CN111136561A

CN111136561A - Belt polishing method and device for fuel injection component

Info

Publication number: CN111136561A
Application number: CN201911055159.2A
Authority: CN
Inventors: R·O·爱德华兹; A·E·列辛
Original assignee: Cummins Inc
Current assignee: Cummins Inc
Priority date: 2018-11-01
Filing date: 2019-10-31
Publication date: 2020-05-12

Abstract

The invention provides a belt polishing method and device for a fuel injection component. Methods and apparatus for reducing surface roughness of a fuel injector component apply a first side of an abrasive member to a surface of the fuel injector component. The surface may be between about 0.5mm to about 5mm in length. The method and apparatus then brings an advancing tool into contact with the second side of the abrasive member. The second side is opposite the first side, wherein the advancement tool is configured to substantially correspond to a surface geometry of the fuel injector component. The method and apparatus then polishes the surface to achieve a surface roughness parameter of less than 0.5 μm by rotating at least one of the fuel injector component and the advancing tool. Subsequently, after polishing the surface, the abrasive member is removed from the surface.

Description

Belt polishing method and device for fuel injection component

Technical Field

The present disclosure relates generally to diesel engine components, and more particularly to polishing surfaces of diesel engine components using abrasive members.

Background

Certain engine components, particularly diesel engine components, may not initially have the surface properties and/or characteristics necessary to perform certain functions. For example, fuel injection system components of a diesel engine may include components having complex geometries, mating components, coated components, and/or components that experience fatigue, wear, and friction. Thus, even with careful manufacture, the components may require extrinsic characteristics and properties. For example, the surface finish (e.g., roughness) of some components may initially be unacceptable for performing some necessary functions during operation of a diesel engine.

In some cases, the component may be machined to reduce surface roughness. For example, the processes for reducing surface roughness may include various precision machining techniques, such as grinding, superfinishing, and/or other processes such as electrochemical machining. However, some of these techniques (e.g., electrochemical machining and electropolishing) may require one or more electrodes shaped into a form that requires machining into a workpiece, and may use chemicals that generate hazardous waste. Furthermore, some techniques may not be effective to reduce the surface roughness by a sufficient amount due to the complex geometry of the component (e.g., curved or tapered surfaces). Accordingly, it would be desirable to use systems and methods that obviate or mitigate one or more of the above-described operational deficiencies.

Disclosure of Invention

In some embodiments, a method for reducing surface roughness of a high pressure fuel injector component is provided. The method applies a first side of an abrasive member to a surface of the fuel injector component. The surface has a length of between about 0.5mm and about 5 mm. The method then contacts an advancing tool with the second side of the abrasive member. The second side is opposite the first side, and the advancing means substantially corresponds to a surface geometry of the fuel injector component. The method then polishes the surface to achieve a surface roughness parameter of less than 0.5 μm by rotating at least one of the fuel injector component and the advancing tool. Finally, after polishing the surface, the method removes the abrasive member from the surface.

In one embodiment, the surface of the fuel injector component is dry when the abrasive member is applied thereon, and remains dry when the abrasive member is removed from the surface of the fuel injector component. In another embodiment, the method uses a cutting fluid to rinse away the residue. In one embodiment, the surface geometry is a complex geometry consisting of two or more basic geometries. In one embodiment, the method further comprises applying a coating to the surface after removing the abrasive member. In one embodiment, the abrasive member is a polyester film, a cloth film, or a plastic film. Further, in one embodiment, the fuel injector component is a fuel injector seat. In one aspect of an embodiment, the surface geometry of the fuel injector seat includes a conical portion, and in another aspect, the surface geometry further includes an opening portion having a constant diameter. In another embodiment, the surface geometry of the fuel injector seat includes a curved bottom. In addition, in another embodiment, the method further comprises removing burrs that are created at edges along the surface as a result of the pre-polishing manufacturing process. In yet another embodiment, the method measures and reports one to ten point average roughness (Rz), arithmetic average roughness (Ra), and surface area roughness (Sa) of the surface by using a scanning device. The surface roughness parameters include one or more of the Rz value, the Ra value, and the Sa value.

In some embodiments, an apparatus for reducing surface roughness of a high pressure fuel injector component using the above method is provided. The device includes: a first mechanical assembly holding the fuel injector component and a second mechanical assembly holding a forward tool; and a controller that controls movement of the first mechanical assembly and the second mechanical assembly. The first and second mechanical assemblies contact the advancement tool with the second side of the abrasive member and polish a surface of the fuel injector component by rotating at least one of the fuel injector component and the advancement tool. In one embodiment, the apparatus further comprises a scanning device to measure Rz, Ra and Sa values of the surface.

While multiple embodiments are disclosed, other embodiments of the present disclosure will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the disclosure. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.

Drawings

The above-mentioned and other features of this disclosure, and the manner of attaining them, will become more apparent and the disclosure itself will be better understood by reference to the following description of embodiments of the disclosure taken in conjunction with the accompanying drawings, wherein:

FIG. 1 shows a partial cross-sectional view of a fuel injector component with a needle component inserted therein;

FIG. 2 shows a schematic view of a polishing apparatus disclosed herein;

FIG. 3 shows a close-up view of a cross-sectional view of an embodiment of using an abrasive member to polish a surface of a workpiece;

FIG. 4 shows a 3D surface map of a surface polished using the different methods disclosed herein;

FIG. 5 shows a close-up view of a 3D surface map from above, where each map shows a surface polished using a different method;

FIG. 6 shows a partial cross-sectional view of another fuel injector component;

FIG. 7 illustrates a close-up view and a cross-sectional view of a fuel injector component after being processed with a baseline burnishing process (lapping) and a band burnishing process as disclosed herein;

FIG. 8 shows a close-up view of a fuel injector component after treatment with a PEP and band polishing process, followed by a knock-in test (beat-in test);

fig. 9 shows a block diagram of performing a belt polishing process as disclosed herein.

While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. However, it is not the intention to limit this disclosure to the particular embodiments described. On the contrary, the disclosure is intended to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure as defined by the appended claims.

Detailed Description

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the present disclosure. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims and their equivalents.

FIG. 1 illustrates one embodiment of a fuel injector component 100, and the systems and methods disclosed herein may be used with the fuel injector component 100 to polish a surface thereof. The fuel injector 100 has a bladder 102 with one or more nozzle holes 104 through which fuel is injected 104. The body of the fuel injector 100 has a surface 106 having a tapered configuration and receiving a needle member 108, and a needle tip 110 of the needle 108 is inserted into an opening defined by the surface 106 until an edge 112 of the needle 108 contacts the surface 106, thereby preventing further advancement of the needle 108. When the needle 108 is raised by actuating a solenoid or other actuation device, high pressure fuel is allowed to flow into the bladder 102 and out of the nozzle holes 104.

In view of the above explanation regarding the fuel injector 100, surface smoothness is important to allow for efficient flow of fuel and through the fuel injector. For example, if the fuel injector has a rough surface, the roughness can cause undesirable friction and disrupt the flow of fuel and reduce the fatigue and wear resistance of the surface. Furthermore, roughness can hinder optimization of surface stresses and hinder preparation for applying friction coatings to surfaces. Furthermore, roughness reduces wettability, or reduces the degree of wetting, which is used to determine the amount of fluid that can be spread on a surface, as determined by the adhesion and cohesion of the fluid, which varies with surface roughness. Other benefits known in the art may be realized by virtue of the smooth surfaces in the fuel injector.

Fig. 2 shows a polishing apparatus 200, the polishing apparatus 200 comprising: a controller 202 electrically connected to the scanner 204; a first mechanical assembly 206; and a second mechanical assembly 208. The electrical connections are depicted in dashed lines. The scanner 204 is any known optical scanner, for example, utilizing a fiber-based non-contact optical probe, which detects peaks and valleys present on a surface with high accuracy. The mechanical assemblies 206 and 208 operate independently of each other and with the controller 202. The first mechanical assembly 206 is coupled to a workpiece 210 and the second mechanical assembly 208 is coupled to an advancement tool 212. Abrasive member 214 is applied to workpiece 210.

Abrasive member 214 covers at least a portion of the surface of workpiece 210 being polished. When the mechanical assemblies 206 and 208 are operated, the workpiece 210 and the advancement tool 212 contact each other with a layer of abrasive members 214 therebetween. The advancement tool 212 substantially corresponds to the surface geometry of the workpiece 210 to polish the surface of the workpiece 210. FIG. 3 illustrates one embodiment of how the workpiece 210 is polished. The forwarding tool 212 uses a soft polishing pad 300, which soft polishing pad 300 rubs against the abrasive member 214 on the surface of the workpiece 210 to polish the surface of the workpiece 210. In one embodiment, the length of the area being polished is between about 0.5mm and about 5mm, which may be too small for some prior art polishing processes (e.g., lapping) to polish. In one embodiment, the first mechanical assembly 206 is a spin chuck that holds the workpiece 210 and rotates the workpiece at a speed between 500 and 800rpm, while the second mechanical assembly 208 holding the forwarding tool 212 is stationary. The process can be optimized to avoid causing dimensional changes large enough to affect the function of the workpiece being polished.

The length of the region to be polished is not particularly limited to 0.5mm and 5 mm. As used herein, the modifier "about" used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes at least the degree of error associated with measurement of the particular quantity). The modifier "about" when used in connection with a range is also to be construed as disclosing the range defined by the absolute values of the two endpoints. For example, a range of "from about 0.5 to about 5" also discloses a range of "from 0.5 to 5".

One advantage of implementing the systems and methods disclosed herein includes the ability to polish the component to achieve a uniform surface. One example of such a uniform surface is a component surface having a ten point average roughness (Rz) value of 0.5 μm or less than 0.5 μm. The Rz values differ from the arithmetic average roughness (Ra) values in that they take into account the vertical distance from the highest peak to the lowest valley over five sample lengths and average these distances. Because Rz averages the five highest peaks and five deepest valleys (hence the "ten point roughness average"), the Rz value is more affected by extreme values (i.e., extremely high or low points on the surface). Furthermore, in some cases, Rz values will take into account less than ten such points. Another embodiment of determining the surface roughness is by calculating the surface area roughness (Sa), which is the arithmetic average of the 3D roughness, i.e. taking into account the roughness of the whole area, rather than just taking the average roughness along linear portions like Ra.

As mentioned above, one prior art embodiment of the surface finish process is grinding, which is suitable for removing particles having a significant size (e.g., particles having a height greater than 50 μm), but is not suitable for finer finishes required for certain components (e.g., fuel injectors in engines). In another prior art embodiment of the surface polishing process, a Plasma Electropolishing (PEP) process is used to form a plasma layer around the surface of the component as a result of applying a voltage to the plasma electrolyte polishing unit. The surfaces made by the prior art processes (i.e., the grinding and PEP processes) and the surfaces made by the belt polishing process disclosed herein are compared to one another in fig. 4. Specifically, the first surface 400 is polished using only a grinding process; the second surface 402 is polished first by grinding and then by using the PEP process; and the third surface 404 is polished first by grinding and then by using a belt polishing process.

As shown by the many peaks and valleys in the surface polished using the grinding process, the Rz value of the first surface is much higher than 1 μm, making the surface too rough. As shown, although the Rz value of the second surface treated with the PEP process was about 0.5 μm, the finished surface was spongy (spongy) and still contained many peaks protruding from the surface (as shown). The Rz value of the third surface treated with the tape polishing process was about 0.3 μm, and appeared to show fewer peaks than any of the previous first and second surfaces. For ease of comparison, the close-up image 500 of fig. 5 shows an enlarged view of the second surface 402, and the close-up image 502 shows an enlarged view of the third surface 404 of fig. 4. The third surface 404 treated with the belt polishing process has a number of vertically extending striations compared to the second surface 402 treated with the PEP, wherein each striation has a uniform height and therefore does not contain as many peaks as in the PEP treated surface. In some cases, as described below, the difference between the spongy surface and the uniform surface can affect the performance of the component.

In the case of fuel injectors, the surfaces of the fuel injector need to be coated with a friction coating after polishing. Examples of such coatings include: a diamond-like carbon (DLC) or hydrocarbon layer applied using a Physical Vapor Deposition (PVD) process; and CrC, CrN, and Cr-C-N film coatings, among others. PVD coatings are particularly effective in reducing friction and protecting the coated surface from wear. For the surface to which the coating is applied, the roughness profile defined by Rz values and surface texture (Sa) has an effect on the adhesion of the PVD coating as well as on the coating properties during operation. For example, if a PVD coating is applied to the sponge-like surface of FIG. 4 (i.e., the first surface or the second surface), after heavy use, the coating will first gradually wear away or peel (peel) at the highest peaks, resulting in exposure of the uncoated portion of the part to the environment. Furthermore, shear stresses applied to uneven surfaces can cause the coating to crack when the individual parts slide across the surface, due to adhesive failure of the contacting surfaces of the coating. The shear stress varies according to the surface roughness and the coefficient of friction (CoF). Therefore, to prevent coating cracking and uneven wear out of the coating over the entire surface, a more uniform surface polished using a belt polishing process is preferred.

In addition to the Ra, Rz and Sa values, the fuel injector must also meet other specifications. For example, one requirement is that the inner edge radius of the fuel injector must not be less than 15 μm. Edge radii define the curvature of the edge, with smaller edge radii indicating sharper edges and larger edge radii indicating more curved edges. Fig. 6 shows an embodiment of a fuel injector component 600 in which an inner edge 602 is located between the surface 106 of the body of the fuel injector and the opening through which fuel is injected. In one embodiment, the opening is a cylindrical path. Fuel injectors benefit from a greater curvature of the edge on the inner surface because the curved edge improves fuel flow within the injector.

Indeed, as shown in fig. 7, which shows the difference between applying the baseline process and the belt burnishing to diesel engine components, the grinding process resulted in sharp edges with edge radii less than 5 μm, but when the belt burnishing process was applied in addition to the grinding process, the edge radii increased to 20 μm with sufficient curvature to meet the 15 μm requirement. For example, a baseline method (e.g., lapping) is applied to the fuel injector component 600 to achieve the surface finish shown in image 700 and the edge radius shown in image 702. The baseline method is the current manufacturing process for these components, such as a multi-stage grinding process. In contrast, a polishing process utilizing tape polishing in addition to grinding is applied to fuel injector component 600 to achieve the surface finish shown in image 704 and the edge radius shown in image 706.

FIG. 8 illustrates another advantage of using a band polishing process on a fuel injector: and (4) durability. Valves for fuel injectors have been extensively tested in which the valve seat is placed in an environment that mimics the operating conditions of the valve seat placed in the fuel injector. In one embodiment, the metal spherical object was constantly in contact with the valve seat during the "knock-in" test to see if prolonged continuous contact would cause wear of the valve seat coating.

In one experiment, as shown in fig. 8, both the PEP and belt polishing processes achieved Rz values less than 0.5 μm, but the surface texture changed dramatically after the tap-in test. In image 800, areas with substantial coating loss are marked with white circles for valve seats that received PEP treatment, whereas as shown in image 802, areas where no such areas were present on valve seats polished with a belt polishing process, almost all of the coating remained intact after the knock-in test. In fact, surfaces polished using the belt polishing process tend to have a smaller Sa value than surfaces polished using the PEP process, resulting in a smoother surface texture than the latter. The advantage of a smoother surface texture includes less coating loss during testing. Furthermore, PEP processed surfaces showed adhesion at HF1 to HF5, with only indentations classified as HF1 and HF2 corresponding to sufficient adhesion, as measured by the desmler-bendrox rocwell-C adhesion test. However, the surface polished using the tape polishing process showed adhesion at HF 1. In this way, the tape polishing process results in higher coating adhesion.

Fig. 9 illustrates the steps of performing the belt polishing process disclosed herein. In step 900, a first side of an abrasive member is applied on a surface of a fuel injector component. In step 902, an advancing tool is brought into contact with a second side of the abrasive member. In step 904, the surface is polished to a surface roughness parameter of less than 0.5 μm by rotating at least one of the fuel injector component and the advancing tool. Then, in step 906, after the surface is polished, the abrasive member is removed from the surface.

For convenience, embodiments of the present disclosure are described with respect to fuel injection components, but the present disclosure may be technically applicable to other devices and machines not limited to fuel injection or even engine components. Indeed, the belt polishing techniques described herein may be used for any high-precision component where the surface smoothness of the component plays a critical role in maintaining the optimal performance of the component.

In one embodiment, the belt polishing technique may be used for bearings, such as rolling element bearings, where balls or rollers are used to minimize friction between two adjacent components in the machine. In another embodiment, the technique may be used with prosthetic components, such as in knee replacement implants, where smoothing the surface of the component prior to implantation in the patient is critical to preventing corrosion or other degradation of the component due to prolonged use.

In yet another embodiment, workpieces in medical instruments used for diagnosis or treatment (e.g., endoscopes) also benefit from belt polishing techniques. For endoscopes, a rough surface on the workpiece can lead to the accumulation of deposits consisting of foreign matter, which can degrade optical performance and risk leaving some deposits in the patient that may lead to infection. The tape polishing technique may be applied to other high-precision components in various industrial fields (e.g., aerospace, electronics, life sciences, medical devices, etc.) as deemed appropriate by those of ordinary skill in the art.

Embodiments of the present disclosure have been described, by way of example only, with reference to the accompanying drawings. Furthermore, the description herein is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. Thus, although the present disclosure includes particular embodiments and arrangements of elements, the scope of the present system should not be so limited, as other modifications will become apparent to those skilled in the art.

It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. For example, it is contemplated that features described in association with one embodiment may optionally be additionally or alternatively applied to features described in association with another embodiment. The scope of the disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

1. A method of reducing surface roughness of a fuel injector component, the method comprising:

applying a first side of an abrasive member on a surface of the fuel injector component, wherein the surface is between about 0.5mm to about 5mm in length;

contacting an advancing tool with a second side of the abrasive member, wherein the second side is opposite the first side, and wherein the advancing tool is configured to substantially correspond to a surface geometry of the fuel injector component;

polishing the surface to a surface roughness parameter of less than 0.5 μm by rotating at least one of the fuel injector component and the advancing tool; and

after polishing the surface, removing the abrasive member from the surface.

2. The method of claim 1, wherein the surface of the fuel injector component is dry when the abrasive member is applied thereon and remains dry when the abrasive member is removed therefrom.

3. The method of claim 1, wherein the surface geometry is a complex geometry consisting of two or more basic geometries.

4. The method of claim 1, further comprising:

after removing the abrasive member, a coating is applied to the surface.

5. The method of claim 1, wherein the abrasive member comprises a polyester film, a cloth film, or a plastic film.

6. The method of claim 1, wherein the fuel injector component is a fuel injector seat.

7. The method of claim 6, wherein the surface geometry of the fuel injector mount comprises a conical portion.

8. The method of claim 7, wherein the surface geometry further comprises an open portion having a constant diameter.

9. The method of claim 6, wherein the surface geometry of the fuel injector seat comprises a curved bottom.

10. The method of claim 1, further comprising:

burrs created at the edges along the surface due to the pre-polishing manufacturing process are removed.

11. The method of claim 1, further comprising:

measuring and reporting a one to ten point average roughness (Rz), an arithmetic average roughness (Ra) and a surface region roughness (Sa) of the surface with a scanning device, wherein the surface roughness parameters comprise one or more of the Rz value, the Ra value and the Sa value.

12. An apparatus for reducing surface roughness of a fuel injector component, the apparatus comprising:

a first mechanical assembly configured to hold the fuel injector component, wherein a first side of an abrasive member is applied on a surface of the fuel injector component, the surface having a length between about 0.5mm and about 5 mm;

a second mechanical assembly configured to hold a forward tool, wherein the forward tool is configured to substantially correspond to a surface geometry of the fuel injector component; and

a controller configured to control movement of the first and second mechanical assemblies, wherein the first and second mechanical assemblies are configured to:

contacting the advancement tool with a second side of the abrasive member, wherein the second side is opposite the first side, and

polishing a surface of the fuel injector component by rotating at least one of the fuel injector component and the advancing tool.

13. The apparatus of claim 12, further comprising:

a scanning device configured to measure one to ten point average roughness (Rz), arithmetic average roughness (Ra), and surface area roughness (Sa) of the surface, wherein the surface roughness parameters comprise one or more of the Rz value, the Ra value, and the Sa value.

14. A method for reducing surface roughness of a high-precision component, the method comprising:

applying a first side of an abrasive member on a surface of the high-precision component, wherein the surface is between about 0.5mm to about 5mm in length;

contacting an advancement tool with a second side of the abrasive member, wherein the second side is opposite the first side, and wherein the advancement tool is configured to substantially correspond to a surface geometry of the high-precision component;

polishing the surface to a surface roughness parameter of less than 0.5 μm by rotating at least one of the high-precision part and the advancing tool; and

after polishing the surface, removing the abrasive member from the surface.