A hydraulic tensioning device for a chain drive, including tensioning piston, which is guided in a holder and which has locking grooves on the outer peripheral surface of the tensioning piston, and including a locking element, which has at least two annular sections and at least two radial extensions, wherein the locking element can be brought into engagement with one of the locking grooves by the at least two annular sections, and including a clamping stop and a sliding stop, which are axially spaced apart from each other. In order to simplify the design, the holder has at least two axial extensions, which extend in the axial direction between the clamping stop plane and the sliding stop plane. The at least two axial extensions and the tensioning piston do not enclose the at least two radial extensions.

A hydraulic tensioning device for a chain drive of an internal combustion engine, having a receptacle and having a tensioning piston which is guided in displaceable fashion in a cylindrical hollow space of the receptacle and which has a piston hollow space, wherein the piston hollow space together with the cylindrical hollow space of the receptacle forms a pressure chamber, and having a pressure relief valve unit arranged in the piston hollow space. The pressure relief valve unit is a preassembled structural unit and comprises a spring, a closing body and a valve seat and also a valve receptacle which surrounds the valve seat in a first subsection, wherein the valve receptacle forms an interference fit with the valve seat, and wherein the valve receptacle or the valve seat in a second subsection form an interference fit with the inner shell surface of the tensioning piston.

A tensioner which adjusts the mean tensioner force to keep the chain tension as low as possible without sacrificing chain control, significantly improving drive efficiency as the chain wears and is subject to low dynamic loads.

A fixing tool of an auto-tensioner includes inwardly inclined engaging pieces inclined inwardly so as to be opposed to respective tapered surfaces of a spring seat and a cylinder of the auto-tensioner. The engaging pieces have concave surfaces that contact the tapered surfaces over a circumferentially extending area. This minimizes the deformation of the engaging pieces such that the diametrical distances therebetween increase due to contact with the tapered surfaces when sandwiching the spring seat and the cylinder with the engaging pieces from the axially opposite directions, thereby preventing the fixing tool from coming off.

A chain guide and tensioning apparatus is disclosed that is configured for engagement (contact) with a driven chain (e.g., in an automotive engine). The chain guide and tensioning apparatus includes a guide body and a guide face overlying the guide body. The guide face defines an inner surface and an opposite outer surface that is configured to guide and tension the driven chain. The guide face includes a plurality of spacers that extend therefrom into engagement (contact) with the guide body so as to define at least one channel that is configured to facilitate air and/or lubricant circulation between the guide body and the guide face to reduce heat and friction generated by engagement of the driven chain with the guide face.

An orifice member is disposed in a plunger including a plunger hole that forms a hydraulic chamber in conjunction with a plunger housing hole in a housing. The orifice member includes a deformed fitting section deformed to fit on the inner circumferential surface of the plunger hole, a communication section that causes a surface in contact with the top surface on the front side of the plunger hole and a surface on the hydraulic chamber side to communicate, and an orifice groove that communicates with the communication section and an external relief hole provided in the plunger on the surface in contact with the top surface on the front side of the plunger hole to constitute an orifice.

The gasket includes a gasket body which is made of a monolithic piece of an elastomeric material. The gasket body has an oil opening for allowing oil to pass between the timing chain tensioner and a cylinder head. The gasket body includes at least one outer engagement feature for directly engaging with an outer wall of the timing chain tensioner to hold the gasket body on the timing chain tensioner. The gasket body also includes at least one inner engagement feature for directly engaging with an inner wall of the timing chain tensioner to further hold the gasket body on the timing chain tensioner.

To provide a tensioner and a relief valve unit that enable a reduction in the number of parts to be processed and the number of assembling steps, reduce the amount of oil flowing out to the outside, prevent damage to the check valve, and improve the oil recovery rate. The relief valve unit that releases oil when pressure inside an oil pressure chamber reaches or exceeds a predetermined high pressure includes a check valve unit that stops reverse flow of oil flowing into the oil pressure chamber as a valve element, the check valve unit being slidably inserted in the relief valve unit. The relief valve unit includes a unit pressing spring that presses the check valve unit toward a relief valve seat. The check valve unit includes an oil passage for allowing oil to flow between an inner side and an outer side of the check valve unit.

A chain tensioner is formed with internal threads each including a push-in-side flank, a protruding-side flank , and a thread top face. The push-in-side flank has a flank angle larger than the flank angle of the protruding-side flank. The push-in-side flank and the protruding-side flank are rolled surfaces formed by rolling, and have a surface roughness smaller than Ra 1.0 μm. Each internal thread further includes, at its position at which the protruding-side flank intersects with the thread top face, a chamfer configured to receive a bulge moving from the protruding-side flank during rolling.

A valve unit for a tensioning device of an endless drive is provided, in particular a chain drive of an internal combustion engine, with a carrier plate having an underside forming a contact surface and an upper side which can be faced towards a pressure chamber of the tensioning device, and a valve body which is guided in a receptacle movably relative to the carrier plate for opening and closing a valve seat of the tensioning device. Such a valve unit is to be simplified and more cost-saving. The receptacle is formed by the carrier plate and a suspension device is provided in the region of the receptacle on which the valve body is suspended from the carrier plate in a lowermost position. The carrier plate is horizontal in the non-installed state of the tensioning device, such that the valve body projects downwardly out of the receptacle and is movable upwardly by at least the opening stroke. The invention relates to a corresponding hydraulic tensioning device.