Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M59/00—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps
  • F02M59/20—Varying fuel delivery in quantity or timing
  • F02M59/34—Varying fuel delivery in quantity or timing by throttling of passages to pumping elements or of overflow passages, e.g. throttling by means of a pressure-controlled sliding valve having liquid stop or abutment
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M59/00—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps
  • F02M59/20—Varying fuel delivery in quantity or timing
  • F02M59/205—Quantity of fuel admitted to pumping elements being metered by an auxiliary metering device
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M59/00—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps
  • F02M59/44—Details, components parts, or accessories not provided for in, or of interest apart from, the apparatus of groups F02M59/02 - F02M59/42; Pumps having transducers, e.g. to measure displacement of pump rack or piston
  • F02M59/46—Valves
  • F02M59/462—Delivery valves
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M2700/00—Supplying, feeding or preparing air, fuel, fuel air mixtures or auxiliary fluids for a combustion engine; Use of exhaust gas; Compressors for piston engines
  • F02M2700/13—Special devices for making an explosive mixture; Fuel pumps
  • F02M2700/1317—Fuel pumpo for internal combustion engines
  • F02M2700/1352—Fuel pump with a constant stroke piston without control means

Definitions

• This invention relates to a pumping head for a fluid pump.
• the invention relates to a pumping head suitable for use in a high-pressure fuel pump of a fuel injection system for an internal combustion engine.
• FIG. 1 of the accompanying drawings is a schematic diagram of a conventional fuel injection system 10 for an internal combustion engine.
• the fuel injection system 10 comprises a plurality of fuel injectors 12. Each injector 12 is arranged to deliver an atomised spray of high-pressure fuel to a respective combustion chamber (not shown) of the engine.
• the injectors 12 receive fuel at high pressure from an accumulator volume or rail 14, by way of high-pressure supply lines 16.
• the rail 14 comprises a reservoir for high-pressure fuel. Delivery of fuel from the injectors 12 is controlled by an electronic control unit 18. When a fuel injection from one of the injectors 12 is required, the electronic control unit 18 sends an actuation signal to the injector 12, which causes actuation of a delivery valve (not shown) of the injector 12. Fuel is pumped to the rail 14 from a storage tank 20 by a fuel pump assembly 22.
• the fuel pump assembly 22 includes a low-pressure transfer pump 24, which serves to convey fuel from the tank 20 to the pump assembly 22, and a high-pressure pump 26 which elevates the pressure of the fuel to the injection pressure, typically of the order of 2000 bar. Fuel is conveyed from the tank 20 to the pump assembly 22 by way of a low- pressure fuel line 28, and from the pump assembly 22 to the rail by way of a high- pressure fuel line 30.
• An inlet metering valve 32 under the control of the engine control unit 18, is provided between the transfer pump 24 and the high-pressure pump 26 of the pump assembly 22.
• the inlet metering valve 32 determines how much fuel reaches the high-pressure pump 26, for subsequent pressurisation and delivery to the rail 14.
• the fuel pressure in the rail 14 is regulated to a target value by the electronic control unit 18.
• a pressure-limiting valve 36 and return line 38 prevent the rail pressure exceeding a pre-determined acceptable level.
• the high-pressure pump 26 comprises a pumping head 50, shown schematically in Figure 2, which is arranged to receive a reciprocable pumping plunger or pumping element 52.
• the pump 26 further comprises a drive assembly (not shown) for driving reciprocal movement of the pumping element 52 along a pumping axis Q.
• the pumping head 50 comprises a housing 56 that includes a blind bore 58.
• the pumping element 52 is slidably received within the bore 58.
• a pumping chamber 60 at the blind end of the bore 58 is defined in part by the pumping member 52 and in part by the bore 58.
• the pumping head 50 further comprises a spring-biased inlet valve 62 and a spring- biased outlet valve 64.
• a spring-biased inlet valve 62 When the pumping element 52 moves downwards (referred to as a filling stroke or return stroke of the pumping element 52), the volume of the pumping chamber 60 increases, the outlet valve 64 closes, and the inlet valve 62 opens when the pressure differential across it reaches a first predetermined level. Fuel is then admitted to the pumping chamber 60 from a fuel supply port 63, through the inlet valve 62. The fuel supply port 63 is fed with fuel from the inlet metering valve (32 in Figure 1).
• the pumping element 52 moves upwards (referred to as a pumping stroke or forward stroke of the pumping element 52), the volume of the pumping chamber 60 decreases, the inlet valve closes 62, and the pressure of fuel in the pumping chamber 60 increases.
• the outlet valve 64 is arranged to open at a second pre-determined pressure. Fuel is then delivered through the outlet valve 64 from the pumping chamber 60 at the second pre-determined pressure, for delivery to the fuel rail 14 through an outlet port 65.
• the second pre-determined pressure at a high level, for example 2000 bar or more, pressurisation of the fuel rail 14 to the desired level can be achieved.
• the pumping head 50 is generally T-shaped, so that the housing 56 comprises a vertically-extending portion 56a and first and second horizontally-extending portions 56b, 56c that extend in opposite directions from the vertically-extending portion 56a.
• the bore 58 extends within the vertically-extending portion 56a of the housing 56, and the inlet and outlet valves 62, 64 are received in the first and second horizontally-extending portions 56b, 56c, respectively.
• a first high-pressure seal 70 is provided to prevent leakage of fuel from the pumping chamber 60 past the inlet valve 62
• a second high- pressure seal 72 is provided to prevent leakage of fuel from the pumping chamber 60 past the outlet valve 64.
• the first horizontally-extending portion 56b of the housing 56 includes an inlet passage 74 that extends laterally from the pumping chamber 60.
• the inlet passage 74 opens into an enlarged-diameter inlet valve bore 76 that houses the inlet valve 62, so that, when the inlet valve 62 is open, fuel can flow from the supply port 63, through the inlet valve 62 and the inlet passage 74 into the pumping chamber 60.
• a first internal shoulder 78 of the housing 56 is defined where the relatively large diameter inlet valve bore 76 meets the relatively small diameter inlet passage 74.
• the inlet valve bore 76 includes an internally-threaded region 76a.
• the inlet valve 62 has an externally-threaded region that engages with the threaded region 76a of the inlet valve bore 76 to secure the inlet valve 62 in the housing 56.
• an end face of the generally cylindrical inlet valve 62 is clamped against the first shoulder 78 of the housing 56 to form the first high-pressure seal 70.
• the inlet valve 62 can be screwed into the inlet valve bore 76 to a sufficient degree to ensure that no fuel leaks past the first high-pressure seal 70.
• a sealing washer may also be provided between the inlet valve 62 and the shoulder 78.
• the outlet valve 86 comprises a generally cylindrical end member 64a, a valve ball 64b, and a spring 64c that acts between the valve ball 64b and the end member 64a.
• an outlet passage 84 extends laterally from the pumping chamber 60 to open into an enlarged-diameter outlet valve bore 86 that houses the end member 64a of the outlet valve 64.
• the outlet passage 84 includes a first portion 84a adjacent to the pumping chamber 60, and a second portion 84b with a larger diameter than the first portion 84a.
• a valve seat 84c for the valve ball 64b is provided in the outlet passage 84, where the first portion 84 meets the second portion 84b.
• outlet valve 64 When the outlet valve 64 is open (i.e. when the valve ball 64b is lifted off the valve seat 84c), fuel can flow from the pumping chamber 60, through the outlet passage 84 and the outlet valve 64 and out of the housing 56 via the outlet port 65.
• a second internal shoulder 88 of the housing 56 is defined where the relatively large diameter outlet valve bore 86 meets the relatively small diameter outlet passage 84.
• the outlet valve bore 86 At its outside end, the outlet valve bore 86 includes an internally-threaded region 86a that engages with an externally-threaded region of the outlet valve 64 to secure the outlet valve 64 in the housing 56.
• an end face of the generally cylindrical outlet valve 64 is clamped against the second shoulder 88 of the housing 56, with sufficient clamping force being applied to ensure that no fuel leaks past the second high-pressure seal 72.
• a sealing washer could be used between the outlet valve 64 and the second shoulder 88.
• a further high- pressure seal (not shown) is required to seal the connection between the outlet port 65 and a fuel line (30 in Figure 1) that connects the head 50 to the fuel rail (14 in Figure 1), in use.
• high-pressure seals 70, 72 adds substantial cost and complexity to the pumping head 50, particularly in very high- pressure applications, for example at pressures of 2000 bar or more. Furthermore, because the high-pressure seals 70, 72 are subject to high stresses during manufacture and use, they represent a potential source of failure of the pumping head.
• the requirement to shape the intersections between the passages, for example by mechanical or electrochemical machining, also adds cost and complexity to the pumping head 50, and in particular to the process for manufacturing such a pumping head.
• the present invention resides in a pumping head for a high-pressure fuel pump, comprising a head housing including a first bore and an integral outlet port defining a second bore, a pumping element slidably received in the first bore and arranged for reciprocal linear movement along a pumping axis, a pumping chamber defined in part by the pumping element and in part by the first bore, wherein a forward stroke of the pumping element causes a reduction in volume of the pumping chamber, and a return stroke of the pumping element causes an increase in volume of the pumping chamber.
• the pumping head further comprises inlet means for delivering fluid at relatively low pressure to the pumping chamber during the return stroke, and outlet means for receiving fluid at relatively high pressure from the pumping chamber during the forward stroke and for delivering the relatively high-pressure fluid through the outlet port.
• the outlet means comprises a passage defined in the housing that opens into the pumping chamber, the passage being substantially coaxial with the pumping axis, and an outlet valve for controlling the flow of fluid from the pumping chamber along a fluid flow path substantially parallel to the pumping axis.
• the outlet valve comprises a valve body received in the second bore, and a valve seat defined by the housing at an end of the passage.
• the outlet means is arranged to convey fluid from the pumping chamber through the outlet port in a fluid flow direction that is substantially coaxial with the pumping axis.
• stress concentrations in the pumping head are minimised, and in particular are reduced compared to known arrangements in which fluid is conveyed from a pumping chamber to an outlet in a direction that is, for example, perpendicular to the pumping axis.
• the housing is provided with an integral outlet port having a second bore to receive the valve body of the outlet valve, and because the valve seat for the outlet valve is defined by the housing at the end of the passage, there are no leakage paths for high-pressure fluid associated with the outlet means. Instead, the only path by which fluid can leave the housing is by way of the outlet port. Accordingly, when a fuel line is connected to the outlet port in use to receive fuel from the outlet, the seal between the fuel line and the outlet port is sufficient to prevent any leakage of high-pressure fuel, and it is not necessary to provide any further high- pressure seals associated with the outlet means. In particular, the requirement for a high- pressure seal to seal the valve body in the pumping head can be avoided.
• the pumping element cooperates with the inlet means to restrict the flow of fluid between the inlet means and the pumping chamber during at least a part of the forward stroke so that the inlet means is not exposed to the relatively high-pressure fluid.
• fluid in the pumping chamber is pressurised as a result of the reduction in volume of the pumping chamber, so that fluid is delivered to the outlet means at high pressure.
• the pumping element restricts flow between the pumping chamber and the inlet means during the forward stroke in this embodiment, the entire inlet means can be substantially isolated from the high fluid pressures that arise in the pumping chamber and, accordingly, the housing is not subjected to high stresses around the inlet means. The likelihood of fatigue damage is therefore reduced. It is a further benefit of this embodiment of the invention that a high-pressure seal associated with the inlet means is not necessary.
• the inlet means is substantially isolated from the pumping chamber, the effective volume of fluid that is in communication with the pumping chamber during the forward stroke (known as the 'dead volume') is reduced.
• the dead volume and therefore the volume of fluid that must be compressed to achieve a given fluid pressure increase, a more efficient pumping action is achieved.
• the pumping head of the present invention is therefore less complex, more efficient, more reliable and less costly to manufacture than previously-known pumping heads for example of the type shown in Figure 2.
• the inlet means preferably comprises at least one inlet passage that communicates with the bore.
• the pumping element may occlude the or each inlet passage to restrict the flow of fluid from the inlet passage to the pumping chamber.
• the second bore is preferably substantially coaxial with the pumping axis.
• the valve body may be an interference fit in the second bore.
• the outlet port may be arranged to engage with a connector for a high-pressure fuel line.
• the outlet port may be in the form of a male connector for engagement with a female connector of the high-pressure fuel line.
• the outlet form is externally threaded to engage with an internally-threaded connector of the high- pressure fuel line.
• the outlet valve may comprise a valve element, and the valve element may be moveable in a direction that is substantially coaxial with the pumping axis for controlling the flow of fluid from the pumping chamber to the outlet.
• the fluid flow path in the outlet valve may comprise a passage in the valve body.
• the passage is preferably substantially coaxial with the pumping axis.
• a second aspect of the present invention resides in a high-pressure pump for a fuel injection system, comprising a pumping head according to the first aspect of the invention, a pump body comprising a pump housing defining an internal volume and including an aperture for receiving the pumping head, and a drive mechanism housed in the internal volume and arranged to drive the pumping element in reciprocal linear movement along the pumping axis.
• the inlet means is in communication with the internal volume.
• the fluid to be pumped may be a lubricating fluid that lubricates the drive mechanism in use.
• the aperture may define a chamber, and the inlet means may communicate with the internal volume by way of the chamber.
• the pump housing comprises a supply conduit for delivering fluid to the inlet means.
• the pump may comprise sealing means to prevent communication between the inlet means and the internal volume.
• the present invention also extends, in a third aspect, to a fuel injection system comprising a high-pressure pump comprising a pumping head according to the first aspect of the invention, or a high-pressure pump according to the second aspect of the invention.
• the fuel injection system may include a fluid source, and an inlet metering valve for receiving fluid from the fluid source and for delivering the fluid to the inlet means of the pumping head.
• the inlet metering valve may be remote from the pumping head.
• the invention resides in a pumping head for a high-pressure fuel pump, comprising a head housing having a bore, a pumping element slidably received within the bore and arranged for reciprocal linear movement along a pumping axis, and a pumping chamber defined in part by the pumping element and in part by the bore, wherein a forward stroke of the pumping element causes a reduction in volume of the pumping chamber and a return stroke of the pumping element causes an increase in volume of the pumping chamber.
• the pumping head further comprises inlet means for delivering fluid to the pumping chamber during the return stroke, and outlet means for receiving fluid from the pumping chamber during the forward stroke and for delivering fluid to an outlet of the pumping head.
• the outlet means is arranged to convey fluid from the pumping chamber to the outlet in a fluid flow direction that is substantially coaxial with the pumping axis.
• the stress concentrations that arise in the housing are reduced compared to arrangements in which fluid is conveyed by the outlet means in a fluid flow direction that is not substantially coaxial with the pumping axis.
• the outlet is axially aligned with the pumping axis.
• the pumping head can be fitted to the pump housing in any angular orientation.
• this flexibility in angular orientation means that misalignment of the pumping plunger, for example due to manufacturing tolerances, is easier to accommodate.
• a fifth aspect of the invention resides in a pumping head for a high-pressure fuel pump, comprising a head housing having a bore, a pumping element slidably received within the bore and arranged for reciprocal linear movement along a pumping axis, and a pumping chamber defined in part by the pumping element and in part by the bore, wherein a forward stroke of the pumping element causes a reduction in volume of the pumping chamber and a return stroke of the pumping element causes an increase in volume of the pumping chamber.
• the pumping head further comprises inlet means for delivering fluid to the pumping chamber during the return stroke, an outlet port for connection to a high-pressure fluid line, and an outlet valve comprising an outlet valve body housed within the outlet port. The outlet valve is arranged to control the flow of fluid from the pumping chamber to the outlet port through the outlet valve body during the forward stroke.
• the present invention resides in a pumping head for a high-pressure fuel pump, comprising a head housing having a bore, a pumping element slidably received within the bore and arranged for reciprocal linear movement along a pumping axis, and a pumping chamber defined in part by the pumping element and in part by the bore, wherein a forward stroke of the pumping element causes a reduction in volume of the pumping chamber and a return stroke of the pumping element causes an increase in volume of the pumping chamber.
• the pumping head further comprises inlet means for delivering fluid at relatively low pressure to the pumping chamber during the return stroke, and outlet means for receiving fluid at relatively high pressure from the pumping chamber during the forward stroke and for delivering the relatively high-pressure fluid to an outlet of the pumping head.
• the pumping element cooperates with the inlet means to restrict the flow of fluid between the inlet means and the pumping chamber during at least a part of the forward stroke so that the inlet means is not exposed to the relatively high-pressure fluid.
• FIG. 1 of the accompanying drawings which has been referred to above, is a schematic diagram of a conventional fuel injection system of an internal combustion engine having a conventional high-pressure fuel pump.
• Figure 2 which has also been referred to above, is a schematic cross-sectional view of a pumping head of a conventional high-pressure fuel pump for use in the fuel injection system of Figure 1.
• Figure 3 is a cross-sectional view of a pumping head according to the invention.
• Figure 4 is a cross-sectional view of another pumping head according to the invention.
• a first embodiment of the present invention is illustrated in Figure 3.
• a pumping head 100 is mounted to a pump housing 102 (shown only in part in Figure 3) of a high-pressure fuel pump, for use in a fuel injection system for an internal combustion engine.
• the pump housing 102 houses a drive mechanism (not shown) for a pumping plunger or pumping element 104.
• the drive mechanism which may be of a known type, comprises a cam and follower arrangement that drives the pumping element 104 in reciprocal linear motion along a pumping axis A, in use.
• the drive mechanism is contained within an internal volume 105 of the pump housing 102.
• the pumping head 100 comprises a head housing 101 of generally tubular form, and is arranged so that the tube axis of the head housing 101 is coaxial with the pumping axis A.
• the pumping head 100 comprises a pumping bore 106 that extends upwardly from a lower end of the head housing 101 , in the orientation shown in Figure 3.
• the pumping bore 106 slidably receives the pumping element 104, and a pumping chamber 1 10 is defined in part by an end face 108 of the pumping element 104 and in part by the wall of the pumping bore 106.
• An outlet valve bore 1 12 extends downwardly into the head housing 101 from its upper end.
• the outlet valve bore 1 12 houses an outlet valve 1 14 having a generally tubular valve body 1 16 and a spherical valve ball 1 18.
• the valve ball 118 is biased away from the valve body 1 16 by a biasing spring 120, which acts between the ball 1 18 and an internal collar 122 of the valve body 116.
• the biasing spring 120 is received in a spring chamber 121 defined in part by the bore of the valve body 1 16, in part by the collar 122, and in part by the lower end of the outlet valve bore 112.
• a central passage or opening 123 in the collar 122 provides fluid communication between the spring chamber 121 and the upper end of the head housing 101.
• the pumping chamber 1 10 communicates with the outlet valve bore 1 12 by way of a flow passage 124 in the head housing 101 that extends coaxially with the pumping axis A.
• An upper end of the flow passage 124, furthest from the pumping chamber 1 10, is shaped to form a valve seat 126 for the ball 1 18.
• An upper portion of the head housing 101 comprises a tubular outlet port 128 that defines an outlet of the pumping head 100.
• the outlet port 128 is an integral part of the head housing 101.
• the port 128 is externally threaded to accept a connector for a high- pressure fuel line (not shown), although it will be appreciated that alternative connection arrangements could be provided.
• the high-pressure fuel line delivers fuel from the pumping head 100 to a fuel rail (not shown) of a fuel injection system.
• the outlet valve bore 112 is formed within the outlet port 128.
• the outlet valve body 116 is an interference fit within the outlet valve bore 1 12.
• the fluid pressure acting on the upwardly-facing surfaces of the outlet valve body 1 16 as a result of fluid in the fuel line is similar to the fluid pressure acting on the downwardly-facing surfaces of the outlet valve body 116. It is not therefore necessary to secure the outlet valve body 1 16 in the outlet valve bore 1 12 with a high-strength threaded connection or similar, although it will be appreciated that such a securing means could be used if desired.
• the pumping head 100 requires only one high-pressure seal between the outlet port 128 of the head housing 101 and the fuel line (not shown), which serves to seal the outlet valve 114 in the housing as well as to connect the head 100 to the fuel line.
• An inlet passage 130 provides fluid communication between the pumping bore 106 and the outer surface 132 of the head housing 101.
• the inlet passage 130 extends radially through the wall of the head housing 101 , and is arranged to receive fluid at relatively low pressure from within the internal volume 105 of the pump housing 102. Only one inlet passage 130 is shown in Figure 3, but it will be appreciated that more radial inlet passages could be provided at the same axial position but different radial positions in the head housing 101.
• the head housing 101 is mounted in an aperture 134 in the pump housing 102 and is held in place by suitable retaining means.
• a lower portion of the head housing 101 may be externally threaded for engagement with an internally-threaded portion of the aperture 134.
• the threaded portions are not shown in Figure 3.
• the head housing 101 includes an external collar 136 that abuts the pump housing 102 around the periphery of the aperture 134, in use.
• a lower face of the collar 136 and an upper face of the pump housing 102 are provided with annular recesses 138, 139 that together receive a sealing washer 140, such as an ⁇ ' ring.
• a fluid seal 142 is formed between the head 100 and the pump housing 102.
• This seal 142 is subjected only to relatively low fluid pressures in use, so need not be adapted to resist the leakage of high-pressure fluid.
• the collar 136 may be provided with flats to serve as a fixing nut for the pumping head 100.
• a lower part 144 of the aperture 134 is formed with an increased diameter, relative to the remaining part of the aperture 134.
• a clearance 146 between the increased-diameter part 144 of the aperture and the head housing 101 defines an annular passage through which fluid can reach the inlet passage 130.
• Fluid to be pumped is delivered to the internal volume 105 of the pump housing 102 from a fluid source, such as a fuel tank, by way of an inlet metering valve (not shown).
• a fluid source such as a fuel tank
• the inlet metering valve controls the delivery of fluid to the inlet passage 130.
• the pumping element 104 reciprocates cyclically within the pumping bore 106 to define a pumping cycle comprising a forward or pumping stroke and a return or filling stroke.
• the pumping element 104 moves upwards to reduce the volume of the pumping chamber 1 10.
• the pumping element 104 moves downwards to increase the volume of the pumping chamber 110.
• the furthest upward extent of travel of the pumping element 104, reached at the end of the forward stroke is known as the top dead centre (TDC) position
• TDC top dead centre
• BDC bottom dead centre
• the inlet passage 130 is positioned so that, during a first portion of the pumping cycle, the pumping element 104 occludes the opening of the inlet passage 130 into the pumping bore 106. Accordingly, during this first portion of the pumping cycle, the flow of fluid between the inlet passage 130 and the pumping chamber 110 is prevented or at least substantially restricted.
• the first portion of the pumping cycle includes the end of the forward stroke and the start of the return stroke, when the pumping element 104 is close to or at TDC.
• the position of the pumping element 104 is such the opening of the inlet passage 130 into the pumping bore 106 is not occluded by the pumping element 104.
• fluid in this second portion of the pumping cycle, fluid can flow substantially freely between the inlet passage 130 and the pumping chamber 130.
• the second portion of the pumping cycle includes the end of the return stroke and the start of the forward stroke, when the pumping element is close to or at BDC.
• the volume of the pumping chamber 110 increases. Part-way through the return stroke, the end 108 of the pumping element 104 moves past the opening of the inlet passage 130, so that fluid can flow from the inlet passage into the valve bore 106, and consequently into the pumping chamber 110.
• the volume of the pumping chamber 1 10 increases until the pumping element 104 reaches BDC. Therefore, the effect of the return stroke is to fill the pumping chamber 110 with fluid from the inlet passage 130.
• the forward stroke of the pumping cycle begins, and the pumping element 104 moves upwards to decrease the volume of the pumping chamber 1 10.
• the end 108 of the pumping element 104 passes the inlet passage 130 so that communication between the inlet passage 130 and the pumping chamber 1 10 is substantially restricted.
• the pressure of fluid in the pumping chamber 110 increases until the pressure acting on the valve ball 1 18 is sufficient to overcome the force of the biasing spring 120, allowing the ball 1 18 to move away from its seat 126.
• the outlet valve 1 14 opens to allow high-pressure fluid to flow from the pumping chamber 110 out of the pumping head 100.
• the pumping element 104 reaches TDC, the decrease in volume of the pumping chamber 1 10 ceases, and the inlet valve 114 closes as the return stroke begins again. Because the pumping element 104 occludes the inlet passage 130 during the last stages of the forward stroke, when the pressure in the pumping chamber 1 10 approaches its maximum value, the inlet passage 130 is isolated or protected from the highest pressures that occur within the pumping head 100. Advantageously, therefore, stress concentrations that arise at the intersection between the inlet passage 130 and the pumping bore 106 are unlikely to give rise to failure of the pumping head 100.
• the inlet passage 130 is protected from the pressure in the pumping chamber 1 10 during the period immediately before and while the outlet valve 1 14 is open, as the pumping element 104 approaches TDC. It is therefore preferable that the first portion of the pumping cycle, in which the inlet passage 130 is occluded by the pumping element 104, is a majority portion of the pumping cycle.
• the inlet passage 130 is occluded by the valve element 104 over a period of the pumping cycle from approximately 140 degrees before TDC to approximately 140 degrees after TDC.
• the pumping element 104 is a sliding fit in the pumping bore 106, a leakage flow of fluid is likely to be present between the pumping element 104 and the pumping bore 106. Accordingly, when the pumping element 104 occludes the inlet passage 130, flow between the pumping chamber 1 10 and the inlet passage 130 is not expected to be completely stopped. Instead, a small leakage flow may still be present. However, the benefit of the invention still arises because, when the inlet passage 130 is occluded, the pressure drop between the pumping chamber 1 10 and the inlet passage 130 is substantial. At the start of the return stroke, the outlet valve 114 closes and the inlet passage 130 is still occluded by the pumping element 104.
• the initial increase in volume in the pumping chamber 110 that occurs before the inlet passage 130 opens results in a partial vacuum being drawn in the pumping chamber 110.
• the pumping element 104 clears the inlet passage 130, so that the inlet passage 130 opens, fluid can then flow into the pumping chamber 1 10 from the inlet passage 130 to relieve the partial vacuum.
• the outlet valve bore 1 12, the flow passage 124 between the pumping chamber 1 10 and the outlet valve bore 1 12, the axis along which the valve ball 1 18 moves as it disengages and reengages with its seat 126, and the opening 123 in the collar 122 are all aligned with the pumping axis A.
• this configuration means that the pumping head 100 is relatively simple to manufacture.
• the pumping head 100 of the first embodiment of the invention is particularly suitable for use in diesel fuel injection systems, in which the fluid to be pumped is diesel fuel.
• the diesel fuel has lubricating properties, and therefore the fuel conveniently lubricates the drive mechanism for the pumping element 104 as the fuel flows through the internal volume 105 of the pump housing 102 before it enters the supply passage 130 of the pumping head 100.
• a second embodiment of the invention will now be described with reference to Figure 4, which shows a pumping head 200 mounted to a pump housing 202 of a high-pressure fuel pump.
• the pumping head 200 of this second embodiment of the invention is similar in most respects to the pumping head 100 of the first embodiment of the invention, and accordingly only the differences between the embodiments will be described in detail.
• reference numerals used in Figure 4 that are not specifically referred to below relate to features that are substantially the same as the components with like reference numerals already described above with reference to Figure 3.
• the pumping head 200 and pump housing 202 arrangement of Figure 4 differs from the arrangement of Figure 3 in the way in which fluid is supplied to the inlet passage, as will now be explained.
• the head housing 201 includes inlet passages 230 that extend radially from the plunger bore 106 to the outer surface 232 of the head housing 201.
• Two inlet passages 230 are shown in Figure 4, but it will be appreciated that fewer or more radial inlet passages could be provided at the same axial position but different radial positions in the head housing 201.
• Fluid is supplied to the inlet passages 230 in this case not from the pump housing volume 105, but from a supply conduit 250 provided in the pump housing 202.
• the pumping head 200 is received in an aperture 234 in the pump housing 202.
• the aperture 234 has a substantially uniform diameter through the wall of the pump housing, and the supply conduit 250 opens on to the internal surface 235 of the aperture 234.
• the axial position of the supply conduit 250 corresponds to the axial location of the inlet passages 230, when the head 200 is mounted in the pump housing 202.
• An annular channel 252 extends around the head housing 201 , and the inlet passages 230 and the supply conduit 250 each open into the annular channel 252. Accordingly, fluid is delivered to the pumping bore 106 and hence to the pumping chamber 1 10 from the supply conduit 250 via the annular channel 252 and the inlet passages 230.
• first and second sealing grooves 254, 256 extend annularly around the head housing 201 above and below the annular groove 252. ⁇ ' rings or other suitable sealing members (not shown) are received in the sealing grooves 254, 256 to guard against loss of fluid from the supply conduit 250.
• a low-pressure seal 142 may also be formed between the collar 136 of the head housing 201 and the pump body 202, as in the first embodiment, in which case the low-pressure seal 142 acts as an additional sealing means for the pump housing 202.
• the pumping head 200 of the second embodiment of the invention is suitable for use in fuel injection systems in which the fluid to be pumped does not lubricate the drive mechanism for the pumping element 104.
• a separate lubricating oil may be used to lubricate the drive mechanism, and it is desirable to avoid mixing of the fuel and the lubricating oil.
• the pumping head may include inlet means that incorporate a conventional inlet valve that delivers fluid to the inlet passage.
• the inlet valve may be a non-return valve, to prevent the back-flow of fluid from the pumping chamber to the inlet means through the inlet passage.
• the outlet valve may be of a different type to that described above.
• a ball valve instead of a ball valve, a needle valve, diaphragm valve or any other suitable valve may be provided.
• the pumping head may be provided with outlet means in the form of passages without an outlet valve, in which case a suitable non-return valve could be included in the fuel injection system downstream of the pumping head.
• inlet means such as a supply passage that is occluded by the pumping element during the forward stroke in combination with an outlet means arranged so that fluid flows out of the pumping chamber and through the head in a flow direction that is substantially aligned with the pumping axis A
• outlet means arranged so that fluid flows out of the pumping chamber and through the head in a flow direction that is substantially aligned with the pumping axis A
• the outlet means may be arranged so that high-pressure fluid flows out of the pumping chamber through a passage that intersects with the pumping bore at a 90° angle.
• the outlet means may be arranged so that high-pressure fluid flows out of the pumping chamber in a direction having an axis that is offset from and/or at any suitable angle to the pumping axis A.
• an outlet means comprising an outlet valve located within an outlet port of the housing to avoid the need for a dedicated high- pressure seal to seal the outlet valve in the housing, even if the fluid flow direction in the outlet means is not aligned with the pumping axis A and/or the inlet means is not occluded by the pumping element during the forward stroke.
• the pumping head of the present invention is not limited to use in a fuel injection system, but would be suitable for any application in which a high- pressure pumping head with good reliability and a simple design is desirable.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Fuel-Injection Apparatus (AREA)

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Citations (12)

• 2011
  • 2011-02-28 EP EP11156276A patent/EP2492492A1/de not_active Withdrawn
• 2012
  • 2012-02-27 WO PCT/EP2012/053284 patent/WO2012116959A1/en active Application Filing

Patent Citations (12)

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