaps CL1 and CL2, the corrosion described above easily progresses. When the void 71h occurs in the base material 71 as described above, the nozzle body 70 may be damaged due to a decrease in strength.
Therefore, in the present embodiment, in order to reduce the occurrence of cracks 72h in the plated layer 72x, the elastic modulus of the plated layer 72 is formed to be sufficiently large. As a result, since the plated layer 72 can be sufficiently elastically deformed by following the deformation of the base material 71, no or less crack occurs in the plated layer 72, and the base material 71 is protected from corrosion as shown in
In the fuel injection valve 10 shown in
Solid lines in
Slopes of the characteristic lines L1 and L2, each of which are a ratio of an increase amount of the breakage probability to a decrease in the indentation elastic modulus by a predetermined amount, are defined as characteristic slopes. Change points appearing on the characteristic lines L1 and L2 at which the characteristic slope changes from a slope less than a predetermined slope to a predetermined slope or more as the indentation elastic modulus is gradually decreased are defined as characteristic change points P1 and P2. The indentation elastic moduli at the characteristic change points P1 and P2 are defined as characteristic change elastic moduli E1 and E2.
In the fuel injection valve 10 according to the present embodiment, since the tensile stress is 1100 MPa, the indentation elastic modulus of the plated layer 72 is set to be larger than 1.6×105 N/mm2 in accordance with the characteristic line L1. On the other hand, for example, in the case of the fuel injection valve in which the tensile stress is 800 MPa, it is desirable that the indentation elastic modulus of the plated layer 72 is set to be larger than 1.2×105 N/mm2 in accordance with the characteristic line L2. The precipitation rate of the plating is adjusted by adjusting the bath temperature and the current value so as to obtain such an indentation elastic modulus. The film thickness of the plated layer 72 is adjusted to be 0.1 82 m or more and less than 10 μm.
As described above, according to the present embodiment, the plated layer 72 includes at least a chromium component and has the indentation elastic modulus larger than the characteristic change elastic modulus E1. For that reason, the occurrence of the crack 72h can be restricted in the plated layer 72 applied to the portion (high stress portion) of the nozzle body 70 (first member) against which the retaining nut 80 (second member) is pressed and becomes high stress. As a result, the corrosion resistance of the plated layer 72 can be sufficiently ensured. Further, in the present embodiment, the fuel injection valve 10 is mounted on the combustion system having the internal combustion engine 1, and the nozzle body 70 is mounted on the combustion system so as to be exposed to an exhaust gas of the internal combustion engine 1. For that reason, since the moisture W containing the acidic component such as a nitrogen compound or a sulfur compound is attached to the nozzle body 70, a requirement for corrosion resistance of the nozzle body 70 is high. Therefore, the effect of “sufficient corrosion resistance can be ensured” described above is suitably exhibited.
Further, in the present embodiment, the first member and the second member are provided in the fuel injection valve 10 for injecting the fuel into the combustion chamber la of the internal combustion engine 1. The tensile stress as a condition for specifying the characteristic lines L1 and L2 is a magnitude generated in a state where the fuel injection valve 10 is mounted on the combustion system. As described above, a large tensile stress acts on the fuel injection valve 10, and a requirement for corrosion resistance is high, so that the effect of “sufficient corrosion resistance can be ensured” described above is suitably exhibited.
Further, in the present embodiment, the tensile stress caused when the fuel injection valve 10 is mounted on the combustion system is 1100 MPa, and the characteristic change elastic modulus in the characteristic line L1 is 1.6×105 N/mm2. Therefore, in the present embodiment, since the elastic modulus is set to be larger than 1.6×105 N/mm2, it is possible to reduce the occurrence of the crack 72h in the plated layer 72.
Further, in the present embodiment, the plated layer 72 is applied in a range from a portion of the nozzle body 70 where the injection hole 39 is formed to a portion of the nozzle body 70 which is pressed against the retaining nut 80. Since the above range is a portion exposed to the exhaust gas, the moisture W containing the acidic component may adhere to the range. Therefore, the effect of “sufficient corrosion resistance can be ensured” described above is suitably exhibited.
Further, in the present embodiment, the film thickness of the plated layer 72 is 0.1 μm or more and less than 10 μm. This makes it possible to restrict the corrosion resistance and the abrasion resistance from becoming inadequate due to an excessively thin film thickness. For example, in a case where the film thickness of the plated layer 72 is less than 0.1 pm contrary to the present embodiment, there is a concern that the moisture W reaches the base material 71 through the void existing in the plated layer 72 even though the crack 72h does not occur. On the other hand, in the present embodiment, since the film thickness of the plated layer 72 is 0.1 μm or more, the above-mentioned concern can be reduced. Further, since the film thickness of the plated layer 72 is less than 10 μm, it is possible to restrict a precipitation time of plating from becoming longer than necessary because the film thickness is excessively thick.
In the first embodiment, no plated layer is formed on the surface of the retaining nut 80, whereas in the present embodiment, the plated layer is also formed on the surface of the retaining nut 80. In the following description, the base material 71 and the plated layer 72 included in the nozzle body 70 are referred to as a first base material and a first plated layer, and the base material and the plated layer included in the retaining nut 80 are referred to as a second base material and a second plated layer.
As shown in
The material and the film thickness of the second plated layer 82 are the same as those of the first plated layer. The method of manufacturing the second plated layer 82 is also the same as that of the first plated layer, and the elastic modulus of the second plated layer 82 can be adjusted by adjusting the precipitation rate of plating.
In the same manner as the tensile stress shown by the arrows in
Therefore, the slope of the second characteristic line, which is the ratio of the increase amount of the second breakage probability to the decrease in the second elastic modulus by a predetermined amount, is the same as the characteristic slope of the first characteristic line (first characteristic slope). The second characteristic change point, which is a change point appearing on the second characteristic line and at which the second characteristic slope changes from a slope less than a predetermined slope to a predetermined slope or more as the second elastic modulus is gradually decreased, is also the same as the characteristic change points P1 and P2 (first characteristic change point) appearing on the first characteristic line. The second elastic modulus at the second characteristic change point is defined as the second characteristic change electric modulus, and the second plated layer 82 is formed so that the second elastic modulus of the second plated layer 82 is larger than the second characteristic change elastic modulus.
As described above, according to the present embodiment, the second plated layer 82 includes at least the chromium component and has the second indentation elastic modulus larger than the second characteristic change elastic modulus. This makes it possible to restrict the occurrence of the crack in the second plated layer 82 applied to the portion (high stress portion) of the retaining nut 80 (second member) where the nozzle body 70 (first member) is pressed into a high stress. As a result, the corrosion resistance of the second plated layer 82 can be sufficiently ensured.
In addition, the second plated layer 82 applied to the portion of the retaining nut 80 where the cylinder head 2 is pressed into the high stress can also be restricted from cracking due to the stress.
Similarly to the first embodiment, in the fuel injection valve 10 according to the present embodiment, the internal stress (tensile stress) caused in the base material 71 of the body locking portion 70a is 1100 MPa. Similarly, the plated layer 72 according to the present embodiment contains at least chromium component, and its indentation elastic modulus is set to be larger than 1.6×105 N/mm2. In addition, as described below in detail, the plated layer 72 is formed to have a void ratio which is set to be equal to or less than 0.5%.
As shown in
It is considered that the voids 72L and 72S are generated in the precipitation process among the manufacturing process for forming the plated layer 72. A ratio of generation of the large voids 72L can be adjusted by adjusting the precipitation rate of the plating in the energization process. The precipitation rate can be adjusted by adjusting the bath temperature in the bath temperature adjustment process and the current value in the energization implemented in the energization process. Thus, the void ratio can be adjusted by adjusting the precipitation rate.
As described above, according to the present embodiment, the plated layer 72 is formed to have the void ratio equal to or less than 0.5% thereby to enable to further enhance the corrosion resistance with the plated layer 72.
Although the multiple embodiments of the present disclosure have been described above, not only the combinations of the configurations explicitly shown in the description of each embodiment, but also the configurations of the multiple embodiments can be partially combined together even if the combinations are not explicitly shown if there is no problem in the combinations in particular. Unspecified combinations of the configurations described in the multiple embodiments and the modifications are also disclosed in the following description. Modifications of the embodiments described above will be described.
In the first embodiment, the tensile stress caused when the fuel injection valve 10 is mounted on the combustion system is 1100 MPa, but may be 800 MPa, for example. The characteristic change elastic modulus in the characteristic line L2 is 1.2×105 N/mm2 (refer to
In the case where the tensile stress is 800 MPa, the plated layer 72 contains at least chromium component, its indentation elastic modulus is set to 1.2×105 N/mm2 or more, and furthermore, the plated layer 72 may be formed to have the void ratio equal to or less than 1.0%.
In
In
In the first embodiment described above, the elastic modulus of the plated layer 72 is a ratio of the load removal amount to the recovery amount when the plated layer 72 is loaded and deformed and then the load is removed to restore the deformation. On the other hand, the elastic modulus of the plated layer 72 may be a ratio of the load application amount and the deformation amount when the plated layer 72 is loaded and deformed. Also, the indentation elastic module is not limited to the indentation elastic modulus defined by the International Standards Organization (ISO) 14577.
The combustion system to which the corrosion resistant device is applied may have an exhaust gas recirculation mechanism for mixing a part of the exhaust gas of the internal combustion engine 1 into the intake air as a recirculation gas. When the first member provided in the corrosion resistant device is disposed so as to be exposed to the recirculation gas, the above-mentioned influence of improving the corrosion resistance can be suitably exhibited.
It should be appreciated that while the processes of the embodiments of the present disclosure have been described herein as including a specific sequence of steps, further alternative embodiments including various other sequences of these steps and/or additional steps not disclosed herein are intended to be within the steps of the present disclosure.
While the present disclosure has been described with reference to embodiments thereof, it is to be understood that the disclosure is not limited to the embodiments and constructions. The present disclosure is intended to cover various modification and equivalent arrangements. In addition, the various combinations and configurations, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-48408 | Mar 2018 | JP | national |
| 2019-3979 | Jan 2019 | JP | national |
