EP3821158A1

EP3821158A1 - On/off solenoid valve providing two levels of mechanical pressure regulation

Info

Publication number: EP3821158A1
Application number: EP19749381.0A
Authority: EP
Inventors: Frédéric Daniel Bernard PINEAU; Stéphane Pascal PEROTTO
Original assignee: Bontaz Centre R&D SAS
Current assignee: Bontaz Centre SA
Priority date: 2018-08-10
Filing date: 2019-08-09
Publication date: 2021-05-19
Also published as: CN112654808B; FR3084922B1; JP2021534356A; FR3084922A1; US20210310571A1; BR112021002438A2; KR20210042342A; CN112654808A; WO2020030802A1; US11879555B2

Abstract

The invention concerns a solenoid valve device (10) with a pressure-responsive slide mechanism, comprising: - a body (2) comprising at least three channels (30 (P), 32 (A), 34(T)) for flow of a liquid; - means forming a slide (4) that can be moved in said body (2) by a pressurised fluid, between a position with fluid communication between a first and a second channel among said three flow channels, and a position with fluid communication between said second channel and the third channel; - means (14, 15), for selecting an activation threshold for movement of the slide, among at least one first (Ph) and at least one second pressure threshold (Pb, Pb<Ph); and - means (6, 12, 16, 22), for regulating at least said activation thresholds (Ph, Pb) of the slide.

Description

ELECTROVALVE ON / OFF PROVIDING 2 LEVELS OF MECHANICAL REGULATION

PRESSURE

DESCRIPTION

TECHNICAL AREA AND PRIOR ART

The invention relates to a solenoid valve, for example of the ON / OFF type, offering 2 levels of mechanical pressure regulation, these being moreover adjustable, independently of one another.

The present invention applies in particular to the control of oil pumps of vehicle engines on which it is installed directly or indirectly.

There are known, in certain applications, ON / OFF solenoid valves with slide mechanism not reactive to pressure, effectively offering no threshold for mechanical pressure regulation, or ON / OFF solenoid valves with drawer mechanism reactive to pressure pressure at 2 regulation thresholds, none or only one of which is adjustable.

Also known are valves with a pressure-responsive slide mechanism but with a single threshold for mechanical pressure regulation.

There are also known proportional solenoid valves with a pressure-responsive slide mechanism, none or only one threshold of which is adjustable. These solenoid valves also require an electrical control system capable of generating a variable current (for example PWM) and possibly equipment useful for managing a control loop.

We are looking for a device of the ON / OFF solenoid valve type, with two adjustable regulation thresholds, in particular for applications of oil pumps, in particular in the automotive field.

BRIEF DESCRIPTION OF THE INVENTION

The invention firstly relates to a device of the solenoid valve type, with a pressure-responsive slide mechanism comprising: - a body comprising at least 3 channels for the flow of a liquid;

- means forming a drawer, which can be moved in said body by a pressurized fluid, between a first position, in which there is fluid communication between a first channel and a second channel among said 3 flow paths, and a second position in which there is fluid communication between said second path and the 3 ^rd channel;

- Means for selecting a pressure threshold for activating a movement of said slide, from at least a first threshold (Ph) and at least a second pressure threshold (Pb, with Pb <Ph);

- Means for adjusting at least said first threshold (Ph) and at least said second threshold (Pb) for activating said drawer.

Thus it is not only possible, using means which may be of the electromagnetic type, to select an activation pressure threshold of said drawer from at least a first threshold (Ph) and at least a second threshold (Pb, with Pb < Ph) of activation pressure of said slide, but also to adjust these thresholds. After selecting the pressure threshold, the slide can then be moved by the fluid under pressure, if this fluid pressure is greater than the selected activation pressure threshold.

The invention makes it possible, in a context of large-scale production, to minimize the dispersion over the value of 2 levels of mechanical regulation by eliminating, thanks to the possible adjustment of the 2 thresholds, the dispersion of the dimensions of the components in the set constituted.

Such a device can be used as a solenoid valve installed in a pump type system, for example an oil pump, for example also of a heat engine, in particular in a rolling vehicle, in order to control it.

According to one embodiment, a device according to the invention comprises:

- a first spring, which forces the drawer into the first position;

- an electromagnetic actuator;

- a movable core, which can be moved inside the device, using said electromagnetic actuator, between a deactivated position and an activated position (in one direction or the other), to select said pressure threshold activation of said drawer, before activation of the latter by the pressurized fluid (if this pressure is greater than said selected activation pressure threshold).

The invention then makes it possible to offer at least 2 levels of mechanical regulation of the selected pressure by activating and deactivating an electromagnetic actuator, before actuation of the drawer between the ^1st and the ^2nd position by fluid under pressure.

According to a particular embodiment of a device according to the invention, the means for adjusting one of the activation pressure thresholds may include means for adjusting a longitudinal force of support of the first spring on the slide.

For example, these means include a stop against which the spring bears, and a needle, inserted in the movable core over a length L.

This length L can be adjustable and / or the device further comprises means for adjusting a pressure or a deformation of said stop.

According to a particular embodiment of a device according to the invention, the means for adjusting the other activation pressure threshold of said drawer include means for adjusting the deactivated position of the movable core inside the device.

Means for adjusting the deactivated position of said movable core may include an element which can be adjusted against said movable core.

For example, such a device comprises a fixed core and a second spring, disposed between the fixed core and the movable core, a support of the element on said movable core more or less compressing this second spring.

Said adjustable support element against said movable core may include an end plug of the device, the support of which is adjusted for example by screwing.

Such a device may comprise a fixed core and a second spring, disposed between the fixed core and the movable core, a support, adjusted for example by screwing, of the fixed core on said movable core compressing more or less this second spring.

In a device according to the invention, the difference Ph - Pb, between the two levels of regulating pressure is preferably between 1 bar and 7 bar. In one embodiment, a device according to the invention may also comprise means for supplying the electromagnetic actuator capable of generating a variable current, for example of the PWM type.

A device according to the invention can be of the type generating a thrust movement when the electromagnetic actuator is activated.

As a variant, a device according to the invention can be of the type generating a traction movement when the electromagnetic actuator is activated.

The invention also relates to a hydraulic circuit, comprising a device of the solenoid valve type according to the invention.

The invention also relates to a pump, for example an oil pump, comprising said pump and a device of the solenoid valve type according to the invention.

The invention also relates to a method of operating a device of the solenoid valve type according to the invention, in which:

- if the activation pressure threshold of said drawer is the first pressure threshold (Ph), a fluid under pressure P is injected to move said drawer, from the first position to the second position, the pressure P being greater than the first threshold (Ph) pressure;

- If the activation pressure threshold of said drawer is the second pressure threshold (Pb), a pressurized fluid P is injected to move said drawer, from the first position to the second position, the pressure P being greater than the second threshold (Pb) pressure.

- if the activation pressure threshold of said drawer is the first pressure threshold (Ph), the movable core is moved inside the device, using said electromagnetic actuator, to adjust the activation pressure at the second activation pressure threshold (Pb) of said drawer;

- A fluid under pressure P is injected to move said slide, from the first position to the second position, the pressure P being greater than the second pressure threshold (Pb). The invention also relates to a method of operating a device of the solenoid valve type according to the invention, in which:

- if the activation pressure threshold of said drawer is the second pressure threshold (Pb), the movable core is moved inside the device, using said electromagnetic actuator, to adjust the activation pressure at the first activation pressure threshold (Ph) of said drawer;

- A fluid under pressure P is injected to move said slide, from the first position to the second position, the pressure P being greater than the first pressure threshold (Pb).

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention will now be described with reference to the accompanying drawings in which:

FIG. 1 represents a particular embodiment of a device according to the invention, for a solenoid generating a thrust movement during activation,

FIGS. 2A to 2C represent particular aspects of an embodiment of a device according to the invention,

FIG. 3 represents a diagram of the evolution of the pressure for an embodiment of a device according to the invention,

FIGS. 4A - 5B represent the application of an embodiment of a device according to the invention to an oil pump,

FIG. 6 represents another particular embodiment of a device according to the invention, for a solenoid generating a traction movement during activation,

- Figure 7 shows a pressure evolution diagram of an embodiment of the other particular embodiment of a device according to the invention.

In the figures, similar or identical technical elements are designated by the same reference numbers.

DETAILED DESCRIPTION OF EMBODIMENTS The invention makes it possible to control the opening and closing of the valve of a solenoid valve with two different pressure thresholds Pb (low pressure), Ph (high pressure). Each of these thresholds is defined by a state of compression of a spring applied to the drawer: in a first state of compression, the spring exerts a first force on the drawer, requiring that the pressure in the drawer (in the example described here - below: in the first channel thereof) exceeds the pressure threshold Pb to establish the desired fluid connection (in the example described below: between the first channel and the second channel); in a second state of compression, the spring exerts a force on the slide requiring that the pressure in the slide (in the example described below: in the first way) exceeds the pressure threshold Ph to establish the desired fluid connection ( in the example described below: between the first channel and the second channel) (Ph> Pb). Means make it possible to adjust (or fix) these two pressure thresholds.

An example of an embodiment of a solenoid valve 10 according to the invention is shown in FIG. 1.

This embodiment relates to a solenoid valve whose pressure threshold is activated (or which activates the passage between a high pressure threshold and a low pressure threshold) using an electromagnetic actuator, for example a solenoid, "ON / OFF ”(Ie operating between an activation state and a deactivation state); a thrust can be generated by activation of the pressure threshold by the actuator.

In the following, the use of a solenoid will be described, but the invention also covers the case of the implementation of other types of electromagnetic actuators.

Using the solenoid, a pressure threshold is selected (from at least a low pressure threshold and a high pressure threshold) or the passage between the high pressure threshold and the low pressure threshold is activated; but, once the pressure threshold has been chosen, the movement of the slide valve then depends on the pressure, with respect to said threshold, of the fluid introduced into the valve.

In this example, the solenoid valve 10 extends between a first end 10i and a second end 10 _2, longitudinally along an axis AA '. It comprises a main body 2, which extends longitudinally along this axis AA '.

In the example shown, this body comprises lateral supply channels 30 ("P" channel, or inlet channel), 32 ("A" channel, or outlet channel), and a supply channel for end 34 ("T" channel, or vent). Through these supply routes, a fluid, for example oil, can circulate. Other geometries for distributing the different channels can be produced in the context of the invention: for example the channel P (inlet) can be at the end of the valve, while the channels "T" and "A" are arranged laterally ; alternatively, the channels "P" and "A" of Figures 1 and 6 can be reversed; in another variant, channel A (outlet) can be at the end, while channels "P" and "T" are arranged laterally. The following explanations are given for the configuration shown in FIG. 1, but the invention also applies to other possible configurations, in particular those mentioned above.

The body 2 is hollow internally: it has an internal cylindrical cavity 2c in which a drawer 4 can move between 2 positions, in order to establish a fluidic or hydraulic communication (which means that a fluid can then circulate), either between two lateral supply channels 30, 32, or between the lateral supply channel 32 and an end channel 34. In FIG. 1, the fluid communication between the channels 30 and 32 is closed, the fluid pressure being less than Pb (for example, all channels are at atmospheric pressure).

The cylindrical cavity 2c is extended by another cylindrical cavity 13c, delimited by a support carcass 13, which also defines a compartment 20 which can accommodate a solenoid 15 disposed around this cavity 13c. Means for feeding the latter are provided. When the solenoid is powered by a current, a movable core 14, which has the magnetic properties to interact with the field generated when the solenoid is traversed by a current, is moved in this cavity 13c.

A spring 8 is positioned between a stop 12, arranged at the first end 10i of the device and of the main body 2, on the side of the end track 34, and a bearing surface of the drawer 4. The stop allows passage around from her for a flow of the fluid towards the channel 34; for example, the end of the cylindrical cavity 2c can be extended by a part of conical shape, flared towards the outside. The width or diameter of the stop 12 can be limited to what is sufficient for the support of the spring. The surfaces against which this spring is supported are perpendicular or substantially perpendicular to the axis AA '. This spring exerts a longitudinal force along this axis AA '. This spring pushes the drawer towards the second end 10 ₂ . A fluid introduced into the valve will allow this action of the spring to be countered and the drawer to be tilted between its 2 positions, when the pressure of this fluid becomes greater than the pressure exerted by the spring on the drawer.

Means will allow the pressure exerted by the spring 8 on the slide 4 to be selected between at least two different levels, Pb and Ph; according to the value Pb, respectively Ph, used, a fluid introduced into the valve will make it possible to struggle to make the slide switch between its 2 positions, when the pressure of this fluid becomes greater than the pressure Pb, respectively Ph.

In the example shown, the drawer 4 has a central cylindrical part 41 (see FIG. 2A), of external diameter less than the diameter of the internal cylindrical cavity of the main body 2. Thus, an internal chamber or cavity 36 is formed between the surface exterior of drawer 4 and the interior surface of the main body. This central cylindrical part 41 of the drawer is extended by two end parts 42, 43, which are also substantially cylindrical, with an outside diameter substantially equal to the inside diameter of the main body 2, in which they can be guided in displacement in translation. One of these two end parts 42 makes it possible to partially close off one of the supply channels of the valve. Longitudinally, the internal cavity 36 is delimited by end surfaces 42i, respectively 43i, of the end part 42, respectively 43. In fact, the end parts 42, 43 may be such that the surfaces offered by these parts of a fluid introduced into the cavity 36 are different from each other, the surface of the end part 42 subjected to this fluid being greater than the surface of the end part 43, this in order to promote movement in the desired direction (to the left in Figure 1). The drawer can for example be in an initial position in which the fluid communication between the tracks 30 and 32 is closed by the end part 42 of the drawer, the latter being arranged so as to partially close the track 32, the cavity 36 being opposite track 30. As a variant, the end part 42 can be arranged between tracks 30 and 32, but this implies a longer stroke of the slide to establish communication between tracks 30 and 32. Fluid communication is then established between the supply channels 32 and 34, between which a fluid, introduced by the supply channel 32, can flow. More generally, the valve makes it possible to establish alternately a fluidic or hydraulic connection between the tracks 30 and 32 then between the tracks 32 and 34 or vice versa. More generally still, the valve makes it possible to establish alternately a fluidic or hydraulic connection first between the tracks “P” and “A” then between the tracks “A” and “T” or vice versa, and this whatever the distribution channels "A", "P" and "T".

When a sufficient pressure P (greater than that exerted by the spring 8 on the drawer 4) is exerted by this fluid in this cavity 36, therefore also on the drawer 4, the latter can be moved, to the left in FIG. 1 , by compressing the spring 8. This leads to a release of the fluid communication between the supply channels 30 and 32 and to a closure of the fluid communication between the supply channels 32 and 34. The fluid, introduced into the cavity 36 via the supply channel 30, can then flow towards the channel 32.

In the embodiment illustrated here, a needle 6, of substantially cylindrical longitudinal shape, has a first end positioned on the side of the first end 10i (or of the end track 34) and a second end inserted in the movable core 14 , which moves under the action of the solenoid 15. This needle is integral with the stop 12.

The needle 6 passes through a fixed core 26 (in which it can slide) and penetrates, over a length L (FIG. 2A), into the movable core 14, in which its second end is maintained. In other words, along the axis AA ', starting from the first end 10i and going towards the second end 10 ₂ of the solenoid valve, are successively disposed the needle 6, the fixed core 26, crossed by the needle and then the core mobile 14, into which the needle is inserted. The greater the length L of insertion of the needle into the movable core, the more the spring 8 is compressed and the higher one of the pressure thresholds (here the threshold Pb). In other words, the low pressure Pb is adjusted (or fixed) by more or less deep insertion of the needle 6 in the movable core.

As a variant, in order to adjust the low pressure Pb, it is possible to apply a variable load or stress to the spring 8, more precisely at the end of the latter located on the side of the first end 10i of the valve. This variable load or stress can be obtained by the plastic deformation of a metallic element applied to the end of the spring, this element possibly being the stop 12. This variant is illustrated in FIG. 2C.

The setting of the pressure threshold Ph will now be described.

A spring 16 applies pressure, on the one hand to a surface 26i of the fixed core 26 and, on the other hand, to a bearing surface 14i of the movable core 14 (FIGS. 2A, 2B). Each of these bearing surfaces is perpendicular or substantially perpendicular to the axis AA '. This spring 16 exerts a longitudinal force along this axis AA 'while tending to push the movable core towards the second end 10 ₂ . Inside the valve, the movable core 14 is positioned between, on the one hand, the end of this spring 16 which bears on the bearing surface 14i and, on the other hand, an end element 22 , also called plug, against which the movable core is pressed. The position of this end element 22 can be adjusted, for example by screwing in a fixed part of the solenoid valve, for example in an overmolded part 39, as illustrated in FIGS. 1 and 6.

This setting fixes the value of the high pressure Ph.

In other words, the position of the movable core 14 at rest (not activated by the solenoid) results from the positioning of the element 22 and the action of the spring 16. By introducing the movable core 14 more (or less) deep into the valve , the position of the needle 6 corresponding to the high pressure Ph is adjusted (a position of the movable core at rest deeper in the valve makes it possible to reduce the pressure exerted by the spring 8 on the slide). When the appropriate adjustment is made, the element 22 can be covered by a portion 24 forming a cover and which can be fixed to the fixed part of the solenoid valve (for example again the molded part 39), so that the setting obtained is not modified.

Thus, there is a first means for adjusting (or fixing) the low pressure Pb, and a second means for adjusting (or fixing) the high pressure Ph, these 2 means being independent of one the other, even if the mobile core is implemented in these 2 means.

The movable core 14 can be moved, in one direction or the other along the axis AA ', by variation of the current which feeds the solenoid, which makes it possible to more or less compress the spring 8 and, thus, select the pressure threshold (Ph or Pb) to apply in the chamber 36 to move the slide 4 and therefore to connect the tracks 30 and 32 or 32 and 34 from the fluidic or hydraulic point of view.

The length over which the movable core is moved is shorter than that over which the movable slide 4 is displaced for the operation of the valve: in fact, the purpose of the displacement of the movable core 14 is to vary the pressure P to be applied in the cavity 36 for moving the slide 4, between the pressure Ph called "high" and the pressure Pb called "low" (with Pb <Ph).

In other words :

- in a first operating state of the device (in the case of FIG. 1, this state is that in which the solenoid is powered by a current, the movable core 14 is positioned so that the pressure P to be applied in the chamber 36 is at least equal to Pb to allow the fluid connection of the tracks 30 and 32 by the movement of the slide;

- in a second operating state of the device (in the case of FIG. 1, this state is that in which the solenoid is not supplied by a current), the movable core is positioned so that the pressure P at apply in the chamber 36 is at least equal to Ph to allow the fluid connection of the tracks 30 and 32 by moving the drawer.

An example of the operation of such a device is as follows.

When the solenoid is not supplied by a current, the pressure threshold is Ph. The pressure P of the fluid entering via the supply channel acts mechanically on slide 4, tending to move it against the effect of spring 8. When this pressure P becomes greater than Ph, the fluid or hydraulic connection between tracks 32 and 34, first open, is closed in favor of a fluidic or hydraulic connection between tracks 30 and 32.

When the solenoid is supplied by a current, the pressure threshold is Pb. The pressure P of the fluid entering via the supply channel 30 acts mechanically on the slide, tending to move it against the effect of the spring 8, reduced by l 'force resulting from the displacement of the assembly comprising the movable core 14, the needle and the stop. When the pressure P becomes greater than Pb (Pb <Ph), the fluid or hydraulic communication between the channels 32 and 34 is closed in favor of a fluid connection between the supply channels 30 and 32.

As explained above, the adjustment of the pressure Pb results from the more or less deep insertion of the assembly comprising the needle 6 in the mobile core 14, consequently forming a rigid needle - stop - mobile core assembly.

The pressure adjustment Ph results from the positioning of the mobile core (in the position not activated by the solenoid), by means of the more or less deep insertion of the element 22 which defines a fixed stroke value of the mobile core.

In the various cases described above, the state in which the solenoid is supplied (respectively: not supplied) by a current is associated with the threshold Pb (respectively: Ph).

It will be the opposite in the case described below in connection with FIG. 6. This opposite case would also be that of a solenoid valve operating on the same principle as that of FIG. 1, but with a drawer going from the left towards the right (in FIG. 1) under the effect of the pressure P which would be introduced on track 32, and not on track 30. Track “A” would then be track 30, and track “T” would still be the track 34, or in body feet, on the side of the solenoid.

In Figures 1 and 6, references 23 and 33 denote, respectively, electrical connection means (cable for example) and a fixing lug. FIG. 3 illustrates the operation of a valve according to the invention, as described above. It represents the evolution of the pressure P32 in the supply path 32 as a function of the pressure P30 in the supply path 30.

On the abscissa axis, the pressure thresholds Pb and Ph are represented (with their respective adjustment ranges indicated by double arrows in dashed lines).

When the solenoid is not activated (curve I), the threshold is defined by the pressure Ph. For a pressure in the supply channel 30, less than this pressure Ph, the communication between the supply channels 30 and 32 is closed.

For a pressure in the supply channel 30, greater than this pressure Ph, the communication between the supply channels 30 and 32 is open, which explains the increasing part of the curve I for P> Ph (the pressure in the feed path 32 approaches that in the feed path 30).

When the solenoid is activated (curve II), the threshold is defined by the pressure Pb. For a pressure in the supply channel 30, lower than this pressure Pb, the communication between the supply channels 30 and 32 is closed .

For a pressure, in the supply path 30, greater than this pressure Pb, the communication between the supply paths 30 and 32 is open, which explains the increasing part of the curve II for P> Pb (again, the pressure in the supply path 32 approximates that in the supply path 30).

FIGS. 4A - 5B represent an application of a valve according to the invention, as described above, to a hydraulic pump 50, preferably a variable geometry pump such as a vane pump or a gear pump. The fluid used is then oil.

In a first state, corresponding to FIG. 4A, the solenoid is not supplied with current and the pressure P inside the chamber 36 is less than the pressure threshold Ph. There is then no fluid communication or hydraulic between tracks 30 and 32, both connected to pump 50, but there is fluidic or hydraulic communication between tracks 32 and 34 releasing the circulation of oil from a chamber (of pump 50) connected to track 32 to track 34. In a second state, corresponding to FIG. 4B, the solenoid is still not supplied with current and the pressure P inside the chamber 36 is greater than the pressure threshold Ph. There is then fluidic or hydraulic communication between tracks 30 and 32, both connected to pump 50, but no more fluid or hydraulic communication between tracks 32 and 34. This then allows the oil supply to the chamber, already mentioned above and connected to this track 32.

In a third state, corresponding to FIG. 5A, the solenoid is supplied with current and the pressure P inside the chamber 36 is less than the pressure threshold Pb. There is then no fluid or hydraulic communication between tracks 30 and 32, both connected to pump 50, but there is fluid or hydraulic communication between tracks 32 and 34 releasing the circulation of oil from the chamber of the pump connected to track 32 to track 34.

In a fourth state, corresponding to FIG. 5B, the solenoid is always supplied with current and the pressure P inside the chamber 36 is greater than the pressure threshold Pb. There is then fluidic or hydraulic communication between the tracks 30 and 32, both connected to the pump 50, but no more fluid or hydraulic communication between the channels 32 and 34 This then allows the oil supply to the chamber, already mentioned above and connected to this channel 32.

The different states above can be obtained chronologically in the order described above, or in another order.

Another example of an embodiment of a solenoid valve 100 according to the invention is shown in FIG. 6.

Numerical references identical to those of the preceding figures designate identical or corresponding technical elements therein.

This embodiment relates to a solenoid valve whose pressure threshold is activated (or which activates the passage between a low pressure threshold and a high pressure threshold) using an electromagnetic actuator, for example an “ON / OFF” solenoid. (i.e. operating between an activation state and a deactivation state); traction can be generated by activation of the pressure threshold by the actuator. In this embodiment, the presence of a washer 37 is noted, which represents the end of travel of the movable core, to the left. This washer is, or is not, part of the main body.

In this embodiment, the needle 6 is held, by its second end, in the movable core 14 'but does not pass through the fixed core 26'. In other words, along Tax AA ', starting from the first end 10i and going towards the second end 10 ₂ of the solenoid valve, are successively disposed the needle 6, a movable core 14', in which the needle is inserted over a certain length (to adjust the low pressure, as before), then a fixed core 26 '.

The insertion length of the needle 6 in the movable core 14 'makes it possible to set the value of the low pressure Pb: the greater the insertion length of the needle in the movable core, the more the spring 8 is compressed and the higher one of the pressure thresholds (here the threshold Pb) is high. In other words, the low pressure Pb is adjusted (or fixed) by more or less deep insertion of the needle 6 in the movable core.

As a variant, in order to adjust the low pressure Pb, it is possible, as in the previous embodiment, to apply a variable load or stress to the spring 8, more precisely at the end of the latter situated on the side of the first end 10i of the valve. This variable load or stress can be obtained by the plastic deformation of a metallic element applied to the end of the spring, this element possibly being the stop 12. This variant is illustrated in FIG. 2C.

The setting of the pressure threshold Ph will now be described.

A spring 16 'applies pressure, on the one hand to a surface 26'i of the fixed core 26' and, on the other hand, to a bearing surface 14'i of the movable core 14 '. Each of these bearing surfaces is perpendicular or substantially perpendicular to the axis AA '. This spring exerts a longitudinal force along this axis AA 'by tending to push the movable core towards the first end 10i. Inside the valve the spring 16 'is positioned between, on the one hand, the bearing surface 14'i and, on the other hand, the fixed core 26'. The position of this fixed core 26 ′ can be adjusted, for example by screwing into a fixed part of the solenoid valve, for example in an overmolded part 39, as illustrated in FIG. 6. This setting fixes the value of the high pressure Ph.

In other words, the position of the movable core 14 'at rest (not activated by the solenoid) results from the positioning of the element 26' and the action of the spring 16 ': by introducing the movable core 14' more (or less) deep into the valve, the high pressure Ph is adjusted. When the appropriate adjustment is made, the element 26 ′ can be covered by a portion 24 forming a cover and which can be fixed to the fixed part of the solenoid valve (for example again molded part 39), so that the setting obtained is not modified.

Thus, there is a first means for adjusting (or fixing) the low pressure Pb, and a second means for adjusting (or fixing) the high pressure Ph, these 2 means being independent of one the other.

The movable core 14 'can be moved, in one direction or the other along the axis AA', by variation of the current which feeds the solenoid, which makes it possible to more or less compress the spring 8 and, thus, to select the pressure threshold (Ph or Pb) to be applied in chamber 36 to move the drawer 4.

The length over which the movable core is moved is shorter than that over which the movable slide 4 is moved for the operation of the valve: in effect, the displacement of the movable core 14 ′ is intended to vary the pressure P to be applied in the cavity 36 to move the slide 4, between the pressure Ph called "high" and the pressure Pb called "low" (with Pb <Ph).

In other words :

- in a first operating state of the device (in the case of FIG. 6, this state is that in which the solenoid 15 is powered by a current), the movable core 14 ′ is positioned so that the pressure P at apply in the chamber 36 is at least equal to Ph to allow the connection of channels 30 and 32 by moving the drawer;

- In a second operating state of the device (in the case of FIG. 6, this state is that in which the solenoid 15 is not powered by a current), the movable core 14 ′ is positioned so that the pressure P at apply in the chamber 36 is at least equal to Pb to allow the connection of channels 30 and 32 by moving the drawer.

An example of the operation of such a device is then as follows.

When the solenoid is supplied by a current, the pressure of the fluid entering via the supply channel 30 acts mechanically on the slide 4, tending to move it against the effect of the spring 8, increased by the force resulting from the displacement of the 'assembly comprising the needle 6 and the movable core 14'. As a result, when the pressure P increases, the initial fluid or hydraulic connection between the channels 32 and 34 is closed in favor of a fluid or hydraulic connection between the channels 30 and 32. This takes place in the vicinity of the pressure threshold Ph, called "high pressure".

When the solenoid is not supplied by a current, the pressure of the fluid entering through the supply channel 30 acts mechanically on the slide, tending to move it against the effect of the spring 8. As a result, when the pressure P increases, the initial fluid or hydraulic communication between the channels 32 and 34 is closed in favor of a fluid or hydraulic connection between the supply channels 30 and 32. This takes place near the pressure threshold Pb, below the threshold Ph.

The adjustment of the pressure Pb results from the more or less deep insertion of the assembly comprising the needle 6 in the movable core 14 ′, consequently forming a rigid needle-abutment-movable core assembly.

The pressure adjustment Ph results from the more or less deep insertion of the fixed core 26 'which will define a fixed stroke value of the movable core 14'.

FIG. 7 illustrates the operation of a valve according to the invention, as described above in connection with FIG. 6. It represents the evolution of the pressure P32 in the supply path 32 as a function of the pressure P30 in the feed channel 30.

On the abscissa axis are shown the pressures Pb and Ph with their respective adjustment ranges indicated by double arrows in dashed lines.

When the solenoid is not activated (curve II ′), the threshold is defined by the pressure Pb. For a pressure in the supply channel 30, lower than this pressure Pb, the communication between the supply channels 30 and 32 is closed. For a pressure, in the supply path 30, greater than this pressure Pb, the communication between the supply paths 30 and 32 is open, which explains the increasing part of the curve II 'for P> Pb (the pressure in the feed path 32 approaches that in the feed path 30).

When the solenoid is activated (curve I ′), the threshold is defined by the pressure Ph. For a pressure, in the supply channel 30, lower than this pressure Ph, the communication between the supply channels 30 and 32 is closed.

For a pressure, in the supply path 30, greater than this pressure Ph, the communication between the supply paths 30 and 32 is open, which explains the increasing part of the curve I 'for P> Pb (here again , the pressure in the supply path 32 approaches that in the supply path 30).

A solenoid valve according to the embodiment described above, in connection with FIGS. 6 and 7, can be applied to a hydraulic pump, preferably a variable geometry pump such as a vane pump or a gear pump. The fluid used is then oil. Diagrams identical or similar to those of FIGS. 4A - 5B can be established, with an operation adapted to a valve generating a traction movement during activation.

Whatever the embodiment envisaged, it is possible to pass from one threshold to another by modifying the current supply of the solenoid, in one direction or in the opposite direction.

Whatever the embodiment envisaged, it is preferably sought to obtain a difference Ph - Pb, between the two levels of regulating pressure between 1 bar and 7 bars, for example around 2 bars. Such pressure levels are in fact suitable for application to an oil pump of a motor vehicle engine.

In the embodiments explained above, the solenoid is supplied by a constant voltage source to which it is connected by, for example, a switch or a relay.

As a variant, the solenoid can be controlled proportionally, thus allowing adjustment by control of several possible threshold levels between the threshold level at low pressure Pb and the threshold level at high pressure Ph. In this case, the supply of the solenoid implements an electrical control system (for example PWM) capable of generating a variable current. One or more levels between Pb and Ph can thus be defined, each corresponding to an intermediate position of the mobile core, between the 2 positions which correspond to Pb and Ph. Its intermediate positions are reached with a current determined by the choice of the duty cycle applied on the PWM.

Claims

1. Device of the solenoid valve type (1, 100), with pressure-responsive slide mechanism comprising:

- a body (2) comprising at least 3 channels (30, 32, 34) for the flow of a liquid;

- means forming a drawer (4), which can be moved in said body (2) by a pressurized fluid, between a first position, in which there is fluid communication between a first channel (30) and a second channel ( 32) among said 3 flow paths (30, 32, 34), and a second position, in which there is fluid communication between said second path (32) and the 3 ^th path (34);

- Means (14, 14 ', 15), for selecting a threshold for activating pressure for moving said slide, from at least a first threshold (Ph) and at least a second threshold (Pb, with Pb <Ph ) pressure;

- Means (6, 12, 16, 22, 16 '26'), for adjusting at least said first threshold (Ph) and at least said second threshold (Pb) for activating said drawer.

2. Device according to claim 1, comprising:

- a first spring (8), which forces the drawer into the first position;

- an electromagnetic actuator (15);

- a movable core (14, 14 '), which can be moved inside the device, using said electromagnetic actuator (15), between a deactivated position and an activated position, to select said pressure threshold activation of said drawer.

3. Device according to claim 2, the means (6, 12, 16, 14, 14 '), for adjusting one of the thresholds (Pb) of activation pressure of said drawer comprising means for adjusting a longitudinal force of support of the first spring (8) on the drawer (4).

4. Device according to claim 3, the means for adjusting a longitudinal support force of the first spring (8) on the drawer comprising a stop (12) against which the spring is supported, and a needle, inserted in the movable core (14) over a length L.

5. Device according to claim 4, the length L being adjustable and / or the device further comprising means for adjusting a pressure or a deformation of said stop (12).

6. Device according to claim 2 to 5, the means (14, 22, 14 ', 26'), for adjusting the other threshold (Ph) of activation pressure of said drawer comprising means for adjusting the deactivated position of the core mobile (14, 14 ') inside the device.

7. Device according to claim 6, comprising means (22, 26 ') for adjusting the deactivated position of said movable core (14) comprising an element (22, 26') in adjustable support against said movable core.

8. Device according to claim 7, comprising a fixed core (26) and a second spring (16), disposed between the fixed core and the movable core, a support of the element (22, 26 ') on said movable compressing core more or less this second spring (16).

9. Device according to one of claims 7 or 8, said element (22) in adjustable support against said movable core comprising a plug (22) end of the device, in the support is adjusted for example by screwing.

10. Device according to claim 7, comprising a fixed core (26 ') and a second spring (16'), disposed between the fixed core and the movable core, a support, adjusted for example by screwing, of the fixed core (26 ' ) on said movable core compressing more or less this second spring (16).

11. Device according to one of claims 2 to 10, further comprising means for supplying the electromagnetic actuator (15) capable of generating a variable current, for example of the PWM type.

12. Device according to one of claims 1 to 11, wherein the difference Ph - Pb, between the two pressure levels, is between 1 bar and 7 bars.

13. Device according to one of claims 1 to 12, of the type generating a thrust movement during activation.

14. Device according to one of claims 1 to 12, of the type generating a traction movement during activation.

15. Hydraulic circuit of a pump (50), for example an oil pump, comprising a pump (50) and a device of the solenoid valve type, according to one of claims 1 to 14.

16. Method of operating a device of the solenoid valve type according to one of claims 1 to 14, in which:

- If the activation pressure threshold of said drawer is the first pressure threshold (Ph), a fluid under pressure P is injected to move said drawer (4), from the first position to the second position, the pressure P being greater at the first pressure threshold (Ph);

- If the activation pressure threshold of said drawer is the second pressure threshold (Pb), a fluid under pressure P is injected to move said drawer (4), from the first position to the second position, the pressure P being greater at the second pressure threshold (Pb), but lower than the first pressure threshold (Ph).

17. A method of operating a device of the solenoid valve type according to one of claims 2 to 11, in which:

- If the activation pressure threshold of said slide valve is the first pressure threshold (Ph), the movable core is moved inside the device, using said electromagnetic actuator (15), to adjust the pressure of activation at the second threshold (Pb) of activation pressure of said slide;

- A fluid P is injected under pressure to move said slide (4), from the first position to the second position, the pressure P being greater than the second pressure threshold (Pb) but less than the first pressure threshold (Ph).

18. Method of operating a device of the solenoid valve type according to one of claims 2 to 11, in which:

- If the activation pressure threshold of said drawer is the second pressure threshold (Pb), the movable core is moved inside the device, using said electromagnetic actuator (15), to adjust the pressure of activation at the first threshold (Ph) of activation pressure of said slide;

- A fluid P is injected under pressure to move said slide (4), from the first position to the second position, the pressure P being greater than the first pressure threshold (Ph).