EP2464866B1 - High pressure pump - Google Patents

Description

State of the art

The invention relates to a high-pressure pump, in particular a radial or linear piston pump. Specifically, the invention relates to the field of fuel pumps for fuel injection systems of air-compression, self-igniting internal combustion engines.

Disclosure of the invention

From the DE 102004002487 or DE 10 2005 046 670 A1 a high-pressure pump for a fuel injection device of an internal combustion engine is known. The known high-pressure pump has a pump housing, in which a pump element is arranged, which comprises a driven by a drive shaft in a stroke pump piston. The pump piston is slidably guided in a cylinder bore of a part of the pump housing and limited in this one pump working space. The pump piston is supported indirectly via a hollow cylindrical plunger on the drive shaft, wherein the plunger is slidably guided in a bore of a part of the pump housing in the direction of the longitudinal axis of the pump piston.

The known high pressure pump has the disadvantage that a certain height is required for the plunger body to ensure reliable guidance in the pump housing in the direction of the longitudinal axis of the pump piston. This affects the size of the high-pressure pump. Furthermore, further components are required, in particular a support element which is inserted in the ram in the drive shaft facing end portion to support the roller. The pump piston is connected via a spring plate, on which a plunger spring is supported, with the plunger body.

Disclosure of the invention

The high pressure pump according to the invention with the features of claim 1 has the advantage that a compact design of the pump assembly is possible and thus the space required for the high-pressure pump space is reduced. Specifically, an embodiment of the pump assembly can be simplified.

According to the invention, the roller tappet in at least one support region, in which the roller tappet is supported radially in the bore of the housing part, is configured to be bulbous. The bulbous configuration can be achieved for example by grinding the roller tappet on its outside. Specifically, the roller tappet on the support area can be ground spherical. Due to the small lever arm between the axis of rotation of the roller and the support point of the roller tappet, a bending moment between the roller tappet and the pump piston with respect to the connection of the roller tappet with the pump piston, which takes place via the spring plate, be kept sufficiently small.

The roller tappet can be made relatively small, whereby the plunger spring designed weaker and also can be significantly reduced, since the plunger spring has less mass to carry with it. This can also be a significant weight savings, that is, a reduction in the mass of the components of the pump assembly, can be achieved, for example, is 50%. Reducing the plunger spring may also result in a reduction in the main dimension of a camshaft (drive shaft) to a cylinder head top. This advantage leads to further weight savings on the cylinder head and the pump housing. Based on the reduction and thus mass reduction of the roller tappet thus additional benefits.

Advantageously, the pump piston is designed substantially cylindrical. This can account for a piston foot on the pump piston. Specifically, the pump piston can be made from a rod material, with an optimally small diameter of the rod material being chosen to minimize a machining volume by turning and grinding.

It is also advantageous that the spring plate has at least one support extension which is guided along the main axis of the pump assembly laterally along the roller tappet and is on the roller beyond the roller tappet out, and that the support extension limits a side run of the roller along its axis of rotation. Specifically, it is advantageous that the spring plate has two support extensions, which are guided on opposite sides along the main axis of the pump assembly laterally on the roller tappet and stand on the roller on the roller tappet out and that the support extensions on both sides limit a side run of the roller along its axis of rotation , The support extensions can be configured according to two ears or lobes that protect the pump housing from the side run of the role and keep the role in its desired position. The resulting forces from the roller start to the support extensions can be transferred to the pump piston.

It is also advantageous that the pump piston has a piston foot, which faces the roller tappet, and that the spring plate engages behind the piston foot of the pump piston for connecting the pump piston with the spring plate. Characterized the pump piston is connected to the roller tappet, wherein the connection is effected by means of the spring plate. The pump piston can be supported with its piston foot on the roller tappet.

It is also advantageous that the cam or a drive shaft, on which the cam is provided, has at least one guide web associated with the cam, which limits a side run of the roller along its axis of rotation. Specifically, it is advantageous that two such guide webs are provided, which bound both sides of a side run of the roller along its axis of rotation. Such guide webs are preferably designed as circumferential and closed guide webs. Such guide webs take over the function of a support extension of the spring plate or the like, so that simplifies the design of the pump assembly. In addition, there is the advantage that the roller can not rotate, as it is guided directly on a cam track of the cam. Thus, the leadership of the role and the support against rolling start of the camshaft, that is, the cam or the drive shaft, are taken over. This also results in the advantage that the spring plate is very simple, so that the total weight of the moving masses, in particular the mass of the plunger body and other connected to the plunger body components, is optimized. In this way, a force and thus a size of the plunger spring can be further reduced.

Brief description of the drawings

• Fig. 1 eine Hochdruckpumpe in einer auszugsweisen, schematischen, axialen Schnittdarstellung entsprechend einem ersten Ausführungsbeispiel der Erfindung;
• Fig. 2 einen auszugsweisen Schnitt durch die in Fig. 1 dargestellte Hochdruckpumpe entlang der mit II bezeichneten Schnittlinie;
• Fig. 3 einen auszugsweisen Schnitt durch die in Fig. 1 dargestellte Hochdruckpumpe entlang der mit III bezeichneten Schnittlinie;
• Fig. 4 eine auszugsweise Darstellung der in Fig. 1 gezeigten Hochdruckpumpe entsprechend einem zweiten Ausführungsbeispiel der Erfindung und
• Fig. 5 eine auszugsweise Darstellung der in Fig. 1 gezeigten Hochdruckpumpe entsprechend einem dritten Ausführungsbeispiel der Erfindung.

Preferred embodiments of the invention are explained in more detail in the following description with reference to the accompanying drawings, in which corresponding elements are provided with corresponding reference numerals. It shows:

• Fig. 1 a high-pressure pump in a partial, schematic, axial sectional view according to a first embodiment of the invention;
• Fig. 2 an excerpted section through the in Fig. 1 illustrated high pressure pump along the designated II section line;
• Fig. 3 an excerpted section through the in Fig. 1 illustrated high pressure pump along the designated III section line;
• Fig. 4 an excerpt representation of in Fig. 1 shown high pressure pump according to a second embodiment of the invention and
• Fig. 5 an excerpt representation of in Fig. 1 shown high pressure pump according to a third embodiment of the invention.

Embodiments of the invention

Fig. 1 shows a high-pressure pump 1 in a partial, schematic, axial sectional view according to a first embodiment. The high pressure pump 1 can be configured in particular as a radial or inline piston pump. Specifically, the high-pressure pump 1 is suitable as a fuel pump for fuel injection systems of air-compressing, self-igniting internal combustion engines. A preferred use of the high pressure pump 1 is for a fuel injection system having a fuel rail which stores diesel fuel under high pressure. However, the high-pressure pump 1 according to the invention is also suitable for other applications.

The high-pressure pump 1 has a pump housing which comprises one or more housing parts 2. In the housing part 2, a drive shaft 3 is arranged, which in the housing part 2 is stored. Here, the drive shaft 3 is rotatable about a rotation axis 4, wherein the drive can be effected by an internal combustion engine.

The drive shaft 3 has at least one cam 5. In this case, the cam 5 can also be configured as a multiple cam. Further, the cam 5 may be formed by an eccentric portion of the drive shaft 3 or the like. In the housing part 2, a pump assembly 6 is arranged, which is associated with the cam 5.

The pump assembly 6 has a main axis 7 which points at least approximately on the axis of rotation 4 of the drive shaft 3. The pump assembly 6 is arranged at least substantially in a bore 8 of the housing part 2. In this case, a cylinder head 9 is connected to the housing part 2. A projection 10 of the cylinder head 9 protrudes into the bore 8. The bore 8 is designed symmetrically with respect to the main axis 7. Furthermore, the projection 10 of the cylinder head 9 is designed symmetrically with respect to the main axis 7.

The pump assembly 6 also has a pump piston 11 which is guided in a bore 12 of the projection 11 along the main axis 7. The pump piston 11 defines a pump working space 13 in the bore 12. Via an inlet valve 14, fuel under a low pressure can flow into the pump working space 13 from a prefeed pump or the like when the pump piston 11 performs a suction stroke. During a delivery stroke of the pump piston 11, the high pressure fuel is delivered via an exhaust valve 15 to a fuel rail or the like.

In the bore 8, a roller tappet 20 is also arranged, which receives a roller 21. The roller tappet 20 is formed as a one-piece roller tappet part. In this case, on the one hand a support of the roller tappet 20 in a radial direction with respect to the main axis 7 in the bore 8 and on the other hand a reliable recording of the roller 21 of the roller tappet 20 is achieved. The roller 21 runs in operation on a cam surface 22 of the cam 5 from. As a result, a lifting movement caused by the cam 5 is transmitted via the roller 21 and the roller tappet 20 to the pump piston 11.

The pump assembly 6 has a spring plate 23 which is connected to the roller tappet 20. Here, the pump piston 11 is connected to the spring plate 23. In In this embodiment, the pump piston 11 is pressed into the spring plate 23. In addition, a plunger spring 24 is provided, which is supported on the one hand on the cylinder head 9 and on the other hand on the spring plate 23. Thus, the spring plate 23 is acted upon by the force of the plunger spring 24, namely in the direction of a suction stroke of a pump piston 11. Thus, during the reciprocation of the pump piston 11 ensures an advantageous power transmission, the roller 21 always in contact with the cam surface 22 and in contact with the roller tappet 20 stands.

In this embodiment, the pump piston 11, which is pressed into the spring plate 23, designed cylindrical. As a result, a cost-effective design of the pump piston 11, for example, from a rod material, possible.

The roller tappet 20 has on its outer side a support region 30. In the support region 30 of the roller tappet 20 is designed belly-shaped. This results in a bulbous support region 30 of the roller tappet 20, on which the roller tappet 20 comes into contact with the bore 8 in the radial direction with respect to the main axis 7. Here, the bulbous support portion 30 is configured so that a lever arm 31 between a rotation axis 32 of the roller 21 and a support point 33 between the bulbous support region (belly) 30 of the roller tappet 20 and the bore 8 of the housing part 2 is relatively small. Depending on the configuration, the lever arm 31 can also be negligibly small.

In operation, the roller tappet 20 is supported at the support point 33 on the bore 8, so that a transverse force occurs radially to the main axis 7 at the support point 33. The roller tappet 20 is not prevented from tilting in the bore 8. This results in a certain torque introduction via the spring plate 23 on the pump piston 11. However, the torque generated is sufficiently small, so that a reliable operation is ensured.

The lateral force to be supported occurs as a force component of the roller force, which is introduced perpendicular to the main axis 7 of the cam drive. With respect to a force applied by the cam 5 to the roller 21, the lateral force at normal cam pitches takes on a maximum of a quarter of the force applied by the cam force. The piston actuation force acting on the Pump piston 11 acts in the direction of the main axis 7, is therefore significantly greater than the transverse force component.

Ideally, the roller tappet 20 is guided in the bore 8, that the transverse force is introduced at least approximately at the height of the axis of rotation 32. This means that the lever arm 31 disappears. If this is not possible for reasons of space or the like, then a tilting moment is exerted on the roller tappet 20 by the transverse force support, which is supported by the pump piston 11. The larger the lever arm 31, the greater the tilting moment that occurs. For example, the lever arm 31 may be about 5 mm. At a cam engagement angle of 15 °, the tilting moment that occurs is smaller than the product of the force acting on the pump piston 11 in the direction of the main axis 7, the lever arm 31 of 5 mm and the tangent of 15 °. Thus, the occurring tilting moment is smaller than the product of the forces acting on the pump piston 11 in the direction of the main axis 7 and 1.25 mm.

For comparison, occurs in an eccentric polygon-based engine on the piston foot on a tilting moment, which is smaller than the product of acting in the direction of the main axis 7 on the pump piston 11 and force, for example, 2.5 mm.

Thus, it can be ensured by a suitable design of the pump assembly 6 that the strength of the pump piston 11 is sufficient even with a relatively small diameter of the pump piston 11 to accommodate the occurring tilting moment of the roller tappet 20. Specifically, the roller tappet 20 can be designed so that the point of force application does not move so far from the ideal point at the height of the axis of rotation 32 of the roller 21, that is, the lever arm 31 is relatively small.

Further, the torque acting on the pump piston 11 can be further reduced by an offset of the bore 12 of the lug 10 to the rotation axis 4 of the drive shaft 3. In this case, the main axis 7 of the pump assembly 6 is slightly past the axis of rotation 4 of the drive shaft 3.

Fig. 2 shows a partial representation of the in Fig. 1 shown high pressure pump 1 in a schematic sectional view along the section line designated II. The spring plate 23 has in this embodiment support projections 35, 36 which laterally on the roller tappet 20 along the main axis 7 of the pump assembly 6 extend. Here, the support extensions 35, 36 are guided laterally on both sides of the roller tappet 20, wherein these are on the side of the roller 21 on the roller tappet 20 addition. The support extension 35 has a stop surface 37. Furthermore, the support extension 36 has a stop surface 38. By the stop surfaces 37, 38 of the support extensions 35, 36 a possible side run of the roller 21 along the axis of rotation 32 of the roller 21 is limited. The support extensions 35, 36 can be designed like an ear.

Fig. 3 shows a partial representation of the in Fig. 1 shown high pressure pump 1 along the designated III cutting line. The roller tappet 20 has bores 39, 40, 41, 42, which also extend through the spring plate 23. About the holes 39 to 42, the bore 8 of the housing part 2 with an interior of the housing part 2, in which the drive shaft 3 is arranged, connected. The bores 39 to 42 serve as compensation bores 39 to 42. The compensation bores 39 to 42 serve to allow a flow of fuel. This avoids that takes place by the roller tappet 20, a compression of the fuel.

Fig. 4 shows a partial representation of the in Fig. 1 shown high-pressure pump 1 according to a second embodiment. The Indian Fig. 4 shown excerpts section corresponds to that in the Fig. 2 shown illustration along the in Fig. 1 executed with II designated cutting line. In this embodiment, the pump piston 11 has a piston foot 50. The piston base 50 has an end face 51, with which the pump piston 11 rests against the piston tappet 20 on its piston foot 50. Furthermore, the spring plate 23 on a collar 25. With the collar 52 of the spring plate 23 engages behind the piston 50 of the pump piston 11 to connect the pump piston 11 with the spring plate 23 and thus also with the roller tappet 20. The pump piston 11 is designed in this case tree-shaped. As a result, high strength of the pump piston 11 is ensured even with relatively large occurring transverse forces, which can lead to correspondingly large moments. The pump piston 11 can thus absorb tilting moments which act on the roller tappet 20. On the piston foot 50, which faces the roller tappet 20, the pump piston 11 is made thicker than on a cylindrical part 53. This results in a high stability of the pump piston 11.

In this embodiment, the spring plate 23 supporting extensions 35, 36. It is ensured by stop surfaces 37, 38 of the support extensions 35, 36, a two-sided limitation of the side run of the roller 21.

Fig. 5 shows the in the Fig. 1 shown high-pressure pump 1 in a partial representation according to a third embodiment. In this embodiment, guide webs 55, 56 are provided on the cam 5 or on the drive shaft 3, on which the cam 5 is provided. The guide webs 55, 56 are in this case associated with the cam 5 and thus the pump assembly 6. The guide webs 55, 56 are configured circumferentially. The guide web 55 has a circumferential, inner guide surface 57. The guide web 56 has a circumferential, inner guide surface 58. The guide surfaces 57, 58 face each other. The guide webs 55, 56 with the guide surfaces 57, 58 protrude in the radial direction beyond the cam surface 22 with respect to the rotation axis 4 of the drive shaft 3. The guide surfaces 57, 58 of the guide webs 55, 56 thereby limit a possible side run of the roller 21 along the axis of rotation 32 of the roller 21. Stützfortsätze 35, 36, as for example in the Fig. 2 and 4 are illustrated, can be omitted here. As a result, the mass of the moving parts of the pump assembly 6, in particular the mass of the spring plate 23, can be further reduced. This allows a further optimization of the pump assembly 6.

Thus, a height of the roller tappet 20 in the direction of the main axis 7 can be optimized.

The invention is not limited to the described embodiments.

Claims (7)

1. High-pressure pump (1), in particular radial or in-line piston pump for fuel injection systems of air-compressing, auto-ignition internal combustion engines, having at least one pump assembly (6) and having a drive shaft (3) which has at least one cam (5) assigned to the pump assembly (6), wherein the pump assembly (6) has a pump piston (11) which is guided in a bore (12), a roller (21) which runs on a cam surface (22) of the cam (5), and a roller tappet (20) which receives the roller (21), wherein the pump piston (11) is connected to the roller tappet (20) by way of a spring plate (23) on which a tappet spring (24) is supported, and wherein, in this way, tilting of the roller tappet (20) relative to a main axis (7) of the pump assembly (6) along which the pump piston (11) can be actuated is limited,
   characterized
   in that the roller tappet (20) is, in a bore (8) formed in at least one housing part (2), supported radially with respect to the main axis (7) of the pump assembly (6), and said roller tappet is of bulged form in at least one support region (30) in which the roller tappet (20) is supported radially in the bore (8) of the housing part (2), and in that the bulge (30) of the roller tappet (20) in the support region is designed such that a lever arm (31) between the axis of rotation (32) of the roller (21) and a support point (33) between the bulge (30) of the roller tappet (20) and the bore (8) of the housing part (2) amounts to at most approximately 5 mm.
2. High-pressure pump according to Claim 1, characterized
   in that the roller tappet (20) is formed at least from a roller tappet part (20), wherein the roller tappet part (20) receives the roller (21), and wherein the roller tappet part (20) is supported, radially with respect to the main axis (7) of the pump assembly (6), in the bore (8) of the housing part (2).
3. High-pressure pump according to Claim 1 or 2, characterized in that the pump piston (11) is pressed into the spring plate (23).
4. High-pressure pump according to one of Claims 1 to 3,
   characterized
   in that the spring plate (23) has at least one support projection (35, 36) which is led laterally along the roller tappet (20) along the main axis (7) of the pump assembly (6) and which, at the roller (21), projects beyond the roller tappet (20), and in that the support projection (35, 36) delimits a lateral movement of the roller (21) along its axis of rotation (32).
5. High-pressure pump according to one of Claims 1 to 4,
   characterized in that the pump piston (11) is of substantially cylindrical form.
6. High-pressure pump according to Claim 1 or 2, characterized in that the pump piston (11) has a piston foot (50) which faces toward the roller tappet (20), and in that the spring plate (23) engages behind the piston foot (50) of the pump piston (11) in order to connect the pump piston (11) to the spring plate (23).
7. High-pressure pump according to one of Claims 1 to 6,
   characterized
   in that the cam (5), or a drive shaft (3) on which the cam (5) is provided, has at least one guide web (55, 56) which is assigned to the cam (5) and which delimits a lateral movement of the roller (21) along its axis of rotation (32).

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