A multi-valve for a cooling system of a motor vehicle includes: a valve housing, which has a plurality of inlets and a plurality of outlets and delimits a cylindrical valve chamber, the plurality of inlets and the plurality of outlets opening into the cylindrical valve chamber; and a valve unit, which is arranged inside the cylindrical valve chamber of the valve housing and is rotatable about an axis of rotation between a plurality of switching positions by an actuator. Depending on a switching position of the valve unit, different inlets of the plurality of inlets are fluidically connectable to different outlets of the plurality of outlets. The valve unit has a plurality of fluid channel structures which are offset from one another in a circumferential direction. Each switching position of the plurality of switching positions is respectively assigned a fluid channel structure of the plurality of fluid channel structures.

A multi-valve for a cooling system of a motor vehicle includes: a valve housing, which has a plurality of inlets and a plurality of outlets and delimits a cylindrical valve chamber, the plurality of inlets and the plurality of outlets opening into the cylindrical valve chamber; and a valve unit, which is arranged inside the cylindrical valve chamber of the valve housing and is rotatable about an axis of rotation between a plurality of switching positions by an actuator. Depending on a switching position of the valve unit, different inlets of the plurality of inlets are fluidically connectable to different outlets of the plurality of outlets. The valve unit has a plurality of fluid channel structures which are offset from one another in a circumferential direction. Each switching position of the plurality of switching positions is respectively assigned a fluid channel structure of the plurality of fluid channel structures.

A method of improving corrosion resistance of a cylinder cover including a port that is an intake port or an exhaust port. The cylinder cover is configured such that an annular cooling water passage is formed between an inner peripheral surface of the port and a valve seat ring when the valve seat ring is inserted in the port. The method includes forming a weld overlay layer on each of sealed regions of the inner peripheral surface of the port by laser metal deposition using a welding material made of a nickel-based alloy, a copper alloy, stainless steel, or a titanium alloy, the sealed regions being positioned at both sides of the cooling water passage, respectively.

A valve seat insert includes a top convex arcuate blend for improving fluid flow, and a valve seating surface for slowing down valve recession. The valve seating surface includes a radially outer convex arcuate segment defining an outer radius of curvature forming a first wear crown for contacting the valve at an early wear state, a radially inner convex arcuate segment defining an inner radius of curvature forming a second wear crown for contacting the valve at a later wear state, and a linear segment extending between the radially outer convex arcuate segment and the radially inner convex arcuate segment.

A valve seat insert includes a top convex arcuate blend for improving fluid flow, and a valve seating surface for slowing down valve recession. The valve seating surface includes a radially outer convex arcuate segment defining an outer radius of curvature forming a first wear crown for contacting the valve at an early wear state, a radially inner convex arcuate segment defining an inner radius of curvature forming a second wear crown for contacting the valve at a later wear state, and a linear segment extending between the radially outer convex arcuate segment and the radially inner convex arcuate segment.

A method of improving corrosion resistance of a cylinder cover including a port that is an intake port or an exhaust port. The cylinder cover is configured such that an annular cooling water passage is formed between an inner peripheral surface of the port and a valve seat ring when the valve seat ring is inserted in the port. The method includes forming a weld overlay layer on each of sealed regions of the inner peripheral surface of the port by laser metal deposition using a welding material made of a nickel-based alloy, a copper alloy, stainless steel, or a titanium alloy, the sealed regions being positioned at both sides of the cooling water passage, respectively.

A device for producing at least one hollow valve for a gas exchange system may include at least one valve holder. The at least one valve holder may include a valve stem centring element, a valve receptacle and a valve head holder. The valve receptacle may receive a valve stem and the valve head holder may receive a valve head. A first carrier and a second carrier may be provided. The valve holder may be arranged on the first carrier. At least one cathode holder may be arranged on the second carrier. The cathode holder may include a cathode that is insertable through the first carrier via the valve stem centring element. At least one contact plate may be arranged opposite the valve head holder.

A device for producing at least one hollow valve for a gas exchange system may include at least one valve holder. The at least one valve holder may include a valve stem centring element, a valve receptacle and a valve head holder. The valve receptacle may receive a valve stem and the valve head holder may receive a valve head. A first carrier and a second carrier may be provided. The valve holder may be arranged on the first carrier. At least one cathode holder may be arranged on the second carrier. The cathode holder may include a cathode that is insertable through the first carrier via the valve stem centring element. At least one contact plate may be arranged opposite the valve head holder.

Internal combustion piston engine includes a cylinder head partly defining two ducts and a combustion chamber, and poppet valves movably arranged in the cylinder head between positions allowing or preventing flow between the combustion chamber and the ducts. The poppet valve has a stem, a valve head having a hollow interior space, a lower surface facing the combustion chamber, an upper surface including a portion adjacent the stem, and a peripheral edge section that extends from the upper surface of the valve head to the lower surface. The valve head is formed separate from but connected to the valve stem in a manner to enclose the hollow space, for example, by a circumferential welding seam. The peripheral edge section contains an arcuate contact surface that extends from the upper to lower surfaces of the valve head and without any sharp edges between upper and lower surfaces.

A poppet valve includes a head and a stem, which extends from the head. At least a part of the back of the head is covered by a cover with a heat insulating space provided in between. A support portion is provided between the cover and the head to support the cover on the head with rubber member having a lower heat conductivity than that of the head between the cover and the head.