CN114599885A

CN114599885A - Piston rod seal

Info

Publication number: CN114599885A
Application number: CN202080073985.4A
Authority: CN
Inventors: D·德赫勒; S·斯坦克; R·博克
Original assignee: Nidec GPM GmbH
Current assignee: Nidec GPM GmbH
Priority date: 2019-08-23
Filing date: 2020-07-22
Publication date: 2022-06-07
Also published as: WO2021037445A1; DE102019122718A1; US20220356884A1

Abstract

The invention relates to a controllable coolant pump (1) for an internal combustion engine, 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 non-rotatably at the free end of the pump shaft (4), and a differential pressure drive actuator which drives at least one piston rod (12), which piston rod (12) is guided in a piston rod bore (13) of the pump housing (2), which piston rod has a control slide (7) which is held on the impeller side of the piston rod (12) and is guided in the piston rod bore (13) by means of a guide bushing (14), which guide bushing (14) is part of a sealing device (15), which sealing device (15) seals a pump chamber which conveys coolant from the differential pressure drive actuator, the pump chamber guiding the coolant. The sealing arrangement (15) has two sealing elements (234, 244) which are spaced apart from one another and are each arranged at one end of the guide bushing (14) and have a static sealing region (235, 245) which surrounds the circumference of the guide bushing (14) and a dynamic sealing region (237, 246, 248) which adjoins the static sealing region, wherein the dynamic sealing region (237) of the first sealing element (234) extends from the end face remote from the impeller end into the interior of the guide bushing (14), and the dynamic sealing region (237) tapers axially inwardly into the guide bushing (14).

Description

Piston rod seal

The invention relates to a controllable coolant pump for an internal combustion engine, having the features of the preamble of claim 1.

The controllable coolant pump has a control system for varying the cooling capacity. Such a control system is known, for example, from patent specification DE 102005062200B 3. The slide valve has an outer barrel which variably covers the discharge area of the coolant pump impeller. The slide valve is arranged on a plurality of piston rods which are movably mounted in the pump housing. The position of the slide valve reflects the flow rate of the cooling liquid and thus the cooling capacity. In the pump housing, the piston rod is guided in a sealing piston guide. Sealing devices for such seals are known, for example, from publication EP 2722567 a 1. The sealing device has a bushing-like base body which serves as a guide for the piston rod. In various cases, a seal is attached to one end of the base. The seal has a dynamic sealing portion designed as a sealing lip. One disadvantage of this seal is that the pressure support is not effective at low differential pressures and the aged seal components can cause leakage to occur.

It is therefore an object of the present invention to provide a controllable coolant pump with piston rod guidance, which has a sealing device which ensures reliable sealing at all times even under load.

This object is achieved by a controllable coolant pump having the features of claim 1.

Accordingly, a controllable coolant pump for an internal combustion engine is provided, having: the pump comprises a pump housing, a drivable pump shaft which is rotatably mounted in the pump housing, an impeller which is non-rotatably arranged on the free end of the pump shaft, and a differential pressure drive actuator which drives at least one piston rod which is guided in a piston rod bore of the pump housing and has a control slide which is held at the impeller-side end of the piston rod. The pilot spool is arranged to variably cover an outflow region of the impeller, and the piston rod is guided in the piston rod hole by a guide bush which is a part of a sealing device that seals a pump chamber that delivers the coolant from the differential pressure driven actuator. The sealing arrangement has two sealing elements spaced apart from one another, each sealing element being arranged at one end of the guide bush and each sealing element having a static sealing region around the circumferential side of the guide bush and a dynamic sealing region adjoining the static sealing region, a first sealing element sealing the pressure chamber of the differential-pressure-driven actuator at the end of the guide bush remote from the impeller and a second sealing element sealing the pump chamber conveying the cooling liquid at the end of the guide bush close to the impeller. The dynamic sealing region of the first seal extends from an end face remote from the end of the impeller into the interior of the guide bushing and tapers in the axial direction inwardly into the guide bushing. Thus, the dynamic sealing region provides a reliable seal for the pressure chamber. This design ensures that the first seal does not disengage from the piston rod but remains sealingly close to the piston rod if cooling liquid enters the space between the seals, thereby always providing a safe seal.

Preferably, the dynamic sealing region of the first seal is spaced from the inside of the guide bush in an unloaded condition.

If the piston rod is tilted in the bore, the dynamic area of the first seal follows this movement instead of losing radial circumferential contact, in particular line contact, with the piston rod. The design of the first seal ensures that a reliable seal is maintained even if the piston rod is tilted.

Preferably, the outer side of the static sealing region of the first seal is in sealing contact with the inner side of the piston rod bore.

In a preferred embodiment, the static sealing area of the first sealing element has an annular projection in the area of the end face of the sealing device, which projection is pressed during mounting.

Preferably, the dynamic sealing region of the second seal extends into the pump chamber from an end face of the guide bush adjacent the impeller and is located outside the guide bush.

Advantageously, the dynamic sealing region of the second seal is firmly seated on the inside against the piston rod during installation.

Preferably, the outer side of the static sealing area of the second seal is in sealing contact with the inner side of the piston rod bore, and the dynamic sealing area adjoining this static sealing area is at its end on the impeller side, the outer side of which tapers away from the guide bushing to ensure that the second seal is always in radial circumferential contact, in particular linear contact, with the piston rod.

Preferably, the dynamic sealing region of the second seal has a sealing lip arranged on the inside, wherein an annular groove arranged coaxially with respect to the piston rod of the empty load is provided between the conical region of the second seal and the sealing lip on the end face, which annular groove allows the sealing lip of the second seal and the conical region of the second seal to move independently of one another in the radial direction.

Advantageously, the second seal is pushed onto the guide bush and engages the annular groove of the guide bush to secure the position. Preferably, the two seals are rotationally symmetrical.

Preferably, a discharge outlet is provided in the guide bushing between the two seals.

Preferably, the dynamic sealing region is designed as a sealing lip.

Preferably, the seal at least partially surrounds the guide bush on the end face.

Preferably, the guide bushing is made of a thermoplastic material. Preferably, the sealing means has an elastomeric seal.

Furthermore, it is advantageous if the piston rod can be moved parallel to the pump shaft by a differential pressure drive actuator. The differential pressure driven actuator may be a pneumatic actuator or a hydraulic actuator. In a preferred embodiment, the pressure differential driven actuator is a pneumatic actuator. Preferably, the vacuum chamber is sealed by a rolling diaphragm or the like. If the vacuum chamber is evacuated, the diaphragm rolls out due to the pressure difference between the atmospheric pressure and the vacuum area and moves the piston slide on which the piston rod is suspended.

Preferred embodiments of the present invention are explained in more detail below with reference to the accompanying drawings. Similar or similarly acting components are denoted by the same reference numerals in the figures. Wherein:

FIG. 1: a longitudinal section through a controllable coolant pump with a sealing device, an

FIG. 2 is a schematic diagram: a longitudinal cross-sectional detail view of the sealing device,

FIG. 3: figure 2 is an enlarged view of the longitudinal section and spatial representation of the guide bushing of the sealing device,

FIG. 4: an enlarged longitudinal cross-sectional view of the first seal of the sealing device of fig. 2; and

FIG. 5: an enlarged longitudinal cross-sectional view of the second seal of the sealing device of fig. 2.

Fig. 1 shows a controllable coolant pump 1 with a pump housing 2. In the pump housing 2, a pump shaft 4 driven by a drive wheel (not shown) is rotatably mounted in a pump bearing 3. The impeller 5 is non-rotatably positioned at 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 valve 7 is arranged inside the pump. The pilot slide valve 7 is pot-shaped with a central opening 8. Which concentrically surrounds the pump shaft 4. The control slide 7 has an annular seat 9 and an outer lateral surface 10 which surrounds the seat 9 on the periphery. Depending on the position of the control slide 7, the outer lateral surface 10 covers the outflow region 11 of the impeller 5. In the region of the base 9, the control slide 7 is firmly connected to preferably three guide rods 12. The guide rods 12 extend parallel to the pump shaft 4 and are distributed uniformly over the circumference of the pump shaft 4. The guide rod 12 is a piston rod which is axially guided in a piston rod bore 13 in the pump housing 2.

The piston rod 12 is driven by a pressure difference driven actuator, which in this case is a pneumatic actuator operated with negative pressure. On the control valve side, the piston rod 12 is guided in a guide bushing 14 located in a piston rod bore 13. The guide bushings 14 are part of sealing devices 15, each sealing device 15 having two sealing elements 16. Two sealing elements 16 are arranged at one end of the guide bushing 14, respectively. They are spatially separated from each other and do not affect each other. The seal remote from the impeller seals the pneumatically driven vacuum chamber and the seal close to the impeller seals the pump chamber which delivers the cooling fluid.

The drain 17 disposed between the two seals 16 can drain the coolant that has permeated into the space between the two seals 16.

On the vacuum side, the piston rod 12 is held in the piston slide 18. In the vacuum chamber 19, the piston slide 18 is arranged in a piston slide receptacle in the rolling diaphragm, the inner diameter of the vacuum chamber 19 being larger than the diameter of the piston rod bore 13. The housing seats of the piston slide 19 are therefore interconnected by a continuous rolling diaphragm. The vacuum chamber is sealed by a rolling diaphragm which also houses a piston slide. The vacuum area is sealed by axial compression of the rolling diaphragm in the housing and a seal 16 in contact with the piston rod. The vacuum area is connected to the vacuum supply of the vehicle via a hose nozzle pressed into the housing. When the vacuum chamber is evacuated, the diaphragm rolls due to the pressure difference between the atmospheric pressure and the vacuum area, thereby moving the piston slider suspending the piston rod.

The control slide 7 is movable between an open position and a closed position by means of a pneumatic actuator. In the open position shown in fig. 1, the outflow region 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 region.

In order to reduce tilting of the piston rod 12 in the pump housing 2 and to reduce the load on the sealing means 15, a second guide 20 for 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 clear width of the through hole 21 is smaller than the clear width of the piston slide receptacle 19 and the piston rod bore 13. The clear width of the through hole 21 fits with a certain clearance to the outer diameter of the piston rod 12. The cylindrical portion of the through hole 21 should be designed as small as possible to minimize the risk of the piston rod 12 getting stuck in the through hole 21. The piston rod 12 is therefore guided only on the vacuum side on the pump housing 2 and in the region of the sealing device 15 by the guide bush 15 in the pump housing 2. Due to the "two-point guidance", the piston rod 12 can only be tilted to a limited extent even in the case of a force being applied to the piston rod 12. The sealing means 15 will age over the life of the pump, which reduces its ability to compensate for piston rod deflections. The two-point guidance reduces the radial deflection of the piston rod, so that the compensation capacity of the sealing device 15 does not have to be as high.

The preferred sealing means 15 is shown in detail in figures 2 to 5. The guide bushing 14 has an opening 22 therethrough having a continuously expanding inner diameter. In the assembled state, the opening 22 is penetrated by the piston rod 12. In the region of the smallest inner diameter, the piston rod 12 is guided in the guide bushing 14. The guide bushing 14 is preferably injection molded from a thermoplastic. In order to release the finished plastic part from the injection mold, a release bevel (also referred to as a lifting bevel) is preferably provided in the inner diameter, which results in the piston rod 12 being guided only at the smallest diameter of the guide sleeve 14.

The guide bushing 14 has two

parts

23, 24, each designed to receive a seal 16. The two

portions

23, 24 are connected to each other by a central area 25, the central area 25 being penetrated by at least one radial opening 26. In the embodiment example shown, two axial openings 26 are provided, aligned with each other. In this central region 25, the outer diameter of the guide bush 14 is significantly smaller than the inner diameter of the piston rod bore 13, so that a circumferential recess 27 is formed on the outside of the guide bush 14. The radial opening 26 forms an inner discharge opening and the circumferential recess 27 forms an outer discharge opening. The cooling liquid that has entered the guide bush 14 can be discharged radially outward through the radial opening 26 into the recess 27 and outwardly through the discharge outlet. Due to the circumferential recess 27, care does not need to be taken with regard to the exact mounting position of the sealing device 15. However, in the axial direction care must be taken to ensure accurate positioning in order to form a leakage system with the circumferential recess 27 of the guide bush 14 and the leakage discharge holes in the pump casing 2, otherwise the

areas

23 and 24 will close the leakage system of the pump.

The portion 23 of the guide bush 14 close to the impeller has circumferential grooves 241, each circumferential groove 241 being delimited in the axial direction by two

annular ribs

242, 243, respectively. The outer diameter of the internal ribs 243 create an interference fit in the housing by overlapping the piston rod bore 13.

At the axial end 231 of the portion 23 remote from the impeller, a pneumatic seal 234 is accommodated for sealing against the differential pressure control actuator or vacuum chamber. The seal 234 shown in detail in fig. 4 has a static sealing region 235, which static sealing region 235 surrounds the guide bushing 14 circumferentially with the inner side and seals at the end 231 on the outer side of the guide bushing. The outside of the static seal area 235 abuts the inside of the piston rod bore 13. The static sealing region 235 surrounds the end face of the end 231 of the guide bush 14 remote from the impeller and thus completely covers this end face. In the assembled state, the end face formed at the seal mounting position is in contact with the shoulder 28 of the piston rod bore 13 via the pneumatic seal 234, which shoulder 28 narrows to form the through-hole 21. The radial overlap of the outer diameter of the pneumatic seal 234 with the piston rod bore ensures a static seal. It is also contemplated that the pneumatic seal 234 has an annular protrusion (not shown) on the end face that is axially compressed during assembly.

The static seal portion 235 of the pneumatic seal 234 is incorporated into a dynamic seal portion 237, the dynamic seal portion 237 being formed as a seal lip. The sealing lip 237 extends axially inward into the guide bush 14, projects radially inward from the inside of the guide bush 14, and tapers in the pump chamber direction on the inside of the guide bush 14 while maintaining the same wall thickness. In other words, tapers exist both inboard and outboard of the seal lip 237. When the piston rod 12 is mounted, the dynamic seal portion 237 is in sealing contact with the outside of the piston rod 12 under a radial preload. The dynamic seal portion 237 is dimensioned such that at least one third, in particular more than 40%, of the height defined in the axial direction of the portion 23 of the guide bush 14 which is remote from the impeller and extends from the leakage groove 25 is covered on the inside.

On the side of the sealing means 15 facing the actuator, a negative pressure is present in the pump housing 2. Instead, atmospheric pressure exists between the

seals

23, 24. Due to the pressure difference, the sealing lip 237 abuts on its inner side against the piston rod 12. If the coolant enters the space between the

seals

23, 24 and the pressure on the dynamic seal portion 237 increases from the inside, the dynamic seal portion 237 presses on the piston rod 12 and the sealability increases. Accordingly, the pneumatic seal 234 can be prevented from leaking due to the load.

A hydraulic seal 244 is received in a recess 241 in the portion 24 of the sealing device 15 adjacent the impeller for sealing the pump chamber. The seal 244 shown in detail in fig. 5 has a static sealing region 245, which static sealing region 245 surrounds the guide bushing 14 on the circumferential surface and engages in the annular groove 241. The outside of static sealing area 245 abuts the inside of piston rod bore 13. A static sealing region 245 at least partially surrounds the end face of the guide bushing near the impeller and merges into a dynamic sealing region 246, which dynamic sealing region 246 projects outwardly in the axial direction beyond the guide bushing 245. Dynamic seal region 246 extends radially inward and forms a seal lip. A sealing lip 247 extends from the end face of the guide bush 14 close to the impeller into the pump chamber. The sealing lip 247 is conical and tapers away from the guide bushing 14. Thus, the end of the sealing lip 246 adjacent the impeller abuts the piston rod 12. The inner diameter of the sealing lip 247 in this region is selected such that the hydraulic seal 244 is in firm contact with the piston rod 12. The pump medium pressing on the hydraulic seal 244 presses the sealing lip 247 against the piston rod 12.

Claims

1. Controllable coolant pump (1) for an internal combustion engine, having a pump housing (2), a drivable pump shaft (4) rotatably mounted in the pump housing (2), an impeller (5) which is arranged non-rotatably at a free end of the pump shaft (4), and a differential pressure drive actuator which drives at least one piston rod (12), which piston rod (12) is guided in a piston rod bore (13) of the pump housing (2) and has a control slide (7), which control slide (7) is held at an impeller-side end of the piston rod (12), wherein the control slide (7) is arranged to variably cover an outflow region (11) of the impeller (5), and wherein the piston rod (12) is guided in the piston rod bore (13) by means of a guide bushing (14), the guide bushing (14) is part of a sealing device (15), which sealing device (15) seals a pump chamber conveying cooling liquid from the differential pressure driven actuator, wherein the sealing device (15) has two sealing elements (234, 244), each sealing element (234, 244) being arranged at one end of the guide bushing (14), and each sealing element (234, 244) having a static sealing region (235, 245) circumferentially surrounding the guide bushing (14) and a dynamic sealing region (237, 246, 248) adjoining the static sealing region (235, 245), a first sealing element (234) sealing a pressure chamber of the differential pressure driven actuator at the end of the guide bushing (14) remote from the impeller, and a second sealing element (244) sealing the pump chamber conveying cooling liquid at the end of the guide bushing (14) close to the impeller, characterized in that the dynamic sealing region (237) of the first seal (234) extends from the end face remote from the impeller end into the interior of the guide bushing (14), the dynamic sealing region (237) being designed to taper axially inwardly into the guide bushing (14).

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

3. A controllable coolant pump according to claim 1 or 2, characterised in that the outer side of the static sealing area (235) of the first seal (234) sealingly abuts the inner side of the piston rod bore (13).

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

5. Controllable coolant pump according to one of the preceding claims, characterized in that the dynamic sealing area (246, 248) of the second seal (244) extends from the end face of the guide bushing (14) close to the impeller into the pump chamber and outside the guide bushing (14).

6. Controllable coolant pump according to one of the preceding claims, characterized in that the outer side of the static sealing region (245) of the second seal (244) bears in a sealing manner against the inner side of the piston rod bore (13), and wherein the dynamic sealing region (246) of the second seal (244) is designed at its end on the impeller side to taper off in a conical region (246) with its outer side away from the guide bushing (14).

7. Controllable coolant pump according to one of the preceding claims, characterized in that the second seal (244) is slid onto the guiding bushing (14) and engages at least one annular groove (241) of the guiding bushing (14) for fixing the position.

8. Controllable coolant pump according to one of the preceding claims, characterized in that a drain outlet is provided in the guide bushing (14) between the two seals (234, 244).

9. Controllable coolant pump according to one of the preceding claims, characterized in that the dynamic sealing region (237, 246) is designed as a sealing lip.

10. Controllable coolant pump according to one of the preceding claims, characterized in that the seal (234, 244) at the end face at least partially surrounds the guide bushing (14).