ITTO20130735A1 - VARIABLE DISPLACEMENT PUMP WITH ELECTRIC CONTROL ADJUSTMENT AND ADJUSTMENT METHOD OF ITS DISPLACEMENT - Google Patents

Description

VARIABLE DISPLACEMENT PUMP WITH ELECTRIC CONTROL OF THE REGULATION AND METHOD OF ADJUSTMENT OF ITS DISPLACEMENT

Technical sector

The present invention refers to variable displacement pumps, and more particularly it concerns a rotary volumetric pump of the type in which the displacement variation is obtained thanks to the rotation of an eccentric ring (stator ring).

The invention also relates to a method for adjusting the displacement of this pump.

Preferably, but not exclusively, the invention finds application in a pump for the lubricating oil of a motor vehicle engine.

Known technique

It is known that in pumps for circulating lubricating oil under pressure in motor vehicle engines the capacity, and therefore the flow rate of the oil at the outlet, depends on the rotation speed of the engine and therefore the pumps are designed to provide sufficient flow to the low speeds, to guarantee lubrication even in these conditions. If the pump has a fixed geometry, at high rotation speed the flow rate is higher than necessary, so that a part of it needs to be discharged to limit the flow rate and pressure. Obviously the discharged volume has already been compressed and therefore there is a strong absorption of power with a consequent greater fuel consumption and greater stress on the components due to the high pressures constantly generated in the pump.

In order to obviate this drawback, it is known to equip the pumps with systems which allow the regulation of the flow rate at the different operating speeds of the vehicle, in particular through the regulation of the displacement. Various solutions are known for this purpose, specific for the particular type of pumping elements (external or internal gears, vanes ...).

A system often used in rotary pumps employs a stator ring with an internal cavity, eccentric with respect to the external surface, inside which the rotor rotates, in particular a vane rotor, which, in operating conditions of the pump, is eccentric with respect to the cavity. By rotating the stator ring by a certain angle, the relative eccentricity between the rotor and the cavity, and therefore the displacement, is varied between a maximum value and a minimum value, substantially tending to zero (operating condition in stall) . An elastic contrast element, suitably calibrated, allows rotation when a predetermined flow rate is reached and causes the pump to substantially deliver this predetermined flow rate when fully operational. An example is described in US 2685842.

Pumps with a double eccentric ring are also known, in which the displacement is varied by rotating the two rings relative to each other in the opposite direction. An example is described in US 4406599.

The evolution of these pumps and the spread of electronics in vehicle engines have led to displacement control systems controlled by the vehicle's electronic control unit based on the oil pressure, preferably detected downstream of the filter, and possibly other parameters. engine operation. In general, these are electro-hydraulic systems, in which the control unit controls solenoid valves which in turn control hydraulic actuators acting on the stator ring. For example, US 2011/0209682 describes a system in which a pump control module, forming part of the electronic control unit, controls, through a solenoid valve, the passage of pressurized oil towards one or the other of two chambers which apply the oil pressure at the stator ring. The application of the pressure of one or the other chamber corresponds to two different pressure / flow regimes of the pump.

In general, the presence of hydraulic actuators makes electro-hydraulic systems complex and expensive; moreover, with the engine off, it is not possible to change the displacement setting, because control pressure is not available.

An object of the present invention is to provide a variable displacement pump and a method for regulating the displacement of this pump which obviate the drawbacks of the known art.

Description of the Invention

According to the invention, this is achieved by the fact that the pump comprises a rotary actuator of the electromagnetic type integrated into the pump or combined with it, which is operated by an electronic system for detecting the operating conditions of the pump and is able to transmit the rotation movement to the stator ring.

Advantageously, the stator ring finds its seat in an eccentric cavity of an outer ring and the rotary actuator is able to transmit the rotation movement simultaneously to both rings, in such a way as to cause an equal and synchronous rotation in the opposite direction.

The invention also implements a method of adjusting the displacement of a rotary volumetric pump by rotating an eccentric stator ring inside which the rotor rotates, comprising the operations of:

- provide an electromagnetic rotary actuator integrated in the pump or combined with it;

- supplying the actuator with rotation commands corresponding to a desired rotation for the stator ring.

Preferably, the method also includes the operations of:

- providing an outer ring having an eccentric cavity in which the stator ring is seated; And

- rotate the two rings by the same angle simultaneously and in the opposite direction.

According to a further aspect of the invention, there is also provided a lubrication system for the engine of a motor vehicle in which the pump with adjustable displacement and the method of regulating the displacement presented above are used.

Brief Description of the Figures

Other characteristics and advantages of the invention will appear clearly from the following description of preferred embodiments, given by way of non-limiting example with reference to the attached drawings, in which:

- fig. 1 is a plan view of a first embodiment of the pump according to the invention, with the cover and the adjustment actuator removed and in the position of minimum displacement;

- fig. 2 is a view similar to fig. 1, in the position of maximum displacement;

- fig. 3 is a plan view, similar to fig. 2, showing the flow rate adjustment mechanism integrated in the lid;

- fig. 4 is a sectional view of the pump according to a plane passing through the line Y - Y of fig. 3;

Figures 5 and 6 are views similar to Figures 1 and 2, relating to a second embodiment of the pump according to the invention; And

- fig. 7 is a schematic block diagram of the displacement adjustment circuit. Description of Preferred Forms of Realization

With reference to Figures 1 - 4, a pump 1 according to the invention, in particular a vane pump, comprises a body 10 which has a substantially circular section cavity 11 in which a first movable ring 12 (outer ring) is arranged, which in turn has an axial cavity 13, also substantially circular in section, eccentric with respect to the cavity 11. A second mobile ring 42 (stator ring) is arranged in the cavity 13, which in turn has an axial cavity 43, also it has a substantially circular section, eccentric with respect to the cavity 13 and having a center O '. The two rings 12, 42 are adapted to rotate in the opposite direction with respect to each other by a certain angle to vary the displacement of the pump, as will be described later. Advantageously, the cavities 13, 43 have the same eccentricity. In the illustrated example, the cavity 11 is blind and is closed at one end by a lid 14 (fig. 4), which also closes the corresponding ends of the chambers 13 and 43.

In the cavity 43 there is in turn a rotor 15, integral with an actuation shaft 15a which causes it to rotate around a center O, for example in a clockwise direction, as indicated by the arrow F. The cavity 43 therefore constitutes the chamber of pumping. In a position of minimum displacement (represented in fig. 1), the rotor 15 and the cavity 43 are coaxial or substantially coaxial and, in a position of maximum displacement (represented in fig. 2), the centers O and O 'are on the same axis X - X and spaced apart from each other and the rotor 15 is substantially tangent to the lateral surface 43a of the cavity 43. In the context of the present description the term "coaxial or substantially coaxial" is used in the sense of indicating a minimum distance tending to zero between the centers O and O '.

Advantageously, the two eccentric rings 12, 42 are mounted so that, in the position of minimum displacement, the outer ring 12 is oriented with its minimum radial thickness in the upper part of the figure and the inner ring 42 is oriented with its minimum radial thickness in the lower part of the figure. In other words, the eccentricities of the respective cavities 13, 43 are offset by 180 °. Preferably, the chambers 13, 43 have the same eccentricity with respect to the external surfaces of the respective rings.

The rotor 15 has a series of vanes 16 sliding radially in respective radial slits. At an external end the vanes 16 are at a minimum distance from the lateral surface 43a of the cavity 43, while at the internal end they rest on guide or centering rings 17, mounted at the axial ends of the rotor 15 and able to maintain the minimum distance between the vanes 16 and the surface 43a in any condition of eccentricity. The centering rings 17 will also be coaxial or substantially coaxial with the rotor 15 in the position of minimum displacement.

On the bottom of the body 10, between the rotor 15 and the surface 43a, an intake chamber 18 is defined, communicating with an intake duct 20, and a delivery chamber 19, communicating with a delivery duct 21. The two chambers are substantially symmetrical with respect to a plane passing through the X - X axis and have the ideal timing for maximum volumetric efficiency, as is clear to the technician. Note that if the rotor direction of rotation were counterclockwise, the functions of the two chambers, and therefore of the respective ducts, would be interchanged.

To control the rotation of the rings 12, 42, toothed sectors 51 and 52 are formed on their facing surfaces, between which a toothed wheel 53 is interposed having a shaft 54 integral with an actuator 50 (fig. 4) which causes its rotation . The rings 12, 42 therefore rotate in the opposite direction and are synchronous with each other

Preferably the actuator 50 is of the electromagnetic type. It can be a rotary actuator, for example a micro-stepping motor, integrated in the pump 1 or combined with it (for example interfaced through the internal / external partition of the motor sump), or an actuator with linear movement, combined with a suitable escapement ratchet to transform motion into rotary.

The actuator 50 is controlled by the electronic control unit of the vehicle, which manages the displacement variation in a closed loop (ie with feedback), increasing or reducing it according to the needs of the thermal engine and its accessories. The variation is independent of the pressures upstream and downstream of the oil filter.

The shaft 54 is guided in a support 40 obtained in the cover 14 or in the body 10. The toothed sectors 51, 52, during their rotation, develop according to a profile defined by the involute of the toothing of the wheel 53, which vice versa rotates on the its fixed axis. If the eccentricities are the same, the relative rotation of the rings causes a translation of the center O 'of the pumping chamber 43 along the X - X axis. This makes the geometry of the pumping chamber 43 perfectly symmetrical in all displacement conditions. , and makes constant the ratio between the rotation of the toothed wheel 53 and the variation of the displacement due to the translation of the axis of the chamber 43.

In the illustrated embodiment, the wheel 53 cooperates with a member 34 for contrasting the rotation of the rings 12 and 42, in particular a flat spiral spring, preloaded so as to prevent rotation of the rings until the torque applied by the actuator 50 is below a predetermined threshold. The spiral spring 34 is arranged in a container 33 which, in the illustrated embodiment example, is fixed to the cover 14. The inner end part of the spring 34 is configured so as to couple to the end part of the shaft 54 of the wheel 53, while the outer end part is hooked to the inner wall of the container 33, which can be rotated, for example using a torque wrench, to adjust the preload of the spring 34. A ring nut 55 allows the container 33 to be locked in the desired calibration position, regardless of the construction tolerances of the entire mechanism. Between the container 33 and the lid 14 there is also a sealing gasket 56 which insulates the internal chamber of the container from the outside. A drain puts this chamber in communication with the suction chamber 18, for the purposes illustrated below.

It will be noted that, during the adjustment rotation, the spiral spring 34, thanks to the negligible variation of the twisting torque and the transmission ratio of the gear mechanism, will negligibly modify its own antagonist torque to the hydraulic one. In the preferred case where the actuator 50 is a stepping motor, the spring 34 can help to ensure that the magnetic resistance torque between one step and the next is sufficient to maintain the position of the rings 12, 42 in the absence excitation of the motor (energy saving). Furthermore, due to a diametrically opposite effect, the spring 34 could contribute to maintaining a maximum displacement in the moment in which an electrical failure occurs.

The rings 12 and 42, as well as the centering rings 17, the rotor 15 and the wheel 53 are preferably obtained by molding and / or sintering of metal powders, with possible finishing processes on some limited areas, according to the dictates of the art. . In particular, the axial thicknesses will be finished. The body 10 and the lid 14 can be obtained by molding either an aluminum alloy or a thermoplastic and / or thermosetting resin. Advantageously, the spring 34 can be made of bimetallic material, so that its characteristic can vary as a function of the working temperature.

Figures 5, 6 show a second embodiment of the pump according to the invention, indicated with 101. Elements functionally identical to those already described with reference to Figures 1 - 4 are indicated with the same reference numbers, increased by 100 The pump 101 differs from the pump 1 in that the outer ring 12 is missing, and the actuator 150 therefore acts, through the wheel 153, on the stator ring 142 only. Furthermore, the rotor 115 rotates in an anticlockwise direction (arrow F '). With this arrangement, the translation of the center O 'of the chamber 143 takes place along a non-rectilinear trajectory. Apart from this, the structure is identical to that of pump 1 and it is not necessary to describe it again.

Fig. 7 illustrates a schematic block diagram of the adjustment of the displacement of the pumps 1, 101. The dashed line indicates the mechanical control of the pump by the actuator 50 and therefore corresponds to the toothed wheel 53, 153 of the previous figures. The dotted and dashed line 60 indicates the lubrication circuit that carries the oil from the pump 1 to the engine and to the various accessories, indicated as a whole with 61. 62 indicates the electronic control unit of the vehicle, which receives signals from sensors indicated in complex with 63 and controls the actuator 50, possibly by means of a digital-analog converter, not shown. The solid lines indicate the path of the incoming / outgoing electrical signals in / from the control unit 62 and the dotted lines indicate the detection of the operating parameters of the motor 61, of the pump 1, of the lubrication circuit 60 and possibly of the actuator 50 by of the sensors 63. The parameters on which the regulation of the flow rate of the lubrication pump of the engine of a motor vehicle can depend are well known to the technician and are not of interest to the invention. A more detailed description is provided in US 2011/0209682.

The operation of the pump described is as follows.

Considering first the pump 1, in rest conditions this is in the maximum displacement arrangement illustrated in fig. 2: as mentioned, the center of rotation O of the rotor 15 is offset with respect to the center O 'of the cavity 43 of the eccentric ring 42 and the rotor 15 is located in proximity to the wall 43a thereof. When the pump 1 is started, the clockwise rotation of the rotor 15 will cause an oil flow through the chamber 19 and the relative delivery duct 21 and, at the same time, from the chamber 18 and the relative suction duct 20, an equivalent will be recalled volume. With the increase in rotation speed and flow rate, the engine lubrication system, opposing resistance to the increasing flow, will raise the pressure. The delivery pressure or the pressure downstream of the oil filter are detected by the appropriate sensors 63 and communicated to the control unit 62, which will rotate the actuator 50. This will in turn generate a rotation torque which, by means of the wheel 53 and once the setting value of the antagonist spring 34 has been reached, it will rotate the rings 12 and 42 by the same angle in the opposite direction. If, as it was supposed, the eccentricities of the cavities 13, 43 with respect to the external surfaces of the respective rings are equal, the rotation of the ring 42 will cause a rectilinear translation towards the right of the center O ', proportional to the amount of rotation, reducing proportionally the eccentricity between the rotor 15 and the cavity 43 and consequently the displacement of the pump and stabilizing the pressure at the set value. When the parameters such as speed, fluidity / temperature of the fluid, the "permeability" of the engine (in the sense of the quantity of oil used by the engine), etc., detected by the sensors 63 vary, this pressure will be maintained and controlled through the variation eccentricity and therefore the displacement.

When, depending on the various operating parameters of the engine, it is desired to pass to a lower pressure value, consequently reducing the absorbed power, the control unit 62 will generate a special command for the actuator 50 in order to further reduce the displacement.

The rotation of the rings can continue until reaching the position of fig. 1, in which the centers O and O 'coincide and the vanes 16 and the centering rings 17 rotate with the rotor without changing the relative radial position: consequently the displacement is zero and the pump is stalled. Note that this position can be assumed when a hydraulic blockage of the discharge pressure is near. In construction practice, it is preferably provided that a minimum displacement is maintained, protecting the pump with a maximum pressure valve.

The operation of the pump 101 is quite similar, with the modifications due to the presence of the stator ring 42 alone.

An important parameter in managing the flow rate / pressure of an oil pump for thermal engines is the temperature, with the increase of which the oil becomes more fluid and the permeability of the engine increases. In proportion, the pump displacement should increase accordingly. This can be favored if the counter spring load increases. To achieve this, the flat spiral spring 34 can be made of a bimetallic material such that the temperature gives an increase in the rigidity and therefore in the antagonist torque. To obtain the variation of the stiffness, the small lubrication flow rate of the shaft 54 of the wheel 53 can be exploited: the oil, after having licked the container 33 of the spring 34 and having transmitted the temperature to the spring itself, finds free outlet towards the suction chamber through the drainage provided in chamber 57.

The invention effectively achieves the desired purposes.

The use of an electromagnetic actuator, controlled directly by the electronic control unit of the vehicle, allows to eliminate the hydraulic actuators of the known art and the necessary connections to the lubrication circuit, and makes the system less bulky, simpler and more reliable and less expensive. Furthermore, the elimination of the hydraulic actuators makes it possible to modify the predisposition of the displacement even with the thermal engine off, since no control pressure is necessary. This is particularly advantageous for vehicles with the "stop and go" function because it allows for example to increase the displacement between stopping the heat engine and starting, to restart the engine with good lubrication.

Furthermore, in both embodiments, given the respective direction of rotation of the rotor, in the event of an electrical failure causing the deactivation of the actuator 50, the hydraulic torque of the pump causes the rotation of the stator ring, or of the stator ring. and of the outer ring, towards the condition of maximum displacement. As mentioned, this action can be favored by the spring 34. In the event of other failures, the minimum displacement is guaranteed and the electronic management, detecting low lubrication pressures, will place the control unit 62 in the "recovery" function of the vehicle.

It is clear that what has been described is given only by way of non-limiting example and that variations and modifications are possible without departing from the scope of the invention.

For example, even if in the embodiment illustrated the shaft 15a of the rotor 15 is guided by the body 10 while the spiral spring 34 with the calibration means constituted by the container 33 and the ring nut 55 are housed in the cover 14, the arrangement could be inverted. , or the spring and the calibration means could also be housed in the body 10.

Furthermore, the spring 34 may not be a bimetallic spring and, at least in the embodiments in which the actuator 50 is a step-by-step electric motor, it may also be missing, the only magnetic resistance pair between one step and another, maintaining the position of the rings 12, 42 in the absence of excitation of the motor.

Finally, even if the invention has been described in detail with reference to a pump for the lubricating oil of a motor vehicle engine, it can be applied in any volumetric pump for transporting fluid from a first to a second environment of work, in which it is convenient to reduce the flow rate as the pump speed increases.

Claims (12)

Claims 1. Variable displacement rotary volumetric pump for fluids, comprising a rotor (15) adapted to rotate in an eccentric cavity (43) of a stator ring (42), adapted in turn to be made to rotate within a predetermined angular interval, at vary the operating conditions of the pump (1; 101) and upon command of a system (62, 63) for detecting these conditions, to vary a relative eccentricity between the cavity (43) and the rotor (15) and therefore the displacement of the pump, characterized in that the pump (1; 101) also comprises an electromagnetic actuator (50) integrated in the pump or combined with it, operated by said detection system (62, 63) and capable of generating a rotary movement and to transmit it to the stator ring (42). 2. Pump according to claim 1, wherein the stator ring (42) has on an external surface a toothed sector (52) with which a toothed wheel (53) operated by the actuator (50) is engaged and which develops according to a profile defined by an involute of the toothing of the wheel (53). 3. Pump according to claim 1 or 2, in which the stator ring (42) is housed in an eccentric cavity (13) of an outer ring (12) and said actuator (50) is able to transmit the rotary movement to both rings (12, 42 ) in such a way as to cause an equal and synchronous rotation in the opposite direction. 4. Pump according to rev. 3, in which the eccentric cavities (13, 43) have the same eccentricity and, in a condition of minimum displacement, are arranged with the eccentricities out of phase by 180 °. 5. Pump according to rev. 3 or 4, in which respective toothed sectors (51, 52) are obtained on facing surfaces of the outer ring (12) and of the stator ring (42), with which a toothed wheel (53) operated by the actuator (50) and which develop according to a profile defined by an involute of the toothing of the wheel (53), so that during the rotation of the rings (12, 42) a center (O ') of the stator ring cavity moves according to a straight trajectory. Pump according to any one of claims 2 to 5, wherein the toothed wheel (53) is adapted to cooperate with a member (34) for contrasting the rotation of the outer ring (12), consisting of a flat spiral spring constrained at one end to a shaft (54) of the toothed wheel and at the other to an element (33) integral with the body and associated with calibration means (33, 55) able to establish a desired speed value for the displacement of the pump (1), and in which the flat spiral spring (34) is made of a bimetallic material and has a temperature dependent characteristic. Pump according to any one of the preceding claims, wherein the actuator (50) is a step by step micromotor or an actuator with linear motion, combined with escapement ratchet gear to transform its motion into a rotary motion. Pump according to any one of the preceding claims, wherein the pump (1; 101) is a pump for a lubrication circuit (60) of a motor vehicle engine (61). 9 Method for adjusting the displacement of a rotary volumetric pump (1, 101) of the type comprising a rotor (15) adapted to rotate in an eccentric cavity (43) of a stator ring (42), the method comprising the operation of rotate the stator ring (42) within a predetermined angular interval to vary the eccentricity between the cavity (43) and the rotor (15) as the operating conditions of the pump (1; 101) vary, and being characterized in that it comprises in addition, the operations of: - providing an electromagnetic type actuator (50) integrated in the pump or combined with it and able to transmit a rotary movement to the stator ring (42); - supplying the actuator (50) with commands corresponding to a desired rotation for the stator ring (42). 10. Method rev.9, also including the operations of: - providing an outer ring (12) having an eccentric cavity (13) in which the stator ring (42) is housed; And - rotate the two rings (12; 42) by the same angle simultaneously and in the opposite direction. 11. Method according to rev. 9 or 10, to adjust the displacement of a lubricating oil pump for a motor vehicle engine. Motor vehicle engine (61) lubrication system, comprising a pump (1; 101) according to any one of claims 1 to 8.