Pump, especially high-pressure fuel pump

Abstract

Pump, in particular high-pressure fuel pump, with at least one pump element (10) having a pump piston (12) driven in a stroke motion, which defines a pump working chamber (24) which can be connected to an inlet (28) via an inlet valve (26), wherein the inlet valve (26) has a valve member (38) which is movable between an open position and a closed position, wherein the valve member (38) is acted upon in the closing direction by a valve spring (52) which is supported on the valve member (38) via a support element (50), wherein the support element (50) comes into contact with a stop (58) to limit the movement of the valve member (38) in its opening direction, wherein the support element (50) and / or the stop (58) has at least one, preferably several, recesses (94) distributed over its contact surface (56; 60).96) having a reduced contact area between the support element (50) and the stop (58), wherein the at least one recess (94; 96) is hydraulically connected to a space (62) surrounding the support element (50), wherein the at least one recess is designed as a groove (94) extending at least approximately radially to the longitudinal axis (79) of the valve member (38), characterized in that the at least one recess is designed as a groove (96) extending in the circumferential direction of the support element (50) or the stop (58), wherein several grooves (94) extending at least approximately radially are provided, which are connected to each other by at least one groove (96) extending in the circumferential direction.

Description

State of the art

[0001] The invention relates to a pump, in particular a high-pressure fuel pump, according to the preamble of claim 1.

[0002] Such a pump, in the form of a high-pressure fuel pump, is known from DE 10 2004 013 244 A1. This pump has at least one pump element comprising a pump piston driven in a reciprocating motion, which defines a pump working chamber. The pump working chamber can be connected to an inlet for the pumped medium via an inlet valve. The inlet valve has a valve element that is movable between an open position and a closed position and is acted upon in the closing direction by a valve spring. The valve spring is supported on the valve element by a support element connected to the valve element. The support element abuts a stop to limit the stroke of the valve element in the opening direction. The valve element with the support element is surrounded by the pumped medium. The contact surfaces of the support element and the stop are flat.If the support element is in contact with the stop when the valve member is in the open position, and the valve member is to move from this open position to its closed position, the effect of so-called hydraulic sticking of the support element to the stop can occur. This makes it difficult for the support element to release from the stop and thus for the valve member to move in the closing direction. This impairs the dynamics of the valve member and consequently increases the switching times for its movement between its open and closed positions.

[0003] From DE 103 46 211 A1 a check valve, in particular for a high-pressure pump of a fuel injection device, is known, wherein the check valve has a valve housing inserted into a receptacle and a recess of the valve housing is connected to an annular space via a bore.

[0004] The patent application DE 10 2012 215 068 A1 discloses a cylinder head for a pump, in particular a high-pressure fuel pump, comprising an electromagnetically actuated inlet valve with a valve element that cooperates to control the connection of a pump working chamber with an inlet to a valve seat.

[0005] German patent application DE 10 2015 203 345 A1 discloses a pump, in particular a high-pressure fuel pump, with at least one pump element comprising a pump piston driven in a reciprocating motion, which defines a pump working chamber in a housing part of the pump. The pump element has an inlet valve through which the pump working chamber can be connected to an inlet for the pumped medium.

[0006] German patent application DE 10 2013 218 895 A1 proposes an inlet valve for a pump, in particular a high-pressure fuel pump, which has a valve housing and a piston-shaped valve element that is slidably guided within the valve housing. The valve element interacts with a valve seat at one end and projects into a valve chamber at its other end. The valve chamber is hydraulically connected to a relief chamber, with the valve element emerging from or entering the valve chamber at its end during the opening or closing movement. Disclosure of the invention Advantages of the invention

[0007] In contrast, the pump according to the invention with the features of claim 1 has the advantage that the dynamics of the movement of the valve element and thus its switching times are improved, since the effect of hydraulic sticking between the support element and the stop is avoided or at least weakened by the at least one recess.

[0008] Advantageous embodiments and further developments of the pump according to the invention are specified in the dependent claims. The embodiments according to claims 2 and 3 further reduce the effect of hydraulic sticking and thus further improve the dynamics of the inlet valve. The improvement in the dynamics of the inlet valve achievable with the embodiments according to claims 1 and 2 is particularly advantageous if the inlet valve can be actuated by means of an electromagnetic actuator as specified in claim 3 and short switching times of the inlet valve are required. drawing

[0009] An embodiment of the invention is shown in the drawing and explained in more detail in the following description. The drawing shows... Fig. 1. Partial view of a pump in a longitudinal section with an inlet valve, Fig. 2. Enlarged view of the pump's inlet valve, Fig. 3 a part of the inlet valve in a cross-section along line III-III in Fig. 2 and Fig. 4 the part of Fig. 3 according to a modified training. Description of the exemplary embodiment

[0010] In Fig. Figure 1 shows a simplified section of a pump, preferably a high-pressure fuel pump for a fuel injection system of an internal combustion engine. The pump has at least one pump element 10, which in turn has a pump piston 12 that is driven, at least indirectly, by a drive shaft 14 in a reciprocating motion. The drive shaft 14 has one or more cams 16 or eccentrics, via which the rotary motion of the drive shaft 14 is converted into the reciprocating motion of the pump piston 12. The pump piston 12 is supported on the cam 16 or eccentric of the drive shaft 14 by a tappet 18.

[0011] The pump element 10 has a housing 20 in which the pump piston 12 is tightly guided in a cylinder bore 22, the housing part 20 being hereinafter referred to as the cylinder head. With its end facing away from the drive shaft 14, the pump piston 12 defines a pump working chamber 24 in the cylinder bore 22. The pump working chamber 24 has a connection via an inlet valve 26, which may be an inlet check valve opening into the pump working chamber 24, to an inlet 28 through which the pump working chamber 24 is filled with fuel during the suction stroke of the pump piston 12, which is directed radially inwards towards the drive unit 14.The pump working chamber 24 also has a connection via an outlet valve 30, which is, for example, an outlet check valve opening out of the pump working chamber 24, to a drain 32 which can lead to a high-pressure accumulator 34 and through which fuel is displaced from the pump working chamber 24 during the delivery stroke of the pump piston 12 directed radially outwards from the drive device 14.

[0012] In Fig. Figure 2 shows an enlarged view of the inlet valve 26. The inlet valve 26 has a piston-shaped valve element 38, which has a stem 40 and an adjoining head 42 with an increased diameter. The valve element 38 is slidably guided by its stem 40 in a bore 44 in the cylinder head 20, which adjoins the cylinder bore 22. The bore 44 has a smaller diameter than the cylinder bore 22, and a valve seat 46 is arranged at the transition from the cylinder bore 22 to the bore 44. The head 42 of the valve element 38 is located in the pump working chamber 24 and has a sealing surface 48 that interacts with the valve seat 46. The end of the shaft 40 facing away from the head 42 protrudes from the bore 44 on the side of the cylinder head 20 facing away from the pump working chamber 24, and a support element 50 in the form of a spring plate is attached to it.A valve spring 52 is clamped between the support element 50 and the cylinder head 20, through which the valve member 38 is acted upon in the closing direction.

[0013] The support element 50 is, for example, pressed or screwed onto the stem 40 of the valve member 38. The support element 50 has a large-diameter collar 54 against which the valve spring 52 is supported, the diameter of the support element 50 decreasing from the collar 54 towards the cylinder head 20, for example with an approximately conical profile. The support element 50 has an end face 56 at its end facing the cylinder head 20.

[0014] The valve spring 52 is supported on the side facing away from the support element 50 against the cylinder head 20. The cylinder head 20 has a projection 58 arranged within the diameter of the valve spring 52, surrounding the bore 44, with an end face 60 facing the support element 50. The portion of the stem 40 of the valve member 38 projecting from the bore 44 is surrounded by an annular space 62, which is bounded radially outwards by a support element 86, which will be explained later. The inlet 28 opens into the space 62, and at least one, preferably several, inlet bores 66 lead from the space 62 into the bore 44, through which the pump working chamber 24 is connected to the space 62 when the inlet valve 26 is open.

[0015] The inlet valve 26 is preferably actuated by an electromagnetic actuator 70, which is controlled by an electronic control unit 72 depending on the operating parameters of the internal combustion engine being supplied. The electromagnetic actuator 70 has an annular magnetic coil 74, a magnetic core 76, and a magnetic armature 78. The electromagnetic actuator 70 is arranged on the side of the inlet valve 26 facing away from the pump working chamber 24. The magnetic core 76 and the magnetic coil 74 are arranged in an actuator housing 80, which can be attached to the cylinder head 20 of the high-pressure pump. The actuator housing 80 can be attached to the cylinder head 20, for example, by means of a screw ring 82 that overlaps it and is screwed onto an externally threaded extension 64 of the cylinder head 20.

[0016] The magnetic armature 78 is at least substantially cylindrical and is guided by its outer shell in a recess in the form of a bore 84 in a support element 86 arranged in the actuator housing 80 so as to move freely. The bore 84 in the support element 86 is at least approximately coaxial with the bore 44 in the cylinder head 20 and thus with the valve element 38.

[0017] The magnetic armature 78 has a central bore 88 arranged at least approximately coaxially with the longitudinal axis 79 of the magnetic armature 78, into which a return spring 90, arranged on the side of the magnetic armature 78 facing away from the valve element 38, projects and is supported on the magnetic armature 78. The return spring 90 is supported at its other end at least indirectly on the magnetic core 76, which has a central bore 92 into which the return spring 90 projects.

[0018] With the solenoid coil 74 de-energized, the return spring 90 presses the magnetic armature 78 towards the valve member 38, thereby holding the valve member 38 in its open position, in which its sealing surface 48 is located away from the valve seat 46. The movement of the valve member 38 in its opening direction is limited by the fact that the support element 50, with its end face 56, abuts the end face 60 of the extension 58 of the cylinder head 20. The extension 58 of the cylinder head 20 thus forms a stop that limits the stroke of the valve member 38 in its opening direction. The space 62 surrounding the support element 50 and the extension 58 of the cylinder head 20 is filled with fuel.

[0019] Furthermore, it is provided that at least one recess is present in the end face 56 of the support element 50 and / or in the end face 60 of the projection 58 of the cylinder head 20, by which the contact area between the support element 50 and the projection 58 is reduced. The at least one recess is located in a Fig. In the embodiment shown in Figure 3, the groove 94 is formed as a groove extending at least approximately radially to the longitudinal axis 79, preferably with several grooves 94 being arranged distributed around the circumference of the support element 50. The grooves 94 extend continuously in the radial direction from the stem 40 of the valve member 38 to the radially outer edge of the support element 50. When the valve member 38 is in its open position, the end face 56 of the support element 50 is in contact with the end face 60 of the projection 58, and when the valve member 38 moves into its closed position, fuel from the space 62 between the two end faces 56 and 60 can flow into the grooves 94, thereby preventing or at least reducing hydraulic adhesion between the two end faces 56 and 60.

[0020] During a Fig. The versions shown in section 4 are as described in Fig. 3. Several radial grooves 94 distributed around the circumference of the support element 50 are provided, as well as additional grooves 96 extending circumferentially around the support element 50 that connect the radial grooves 94 to each other. For example, a groove 96 extending around the entire circumference of the support element 50 may be provided.

[0021] The function of the electromagnetically actuated inlet valve 26 is explained below. During the suction stroke of the pump piston 12, the inlet valve 26 is open, with its valve element 38 in its open position, in which its sealing surface 48 is positioned away from the valve seat 46. The movement of the valve element 38 into its open position is caused by the pressure differential between the fuel inlet 28 and the pump working chamber 24 against the force of the valve spring 52. The solenoid coil 74 of the actuator 70 can be energized or de-energized. When the solenoid coil 74 is energized, the magnetic armature 78 is drawn towards the magnetic core 76 by the resulting magnetic field against the force of the return spring 90. When the solenoid coil 74 is de-energized, the magnetic armature 78 is pushed towards the inlet valve 26 by the force of the return spring 90.

[0022] During the delivery stroke of the pump piston 12, the actuator 70 determines whether the valve element 38 of the inlet valve 26 is in its open or closed position. With the solenoid coil 74 de-energized, the magnetic armature 78 is moved by the return spring 90 in the direction indicated by arrow B. Fig. 2 pressed, whereby the valve member 38 is pressed by the magnetic armature 78 against the valve spring 52 in the actuating direction B into its open position. The force of the return spring 90 acting on the magnetic armature 78 is greater than the force of the valve spring 52 acting on the valve member 38. In the actuating direction B, the magnetic armature 78 acts on the valve member 38, and the magnetic armature 78 and the valve member 38 are moved together in the actuating direction B. As long as the solenoid coil 74 is not energized, no fuel can be delivered into the high-pressure accumulator 34 by the pump piston 12; instead, fuel displaced by the pump piston 12 is returned to the fuel inlet 28. If fuel is to be delivered into the high-pressure accumulator 34 during the delivery stroke of the pump piston 12, the magnetic coil 74 is energized, so that the magnetic armature 78 moves towards the magnetic core 76 in an actuating direction opposite to the actuating direction B, as indicated by arrow A. Fig.2 is pulled. Thus, no force is exerted on the valve element 38 by the magnetic armature 78, whereby the magnetic armature 78 is moved in the actuating direction A by the magnetic field and the valve element 38 is moved into its closed position independently of the magnetic armature 78 due to the valve spring 52 and the pressure difference prevailing between the pump working chamber 24 and the fuel inlet 28 in the actuating direction A.

[0023] By opening the inlet valve 38 during the delivery stroke of the pump piston 12 by means of the electromagnetic actuator 70, the delivery rate of the high-pressure pump to the high-pressure accumulator 34 can be variably adjusted. If a low fuel delivery rate is required, the inlet valve 38 is held open by the actuator 70 for a large part of the delivery stroke of the pump piston 12, and if a high fuel delivery rate is required, the inlet valve 38 is held open only for a small part or not at all during the delivery stroke of the pump piston 12.

Claims

[1] Pump, in particular high-pressure fuel pump, with at least one pump element (10) having a pump piston (12) driven in a stroke motion, which defines a pump working chamber (24) which can be connected to an inlet (28) via an inlet valve (26), wherein the inlet valve (26) has a valve member (38) which is movable between an open position and a closed position, wherein the valve member (38) is acted upon in the closing direction by a valve spring (52) which is supported on the valve member (38) via a support element (50), wherein the support element (50) comes into contact with a stop (58) to limit the movement of the valve member (38) in its opening direction, wherein the support element (50) and / or the stop (58) has at least one, preferably several, recesses (94) distributed over its contact surface (56; 60).96) having a reduced contact area between the support element (50) and the stop (58), wherein the at least one recess (94; 96) is hydraulically connected to a space (62) surrounding the support element (50), wherein the at least one recess is designed as a groove (94) extending at least approximately radially to the longitudinal axis (79) of the valve member (38), ; characterized by , that the at least one recess is designed as a groove (96) extending in the circumferential direction of the support element (50) or the stop (58), wherein several grooves (94) extending at least approximately radially are provided, which are connected to each other by at least one groove (96) extending in the circumferential direction. [2] Pump according to claim 1, characterized by , that the cross-section of the support element (50) decreases from a region (54) on which the valve spring (52) is supported, towards the stop (58). [3] Pump according to claim 1 or 2, characterized by, that the inlet valve (26) can be actuated by means of an electromagnetic actuator (70) which has a magnetic armature (78) that can be coupled to the valve element (38).

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