Metering pump

Abstract

The invention relates to a linear-action pump device (1) for metering a fluid moving between a front casing (2) and a rear port (3) of the pump device (1), the pump device comprising: a magnetic motor unit (11) configured to drive a piston (10) in a reciprocating manner along a central axis (OX); a control unit (21) comprising the piston and elements configured to return the piston to its initial position after each pumping cycle; and a housing (108) made of non-magnetic material and suitable for surrounding the control unit, the housing being suitable for axially guiding the piston in a bore of the housing. The magnetic motor unit (11) comprises a C-shaped magnetic yoke (111, 113) suitable for receiving a coil (102) and the housing (108), the magnetic yoke being configured to concentrate a magnetic flux generated by the coil (102) around an armature (10a) of the piston along the central axis (OX) when the piston moves relative to the housing. The pump device further comprises at least one of: a friction bearing (107) located at one end of the piston, and a rear stop (114) configured to limit the axial movement of the piston.

Description

Dosing pump Technical field of the invention

[0001] This description concerns a metering pump. In particular, this description relates to a linear-acting pump device for metering a fluid into an injector. State of the art

[0002] Diesel engines require exhaust gas treatment to meet existing emissions regulations. These regulations aim to control the emission of nitrogen oxides (NOx) from the exhaust of diesel engines.

[0003] During the operation of internal combustion engines, these nitrogen oxides are formed during operation with an excess of oxygen, as is the case in the majority of diesel engine operating conditions.

[0004] According to the prior art, a reduction catalyst is supplied to the exhaust gas stream to reduce nitrogen oxide emissions. It is known, in this case, to supply an aqueous urea solution as a reducing agent to the exhaust gases, distributing it finely before it enters the catalyst.

[0005] Thus, the amount of urea supplied must be precisely adjusted according to the combustion process, in order to ensure optimal reduction within the catalyst, while avoiding an excess of urea.

[0006] For this purpose, it is known to use adapted pumps to pressurize and meter fluids. One arrangement involves a motor adapted to guide a piston within a bore, with proper sealing and as little friction as possible. Such pumps are often used in Selective Catalytic Reduction (SCR) systems to reduce NOx emissions in the exhaust gases of diesel engines.

[0007] For example, US Patent Application No. US 2008 / 138221 A1 discloses a pump for metering and supplying a reducing agent to the exhaust gas stream. This pump includes hydraulic components and a hydraulic circuit and is easy to assemble. The amount of reducing agent delivered to the exhaust gas stream can be adjusted by activating the metering pump. The pump pressurizes a liquid within a given range and measures the metered volume in real time to monitor the operation of the distribution system.

[0008] However, known systems and pumps have several drawbacks.

[0009] One drawback of modern pumps is their requirement for high-precision components and hard friction surfaces, which significantly increases production costs. A precise fit between the piston and the bore, ideally with minimal clearance, is essential for optimal guidance and to reduce the risk of hydraulic leaks.

[0010] Another disadvantage of existing pumps is that their design involves high costs.

[0011] Furthermore, the materials used for these pumps often require hardening treatments or special coatings to ensure durability and reduce wear over time. Given the use of aqueous fluids in the system, there is also a need for durable pumps that are significantly more resistant to corrosion. Object of the invention

[0012] In order to address this or these drawbacks, a linear action pump device is proposed under one of the present terms for metering a fluid moving between a front casing and a rear port of a pump unit of said fluid, said pump device comprising: - a magnetic motor unit configured to drive, via a reciprocating motion of the linear action pump device, a piston of a control unit, the magnetic motor unit being adapted to be mechanically connected to the front casing of the fluid pump unit,

[0013] - said control unit,

[0014] in which the piston of the control unit is configured to cooperate in translation with the magnetic motor unit by moving alternately along a central axis of the pump device.

[0015] According to one possible embodiment, the control unit is a unit adapted to ensure a sealing function against the movement of the fluid, a stop function and a return function against the reciprocating movement of the piston of the control unit along the central axis of the pump device.

[0016] According to one embodiment, the control unit is adapted to be mechanically connected, on the one hand, to the rear port of the injector and, on the other hand, to the magnetic motor unit, the reciprocating movement of the piston relative to the magnetic motor unit implementing controlled metering of the fluid.

[0017] According to one embodiment, the pump device comprises a housing made of non-magnetic material and adapted to surround the control unit, the housing being further adapted to axially guide the piston in a bore of said housing.

[0018] Advantageously, such a non-magnetic housing maximizes the efficiency of the magnetic flux in the device, while ensuring precise guidance of the piston along the central axis.

[0019] According to one embodiment, the magnetic motor unit includes a "C"-shaped magnetic junction adapted to accommodate a coil and the housing, said magnetic junction being configured to concentrate a magnetic flux generated by the coil around a piston armature along the central axis when the piston moves relative to the housing.

[0020] In this text, a "C" shape is an open form with a partially enclosed curved structure, defining an internal space to accommodate the coil and housing. This form comprises two parallel or diverging arms connected by a curved central portion. This optimizes the concentration of the magnetic flux generated by the coil within the piston armature by directing and channeling the magnetic flux towards the central axis of piston movement, while minimizing magnetic flux losses at the open ends of the junction.

[0021] According to one embodiment, the pump device further comprises at least one of the following:

[0022] - a friction bearing located at one end of the piston,

[0023] - a rear stop configured to limit the axial movement of the piston,

[0024] - a front stop and a support for said front stop, said front stop and said support being included in the control unit and being positioned to control the stroke of the piston along the central axis, and / or

[0025] - a spring located downstream of the piston and upstream of the front stop and the front stop support, said spring being included in the control unit and being positioned to ensure a return of the piston to its initial position after at least one cycle of the reciprocating motion of the piston.

[0026] According to one possible embodiment, the friction bearing includes a bushing and / or provides a guiding function between the piston and the housing that comprises the device.

[0027] According to one embodiment, the spring is dimensioned to fit into the support of the front stop, the spring being further adapted to allow controlled movement of the piston stroke along the central axis.

[0028] This allows the spring inserted in the front stop support to precisely control the movement of the piston along the central axis, maintaining the position of the piston after each cycle of movement, which can be achieved by minimizing vibration and wear of the components.

[0029] According to one embodiment, the magnetic motor unit is made of a soft magnetic material.

[0030] In this context, a magnetically soft material is a ferromagnetic material with low coercivity, typically less than a few hundred A / m, high relative magnetic permeability (which can reach several thousand, dimensionless), and minimal hysteresis losses. These properties allow for rapid reversibility of magnetization under the influence of an external magnetic field, making the material suitable for applications requiring rapid changes in magnetic flux. Examples of compatible materials include one or more alloys of iron, nickel, or cobalt.

[0031] According to one embodiment, the motorized magnetic unit includes a C-shaped magnetic junction adapted to accommodate the coil and housing, said junction being configured to concentrate a magnetic flux generated by the coil around the piston armature along the axis when the piston moves relative to the armature.

[0032] According to one embodiment, the housing includes an O-ring located at one end of the housing to ensure static sealing with the magnetic motor unit.

[0033] According to one embodiment, the housing includes a "V" shaped seal adapted to compensate for misalignments between the piston and said housing along the axis.

[0034] According to one embodiment, the presence of seals, for example O-rings and / or V-shaped seals, makes it possible to maintain optimal sealing despite misalignments between the piston and said housing along the axis, ensuring effective separation between the high and low pressure zones in the device.

[0035] Furthermore, in order to address this or these drawbacks, a selective catalytic reduction system for diesel engines is also proposed under another object of the present document, comprising the linear action pump device for metering a fluid according to the invention and the pump unit for said fluid, the SCR system further comprising the front casing and the rear port, the pump device being inserted into said pump unit, said injector, the pump device being further connected, at a first end, to the front casing and, at a second end opposite to said first end, to the rear port, and in which: the magnetic motor unit of the pump device is connected to the front casing, the control unit of the pump device is connected to the rear port.

[0036] In this document, a selective catalytic reduction system is referred to as an SCR system. Brief description of the figures

[0037] Other features, details, and advantages will become apparent upon reading the detailed description below and analyzing the attached drawings, on which:

[0038] Figure 1 illustrates a perspective view of a pump device according to one embodiment of the invention.

[0039] Figure 1 illustrates a cross-sectional view of a pump device according to one embodiment of the invention.

[0040] Unless otherwise indicated, elements common or similar to several figures bear the same reference signs and have identical or similar characteristics, so that these common elements are generally not described again for the sake of simplicity.

[0041] Lare represents a perspective, or exploded, view of different components of a pump device according to an embodiment of the invention.

[0042] In particular, several elements of a linear-acting pump device 1 are shown, this device 1 and its elements being adapted to be integrated into a fluid pump unit, for example to pump this fluid into a circuit of a selective catalytic reduction system, called an SCR system, or into an injection system of such an SCR system.

[0043] As illustrated, the linear action pump device 1 comprises a motorized magnetic motor unit 11 and a control device 120.

[0044] According to one embodiment, in the front part of the linear action pump device 1 and along a central axis "OX" and are located, respectively, from downstream to upstream to downstream in the direction of fluid flow, the liquid flowing from right to left in the figure, a pallet support 12 as well as one or more pallets 6. This front part is adapted to be connected to the front housing 2 of an injector 1 (not visible), which serves as the fluid discharge port, and into which the linear action pump device 1 can be inserted.

[0045] According to one embodiment, one end of the linear action pump device 1 is adapted to be connected to a hydraulic block, said hydraulic block being itself connected to a fluid injector or to a pipeline which is connected to the pump unit.

[0046] According to one embodiment, the pallet(s) 6 comprise a non-return valve. In a possible variant of this embodiment, this non-return valve is formed of a blade, this blade being actuated by the passage of fluid which opens or closes the fluid passage.

[0047] According to one embodiment, a pallet support 12 defines an inlet pallet 12, which is fixed to one end of the piston 10 and is configured to regulate the entry of the fluid into the pump device 1, in particular into the pumping chamber of the latter.

[0048] According to one embodiment, the pump device 1, for example a pumping chamber of the pump device 1, includes two valves, the first valve being integrated into the piston to allow the pumping chamber to be filled when the pump draws in the fluid and blocking the flow when the pump device 1 discharges the fluid, while the second valve 6 allows the fluid to pass through when the pump discharges and blocks the fluid at the level of the casing 2 when the pump draws in the fluid.

[0049] According to one embodiment, the magnetic motor unit 11 comprises a junction and a coil 102. The junction comprises two armatures, a downstream armature 111 and an upstream armature 113. The junction and the coil 102 are adapted to be joined together, the junction and the coil 102 then being aligned along the central axis "OX" of the linear action pump device 1, this central axis "OX" then passing through the coil 102 along a height of the latter.

[0050] Advantageously, the magnetic circuit formed by the magnetic motor unit 11 is isolated from contact with the passage of any fluid moving in the linear action pump device 1, or in the pump unit 1 in which said linear action pump device 1 may be placed.

[0051] In one embodiment, several separating elements may be present in the linear-acting pump device 1. These separating elements, described in detail below, contain the fluid and prevent external leakage. Additionally, this reduces the risk of degradation of the magnetic properties of the assembly, particularly due to potential corrosion caused by fluid movement.

[0052] According to one embodiment, the junction is magnetic, and the downstream reinforcement 111 itself comprises a sub-reinforcement 111a, preferably formed of a material with high magnetic performance, and which optionally has a "C" shape.

[0053] Advantageously, this "C" shape facilitates the alignment of the magnetic motor unit 11 with the other elements of the linear action pump device 1 and along the central axis "OX".

[0054] As illustrated, the vertical upright of the "C" formed by the sub-reinforcement 111a can be provided with a hole adapted to cooperate mechanically with a pole piece 111b, by simple insertion.

[0055] In the illustrated embodiment, the pole piece 111b is preferably made of a non-magnetic material. The pole piece 111b holds and positions the components of the magnetic motor unit 11. These components are thus held in a position that controls the geometry of the magnetic circuit. This geometry is achieved, for example, by means of an overmolded pole piece 111b, the dimensions and shape of which are adapted to cooperate directly with the hole in the sub-armature 111a.

[0056] In this configuration, the coil 102 of the magnetic motor unit 11 is configured to create a magnetic field useful for the operation of the linear action pump device 1 by causing the movement of the piston system formed by parts 10 and 10a and / or the control device 120 along the axis "OX", as described below.

[0057] In other words, the junction formed by the downstream armature 111 and the upstream armature 113 allows, when the magnetic motor unit 11 is in operation, to drive a movement of the piston 10 and 10a.

[0058] Advantageously, the magnetic motor unit 11 is configured to generate linear piston motion about the "OX" axis. This linear motion is further modified by fluid movement within the pump device 1 and / or by a restoring force provided by a return element. This type of motion corresponds to the principle of damped mechanical oscillations, where the piston moves successively between two extreme positions in a repeated cycle.

[0059] One embodiment of the reciprocating motion of piston 10 (and 10a) is generated by a magnetic excitation phase, also called the "motor" phase, during which a current pulse passes through the coil 102 of the magnetic motor unit 11. This current flow induces a magnetic field that causes the piston 10 to move along the central axis "OX". When the current ceases, a restoring element, such as a spring 104 described below, returns the piston 10 to its initial position by means of an elastic restoring force.

[0060] This embodiment is based on a succession of driving and restoring phases, forming an oscillation cycle of the piston. The driving phase is characterized by the application of a magnetic force which causes the piston to move in a first direction.

[0061] In this embodiment, the spring 104 is located downstream of the piston 10 and upstream of the front stop 116 and its support 115. The spring 104 is typically contained within the control unit 21, its position ensuring the return of the piston 10 to its initial position after at least one cycle of its reciprocating motion. The return phase is ensured by the spring 104, which exerts an opposing force to bring the piston back to its initial position.

[0062] The fluid located in the linear action pump device 1 undergoes this movement, consuming the mechanical energy supplied by the piston to convert it into hydraulic energy, generated by the flow and pressure of the fluid.

[0063] In this embodiment, the sequence of motor phases necessary to establish pumping is achieved by regulating the current through the coil 102. The efficiency of this movement is enhanced by the presence of one or more return elements associated with the piston 10 and / or by the possibility for the piston 10 to slide on a bearing. This bearing allows for precise guidance of the axial movement of the piston and reduces mechanical friction between the various moving parts of the device, thus optimizing the conversion of mechanical energy into hydraulic energy.

[0064] In other words, in this embodiment, after the movement generated by the magnetic force induced by the current flowing through the coil 102, the piston 10 returns to its initial position under the effect of the return element, thus creating a continuous alternation between the so-called "driving" phases and the return phases. This alternating cycle ensures continuous pumping, each "driving" phase being followed by a release phase that maintains the smooth and regular movement of the piston 10 along the axis "OX". This operation also contributes to efficiently converting the electrical energy supplied by the coil into hydraulic energy in a controlled manner, thanks to the combination of magnetic excitation and optimized piston return.

[0065] The coil 102 is designed to cooperate with the armature 111a and / or the front part 111b, aligning with them along the OX axis. The coil 102 also includes at least one electrical connector, although flying leads can be used as an alternative. This optimizes magnetic energy transfer and ensures efficient concentration of the magnetic flux, thereby improving the operation of the linear-acting pump device.

[0066] The magnetic motor unit 11 is designed to be inserted into a fluid pump unit 1 (not shown in the figure). A limit switch 21 is designed to be inserted into the housing 108, along the axis "OX", substantially parallel to the height passing through the center of the coil 102. This limit switch dampens and controls the end of the stroke of the piston 10, thus ensuring smooth and precise movement. It is also advantageous to provide a rigid connection between the magnetic motor unit 11 and the limit switch 21 to guarantee optimal stability.

[0067] According to one embodiment, the piston 10 is composed of several sub-elements, including an armature 10a and a piston body. The armature 10a interacts directly with the magnetic field generated by the coil 102.

[0068] According to one embodiment, the coil 102 of the magnetic motor unit 11 is placed around, or in, the junction formed by the armatures 111 and 113. The coil 102 is further adapted to be connected to an external power supply by means of electrical connectors, these preferably allowing precise control of the magnetic field generated in the coil 102, for example under the effect of electrical voltage pulses.

[0069] In one embodiment, the armature 10a is made of a magnetic material exhibiting low hysteresis and high magnetic permeability, enabling optimal device responsiveness. This material is preferably a magnetizable ferritic stainless steel or a silicon steel. This part of the system is immersed in the liquid and advantageously resists contact with the fluid, particularly during corrosion. The piston body 10 is mechanically connected to the armature 10a, thus ensuring the transfer of the magnetic force to the fluid through the linear movement of the piston.

[0070] Advantageously, the piston 10 can be guided in a bore or sleeve designed for this purpose.

[0071] According to one possible embodiment, coil 102 is not overmolded, which improves natural convection and better cooling of the winding.

[0072] According to one possible embodiment, the magnetic motor unit 11 is isolated from the fluid or surrounding environment by a non-magnetic container or tube such as the housing 108

[0073] In one embodiment, one end of the magnetic motor unit 11 located downstream of the pump device 1 is adapted to be connected to another junction 113, to one or more seals 109, to the housing 108 and / or to the control unit 21. It is important that this connection be made for optimal operation of the pump device 1.

[0074] According to one embodiment, the housing 108 is a tube comprising a thin wall, this wall having a thickness of less than 0.55 millimeters, allowing the housing 108 to define an isolation tube, equivalent to a separation tube.

[0075] As illustrated, the linear action pump device 1 also includes the control unit 21.

[0076] According to one embodiment, the control unit 21 and the magnetic motor unit 11 are adapted to be positioned centrally relative to each other along the axis "OX", or even to be connected to each other, for example via the junction 113.

[0077] Advantageously, the junction 113 can be configured to hold the entire magnetic unit in position and aligned with the OX axis. The junction 113 also enhances the rigidity of the assembly while ensuring a uniform distribution of magnetic flux around the piston 10, as discussed below. In one possible example, the junction 113 is made of a soft iron-type material or any other material with low magnetic coercivity and high magnetic permeability.

[0078] In one embodiment, the control unit 21 is inserted into a housing 108, at the end of which an O-ring 109 provides a connection with the magnetic motor unit 11. The O-ring 109 creates a seal with and / or around the control unit 21.

[0079] According to one embodiment, the housing 108 is made of austenitic stainless steel with low magnetic permeability. This prevents an unwanted magnetic short circuit between the magnetic motor unit 11 and the junction formed by the armatures 111 and 113. Advantageously, the low magnetic permeability of the housing 108 prevents a short circuit between the armatures 111 and 113 of the junction.

[0080] According to one embodiment, the housing 108 is adapted to contain the fluid out of the magnetic motor unit 11, which also improves the service life of the internal components by avoiding any corrosive contact with the fluid.

[0081] Advantageously, the geometry of these elements is designed so that the fluid does not enter the magnetic circuit, since the latter is confined around the coil. This therefore ensures a functional separation between the magnetic part and the fluid path.

[0082] According to one embodiment, a spring 104 is placed in the control unit 21 and is configured to return the piston 10 to its initial position after each pumping cycle.

[0083] A magnetic actuator is thus provided that can be alternately of the "push" type and of the "pull" type, the movement of the piston 10 being caused by the generated magnetic excitation, and returned by the spring 104, as previously described with regard to the alternating movement of the piston 10.

[0084] Advantageously, a pump powered by a motor or magnetic actuator of the "push" type produces the necessary hydraulic work in terms of flow and pressure with a magnetic force, the return of the piston 10 being ensured by the spring 104. On the other hand, a motor or magnetic actuator of the "pull" type allows the spring 104 to be compressed and the hydraulic work to be generated in terms of flow by releasing the force of the spring.

[0085] According to one embodiment, the housing 108 can be made of various types of materials, preferably chosen to provide insulation between the fluid path and the external magnetic circuit when the pump is operating. It is therefore important that the housing 108 withstand contact with the fluid and be magnetically insulating to prevent magnetic short circuits. For example, the housing 108 can be made of a non-magnetic material or a synthetic material, such as a thermoplastic or thermosetting material.

[0086] Preferably, the 108 housing is thin to minimize magnetic gap, for example with a thickness of 0.3 millimeters. The 108 housing can be manufactured by deep drawing or rotational forming, hydroforming, or flow forming.

[0087] Advantageously, this composition allows the junction 111 to be magnetically isolated at the level of the active air gap.

[0088] Advantageously, the previously described junction 111 makes it possible to ensure an efficient concentration of the magnetic field on the piston armature.

[0089] According to one embodiment, the control unit 21 includes the spring 104, a front stop support 115, the front stop 116, and a V-shaped seal 110, although other shapes are possible for said seal 110. This ensures a seal around the piston, and thus ensures the absence of leakage in the pumping chamber.

[0090] In one embodiment, the spring 104 is supported by a bracket 115 of the front stop 116, this bracket 115 being positioned so as to limit the displacement of the piston 10 during the return phase of its reciprocating motion. Advantageously, the combination of the spring 104 and the bracket 115 allows for more precise control of the piston stroke and reduces any potential vibrations.

[0091] This arrangement also allows control of the deceleration energy of piston 10 and / or control of the use of the pump device 1 by measuring the distance traveled by the piston, and indirectly its ability to meter the volume of fluid pumped. This can be done, for example, by counting the number of strokes completed.

[0092] According to one embodiment, the spring 104 has a diameter smaller than that of the support 115, and is intended to fit into it.

[0093] According to one embodiment, the spring 104 can be dimensioned to ensure high-frequency operation. For example, the moving assembly returned by the spring 104 has a natural frequency greater than 45 hertz, with a moving mass that can exceed 30 grams.

[0094] Advantageously, the spring 104 has dimensions and stiffness suitable for regular use in combination with the movements of the piston 10. It is possible, for example, to supply a spring 104 capable of operating over 900 million return cycles, or even more.

[0095] According to one embodiment and in the control unit 21, the "V" joint 110, the support 115, the front stop 116 and the spring 104 of the control unit 21 are located in front of the piston system 31.

[0096] According to one embodiment, upstream of the piston 10 it comprises, the pump device 1 includes a piston system, said piston system comprising a friction bearing 107 described below, a rear thrust bearing 114, and an O-ring 105. Each of these elements contributes to limiting or even stopping the movement of the piston 10 when it reaches the end of its stroke during a cycle, for example, when it abuts against the rear port 3. The rear port 3 can, in particular, be the rear port of a fluid pump unit 1 included in the pump device 1.

[0097] When the V-shaped seal 110, the front stop support 115, the front stop 116 and the spring 104 are assembled together as illustrated, their assembly allows control of friction and wear between the parts during reciprocating movement of the piston 10, while ensuring effective dynamic sealing, even in the presence of misalignments along the axis "OX".

[0098] According to one embodiment, the friction bearing 107 and the V-shaped seal 110 cooperate together to guide the piston 10 along the axis OX.

[0099] Advantageously, the V-shaped seal 110 compensates for any misalignment of the piston 10, while maintaining an effective seal even under pressure variations. The O-ring 109, located downstream of the piston 10, complements this function by providing a static seal between the components of the engine unit 11 and the housing 108.

[0100] Advantageously, this sealing is particularly ensured in the case of misalignments which appear or would appear due to the separation of the guiding and sealing functions of the pump device 1 when it is in operation.

[0101] As illustrated elsewhere, the housing 108 is adapted to include a hollow space into which the spring 104, a V-shaped seal 110, a support 115, and the front stop 116 can be inserted. The seal 110, the support 115, the front stop 116, and the spring 104 can all be inserted into the control device 120.

[0102] Advantageously, the seal 110 has a "V" shape. Other shapes are possible, however, and it is possible to replace it with an O-ring or to omit the bearing 107 entirely when the fluid has highly lubricating properties.

[0103] Advantageously, the seal 110 ensures axial and sealed guidance of the piston 10 and the piston system 31, while optimizing this guidance centrally along the axis "OX".

[0104] In combination with the support 115 and the front stop 116, a dynamic seal is also implemented between the high pressure side and the low pressure side of the pump device 1, i.e. between the upstream and downstream sides along the axis "OX".

[0105] Advantageously, the rear stop 114 as well as the combination of the support of the front stop 115 and the front stop 116 make it possible to limit the axial stroke of the piston 10 along the axis "OX".

[0106] Preferably, the rear stop 114 is placed upstream of the piston 10, limiting the stroke of said piston 10 in the opposite direction and thus providing precise control of the movement of the piston 10 while avoiding an overstroke which could damage the device.

[0107] Advantageously, the materials of the elements forming the control unit 21, the piston 10, the housing 108, and / or any other element likely to contribute or participate in the linear reciprocating motion of the piston 10, can be selected so as to reduce friction and / or extend the service life of the components.

[0108] In one embodiment, these materials are selected from thermosetting materials, such as a polyetheretherketone material, called PEEK, possibly filled with polytetrafluoroethylene, called PTFE. These materials can also be chosen as polyphenylene sulfide, called PPS, or polyacetal, called POM. Advantageously, their cost is lower than that of machined metal parts, making their use more cost-effective and durable.

[0109] According to one embodiment, these materials are combined with additives such as carbon graphite, PTFE or any other agent to ensure friction control.

[0110] According to one embodiment, the friction bearing 107, the rear stop 114, the support 115 for the front stop 116, and said front stop 116 may also be made of PTFE and / or comprise a polyamide support, for example PA66. Either of these elements may also comprise polyacetal, which is more advantageous than PTFE in terms of moldable properties.

[0111] Advantageously, the friction bearing 107 and the rear stop 114, which is optionally of the same shape and / or composition as the front stop 116, together contribute to axially guiding the piston system 31. The dimensions of these elements are preferably sufficiently small and, for example, on the order of 0.35 millimeters.

[0112] According to one embodiment, the male end of the piston 10 is partially hollow so as to allow the passage of fluid in the piston from upstream to downstream, and vice versa, of the linear action pump device 1.

[0113] According to one embodiment, said paddles (not visible) are preferably circular so as to be able to be inserted into the male end of the piston 10, which has a circular shape, these paddles being able to have a surface having different shapes, in order to dose the passage of fluid at each back-and-forth movement of the piston 10, the fluid then passing through the inside of the latter.

[0114] According to one embodiment, the end of the piston 10 opposite the male end is adapted to be able to cooperate with the friction bearing 107.

[0115] According to one embodiment, device 1 includes a freeze-compensating element 112. This element 112 is, for example, a cylindrical compensator formed of foam, this foam comprising an internal channel allowing the passage of fluid through a mid-height

[0116] In one embodiment, the foam of a compensator comprising the freeze-compensating element 112 is formed of a closed-cell foam and, preferably, has the capacity to manage and / or reduce fluid volume variations due to fluid phase changes, which may occur, for example, during temperature changes. In other words, this allows, among other things, the counteracting of the effects of potential freezing inside the pump device 1, as the foam compresses, thereby absorbing any volume increases related to fluid phase changes.

[0117] According to one embodiment, the foam described above can also be advantageously designed to avoid the risks of overpressure due to fluid expansion at low temperatures, thus reducing the risks of damage to the internal components of the device.

[0118] According to one embodiment, upstream of the compensator 107, located along the axis "OX" and connected to it, the rear stop 114 and an O-ring 105 close the assembly. The rear stop 114 takes, for example, the form of a ring.

[0119] Laillustre a cross-sectional view of an injector comprising a pump device according to an embodiment of the invention.

[0120] In particular, a pump unit 1 is shown equipped, inside its frame, with the linear action pump device 1, the assembly being thus configured to meter a fluid moving between a front casing 2 and a rear port 3 of this pump unit 1, for example intended for an SCR system.

[0121] In one embodiment, the front housing 2 has a mounting point for securing the pump device 1 within the structure of the pump unit 1. The front housing 2 is advantageously connected to the housing 108 to provide optimal alignment of the internal pump components and ensure a stable and secure mounting, guaranteeing optimal stability during movement.

[0122] According to one embodiment, the rear port 3, located at the opposite end of the device, ensures the admission of the fluid, so that the fluid flows from right to left in the figure. Advantageously, the port 3 is aligned with the "OX" axis and is designed for a tight connection with the external piping of the SCR system.

[0123] Advantageously, the piston 10 is fitted within the housing 108 and is aligned along the OX axis with the other components of the magnetic motor unit 11 and the control unit 21.

[0124] In operation, i.e. when the linear action pump device 1 is installed between the front casing 2 and the rear port 3 of a pump unit 1, the pump operates in a reciprocating motion, i.e. the magnetic motor unit 11 acts on the piston 10 to move it linearly along the axis OX.

[0125] The solution proposed herein allows the pump's sealing function to be separated to achieve appropriate volumetric efficiency, while ensuring guidance within the frame to allow its movement. This guidance is achieved in particular through its geometry, with the linear-acting pump device 1 sliding along the "OX" axis.

[0126] This provides a pumping device capable of performing both pumping and / or metering functions for a fluid. This pump is preferably used to pressurize and meter a reactive element for diesel engines, in particular a reactive element useful for the operation of an SCR system or a corresponding catalyst, in order to more efficiently convert NOx from diesel engine exhaust gases.

Claims

A linear-acting pump device (1) for metering a fluid moving between a front casing (2) and a rear port (3) of a pump unit (1) of said fluid, said pump device (1) comprising: a magnetic motor unit (11) configured to drive, via a reciprocating motion of the linear-acting pump device (1), a piston (10) of a control unit (21), the magnetic motor unit (11) being adapted to be mechanically connected to the front casing (2) of the fluid pump unit (1), said control unit (21), wherein the piston (10) of the control unit (21) is configured to cooperate in translation with the magnetic motor unit (11) by moving alternately along a central axis (OX) of the pump device (1), wherein the pump device (1) comprises a housing (108) made of non-magnetic material and adapted to surround the unit (21) of control,the housing (108) being further adapted to axially guide the piston (10) in a bore of said housing (108), wherein the magnetic motor unit (11) comprises a magnetic junction (111, 113) in the shape of a "C" adapted to accommodate a coil (102) and the housing (108), said magnetic junction (111, 113) being configured to concentrate a magnetic flux generated by the coil (102) around an armature (10a) of the piston (10) along the central axis (OX) when the piston (10) moves relative to the housing (108), the pump device (1) further comprising at least one of: a friction bearing (107) located at one end of the piston (10), a rear stop (114) configured to limit the axial displacement of the piston (10). Pump device (1) according to claim 1, wherein the control unit (21) is adapted to be mechanically connected, on the one hand, to the rear port (3) of the injector (1) and, on the other hand, to the magnetic motor unit (11), the reciprocating movement of the piston (10) relative to the magnetic motor unit (11) implementing controlled metering of the fluid. Pump device (1) according to any one of the preceding claims, further comprising a front stop (116) and a support (115) for said front stop (116), said front stop (116) and said support (115) being included in the control unit (21) and being positioned to control the stroke of the piston (10) along the central axis (OX). Pump device (1) according to claim 3, further comprising a spring (104) located downstream of the piston (10) and upstream of the front stop (116) and the support (115) of the front stop (116), said spring (104) being included in the control unit (21) and being positioned to ensure a return of the piston (10) to its initial position after at least one cycle of the reciprocating motion of the piston (10). Pump device (1) according to claim 4, wherein the spring (104) is dimensioned to fit into the support (115) of the front stop (116), the spring (104) being further adapted to allow controlled movement of the stroke of the piston (10) along the central axis (OX). Pump device (1) according to any one of the preceding claims, wherein the magnetic motor unit (11) is made of a magnetically soft material. Pump device (1) according to any one of the preceding claims, wherein the housing (108) includes an O-ring (109) located at one end of the housing (108) to ensure static sealing with the magnetic motor unit (11). Pump device (1) according to any one of the preceding claims, wherein the housing (108) includes a "V" shaped seal (110) adapted to compensate for misalignments between the piston (10) and said housing (108) along the axis (OX). Selective catalytic reduction (SCR) system for a diesel engine comprising a linear-acting pump device (1) for metering a fluid according to any one of the preceding claims and a pump unit (1) for said fluid, the SCR system further comprising the front housing (2) and the rear port (3), the pump device (1) being inserted into said pump unit (1) and said injector (1), the pump device (1) being further connected, at a first end, to the front housing (2) and, at a second end opposite said first end, to the rear port (3), and wherein: the magnetic motor unit (11) of the pump device (1) is connected to the front housing (2) and the control unit (21) of the pump device (1) is connected to the rear port (3).

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