Coolant pump for an internal combustion engine

Abstract

Coolant pumps for internal combustion engines with a drive shaft (18), a coolant pump impeller (20) which is fixedly arranged on the drive shaft (18) at least rotationally fixed and through which coolant can be conveyed and an adjustable control slide (58) via which a flow cross-section of an annular gap (62) between an outlet (64) of the coolant pump impeller (20) and the surrounding conveying channel (12) can be controlled are known. In order to achieve a reliable seal between the two opposing pressure chambers (92, 94), particularly in the case of purely hydraulic adjustment, it is proposed that the control slide (58) has an inner hollow cylindrical circumferential wall (84) with a radial groove (86) on its radial inside, in which a sealing ring (88) is arranged, and an outer hollow cylindrical circumferential wall (60) with a radial groove (74) on its radial outside, in which a sealing ring (76) is arranged, wherein the two circumferential walls (60, 84) are connected to each other via a base (80).

Description

[0001] The invention relates to a coolant pump for an internal combustion engine with a drive shaft, a coolant pump impeller which is arranged on the drive shaft at least in a rotationally fixed manner and through which coolant can be conveyed, and an adjustable control slide via which a flow cross-section of an annular gap between an outlet of the coolant pump impeller and the surrounding conveying channel can be controlled.

[0002] These types of coolant pumps are used in internal combustion engines to regulate the amount of coolant pumped, preventing the engine from overheating. These pumps are usually driven by a belt or chain drive, so that the coolant pump impeller is driven at the speed of the crankshaft or at a fixed ratio to the crankshaft speed.

[0003] In modern combustion engines, the amount of coolant supplied must be adjusted to the coolant requirements of the combustion engine or the vehicle. To avoid increased pollutant emissions and reduce fuel consumption, the engine's cold-start phase should be shortened. This is achieved, among other things, by throttling or completely shutting off the coolant flow during this phase.

[0004] Various pump designs are known for regulating the coolant flow rate. Besides electrically driven pumps, there are pumps that can be coupled to or disconnected from their drive via couplings, particularly hydrodynamic couplings. However, a particularly cost-effective and simple method for regulating the coolant flow is the use of an axially displaceable control slide that is moved over the coolant pump impeller. This reduces or completely closes the flow cross-section of the annular gap through which the pump impeller pumps the coolant into the surrounding delivery channel, thus reducing the coolant flow rate.

[0005] These valves are also controlled in various ways. Besides purely electric adjustment, hydraulic adjustment of the valves has proven particularly effective. For this purpose, a pressure chamber is located on the side of the valve facing away from the pump impeller. This chamber is filled with pressurized hydraulic fluid to create a pressure differential across the valve, causing it to move. The valve returns to its original position by opening the piston chamber to an outlet, usually via a solenoid valve, and by the action of a spring that provides the force for the return movement. The hydraulic pressure can be generated, for example, by a secondary pump mounted on the drive shaft, so that the coolant is also used to adjust the control valve.

[0006] A problem with these coolant pumps with a control valve is that the valve is pushed into the space through which the coolant flows. This allows coolant to flow along the gap into the space behind the control valve. With purely hydraulically actuated control valves, the pressure chamber must be sealed to generate the pressures necessary for adjustment. Even with control valves that have opposing pressure chambers separated only by the control valve, these chambers must be sealed against each other to prevent gradual pressure equalization, relieve stress on the pumping mechanism, and ensure valve adjustment at low speeds and consequently low side channel pressures and flow rates.

[0007] From DE 10 2004 054 637 A1, it is known to arrange a piston ring in a groove on the radial outer circumference of the control slide to prevent coolant from penetrating between the outer housing and the slide into the space behind the slide. However, in this design, coolant still flows through the radial interior of the slide towards the electromagnet, so it can be assumed that the piston ring primarily serves for guidance within the outer housing.

[0008] Furthermore, DE 10 2007 042 866 A1 discloses a controllable coolant pump in which the control slide is connected to an annular piston guided in a sleeve. Pressure can be generated on the underside of the annular piston by means of an actuating piston. When this pressure exceeds a spring force acting in the opposite direction, it causes the annular piston to be moved in the sleeve towards the impeller, thereby pushing the control slide over the impeller. When the actuating piston moves in the opposite direction, the pressure in the sleeve decreases, so that the spring force moves the control slide back into its position releasing the pump impeller. The annular piston is sealed on its underside by means of a sealing ring. A control slide on which pressure directly acts for adjustment is not disclosed.

[0009] The challenge, therefore, is to create a coolant pump for an internal combustion engine that minimizes leakage from one side of the control valve to the other. Additionally, the pump should ensure the most precise and frictionless adjustment of the control valve to all positions, requiring only minimal actuating forces.

[0010] This problem is solved by a coolant pump having the features of main claim 1.

[0011] The control slide has an inner hollow cylindrical circumferential wall with a radial groove on its inner radial side, in which a sealing ring is arranged, and an outer hollow cylindrical circumferential wall with a radial groove on its outer radial side, in which a sealing ring is arranged, with the two circumferential walls connected to each other via a base. This creates a reliable and leakage-minimizing seal between the front and rear of the slide. Additionally, the sealing rings can act as sliding elements, thus achieving reliable guidance of the slide on both sides. This prevents tilting, which would disable the function of the control slide, and reduces the frictional forces that occur during adjustment.

[0012] Preferably, the sealing rings are made of PTFE (polytetrafluoroethylene). These have a low coefficient of friction and also exhibit high wear resistance, even against corrosive liquids such as glycol-containing coolants.

[0013] In an advantageous embodiment of the invention, the sealing rings have a slot. This facilitates the installation of the sealing rings, which can first be slightly bent open to be fitted into the corresponding radial groove. Furthermore, the open piston ring allows for the one-piece design of the control slide, thus simplifying its manufacture.

[0014] In a further preferred embodiment, the slot runs at an angle to the central axis of the sealing ring. Due to the angled shape of the slot, it closes automatically when a pressure differential is applied or when the ring is moved, as the two angled surfaces are pressed against each other. Accordingly, a high level of sealing is achieved despite the slot and the resulting simplified installation.

[0015] Additionally, it is advantageous if the sealing ring, located on the inside of the inner hollow cylindrical circumferential wall, slides on a machined outer surface of a cylindrical section of a first housing part of the coolant pump. Such internal guidance of the control slide creates high coaxiality, allowing for manufacturing with tight tolerances, which in turn leads to low leakage. Furthermore, the existing friction is minimized because the control slide moves on a surface that can be easily machined from the outside, for example, to a surface roughness with a mean roughness value of less than 0.3 µm.

[0016] Furthermore, it is additionally or alternatively advantageous to allow the sealing ring, arranged on the outside of the outer hollow cylindrical circumferential wall, to slide on a machined inner surface of an axially extending annular projection of a second housing part of the coolant pump. These coolant pumps are frequently installed in an unmachined housing section of the internal combustion engine's crankcase, which can lead to leaks. However, by arranging the sealing ring inside the housing to be inserted, an effective seal can be achieved in all positions of the control slide, including on its outer circumference.

[0017] It is particularly advantageous if the outer hollow cylindrical circumferential wall has a shoulder from which the outer hollow cylindrical circumferential wall with an enlarged outer circumference extends towards the coolant pump impeller, the outer diameter of this enlarged section essentially corresponding to the outer diameter of the axially extending annular projection of the second housing part. Such a pump can be installed in a cylindrical recess of the crankcase. This ensures, on the one hand, the sealing of the valve and, on the other hand, avoids excessively large gaps at the valve or the need to reduce the size of the coolant pump impeller.

[0018] In a further embodiment, the shoulder rests axially against one end of the annular projection of the second housing part when the control slide is fully retracted. This reliably prevents an enlarged contact surface of the slide in its base area in its retracted position, which could lead to increased closing forces.

[0019] Preferably, the base separates a first pressure chamber from a second pressure chamber, allowing the control slide to be displaced depending on the pressure difference between the two chambers. In such a design, large force application areas of the control slide can be utilized, so that even smaller pressure differences are sufficient for adjustment. In a design with two actively fillable pressure chambers, return springs can be omitted.

[0020] In this design, the two pressure chambers are advantageously sealed off from each other by the two sealing rings. This significantly reduces leakage between the two pressure chambers, allowing for precise and rapid adjustment with minimal effort compared to known designs.

[0021] This results in a coolant pump for an internal combustion engine in which the pressure chambers of the control valve are sealed on all sides to minimize leakage. Simultaneously, precise guidance of the control valve is achieved, minimizing all gaps. The sealing rings used exhibit an extended service life.

[0022] An embodiment of a coolant pump according to the invention for an internal combustion engine is shown in the figures and is described below. Fig. Figure 1 shows a side view of a coolant pump according to the invention in a cutaway view. Fig. 2 shows one to Fig. 1 Rotated side view of the coolant pump according to the invention in cutaway view.

[0023] The coolant pump according to the invention consists of an outer housing 10 in which a spiral delivery channel 12 is formed. Coolant is drawn into the channel 12 via an axial pump inlet 14, also formed in the outer housing 10, and is conveyed through the delivery channel 12 to a tangential pump outlet 16 formed in the outer housing 10 and into a cooling circuit of the internal combustion engine. This outer housing 10 can, for example, be formed integrally with the crankcase or cylinder head of an internal combustion engine.

[0024] For this purpose, a coolant pump impeller 20, designed as a radial impeller, is mounted radially inside the delivery channel 12 on a drive shaft 18. Its rotation pumps the coolant within the delivery channel 12. A control pump impeller 22 is formed on the axial side of the coolant pump impeller 20 opposite the pump inlet 14 and rotates accordingly with the coolant pump impeller 20. This control pump impeller 22 has blades 23 arranged axially opposite a flow channel 24, which is designed as a side channel and is formed in a first inner housing part 26. This first housing part 26 has an inlet (not shown) and an outlet (also not shown), so that the control pump impeller 22 and the flow channel 24 form a control pump 28, through which the coolant pressure is increased from the inlet of the control pump 28 to the outlet.

[0025] The coolant pump impeller 20 and the control pump impeller 22 are driven by a belt that engages a pulley 30, which is attached to the axial end of the drive shaft 18 opposite the coolant pump impeller 20. The pulley 30 is supported by a double-row ball bearing 32, the outer ring 34 of which is pressed onto the pulley 30 and the inner ring 36 of which is pressed onto a second stationary housing part 38. The second housing part 38 has an inner axial through-opening 40 through which the drive shaft 18 projects with a shaft seal 42 in between, and into which an inner annular projection 44 of the first housing part 26 projects, centering the first housing part 26 relative to the second housing part 38. The first housing part 26 is fastened to the second housing part 38 by screws 46 that axially penetrate the first housing part 26. The second housing part 38 is attached to the outer housing 10 with a seal 48 in between.For this purpose, the outer housing 10 has a receiving opening 50 of constant diameter at its axial end opposite the pump inlet 14, into which an annular projection 52 of the second housing part 38 projects, on whose limiting flange-shaped wall 54, which abuts axially against the outer housing 10, a groove 56 is formed in which the seal 48 is arranged.

[0026] This projection 52 simultaneously serves as a rear stop for a control slide 58, whose radially outer hollow cylindrical circumferential wall 60 can be slid over the coolant pump impeller 20 in such a way that a free cross-section of an annular gap 62 between an outlet 64 of the coolant pump impeller 20 and the delivery channel 12 is regulated. The coolant flow conveyed through the coolant circuit is thus regulated according to the position of this control slide 58. This circumferential wall 60 accordingly has a shoulder 66 from which the circumferential wall 60 extends axially with an increased diameter towards the annular gap 62.The outer diameter of this section 68 corresponds approximately to the outer diameter of the annular projection 52, so that the annular projection 52 and this section 68 of the circumferential wall 60 are formed directly opposite an inner wall 70 of the receiving opening 50 of the outer housing 10, thereby minimizing gaps in this area.

[0027] On the section 72 of the outer circumferential wall 60, extending from the shoulder 66 in the opposite direction to the coolant pump impeller 22, a radial groove 74 is formed on the radial outer surface in which a sealing ring 76, made of PTFE, is arranged. The sealing ring 76 is arranged such that, in every position of the control slide 58, it bears against a machined inner surface 78 of the annular projection 52 of the second housing part 38. Due to the machining, this inner surface 78 has a very low roughness, so that it serves as a low-friction sliding and sealing surface for the sealing ring 76.

[0028] The control slide 58 has, in addition to its circumferential wall 60, a base 80 with an inner opening 82. The circumferential wall 60 extends axially from the outer circumference of the base, and a shorter, inner, hollow cylindrical circumferential wall 84 extends from the inner circumference of the base towards the coolant pump impeller 20. A radial groove 86 is formed on the radial inner surface of this circumferential wall 84. A sealing ring 88 made of PTFE, which is insensitive to the coolant and has good sliding properties, is also arranged in this groove. The circumferential wall 84 slides on a similarly machined outer surface 89 of an axially extending cylindrical section 90 of the first housing part 26. This section 90 is formed between the annular projection 44 and the section of the first housing part 26 that forms the flow channel 24. The section 90 serves to support the control slide 58.To ensure low-friction guidance, the two machined surfaces 78 and 89 have a mean roughness of approximately 0.3 µm. This results in only low actuating forces being required when moving the control slide 58, and a high degree of sealing between the front and back of the control slide 58 is achieved.

[0029] This is important because a first pressure chamber 92 is formed on the side of the control slide 58 facing away from the coolant pump impeller 20, which is bounded axially by the second housing part 38 and the bottom 80 of the control slide 58 and radially outwards by the annular projection 52 of the second housing part 38 and radially inwards by the first housing part 26, and a second pressure chamber 94 is formed on the side of the bottom 80 facing the coolant pump impeller 20, which is bounded axially by the bottom plate 80 and the first housing part 26, radially outwards by the circumferential wall 60 of the control slide 58 and radially inwards by the section 90 of the first housing part 26.Depending on the pressure differential at the base 80 of the control slide 58 in the two pressure chambers 92, 94, the outer circumferential wall 60 of the control slide 58 is pushed into or out of the annular gap 62 accordingly. To prevent pressure equalization between the two pressure chambers 92, 94, a high degree of sealing between them is required, which is achieved by the PTFE sealing rings 76, 88. This sealing is further enhanced by the pressure differential, as the sealing rings 76, 88 are subjected to pressure against the respective axial wall defining the radial groove 74, 86, and a slot 96, 98 necessary for mounting the sealing rings 76, 88 is closed. The slots 96, 98 are designed so that the sealing rings are opened at the circumference through these slots 96, 98, allowing them to be bent open for assembly.However, the slots 96, 98 do not run in an axial direction, but are inclined at least 30° to the central axis. This results in the two opposite ends of the sealing rings 76, 88 being pressed against each other when a pressure differential is applied, thus exhibiting a sealing performance comparable to that of a closed sealing ring.

[0030] The necessary pressure differential is generated by the control pump 28 and supplied to the respective pressure chambers 92, 94 by means of a valve 100, which is designed as a solenoid valve. For this purpose, correspondingly arranged channels, not visible in the figures, are formed in the two housing parts 26, 38, through which pressurized coolant can be supplied to or discharged from the respective pressure chamber. As a result of this pressure differential, the control slide 58 is pushed into the annular gap 62 to reduce the amount of coolant delivered, or pushed out of it to maximize the amount of coolant delivered to the cooling circuit.

[0031] The described coolant pump features a very precise internal guide, so that despite small gaps, only low actuating forces are required. This is further enhanced by the excellent sliding properties of the sliding surfaces opposite the sealing rings. The durable and smooth-running sealing rings used reliably seal the pressure chambers against each other, allowing adjustment of the control valve with minimal actuating forces and resulting in a significantly delayed pressure equalization between the pressure chambers.

[0032] It should be clear that the scope of protection of the main claim is not limited to the described embodiment. In particular, other housing divisions or a different type of actuation of the control slide are conceivable. In addition to purely hydraulic adjustment, electrical adjustments or preloading by means of compression springs are also conceivable. Furthermore, other sealing rings with good sliding and sealing properties that are insensitive to corrosion when used with refrigerants such as glycol can be used.

Claims

[1] Coolant pump for an internal combustion engine with a drive shaft (18), a coolant pump impeller (20) which is fixedly arranged on the drive shaft (18) at least rotationally fixed and through which coolant can be conveyed, an adjustable control slide (58) via which a flow cross-section of an annular gap (62) between an outlet (64) of the coolant pump impeller (20) and a surrounding delivery channel (12) can be controlled, characterized by , that the control slide (58) has an inner hollow cylindrical circumferential wall (84) on the radial inside of which a radial groove (86) is formed in which a sealing ring (88) is arranged and an outer hollow cylindrical circumferential wall (60) on the radial outside of which a radial groove (74) is formed in which a sealing ring (76) is arranged, wherein the two circumferential walls (60, 84) are connected to each other via a base (80). [2] Coolant pump for an internal combustion engine according to claim 1, characterized by , that the sealing rings (76, 88) are made of PTFE (polytetrafluoroethylene). [3] Coolant pump for an internal combustion engine according to one of claims 1 or 2, characterized by that the sealing rings (76, 88) each have a slot (96, 98). [4] Coolant pump for an internal combustion engine according to claim 3, characterized by , that the slot (96, 98) is inclined to the central axis of the respective sealing ring (76, 88). [5] Coolant pump for an internal combustion engine according to any of the preceding claims, characterized by , that the sealing ring (88) arranged on the inside of the inner hollow cylindrical circumferential wall (84) slides on a machined outer surface (89) of a cylindrical section (90) of a first housing part (26) of the coolant pump. [6] Coolant pump for an internal combustion engine according to one of the preceding claims, characterized by , that the sealing ring (76) arranged on the outside of the outer hollow cylindrical circumferential wall (60) slides on a machined inner surface (78) of an axially extending annular projection (52) of a second housing part (38) of the coolant pump. [7] Coolant pump for an internal combustion engine according to claim 6, characterized by , that the outer hollow cylindrical circumferential wall (60) has a shoulder (66) from which the outer hollow cylindrical circumferential wall (60) extends with an enlarged outer circumference towards the coolant pump impeller (20), wherein an outer diameter of this section (68) with an enlarged diameter corresponds essentially to the outer diameter of the axially extending annular projection (52) of the second housing part (38). [8] Coolant pump for an internal combustion engine according to claim 7, characterized by , that the shoulder (66) in a fully retracted position of the control slide (58) rests axially against one end of the annular projection (52) of the second housing part (38). [9] Coolant pump for an internal combustion engine according to any of the preceding claims, characterized by , that the bottom (80) separates a first pressure chamber (92) from a second pressure chamber (94), so that the control slide (58) can be moved depending on a pressure difference between the two pressure chambers (92, 94). [10] Coolant pump for an internal combustion engine according to claim 9, characterized by , that the two pressure chambers (92, 94) are sealed against each other pressure chamber (92, 94) by the two sealing rings (76, 88).

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