Valve comprising a movement transformation device

Abstract

The invention relates to an engine control valve (1) which comprises a rotatable actuator (7), a valve (5), and a movement transformation device (9) suitable for transforming the rotation of the actuator (7) into translation of the valve (5). The movement transmission device (9) comprises a helical link with uniform pitch for translating the valve (5).

Claims

1. An engine control valve comprising: a rotary actuator; a valve shutter with an open position and a closed position; a movement conversion device configured to convert a rotational movement of the actuator into a translational movement of the valve shutter, wherein the movement conversion device comprises a constant-pitch helical connection for driving the translational movement of the valve shutter; and at least one follower attached to the valve shutter and configured to collaborate with a camway of constant pitch, wherein: the helical connection comprises the camway, the movement conversion device further comprises a tubular wall in which the camway is formed, the camway comprises an open slot in the tubular wall, the open slot having a first end that limits the translational movement of the valve shutter in one of the open and closed positions, and a second end that limits the translational movement of the valve shutter in the other position, the slot having the shape of a helicoid extending along the tubular wall, the movement conversion device is monolithic, the at least one follower is mounted to rotate on a bar attached to the valve shutter, the bar being arranged in a volume delimited by the tubular wall so as to collaborate with an input wheel which is driven by the rotary actuator and which is designed to rotate the bar, and the at least one follower that is mounted to rotate on the bar is a wheel.

2. The valve as claimed in claim 1, wherein the camway comprises two tracks arranged facing one another on the tubular wall.

3. The valve as claimed in claim 1, wherein the input wheel is mounted to rotate on the tubular wall.

4. The valve as claimed in claim 3, wherein the input wheel is mounted to rotate on the tubular wall via a rolling bearing.

5. The valve as claimed in claim 1, wherein a position sensor that senses the position of the valve shutter is positioned in a space delimited by the tubular wall.

6. The valve as claimed in claim 5, wherein the position sensor is a linear-displacement transducer.

7. The valve as claimed in claim 1, wherein the rotary actuator comprises an electric motor that behaves in a substantially linear manner.

8. The valve as claimed in claim 7, wherein the electric motor is a DC motor.

9. The valve as claimed in claim 1, wherein the rotary actuator is connected to the movement conversion device by transmission means which behave in a substantially linear manner.

10. The valve as claimed in claim 1, wherein a drive train from the rotary actuator to the valve shutter is made up of elements that behave in a substantially linear manner.

11. An assembly comprising: a valve comprising: a rotary actuator, a valve shutter with an open position and a closed position, a movement conversion device configured to convert a rotational movement of the actuator into a translational movement of the valve shutter, wherein the movement conversion device comprises a constant-pitch helical connection for driving the translational movement of the valve, a bar attached to the valve shutter, at least one follower attached to the valve shutter and designed to collaborate with a camway of constant pitch; and control means which are programmed to a linear model, wherein the helical connection comprises the camway, the movement conversion device further comprises a tubular wall in which the camway is formed, the camway comprises an open slot in the tubular wall, the open slot having a first end that limits the translational movement of the valve shutter in one of the open and closed positions, and a second end that limits the translational movement of the valve shutter in the other position, the slot having the shape of a helicoid extending along the tubular wall, the movement conversion device is monolithic, the at least one follower is mounted to rotate on the bar attached to the valve shutter, the bar being arranged in a volume delimited by the tubular wall so as to collaborate with an input wheel which is driven by the rotary actuator and which is designed to rotate the bar, and the at least one follower that is mounted to rotate on the bar is a wheel.

12. The valve as claimed in claim 1, the movement conversion device further comprising a helical torsion spring that returns the valve shutter to the closed position, wherein the helical torsion spring behaves in a substantially linear manner, and wherein the helical torsion spring is disposed about the rotary actuator.

13. The valve as claimed in claim 1, and further comprising: an input wheel mounted to rotate on the tubular wall and driven by said rotary actuator to rotate the valve shutter.

14. The valve as claimed in claim 11, and further comprising: an input wheel mounted to rotate on the tubular wall and driven by said rotary actuator to rotate the valve shutter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be better understood in the light of the description which follows of one preferred and nonlimiting embodiment, which description is given with reference to the attached drawings, among which:

(2) FIG. 1 is a perspective view of a valve according to the invention;

(3) FIG. 2 is an exploded view of the valve of FIG. 1;

(4) FIG. 3 is a perspective view of the movement conversion device of the valve of FIG. 1;

(5) FIG. 4 is a graph showing the axial force applied to the valve shutter as a function of its valve lift travel in the valve of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

(6) FIG. 1 depicts an engine control valve 1 which in this example is an exhaust gas recirculation valve commonly known as an EGR valve. The various elements that make up the valve 1 are visible separately in the exploded view of FIG. 2.

(7) The valve 1 comprises a fluid inlet 2 and a fluid outlet 3 between which the head 4 of a valve shutter 5 is positioned. In the way that is conventional for an EGR valve, when the valve shutter 5 is in the closed position it shuts off the flow of fluid entering via the inlet 2 and leaving via the outlet 3. By contrast, when the valve shutter 5 is wide open it allows this fluid to flow freely, whereas when the valve shutter 5 is in an intermediate position it meters the fluid.

(8) The valve 1 comprises a mount 6 on which there are mounted an actuator, here consisting of an electric motor or rotary actuator 7, a movement conversion device 9 and a transmission wheel 8 which allows the motor 7 to drive the movement conversion device 9, the latter converting the rotary movement of the transmission wheel 8 into a rectilinear movement of the valve shutter 5.

(9) The movement conversion device 9 has a tubular overall shape and at one of its ends comprises a valve seat 10 and at the other of its ends comprises a camway or constant pitch helical connection 11. As an alternative, the valve may have no valve seat. In this example, the camway 11 comprises two tracks made in a tubular wall 12 of the movement conversion device 9. A bar 13 fixed to the valve shutter 5 and equipped with followers 14 is designed to follow the camway 11.

(10) The movement conversion device 9 collaborates with an input wheel 15 comprising a toothed portion 16 attached to a tubular portion 17 mounted to rotate on the movement conversion device 9 via a rolling bearing 18.

(11) Elastic return means 19 are provided here in the form of a helical torsion spring to return the input wheel 15 to one of its extreme angular positions corresponding, in this example, to the closed position of the valve shutter 5.

(12) The motor 7 is therefore in this instance operated against the action of the return means 19 in order to open the valve shutter 5.

(13) A position sensor 20 additionally allows the position of the valve shutter 5 along its axial travel to be measured at any moment, and does so via a feeler 21 kept in contact with the bar 13 by means of a spring (not depicted). The sensor 20 therefore behaves in a linear manner in so far as the feeler 21 [lacuna].

(14) A protective cap 22 (see FIG. 2) mounted on the support 6 protects the rotary parts of the valve 1.

(15) The motor 7 is powered and driven with inbuilt control in a way that is conventional to computation means (not depicted).

(16) When the motor 7 is made to rotate, it drives the rotation of the transmission wheel 8 (and any other gearset that might be provided) which in turn turns the input wheel 15. The latter also drives the rotation of the bar 13 through complementary shapes (see FIG. 1), while leaving it free to effect axial translational movement. That causes the followers 14 to roll along the camway 11 (which is fixed, the movement conversion device 9 being fixed to the support 6) and therefore causes the joint translational movement of the bar 13 and of the valve shutter 5 in the axial direction, causing the valve shutter 5 to open or to close.

(17) With reference to FIG. 4, the movement conversion device 9 is depicted outside the valve 1 here. In this figure, the input wheel 15 is in an angular position which: corresponds to an angular position of the bar 13; corresponds to a position of the followers 14 in the camway 11 (at the end of the track); corresponds to a position of the valve shutter (the closed position).

(18) The camway 11 is configured so that the force exerted on the valve shutter 5 as it opens is substantially linear.

(19) The movement conversion device 9 thus behaves in a way very similar to that of a linear system. A linear system is a system model which applies a linear (first order) operator to an input signal. A linear system typically displays characteristics and properties that are far simpler than the general non-linear case.

(20) These linear properties improve the controllability of the system.

(21) The axial force applied to the valve shutter varies in a linear or near-linear manner along the axial travel of the valve shutter 5. The curve 23 indicative of the axial force applied to the valve shutter 5 as a function of its axial travel (valve lift) is therefore substantially a straight line. In FIG. 4, this curve 23 is depicted in solid line whereas a conventional curve 24 relating to valves of the prior art is shown in dotted line.

(22) For the same rotation of the motor 7, corresponding directly to a variation in angle of the bar 13, the variation in axial force applied to the valve shutter 5 thanks to collaboration between the camway 11 and the followers 14 is therefore substantially constant and is identical over the entire working rotational range of the motor 7.

(23) In the example of FIG. 4, the variation in the axial force applied to the valve shutter 5 is not only constant but very small. By way of example, the force at the start of valve lift (point 25 in FIG. 4) may be 420 N while the force at the end of valve lift (point 26 in FIG. 4) may be 380 N, which represents a variation in force of around 10% over the entire valve lift travel of the valve shutter 5. By way of comparison, the order of magnitude of the variation in force for valves of the prior art is 1000% (see FIG. 4).

(24) The curve 23 is therefore not only a straight line here but also nearly horizontal.

(25) The camway 11 is, in the present example, made up of two tracks arranged face to face (diametrically opposite each other) on the tubular wall 12, each of these tracks being formed here of an open slot made in the tubular wall 12. The shape of the slot is a helicoid extending along the tubular wall 12. To obtain an axial valve lift force with constant variation, this helicoid in this example has a constant helix pitch (see FIG. 3).

(26) Thus, by virtue of the movement conversion device 9, the way in which the valve 1 behaves when opened is substantially linear in the sense that a rotation of the motor 7 through a given angle will produce substantially the same variation in force on the valve shutter 5 whatever the position of the valve shutter 5. Because this variation is also reduced to a minimum here, rotating the motor 7 through a given angle will cause substantially the same force to be applied to the valve shutter 5, regardless of the position of the valve shutter 5.

(27) Moreover, the substantially linear way in which the movement conversion device 9 behaves may be supplemented by other components of the drive train extending from the motor 7 to the valve shutter 5 and which likewise advantageously behave in a substantially linear manner.

(28) The embodiment of the present example, which is particularly advantageous, contains in this drive train only elements which behave in a substantially linear manner. This drive train can therefore be modeled as a linear model with satisfactory results. This linear model is embedded in the electronic device selected to control the valve.

(29) The motor 7 first of all in this instance is a DC motor, which means that it behaves in a substantially linear manner.

(30) All the gearing that transmits the rotation of the motor 7 to the input wheel 15 also behaves in a substantially linear manner, which means to say that the teeth of the gearwheels (in this instance the wheels 8 and 15) are evenly distributed about the working circumference of said wheels.

(31) Friction is also a source of non-linearity. The rolling bearing 18 here reduces this friction so that the system behaves even more like a linear system.

(32) The helical torsion spring that makes up the return means 19 also here behaves in a substantially linear manner, which means to say that the rotation of the input wheel 15 is directly proportional to the torque that has caused this rotation (the torque applied by the transmission wheel). This manner of behaving is obtained by choosing a spring with a substantially constant spring rate.

(33) The entire drive train from the motor 7 to the valve shutter 5 thus behaves in a substantially linear manner, thus making it more controllable.

(34) The workload on the computation means (not depicted) for controlling the motor 7 is reduced here because, in order to get from a position instruction for the valve shutter 5 to the corresponding command for the motor 7, the computation means have linear equations to handle, which requires less computing power, better responsiveness and greater robustness. The control of the motor 7 is therefore linear in this instance, which means to say performed to a first-order linear model.

(35) Other features of the valve 1 can be conceived of without thereby departing from the scope of the invention. In particular, the gearset from the motor 7 to the input wheel 15 may contain any number of gears or pinions.

(36) The valve shutter can be any component that controls the flow (opens, closes and/or meters) using a member that undergoes a translational movement.