PUMP ARRANGEMENT, A FUEL DELIVERY SYSTEM AND A LIQUID COOLING SYSTEM FOR AN INTERNAL COMBUSTION ENGINE INCORPORATING SUCH A PUMP AND A VEHICLE COMPRISING SUCH A FUEL DELIVERY SYSTEM AND LIQUID COOLING SYSTEM

Abstract: A pump arrangement (10) is disclosed having a housing (12), a first pumping chamber (14) within the housing, a drive shaft (18) carried by the housing, and first pumping means (16) arranged for rotation within the first pumping chamber (14). The first pumping means is driven by the drive shaft. A second pumping chamber (22) accommodating second pumping means (26) is separated from the first pumping chamber by the housing (12) such that the housing forms a common separation wall (24). To provide a compact arrangement in which the first and second pumping chambers are reliably sealed from each other, the second pumping means is driven by the drive shaft (18) via a magnetic coupling (32). Thus, the coupling comprises a driver rotor (34) connected to the drive shaft (18) and a driven rotor (36) carried by the housing (12). The driver rotor (34) and the driven rotor (36) are separated by a separation wall assembly (48) serving as a static seal to hermetically seal the second pumping chamber from the drive shaft.

Description: PUMP ARRANGEMENT, A FUEL DELIVERY SYSTEM AND A LIQUID COOLING SYSTEM FOR AN INTERNAL COMBUSTION ENGINE INCORPORAΗNG SUCH A PUMP AND A VEHICLE COMPRISING SUCH A FUEL DELIVERY SYSTEM AND LIQUID COOLING SYSTEM TECHNICAL FIELD: The present invention relates to a pump arrangement primarily, though not exclusively, for use in vehicles. The invention further relates to a fuel delivery system incorporating such a pump arrangement. The invention also relates to a liquid cooling system for an internal combustion engine incorporating such a pump arrangement. BACKGROUND OF THE INVENTION: In the fuel delivery system of a commercial vehicle it is known to use a rotary displacement pump driven by the transmission of the vehicle to increase the fuel pressure in the system to a level suitable for injection of the fuel into the vehicle engine. The pump has to be capable of delivering fuel at a sufficient pressure substantially immediately upon starting the engine. This implies that at high engine speeds the pressure in the fuel delivery system is greater than actually required and, as a result, an overpressure valve is required downstream of the pump to relieve the excess pressure. A conventional rotary displacement pump comprises a housing, a pumping chamber within the housing, pressure increasing means in the form of intermeshing gears within the pumping chamber, and an input shaft to the housing to effect rotation of the intermeshing gears. To prevent leakage of the pumped liquid from the pumping chamber, it is necessary that adequate sealing means be provided between the housing and the input shaft. Due to the rotation of the input shaft, a dynamic seal must be employed. In the fuel delivery system described above, failure of the sealing means not only implies that fuel leaks out of the system, but also that the leaking fuel may migrate into the transmission and mix with the lubricant therein. Furthermore, the use of a transmission-driven fuel pump implies that a suitable location for the drive shaft to the pump has to be provided, as well as ensuring correct gearing for the drive shaft. Given the space constraints in modern vehicles, these demands are not always simple to accomplish. It is also known to use electrically driven pump to supply fuel to an internal combustion engine. Such a pump is not particularly efficient, however, since electrical energy to drive the pump must be generated by the internal combustion engine and this electrical energy is thereafter reconverted to mechanical energy in the pump. This implies losses during conversion. Virtually without exception, internal combustion engines used in commercial vehicles require liquid cooling using a coolant. The coolant is pumped through the engine using a so-called water pump. Typically, the water pump is attached to the cylinder block and is driven by a belt from the crankshaft of the engine. A dual pump system is known from U.S. Patent No. 3 370 540 comprising a first gear pump having a drive member and a driven member and a second gear pump which is magnetically driven by the first gear pump. The drive member and the driven member are made from magnetic material. The second gear pump comprises an internal gear element having magnetic material peripherally carried thereon in juxtaposition to both the drive member and the driven member. The internal gear element is separated from the drive and driven members by an impermeable member attached to the pump body of the first gear pump. Rotation of the drive member and the driven member allows responsive rotation of the internal gear element. In this manner, two separate liquids may be pumped by the dual pump system. A disadvantage with this dual pump system is that two pump bodies are required, one for the first gear pump and one for the second gear pump. Another dual pump arrangement is disclosed in DE-A-44 34 244. In said document, two axially arranged pumps are mechanically driven by a common drive shaft, with one pump acting as a fuel pump and the other pump serving as a power steering pump. A conceivable problem with this arrangement is the risk of leakage of liquid from one pump to the other due to failure of the seals around the common drive shaft. SUMMARY OF THE INVENTION: It is an object of the present invention to provide a pump arrangement which is suitable for use in commercial vehicles to pump fuel and coolant, which pump arrangement is potentially more compact, energy efficient and easier to seal than previous arrangements. This object is achieved in accordance with the present invention by a pump arrangement according to claim 1 comprising a housing, a first pumping chamber within said housing, said first pumping chamber being adapted to be connected to a first liquid transport circuit, a drive shaft carried by said housing, first pumping means arranged for rotation within said first pumping chamber, said first pumping means being driven by said drive shaft, a second pumping chamber separated from said first pumping chamber by said housing such that said housing forms a common separation wall, said second pumping chamber being adapted to be connected to a second liquid transport circuit, said second pumping chamber accommodating second pumping means being driven by said drive shaft, wherein said second pumping means is driven by said drive shaft via a magnetic coupling, the coupling comprising a driver rotor connected to said drive shaft and a driven rotor carried by said housing, said driven rotor driving said second pumping means, said driver rotor and said driven rotor being separated by a separation wall assembly serving as a static seal to hermetically seal the second pumping chamber from said drive shaft. Accordingly, the pump arrangement of the present invention is a single compact unit which is able to pump two separate liquids in respective liquid transport circuits with greatly reduced risk of inadvertent mixing of the two liquids. Furthermore, since the magnetic coupling is only capable of transmitting a predetermined value of torque, the pressure downstream of the pump cannot exceed a predetermined value, irrespective of the rotational speed and/or torque of the input shaft. The invention further provides for a fuel delivery system incorporating the pump arrangement of the present invention, as well as a liquid cooling system incorporating said pump arrangement. In addition, the invention provides for a vehicle comprising the fuel delivery system and the liquid cooling system of the present invention. Further preferred embodiments of the invention are detailed in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS: The invention will be described in greater detail in the following by way of example only and with reference to embodiments shown in the attached drawings, in which: Fig. 1 is a schematic perspective view of the pump arrangement of the present invention; Fig. 2 is a schematic cross-sectional view along line II-II of Fig. 1; Fig. 3 is a simplified end view of the pump arrangement according to the present invention in a partially dismantled condition; Fig. 4 is a schematic perspective view of the separation wall assembly forming a part of the pump arrangement of the present invention; Fig. 5 is a schematic perspective view of the driver rotor forming a part of the pump arrangement according to the present invention; Fig. 6 is a schematic representation of a fuel delivery system incorporating the pump arrangement according to the present invention; and Fig. 7 is a schematic representation corresponding to Fig. 6, though with the addition of a liquid cooling system incorporating the pump arrangement according to the present invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS: In the following, the pump arrangement of the present invention will be described in a favoured application for use as a combined fuel pump and water pump for an internal combustion engine. It is to be understood, however, that such an application is described by way of example only and that the pump arrangement may be employed for any application in which its particular advantages may be utilized. In the drawings, reference numeral 10 generally denotes a pump arrangement according to the present invention. The pump comprises a housing 12 which, in a favoured application of the present invention, is arranged to be bolted or attached in any suitable manner to the block of an internal combustion engine. With particular reference to Fig. 2, the pump arrangement 10 comprises a first pumping chamber 14 within the housing 12. The first pumping chamber is adapted to be connected to a first liquid transport circuit, for example the liquid cooling system of a vehicle engine. Thus, in a known manner, the first pumping chamber 14 may be used to generate pressure in a liquid coolant. To this end, first pumping means 16 in the form of an impeller is arranged for rotation within the first pumping chamber. To effect rotation of the impeller 16, the impeller is connected to a drive shaft 18 carried by the housing 12. The drive shaft 18 is caused to rotate by a not shown drive belt or gear train driven by the crankshaft of the engine to which the pump arrangement is attached. A sealing bush 20 is provided between the drive shaft 18 and the housing 12 to thereby prevent leakage of the liquid coolant out of the first pumping chamber past the drive shaft. Liquid coolant is introduced into the first pumping chamber 14 through an opening arranged concentrically with the drive shaft 18 and exits the first pumping chamber via an outlet 21 to thereafter continue its path through the first liquid transport circuit. The pump arrangement 10 also incorporates a second pumping chamber 22 adapted to be connected to a second liquid transport circuit, the second pumping chamber being hermetically sealed from the first pumping chamber 14. In other words, the contents of the first pumping chamber cannot enter the second pumping chamber or vice versa. To this end, the first pumping chamber 14 may be formed in a first surface of the housing 12 and the second pumping chamber 22 may be formed in a second surface of the housing. In this manner, the housing serves as a common separation wall 24 between the pumping chambers. Although in the drawings the housing 12 is shown as a unitary piece, it is to be understood that the housing may also be fabricated from a plurality of components. Thus, the expression "common separation wall" is intended to encompass both a unitary wall and a fabricated wall. In the described embodiment, the second liquid transport circuit is a fuel delivery system and the second pumping chamber is utilized to increase the pressure in fuel. To achieve this, the second pumping chamber 22 accommodates second pumping means 26 in the form of, for example, a pair of intermeshing gear wheels (see Fig. 3). The second pumping chamber 22 has an inlet 28 and an outlet 30 for the liquid to be pumped, i.e. fuel in the exemplary embodiment. In a manner which will be explained in more detail in the following, and in accordance with the present invention, the second pumping means 26 is driven by the drive shaft 18 via a magnetic coupling 32. As is most clearly apparent from Fig. 2, the coupling 32 comprises a driver rotor 34 connected to the drive shaft, for example by splines or a keyed connection, and a driven rotor 36 carried by the housing 12. The driver rotor 34 and the driven rotor 36 are concentrically arranged about the drive shaft 18. The driven rotor 36 is journalled for rotation on the housing and drives the second pumping means 26 via a toothed peripheral section 38 on the driven rotor. In a preferred embodiment of the invention, the driver rotor 34 supports a number of first magnets 40 arranged circumferentially on the driver rotor and the driven rotor 36 supports a number of second magnets 42 arranged circumferentially on the driven rotor. The first magnets 40 on the driver rotor are held in a first magnet holder assembly 44 and the second magnets 42 on the driven rotor 36 are held in a similar manner in a second magnet holder assembly 46. The first and second magnet holder assemblies 44,46 are preferably each in the form of an annular ring having a number of recesses equal to the number of magnets for maintaining the magnets in spaced peripheral relationship. To ensure optimal torque transmission through the coupling 32, the first and second magnet holder assemblies should be substantially radially aligned. In the preferred embodiment shown in the drawings, the first magnet holder assembly 44 is arranged on a radially inwardly facing surface of the driver rotor 34 (see also Fig. 5) and the second magnet holder assembly 46 is arranged on a radially outwardly facing surface of the driven rotor 36. A construction is however conceivable in which the relative positions of the first and second magnet holder assemblies are reversed. To ensure that the second pumping chamber 22 is sealed, a separation wall assembly generally denoted by reference numeral 48 is provided. With particular reference to Figs. 2 and 4, the separation wall assembly serves i.a. to separate the driver rotor 34 and the driven rotor 36. More particularly, the separation wall assembly 48 has an annular portion 50 arranged substantially parallel to the drive shaft 18, the annular portion passing through a gap between the first and second magnet holder assemblies 44 and 46. At a first axial end of the annular portion 50, the separation wall assembly has a radially outwardly extending flange 52 partially delimiting the second pumping chamber 22. At a second axial end of the annular portion, the assembly has a radially inwardly extending flange 54 comprising sealing means 56 for sealing against the housing 12. The radially outwardly extending flange 52 may also be provided with sealing means 58 to assist in retaining liquid within the second pumping chamber. It will thus be apparent that the separation wall assembly 48 serves as a static seal to hermetically seal the second pumping chamber from the rotating drive shaft and driver rotor. In terms of material selection, the separation wall assembly may be made from steel, preferably stainless steel, while the housing and the first and second magnet holder assemblies may be made from aluminium. The amount of torque which can be transmitted through the coupling 32 depends i.a. on the strength of the magnets and the size of the gap between the first and second magnet holder assemblies. The parameters determining the amount of torque which can be transmitted can of course be selected for each chosen application. A major advantage of using a magnetic coupling is that when a certain value of torque is applied across the coupling 32, the second magnet holder assembly 46 tends to lag behind the first magnet holder assembly 44, i.e. the coupling "slips". Should the amount of torque increase further, the first magnet holder assembly 44 "skips" relative to the second magnet holder assembly 46 and proceeds to rotate faster than the second magnet holder assembly whilst still transmitting the same, maximum, amount of torque. Accordingly, the preferred coupling 32 of the present invention is eminently suitable for use in applications in which a maximum amount of torque transmission is desired irrespective of the applied torque. Operation of the pump arrangement of the present invention will be described in the following in which the pump arrangement is used to pump both a coolant and a fuel for an internal combustion engine. When the drive shaft 18 is caused to rotate, coolant is drawn into the first pumping chamber 14 due to rotation of the impeller 16. After being subjected to an increase in pressure, the coolant exits the first pumping chamber via the outlet 21. Should the impeller 16 be directly attached to the drive shaft 18, the volume flow rate of coolant will be substantially proportional to the rotational speed of the drive shaft. Rotation of the drive shaft 18 also effects rotation of the driver rotor 34 and hence the first magnet holder assembly 44. The magnetic field between the magnets of the first and second magnet holder assemblies causes the second magnet holder assembly 46 and thus the driven rotor 36 to rotate. As a result, the toothed peripheral section 38 of the driven rotor 36 engages with the gear wheels 26 of the second pumping means within the second pumping chamber 22 and fuel is drawn into the chamber via the inlet 28. After being subjected to an increase in pressure, the fuel exits the second pumping chamber via the outlet 30 to continue its path through the second liquid transport circuit. For internal combustion engines equipped with a fuel injection system, the pump arrangement has to be capable of delivering fuel at a sufficient pressure substantially immediately upon starting the engine. Accordingly, the pump arrangement 10 is designed such that fuel exits the second pumping chamber at sufficiently high pressure even at low rotational speeds of the drive shaft 18. To prevent excess pressure arising in the fuel system at higher rotational speeds of the drive shaft, the coupling 34 is arranged to slip in the manner described above if the applied torque is greater than that necessary to maintain the desired pressure in the fuel system. In this manner, it is ensured that the pumping pressure in the second pumping chamber 22 never exceeds a desired level. The above-described pump arrangement is eminently suitable for use as a fuel pump in a vehicle fuel delivery system. Such a system is schematically illustrated in Fig. 6 and serves as the second liquid transport circuit. In the drawing, the pump is denoted by reference numeral 10. The pump has a suction side 60 and an output side 62. The suction side 60 of the pump is connected to a fuel reservoir 64 and a fuel delivery line 66 is connected to the output side 62 of the pump. A fuel filter 68 is connected into the delivery line 66. Downstream of the fuel filter 68, a number of fuel injectors 70 are provided with fuel via the delivery line. The fuel injectors are arranged to inject fuel into cylinders of an internal combustion engine 71. In order to ensure that the fuel delivered to the injectors 70 has a substantially uniform temperature, the pump is arranged to pump a greater quantity of fuel along the delivery line 66 than is required by the injectors. The surplus of fuel is returned to the suction side 60 of the pump via a return line 72. A further advantage of this arrangement is that fuel is recirculated through the filter 68 a number of times, thereby increasing the purity of the fuel. In a typical installation, the pump can be arranged to pump between 2 and 8 litres/minute (1/min) of fuel at a maximum pressure of about 9 bar in the fuel delivery line 66 adjacent the outlet side 62 of the pump. Normally, a maximum pressure of about 6 bar is sufficient in the fuel delivery line. Thus, a not shown overpressure valve may be incorporated in the fuel delivery system. Depending on the load on the engine, between about 0.5 and 1.5 1/min of fuel is injected into the engine via the injectors 70. This implies that between about 1.5 and 7.5 1/min of fuel is returned to the pump. An amount of fuel corresponding to that which has been injected into the engine is drawn from the reservoir by the pump. A one-way valve 74 between the reservoir 64 and the pump ensures that fuel in the return line 72 does not drain into the reservoir. Since the magnetic coupling in the pump can be adapted to ensure that a maximum pressure of no more than 9 bar is generated in the delivery line 66, even if the overpressure valve should stick shut, no damage will result. This further implies that less power is needed to drive the pump than with conventional pumps in which the fuel output pressure is much greater than 9 bar at higher pump speeds. The system shown schematically in Fig. 7 corresponds essentially to Fig. 6, though with the addition of a liquid cooling system, generally denoted by reference numeral 76, connected to the pump arrangement 10. Accordingly, the liquid cooling system serves as the first liquid transport circuit. Coolant from the engine 71 passes into an inlet 78 of the pump arrangement 10 and exits the arrangement via the outlet 21. Downstream of the pump arrangement there is located a thermostat 80 to divert flow either along a bypass conduit 82 or through a heat exchanger 84. After flowing through either the bypass conduit or the heat exchanger, the coolant is returned to the engine 71 via a return conduit 86. It is to be understood that the invention is not restricted to the embodiments described above and shown in the drawings, but may be varied within the scope of the appended claims. For example, although the pump arrangement has been described in an application in which two different liquids are pumped, it is to be understood that the liquids of the first and second liquid transport circuits may be of the same type. Important for the invention is only that the liquids of the two circuits are maintained in their respective circuits at least through the pump arrangement without mixing taking place.

Claims: CLAIMS 1. A pump arrangement (10) comprising a housing (12); a first pumping chamber (14) within said housing, said first pumping chamber being adapted to be connected to a first liquid transport circuit; a drive shaft (18) carried by said housing; first pumping means (16) arranged for rotation within said first pumping chamber (14), said first pumping means being driven by said drive shaft; a second pumping chamber (22) separated from said first pumping chamber by said housing (12) such that said housing forms a common separation wall (24), said second pumping chamber being adapted to be connected to a second liquid transport circuit, said second pumping chamber (22) accommodating second pumping means (26) being driven by said drive shaft; characterized in that said second pumping means is driven by said drive shaft (18) via a magnetic coupling (32), the coupling comprising a driver rotor (34) connected to said drive shaft (18) and a driven rotor (36) carried by said housing (12), said driven rotor driving said second pumping means (26), said driver rotor (34) and said driven rotor (36) being separated by a separation wall assembly (48) serving as a static seal to hermetically seal the second pumping chamber from said drive shaft. 2. The pump arrangement as claimed in claim 2, characterized in that said driver rotor (34) supports a number of first magnets (40) arranged circumferentially on said driver rotor, and in that said driven rotor (36) supports a number of second magnets (42) arranged circumferentially on said driven rotor. 3. The pump arrangement as claimed in claim 2, characterized in that said number of first magnets (40) on said driver rotor are held in a first magnet holder assembly (44), in that said number of second magnets (42) on said driven rotor are held in a second magnet holder assembly (46), and in that said first and second magnet holder assemblies are substantially radially aligned. 4. The pump arrangement as claimed in claim 3, characterized in that said first magnet holder assembly (44) is arranged on a radially inwardly facing surface of said driver rotor (34), and in that said second magnet holder assembly (46) is arranged on a radially outwardly facing surface of said driven rotor (36). 5. The pump arrangement as claimed in any one of the preceding claims, characterized in that said separation wall assembly (48) has an annular portion (50) arranged substantially parallel to said drive shaft (18), said annular portion passing through a gap between said first and second magnet holder assemblies (44, 46), in that at a first axial end of said annular portion (50), said separation wall assembly has a radially outwardly extending flange (52) partially delimiting said second pumping chamber (22), and in that at a second axial end of said annular portion (50), said assembly has a radially inwardly extending flange (54) comprising sealing means 56 for sealing against said housing (12). 6. The pump arrangement as claimed in claim 5, characterized in that said separation wall assembly (48) is made from steel. 7. The pump arrangement as claimed in any one of claims 3 to 6, characterized in that said housing (12) and said first and second magnet holder assemblies (44, 46) are made from aluminium. 8. A fuel delivery system comprising the pump arrangement as claimed in any one of the preceding claims. 9. The fuel delivery system as claimed in claim 8, said system further comprising a fuel reservoir (64) connected to a suction side (60) of said pump arrangement (10), a fuel delivery line (66) connected to an output side (62) of said pump arrangement, a fuel filter (68) in said delivery line, a number of fuel injectors (70) connected to said delivery line downstream of said fuel filter, and a return line (72) from said number of injectors to said suction side (60) of said pump arrangement. 10. The fuel delivery system of claim 9, wherein said magnetic coupling in said pump arrangement restricts the amount of torque transmitted to the driven rotor such that a maximum pressure of about 9 bar is attained at said output side (62) of said pump. 1 1. A liquid cooling system comprising the pump arrangement as claimed in any one of claims 1 to 7. 12. A vehicle comprising the fuel delivery system as claimed in claims 8 to 10 and the liquid cooling system as claimed in claim 11.

Inventors: HAAKANSSON NILS-OLOF, LARSSON LEIF, HAAKANSSON, NILS-OLOF, LARSSON, LEIF
Applicants: HAAKANSSON NILS OLOF, LARSSON LEIF, VOLVO LASTVAGNAR AB, HAAKANSSON, NILS-OLOF, LARSSON, LEIF
Application year: 1999
Main classification: F01P5
IPC codes: F01P5, F02M37, F04C11, F04D13