DETAILED DESCRIPTION

[0021] A pressure-regulating valve 1 according to the invention ( FIGS. 1 and 2 ) has, for example as the housing, a tube section 2 with a throughflow cross section 3 through which exhaust gas can flow in an exhaust-gas flow direction 4 . The throughflow cross section 3 of the tube section 2 is, for example, of circular cross section and has a center axis 5 . The tube section 2 is designed as a thin-walled tube with a tube wall 6 which has an inner side 7 which delimits the throughflow cross section 3 .

[0022] Arranged in the interior of the tube section 2 is a throttle 10 which is arranged such that it can be pivoted about an axis 11 directed perpendicular to the center axis 5 . The pivot axis 11 may be spaced apart, by a distance e, from the center axis 5 , with the result that the pivot axis 11 is arranged eccentrically in relation to the center axis 5 . The amount e is preferably in the range between 0<e<⅛ D-{fraction (1/12)} D, in particular about {fraction (1/10)} D, where D is the diameter of the throttle.

[0023] According to another preferred embodiment, the pivot axis 11 is arranged centrally, that is to say the pivot axis 1 intersects the center axis 5 . The eccentricity e thus has the value of 0. The exhaust-gas flow consequently does not subject the throttle 10 to an opening torque, with the result that the position of the throttle 10 in the tube section 2 is not influenced by the exhaust gas.

[0024] The throttle 10 has a throttle stem 12 which is mounted such that it can be rotated about the pivot axis 11 . At least one end of the throttle stem 12 penetrates the wall 6 of the tube section 2 and projects some way outside the tube section 2 . At the free end (not shown) of the throttle stem 12 , said free end being located outside the tube section 2 , a lever element 13 is connected in a rotationally fixed manner to the throttle stem 12 . At the free end of the lever element 13 , the lever element 13 is connected to a push rod 14 , which can be driven such that it can be moved in a double-arrow direction 15 , for example parallel to the center axis 5 . for this purpose, use is usually made of an actuating device (not shown) e.g. a negative-pressure/positive-pressure drive device or some other linear-drive device.

[0025] Located in a throttle plane 18 , a first throttle wing 16 and a second throttle wing 17 extend from the throttle stem 12 . The throttle wings 16 , 17 are designed essentially in the form of flat plates and extend away from the throttle stem 12 in the throttle plane 18 more or less as far as the inner side 7 of the tube. The first throttle wing 16 has a first flat side 19 and a second flat side 20 as well as a boundary edge 21 . The second throttle wing 17 has a first flat side 22 , a second flat side 23 as well as a boundary edge 24 . In a closed position of the throttle stem 12 ( FIG. 1 ), in which the throttle plane 18 is located perpendicularly to the center axis 5 , the boundary edges 21 , 24 together with the inner side 7 of the tube section 2 form a clearance gap 25 .

[0026] Adjacent to the cross-section plane of the tube section 2 which runs through the pivot axis 11 , the wall 6 has thickened portions 30 which are bounded by a ramp surface 31 , 31 a and step surfaces 32 , 32 a. The step surface 32 , in the region of the first throttle wing 16 , is oriented in the same direction as the exhaust-gas flow direction 4 , in the axial direction of the tube section 2 . The step 32 a is oriented counter to the exhaust-gas flow direction 4 , in the axial direction of the tube section 2 . The radial extent to the steps 32 , 32 a is somewhat greater than the clearance gap 25 , with the result that, in the closed state of the throttle, the first throttle wing 16 has the border of its second flat side 20 resting on the step 32 and the second throttle wing 17 has the border region of its first flat side 22 resting on the step 32 a . In this position, the through-passage cross section 3 is closed off in a sealed manner by the throttle 10 .

[0027] In a plan view, the throttle 10 has increased material thickness in the center, with the result that a cylindrical thickened portion 35 is formed. The thickened portion 35 is arranged on both sides in relation to the throttle wings 16 , 17 and extends, from the radial center of the throttle 10 , approximately over a third of the diameter of the throttle 10 . On the outside in the radial direction, the thickened portion 35 is adjoined by a tapered portion 36 which reduces the material thickness of the throttle 10 , in a wedge-shaped manner in cross section, in the direction of the border region of the throttle wings 16 , 17 .

[0028] In the region of the thickened portion 35 , the throttle 10 has a cylindrical through-passage opening 40 perpendicular to the throttle plane 18 . The through-passage opening 40 has a step 41 and is designed, in a radially widened manner at one end, as a stepped bore. The through-passage opening 40 is of conically widened design at both ends, the conically widened portion at one end being designed as a sealing seat 42 . A valve element 43 with a valve tappet 44 and a valve cone 45 is arranged in an axially displaceable manner in the opening 40 . The valve cone 45 is fitted in the sealing seat 42 . The valve tappet 44 is of radially widened design at its free end, a conical helical spring 46 being supported between the step 41 and the radially widened end of the valve tappet 44 .

[0029] The helical spring 46 is of conical design, having a larger diameter in the region of the step 41 and a smaller diameter in the region of the radically widened end of the valve tappet 44 .

[0030] The through-passage opening 40 , the helical spring 46 and the valve element with the valve tappet 44 and the sealing cone 45 thus form a valve, which is integrated in the throttle 10 , in the manner of a pressure relief valve, in particular of a pressure relief tappet valve. The spring constant of the helical spring 46 here is selected such that, with the throttle 10 closed according to FIG. 1 , the pressure relief valve, in the case of a predetermined pressure difference between the regions upstream and downstream of the throttle 10 (as seen in the flow direction 4 ), opens.

[0031] The functioning of the pressure-regulating valve according the invention is explained in more detail hereinbelow. In an opened position (according to FIG. 2 ), the throttle 10 is arranged such that the throttle plane 18 is aligned approximately parallel to the throughflow direction 4 , with the result that the throttle 10 releases the throughflow cross section to the maximum extent and exhaust gas can flow in the throughflow direction 4 .

[0032] In this position, the valve 40 , 44 , 45 , 46 in the manner of a pressure relief valve is not active since there is no pressure difference present in the direction in which the valve acts.

[0033] In a closed position ( FIG. 1 ) of the pressure-regulating valve 1 according to the invention, the throttle 10 is subjected, via the push rod 14 and the lever 13 , to a closing force such that the throttle 10 has its border regions resting with sealing action on the steps 32 and 32 a of the tube walls 6 . The throttle 10 thus closes the cross section 3 fully. A positive pressure thus builds up upstream of the throttle 10 , as seen in the exhaust-gas flow direction 4 , and, once the pressure difference between the regions upstream of the throttle 10 and downstream of the throttle 10 which is predetermined for triggering the pressure release valve 40 , 44 , 45 , 46 has been exceeded, causes the valve 40 , 44 , 46 to open, a defined pressure difference thus being established upstream and downstream of the throttle 10 . According to the invention, it has been found that reliable and precise pressure regulation takes place if the pressure regulation and/or the volume-flow regulation is affected not with the throttle 10 in a partially opened position, but with the throttle 10 fully closed and with the throttle 10 provided with a valve 40 , 44 , 45 , 46 , in the manner of a pressure relief valve, which, once a defined pressure difference has been exceeded, opens and thus ensures a constant pressure difference on both sides of the throttle 10 .

[0034] It is particularly advantageous for the eccentricity e to be selected to be very small, in particular equal to 0, because, with an eccentricity of 0, the gas flow does not subject the throttle 10 to any opening torque, which would have to be compensated for by corresponding closing forces. This avoids the situation where, in the case of very high exhaust-gas pressures, the throttle 10 lifts off from the steps 32 , 32 a and this adversely affects the pressure-regulating function of the valve 40 , 44 , 45 , 46 .

[0035] A pressure-regulating valve 1 according to the invention has the advantage that it is of relatively straightforward construction and, by virtue of the opening/closing and pressure-regulating functions being separated, makes it possible to establish a defined predetermined pressure difference upstream and downstream of the throttle 10 , as seen in the flow direction 4 . It is also advantageous that the pressure difference being established is independent of any dynamic change in exhaust-gas-volume flow occurring, with the result that, in the case of dynamic operation of an internal combustion engine, as constantly occurs in a motor vehicle, this does not influence a predetermined pressure difference to any significant extent.

[0036] In contrast to convention counterpressure regulating valves with a throttle in the case of which the pressure regulation takes place by means of a small opening gap via the throttle, the pressure-regulating valve according to the invention does not have any dynamic-pressure hysteresis in the case of changes in the dynamic exhaust-gas-volume flow. This results in very precise and foreseeable pressure regulation.

[0037] It should be apparent to those skilled in the art that the above-described embodiments are merely illustrative of but a few of the many possible specific embodiments of the present invention. Numerous and various other arrangements can be readily devised by those skilled in the art without departing from the spirit and scope of the invention as defined in the following claims.