Control apparatus for camshaft phaser

A device for controlling a camshaft phaser includes a hydraulic element with a body, a slide assembly having a slide body, and a valve assembly with a first valve, a second valve, and a third valve. The device also includes an actuator which moves along a longitudinal axis between 1) a first position in which the first valve opens or closes a first fluid communication, 2) a second position in which the second valve and the tray open or close a second fluid communication, and 3) a third position in which the third valve and the slide body open or close a third fluid communication between a retard port and a retard chamber.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage application under 35 USC 371 of PCT Application No. PCT/EP2019/067182 having an international filing date of Jun. 27, 2019, which is designated in the United States and which claimed the benefit of FR Patent Application No. 1856149 filed on Jul. 4, 2018, the entire disclosures of each are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a control device for controlling the position of a variable camshaft phaser of an internal combustion engine.

BACKGROUND OF THE INVENTION

Camshaft phasers are used to control the angular relationship between the crankshaft pulley and the camshaft of an internal combustion engine. In a double overhead camshaft engine, a camshaft phaser is used to offset the intake camshaft so as to expand the engine torque curve, increase power at variable high rpm and improve the idle quality. In addition, the exhaust cam can be offset by a camshaft phaser to allow control of exhaust gas recirculation (EGR) such as an internal EGR valve, which considerably reduces polluting emissions and also saves on fuel.

By rotating the camshafts to advance or retard positions the angular timing of the valve lift is changed. The camshaft phasers are controlled by hydraulic systems that use lubricating oil pressurized by the oil pump.

In order to allow the rotation of the camshaft, the camshaft phaser consists of a stator portion connected to the crankshaft by means of a chain or a belt, and a rotor portion secured to the camshaft.

One or more pairs of hydraulic chambers are arranged between the rotor and the stator constituting a rotary actuator. Each pair of hydraulic chambers consists of an advance chamber and a retard chamber.

Two different technologies allow the rotational movement of the rotor relative to the stator.

The first technology consists in using the pressure difference between the pressurized oil coming from the oil pump and the engine drainage pressure close to atmospheric pressure. Thus, when the pressure in the advance chamber is greater than the pressure in the retard chamber, the rotor rotates in the advance direction and likewise, when the pressure in the retard chamber is greater than the pressure in the advance chamber, the rotor turns in the retard direction. The direction of rotation is controlled by a four-port, three-position solenoid valve. The volume of oil used for the movement of the rotor is taken from the high pressure circuit and evacuated via a drain, something which consumes hydraulic power

The second technology consists in using the torque oscillations exerted on the camshaft, which come from the compressive forces of the valve springs. These oscillations are transferred to the rotor, which creates a pressure difference on each pair of advance and retard chambers. Each pair of chambers is hydraulically connected by a channel including a valve allowing oil to flow in one direction. The rotor rotates in one direction. The advance or retard direction of rotation is selected by a five-port, three-position solenoid valve. A valve is integrated in a slide assembly of the solenoid valve. Depending on the position of the slide assembly, rotation is in the advance direction or the retard direction. The volume of oil displaced during the movement of the rotor is transferred between the advance chamber and the retard chamber. Oil is recirculated inside the phaser and therefore no hydraulic power is consumed. A supply of oil is required via the pressurized oil circuit from the oil pump. In order to avoid venting the internal pressure of the camshaft phaser to the oil circuit of the engine and disrupting the latter, a second valve is used at the inlet of the control solenoid valve. The valves currently used are of the ball or spring type and must have a permeability/size ratio that is compatible with the expected performance of the camshaft phaser, something which is difficult to achieve.

Manufacturers are seeking increasingly compact solutions for camshaft phasers. Solutions such as the control device also known as the central oil supply in the phaser (referred to as “barrel check valve”) cannot be used because the space available for the camshaft phaser in the engine is insufficient. To this end, a compromise must be sought between a more compact camshaft phaser and its speed of rotation.

In this context, the invention aims to solve at least one of the problems associated with known valves.

SUMMARY OF THE INVENTION

The present invention solves the abovementioned problems by providing a control device for controlling a camshaft phaser, for locking or releasing a rotor of a camshaft phaser of an internal combustion engine. Furthermore, the control device comprises a hydraulic element comprising a body, a slide assembly having a slide body, a seal and a valve assembly comprising a first valve, a second valve and a third valve. The control device further comprises an electromagnetic actuator connected to the slide assembly of the hydraulic element which can move along a longitudinal axis between:a first position, in which the first valve opens or closes a first fluid communication between an advance port of the slide body and an advance chamber of the camshaft phaser and,a second position in which the second valve and the slide body open or close a second fluid communication between an oil circuit coming from the engine and a supply port of the slide body and,a third position in which the third valve and the slide body open or close a third fluid communication between a retard port of the slide body and a retard chamber of the camshaft phaser. Moreover, in a first embodiment of the invention, the valve assembly comprises at least three valves integrated in a flexible one-piece part. Furthermore, each valve comprises at least one vane connected to two flexible arms and in that the valve is connected to two contiguous rigid rings. In a second embodiment of the invention, the valve assembly comprises a longitudinal bar and at least three valves integrated in a flexible one-piece part. Moreover, the valve comprises at least one vane connected to a flexible arm extending along the longitudinal axis and the longitudinal bar connects the valve to the contiguous valve. In addition, the longitudinal bar connects two contiguous valves. A method for producing the control device according to the two embodiments of the invention described above comprises the following steps:inserting the valve assembly into the slide bodyinserting the slide insert into the assembly obtained in the previous step,inserting the corrugated stop ring into the assembly obtained in the previous step,inserting the compression spring into the body,inserting the slide assembly into the body,crimping the hydraulic element with the electromagnetic actuator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

To facilitate and clarify the following description, the orientation from top to bottom is arbitrarily chosen and, words and expressions such as “above, below, top, bottom, high, low, etc.” may be used without any intention to limit the invention.

FIGS. 1 and 2show an engine10, a control device12and a camshaft phaser13. The control device12is arranged in a bore made in the bottom end of the engine10.

FIGS. 3 and 4show the control device12. The control device12comprises an electromagnetic actuator14and a hydraulic element16. The electromagnetic actuator14manages the hydraulic element16. The electromagnetic actuator14includes a connector18, a coil20, a rod22, a housing24and a bracket26. The connector18is arranged at an opposite end to the hydraulic element16. The hydraulic element16includes a body28, a slide assembly30, a seal32, a compression spring40and a washer44. The slide assembly30includes a valve assembly34, a slide body36, a slide insert38, and a stop ring42.

According toFIGS. 3 and 4, the slide assembly30is mounted in the body28and controls a flow of fluid between the advance and retard chambers of a camshaft phaser (not shown) to rotate the camshaft phaser in the advance or retard directions.

FIGS. 3 and 4show the body28of the hydraulic element. The body28extends along a central longitudinal axis X. The body28is cylindrical in shape. The body28includes a bore29. The slide assembly30defines an internal chamber45where the recirculation pressure of the control screw18prevails.

The term “at least one opening”, used in the description below, defines a number of openings comprising at least one opening.

FIG. 3shows the hydraulic element16comprising the body28having three ports46,48,50arranged radially, which makes three ports. The port46is also referred to as the advance port46. The port48is referred to as the retard port48. The port50is referred to as the supply port50. The three ports46,48,50are provided with a filter53.

InFIG. 3, the supply port50has at least one opening connected to the pressurized oil circuit of the engine (not shown). The advance port46has at least one opening connected to the advance chambers of the rotor of the camshaft phaser13(not shown). The retard port48has at least one opening connected to the retard chambers of the rotor of the camshaft phaser13(not shown).

FIG. 3shows the slide body36comprising openings54,56,58,60. The openings54,56,58are arranged radially all around the slide body36. The opening54is also referred to as the advance opening54. The opening58is also referred to as the supply opening58. The opening56is also referred to as the retard opening56. The opening60is also called the recirculation opening60. The slide body36includes at least the advance opening54, at least the retard opening56, at least the supply opening58, and at least the recirculation opening60. The openings54,56,58are subjected to the recirculation pressure via the internal chamber45. The internal chamber45is arranged between the slide insert38and the slide body36.

According toFIG. 3, the slide assembly30is arranged inside a bore made in the body28of the hydraulic element16. The slide assembly30extends along the longitudinal axis X. The oil supply openings58communicate with the supply port50regardless of the position of the slide assembly30on the longitudinal axis X. The recirculation openings60communicate with the advance port46or the retard port48depending on the position of the slide assembly30on the longitudinal axis X. The advance openings54may or may not communicate with the advance port46depending on the position of the slide assembly30on the longitudinal axis X. The retard openings48may or may not communicate with the retard port48depending on the position of the slide assembly30on the longitudinal axis X.

According toFIG. 3, the recirculation60and supply58openings of the slide body are shown. The recirculation60and supply58openings are elongate in a circumferential direction perpendicular to the longitudinal axis X. In this way, the recirculation60and supply58openings of the slide body each have an oblong projected section. This oblong cross section allows a greater flow surface area than a circular opening for the same width along the axis X and therefore a greater flow of fluid through the advance46, retard48and supply50ports.

According toFIG. 3, the recirculation openings60and the oil supply openings58are positioned facing the vanes62of the valve assembly34. The valve assembly34is arranged in a bore of the slide body36such that an external surface of the valve assembly34is in contact with the inner surface of the slide body36.

A first embodiment is described according toFIG. 5. The valve assembly34is tubular, i.e. it has a cylindrical shape and is open at both ends66. Oil can flow through the internal volume of the valve assembly34, with the oil flowing in the direction of the central longitudinal axis X. The thickness of the tube of the valve assembly34is very small compared to its diameter, i.e. of the order of 0.1% to 10%. The valve assembly34includes at least three rigid rings68and at least a first valve70, a second valve71and a third valve73. Each valve70,71,73comprises at least one vane62connected to two flexible arms72,74and each valve70,71,73is connected to two consecutive rigid rings68. The valve assembly34includes at least one angular indexing element76formed by an internal or external notch. As shown inFIGS. 2, 3 and 4, the angular indexing element76does not allow rotation of the valve assembly34inside the body28of the hydraulic element16. The rigid rings68may have one or more differently shaped openings to allow the circulation of oil within the valve assembly34. The vane62is elongate in the tangential direction of the tubular valve assembly34. The shape of the vane62defines an oblong shape complementary to the oblong section of the recirculation opening58and the supply opening60of the slide body. Furthermore, the vane62has a surface area which is larger than the surface area of the recirculation opening60and the supply opening58of the slide body. Covering the two surfaces provides the oil seal necessary for one-way valve operation. The valve assembly34comprises a plurality of valves70arranged in a circumferential direction perpendicular to the longitudinal axis X. In other alternatives, the valve assembly34may include both valves70,71,73arranged circumferentially and valves70,71,73arranged linearly along the longitudinal axis X. In the circumferential direction, each pair of flexible arms72,74extends towards the rear of the vane62with sufficient space for the next vane in the circumferential direction to be arranged between the pairs of flexible arms72,74. The arrangement of the vanes62in the same circumferential direction makes it possible to increase the permeability/size ratio of the valve assembly34.

In the embodiment described above, the vanes62and the arms72,74are rigidly secured to one another. The valve assembly34may be formed for example by cutting, for example with a laser, a cylindrical metal tube, such as for example steel. Other variants of the embodiment of the valve assembly34described above are possible such as starting with a metal sheet then cutting by stamping or by laser or by chemical attack and then rolling the metal sheet and finally welding the rolled metal sheet

According toFIG. 5, each valve70,71,73is defined by the pair of spring arms72,74. The arms72,74are also referred to as the first arm72and the second arm74. According toFIG. 5, the spring arms72,74diverge in the direction away from the vane62of the valve70. The first spring arm72extends on the left inFIG. 5towards a first end66while the second spring arm74extends on the right towards an open second end67of the valve assembly34.

The spring arms72,74are thin in terms of width. Due to the slenderness of the arms, an opening78of the vane is defined between the spring arms72,74of the valve70,71,73.

In a second embodiment, the control valve assembly34depicted inFIG. 6is tubular, i.e. has a cylindrical shape and is open at both ends80. The shape of the control valve assembly34is referred to as an origami shape. The valve assembly34includes at least three valves70. Each valve70comprises at least one vane62connected to a flexible arm82and a rigid element86. The valve assembly34further includes a longitudinal bar84extending along the central longitudinal axis X. The longitudinal bar84connects two contiguous valves70,71,73. Two contiguous valves70are interconnected by a longitudinal bar84extending along the axis X. The arm82is arranged longitudinally along the axis X. The longitudinal bar84is arranged between the two contiguous rigid elements86. The longitudinal bar84serves as an index for the valve assembly34. The vane62is elongate in the tangential direction of the tubular valve assembly34. The shape of the vane62defines a rectangular shape complementary to the oblong section of the recirculation opening60and the supply opening58of the slide body36. Moreover, the vane62has a surface area which is larger than the surface area of the recirculation opening60and the supply opening58of the slide body.

According toFIG. 6, the spring arm82moves at an angle to the longitudinal axis X while remaining in a plane perpendicular to the axis X. The spring arm82moves closer to the central longitudinal axis X.

The operation of the control device12for controlling the camshaft phaser13, for locking or releasing a rotor of a camshaft phaser13, will be described briefly. The electromagnetic actuator14is connected to the slide assembly30of the hydraulic element16, which can move along the longitudinal axis X between:a first position in which the first valve70opens or closes a first fluid communication F1between an advance chamber of the camshaft phaser13and an advance port46of the slide body36,a second position in which the second valve71and the slide body (36) open or close a second fluid communication (F2) between an oil circuit coming from the engine (10) and a supply port (50) of the slide body (36), anda third position in which the third valve73opens or closes a third fluid communication F3between a retard chamber of the camshaft phaser13and a retard port48of the slide body36.

The operation of the valve assembly34of the two embodiments will be described briefly. When the pressure exerted on the outside of the vane62is greater than the pressure exerted on the inside of the vane62, the force exerted on the surface tends to deform the flexible arms72,74,82. The arms72,74,82flex the vane62, the vane62moves towards the central longitudinal axis X which frees the recirculation opening60and the supply opening58of the slide body36. The maximum deformation of the arms72,74,82is limited by radial stops in the slide insert38.

The tubular valve assembly34described above could be incorporated into any other system of a vehicle requiring this type of valve to selectively block an opening as described.

Those skilled in the art will appreciate that the invention may be modified according to numerous variants without departing from the scope of the appended claims.

The method for producing and assembling the invention described above for the two embodiments will be described below:

The method for assembling the control device12includes the following steps:100/ inserting the control valve assembly34into the slide body36,110/ inserting the slide insert38into the assembly obtained in the previous step100,120/ inserting the corrugated stop ring42into the assembly obtained in the previous step110,130/ inserting the compression spring40into the body28,140/ inserting the slide assembly30into the body28,150/ crimping the hydraulic element16with the electromagnetic actuator14.

The assembled control device12is then placed on the engine10and then a screw is screwed through the fixing bracket26and tightened for axial and rotational immobilization.

LIST OF REFERENCE SIGNS USED