Abstract:
An accumulator type injection valve of simple construction and relatively large accumulator capacity has opposed inlet and outlet valves for alternately and intermittently communicating a single chamber with an inlet passage for receiving fuel from a pump and an outlet passage in further communication with an injection nozzle, the outlet valve being an inwardly opening needle valve responsive to fluid pressure within the chamber. In order to even further improve operating response of the injection valve, a dump valve relieves fluid pressure from the chamber below a preselected pressure.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     Cross reference is made to a related application entitled &#34;Accumulator Type Injection Valve Including a Dump Valve for Fast Response&#34;, issued on Sept. 28, 1976, as U.S. Pat. No. 3,982,694, and assigned to the Assignee hereof. 
     BACKGROUND OF THE INVENTION 
     The present invention is directed to an accumulator-type fuel injection valve and more particularly to such a valve wherein a single chamber is employed as both a valve chamber and an accumulator chamber to provide increased accumulator capacity while achieving simplicity of construction within the valve as well. Preferably, the fuel injection valve also includes a dump valve for relieving fluid from the chamber below a preselected pressure level in order to improve operating response of the injection valve. 
     The prior art is exemplified, for example, by U.S. Pat. No. 3,788,546, which discloses a typical fuel injection valve, as well as U.S. Pat. No. 3,598,314 which is directed toward a &#34;trapped volume&#34; fuel injection valve, both of the above patents being assigned to the assignee of the present invention. 
     SUMMARY OF THE INVENTION 
     A fuel injection valve providing a relatively large accumulator capacity in comparison with the size of the valve is provided by employing a single chamber as both a valve chamber and an accumulator chamber. Opposed inlet and outlet valves alternately and intermittently communicate the single chamber with an inlet passage through which fuel under pressure is delivered and an outlet passage which is in further communication with a nozzle orifice. 
     In a preferred embodiment of the fuel injection valve, a dump valve is also provided to relieve fluid pressure from the chamber below a preselected pressure level in order to improve response of the injection valve. 
     Additional objects and advantages of the invention are made apparent in the following description having reference to the accompanying drawing. 
    
    
     DESCRIPTION OF THE DRAWING 
     The single drawing is a longitudinally sectioned view of a fuel injection valve constructed according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The single FIGURE illustrates a fuel injection valve and nozzle combination 11 of the type employed within internal combustion engines for atomization of fuel and timed injection of the fuel as a spray into the engine cylinders. The fuel injection valve has an inlet passage 12 which is conventionally coupled with a fuel pump (not shown) suitable for delivering fuel under pulsating pressure. The fuel injection valve also includes a nozzle assembly 13 having outlet orifices 14 which may be conventionally associated with the respective cylinders of an engine (not shown). 
     The body of the fuel injection valve 11 is formed by a number of elements including an outer shell 16. An inlet plug member 17 forming the inlet passage 12 is secured within the shell 16, for example, by swaging. A threaded connector 18, an adapter element 19 and a dump valve unit 21 are secured in axial alignment with each other by means of a cylindrical case 22 adapted to fit within the shell 16. 
     An additional cylindrical case 23 is also secured to the dump valve unit 21, for example, by swaging, and extends downwardly to support a nozzle head 24 of the nozzle assembly 13. Once the various fuel injection valve and nozzle components are suitably arranged within the two case members 22 and 23, the assembly is secured within the shell 16 by threaded engagement of the member 17 and 18. An O-ring 26 provides a suitable seal between the shell 16 and the case 23. 
     Fuel from the inlet passage 12 is communicated into a radially extending chamber 27 at the base of the dump valve unit 21 by means of an interconnecting passage 28 extending through the various intervening valve components. A cylindrical adapter 29 is arranged directly below the radially extending chamber 27 with a cylindrical spacer 31 extending between the adapter 29 and the nozzle head 24. 
     A single elongated chamber 32 is formed within the cylindrical extension 31 between the adapter 29 and the nozzle head 24. The chamber 32 acts as both a valve chamber and an accumulator chamber within the construction of the present invention. The adaptor 29 forms an inlet passage 33 for communicating fuel from the chamber 27 to the elongated chamber 32. A conical valve seat 34 is formed at one end of the elongated chamber 32 about the inlet passage 33. An inlet valve member 36 has a mating spherical surface 37 adapted to engage the conical seat 34 and close off the inlet passage 33 from the chamber 32. 
     An outlet passage 38 is formed at the opposite end of the elongated chamber 32 in further communication with the orifices 14. A conical valve seat 39 is also formed about the outlet passage 38 to receive an inwardly opening needle valve 41. The needle valve member 41 is of a conventional inwardly opening type, at least to the extent that it is spaced apart from the nozzle head 24 in order to open in response to pressure differential between chamber 33 and the elongated chamber 32. An axial extension 42 of the needle valve 41 extends upwardly and penetrates a bore 43 formed by the inlet valve member 36. 
     A spring 44 is arranged about the needle valve extension 42 for interaction between the needle valve member 41 and the inlet valve member 36 in order to assure alternate and intermittent opening of the two valves. As described in greater detail below, the single chamber 32 is thus placed either in communication with the inlet passage 33 to be charged with fuel under pressure or with the outlet passage 38 for the injection of fuel through the orifices 14. 
     In order to provide greater accumulator capacity within the valve assembly, the adapter 29 also forms an annular chamber 46 which is spaced apart from the inlet passage 33. The chamber 46 is in communication with the elongated chamber 32 by means of an intermediate passage 47 which is also formed by the adapter 29. 
     The components described immediately above and arranged toward the lower end of the injection valve assembly function together to provide an inwardly opening accumulator type valve having a relatively high accumulator capacity. As noted above, the needle valve 41 tends to open in response to pressure differential between chambers 33 and 32. Following intermittent injection of fuel, the needle valve 41 then tends to close as pressure diminishes within the elongated chamber 32 and the inlet valve 36 opens to permit repressurization of the chamber 32 with fuel from the inlet passage 33. 
     It is desirable within such injection valves to provide a sharp cutoff after each injection cycle for better control over the engine with which the injection valve is associated. The present injection valve improves response of the needle valve 41 by relieving fluid pressure from the elongated chamber 32 and the extension chamber 46 below a selected pressure level. For that purpose, the elongated chamber 32 is in communication with the dump valve unit 21 by means of a passage 51 extending through the adapter 29 and into communication with a cross drilled passage 52. The body 53 of the dump valve unit 21 also forms an axially off center bore 54 which slidably receives a dump valve spool 56. The spool 56 has an axial bore 57 which is in constant communication with the cross drilled passage 52 and accordingly the elongated chamber 32 by means of an annular groove 58 and an interconnecting passage 59. The lower end of the axial bore 57 is closed by a reaction piston 61 which has an enlarged head arranged within the radially extending chamber 27 in order to prevent the spool 56 from blocking off the inlet passage 33. A spring 62 in the upper end of the bore 54 tends to urge the spool 56 downwardly toward a position where an outlet passage 63 in communication with the axial passage 57 registers with a drain outlet passage 64 formed by the dump valve body 53. The passage 64 communicates with the interior of the shell 16 with fluid pressure being relieved from the shell 16 by means of drain passage indicated at 66. 
     The mode of operation for the accumulator valve and nozzle combination of the present invention is believed obvious from the preceding description of its various components. However, the preferred mode of operation for the valve and nozzle combination 11 is described in greater detail below in order to further clarify the invention. 
     As pulsating pressure from the pump (not shown) increases within the inlet passage 33, the inlet valve member 36 shifts downwardly against the spring 44 in order to admit fuel under pressure into the elongated chamber 32 and extension chamber 46. During this period, the needle valve 41 is urged downwardly into closing engagement with the valve seat 39. After pressure in passage 33 reaches dump pressure of the pumps, the pressure differential between 33 and 32 causes the needle valve 41 to be urged upwardly to permit communication between the elongated chamber 32 and the orifices 14 to commence an injection stroke. With the needle valve 41 shifted upwardly against the spring 44, the inlet valve member 36 is urged upwardly into closing engagement against the valve seat 34. 
     The valve members 41 and 36 remain in this position until fluid pressure within the chamber 32 drops below a preselected pressure level at which the needle valve 41 is closed by the spring 44. Through proper timing, pulsating pressure tends to be simultaneously increasing within the inlet passage 33 so that the inlet valve 36 is also urged downwardly to permit repressurization of the elongated chamber 32 with fuel. 
     In order to improve response of the needle valve 41, the dump valve unit 21 functions to relieve fluid pressure from the elongated chamber 32 and the extension chamber 46 as it falls toward the pressure selected for closing of the needle valve 41. In accomplishing this purpose, it may be seen that the dump valve spool 56 is initially shifted upwardly by inlet pressure within the radially extending chamber 27. Its axial passage 57 and accordingly the elongated chamber 32 is thus blocked from the drain provided by the passages 63 and 64. As the elongated chamber 32 and the extension chamber 46 are pressurized with fuel, the dump valve spool 56 also tends to be urged upwardly toward the illustrated position by fluid pressure within its axial passage 57. Toward the end of each injection stroke, pressure diminishes within the axial passage 57. The spring 62 is selected so that as pressure within the elongated chamber 32 falls toward a preselected level, the dump valve spool 56 is shifted downwardly in order to positively relieve fluid pressure from the chamber 32 and accelerate closing response of the needle valve 41. At that time, pulsating pressure tends to be increasing within the inlet passage 33 so that the inlet valve 36 is opened and repressurization of the chambers 32 and 46 commences a new injection cycle. The dump valve spool 56 is also shifted upwardly into its illustrated position by fluid pressure within the chamber 27 in order to accomplish its function during the new cycle.