Radial Piston Pump

Abstract

A radial piston pump (1) is disclosed that includes a rotor (2) mounted for rotation on a pintle (204). The rotor includes a plurality of piston chambers (18) with pistons (20) mounted for reciprocating movement in each of said chambers (18). The pump (1) includes at least one supply flow passage connecting the piston chambers (18) to a source of low pressure fluid, at least one outlet flow passage through which high pressure fluid from the piston chambers (18) is discharged from the pump (1), and at least one auxiliary flow passage connecting another component of the pump (1) to the piston chambers (18). The pintle (204) includes a plurality of flow galleries (36), including at least one supply flow gallery (287) forming a portion of the supply flow passage, at least one outlet flow gallery (283) forming a portion of the outlet flow passage, and at least one auxiliary flow gallery (285) forming a portion of the auxiliary flow passage. Thus, the radial piston pumps disclosed herein can use a pintle as a fluid manifold that supplies fluid to or from the piston and to or from at least one other component of the pump. Hydraulic power packs (270), braking systems (260), active suspension systems (170) and flight control systems (180) that include such pumps, as well as methods of manufacturing such pumps, are also disclosed.

Description

[Technical field]

[0001] The present invention relates to a radial piston pump. More specifically, but not by way of limitation, the present invention relates to a radial piston pump having a first set of pistons and a second set of pistons and a valve configured to control fluid flow to or from both the first set of pistons and the second set of pistons. In another aspect, the present invention relates to a radial piston pump having a common rotor between a motor and a pump. In yet another aspect, the present invention relates to a radial piston pump having a pintle with at least one auxiliary flow gallery. The present invention also relates to a hydraulic power pack, a braking system, an active suspension system and / or a flight control system including such a radial piston pump, a method of operating such a piston pump, and a method of manufacturing such a piston pump. [Background technology]

[0002] Radial piston pumps are used in a wide range of applications including automotive and aerospace applications.

[0003] Typically, radial piston pumps include multiple pistons mounted in radially extending piston chambers formed in a piston housing. The piston housing may include a hollow center in which a shaft is eccentrically mounted. Alternatively, the piston housing may be eccentrically mounted in a ring. Movement of the pistons may be produced by rotating the piston housing relative to the shaft and / or ring. An internal (or internal) impingement pump may be defined as a pump in which fluid flows into the pistons through the interior of the pump housing. An external (or external) impingement pump may be defined as a pump in which fluid flows to and from the pistons through structure disposed around the outside of the piston housing.

[0004] FIG. 1 shows a schematic diagram of the inside of a prior art impingement radial piston pump 1001. The pump 1001 comprises a cylindrical piston housing 1002 including a plurality of radially extending piston chambers 1018 formed within the body of the housing 1002. A piston 1020 forming part of a piston assembly 1019 is disposed within each piston chamber 1018. Each piston assembly 1019 includes a piston 1020 and a cam follower 1022 connected to the piston 1020. The cam follower 1022 is in contact with an inwardly facing cam surface 1024 that extends around the outside of the piston housing 1002. The radius of the cam surface 1024 varies periodically with distance around the circumference of the housing 1002.

[0005] In use, the piston housing 1002 rotates against the cam surface 1024. A spring (not shown) biases the piston 1020 radially outward from the piston chamber 1018, thus maintaining the cam follower 1022 in contact with the cam surface 1024. In some prior art pumps, a spring may not be necessary and centrifugal force, or the pressure of the liquid entering the piston chamber 1018, may be sufficient to maintain the follower in contact with the cam surface 1024. As a result of contact between the cam follower 1022 and the cam surface 1024, the piston 1020 is forced into the piston chamber 1018 along the portion of the cam surface 1024 where the radius of the cam surface decreases with the relative rotation of the housing 1002 and the cam surface 1024. As a result, any liquid present in the piston chamber 1018 is expelled from the piston chamber 1018 under pressure. Conversely, if the profile of the cam surface 1024 is configured such that the radius of the cam surface 1024 increases with rotation, the piston 1020 will move radially outward and fluid will be able to enter the piston chamber 1018. Thus, rotation of the piston housing 1002 against the changing profile of the cam surface 1024 causes the piston 120 to reciprocate within the piston chamber 1018, thereby moving fluid through the pump 1001. Fluid flows in and out of the piston chamber 1018 through the hollow center of the piston housing 1002 under the control of a series of check valves (not shown).

[0006] In many systems, pump selection is limited by available space and / or power. Thus, it is generally desirable to increase the efficiency of a pump, particularly for a range of speeds or a range of flow rates. Additionally or alternatively, it is generally desirable to reduce the size of the pump required for a given flow rate.

[0007] US Patent No. 5,399,363 (Domin Fluid Power Limited) discloses a radial pump or motor comprising a plurality of reciprocating elements, e.g. piston balls or rollers, arranged in at least two layers. Each reciprocating element of the at least two layers is arranged to follow a different cam surface. The pump may comprise at least two valves, each valve arranged to control fluid flow to or from a different one of the layers (or a different group of the layers), whereby each of the at least two layers can be switched between a pumping state and a non-pumping state by operating the associated valve. In this way, the capacity of the pump of US Patent No. 5,399,363 can be changed, improving efficiency over a wider range of speeds than a fixed displacement pump. It would be advantageous to provide a radial piston pump that is more compact and / or less mechanically complex for a given flow rate than the pump of US Patent No. 5,399,363, while providing the variable capacity of US Patent No. 5,399,363. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2017 / 098250 Brochure Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention aims to alleviate the above-mentioned problems. Alternatively or additionally, the present invention aims to provide an improved radial piston pump and / or an improved system incorporating a radial piston pump. [Means for solving the problem]

[0010] In a first aspect of the invention, there is provided a radial piston pump comprising a rotor having a plurality of piston chambers and a first set of pistons and a second set of pistons received within the piston chambers. The pump may further comprise a first cam surface and a second cam surface. The rotor may be mounted for rotation relative to the first cam surface and the second cam surface, the first cam surface being arranged to control radial movement of the first set of pistons and the second cam surface being arranged to control radial movement of the second set of pistons. The radial piston pump may comprise a valve configured to control fluid flow to both the first set of pistons and the second set of pistons. The radial piston pump may comprise a valve configured to control fluid flow from both the first set of pistons and the second set of pistons. The valve may be configured to switch the radial piston pump from a first configuration to a second configuration by altering fluid flow to or from the second set of pistons independently of the first set of pistons.

[0011] Thus, in a radial piston pump according to the present invention, the same valve can independently switch flow to or from both sets of pistons (e.g., switch flow to one set of pistons without substantially altering flow to or from the other set of pistons). Using a single valve to control the flows associated with the various different layers can provide a variable displacement pump with a reduced parts count (and therefore reduced mechanical complexity) compared to other variable displacement pumps and / or allows for a more compact variable displacement pump for a given flow rate.

[0012] The valves can be configured to switch the radial piston pump from a first configuration to a third configuration and / or a fourth configuration by altering the fluid flow to or from the first set of pistons independently of the second set of pistons. Thus, the same valves may enable three and / or four different operating modes of the pump. Thus, a pump according to the present invention may provide multiple operating modes while using the same valves for various different layers.

[0013] As used herein, the terms low pressure fluid and high pressure fluid refer to the flow before and after compression by a piston, respectively.

[0014] In the context of a valve configured to alter fluid flow to / from one set of pistons independently of another set of pistons, the term independently will be understood to require that the valve can substantially alter the fluid flow to one set of pistons (e.g., switch on, switch off, or route to a different destination) without significantly affecting the fluid flow to another set of pistons.

[0015] Modifying fluid flow to or from a set of pistons can include opening or closing flow paths to or from a set of pistons. Modifying fluid flow can include opening flow paths, thereby allowing fluid to flow to a set of pistons that did not receive fluid flow in the other configuration. Modifying fluid flow may include closing flow paths, thereby no longer allowing fluid to flow to a set of pistons that received fluid flow in the other configuration. Modifying fluid flow can include closing flow paths and opening different flow paths, thereby causing fluid to take different routes to or from a set of pistons, such as to allow fluid from different sources to be supplied to the set of pistons or fluid from the set of pistons to be delivered to different destinations.

[0016] In a first configuration, the valve may provide a fluid flow path to the first set of pistons but not the second set of pistons. In a second configuration, the valve may provide a fluid flow path to both the first and second sets of pistons. When the valve is configured to control the flow of fluid to the first and second sets of pistons, the valve may switch the pump between a first configuration in which fluid flows to the first set of pistons but not the second set of pistons, and a second configuration in which fluid flows to the second set of pistons. Thus, a variable displacement pump may be provided in which no fluid flows to the second set of pistons when power is not required. A variable displacement pump that does not flow to the set of pistons that is not required may achieve improved efficiency because the motor of such a pump does not need to overcome losses associated with pumping fluid through the second set of pistons.

[0017] The valve can be configured to switch the pump between a first configuration, a second configuration, and a third configuration in which fluid flows to the second set of pistons but not the first set of pistons.

[0018] In the first configuration, the valve may provide a flow path for fluid from both the first and second sets of pistons. In the second configuration, the flow path for fluid from the second set of pistons may be different from the flow path for fluid from the second set of pistons in the first configuration. Thus, altering the flow of fluid from one set of pistons may include altering the flow path that the fluid follows after leaving the pistons of that set.

[0019] When a valve is configured to control fluid flow from the first and second sets of pistons, the valve can switch the pump between a first configuration in which fluid from the second set of pistons flows along a first flow path, and a second configuration in which fluid from the second set of pistons flows along a second, different flow path. Fluid from the first set of pistons may flow along the same flow path (e.g., a third flow path) in both the first and second configurations.

[0020] Providing a valve configured to control fluid flow from the piston (rather than to the piston) can facilitate an increased number of operating modes of the pump and / or allow the pump to provide high pressure fluid for auxiliary functions. For example, high pressure fluid not required for the hydraulic system to which the pump is connected may be diverted to a cooling circuit to cool the pump and / or to other elements of the hydraulic system.

[0021] The valve may be configured to switch the pump between the first and / or second configurations and a third configuration in which fluid from the first set of pistons flows along a different flow path (e.g., a fourth flow path) than the flow paths of the first and second configurations. In the third configuration, fluid from the second set of pistons may flow along the second flow path.

[0022] The valve may be configured to switch the pump between the first, second, and / or third configurations and a fourth configuration in which fluid from the first set of pistons flows along a different flow path (e.g., a fourth flow path) than the flow paths of the first and second configurations. In the fourth configuration, fluid from the second set of pistons may flow along the first flow path.

[0023] The valves may be configured to switch the pump between the first, second, third and / or fourth configurations and a fifth configuration in which fluid from the first set of pistons flows along both the third and fourth flow paths and / or fluid from the second set of pistons flows along both the first and second flow paths.

[0024] The second and third flow paths may be outlet flow paths through which fluid is discharged from the pump. Each outlet flow path may be connected to a pump outlet suitable for connection to a hydraulic system such that, in use, the pump supplies high pressure fluid to the hydraulic system.

[0025] The first and fourth flow paths may be bypass flow paths through which fluid is returned to (i) a point located upstream of the first and / or second sets of pistons and / or (ii) a reservoir of low pressure fluid (or a pump outlet suitable for connection to such a reservoir).

[0026] It will be appreciated that the valves configured to control fluid flow to the first and second sets of pistons are disposed upstream of the first and second sets of pistons. Similarly, the valves configured to control fluid flow from the first and second sets of pistons are disposed downstream of the first and second sets of pistons. The valves can be spool valves. The spool valves can include a spool mounted for movement relative to a surface that includes a plurality of internal ports. The pump can be configured such that relative movement of the spool and the internal ports controls fluid flow to or from the first and second sets of pistons.

[0027] The spool may be mounted for movement between a first position and a second position. Movement of the spool from the first position to the second position may switch the pump from the first configuration to the second configuration. The spool may be mounted for movement between the first and / or second position and a third position. Movement of the spool from the first and / or second position to the third position may switch the pump from the first and / or second configuration to the third configuration. The spool may be mounted for movement between the first, second and / or third position and a fourth and / or fifth position. Movement of the spool from the first, second and / or third position to the fourth and / or fifth position may switch the pump from the first, second and / or third position to the fourth and / or fifth configuration.

[0028] The spool may be mounted for rotational movement between first, second, third (if present), fourth (if present), and fifth (if present) positions. Rotary spool valves may allow for a more compact pump for a given flow rate and / or facilitate a more compact pump through better packing of the flow galleries within the pump.

[0029] The spool may be mounted for axial movement between first, second, third (if present), fourth (if present), and fifth (if present) positions. In some cases, for example where complex flow connections are not required, a linear spool valve or the like may be advantageous.

[0030] The spool may include a surface having one or more grooves formed therein. Fluid may flow through the servo valve to or from the pistons via one or more grooves. Fluid may flow to or from a first set of pistons via a first groove. Fluid may flow to or from a second set of pistons via a second groove. It will be appreciated that if a groove is aligned with two ports, fluid may flow between the two ports via the groove. Thus, the spool valve may modify fluid flow to or from the pistons by aligning and / or moving one or more grooves out of alignment with the ports. It will be appreciated that by arranging the geometry of the grooves and ports, independent control of different sets of pistons may be achieved.

[0031] The spool may be disposed within a cavity defined at least in part by a surface including a plurality of internal ports, and the spool and cavity may be disposed within the cavity such that a gap between the spool and the surface defining the cavity is small enough to prevent any significant fluid flow between a surface of the spool and a surface of the cavity other than through the one or more grooves.

[0032] When the spool is in the first position, the first groove may be aligned with two ports, and when the spool is in the second position, the first groove may be aligned with the same two ports. When the spool is in the second position, the second groove may be aligned with two ports, and when the spool is in the first position, the second groove may not be aligned with the same two ports. When the spool is in the third position, the first groove may be aligned with a different pair of ports than it is aligned with when the spool is in the first and second positions. Similarly, the first and / or second grooves may be aligned with a different combination of ports in the fourth and / or fifth positions.

[0033] An inlet port may be defined as a port through which fluid enters the groove, and an outlet port may be defined as a port through which fluid exits the groove.

[0034] The plurality of internal ports may include piston ports, each piston port being associated with (i.e., in fluid communication with) either a (chamber of) a first set of pistons or a (chamber of) a second set of pistons. The piston ports associated with the first and second sets of pistons may be referred to as first and second piston ports, respectively. If the valve controls fluid flow to the first and second sets of pistons, the piston port is an outlet port. If the valve controls fluid flow from the first and second sets of pistons, the piston port is an inlet port.

[0035] The plurality of internal ports may include a supply port. In use, each supply port may be connected to a source of (low pressure) fluid, for example a reservoir of low pressure fluid. Thus, a supply port may be an inlet port.

[0036] The plurality of internal ports may include bypass ports, each of which may be connected to a point upstream of the first and / or second sets of pistons and / or to a reservoir of low pressure fluid. The provision of such bypass ports allows a supply of high pressure fluid to be recirculated within the pump, thereby allowing cooling of the pump and / or rotation of the motor shaft without substantial fluid resistance.

[0037] The plurality of internal ports may include an exhaust port. Each exhaust port may be connected to a pump outlet. Thus, the exhaust ports may be outlet ports.

[0038] If the valve controls fluid flow to the first and second sets of pistons, in the first and second positions, the first groove may be aligned with the supply port and the first piston port. In the second position, the second groove may be aligned with the supply port and the second piston port. In the first position, the second groove may be misaligned with one or both of the supply port and the second piston port. In the third position, the second groove may be aligned with the supply port and the second piston port. In the third position, the first groove may be misaligned with one or both of the supply port and the first piston port.

[0039] Where the valve controls fluid flow from the first and second sets of pistons, each piston port may be connected to an associated set of pistons such that, in use, fluid may flow from the set of pistons through the piston port to the spool. In the first and second positions, the first groove may be aligned with the first piston port and the outlet port. In the first position, the second groove may be aligned with the second piston port and one of the bypass port and the exhaust port. In the second position, the second groove may be aligned with the second piston port and the other of the bypass port and the exhaust port. In the third position, the first groove may be aligned with the first piston port and the bypass port. In the third position, the second groove may be aligned with the second piston port and one of the bypass port and the exhaust port. In the fourth position, the second groove may be aligned with the second piston port and the other of the bypass port and the exhaust port. Thus, the valve may be configured to switch the pump to a fourth configuration. In the fifth position, the first groove can be aligned with the first piston port, the bypass port, and the exhaust port. In the fifth position, the second groove can be aligned with the second piston port, the bypass port, and the exhaust port.

[0040] At least a portion of the rotor may overlap a portion of the valve, e.g., a spool. For example, the valve, e.g., a spool, and the rotor may be concentric. At least a portion of the valve, e.g., a spool, may be located inside a portion of the rotor. The rotor may have a longitudinal axis (axis of rotation) about which the rotor rotates. The spool may have a longitudinal axis along or about which the spool moves. The longitudinal axes of the rotor and the spool may be parallel. The spool and the rotor may be coaxial (i.e., the spool and the rotor have a common longitudinal axis).

[0041] Providing a valve in the rotor to control flow to the piston may allow for a more compact pump for a given flow rate. Additionally or alternatively, providing a valve in the rotor may reduce the length and / or complexity of the flow paths in the pump, thereby reducing associated pressure losses and improving efficiency.

[0042] The pump may include a pintle. Further features of the pintle are described below in relation to aspect X. The rotor may be mounted to rotate on the pintle. A portion of the valve, e.g., the spool, and the pintle may be concentric. At least a portion of the valve, e.g., the spool, may be located inside a portion of the pintle. The pintle may have a longitudinal axis (axis of rotation) about which the rotor rotates. The longitudinal axes of the rotor, pintle, and / or spool may be parallel. The spool, rotor, and / or pintle may be coaxial (i.e., the spool and rotor have a common longitudinal axis).

[0043] A surface, e.g., an inner surface, of the pintle may include a plurality of internal ports. The surface of the pintle may at least partially define a cavity within the pintle, and at least a portion of the valve, e.g., a spool, may be received within said cavity. The spool may thus be disposed within a cavity formed in the pintle over which the rotor rotates. The spool may be mounted for movement relative to the pintle.

[0044] By locating the valve within the pintle to which the rotor is attached, a more compact pump can be provided for a given flow rate. Additionally or alternatively, by providing the valve within the pintle, the pintle can form a manifold for the valves, thereby reducing the number of elements within the pump and / or allowing for a more compact pump for a given flow rate.

[0045] The radial piston pump may include a control motor configured to move a valve, e.g., a spool, between first, second, third (if present), fourth (if present), and / or fifth (if present) positions.

[0046] The pintle may include one or more flow galleries through which fluid can flow. Each flow gallery may be connected to one or more internal ports of the spool valve. For example, the pintle may include a piston flow gallery, where each piston flow gallery connects a piston (or piston chamber) of the first or second set of pistons to a piston port. The pintle may include an exhaust flow gallery connecting an exhaust port to one or more outlets for connecting the pump to a hydraulic system. The pintle may include a bypass flow gallery connecting a bypass port to a point upstream of the first and / or second set of pistons or to a reservoir of low pressure fluid.

[0047] The first and / or second cam surfaces may be shaped such that each piston of the first and / or second sets, respectively, completes two, four, six, or more reciprocating motions (each reciprocating motion including a motion in a first direction and a motion in an opposite second direction) for each full rotation of the rotor. The first and / or second cam surfaces may be shaped such that each piston completes only two, four, or six reciprocating motions for each full rotation of the rotor.

[0048] The radial distance between the longitudinal axis of the rotor and the cam surface may vary circumferentially (e.g., around the circumference of the rotor and / or cam surface). The first and / or second cam surfaces may each include one or more regions of decreasing radius (e.g., regions of decreasing radius corresponding to movement of the piston in a first direction) and one or more regions of increasing radius (e.g., regions of decreasing radius corresponding to movement of the piston in an opposite second direction). Each region of decreasing radius may be located between two regions of increasing radius, or vice versa. Each region of decreasing radius may be located opposite another region of decreasing radius. Each region of increasing radius may be located opposite another region of increasing radius.

[0049] The profile of the cam surface may be defined as the change in radius of the cam surface around the circumference of the cam surface and / or rotor. The radius of the cam surface may be defined as the distance between the cam surface and the point about which the rotor rotates relative to the cam surface.

[0050] The cam surface profile may include one or more cycles, with each cycle including regions of increasing radius and regions of decreasing radius. Thus, each cycle of the cam surface may correspond to a cycle (a complete back and forth movement) of the piston. The cam surface profile may include 2, 4, 6, or more cycles. The cam surface profile may include only 2, 4, or 6 cycles.

[0051] Each cam surface may have a surface facing the longitudinal axis (axis of rotation) of the rotor. Each cam surface may extend circumferentially around the rotor, for example around the entire circumference of the rotor. Each cam surface may extend 360 degrees around the rotor.

[0052] The radial piston pump may include a plurality of cam followers arranged to move along the first or second cam surfaces as the rotor rotates relative to the first and second cam surfaces, with each piston connected to a cam follower such that radial displacement of the cam follower results in radial displacement of the piston. The radial piston pump may include a first set of cam followers arranged to move along (follow) the first cam surface and a second set of cam followers arranged to move along (follow) the second cam surface. The first set of pistons may be connected to the first set of cam followers. The second set of pistons may be connected to the second set of cam followers.

[0053] The first set of piston chambers and / or pistons may be spaced apart from the second set of piston chambers and / or pistons along a longitudinal axis (axis of rotation) of the rotor. The first cam surface may be spaced apart from the second cam surface along the longitudinal axis of the rotor. The position of each cam surface may be fixed relative to the housing of the pump. The first set of pistons may be disposed at substantially the same location along the longitudinal axis of the rotor. The second set of pistons may be disposed at substantially the same location along the longitudinal axis of the rotor.

[0054] The radial piston pump may be an internal impingement piston pump. The radial piston pump, e.g., the rotor and / or pintle, may comprise, consist essentially of, or consist of a metal, e.g., steel, aluminum, bronze, titanium, or other suitable material.

[0055] The pump (or the system it forms a part of) may include a control system configured to control the operation of the pump, e.g., the speed of the motor and / or the valve. The control system may be configured to control the control motor (which moves the valve) and / or the motor which rotates the rotor in response to user input and / or signals received from a feedback system. The pump may comprise a feedback system, e.g., an electrical feedback system, configured to provide information regarding the state of the valve, e.g., the position of the spool and / or the speed of the rotor. The feedback system may comprise one or more sensors, e.g., electrical transducers, attached to the spool and / or the rotor.

[0056] The pump may include additional sets of pistons. The valves may be configured to control the flow to or from each set of pistons. The valves may be configured to control the fluid flow of each of the additional sets of pistons independently of the first and / or second sets of pistons. Alternatively, the pump may include a first group of pistons including the first set of pistons and one or more additional sets of pistons, and a second group of pistons including the second set of pistons and one or more additional sets of pistons. The valves may be configured to switch the radial piston pump from the first configuration to the second configuration by modifying the fluid flow to or from the second group of pistons independently of the first group of pistons.

[0057] In a second aspect of the invention, there is provided a radial piston pump comprising one or more rotors having a plurality of piston chambers, a first set of pistons and a second set of pistons received within the piston chambers, and a first cam surface and a second cam surface. The rotor may be mounted for rotation relative to the first cam surface and the second cam surface. The first cam surface may be configured to control radial movement of the first set of pistons and the second cam surface may be configured to control radial movement of the second set of pistons. The pump may comprise a valve configured to control fluid flow to or from the first and second sets of pistons, the valve being concentric with the rotor.

[0058] By using the same, concentrically mounted valve to control flow to or from both sets of pistons, a more compact pump can be provided for a given flow rate and / or a mechanically simpler pump can be provided.

[0059] The pump of the second aspect may have any of the features described above in relation to the first aspect, for example the valve may be a spool valve as described above and / or the rotor may be mounted on a pintle as described above.

[0060] In a third aspect of the present invention, there is provided a radial piston pump comprising one or more of: a motor comprising a plurality of magnets, a plurality of coils and a stator; a rotor mounted for rotation relative to the stator and having a plurality of piston chambers and a plurality of pistons received within said piston chambers. Either the plurality of magnets or the plurality of coils may be mounted to the stator, and the other of the plurality of magnets and the plurality of coils may be mounted to the rotor.

[0061] Thus, a radial piston pump according to the invention may include a common rotor between the pump and the motor, the use of such a common rotor may make the pump more compact for a given flow rate and / or reduce the mechanical complexity of the pump relative to similar prior art pumps.

[0062] A plurality of magnets or a plurality of coils are attached to the rotor for rotation therewith, such that when a current is supplied to the coils in the presence of the magnetic field of the magnets, an electromotive force is generated, thereby rotating the rotor. Electric motors are known per se and will not be described further herein.

[0063] The rotor may be mounted to the pintle for rotation relative to the stator. The pump may be configured such that a hydrostatic bearing is formed between the pintle and the rotor, said hydrostatic bearing containing (high pressure) fluid from the piston chamber.

[0064] By reducing friction between the rotor and pintle, hydrostatic bearings may provide a more efficient pump and / or extend the life of the pump by reducing wear on the pintle and / or rotor. The use of hydrostatic bearings may be particularly advantageous in pumps having first and second sets of pistons because it allows for more compact packaging, less noise and / or higher speeds.

[0065] The pintle and rotor may each comprise one or more bearing surfaces through which loads from the rotor are transferred to the pintle. The pintle bearing surface may be an outer surface of the pintle, e.g., a surface facing away from the longitudinal axis of the pintle and / or rotor. The rotor bearing surface may be an inner surface of the rotor, e.g., a surface facing the longitudinal axis of the pintle and / or rotor. The hydrostatic bearing may comprise a fluid layer located between the pintle bearing surface and the rotor bearing surface. The fluid layer may include a fluid pressurized by passing through a piston chamber of the pump. Thus, the fluid layer may be a high pressure fluid.

[0066] The bearing surface of the pintle and / or the bearing surface may comprise one or more orifices configured to supply fluid to the hydrostatic bearing. The one or more orifices may be in fluid communication with one or more of the piston chambers. The bearing surface may comprise a first orifice or set of orifices in fluid communication with the piston chambers of the first set of pistons. The bearing surface may comprise a second orifice or set of orifices in fluid communication with the piston chambers of the second set of pistons. The pintle and / or the rotor may comprise one or more flow galleries forming part of a flow path between the one or more orifices and the piston chambers.

[0067] The radial piston pump may comprise a housing, and the rotor and / or the stator may be disposed (at least partially) within the housing.

[0068] The housing may include one or more partitions configured to provide a first compartment in which the rotor is disposed and a second compartment in which the stator is disposed. The partitions may be configured to prevent fluid from the rotor from contacting the stator. Thus, the first compartment may be a watertight compartment.

[0069] By separating the "wet" components (e.g., rotor and piston) from the electronics (e.g., coil using an internal wall), a more reliable and / or robust pump can be provided.

[0070] The radial piston pump may include one or more cooling flow galleries configured to provide a fluid flow path around one or more components of the pump, e.g., around the motor and / or rotor of the pump, such that fluid in said cooling flow galleries can absorb excess heat from said components. The cooling flow gallery(s) may be in fluid communication with the first compartment, e.g., to receive fluid leaking from the piston chamber to the exterior of the rotor and / or into the first compartment. Fluid leaking from the piston chamber may thus be used to cool the pump.

[0071] By using the high pressure fluid leaking from the piston chamber to cool the pump, cooling of the pump can be achieved with a significant impact on the efficiency of the pump, as there is no need to pressurize the fluid for the express purpose of cooling the pump, and instead hydraulic power that might otherwise be wasted is put to a useful purpose.

[0072] Alternatively, the cooling flow gallery may form part of a bypass flow path, for example, the cooling flow gallery may be a bypass flow gallery and / or may be connected to a bypass port such that high pressure fluid that is not output from the pump may be recirculated to cool the pump, thereby cooling the pump with minimal impact on efficiency.

[0073] In a fourth aspect of the invention, there is provided a radial piston pump comprising a rotor mounted for rotation on a pintle, the rotor comprising a plurality of piston chambers, with pistons mounted for reciprocating movement in each of said chambers. The pump comprises at least one supply flow path connecting one or more of the piston chambers to a source of low pressure fluid in use; at least one outlet flow path through which high pressure fluid from one or more of the piston chambers is discharged from the pump in use; and at least one auxiliary flow path connecting another component of the pump to one or more of the piston chambers. The pintle comprises a plurality of flow galleries, the plurality of flow galleries may comprise one or more of at least one supply flow gallery forming part of the supply flow path, at least one outlet flow gallery forming part of the outlet flow path, and at least one auxiliary flow gallery forming part of the auxiliary flow path.

[0074] Thus, a radial piston pump according to the present invention may use a pintle as a fluid manifold that supplies fluid to or from the piston and to or from at least one other component of the pump. Having such a multi-function pintle may allow the pump to be more compact for a given flow rate and / or reduce the number of components in the pump. Additionally or alternatively, using the pintle as a fluid manifold for another component of the pump may reduce the distance that fluid travels in the pump and the associated pressure losses.

[0075] The pump may be configured such that, in use, high pressure fluid from one or more of the piston chambers is supplied to said further component via the auxiliary flow path.

[0076] The pump may comprise a return flow path connected to an outlet of said further component of the pump. The pump may be configured such that, in use, (low pressure) fluid is exhausted from said further component and / or the pump via the return flow path. The pintle may comprise at least one return flow gallery forming part of the return flow path.

[0077] Multiple flow galleries, such as at least one supply flow gallery, at least one outlet flow gallery, at least one auxiliary flow gallery, and / or at least one return flow gallery (if present), may be at the same axial location on the pintle (i.e., at the same location along the longitudinal axis of the pintle). The at least one outlet flow gallery, at least one auxiliary flow gallery, and / or at least one return flow gallery (if present) may be circumferentially spaced about the pintle.

[0078] The multiple flow galleries may be integrally formed with the pintle, i.e., the multiple flow galleries may be formed within the pintle as a single piece, for example, using an additive manufacturing process.

[0079] The auxiliary flow path may connect the piston and the control valve (i.e., the further component may be a control valve). The control valve may comprise a pressure inlet, a return outlet, and a first and / or second service outlet. For example, the control valve may be a three-way valve with a pressure inlet, a return outlet, and a first service outlet. Alternatively, the control valve may be a four-way valve with a pressure inlet, a return outlet, a first service outlet, and a second service outlet. The auxiliary flow path may connect the pressure inlet to one or more piston chambers. For example, in use, high pressure fluid from the piston chambers may be supplied to the pressure inlet of the control valve via the auxiliary flow path. The return flow path may be connected to the return outlet of the control valve, such that in use, fluid from the control valve flows via the return flow path to a (low pressure) reservoir and / or an outlet of the pump suitable for connection to such a reservoir. The pump may comprise one or more first and / or second service flow paths through which the first and second service flows from the control valve (respectively) may be discharged from the pump in use. The pump may comprise one or more service ports suitable for connection to an actuator or other hydraulic component, for example an actuator for providing or controlling linear motion or force, or a rotary actuator functioning as a pump or motor controlled as a component of a transmission. The pump may comprise one or more first and / or second service ports through which a first or second service flow path is connected to the actuator or other hydraulic component. Thus, in use, first and / or second service flows from the control valve may be provided to a hydraulic component connected to the pump via the first and / or second service ports.

[0080] The plurality of flow galleries may further comprise at least one first and / or second service flow gallery forming part of a first or second service flow path, respectively.

[0081] The pump may comprise a first set of flow paths including an auxiliary flow path, a return flow path and a first and / or second service flow path, and a second set of flow paths including an auxiliary flow path, a return flow path and a first and / or second service flow path, the first set of flow paths being connected to a first component and the second set of flow paths being connected to a second, different component. The pintle may comprise a first set of flow galleries, each of which forms part of one of the flow paths of the first and second sets of flow galleries, and each of which forms part of one of the flow paths of the second set. The pump may comprise further components and further sets of flow paths associated with each component. The pintle may comprise a further set of flow galleries, each of which forms part of one of the flow paths of the further sets.

[0082] The control valve may be a servo valve. The servo valve may comprise a spool mounted for movement relative to a sleeve comprising a plurality of internal ports. The servo valve may be configured such that movement of the spool relative to the sleeve controls flow through the valve, for example, by varying fluid flow through grooves formed in a surface of the spool. The function of the servo valve may be as described in relation to the spool valve above. In the case of a three-way servo valve, the valve is configured to determine, by movement of the spool, whether the auxiliary flow path and the return flow path are in fluid communication with the first service flow path. In the case of a four-way servo valve, the valve is configured to determine, by movement of the spool, whether the auxiliary flow path and the return flow path are in fluid communication with the first service flow path and whether the auxiliary flow path and the return flow path are in fluid communication with the second service flow path. The control valve may comprise a control valve motor configured to move the spool.

[0083] It will be appreciated that the pump may include a spool valve (as described above) configured to control flow to or from the piston chambers, and a control valve configured to receive high pressure fluid from the piston chambers. The pintle may be as described above in relation to the first embodiment. For example, the pintle may be configured to receive at least a portion of a valve configured to control fluid flow to or from both the first set of pistons and the second set of pistons.

[0084] The pintle may further comprise one or more sensors and / or sensor targets. The pump may comprise a feedback system configured to detect the rotational position of the rotor using said sensors and / or to calculate the speed and / or acceleration of the pump in response to the rotational position so detected.

[0085] The pintle may include one or more recesses extending along at least a portion, e.g., the entire length, of the pintle. The or each recess may be configured to receive (or include at least a portion of) a rod of an elongated member, e.g., a piston. The pintle may include an anti-rotation device configured to prevent rotation of the elongated member relative to the pintle. The anti-rotation device may include an interlocking feature (e.g., a protrusion or a recess) configured to be received in a corresponding interlocking feature (e.g., the other of the protrusion or recess) on the elongated member, such that, in use, when the two interlocking features are engaged, rotation of the elongated member relative to the protrusion is prevented.

[0086] In a fifth aspect of the present invention there is provided a hydraulic power pack comprising a radial piston pump according to any other aspect, such as any of the first to fourth aspects.

[0087] The hydraulic power pack may be configured to supply high pressure fluid to the hydraulic system. The hydraulic power pack may include a reservoir configured to store a supply of low pressure fluid. The fluid reservoir is connected to an inlet of the pump and / or a supply flow path of the pump such that low pressure fluid from the fluid reservoir is supplied to the pump. The hydraulic power pack may include an accumulator configured to store a supply of high pressure fluid for use in the hydraulic system. The accumulator is connected to an outlet of the pump and / or an outlet flow path of the pump such that high pressure fluid from the pump is supplied to the accumulator.

[0088] The hydraulic power pack may include a fluid reservoir piston that at least partially defines a fluid reservoir. The hydraulic power pack may include an accumulator piston that at least partially defines an accumulator. The fluid reservoir piston and / or the accumulator piston may be mounted on the pintle for movement (e.g., axial movement) relative to the pintle and / or each other. At least a portion of the fluid reservoir piston and / or the accumulator piston may be received within a piston recess formed in and extending along a portion of the pintle, e.g., a majority of the length. The piston recess may comprise a through hole in the pintle in which the rotor is mounted. The fluid reservoir piston and / or the accumulator piston may be received within the same piston recess.

[0089] The fluid reservoir piston, the accumulator piston may be coaxial, and the pintle and / or the rotor may also be coaxial. The fluid reservoir piston, the accumulator piston, the pintle and / or the rotor may be concentric. A portion of one of the fluid reservoir piston and the accumulator piston may be received within a piston recess formed in the other of the fluid reservoir piston and the accumulator piston.

[0090] The fluid reservoir piston and / or the accumulator piston may each include a piston head and a piston stem extending from the piston head. The piston may at least partially define the fluid reservoir or accumulator. The fluid reservoir piston and / or the accumulator piston may each include one or more flow galleries. The fluid reservoir piston may include one or more flow galleries connecting the fluid reservoir to an inlet of the pump and / or a supply flow path of the pump. The accumulator may include one or more flow galleries connecting an outlet of the pump and / or an outlet flow path to the accumulator.

[0091] The hydraulic power pack can be configured such that force generated by high pressure fluid in the accumulator is transferred to the low pressure fluid in the reservoir via a fluid reservoir piston. For example, a portion of the fluid reservoir piston, e.g., a distal end of a piston stem, can at least partially define the accumulator. Thus, the portion of the fluid reservoir piston can be exposed to the high pressure fluid in the accumulator.

[0092] The hydraulic power pack may include a power pack housing. The radial piston pump may be disposed within the power pack housing. The power pack housing may include one or more internal walls dividing the power pack into a first compartment in which the rotor is disposed and a second compartment in which a stator of the motor is disposed. The internal walls may be configured to provide a watertight barrier between the first compartment and the second compartment, thereby preventing fluid from the first compartment from contacting the stator.

[0093] In a sixth aspect of the present invention there is provided a braking system for a vehicle, such as an automobile, comprising a radial piston pump and / or a hydraulic power pack according to any other aspect.

[0094] The braking system may comprise brake pads and an actuator configured to move the brake pads from a first position to a second position to effect braking of the wheels of the vehicle. The braking system may comprise a fluid reservoir for storing low pressure fluid. The braking system may be configured such that, in use, low pressure fluid from the reservoir is supplied to the pump and / or high pressure fluid from the pump is supplied to the actuator (e.g., via an accumulator or directly to the actuator). The braking system may comprise a valve configured to control fluid flow from both the first set of pistons and the second set of pistons, as described above in relation to the first aspect.

[0095] In a seventh aspect of the present invention there is provided an active suspension system for a vehicle, such as an automobile, comprising a radial piston pump and / or a hydraulic power pack according to any other aspect.

[0096] An "active" suspension system for a vehicle can be defined as a system that supplies energy to actuators to control the relative motion of the vehicle's wheels and chassis in response to road conditions. This is in contrast to an active damping system (also known as semi-active or adaptive suspension) in which the stiffness of the suspension means (e.g. the stiffness of a damper placed in parallel with the coil springs of a vehicle suspension) varies in response to road conditions.

[0097] An active suspension system may comprise an actuator configured to exert a force on the wheels and / or chassis of a vehicle. Typically, in immediate response to a road event (e.g., cornering, accelerating or braking), a control system switches on a pump, which supplies fluid under pressure to the actuator to move an actuator arm, thereby exerting a reaction force on the chassis and wheels. Typically, the power of the pump is provided by the engine of the vehicle. The main challenge of an active suspension system is to instantly provide the high power required when the vehicle encounters a more severe road event, such as a speed bump, without adversely affecting the driving experience (e.g., by drawing an excessive amount of power from the engine) and / or without requiring large valves / pumps. The radial piston pump of the present invention is particularly suitable for this application because it allows for rapid changes in flow rate to the actuator.

[0098] The active suspension system may comprise a damper, e.g., a spring, configured to exert a force on the wheel and / or the chassis. The damper and the actuator may be arranged in parallel. The active suspension system may comprise a fluid reservoir for storing low pressure fluid. The active suspension system may be configured such that, in use, low pressure fluid from the reservoir is supplied to the pump and / or high pressure fluid from the pump is supplied to the actuator (e.g., via an accumulator or directly to the actuator). The active suspension system may comprise a valve configured to control fluid flow from both the first set of pistons and the second set of pistons, as described above in relation to the first aspect.

[0099] In an eighth aspect of the present invention there is provided a flight control system for an aircraft, such as a fixed-wing aircraft, the flight control system comprising a radial piston pump and / or a hydraulic power pack according to any other aspect.

[0100] The flight control system may comprise a control surface and an actuator configured to move the control surface (e.g., a flap, slat, or other control surface) from a first position to a second position to effect a change in the aerodynamic performance of the control surface. The flight control system may comprise a fluid reservoir for storing low pressure fluid. The flight control system may be configured such that, in use, low pressure fluid from the reservoir is supplied to a pump and high pressure fluid from the pump is supplied to the actuator (e.g., via an accumulator or directly). The flight control system may comprise a valve configured to control fluid flow from both the first set of pistons and the second set of pistons, as described above in relation to the first aspect.

[0101] A valve (e.g., of a braking system, active suspension system, and / or flight control system) can be configured to switch the pump between a first configuration in which fluid from a second set of pistons flows along a first flow path, and a second configuration in which fluid from the second set of pistons flows along a second, different flow path, and in both the first and second configurations, fluid from the first set of pistons flows along the same flow path (e.g., a third flow path). The valve can be configured to switch the pump between the first and / or second configurations and a third configuration in which fluid from the first set of pistons flows along a different flow path (e.g., a fourth flow path) than the first and second configurations. In the third configuration, fluid from the second set of pistons can flow along the second flow path.

[0102] A valve (e.g., in a braking system, an active suspension system, and / or a flight control system) may be configured to switch the pump between a first, second, and / or third configuration and a fourth configuration in which fluid from the first set of pistons flows along a different flow path (e.g., a fourth flow path) than the flow paths of the first and second configurations. In the fourth configuration, fluid from the second set of pistons may flow along the first flow path.

[0103] The valve may be a spool valve comprising a spool mounted for movement relative to a series of internal ports, the spool valve configured to switch the pump between the first, second, third, and / or fourth configurations by moving the spool relative to the internal ports (e.g., by rotating the spool or axially moving the spool).

[0104] In the first configuration, the first set of pistons may be in fluid communication with actuators (e.g., actuators of a braking system, an active suspension system, and / or a flight control system), thereby allowing high pressure fluid from the first set of pistons to flow to the actuators. In the first configuration, the second set of pistons may be in fluid communication with upstream points of the first and / or second sets of pistons and / or fluid reservoirs (e.g., fluid reservoirs of a braking system, an active suspension system, and / or a flight control system), thereby allowing high pressure fluid from the second set of pistons to be recirculated between said upstream points and / or said reservoirs and the pistons.

[0105] In the second configuration, the first set of pistons may be in fluid communication with the actuators, thereby allowing high pressure fluid from the first set of pistons to flow to the actuators. In the second configuration, the second set of pistons may be in fluid communication with the actuators, thereby allowing high pressure fluid from the second set of pistons to flow to the actuators.

[0106] In a third configuration, the first set of pistons are in fluid communication with upstream points of the first and / or second sets of pistons and / or fluid reservoirs, such that high pressure fluid from the second set of pistons can be recirculated between said upstream points and / or said reservoirs and pistons. In a third configuration, the second set of pistons are in fluid communication with upstream points of the first and / or second sets of pistons and / or fluid reservoirs, such that high pressure fluid from the second set of pistons can be recirculated between upstream points and / or said reservoirs and pistons.

[0107] In a fourth configuration, the valves are open, allowing fluid from the first set of pistons and the second set of pistons to flow between (i) an upstream point on the first and / or second sets of pistons and / or the fluid reservoir and (ii) the actuator.

[0108] In a ninth aspect of the present invention, there is provided a method of braking a vehicle comprising a braking system according to the sixth aspect of the present invention.

[0109] The method can include the pump switching to a first configuration in response to a signal indicating a lower level of braking is required. In the first configuration, fluid can be supplied by the pump to the actuator at a first, lower flow rate.

[0110] The method can include the pump switching to a second configuration in response to a signal indicating a higher level of braking is required, where in the second configuration fluid can be supplied by the pump to the actuator at a second, higher flow rate.

[0111] The method may include the pump switching to a third configuration in the absence of a signal indicating braking is required and / or in response to a signal indicating braking is not required. In the third configuration, no fluid may be provided by the pump to the actuator. In the third configuration, high pressure fluid from the pump may be recirculated within the pump and / or brake system to cool the pump, brake pads and / or actuators.

[0112] The method can include the pump switching to the fourth configuration in response to a signal indicating that a higher level of braking is required immediately (e.g., within less than one second). Such a signal can be sent by the control system upon detecting one or more conditions indicating that a higher level of braking is required immediately (e.g., the throttle pedal is suddenly released or a vehicle sensor detects an obstacle). In the third configuration, the speed at which the motor drives the pump can be increased, for example, from rest to half or full speed.

[0113] In a tenth aspect of the present invention there is provided a vehicle, for example a car, comprising a braking system according to the sixth aspect.

[0114] In an eleventh aspect of the present invention, there is provided a method of damping movement of a vehicle comprising an active suspension system according to the seventh aspect of the present invention.

[0115] The method can include the pump switching to a first configuration in response to a signal indicating a lower level of damping is required. In the first configuration, fluid can be supplied by the pump to the actuator at a first, lower flow rate.

[0116] The method can include the pump switching to a second configuration in response to a signal indicating a higher level of damping is required, where in the second configuration fluid can be supplied by the pump to the actuator at a second, higher flow rate.

[0117] The method can include the pump switching to a third configuration in the absence of a signal indicating damping is needed and / or a signal indicating damping is not needed. In the third configuration, no fluid can be supplied by the pump to the actuator. In the third configuration, high pressure fluid from the pump can be recirculated within the pump and / or suspension system to cool the pump and / or actuator.

[0118] The method can include the pump switching to the fourth configuration in response to a signal indicating that a higher level of damping is required immediately (e.g., within less than one second). Such a signal can be sent by the control system upon detecting one or more conditions indicating that a higher level of damping is required immediately (e.g., the vehicle's forward looking sensors detect an obstacle such as a speed bump). In the third configuration, the speed at which the motor drives the pump can be increased, for example, from rest to half speed or full speed.

[0119] In a twelfth aspect of the present invention, there is provided a vehicle, for example a car, comprising an active suspension system according to the seventh aspect.

[0120] In a thirteenth aspect of the present invention, there is provided a method of controlling an aircraft including a flight control system according to the eighth aspect of the present invention.

[0121] The method can include, for example, switching the pump to a first configuration in response to a signal indicating that power is required by the actuator to move the flight control surface, where in the first configuration fluid can be supplied by the pump to the actuator at a first, lower flow rate.

[0122] The method can include, for example, the pump switching to a second configuration in response to a signal indicating that the actuator needs more power to move the flight control surface faster, where in the second configuration fluid can be supplied by the pump to the actuator at a second, higher flow rate.

[0123] The method may include the pump switching to a third configuration in the absence of a signal indicating that power is needed by the actuators and / or when a signal indicates that power is not needed. In the third configuration, no fluid may be provided by the pump to the actuators. In the third configuration, high pressure fluid from the pump may be recirculated within the pump and / or the flight control system to cool the pump and / or the actuators.

[0124] The method can include the pump switching to the fourth configuration in response to a signal indicating that a higher level of power is required immediately (e.g., within less than one second). Such a signal can be sent by the control system upon detecting one or more conditions indicating that a higher level of damping is required immediately. In the third configuration, the speed at which the motor drives the pump can be increased, for example, from rest to half speed or full speed.

[0125] In a fourteenth aspect of the present invention, there is provided an aircraft comprising a flight control system according to the eighth aspect.

[0126] In a fifteenth aspect of the present invention, there is provided a pintle suitable for use as the pintle of any of the other aspects.

[0127] In a sixteenth aspect of the present invention there is provided a method of manufacturing a radial piston pump according to any preceding claim, the method comprising manufacturing one or more of the rotor, the pintle and / or the spool using an additive manufacturing process.

[0128] The method may include finishing the rotor, pintle, and / or spool manufactured using an additive manufacturing process using a subtractive manufacturing process, for example, one or more of grinding, milling, boring, and / or polishing.

[0129] The method may further include assembling one or more of the stator, rotor, pintle and / or spool to produce a radial piston pump according to any preceding aspect.

[0130] In a seventeenth aspect of the present invention, there is provided a method of operating a radial piston pump according to any other aspect (or a hydraulic power pack or brake system including such a pump).

[0131] A method may be provided for controlling operation of a radial piston pump comprising one or more of a rotor having a plurality of piston chambers, a first set of pistons and a second set of pistons received within the piston chambers, a first cam surface arranged to control radial movement of the first set of pistons and a second cam surface arranged to control radial movement of the second set of pistons. The method may include a valve controlling fluid flow to or from both the first set of pistons and the second set of pistons. The method may include a valve altering fluid flow to (or from) the second set of pistons without altering fluid flow to (or from) the first set of pistons, thereby switching the radial piston pump from a first configuration to a second configuration.

[0132] The method may further include a valve that alters fluid flow to or from the first set of pistons without altering fluid flow to the second set of pistons, thereby switching the radial piston pump from the first configuration to a third configuration.The method may further include a valve that simultaneously alters fluid flow to or from the first set of pistons and the second set of pistons, thereby switching the radial piston pump from the first configuration to a fourth configuration.

[0133] The method may include, for example, a valve switching the radial piston pump from one configuration to another (e.g., from a first configuration to a second configuration) in response to a signal (a control signal) from a user and / or a control system configured to operate a hydraulic system to which the pump is connected.

[0134] The method may include a valve switching (ie, varying the flow) of the pump while the rotor is spinning.

[0135] The method may include increasing a flow rate of high-pressure fluid output from the pump (e.g., from a first flow rate to a second, higher flow rate) by a valve that switches the pump from a first configuration to a second configuration.

[0136] The method may include cooling the pump by operating the pump in a third configuration and / or enhancing cooling of the pump by a valve that switches the pump from the first and / or second configurations to the third configuration.

[0137] The method may include operating the pump in a fourth configuration in which the valve is open, thereby allowing fluid from both the first set of pistons and the second set of pistons to flow to (i) a point upstream of the first and / or second sets of pistons and (ii) an outlet of the pump. The method may include increasing the speed of the pump, e.g., a motor, while the pump is in the further configuration. The method may include the valve switching the pump from the fourth configuration to the first and / or second configuration in response to a control signal or when the speed of the pump reaches a predetermined threshold.

[0138] A method of operating a radial piston pump comprising a rotor mounted for rotation on a pintle may be provided. The rotor may comprise a plurality of piston chambers, with pistons mounted for reciprocating movement in each of said chambers. Fluid flows from a source of low pressure fluid along at least one supply passageway to one or more of the piston chambers, and high pressure fluid from one or more of the piston chambers may be exhausted from the pump via at least one exhaust passageway and / or high pressure fluid from one or more of the piston chambers may flow via at least one auxiliary passageway to another component of the pump for use in the operation of the component. Fluid on the at least one supply passageway, the at least one exhaust passageway and / or the at least one auxiliary passageway may flow through one or more flow galleries in the pintle.

[0139] It will of course be understood that features described in relation to one aspect of the invention may be incorporated in other aspects of the invention, for example a method of the invention may incorporate any of the features described in relation to an apparatus of the invention, and vice versa.

[0140] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which: [Brief description of the drawings]

[0141] [Figure 1] FIG. 1 is a cross-sectional view of a radial piston pump in the prior art. [Diagram 2] 1 is a perspective cross-sectional view of a radial piston pump and motor assembly according to a first embodiment of the present invention; FIG. [Figure 3a] FIG. 3 is a perspective cross-sectional view of the radial piston pump of FIG. 2. [Figure 3b] FIG. 3 is a perspective cross-sectional view of the radial piston pump of FIG. 2. [Figure 4] FIG. 3 is a perspective view of a pintle of the radial piston pump of FIG. 2. [Figure 5a] FIG. 6 is a cross-sectional view of the pintle of FIG. [Figure 5b] FIG. 6 is a cross-sectional view of the pintle of FIG. [Figure 6a] FIG. 6 is a cross-sectional view of the pintle of FIG. [Figure 6b] FIG. 6 is a cross-sectional view of the pintle of FIG. [Figure 7] FIG. 3 is a perspective view of a spool of the radial piston pump of FIG. 2. [Figure 8] FIG. 3 is a perspective view of a rotor of the radial piston pump of FIG. 2. [Figure 9] 1 is a schematic diagram of a braking system including a radial piston pump according to an embodiment of the present invention; [Figure 10a] FIG. 2 is a cross-sectional view of a power pack according to one embodiment of the present invention. [Figure 10b] FIG. 2 is a cross-sectional view of a power pack according to one embodiment of the present invention. [Figure 11] FIG. 11 is a cross-sectional view of a pintle of the power pack of FIG. [Figure 12] FIG. 1 is a schematic diagram of an active suspension system including a radial piston pump in accordance with an exemplary embodiment of the present invention. [Figure 13] FIG. 1 is a schematic diagram of a flight control system including a radial piston pump in accordance with an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0142] 2 and 3 are cross-sectional views of a radial piston pump and motor assembly 1. Both Figs. 3a and 3b are cross-sectional plan views of the radial piston pump and motor assembly 1 of Fig. 2. The assembly 1 comprises a rotor 2 (shown in detail in Fig. 9) mounted on a pintle 4 (shown partially transparent in Fig. 2 to aid in understanding). A spool 6 (shown in detail in Fig. 6) is concentrically disposed within a cavity 8 defined by an inner surface 10 of the pintle 4. In this embodiment, the spool 6 is an elongated body having a generally circular cross-section, although the surface of the spool is flattened in some areas to provide an uneven surface 7. In other embodiments, the spool may comprise one or more lands or grooves. One end 59 of the spool 6 protrudes from the pintle 4 and is connected to a control motor 12. 2, the control motor 12 includes a plurality of control motor permanent magnets 14 mounted on the splines 56 of the spool 6 for rotation therewith, and a plurality of control motor coils 16, the control motor permanent magnets 14 being concentrically arranged within the control motor coils 16. While this embodiment has the permanent magnets concentrically arranged within the annular array of coils, it will be appreciated that other control motor configurations could be used, such as coils mounted on the rotor and permanent magnets mounted on the pump housing.

[0143] The rotor 2 includes a number of radially extending piston chambers 18, and in use, each cavity has a piston 20 disposed therein. The pistons 20 (and piston chambers 18) are arranged in two layers, with the pistons 20a in the first layer spaced apart from the pistons 20b in the second layer along the longitudinal axis of the rotor 2. At the distal end of each piston 20 is a cam follower 22. The cam follower 22a of the pistons 20a in the first layer is arranged to rotate along a first cam surface, and the cam follower 22b of the pistons 20b in the second layer is arranged to rotate along a second cam surface. The first and second cam surfaces extend circumferentially around the rotor 2 and face the outside of the rotor 2. The first and second cam surfaces are contoured such that the radial distance between each cam surface 24 and the rotor 2 varies with position around the circumference of the rotor 2. Thus, the first cam surface and the second cam surface have a distal region 26 that is further from the outer surface of the rotor 2 than the proximal region 28. In some embodiments, the cam surfaces may have the same contour, and in other embodiments, the contours of the cam surfaces may differ from one another. While this embodiment includes two layers of pistons and two cam surfaces, it will be understood that in other embodiments, there may be more than two layers and / or cam surfaces. A plurality of permanent magnets 30 are attached to the splines 58 and are spaced around the rotor 2 at locations spaced along the longitudinal axis of the rotor 2 from the pistons 20. The permanent magnets 30 form part of a motor 32. The motor 32 also includes an annular array of coils 34, with the permanent magnets 30 concentrically arranged within the array of coils 34. Although this embodiment describes a motor in which the stator includes a plurality of coils and the rotor includes an array of permanent magnets, it will be understood that other types of motors can be used with embodiments in accordance with the present invention, so long as the motor includes a rotor and a stator.

[0144] Within the pintle 4 are formed (see Figs. 4-6): an inlet-spool flow gallery 36 providing a flow path between the pump inlet 38 (the inlet 38 being located at the opposite end of the pintle 4 relative to the control motor 12) and the spool 6; a spool-piston flow gallery 40 providing a flow path between the spool 6 and the first and / or second piston inlet apertures 42a, 42b; a piston-outlet flow gallery 44 providing a flow path between the first and / or second piston outlet apertures 46a, 46b and the outlet 48 of the motor-pump-valve assembly 1 (the outlet 48 being located at the opposite end of the pintle 4 relative to the control motor 12); and a return flow gallery providing a flow path between the spool 6 and the outlet 48. The first and second piston inlet apertures 42a, 42b are each in the form of a slot or groove extending around a portion of the circumference of the pintle 4 at the same axial location as the first or second layer of the pistons 20a, 20b, respectively. The first and second piston outlet apertures 46a, 46b are in the form of slots or grooves that extend around different portions of the circumference of the pintle 4 to the first and second piston inlet apertures 42a, 42b, respectively, but are still in the same axial position as the first or second layer pistons 20a, 20b, respectively. The first and second piston inlet apertures 42a, 42b are located opposite the distal regions 26 of the respective first and second cam surfaces 24. The first and second piston outlet apertures 46a, 46b are located opposite the proximal regions 28 of the respective first and second cam surfaces 24. In this embodiment, each cam surface 24 comprises two distal regions 26 and two proximal regions 28, which are alternately and equidistantly spaced along the circumference of the piston. Each layer of the pump includes two piston inlet apertures 42 and two piston outlet apertures 46, each occupying slightly less than 90 degrees of the circumference of the face of the pintle 4, with similar apertures located on opposite sides of the pintle 4. For clarity, not all of the flow galleries are shown in Figures 2 and 3.

[0145] The above-mentioned components are disposed within a housing 50, the interior of which is divided into two concentric sections along its entire length by an inner wall 52. The inner wall 52 extends circumferentially around the rotor 2 and separates the rotor 2 (including the permanent magnets 30 and pistons 20) and cam surface 24 from the coils 34 and the control motor coils 16. Within the housing 50, outside of the inner wall 52, are wires / cables 54 that can transmit power and / or control signals to the control motor 12 and motor 32.

[0146] In use, low pressure liquid enters pump-motor-valve assembly 1 at inlet 38 and travels through one or more inlet-spool flow galleries 36 in pintle 4 to cavity 8 containing spool 6. Spool 6 is rotated between different positions by control motor 12 such that positioning of spool 6 controls fluid flow by selectively providing one or more flow paths for fluid across the surface of spool 6 via contoured surface 7. Depending on the position of spool 6, fluid is directed from cavity 8 to (i) piston 20a of the first layer but not piston 20b of the second layer, (ii) pistons 20a, 20b of the first and second layers, (iii) pistons 20a, 20b of the first and second layers and pump outlet 38, or (iv) pump outlet 38. In cases (i) and (ii), spool 6 is positioned such that a flow path is formed from inlet-spool flow gallery 36 to spool-piston flow gallery 40. In case (iii), the spool 6 is positioned such that a flow path is formed from the inlet-spool flow gallery 36 to the spool-piston flow gallery 40 and the return flow gallery 49. In case (iv), the spool 6 is positioned such that a flow path is formed from the inlet-spool flow gallery 36 to the return flow gallery 49. In other embodiments, the spool may be positioned such that for a given position, fluid is directed from the cavity 8 to the second layer piston 20b rather than the first layer piston 20a.

[0147] In this embodiment, by supplying a current to the coil 34 in the presence of a magnetic field generated by the permanent magnet 30, an electromotive force is generated in a conventional manner, which rotates the permanent magnet 30 and the rotor 2 to which it is attached. This rotation of the rotor 2 drives the reciprocating motion of the piston 20 as the motion of the rotor 2 moves the cam follower 22 along the cam surface 24. As the radial distance between the cam surface 24 and the rotor 2 decreases, the cam follower 22 and the piston 20 to which it is attached are forced inwardly, expelling fluid from the piston chamber 18 through the first and second piston outlet apertures 46a, 46b and into the piston-outlet flow gallery 44. As the radial distance between the cam surface 24 and the rotor 2 increases, the piston 20 (which is biased toward an extended position) moves outwardly, drawing fluid from the spool-piston flow gallery 40 into the piston chamber 18 through the first and second piston inlet apertures 42a, 42b. In this way, the pressure of the fluid increases due to the action of the pump.

[0148] The present embodiment provides a variable displacement pump that allows the flow rate from the pump to be varied by controlling whether one or both layers of the pump are operating. In this manner, the pump according to the present invention may provide additional flexibility and / or allow more efficient operation over a wider range of operating conditions. Additionally and / or alternatively, the pump according to the present embodiment may provide this advantage while being compact and / or mechanically simpler than prior art pumps.

[0149] Each cam surface in this embodiment comprises two proximal regions and two distal regions, resulting in two cycles of piston movement for each rotation of the rotor. However, in some embodiments, the number of proximal regions may differ between different layers of the piston. Furthermore, the profile of the cam surface between different layers may differ in other ways, for example, by having a larger maximum distance between the rotor and the cam surface and / or by having a sharper rate of change of said distance. Thus, pumps according to embodiments of the invention may enable the pump to have different characteristics depending on which layer of the pump the fluid passes through, thereby increasing the flexibility of the pump and / or the efficiency of the pump over a wide range of operating conditions.

[0150] Using a spool valve to control fluid flow to the piston (as in this embodiment) may facilitate providing a more compact pump for a given flow rate and / or allow for a reduced number of pump parts, thereby reducing weight and / or cost. Additionally or alternatively, the use of a spool valve may provide a more responsive pump since the (relatively lightweight) spool can be quickly and precisely displaced to control the flow through the pump. However, it will be appreciated that the multi-layer pump may be used with a different control system, either integral with or separate from the motor-pump assembly (provided that said control system is capable of adequately controlling fluid flow to the piston).

[0151] In this embodiment the spool 6 is mounted for rotation and is therefore a rotary spool valve, however in other embodiments the spool may move axially.

[0152] The rotor 2 in this embodiment is both the rotor of the motor 32 and the rotor of the radial piston pump with the piston 20. The use of such a common rotor in a compound motor pump allows for a more compact pump design and / or a more responsive pump. Additionally or alternatively, the use of a common rotor can reduce the number of parts in the pump, not only because the rotors of the pump and motor are integrally formed, but also because no shaft and / or gearing is required to transfer the rotational motion generated by the motor to the rotor of the pump.

[0153] In this embodiment, one or more orifices (not shown) are formed in the surface of the pintle. In use, fluid pressurized by the action of the piston 20 is forced through these orifices to form a hydrostatic bearing between the pintle and the rotor. Thus, a pump according to this embodiment may have lower losses due to friction and / or a longer operating life.

[0154] Locating the inlet and outlet to the pump on the same end of the pintle (as in this embodiment) may facilitate easy connection of the motor and pump assembly to a hydraulic system, however, it will be appreciated that in other embodiments the inlet and / or outlet may have different locations.

[0155] In some embodiments, the inner wall 52 (and associated seals, if necessary) forms a watertight barrier within the housing 50. This allows fluid to flow through and around the rotor 2 while keeping the coils 34 and control motor coils 16 dry, thereby improving reliability and simplifying motor-pump construction by eliminating the need to separately protect electrical components from contact with the working fluid.

[0156] In some embodiments, a small amount of fluid leaks from the piston chamber 18 during use of the pump. The inner wall 52 may include features and / or flow galleries that provide a cooling effect by directing this fluid around and / or onto the rotor 2. Thus, an assembly according to the present invention may provide improved cooling of the pump and / or motor. Additionally or alternatively, such a cooling effect may be achieved without significantly reducing the efficiency of the pump by utilizing the fluid that leaks from the piston chamber 18.

[0157] In an embodiment of the invention shown generally in FIG. 9 using conventional symbols, a radial piston pump and motor assembly 101 similar to that described above in connection with FIG. 2 (except as otherwise described below) is used in a disc brake system 160. Similar components between FIG. 2 and FIG. 9 are indicated in FIG. 9 with the reference numerals increased by 100, for example, spool 6 in FIG. 2 is indicated in FIG. 9 with reference numeral 106. Disc brake system 160 comprises a radial piston pump and motor assembly 101 connected via inlet 138 to a fluid reservoir 161 and via outlet 148 to a brake caliper and pad assembly 162 adjacent to a brake disc 164. Although a single brake caliper and pads 162 are shown in FIG. 9, it will be understood that in other embodiments the brake caliper may be located on either side of the brake disc. As in FIG. 2, radial piston pump and motor assembly 101 comprises a spool 106 mounted for rotation within a cavity 108 (not shown in FIG. 9) to form a spool valve indicated in FIG. 9 with reference numeral 109. Movement of the spool 106 is provided by a control motor 104. The first layer pistons 122a and the second layer pistons 122b, together with associated cam followers etc., form first and second pumps 123a, 123b driven by a motor 132. In contrast to the arrangement of Figure 2, in the radial piston pump and motor assembly 101 of Figure 10, the spool valve 109 of Figure 9 is located downstream of the first and second pumps 123a, 123b.

[0158] As shown in FIG. 9, in standard schematic fashion, the spool valve 109 has four positions (each position corresponding to a different rotational position of the spool 106 within the cavity 108). These positions are labeled I, II, III, and IV in FIG. 9. Flow galleries (shown as lines in FIG. 9) connect (i) the fluid reservoir 161 to each of the first and second pumps 123a, 123b, (ii) each of the first and second pumps 123a, 123b to the spool valve 109, and (iii) the spool valve 109 to the fluid reservoir 161 and the brake caliper and pad assembly 162. Although the flow galleries are shown diagrammatically in FIG. 9 as straight lines, in practice the flow galleries may be curved and may extend around and encircle a portion of the brake caliper and pad assembly 162.

[0159] Mode I may be referred to as a passive mode. In Mode I, the inlet 138, outlet 148, and first and second pumps 123a, 123b are all connected, allowing fluid to flow freely between the pumps 123a, 123b, reservoir 161, and brake calipers and pads 162 through the spool valve 109. Mode I may be used when the brakes are released, or more specifically while the motor 132 is spinning up one or both of the pumps 123a, 123b before the brakes are engaged, allowing for faster transfer of hydraulic power to the brake calipers and pads 162 when the brakes are eventually engaged (Modes III and IV). Mode I may be used when there is advance warning that the user is about to brake suddenly, such as when a signal is received that the throttle pedal has been released too quickly or when an on-board sensor detects an obstacle. The pumps 123a, 123b and motor 132 have more inertia than the spool valve 109 and may take several milliseconds to spin up to full speed, in contrast to the spool valve 109, which can switch positions almost instantly. By utilizing the responsiveness of the spool valve to switch between passive and active modes, the pump according to this embodiment can provide more responsive braking. It will be appreciated that this mode of operation can be used in other systems aside from braking systems that similarly benefit from a more rapid delivery of hydraulic power.

[0160] Mode II is sometimes referred to as bypass mode. In Mode II, the spool 109 provides a flow path between both the first and second pumps 123a, 123b and the fluid reservoir 161. When the motor 132 drives one or both of the first and second pumps 123a, 123b, fluid is pumped back to the reservoir 161 but not back to the brake caliper and pad assembly 162. The resulting fluid flow can be used to cool the brake system 160 when the brakes are not engaged.

[0161] Mode III may also be referred to as partial operation. In Mode III, the spool provides a fluid path between the first pump 123a and the brake caliper and pad assembly 162, but does not provide a fluid path between the second pump 123b and the brake caliper and pad assembly 162, and the second pump 123b is connected to the reservoir 161. Thus, in Mode III, only a single layer of the radial piston pump and motor assembly 101 provides hydraulic power to the brake system 160.

[0162] Mode IV may also be referred to as full operation. In Mode IV, the spool provides a flow path between both the first and second pumps 123a, 123b and the brake caliper and pad assembly 162. No flow path is provided between the pumps 123a, 123b and the reservoir 161. Thus, in Mode IV, both layers of the radial piston pump and motor assembly 101 provide hydraulic power to the brake system 160. Mode IV is used when more hydraulic power is required than can be provided in Mode III. The ability to selectively use layers of the radial piston pump and motor assembly 101 allows the assembly 101 to achieve high flow rates, when needed, but also to operate more efficiently at lower flow rates.

[0163] FIG. 12 shows a variation of the embodiment of FIG. 9, in which a radial piston pump and motor assembly 101 similar to that described above in relation to FIG. 2 (except as otherwise noted below) is used in an active suspension system 170. Similar components between FIG. 9 and FIG. 12 are indicated with the same reference numerals in FIG. 12. Only those aspects of the embodiment of FIG. 12 that differ with respect to the embodiment of FIG. 9 will be described here. In FIG. 12, the suspension system 170 comprises a radial piston pump and motor assembly 101 connected via an inlet 138 to a fluid reservoir 161 and via an outlet 148 to an actuator 171 arranged concentrically with a coil spring 172. The actuator 171 is connected at one end to a chassis 174 (schematically shown in FIG. 12) of a motor vehicle (not shown) and at the other end to a wheel 176 (schematically shown in FIG. 12) of the motor vehicle. In other embodiments, the coil spring 172 may not be present.

[0164] In use, power is provided to the actuator 171, which can be used to vary the damping of the movement between the chassis 174 and the wheels 176. Mode I (passive mode) can be used when sensors detect an obstacle on the road, causing the pump to "spin up" and thereby more efficiently manage power from the engine. Modes III and IV are used depending on the amount of power required by the actuator (e.g., the amount of damping required), and Mode II can be used to cool the pump when the system is not engaged.

[0165] Figure 13 shows a variation of the embodiment of Figure 9 in which a radial piston pump and motor assembly 101 similar to that described above in relation to Figure 2 (except as otherwise noted below) is used in a flight control system 180. Similar components between Figures 9 and 13 are indicated with the same reference numbers in Figure 13. Only those aspects of the embodiment of Figure 13 that differ with respect to the embodiment of Figure 9 will be described here. In Figure 13, the flight control system comprises a radial piston pump and motor assembly 101 connected to an actuator 181 which is connected via an inlet 138 to a fluid reservoir 161 and via an outlet 148 to a control surface 182 attached to a portion of a wing 184 of an aircraft (not shown).

[0166] In use, fluid is supplied to actuator 181, which causes actuator 181 to move control surface 182, thereby changing the aerodynamic performance of wing 184. Mode I (passive mode) is used to "spin up" the pump prior to a maneuver, thereby efficiently managing power requirements within the aircraft. Modes III and IV are used depending on the amount of power required by the actuator to move flight control surface 182. Mode II can be used to cool the pump when the system is not engaged.

[0167] 10a and 10b show cross-sectional views of a hydraulic power pack 270 according to an exemplary embodiment of the invention in (a) an empty reservoir / full accumulator configuration and (b) a full reservoir / empty accumulator configuration. Similar components between FIG. 2 and FIG. 10 are indicated in FIG. 10 with the reference numeral 200 added, for example, rotor 2 in FIG. 2 is indicated in FIG. 10 with reference numeral 202. Power pack housing 250 includes a pintle 204 to which rotor 202 is attached. Pintle 204 is connected to housing 250 by an inner wall 252 that extends radially inward from housing 250 to pintle 204, and appears dome-shaped when viewed in cross-section in FIG. 10, with the convex side of the dome facing the right side of FIG. 10 and the distal end of pintle 204 on the left side of the figure. A stator 233 of motor 232 is disposed concentrically with rotor 202 and outside rotor 202. The rotor 202 includes a plurality of pistons (not shown) that together with the rotor 202 form a radial piston pump 223 (e.g., with multiple layers of pistons as described in FIG. 1 or with a single layer of pistons). In contrast to the embodiment of FIG. 2, the hydraulic power pack does not have a spool configured to control fluid flow within the pump. Extending through the axial through-bore 272 of the pintle 204 is a stem 274 of a fluid reservoir piston 276. At one end of the stem 274 (the left end in FIG. 10) is a reservoir piston head 278 that fits within a cylindrical portion of the housing 250, and at the opposite end of the reservoir piston head 278 forms a fluid reservoir 280 between the reservoir piston head 278 and the end of the housing 250 to the motor stator 233 and the rotor 202. At the other end of the stem 274 is a circumferential flange 282 that extends radially outward from the stem 274. A recess 284 extends into the stem 274 along the longitudinal axis from the end of the stem having the circumferential flange 282. A stem 286 of an accumulator piston 288 sits in the recess 284.The accumulator piston 288 has an accumulator piston head 290 at one end of the stem 286 (the end located on the right side in FIG. 10), which fits into the cylindrical portion of the housing 250 to form a pressure accumulator 292 on the proximal side of the accumulator piston head 290 to the motor stator 233 and rotor 202 (i.e., between the convex surface of the inner wall 252 and the piston head 290). On the opposite side of the accumulator piston head 290 to the motor stator 233 and rotor 202, a gas reservoir 294 is formed between the accumulator piston head 290 and the end of the housing 250. A control valve 296 is arranged between the reservoir piston head 278 and the motor stator 233 and rotor 202, and between the inner wall 252 and the motor stator 233 and rotor 202. 10(a), the fluid reservoir 280 is empty, the accumulator is substantially full, the reservoir piston head 278 is immediately adjacent an end of the housing 250, and the accumulator piston head 290 is adjacent an opposite end of the housing 250, thereby making the volume of the gas reservoir 294 relatively small. In FIG. 10(b), the fluid reservoir 280 is full, the accumulator is empty, the reservoir piston head 278 is spaced away from the end of the housing 250 that defines the fluid reservoir 280, and the accumulator piston head 290 is adjacent the inner wall 52, thereby making the volume of the gas reservoir 294 relatively large. The membrane wall 295 provides a watertight barrier separating the motor stator 233 and the rotor 202.

[0168] FIG. 11 shows a schematic cross-sectional view of the pintle 204 of FIG. 10. At the center of the pintle 204 is an axial throughbore 272 into which the stem 274 of the fluid reservoir piston 276 and the stem 286 of the accumulator piston 288 are received. A number of flow galleries, which appear substantially circular when viewed in the cross-sectional view of FIG. 11, are formed along the longitudinal axis of the pintle 204. These include (in clockwise order from the 12 o'clock position in FIG. 11) an auxiliary pressure flow gallery 281, a pump outlet flow gallery 283, a control valve return flow gallery 285, a pump inlet flow gallery 287, a control valve pressure flow gallery 281, a pump outlet flow gallery 283, and a pump inlet flow gallery 287, with flow galleries of the same type positioned opposite one another around the circumference of the pintle 204. A pump inlet flow gallery 287 is also present in the stem 274 of the fluid reservoir piston 276. Two pump inlet flow apertures 241 (shown in dotted lines in FIG. 11) are formed on the periphery of the pintle 204 and are connected to pump inlet flow galleries 287 in a plane spaced apart from the plane of the cross section of FIG. 11. The cross-sectional shape of each pump inlet flow gallery 287 varies in a region adjacent the pump inlet flow aperture 241 and expands from a circle to intersect with an aperture 287 that extends approximately 80 degrees along the periphery of the pintle 204. A pump outlet aperture 243 is similarly connected to each pump outlet flow gallery 283. An anti-rotation device 297 and a rotation sensor 299 are also disposed within the pintle 204.

[0169] In use, low pressure fluid is held in the fluid reservoir 280. Fluid from the fluid reservoir 280 passes through the reservoir piston head 278 and pump inlet flow gallery 287 in the stem 274, and into the pintle 204 (see FIG. 11) and into the pump 223 via the pump inlet flow aperture 241. Rotation of the pump is caused by supplying electrical current to a coil (not shown) in the motor stator 233. Fluid is pressurized in the pump 223 by the action of the reciprocating piston (as described above for FIG. 1), and then passes through the pump outlet aperture 243, into the pump outlet flow gallery 283 in the pintle 204 and into the inner wall 252 to the pressure accumulator 292. The accumulation of pressurized fluid in the pressure accumulator 292 applies pressure to the accumulator piston head 290, causing the accumulator piston 288 to move towards the right in FIG. 11, compressing the gas in the gas reservoir 294. The fluid in the pressure accumulator 292 also exerts a force on the surface of the circumferential flange 282, which causes the fluid reservoir piston 276 to move toward the left in Figure 10, thereby compressing the fluid in the fluid reservoir 280 and increasing the pressure. Pressurized fluid from the pump 223 is also supplied to the control valve 296 via the auxiliary pressure flow gallery 281, and fluid from the control valve 296 is returned to the fluid reservoir 280 via the control valve return flow gallery 285.

[0170] The use of a common rotor for the pump and motor of the hydraulic power pack may allow for a more compact power pack compared to power packs of similar capacity. Additionally or alternatively, the use of a pintle to provide flow galleries connecting the reservoir, accumulator, and pump of the hydraulic power pack may allow for a more compact power pack compared to power packs of similar capacity.

[0171] In this exemplary embodiment, the pintle functions as a fluid manifold connecting the reservoir, accumulator, and pump, providing a more compact power pack compared to a power pack of similar capacity. In this exemplary embodiment, the pintle also functions as a fluid manifold for the control valves present in the hydraulic power pack, since the pressure and return flow galleries for such valves are contained within the pintle. This provides a more compact power pack compared to a power pack of similar capacity and / or allows for the provision of a self-contained control unit for the hydraulic system to which the power pack is connected, said self-contained control unit being capable of providing both pressurized fluid flow and control flow. By keeping the "smart" elements of the hydraulic system within the self-contained control unit, the design of the hydraulic system can be simplified.

[0172] In the same or yet another embodiment, the pintle can function as a fluid manifold for control valves located outside of the hydraulic power pack and / or other auxiliary systems of the hydraulic system.

[0173] Although the present invention has been described and illustrated with reference to specific embodiments, those skilled in the art will appreciate that the present invention is susceptible to many different variations not specifically illustrated herein.

[0174] Where the foregoing description refers to integers or elements having known, obvious, or foreseeable equivalents, such equivalents are intended to be incorporated herein as if set forth separately. Reference should be made to the claims to determine the true scope of the invention, which should be interpreted to encompass all such equivalents. The reader will also understand that any integers or features of the invention described as preferred, advantageous, convenient, etc. are optional and do not limit the scope of the independent claims. It should further be understood that any such integers or features may be beneficial in some embodiments of the invention, while being undesirable and therefore may not be present in other embodiments.

Claims

1. 1. A radial piston pump comprising a rotor mounted for rotation on a pintle, said rotor having a plurality of piston chambers, pistons mounted for reciprocating movement in each of said chambers, said pump comprising: at least one supply channel connecting, in use, one or more of said piston chambers to a source of low pressure fluid; at least one outlet flow passage through which, in use, high pressure fluid from one or more of said piston chambers is discharged from said pump; at least one auxiliary flow passage connecting another component of the pump to one or more of the piston chambers; the pintle comprising a plurality of flow galleries including at least one supply flow gallery forming a portion of the supply flow passage, at least one outlet flow gallery forming a portion of the outlet flow passage, and at least one auxiliary flow gallery forming a portion of the auxiliary flow passage.

2. 2. The radial piston pump of claim 1, further comprising a return flow path connected to an outlet of the other component of the pump, whereby, in use, fluid is discharged from the other component and / or the pump via the return flow path, and the plurality of flow galleries includes at least one return flow gallery forming part of the return flow path.

3. 2. The radial piston pump of claim 1, wherein the plurality of flow galleries are integrally formed with the pintle.

4. 2. The radial piston pump of claim 1, wherein the plurality of flow galleries are at the same axial location on the pintle.

5. 2. A radial piston pump as claimed in claim 1, wherein said further component of the pump is a control valve, and in use said auxiliary flow passage is connected to a pressure inlet of said control valve.

6. 6. The radial piston pump of claim 5, wherein the control valve is a servo valve, e.g. a three-way servo valve or a four-way servo valve, and the pump is configured to supply first and / or second service flows to actuators or other hydraulic components connected to the pump.

7. 1. A method of operating a radial piston pump comprising a rotor mounted for rotation on a pintle, said rotor having a plurality of piston chambers, pistons mounted for reciprocating movement in each of said chambers; - fluid flows from a source of low pressure fluid along at least one supply channel to one or more of said piston chambers; - high pressure fluid from one or more of said piston chambers is discharged from said pump via at least one outlet passage; - high pressure fluid from one or more of said piston chambers flows via at least one auxiliary flow path to another component of said pump and is used in the operation of said component; The method, wherein fluid on the at least one supply passage, the at least one outlet passage, and the at least one secondary passage passes through one or more flow galleries in the pintle.

8. A hydraulic power pack comprising a radial piston pump according to any one of claims 1 to 7.

9. 9. The hydraulic power pack of claim 8, further comprising a reservoir and an accumulator, the power pack being configured such that, in use, low pressure fluid from the reservoir is supplied to the pump and high pressure fluid from the pump is supplied to the accumulator.

10. a fluid reservoir piston that at least partially defines the fluid reservoir; an accumulator piston that at least partially defines the accumulator; 9. The hydraulic power pack of claim 8, further comprising: said fluid reservoir piston, said accumulator piston and said rotor being concentric.

11. 11. The hydraulic power pack of claim 10, wherein the rotor is mounted for rotation on a pintle and at least a portion of the fluid reservoir piston and / or accumulator piston is received within a piston recess formed in the pintle.

12. 9. The hydraulic power pack of claim 8, configured such that force generated by the high pressure fluid in the accumulator is transferred to the low pressure fluid in the reservoir via the fluid reservoir piston.

13. A vehicle brake system, comprising a radial piston pump according to any one of claims 1 to 7.

14. 14. The brake system of claim 13, comprising brake pads, an actuator configured to move the brake pads from a first position to a second position to effect braking of the wheels of the vehicle, and a fluid reservoir for storing low pressure fluid, the brake system configured such that, in use, low pressure fluid from the reservoir is supplied to the pump and high pressure fluid from the pump is supplied to the actuator.

15. An active suspension system for a vehicle, comprising a radial piston pump according to any one of claims 1 to 7.

16. 16. The active suspension system of claim 15, wherein the system comprises an actuator configured to exert a force on a wheel and / or a chassis of a vehicle, and the active suspension system is configured such that, in use, high pressure fluid from the pump is supplied to the actuator.

17. A flight control system for an aircraft, the flight control system comprising a radial piston pump according to any one of claims 1 to 7.

18. 18. The flight control system of claim 17, wherein the system comprises an actuator and a control surface, the actuator configured to move the control surface from a first position to a second position to modify an aerodynamic performance of the control surface, and the flight control system configured such that, in use, high pressure fluid from the pump is supplied to the actuator.

19. 8. A method of manufacturing a radial piston pump according to any one of the preceding claims, the method comprising manufacturing one or more of the rotor, pintle and / or spool using an additive manufacturing process.

20. 20. A method of manufacturing the radial piston pump of claim 19, the method including finishing a rotor, a pintle and / or a spool manufactured using an additive manufacturing process using a subtractive manufacturing process.

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