Device For Adjusting The Timing In Fuel Injection Pumps

Abstract

In a fuel injection pump, for an rpm-independent, arbitrary adjustment of the injection timing, there is provided an electromagnet which, on command, opens or closes a conduit to admit or cut off, respectively, a control pressure affecting an adjusting member and simultaneously, closes or opens a bypass channel communicating with said conduit upstream of said adjusting member.

Description

BACKGROUND OF THE INVENTION

This invention relates to an adjusting device for a fuel injection pump associated with an internal combustion engine. The fuel injection pump is of the type that includes at least one reciprocating pump piston that delivers fuel to the engine during the pressure strokes. The start of injection of fuel during each pressure stroke of the pump piston, related to the engine shaft, is adjustable by means which may be acted upon by a hydraulic fluid. The latter is admitted through a check valve and is opposed by a return force affecting said means. The hydraulic circuit which controls said fluid is provided, downstream of said check valve, with a bypass channel controlled by a discharge valve.

In a known adjusting device of the aforenoted type (such as disclosed in German Pat. No. 1,155,290), the bypass channel is controlled by means of a plunger which simultaneously serves as the control piston of a hydraulic servo control circuit containing a setting piston for adjusting the cam ring of the fuel injection pump. A servo system of this type which is designed as a follower control and which operates with two pistons displaceable against two springs, is relatively complex and expensive.

By means of adjusting devices of the aforenoted type it is achieved that the beginning of the injection occurs independently of the fuel quantity to be injected during each pressure stroke of the pump piston. Such adjusting devices further ensure by means of a temporary hydraulic lock that the cam ring is not reset by the force exerted thereon by the pump piston during its pressure stroke.

In the aforenoted known adjusting device, the displacement of the means for changing the timing, i.e., the beginning of the injection, is dependent of the rpm of the fuel injection pump, since the hydraulic fluid pressure which exerts a force on the aforenoted plunger, is controlled in an rmp-dependent manner.

OBJECT AND SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved adjusting device of the aforenoted type wherein the beginning of the injection may be set independently of the rpm in an arbitrary manner.

Briefly stated, according to the invention, the movable valve member of the discharge valve controlling the bypass channel is actuated by an electromagnet. In order to ensure that, as long as the discharge valve is open, there is no admission of hydraulic fluid (which would be immediately discharged in any case), the electromagnet, simultaneously with the unseating (opening) of the discharge valve, causes the aforenoted check valve to close.

The invention will be better understood as well as further objects and advantages will become more apparent from the ensuing detailed specification of a preferred, although exemplary embodiment, taken in conjunction with the sole FIGURE showing the embodiment in longitudinal section.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In an only partially shown housing 1 of a fuel injection pump, there is threadedly held a hollow support plug 2 containing the adjusting device according to the invention. O-rings 3 provide a hermetic seal for the device. Hydraulic fluid, which may be fuel, is supplied to the adjusting device from a tank 4 through a conduit 6 by means of a delivery pump 5. The pressure and the suction side of the pump 5 are interconnected by means of a conduit 7 which contains a pressure control valve 8.

First, the fuel passes through a filter 10 into a pressure chamber 11 which is in communication with a control chamber 13 by means of a port 12. The circular opening of the port 12 at the control chamber 13 is defined by a valve seat 12a, with which there is associated a check valve sphere 14 disposed in he control chamber 13.

From the control chamber 13 there extends a lateral port 15 into an annular channel 15' which communicates with a conduit 16 through a bore 15" provided in the plug 2. The hydraulic pressure in the conduit 16 regulates an adjusting member generally indicated at 17. As it will become more apparent hereinafter, with the adjusting member 17 the timing of the injection may be adjusted. The adjusting member 17 includes a cylinder 18, an associated, hydraulically operated, reciprocating piston 19, a piston rod 20 affixed to said piston and a return spring 21. The piston rod 20 is connected with the cam ring (not shown) of the fuel injection pump for causing angular displacements thereof.

The control chamber 13 is further provided with a two-part discharge channel 22 which communicates with a discharge conduit 23 extending to the fuel tank 4. The opening of the discharge bore 22 at the control chamber 13 is defined by a valve seat 22a associated with a discharge valve sphere 24 disposed in the control chamber 13. The valve sphere 24 may be unseated from the outlet side by means of the armature 25 of an electromagnet. As the sphere 24 is unseated, it urges the sphere 14 into the valve seat 12a. Conversely, as long as the armature 25 exerts no unseating force on sphere 24, the sphere 14 is unseated by the force exerted by the fluid present in pressure chamber 11 and presses the sphere 24 against the valve seat 22a. In this manner each sphere mutually serves for the other sphere as an abutment determining a maximum flow passage section. The resetting forces exerted on the piston rod 20 during the pressure stroke of the pump piston or pistons cause an increase of the pressure in the control chamber 13. As a result, both spheres 14 and 24 are pressed into their respective seat 12a, 22a, so that a hydraulic lock is obtained which blocks any further displacement of the piston rod 20 in response to the resetting forces.

The armature 25 of the electromagnet is maintained in its position shown in the Figure, as long as the solenoid 26 is in an energized condition. As soon as the solenoid 26 is de-energized, the armature 25 is hydraulically displaced, the sphere 24 is unseated in the afore-described manner and thus, discharge bore 22 is opened. For effecting such hydraulic displacement of armature 25, the pressure chamber 11 is connected, through a channel 27, with a magnet chamber 28 from which hydraulic fluid under pressure is admitted to the radial face 25' through an annular clearance 30. The latter is defined by a peripheral wall portion of armature 25 and an inner wall portion of a bushing 29 carrying the solenoid 26. The armature portion which separates the magnet chamber 28 from the discharge bore 22 has a diameter larger than the diameter of the valve seats 12a or 22a. Thus, by virtue of the differences in the areas exposed to opposed forces, during the de-energized condition of the solenoid 26, the armature 25 holds the spheres 14, 24 in a position in which the bore 12 is closed by the sphere 14.

The electromagnet is operated by means of an electronic regulating apparatus, not shown, which, dependent upon the rpm, load or other variables characterizing the operation of the engine, ensures that the actual moment of the beginning of the injection is matched with the ideal moment, related to the shaft of the internal combustion engine. Thus, as long as the said electronic apparatus maintains the solenoid 26 in a de-energized condition, the sphere 24 is unseated and the sphere 14 is seated. As a result, the piston rod 20 and the piston 19 of the setting member 17 are displaced by the return spring 21 in the "-" direction because no communication exists between the pressurized conduit 6 and the conduit 16 and further, because the control chamber 13 is de-pressurized through channel 22 and conduit 23. As soon as the solenoid 26 is energized and, as a result, the armature 25 moves away from the sphere 24, the pressure prevailing in the pressure chamber 11 lifts the sphere 14 from its seat 12a and presses the sphere 24 against its seat 22a. Consequently, fuel under pressure may flow into the control chamber 13. The pressure prevailing therein is transmitted through ports 15, 15" to conduit 16. The said pressure overcomes the force of the return spring 21 and thus moves the piston 19 and piston rod 20 in the "+" direction. It is noted that "+" means a shift in the timing to an earlier moment whereas "-" means a shift to a later moment.

Independently of the fact whether the solenoid 26 is energized or is de-energized, that is, independently of the position assumed by the spheres 14 and 24, the spheres are each urged against their associated seat by any resetting force exerted on the rod 20 in the "-" direction. In this manner a hydraulic lock is generated that prevents the piston 19 and the rod 20 from moving in the "-" direction. Thus, no resetting of the cam ring may take place in response to the aforenoted resetting forces.

The precedingly outlined "hydraulic lock" may be explained in more detail as follows.

The valve device comprising the check valve ball 14 and the discharge valve ball 24 is capable to prevent the motion of the piston 19 in the "-" direction in response to random forces exerted on the rod 20. As a result of such forces a fluid pressure is generated in the ports 15", 15 and control chamber 13 which is greater than either the fluid pressure upstream of the check valve 14 or the force of the armature 25 (in case the solenoid 26 is de-energized and the armature is urged downwardly by the pressure in the chamber 28) on the discharge valve ball 24.

Consequently, if the solenoid 26 is in an energized condition, then the discharge valve ball 24 is urged against its valve seat by the check valve ball 14, while port 12 is open. If now an external force exerted on the rod 20 tends to move the piston 19 towards the right, ("-" position), the check valve ball 14, by virtue of the pressure surge in chamber 13 in response to the said external force, is pressed against the valve seat 12a. The discharge valve ball 24 was seated originally by the valve ball 14 and is now maintained in that position by the pressure in chamber 13. Thus, to the right of the piston 19 there is a hydraulic lock preventing the piston 19 to move in that direction.

If, on the other hand, the solenoid 26 is in a de-energized condition, then the armature 25 is pressed against the discharge valve ball 24 by virtue of the pressure in the chamber 28, whereupon the check valve ball 14 is pressed against its seat 12a, while the discharge valve ball 24 opens the port 22. If now an external force is applied to the control rod 20, which tends to urge the piston 19 towards the right, the pressure surge generated in the chamber 13 will move the discharge valve ball 24 against the force exerted by the armature 25 and thus the ball 24 will be seated. The check valve ball 14 has been originally seated by the ball 24 and now both balls 14 and 24, as in the previously discussed situation, are urged against their respective valve seat so that again, a hydraulic lock is obtained.

It is apparent from the foregoing two paragraphs that regardless whether the solenoid 26 is energized or de-energized, the effect of a force on the rod 20 will be the same: both balls 14 and 24 will be pressed against their respective seat. Stated differently, no matter in what position does a pressure surge in the chamber 13 find the valve balls 14 and 24, upon occurrence of such a surge, that ball which in the momentary position of the valve device is not pressed against its seat, will be seated and thus a hydraulic lock to the right of the piston 19 will be obtained.

It is an additional advantage of the hydraulically and electromagnetically actuated armature structure and the associated seat-type valve that the setting frequency may be higher than in devices of the prior art. Further, by using spheres as movable valve members, a particularly good seal between the movable valve member and its seat is obtained.

Claims

What is claimed is:

1. In a device for adjusting the timing of a fuel injection pump associated with an internal combustion engine, said device being of the known type that includes (A) a movable adjusting member to effect a change in said timing, (B) conduit means carrying hydraulic fluid under pressure to said adjusting member for causing displacement thereof in one direction, (C) means exerting a force to said adjusting member in a second, opposite direction, (D) a check valve contained in said conduit means and including a movable valve member openable towards said adjusting member, (E) bypass channel means communicating with said conduit means downstream of said check valve and upstream of said adjusting member, and (F) a discharge valve including a movable valve member opening and closing said bypass channel means, the improvement comprising,

A. an electromagnet operatively connected with the movable valve member of said discharge valve to cause opening or closing of said bypass channel and

B. means operatively connecting said electromagnet with the movable valve member of said check valve to cause closing thereof upon opening of said discharge valve.

2. In a device for adjusting the timing of a fuel injection pump associated with an internal combustion engine, said device being of the known type that includes (A) a movable adjusting member to effect a change in said timing, (B) conduit means carrying hydraulic fluid under pressure to said adjusting member for causing displacement thereof in one direction, (C) means exerting a force to said adjusting member in a second, opposite direction, (D) a check valve contained in said conduit means and including a movable valve member openable towards said adjusting member, (E) bypass channel means communicating with said conduit means downstream of said check valve and upstream of said adjusting member, and (F) a discharge valve including a movable valve member opening and closing said bypass channel means, the improvement comprising, an electromagnet operatively connected with the movable valve member of said discharge valve to cause opening or closing of said bypass channel, said electromagnet including a reciprocable armature being movable in a first direction by the fluid pressure prevailing in said conduit means upstream of said check valve, said armature being movable in a second, opposite direction upon energization of said electromagnet, said armature being operatively connected with the movable valve member of said discharge valve to open the same when said armature is moved in said first direction upon de-energization of said electromagnet.

3. In a device for adjusting the timing of a fuel injection pump associated with an internal combustion engine, said device being of the known type that includes (A) a movable adjusting member to effect a change in said timing, (B) conduit means carrying hydraulic fluid under pressure to said adjusting member for causing displacement thereof in one direction, (C) means exerting a force to said adjusting member in a second, opposite direction, (D) a check valve contained in said conduit means and including a movable valve member openable towards said adjusting member, (E) bypass channel means communicating with said conduit means downstream of said check valve and upstream of said adjusting member, and (F) a discharge valve including a movable valve member opening and closing said bypass channel means, the improvement comprising,

A. an electromagnet operatively connected with the movable valve member of said discharge valve to cause opening or closing of said bypass channel and

B. an electronic regulating device emitting command signals to said electromagnet for matching the actual position of said adjusting member with the ideal position thereof, said actual position depends upon at least one variable characterizing the operation of said internal combustion engine.

4. An improvement as defined in claim 1, including

A. a chamber in continuous hydraulic communication with said adjusting member,

B. a first opening provided in said chamber for establishing communication between said chamber and a source supplying said hydraulic fluid under pressure,

C. a first valve seat defining said first opening,

D. a first sphere disposed in said chamber and associated with said first valve seat, said first sphere constitutes the movable member of said check valve,

E. a second opening provided in said chamber for establishing communication between said chamber and said bypass channel means,

F. a second valve seat defining said second opening, and

G. a second sphere disposed in said chamber and associated with said second valve seat, said second sphere constitutes the movable member of said discharge valve.

5. An improvement as defined in claim 4, wherein said spheres are cooperating in such a manner that, when said electromagnet exerts no opening force on said second sphere, said hydraulic fluid pressure unseats said first sphere whereby the latter displaces said second sphere pressing it into engagement with said second valve seat, and when said electromagnet exerts an opening force on said second sphere, the latter is unseated, thereby displacing said first sphere and pressing it into engagement with said first valve seat.

6. An improvement as defined in claim 5, wherein the fluid pressure in said chamber, when greater than the opening force exerted on said first sphere and greater than the opening force exerted on said second sphere, presses both spheres into their respective associated valve seats.