1. Technical Field
This invention relates generally to a timing tool for measuring and setting the timing of fuel injectors and more particularly to such a tool for measuring and setting plunger position and travel of unit fuel injectors.
2. Background Art
Injection timing is a critical parameter for meeting emission standards on all diesel engines, including those used in locomotive and marine engines. Exact timing of the injectors is important because retarding the injection timing can reduce NOx emissions. However, if the injection timing is retarded beyond a target value, smoke emissions can increase above acceptable limits and the fuel consumption penalty can be excessive.
On many diesel engines, such as the General Motors Electro-Motive Division (EMD) engines, the fuel injection pump and spray nozzle are combined in a single compact unit called a unit injector. Unit injectors meter, atomize, and spray fuel into an associated cylinder of the engine. The pumping function of the injector is accomplished by the reciprocating motion of a constant stroke injection plunger which is actuated by an injector cam on the engine camshaft through an injector rocker arm. In the EMD engine unit injectors, the position of the plunger, and thereby the timing, is adjusted by means of a ball stud and lock nut at the injector actuating end of the rocker arm. The quantity of the fuel injected into each cylinder is varied by rotating the plunger mechanically by means of an injector control rack, or by electronically controlled valves. The plunger stroke remains constant at about ¾ of an inch.
The standard injection timing tool used for setting the injection timing in General Motors EMD engines is used to check the height of the injector plunger as the flywheel is set at a predetermined position. The tool has a steel shaft having a knurled end by which the tool is gripped. An end of the shaft opposite the knurled end has a narrow section that is inserted into a hole in the injector body. At the top of the narrow section, there is a step that acts as a stop to control extension of the tool into the hole so that the step rests directly on the top of the injector body. Above this step there is a larger shoulder that is adapted to be seated on a retainer element of the injector, and is spaced a predetermined distance from the step, for example 2.430 inches. It is this fixed distance between the step and the shoulder that allows the tool to be used as a feeler-type gauge for timing adjustment. The stock timing tool must be held in precise vertical alignment and requires considerable experience and a good sense of “feel” to achieve accurate and repeatable injector timing settings.
Injector timing tools have been developed for measuring injector plunger height on engines in which injector plunger position is controlled by an adjustable push rod connected to an end of the rocker arm opposite the plunger actuator end of the rocker arm. For example, U.S. Pat. No. 4,503,619 issued Mar. 12, 1985 to Nelsen, et al. for an INJECTOR HEIGHT MEASURING TOOL ASSEMBLY describes such a tool. However, the Nelsen, et al. timing tool cannot be used on rocker arm/injector arrangements that have the plunger adjustment means at the plunger actuator end of the rocker arm. For example, an adjustable ball stud mounted in the plunger actuator end of the rocker arm and an associated lock nut are used in the aforementioned EMD series diesel engines. This arrangement requires direct tool access to the ball stud and lock nut for adjustment of injector timing, a requirement prohibited by the Nelsen et al. timing tool which covers the plunger actuator end of the rocker arm.
The present invention is directed to overcoming the problems set forth above. It is desirable to have a fuel injector timing tool that does not require subjective “feel” and critical alignment to measure and set injector plunger position. It is also desirable to have such a tool that allows access to plunger position adjustment components mounted in the plunger activator end of the rocker arm.
In accordance with one aspect of the present invention, a timing tool for a fuel injector includes an elongated tubular member having a central passageway extending between upper and lower open ends. The upper end of the tubular member is adapted to receive a linear displacement measuring device. The timing tool also includes a base member having a first surface that is attached to the lower end of the elongated tubular member in perpendicular relationship with the central passageway of the tubular member. The base member also includes a second surface spaced from and parallel to the first surface that is adapted to be seated in contacting relationship on a retainer element of the fuel injector. The base member also has an aperture extending between the first and second surfaces in axially aligned relationship with the central passageway of the tubular member. The base member also has an end portion spaced from the aperture and is adapted to only partially circumscribe a plunger follower disposed on the retainer element of the fuel injector.
Other features of the timing tool embodying the present invention include the base member being magnetically attachable to the retainer element of the fuel injector.
Another feature of the timing tool embodying the present invention includes the aperture in the base member having a guide bushing disposed therein. The guide bushing has an internal diameter that is sufficient to provide guiding contact with a movable stem element of the linear displacement measuring device when the device is mounted on the upper end of the elongated tubular member.
A more complete understanding of the present invention may be had by reference to the following detailed description when taken in conjunction with the accompanying drawings, wherein:
In accordance with the present invention, a timing tool 10 for measuring and setting the position of a fuel injector plunger 12 of a fuel injector 14, is shown in
In the preferred embodiment of the present invention, the timing tool 10 includes an elongated tubular member 40 having a central passageway 42 extending between a first, or upper, open end 44 and a second, or lower, open end 46. The upper end 44 of the tubular member is adapted to receive a linear displacement measuring device such as a dial indicator 48, as shown, or, if desired, other measuring devices, such as a digital linear indicator.
The timing tool 10 has a base member 50 having an upper, or first, surface 52. The lower end 46 of the elongated tubular member 40 is attached to the first surface 52 of the base member 50 such that the central passageway 42 of the elongated tubular member 40 perpendicular to the upper surface 52 of base member 50. The base member 50 also includes a lower, or second, surface 54 that is spaced from and generally parallel to the first surface 52. The lower surface 54 is adapted to be seated directly on an upper surface 56 of the retainer 18, perpendicular to the axis 11. The base member 50 has an through hole, or aperture, 58 that extends between the upper surface 52 and the lower surface 54 and is in axially aligned relationship with the central passageway 42 of the tubular member 40. Importantly, the base member 50 also an open end 60 that is spaced from the aperture 58 and is adapted to only partially circumscribe the plunger follower 20 disposed on the upper surface 56 of the retainer element 18, and abut an outer circumferential surface of the plunger follower to accurately center the timing tool 10 on the retainer 18.
The measuring device 48 has a stem portion 62 that extends through the central passageway 42 of the elongated tubular member 40, the aperture 58 in the base member 50 and further extends for a distance sufficient to contact a predetermined upper surface of the fuel injector 14. A distal, or contact end 64 of the stem 62 is suitably adapted to contact the upper surface of the fuel injector 14. In one embodiment, the contact end 64 of the stem 62 is knurled to reduce the effect of an oil film that may be present on the top surface of the fuel injector 14.
Desirably, a guide bushing 66 is disposed in the aperture 58 in the base member 50 and has an internal diameter sufficient to provide guiding contact with the movable stem 62 of the linear displacement measuring device 48.
In a preferred embodiment of the present invention, the base member 50 of the timing tool 10 is magnetically attachable to the upper surface 56 of the retainer element 18. The base member 50 may be formed of a magnetic or magnetized metal, or have one or more magnets recessed in, or otherwise fixedly mounted on, the bottom surface 54 of the base member 50. Thus, when the timing tool 10 is seated on the upper surface 56 of the retainer 18, the timing tool 10 can advantageously be used hands-free, allowing both hands to be used when adjustment is required, to loosen the lock nut 38, adjust the ball stud 24, and subsequently retighten the lock nut 38. By maintaining the timing tool 10 on the retainer 18 during the adjustment process, it can be easily observed that the critically set distance adjustment is not altered during tightening of the lock nut 38.
An important benefit of the timing tool embodying the present invention includes being able to rotate the linear distance measuring device 48 so that it is readily observable during timing adjustments. Also, the timing tool 10 can be used to measure injector plunger position as a function of crank angle degrees. Such measurements are typically done to verify that the lobe on the injector cam shaft is phased correctly with the crankshaft. Heretofore this measurement has been carried out by using a dial indicator on the top of the injector rocker arm. However, the geometry of the rocker arm follows an arc, thereby contributing some error to the accuracy of the measurement. The timing tool 10, embodying the present invention, measures only true vertical motion, thereby increasing the accuracy and repeatability of the measurements.
An important advantage of the injector timing tool 10, embodying the present invention, is that it may be used with a specific software program capable of accepting readings from a digital displacement measuring device 48 as an input value and perform specific calculations. Such a process may be easily automated by using an electronic digital indicator in connection with the timing tool 10 and a shaft encoder on the engine. The digital indicator output signal and the shaft encoder output signal may both be connected to a PC, the sensed values provided directly to the software, and a plot or table made of the entire plunger travel profile. To further automate this process, the engine may be turned by a hydraulically actuated bar tool. Alternatively, the PC could be replaced with a PDA or other small microprocessor based unit that accepts the measurement signals, stores the data, performs the calculations, and displays the results. The displayed results are very beneficial in checking a unit that has been timed in the traditional manner or if one is unsure about the timing at which the engine is set. It should be noted that cam shafts are sometimes replaced to provide specific timing events. Heretofore there has been no way to easily and quickly measure injector timing variations attributable to different cam shafts.
Although the present invention is described in terms of a preferred illustrative embodiment, those skilled in the art will recognize that the dial indicator described herein is for the purpose of illustration, and that other measurement devices, such as digital indicators, may be used in conjunction with the injector timing tool embodying the present invention. Such measurement devices are intended to fall within the scope of the following claims. Other aspects, features, and advantages of the present invention may be obtained from a study of this disclosure and the drawing, along with the appended claims.
Number | Name | Date | Kind |
---|---|---|---|
2642047 | Johnson | Jun 1953 | A |
2796674 | Ross | Jun 1957 | A |
2819534 | Kitzman | Jan 1958 | A |
2855692 | Campbell | Oct 1958 | A |
4170072 | Downs | Oct 1979 | A |
4202207 | Johnson et al. | May 1980 | A |
4420973 | Garcia | Dec 1983 | A |
4503619 | Nelsen et al. | Mar 1985 | A |
4711216 | Takeuchi et al. | Dec 1987 | A |
5329803 | Booth | Jul 1994 | A |
5414941 | Carpenter | May 1995 | A |
6622549 | Wlodarczyk et al. | Sep 2003 | B1 |