WO2021037445A1

WO2021037445A1 - Piston rod seal

Info

Publication number: WO2021037445A1
Application number: PCT/EP2020/070670
Authority: WO
Inventors: Daniel Döhler; Stephan Steinke; Robert Bock
Original assignee: Nidec Gpm Gmbh
Priority date: 2019-08-23
Filing date: 2020-07-22
Publication date: 2021-03-04
Also published as: US20220356884A1; CN114599885A; DE102019122718A1

Abstract

The invention relates to a controllable coolant pump (1) for internal combustion engines, having a pump housing (2), a drivable pump shaft (4) which is rotatably mounted in the pump housing (2), an impeller (5) which is arranged on a free end of the pump shaft (4) in a rotationally fixed manner, and a pressure difference-driven actuator which drives at least one piston rod (12) guided in a piston rod bore (13) of the pump housing (2), said piston rod having a control slide (7) held on the impeller-side end of the piston rod (12) and being guided in the piston rod bore (13) by means of a guide sleeve (14) which is part of a seal device (15) that seals a pump chamber from the pressure difference-driven actuator, said pump chamber guiding the coolant. The seal device (15) has two mutually spaced seal elements (234, 244), each of which is arranged on a respective end of the guide sleeve (14) and each of which has a static seal region (235, 245) that surrounds the periphery of the guide sleeve (14) and a dynamic seal region (237, 246, 248) that adjoins the static seal region (235, 245), wherein the dynamic seal region (237) of the first seal element (234) extends from the end face at the end remote from the impeller into the interior of the guide sleeve (14), and the dynamic seal region (237) tapers into the guide sleeve (14) axially towards the interior.

Description

Piston rod seal

The present invention relates to a controllable coolant pump for internal combustion engines with the features of the preamble of claim 1.

Controllable coolant pumps have a regulation to vary the cooling capacity. Such a regulation is known, for example, from patent specification DE 10 2005 062 200 B3. A valve slide has an outer cylinder that variably overlaps the outflow area of the impeller of the coolant pump. The valve slide is arranged on several piston rods which are slidably mounted in the pump housing. The position of the valve slide shows the coolant flow and thus the cooling performance. The piston rods are guided in a sealed piston guide in the pump housing. Sealing devices used for such a seal are known, for example, from the laid-open specification EP 2 722 567 A1. The sealing device has a bush-shaped base body which serves as a guide for the piston rod. A sealing element is attached to each end of the base body. The sealing elements have dynamic sealing sections which are designed as sealing lips. A disadvantage of this sealing device is that, in the case of low pressure differences, pressure support does not become effective and aged sealing components lead to leaks occurring.

It is therefore the object of the present invention to specify a controllable coolant pump with a piston rod guide which has a sealing device which always ensures a reliable seal even under load. This object is achieved by a controllable coolant pump with the features of claim 1.

Accordingly, a controllable coolant pump for internal combustion engines has a pump housing, a drivable pump shaft rotatably mounted in the pump housing, an impeller arranged non-rotatably on a free end of the pump shaft, and an actuator driven by a pressure differential that drives at least one piston rod guided in a piston rod bore of the pump housing, which drives a Has the impeller-side end of the piston rod held control slide is provided. The control slide is set up to variably cover an outflow area of the impeller, the piston rod being guided in the piston rod bore by means of a guide bushing which is part of a sealing device which seals a pump chamber carrying the coolant from the actuator driven by a differential pressure, whereby the sealing device is two spaced apart from each other Has sealing elements which are arranged on one end of the guide bush and each have a static sealing area surrounding the guide bush circumferentially and a dynamic sealing area adjoining the static sealing area, a first sealing element sealing a pressure chamber of the pressure differential driven actuator at the end of the guide bushing remote from the impeller a second sealing element seals the coolant-carrying pump chamber at the end of the guide bush near the impeller. The dynamic sealing area of the first sealing element extends into the interior of the guide bushing from the face at the end remote from the impeller and is designed to taper conically in the axial direction inward into the guide bushing. The dynamic sealing area thus provides a reliable seal for the pressure space. In the event that coolant enters the space between the sealing elements, the design can ensure that the first sealing element does not lift off the piston rod, but remains close to it and thus always provides a secure seal.

The dynamic sealing area of the first sealing element is preferably spaced apart from the inside of the guide bushing in the unloaded state. If the piston rod tilts in the bore, the dynamic range of the first sealing element follows the movement without losing the radially circumferential contact, in particular line contact with the piston rod. The design of the first sealing element can ensure that reliable sealing is ensured even if the piston rod tilts. The outside of the static sealing area of the first sealing element preferably lies against the inside of the piston rod bore in a sealing manner.

In a preferred embodiment, the static sealing area of the first sealing element has an annular elevation in the area of the end face of the sealing device, which is compressed during installation.

The dynamic sealing area of the second sealing element preferably extends from the end face of the guide bushing close to the impeller into the pump chamber and lies outside the guide bushing.

It is advantageous if the dynamic sealing area of the second sealing element on the inside rests securely on the piston rod when it is installed.

It is preferably provided that the outside of the static sealing area of the second sealing element rests in a sealing manner on the inside of the piston rod bore and that the dynamic sealing area adjoining the static sealing area is tapered at its end on the impeller side on its outside away from the guide bushing, thus ensuring can be that the second sealing element always rests radially circumferentially on the piston rod, in particular with line contact.

The dynamic sealing area of the second sealing element preferably has a sealing lip arranged on the inside, between the conical area of the second sealing element and the sealing lip an annular groove arranged concentrically to the unloaded piston rod is arranged at the end, which allows a movement in the radial direction of the sealing lip of the second sealing element and the allows conical area of the second sealing element independently of one another. It is advantageous if the second sealing element is pushed onto the guide bush and engages in an annular groove in the guide bush to fix the position. The two sealing elements are preferably designed to be rotationally symmetrical.

A drainage line is preferably arranged between the two sealing elements in the guide bushing.

The dynamic sealing areas are preferably designed as sealing lips.

The sealing elements preferably encompass the guide bush at least partially on the front side.

The guide bushing is preferably made from a thermoplastic material. The sealing device preferably has elastomer seals.

Furthermore, it is advantageous if the piston rod can be moved parallel to the pump shaft by means of the pressure difference-driven actuator. The actuator operated by a pressure difference can be a pneumatic or hydraulic drive. In a preferred embodiment, the actuator driven by a pressure difference is a pneumatic drive. The negative pressure space is preferably sealed by a rolling membrane, among other things. If the vacuum chamber is evacuated, the membrane rolls out due to the pressure difference between the atmospheric pressure and the vacuum area and moves a piston slide in which the piston rods are suspended.

A preferred embodiment of the invention is explained in more detail below with reference to the drawings. Components of the same type or having the same effect are designated by the same reference symbols in the figures. Show it:

Fig. 1: a longitudinal section through a controllable coolant pump with

Sealing device, as well

Fig. 2: a detailed view of a sealing device in longitudinal section,

3: an enlarged view of a guide bushing in FIG

Sealing device of FIG. 2 in longitudinal section and in a three-dimensional representation, FIG. 4: an enlarged view of a first sealing element in FIG

Sealing device of FIG. 2 in longitudinal section, as well as

FIG. 5: an enlarged view of a second sealing element in FIG

Sealing device of FIG. 2 in longitudinal section.

In FIG. 1, a controllable coolant pump 1 with a pump housing 2 is shown. In the pump housing 2, the pump shaft 4, which is driven by a drive wheel (not shown), is rotatably supported in a pump bearing 3. An impeller 5 is seated non-rotatably on the free, flow-side end of the pump shaft 4. The pump shaft 4 is surrounded by a mechanical seal 6 between the pump bearing 3 and the impeller 5. A pressure-actuated control slide 7 is arranged in the interior of the pump. The control slide 7 is pot-shaped with a central opening 8. It surrounds the pump shaft 4 concentrically. It has an annular base 9 and a jacket surface 10 surrounding the base 9 on the circumferential side. Depending on the position of the control slide 7, the lateral surface 10 covers the outflow area 11 of the impeller 5. The control slide 7 is firmly connected in the area of the base 9 to preferably three guide rods 12. The guide rods 12 extend parallel to the pump shaft 4 and are arranged evenly distributed over their circumference. The guide rods 12 are piston rods which are axially guided in piston rod bores 13 in the pump housing 2.

The piston rods 12 are driven by means of an actuator driven by a pressure difference, in this case a pneumatic drive that works with negative pressure. The piston rod 12 is guided on the control slide side in a guide bushing 14 in the piston rod bore 13. The guide bush 14 is part of a sealing device 15 with two sealing elements 16 each. The two sealing elements 16 are each arranged at one end of the guide bush 14. They are spatially separated from one another and do not influence one another. The sealing element remote from the impeller seals the vacuum chamber of the pneumatic drive and the sealing element close to the impeller seals the coolant-carrying pump chamber. A drainage line 17 arranged between the two sealing elements 16 can discharge a coolant that has penetrated into the space between the two sealing elements 16.

The piston rod 12 is held in a piston slide 18 on the negative pressure side. The piston slide 18 is arranged in a vacuum chamber 19, which has an enlarged inside diameter compared to the piston rod bore 13, in a piston slide receptacle in a roller diaphragm. The recordings of the piston slide 19 are thus connected to one another via the continuous rolling diaphragm. The vacuum space is sealed by the rolling diaphragm, which also accommodates the piston valve. The negative pressure area is sealed by axial compression of the rolling diaphragm in the housing and the seal 16 in contact with the piston rod. This area is connected to the vacuum supply of the vehicle with a hose nozzle pressed into the housing. If the vacuum chamber is evacuated, the membrane rolls out due to the pressure difference between the atmospheric pressure and the vacuum area and thus moves the piston slide in which the piston rods are suspended.

The control slide 7 can be moved between an open position and a closed position by means of the pneumatic drive. In the open position shown in FIG. 1, the outflow area 11 of the impeller 5 is free and not covered by the control slide 7. In the closed position, however, the control slide completely covers the outflow area.

In order to reduce tilting of the piston rod 12 in the pump housing 2 and a load on the sealing device 15, a second guide 20 of the piston rod 12 is provided in the pump housing 2. The second guide point 20 is formed by a through hole 21 between the piston slide receptacle 19 and the piston rod bore 13. The through hole 21 has a clear width which is smaller than the clear width of the piston slide receptacle 19 and piston rod bore 13. The clear width of the through hole 21 is matched to the outer diameter of the piston rod 12 with a little play. The cylindrical portion of the through hole 21 is to be designed as small as possible so that the risk of the guide rod 12 jamming in the through hole 21 is minimized. The piston rod 12 is thus only guided on the negative pressure side on the pump housing 2 and in the area of the sealing device 15 by means of a guide bush 15 in the pump housing 2. Due to the "two-point guide", even when force is exerted on the piston rod 12, tilting of the piston rod 12 is only possible to a limited extent. The sealing device 15 will age over the life of the pump, which reduces its ability to compensate for a piston rod deflection the compensatory capacity of the sealing device 15 does not have to be so high.

FIGS. 2 to 5 show in detail a preferred sealing device 15. The guide bushing 14 has a penetrating opening 22 which has a continuously widening inner diameter. The opening 22 is penetrated by the piston rod 12 in the assembled state. In the area of the smallest inner diameter, the piston rod 12 is guided in the guide bush 14. The guide bushing 14 is preferably manufactured from a thermoplastic by injection molding. To remove the finished plastic part from the injection mold, a draft bevel (also called a draft bevel) is preferably provided in the inside diameter, which means that the piston rod 12 is only guided on the smallest diameter of the guide bushing 14.

The guide bushing 14 has two sections 23, 24 which are each designed to receive a sealing element 16. The two sections 23, 24 are connected to one another by a central region 25 through which at least one radial opening 26 passes. In the exemplary embodiment shown, two radial openings 26 that are aligned with one another are provided. The outside diameter of the guide bushing 14 is significantly smaller in this central region 25 than the inside diameter of the piston rod bore 13, so that a circumferential recess 27 is formed on the outside of the guide bushing 14. The radial openings 26 form an inner drainage line and the circumferential recess 27 an outer drainage line. A coolant that has got into the guide bushing 14 can pass through the radial openings 26 can be derived radially outward into the recess 27 and discharged to the outside through the drainage line. Because of the circumferential recess 27, there is no need to pay attention to an accurate installation position of the sealing device 15. In the axial direction, however, attention must be paid to precise positioning in order to form the leakage system with the circumferential recess 27 of the guide bushing 14 and the leakage discharge bores in the pump housing 2, otherwise the areas 23 and 24 close the leakage system of the pump.

The section 23 of the guide bush 14 close to the impeller has a circumferential groove 241 which is delimited in the axial direction by two annular webs 242, 243. The inner web 243 has an outer diameter which, by overlapping with the piston rod bore 13, produces the press fit in the housing.

At the axial end 231 of the section 23 remote from the impeller, a pneumatic sealing element 234 is received for sealing against the pressure difference-controlled actuator or the vacuum chamber. The sealing element 234 shown in detail in FIG. 4 has a static sealing area 235 which surrounds the inside of the guide bush 14 on the circumference and which sits on the outside of the guide bush at the end 231. The outside of this static sealing area 235 rests against the inside of the piston rod bore 13. The static sealing area 235 engages around the end face of the end 231 of the guide bush 14 remote from the impeller and thus completely covers it. The end face formed in the installed position of the sealing device by means of the pneumatic sealing element 234 rests in the assembled state with a shoulder 28 of the piston rod bore 13, which is formed by the constriction to form the through hole 21. The radial overlap of the outer diameter of the pneumatic sealing element 234 with the piston rod bore ensures a static seal. Provision can also be made for the pneumatic sealing element 234 to have a circumferential bead (not shown) on the strut side, which is axially pressed during installation. The static sealing section 235 of the pneumatic sealing element 234 merges into a dynamic sealing section 237, which is designed as a sealing lip. The sealing lip 237 extends axially inward into the guide bushing 14. It protrudes in the radial direction inward from the inside of the guide bushing 14 and is tapered inside the guide bushing 14 in the direction of the pump chamber with the same wall thickness. In other words, the conicity is on the inside and the outside of the sealing lip 237. When the piston rod 12 is mounted, the dynamic sealing section 237 rests against the outside of the piston rod 12 in a sealing manner under radial prestress. The dynamic sealing section 237 is dimensioned in such a way that at least one third, in particular more than 40% of the height defined in the axial direction of the section 23 of the guide bushing 14, which extends from the leakage groove 25, is covered in the interior.

On the side of the sealing device 15 facing the actuator, there is negative pressure in the pump housing 2. On the other hand, atmospheric pressure prevails between the sealing elements 23, 24. Due to the pressure difference, the sealing lip 237 clings to the piston rod 12 on its inside. In the event that cooling liquid enters the space between the sealing elements 23, 24 and the pressure on the dynamic sealing section 237 increases from the inside, the dynamic sealing section 237 is pressed against the piston rod 12 and the tightness is increased. It can thus be prevented that the pneumatic sealing element 234 becomes leaky due to load.

A hydraulic sealing element 244 for sealing against the pump chamber is received in the groove 241 of the section 24 of the sealing device 15 close to the impeller. The sealing element 244 shown in detail in FIG. 5 has a static sealing area 245 which surrounds the guide bushing 14 on the circumference and which engages in the annular groove 241. The outside of the static sealing area 245 rests against the inside of the piston rod bore 13. The static sealing area 245 at least partially encompasses the end face of the guide bush near the impeller and merges into a dynamic sealing area 246 which extends outward in the axial direction over the guide bush 245 protrudes. The dynamic sealing area 246 extends inward in the radial direction and is designed as a sealing lip. The sealing lip 247 extends from the end face of the guide bush 14 close to the impeller into the pump chamber. It is thus outside the guide bushing 14. The sealing lip 247 is conical and tapering away from the guide bushing 14. It therefore hugs the piston rod 12 with its end close to the impeller. The inner diameter of the sealing lip 247 in this area is selected such that the hydraulic sealing element 244 rests securely on the piston rod 12. The pressure of the conveying medium on the hydraulic sealing element 244 presses the sealing lip 247 against the piston rod 12.

Claims

1. Controllable coolant pump (1) for internal combustion engines having a pump housing (2), a drivable pump shaft (4) rotatably mounted in the pump housing (2), an impeller (5) arranged in a rotationally fixed manner on a free end of the pump shaft (4) and a pressure differential driven Actuator which drives at least one piston rod (12) which is guided in a piston rod bore (13) of the pump housing (2) and which has a control slide (7) held on the impeller-side end of the piston rod (12), the control slide (7) being designed to to variably cover an outflow area (11) of the impeller (5), and wherein the piston rod (12) is guided in the piston rod bore (13) by means of a guide bush (14) which is part of a sealing device (15) which carries the coolant The pump chamber is sealed off from the actuator driven by a pressure difference, the sealing device (15) having two sealing elements (234, 244) which are spaced apart from one another and which on are arranged at one end of the guide bushing (14) and each have a static sealing area (235,245) surrounding the circumference of the guide bushing (14) and a dynamic sealing area (237,246,248) adjoining the static sealing area (235,245), a first sealing element (234 ) seals a pressure chamber of the actuator driven by the pressure difference at the end of the guide bushing (14) remote from the impeller and a second sealing element (244) seals the coolant-carrying pump chamber at the end of the guide bushing (14) near the impeller, characterized in that the dynamic sealing area (237) of the first sealing element ( 234) extends into the interior of the guide bushing (14) from the face at the end remote from the impeller, the dynamic sealing area (237) tapering axially inward into the guide bushing (14).

2. Controllable coolant pump according to claim 1, characterized characterized in that the dynamic sealing area (237) of the first sealing element (234) is spaced apart from the inside of the guide bushing (14) in the unloaded state.

3. Controllable coolant pump according to claim 1 or 2, characterized in that the outside of the static sealing area (235) of the first sealing element (234) lies against the inside of the piston rod bore (13) in a sealing manner.

4. Controllable coolant pump according to one of the preceding claims, characterized in that the static sealing area (235) of the first sealing element (234) has an annular elevation (236) in the area of the end face of the sealing device (15).

5. Controllable coolant pump according to one of the preceding claims, characterized in that the dynamic sealing area (246,247) of the second sealing element (244) extends from the impeller-near end of the guide bushing (14) into the pump chamber and is outside the guide bushing (14).

6. Controllable coolant pump according to one of the preceding claims, characterized in that the outside of the static sealing area (245) of the second sealing element (244) rests in a sealing manner on the inside of the piston rod bore (13) and that the dynamic sealing area (246) of the second sealing element ( 244) is designed at its end on the impeller side on its outside from the guide bushing (14) to taper conically in a conical region (246).

7. Controllable coolant pump according to one of the preceding claims, characterized in that the second sealing element (244) is pushed onto the guide bushing (14) and engages in at least one annular groove (241) of the guide bushing (14) to fix the position.

8. Controllable coolant pump according to one of the preceding claims, characterized in that between the two sealing elements (234,244) a drainage line is arranged in the guide bushing (14).

9. Controllable coolant pump according to one of the preceding claims, characterized in that the dynamic sealing areas (237,246) are designed as sealing lips.

10. Controllable coolant pump according to one of the preceding claims, characterized in that the sealing elements (234, 244) at least partially encompass the guide bushing (14) on the front side.