Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L9/00—Valve-gear or valve arrangements actuated non-mechanically
  • F01L9/10—Valve-gear or valve arrangements actuated non-mechanically by fluid means, e.g. hydraulic

Definitions

• the invention is based on a valve control device for an internal combustion engine according to the preamble of claim 1.
• a valve control device known from DE 195 11 320 A1
• a piston-shaped valve member of a gas exchange valve controls the opening and closing of an inlet and outlet cross section on the combustion chamber of the internal combustion engine to be supplied.
• the gas exchange valve designed as a poppet valve has an axially displaceable valve member, the valve member shaft of which is coupled via a piston rod to a hydraulically actuated adjusting piston (differential piston), via which the individual gas exchange valve can be actuated directly independently of the other gas exchange valves.
• the hydraulic adjusting piston is arranged directly on the valve member or the piston rod of the gas exchange valve and forms part of the gas exchange valve member itself.
• the adjusting piston delimits a first hydraulic working area with a lower annular end face and a second hydraulic working area with its upper piston end face. the over corresponding Pressure fluid lines can be filled and relieved of pressure with high pressure.
• the hydraulic working pressure in the working space located below acts on the adjusting piston in the closing direction of the gas exchange valve and the working space on the top acts on the adjusting piston in the opening direction of the valve member of the gas changing valve.
• the known valve control device has the disadvantage that there is a static indeterminacy on the adjusting piston, which is caused by double centering of the adjusting piston, since the hydraulic adjusting piston is attached to one of its outer circumferential surface directly as well as via the piston rod firmly connected to it second guide surface of the valve member is guided on its inner surface, which can result in jamming of the hydraulic adjusting piston and a blocking of the gas exchange valve even with the smallest tolerance deviations.
• Valve control devices are also known in which the hydraulic adjusting piston is fastened by means of a thread to the valve member of the gas exchange valve. This has the further disadvantage that the power transmission from the hydraulic adjusting piston to the valve member takes place via the screw thread, which results in a high dynamic tensile-pressure alternating stress in a zone with a high notch effect, which can cause fatigue fractures there.
• the valve control device for an internal combustion engine has the advantage that the hydraulic differential piston actuating the gas exchange valve member has a radial play between its two guide surfaces or to the guide surface of the gas exchange valve member.
• This is achieved in a constructively advantageous manner by a two-part design of the piston of a hydraulic valve actuation device, which is preferably designed as a differential piston, the two piston parts being operatively connected to one another in the axial direction, axially sliding and having radial play with one another.
• both piston parts can perform a relative movement in the radial direction to one another, which reliably avoids blocking of the differential piston in the event of tolerance deviations and thus reduces the manufacturing outlay with regard to tolerance sensitivity.
• the two-part differential piston is designed such that a first piston part with a larger diameter on its radial outer circumferential surface slides sealingly on a cylinder guide surface, with a radial play projecting axially through it Has piston rod of the gas exchange valve member.
• the second piston part which is smaller in diameter, is sealingly guided on the piston rod with its radial inner wall surface and has a radial play with the cylinder guide wall.
• the two piston parts can now move radially to one another during operation, the mutually facing axial piston end faces sealingly abutting one another.
• an axial sealing element for example a Provide sealing washer.
• the two piston parts are also operatively connected to the piston rod in the axial direction via axial stop surfaces and have a small axial play that enables a radial compensating movement to one another.
• the valve member of the gas exchange valve is advantageously formed in one piece with the piston rod of the differential piston and is advantageously axially guided in a guide bush, the end wall surface of which simultaneously delimits a lower hydraulic working space.
• the stop surfaces on the piston rod are advantageously designed on the one hand as a ring shoulder surface on which the differential piston comes to rest directly with its one end face.
• the second stop is advantageously formed by a separate component pressed onto the shaft of the piston rod, which component is designed as a valve wedge and can be placed around the piston rod in a multi-part form.
• This wedge-shaped component has a conical cross-sectional widening in the direction of the differential piston on its outer circumference, onto which a corresponding conical ring is pushed axially.
• the radially inward clamping force is applied by means of a clamping nut screwed onto the piston rod, which axially clamps the conical ring with radial clamping of the wedge-shaped stop components.
• a lower end face of the wedge-shaped stop components forms a stop face that interacts with an upper ring end face of the differential piston.
• a spring element between the nut and the conical ring which is preferably designed as a spring washer or spring ring and has a U-shaped contour can.
• valve control device it is thus possible with the valve control device according to the invention to integrate the gas exchange valve member into the actuator of a hydraulic valve actuator and to fasten the valve member directly to the hydraulic differential piston without radial forces or moments being transmitted between these two moving components.
• the invention is described on a valve control device in which both the opening and the closing stroke movement of the gas exchange valve member are carried out hydraulically, but it is alternatively also possible to mechanically, for example, the closing stroke movement of the valve member of the gas exchange valve, e.g. via a valve spring.
• the hydraulic piston is connected directly to a piston rod formed in one piece with the valve member of the gas exchange valve, but it is alternatively also possible to attach the hydraulic piston to a piston rod, which in turn is coupled to the valve member of the gas exchange valve outside the cylinder.
• differential piston part which is sealingly guided on the piston rod, in one piece with the piston rod, or to press this piston part onto the piston rod.
• valve control device for an internal combustion engine is shown in the drawing and is explained in more detail below.
• valve 1 shows a longitudinal section through the valve control device and the lower end of the gas exchange valve member with the valve plate and the corresponding valve seat on the combustion chamber of the internal combustion engine to be supplied.
• the valve control device for an internal combustion engine shown in a simplified sectional view in FIG. 1 has a gas exchange valve 1, the piston-shaped gas exchange valve member 3 of which is axially displaceable and has a valve sealing surface 5 on a plate-shaped valve member head 7 with a fixed valve seat 9 on the housing 11 of the internal combustion engine for control purposes an inlet or outlet cross section 13 of the combustion chamber of the internal combustion engine cooperates.
• the gas exchange valve member 3 has a valve member shaft 15 which merges in one piece into a piston rod 16 which projects into a cylinder housing 17 of a hydraulic adjusting device.
• the differential piston part 19 which is larger in diameter, is sealingly and slidably guided with its outer peripheral wall surface on a guide wall surface 22 in the cylinder housing 17 and borders with its axial end faces on hydraulic working spaces in the cylinder housing 17.
• a lower end surface 23 of the piston part 19 near the combustion chamber delimits a lower hydraulic one Working space 25, which can continue into the radial annular gap 20 via a play between the piston rod 16 and the piston part 19.
• a second piston part 51 of the differential piston 18 is smaller in diameter than the first piston part 19.
• This piston part 51 is sealingly guided on the shaft of the piston rod 16 and has a radial play with the guide wall 22 of the cylinder housing 17.
• the piston parts 19, 51 lie against one another with their axial end faces facing one another, a radial relative movement of the piston parts 19, 51 with respect to one another being possible.
• the working spaces 25 and 27 can be filled and relieved of pressure with a hydraulic working medium via pressure medium lines 31, 33, the opening of the pressure medium lines in the exemplary embodiment described being able to be controlled in a manner not shown by means of a control valve, preferably a solenoid valve, depending on a control device
• a control valve preferably a solenoid valve
• the valve member shaft 15 or the piston rod 16 is at its entry into the cylinder housing 17 by means of a Guide sleeve 35 guided axially sealing, the outer sleeve sealingly inserted into the cylinder housing 17 with its upper end wall surface 37 projecting into the cylinder housing 17 delimits the lower working chamber 25 at its end facing away from the differential piston 18.
• the upper working chamber 29 is closed at its end facing away from the differential piston 18 by an end wall of the cylinder housing 17.
• the piston rod 16 has two stops on its outer surface, against which the differential piston 18 with its end faces 23, 27 can come to rest in both axial adjustment directions.
• a lower shoulder 39 forms a first stop surface on the piston rod 16, the shoulder 39 being formed by reducing the cross section of the shaft of the piston rod 16 in the direction of the end facing away from the combustion chamber.
• the differential piston part 19 with its lower piston end face 23, which is larger in diameter, only bears against this shoulder 39 when there is no high pressure in the lower working chamber 25.
• the piston part 19 is held in contact with the upper stop by the high pressure in the lower working chamber 25, so that between the shoulder surface 39 on the piston rod 16 and the lower piston end face 23 on the piston part 19 there is a slight axial play, via which the pressure medium in the Annular gap 20 can flow and over which the piston rod 16 and the differential piston 18 can move axially relative to each other.
• This play is necessary in order to avoid a static over-determination of the system, since the closing stroke movement of the gas exchange valve member 3 is limited by the centering effect when it is in contact with the valve seat surface 9.
• a valve wedge 41 is arranged on the shaft of the piston rod 16 at the upper end of the piston rod 16, which end protrudes from the differential piston 18.
• This wedge 41 is ring-shaped and is preferably formed from two half-shells which are flush with their cylindrical inner wall surface on the piston rod shaft 16.
• the outer wall surface of these wedges is conical, the wall thickness of the wedges 41 increasing evenly in the direction of the differential piston 18.
• the wedges 41 have on their inner wall surface an annular web 43 which projects into a corresponding annular groove 45 in the peripheral wall of the piston rod 16.
• a conical ring 47 is axially slid onto this radially outer peripheral wall of the wedges 41, the inner wall diameter of which decreases conically in the direction of the differential piston 18 in a manner complementary to the cone angle of the wedges 41.
• the conical ring 47 is pressed axially onto the wedges 41 by means of a clamping nut 49, for which purpose the clamping nut 49 is screwed onto a thread 53 provided at the upper end of the piston rod 16.
• the wedges 41 are clamped radially on the shaft of the piston rod 16, so that the power transmission from the differential piston 18 to the piston rod 16 and further onto the shaft 15 of the gas exchange valve member 3 takes place via the wedges 41 and the thread 53 is not exposed to changing force introduction stresses.
• interposition of a spring washer between the conical ring 47 and the clamping nut 49 allows settlement phenomena of the components to be compensated and the necessary pretension in the axial connection to be maintained
• the lower ring end face of the wedges 41 facing the differential piston 18 forms the second stop surface on the piston rod 16, on which the second piston part 51 of the differential piston 18 comes to rest.
• a sealing ring can also be provided between the guide sleeve 35 and the shaft of the piston rod 16 in order to allow play between the piston rod 16 and the guide sleeve 35.
• the valve control device for an internal combustion engine works in the following manner.
• the idle state that is to say when the valve member 3 is in contact with the valve seat 9
• the hydraulic pressure in the lower working chamber 25 exceeds the hydraulic working pressure in the upper working chamber 29, so that the differential piston 18 is acted upon in the direction of the upper working chamber 29 and thus the gas exchange valve member 3 in its closed position fixed.
• the lower working chamber 25 is relieved of pressure via the control valve (not shown) and the pressure medium line 31 (or alternatively kept at the same pressure level) and at the same time the upper working chamber 29 is filled with a high pressure medium via the pressure medium line 33, so that the actuating force acting on the differential piston 18 in the upper working chamber 29 exceeds the actuating force acting on the differential piston 18 in the lower working chamber 25, since the total pressure application area of the differential piston 18 in the upper working chamber 29 is larger than in the lower working chamber 25 Working chamber 29 applied high pressure the differential piston 18 in the direction of the lower working chamber 25, the gas exchange valve member 3, 15, which is firmly connected to the differential piston 18 via the piston rod 16, also being moved in the direction of the combustion chamber.
• valve member 3 lifts off with its valve sealing surface 5 from the valve seat 9 and releases an inlet or outlet cross section 13 from a feed channel into the combustion chamber of the internal combustion engine, which is not shown in detail.
• the closing stroke movement of the valve member 3 takes place again by relieving the pressure in the upper working chamber 29 and filling the lower working chamber 25 with pressure, as a result of which the differential piston 18 and with it also the gas exchange valve member 3 is displaced again in the direction of the upper working chamber 29 until the valve member 3 with its valve sealing surface 5 rests sealingly on the valve seat 9.
• the mutual filling and relieving of the work spaces 25 and 29 takes place via solenoid valves in the pressure medium lines 31, 33, which are controlled as a function of operating parameters of the internal combustion engine via a control unit (not shown in more detail).

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Valve Device For Special Equipments (AREA)
• Fluid-Driven Valves (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=7870583

Family Applications (1)

Country Status (6)

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• 1998
  • 1998-06-12 DE DE19826046A patent/DE19826046A1/de not_active Withdrawn
• 1999
  • 1999-02-16 DE DE59906944T patent/DE59906944D1/de not_active Expired - Lifetime
  • 1999-02-16 US US09/485,540 patent/US6178935B1/en not_active Expired - Lifetime
  • 1999-02-16 EP EP99914421A patent/EP1029157B1/de not_active Expired - Lifetime
  • 1999-02-16 JP JP2000554968A patent/JP4395259B2/ja not_active Expired - Fee Related
  • 1999-02-16 WO PCT/DE1999/000423 patent/WO1999066177A1/de active IP Right Grant
  • 1999-02-16 KR KR1020007001396A patent/KR100570913B1/ko not_active IP Right Cessation

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