Patent Application
20220356884
The present disclosure relates to a controllable coolant pump of internal combustion engines.
Controllable coolant pumps have a control system for varying the cooling capacity. Such a control system is described in, for example, DE 10 2005 062 200 B3. A valve spool has an outer cylinder which variably covers the discharge area of the impeller of the coolant pump. The valve spool is arranged on several piston rods which are movably mounted in the pump housing. The position of the valve spool reflects the coolant flow and thus the cooling capacity. 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 publication EP 2 722 567 A1. The sealing device has a bushing-shaped base body which serves as a guide for the piston rod. A seal is attached to one end of the base body in each case. The seals have dynamic sealing sections which are designed as sealing lips. A disadvantage of this sealing device is that pressure support is not effective at low pressure differences, and aged sealing components cause leaks to occur.
Example embodiments of the present disclosure provide controllable coolant pumps each including a piston rod guide, which includes a sealing device that always ensures a reliable seal even under load.
An example embodiment of the present disclosure provides a controllable coolant pump of internal combustion engines including a pump housing, a drivable pump shaft rotatably mounted in the pump housing, an impeller fixed on a free end of the pump shaft, and a pressure-difference-driven actuator to drive at least one piston rod which is guided in a piston rod bore of the pump housing and includes a control spool held at the impeller-side end of the piston rod. The control spool variably covers an outflow region of the impeller, the piston rod being guided in the piston rod bore by a guide bushing which is a portion of a sealing device which seals off a pump chamber carrying the coolant from the pressure-differential-driven actuator, the sealing device including two seals which are spaced apart from one another, which are on one end of the guide bushing, and which include a static sealing area surrounding the guide bushing on a circumferential side and a dynamic sealing area adjoining the static sealing area, a first seal to seal off a pressure space of the pressure-difference-driven actuator at an end of the guide bushing remote from the impeller and a second seal to seal off the pump space carrying coolant at the end of the guide bushing adjacent the impeller. The dynamic sealing area of the first seal extends into the interior of the guide bushing from an end surface at the end remote from the impeller and is tapered inward into the guide bushing in the axial direction. The dynamic sealing area thus provides a reliable seal of the pressure chamber. In the event that coolant enters the space between the seals, the structure ensures that the first seal does not lift off the piston rod but remains sealingly adjacent to it, thus always providing a secure seal.
Preferably, the dynamic sealing area of the first seal is spaced from the inside of the guide bushing in the unloaded state.
If the piston rod tilts in the bore, a dynamic area of the first seal follows the movement without losing the radial circumferential contact, in particular line contact, with the piston rod. The structure of the first seal ensures that a reliable seal is maintained even if the piston rod tilts.
Preferably, an outer side of the static sealing area of the first seal is in sealing contact with an inner side of the piston rod bore.
In an example embodiment, the static sealing area of the first seal includes an annular protrusion in an area of the end surface of the sealing device, which is compressed during installation.
Preferably, the dynamic sealing area of the second seal extends from the end surface of the guide bushing adjacent the impeller into the pump chamber and lies outside the guide bushing.
It is advantageous if the dynamic sealing area of the second seal on the inside rests securely against the piston rod when installed.
Preferably, the outside of the static sealing area of the second seal is in sealing contact with the inside of the piston rod bore, and the dynamic sealing area adjoining the static sealing area is tapered on its outer side away from the guide bushing at its end on the impeller side to ensure that the second seal is always in radial circumferential contact with the piston rod, in particular with line contact.
Preferably, the dynamic sealing area of the second seal includes a sealing lip on the inside. An annular groove is provided concentrically with respect to the unloaded piston rod is between the conical region of the second seal and the sealing lip on the end surface, which annular groove permits movement in the radial direction of the sealing lip of the second seal and the conical region of the second seal independently of one another.
It is advantageous if the second seal is pushed onto the guide bushing and engages in an annular groove of the guide bushing to fix the position. The two seals are preferably rotationally symmetrical.
Preferably, a drainage outlet is between the two seals in the guide bushing.
The dynamic sealing areas are preferably sealing lips.
The seals preferably surround the guide bushing at least partially on the end surface.
Preferably, the guide bushing is made of a thermoplastic material. Preferably, the sealing device includes elastomer seals.
Furthermore, it is advantageous if the piston rod can be moved parallel to the pump shaft by the pressure difference driven actuator. The pressure difference driven actuator can be a pneumatic or hydraulic actuator. In an example embodiment of the present disclosure, the pressure difference driven actuator is a pneumatic drive. The vacuum chamber is preferably sealed by, among other things, a rolling diaphragm. When the vacuum chamber is evacuated, the diaphragm rolls out due to the pressure difference between the atmospheric pressure and the vacuum region and moves a piston slide in which the piston rods are suspended.
The above and other elements, features, steps, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings.
Example embodiments of the present disclosure is explained in more detail below with reference to the drawings. Similar or similarly acting components are designated in the figures with the same reference signs.
The piston rods 12 are driven by a pressure differential driven actuator, in this case a pneumatic actuator operating with negative pressure. The piston rod 12 is guided on the control spool side in a guide bushing 14 in the piston rod bore 13. The guide bushing 14 is part of a sealing device 15, each with two seals 16. The two seals 16 are each arranged at one end of the guide bushing 14. They are spatially separated from each other and do not influence each other. The seal far from the impeller seals the vacuum chamber of the pneumatic drive and the seal near the impeller seals the pump chamber carrying coolant.
A drainage outlet 17 arranged between the two seals 16 can discharge a coolant that has penetrated into the space between the two seals 16.
The piston rod 12 is held on the vacuum side in a piston slide 18. The piston slide 18 is arranged in a piston slide holder in a rolling diaphragm in a vacuum chamber 19 whose inner diameter is larger than that of the piston rod bore 13. The receptacles of the piston slide 18 are thus connected to each other via the continuous rolling diaphragm. The vacuum chamber is sealed by the rolling diaphragm, which also receives the piston slide. The vacuum 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 vehicle's vacuum supply by a hose nozzle pressed into the housing. When the vacuum chamber is evacuated, the diaphragm rolls out due to the pressure difference between atmospheric pressure and the vacuum area, thus moving the piston slide in which the piston rods are suspended.
By the pneumatic drive, the control spool 7 can be moved between an open position and a closed position. In the open position shown in
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 in the pump housing 2 is provided. The second guide point 20 is formed by a through hole 21 between the piston slide holder and the piston rod bore 13. The through hole 21 has a clear width that is smaller than the clear width of the piston slider receptacle 19 and piston rod bore 13. The clear width of the through hole 21 is matched with some clearance to the outer diameter of the piston rod 12. The cylindrical portion of the through hole 21 is to be designed as small as possible so that the risk of jamming of the guide rod 12 in the through hole 21 is minimized. The piston rod 12 is thus guided only on the vacuum side on the pump housing 2 and in the area of the sealing device 15 by a guide bushing 14 in the pump housing 2. Due to the “two-point guide”, tilting of the piston rod 12 is only possible to a limited extent even when force is applied to the piston rod 12. The sealing device 15 will age over the life of the pump, which reduces its compensating capacity in the event of piston rod deflection. The two-point guide reduces the radial deflection of the piston rod, so that the compensating capacity of the sealing device 15 does not have to be so high.
The guide bushing 14 has two sections 23,24, each of which is designed to receive a seal 16. The two sections 23,24 are connected to each other by a central area 25, which is penetrated by at least one radial opening 26. In the illustrated example embodiment example, two radial openings 26 are provided in alignment with one another. The outer diameter of the guide bushing 14 in this central region 25 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 bushing 14. The radial openings 26 form an inner drainage outlet and the circumferential recess 27 an outer drainage outlet. A coolant that has entered the guide bushing 14 can be drained radially outwardly into the recess 27 through the radial openings 26 and discharged outwardly through the drainage outlet. Due to the circumferential recess 27, it is not necessary to pay attention to a positionally accurate installation position of the sealing device 15. In the axial direction, however, care must be taken to ensure exact positioning in order to form the leakage system with the circumferential recess 27 of the guide bushing 14 and the leakage drainage holes in the pump housing 2, otherwise the areas 23 and 24 will close off 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 bounded in the axial direction respectively by two annular webs 242,243. The inner web 243 has an outer diameter which produces the interference fit in the housing by overlapping with the piston rod bore 13.
A pneumatic seal 234 is accommodated at the axial end 231 of the section 23 remote from the impeller for sealing with respect to the pressure differential-controlled actuator or the vacuum chamber. The seal 234, shown in detail in
The static sealing section 235 of the pneumatic seal 234 merges into a dynamic sealing section 237, which is formed as a sealing lip. The sealing lip 237 extends inwardly into the guide bushing 14 in the axial direction, protruding inwardly from the inside of the guide bushing 14 in the radial direction, and is tapered inside the guide bushing 14 in the direction of the pump chamber while maintaining the same wall thickness. In other words, the taper is present on the inner side and the outer side of the sealing lip 237. When the piston rod 12 is mounted, the dynamic sealing section 237 is in sealing contact with the outside of the piston rod 12 under radial preload. 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 remote from the impeller wheel and extending from the leakage groove 25 is covered in the interior.
On the side of the sealing device 15 facing the actuator, negative pressure prevails in the pump housing 2. In contrast, atmospheric pressure prevails between the seals 23,24. Due to the pressure difference, the sealing lip 237 nestles against the piston rod 12 on its inner side. In the event that cooling liquid enters the space between the seals 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 is thus possible to prevent the pneumatic sealing member 234 from leaking due to load.
A hydraulic seal 244 is received in the groove 241 of the section 24 of the sealing device 15 near the impeller for sealing against the pump chamber. The seal 244 shown in detail in
While example embodiments of the present disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2019 122 718.6 | Aug 2019 | DE | national |
This is a U.S. national stage of PCT Application No. PCT/EP2020/070670, filed on Jul. 22, 2020, and with priority under 35 U.S.C. § 119(a) and 35 U.S.C. § 365(b) being claimed from German Application No. 10 2019 122 718.6, filed on Aug. 23, 2019, the entire disclosures of which are hereby incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/070670 | 7/22/2020 | WO |
