JPH0575893B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a fuel injection pump for a supercharged diesel internal combustion engine, in particular a distribution injection pump, in which the inner chamber of the pump casing serves as a suction chamber. The inner chamber is supplied with fuel under a pressure that is controlled in dependence on the rotational speed, and a rotational speed regulator is housed in the inner chamber, in which a control unit connected to the discharge amount adjusting member is provided. The amount of lever travel is limited by the position of a full load stop that defines the maximum allowable full load displacement;
and a control device having a three-dimensional cam and a hydraulically operated adjusting piston directly engaged with the three-dimensional cam to move the three-dimensional cam, the cam surface of the three-dimensional cam being brought into contact with the full load stopper. traced by a cooperating transmission member, the adjusting piston resisting the force of the return spring pushing back the three-dimensional cam by a pressure controlled depending on the rotational speed of the fuel present in the inner chamber. Concerning formats that are operated on.

Prior Art This type of fuel injection pump (hereinafter simply referred to as injection pump) is known from the patent application published in the Federal Republic of Germany.
It is known from the specification No. 2847572. The pressure, which is controlled as a function of the speed of the fuel present in the interior of the injection pump, serves as a speed-dependent parameter for the loading of the regulating piston.
This allows for a space-saving arrangement of the control device. No additional speed adjustment elements are required. It is also possible to provide one common return spring for the three-dimensional cam and the adjusting piston. In short, the quantity correction in this injection pump is effected by hydraulic operation.

Problems to be Solved by the Invention There are difficulties in applying a technique for changing the counterpressure in the spring chamber depending on the boost pressure to this type of injection pump. This is because the division of the total displacement of the adjusting piston by the three-dimensional cam is determined by the pump pressure characteristics in the rotational speed range of this function. This is difficult to achieve if a relatively large displacement is required to change the counterpressure in the spring chamber depending on the boost pressure. Generally, obtaining this kind of bend in the characteristic curve requires a large amount of expense. This is because, for this purpose, the total displacement must be increased or else the spring strength must be varied, for example by using two springs, or the three-dimensional cam must be designed in steps. Moreover, it is extremely difficult to adjust the bending of the characteristic curve obtained in this way.

SUMMARY OF THE INVENTION It is therefore an object of the invention to provide a simple and space-saving injection pump in which a bend in the characteristic curve can be obtained by varying the effective surface of the regulating piston.

Means of the Invention for Solving the Problem A configuration of the invention provides that the adjusting piston accommodates an inner piston coaxial therewith, which piston is arranged in a piston chamber of the adjusting piston in two axial directions of the adjusting piston. It is arranged to be movable relative to the adjusting piston between the stoppers, and the adjusting piston is provided with a passage opening into the inner chamber of the pump casing, with the inner piston being arranged on the side facing the inner chamber. , loaded through the passage by the pressure of fuel present in the inner chamber;
and a stopper fixed to the casing is disposed opposite to the inner piston on the side opposite to the passage, and the inner piston is configured to collide with the stopper when the adjusting piston moves. be.

Effect In the first section of the displacement, the entire cross section of the adjusting piston acts against the return spring and as a function of the rotational speed of the characteristic curve of the first steep slope of the displacement. During its stroke movement, the inner piston hits a stop fixed to the casing and is supported, so that it is stationary with respect to the casing, so that under the influence of the fuel pressure the adjusting piston is fixed relative to the inner piston. be made to exercise. In that case, only the remaining annular surface, excluding the end surface of the inner piston, is loaded with fuel pressure. This corresponds to a change in spring strength. As a result, the first characteristic curve of the travel distance is followed by a curved second characteristic curve, and this second characteristic curve, which has a smaller slope than the first characteristic curve, becomes a function of the rotational speed. act.

The means recited in the dependent claim of claim 1
An advantageous embodiment of the injection pump according to paragraph 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The drawing shows a reciprocating piston distributing injection pump, which is essentially known from DE 28 47 572 A1. Therefore, the basic structure of this injection pump will not be explained here.

This injection pump 10 is for a supercharged diesel internal combustion engine. This injection pump 10 includes a pump casing 11 and a control device 12 attached to the pump casing 11.
The control device 12 serves to modify the position of the full-load stop 13 as a function of the rotational speed. In this case, the rotational speed-dependent pressure of the fuel present in the interior chamber 18 of the pump housing 11 serves as the rotational speed-dependent parameter. The full load stopper 13 is formed as a spherical end of a first arm 14a of a two-arm stopper lever 14, and a second arm of the stopper lever 14 has a two-arm shape.
The arm 14b is supported by a driven pin 15 which serves as a transmission member. The driven pin 15 is guided in a guide member 16 inserted into the wall of the pump casing 11 with a tight sliding contact that is impermeable to fuel. The driven pin 15 is connected to the three-dimensional cam 19 at its free end.
cooperates with an advantageously three-dimensional cam surface 17.

The interior chamber 18 is filled with fuel under pre-pump pressure which is controlled as a function of the rotational speed. This inner chamber also serves as the suction chamber for the injection pump.
It also houses a mechanical rotation speed adjuster 20.
Regarding the rotation speed regulator 20, the full load stopper 1
Only a stop lever 14 supporting 3 and pivotably mounted on an axle 21 fixed to the housing, and a clamping lever 22 supported on a full-load stop 13 are shown.

The three-dimensional cam 19 is integrally formed with the adjustment piston 23 that is movable in the direction of its own axis, and is, in short, a conical portion 2 that continues to the piston surface 24 of the adjustment piston.
5 forms the cam surface 17 in a particularly compact configuration. The adjusting piston 23 is held axially movably with its cylindrical surface 25a in a cylindrical bushing 26, which is press-fitted into the wall of the pump casing 11 in a replaceable manner. The cylindrical bushing 26 is open at both ends.
As seen in the drawings, a snap spring 27 or similar stop ring is inserted into its lower end. This snap spring connects the adjusting piston 23 to the inner chamber 18.
prevents it from sliding down.

The pressure of the fuel present in the interior chamber 18 acts as a speed-dependent parameter on the piston surface 24, so that the regulating piston 23 is adjusted in accordance with the controlled pressure as a function of the speed. The three-dimensional cam 19 is moved or moved against the return force of a return spring 28 supported on a cap 29 to a position where the hydraulic adjustment force and the return force of the return spring are balanced.

In a special embodiment, the adjusting piston 23 has in its piston chamber 30 an inner movable piston 31 coaxial with the adjusting piston 23 . The piston chamber 30 is provided on the opposite side of the adjusting piston 23 from the piston surface 24. The piston chamber 30 is open toward the upper end of the adjusting piston 32. A ring-shaped or plate-shaped axial stopper 3 is attached to this upper end.
2 is fixed, and against this axial stop the inner piston 31 impinges with its upper piston face in order to limit its stroke. The axial stop 32 has a central opening and forms an axial support for the return spring 28.

On the other side of the inner piston 31, the bottom 33 of the piston chamber 30 or the inserted ring 34 forms a lower axial stop of the piston 31. The inner piston 31 moves within the piston chamber 30 between the two stops 32, 34 relative to the adjusting piston 23. The distance of this relative movement can be adjusted, for example, by inserting a further separating ring 34 inside the piston chamber at least at one end of the inner piston 31.

The inner piston 31 is connected via a passage 35 provided in the adjusting piston 23 so as to open from the piston surface 24 of the adjusting piston 23 to the piston chamber 30.
It is loaded with a controlled fuel pressure depending on the rotational speed in the interior chamber 18. This passage 35 is designed as a central axial bore.

The inner piston 31 is on the side opposite to the passage 35,
Stopper 3 with adjustable stopper screw shape movement
It is located at 6. This stopper 36 is screwed into the casing. The inner piston 31, with its end face facing the stop 36, impinges upon the free end of the stop 36 at a predetermined stroke limit during the movement of the adjusting piston 23. The opening inside the axial stopper 32 has a size that does not prevent the free end of the stopper 36 from passing through.

A cam surface 17 is provided on the conical portion 25,
This cam surface 17 tapers in a substantially frustum shape in the direction in which the return spring 28 returns. The adjustment piston axial region supporting the cam surface 17 is effectively the piston surface 2.
4 and the piston chamber 30.

Due to the fuel pressure in the inner chamber 18, the inner piston 31 impinges on the axial stop 32 and is always held in the position shown.

Next, the operation of the illustrated control device will be explained.

The position of the full-load stopper 13 determines the position of the tightening lever 22 and thus of the ring slide that controls the permissible full-load injection quantity. This ring slide is a part of the injection pump and is attached to the tightening lever 22.
and a control lever (not shown).
The position of the full load stopper 13 is determined via the driven pin 15 by the shape of the cam surface 17 of the three-dimensional cam 19. The fuel pressure, which is controlled as a function of the rotational speed in the inner chamber 18, acts on the piston face 24 of the regulating piston 23 and also on the end face of the inner piston 31 facing the passage 35. inner piston 3
1 is supported by this force on the axial stop 32 and thus on the adjusting piston 23. In short, the fuel pressure acts on the entire surface corresponding to the cross section of the adjusting piston 23. The adjusting piston 23, together with the inner piston 31, moves without relative movement to the return spring 2.
It is moved against the action of 8. Driven pin 15
traces the cam surface 17, so that the stop lever 14 pivots following the cam surface 17 under the action of the adjusting spring 37, and the full-load stop 13 moves to the left in the drawing. This movement of the adjusting piston 23 and the inner piston 31 against the return spring 28 follows a first characteristic curve with a linear characteristic of the displacement as a function of the rotational speed. During this movement, the inner piston 31 moves to the stopper 3 at its upper end.
6, the characteristic curve bends. This is because the fuel pressure acting on the surface of the inner piston 31 is excluded from the force pushing back the return spring 28. This has the same effect as increasing the force of the return spring 28. This results in a second characteristic curve with a linear characteristic of the stroke as a function of the rotational speed. This second characteristic curve follows the first characteristic curve with a bend and has a relatively slight slope.

In short, with the injection pump described above, a curved characteristic curve can only be obtained by varying the effective surface of the regulating piston.

The invention further provides that the return spring 2 in the spring chamber
The possibility of varying the resistance pressure generated by 8 is revealed as a function of the boost pressure introduced into the chamber part 39 via the inlet 38 and acting on the free end face of the inner piston 31.

Effects of the Present Invention According to the injection pump of the present invention, a polygonal characteristic curve can be obtained only by changing the effective surface of the adjusting piston, so adjustment becomes easy. Furthermore, the final force of the return spring is low, which also reduces the load. Adjustment is made easy by moving the stopper, and the inner piston and adjustment piston 23
The amount of relative movement between is selected as desired by inserting the ring plate.

[Brief explanation of the drawing]

The drawing is a longitudinal sectional view of one embodiment of the present invention. DESCRIPTION OF SYMBOLS 10...Fuel injection pump, 11...Pump casing, 12...Control device, 13...Full load stopper, 1
4...stopper lever, 14a, 14b...arm,
15... Driven pin, 16... Guide member, 17... Cam surface, 18... Inner chamber, 19... Three-dimensional cam, 20... Rotation speed adjuster, 21... Shaft, 22... Tightening lever, 23... Adjusting piston, 24... Piston Surface, 25... Conical part, 25a... Cylindrical part, 26... Cylindrical push,
27...Snat spring, 28...Return spring, 2
9... Cap, 30... Piston chamber, 31... Piston, 32... Axial stopper, 33... Bottom, 34...
Separation ring, 35...passage, 36...stopper screw,
37...adjustment spring, 38...inlet, 39...chamber part.

Claims (1)

[Scope of Claims] 1. A fuel injection pump for a supercharged diesel internal combustion engine, which has an inner chamber 1 of a pump casing.
8 serves as a suction chamber, and this inner chamber 18
is supplied with fuel under pressure controlled depending on the rotation speed, and houses a rotation speed regulator 20, in which a control unit connected to the discharge amount adjusting member is supplied. The amount of movement of the lever is limited by the position of the full load stopper 13, which defines the maximum allowable full load displacement, and the three-dimensional cam 19 and the three-dimensional cam are directly connected to the three-dimensional cam in order to move it. A control device 12 is provided with an engaged hydraulically operated adjusting piston 23, in which the cam surface 17 of the three-dimensional cam 19 is traced by means of transmission elements 14, 15 cooperating with the full-load stop 13. and the adjustment piston 2
3 is operated against the force of a return spring 28 pushing back the three-dimensional cam 19 by a pressure controlled as a function of the rotational speed of the fuel present in the inner chamber 18; The piston 23 accommodates an inner piston 31 coaxial therewith, which piston 31 pushes the adjusting piston 23 between two axial stops 32, 34 of the adjusting piston 23 in a piston chamber 30 of the adjusting piston. The adjusting piston 23 is provided with a passage 35 that opens into the inner chamber 18 of the pump casing 11 , and the inner piston 31 is arranged so as to be movable relative to the inner chamber 18 . , is loaded through the passage 35 by the pressure of the fuel present in the inner chamber 18, and the inner piston 31 is
A stopper 36 fixed to the casing is disposed on the side opposite to the passage, and the inner piston 31 is configured to collide with the stopper 36 when the adjusting piston 23 moves. injection pump. 2. The adjustment piston 23 is formed integrally with the three-dimensional cam 19, and the cam surface 1 is formed in the axial direction of the three-dimensional cam 19 and tapered in a substantially wedge-shaped direction in the return direction of the return spring 28.
7. The fuel injection pump according to claim 1, comprising: 7. 3. Fuel injection pump according to claim 1, wherein the cam surface 17 extends in the axial region between the effective piston surface 24 of the adjusting piston 23 and the piston chamber 30. 4. Said passage 35 is formed as a central axial bore, which axial bore forms the effective piston face 24.
The fuel injection pump according to any one of claims 1 to 3, wherein the fuel injection pump extends from the piston chamber 30 to the piston chamber 30. 5. The piston chamber 30 in the adjusting piston 23 is open on the side opposite the effective piston surface 24 and has in its opening a ring 32, a plate or the like as an axial stop, which ring 32 one end of the return spring 28 is supported, and
The fuel injection pump according to any one of claims 1 to 4, wherein the inside of the return spring 28 is penetrated by a stopper 36 fixed to the casing. 6. The fuel injection pump according to any one of claims 1 to 5, wherein the stopper 36 fixed to the casing is movably adjustable. 7. The other axial stop for the inner piston 31 is formed by the bottom 33 of the piston chamber 30 itself or by a ring 34, plate or the like inserted into the piston chamber 30
6. The fuel injection pump according to any one of items 6 to 6. 8. Any one of claims 1 to 7, in which the relative axial movement path between the adjusting piston 23 and the inner piston 31 is adjustable.
The fuel injection pump described in section. 9. Claims 5 to 8, in which a separating ring 34 is arranged between the inner piston 31 and its axial stop on at least one end face side of the inner piston 31. The fuel injection pump according to any one of the preceding items.