Abstract: An internal combustion engine has an intake manifold injection, at least two combustion chambers, at least one central rail for supplying fuel for the intake manifold injection, and at least one air distributor for supplying air to the individual combustion chambers. The central rail is attached to the air distributor, or the central rail and the air distributor are formed as an integral component.

Abstract: The flexibility of the attachment angle and attachment interval of the member (e.g., injector) attached to the joint member is increased to improve the flexibility of layout even in the case of the forged rail for high-pressure direct injection. In addition, the manufacturing cost can be reduced while keeping high strength of the joint portion. A rail body 1 manufactured by forging, the rail body 1 having a through hole 4 opened on a wall surface 3 for communicating a fuel passage 2 extending in an axial direction with an outside; and a tubular joint member 6 manufactured separately from the rail 1 body and fixed to the rail body 1 at a position of the through hole 4 for allowing a fuel to flow from the fuel passage 2 through the through hole 4 are provided.

Abstract: Wakeboat hull control systems and methods are provided to monitor the orientation of the wakeboat hull in the surrounding water, and to automatically control wakeboat ballast components to achieve or maintain desired hull orientations. Systems and methods are provided to measure, store, and recall hull orientation. Systems and methods are also provided to enable automated action to improve the safety, automation, performance, convenience, and marketing advantage of wakeboat ballast systems.

Abstract: A system comprises a component manufactured via additive manufacturing. The component includes a first material with a first contraction rate. An insert is disposed in the component and comprises a second material with a second contraction rate that is lower than the first contraction rate. When the component and the insert are exposed to a temperature suitable for sintering, the component contracts around the insert, thereby coupling the insert and the component.

Abstract: A gas injector has an injector lance, a drive unit, a push rod and a valve. The injector lance has a free end for injecting gas into an external unit. The drive unit generates a linear movement of the push rod, as a result of which the push rod actuates the valve and exposes a valve through-passage opening, in order for the gas to be injected. The valve through-passage opening is arranged in the region of the free end of the injector lance ). The gas injector can be designed to be relatively small and narrow. It minimizes switching delays, avoids dead spaces and prevents contamination of the valve.

Abstract: The invention relates to an arrangement for connecting at least one fuel injection valve with a fuel distributor of a fuel injection system of an internal combustion engine, which fuel distributor is detachably fastened to a cylinder head, wherein the at least one fuel injection valve is detachably fastened by means of a fixing element to a mounting element of the fuel distributor. It is provided that a non-cylinder-facing surface of the mounting element of the fuel distributor and a cylinder-facing surface of the fixing element, in the assembled state of the cylinder head and fuel distributor and also the fuel injection valve, are configured as contact surfaces, by means of which, through attachment of the fixing element to the fuel injection valve, it is possible to bring about an axial fixing and a radial orientation of the fuel injection valve in the cylinder head and in the mounting element of the fuel distribution rail.

Abstract: A hand-guided power tool has an internal combustion engine that is arranged in a power tool housing and drives a tool member of the power tool. A fuel tank and at least one electric component are provided. A control device that is an electronic control unit is connected to the at least one electric component and controls the at least one electric component. The power tool has a top face which, when parking the power tool in a usual parking position on a flat horizontal support surface, is facing upwardly. The electronic control unit has a plug contact and a connecting plug is plugged into the plug contact. The connecting plug is connected by a connecting line to the at least one electric component. The connecting plug is arranged on a top side of the control device which is facing upwardly in the usual parking position of the power tool.

Abstract: Disclosed is a vehicle. The vehicle generally includes a frame to support an engine and one or more ground supports, such as wheels, to support the frame. The engine may include an internal combustion power plant and a fuel supply system therefore.

Abstract: A fuel pipe includes a tubular header pipe and a socket coupled to the header pipe and supplied with fuel from the header pipe. The header pipe and the socket form a joining portion therebetween. The joining portion is shaped to be elongated in a first direction. The joining portion includes a communication hole that connects an inner region of the header pipe and an inner region of the socket. The communication hole is an elongated hole elongated in the first direction.

Abstract: A leak detection tool for a double walled fuel rail system is provided. The tool includes a body having a first end and a second end distal with respect to the first end. The tool includes a first passage extending from the first end at least partially towards the second end. The tool includes a second passage axially aligned with and extending from the first passage towards the second end. The tool includes a seat defined at an intersection of the first passage and the second passage. The tool also includes a sealing element provided in association with the seat within the second passage. The tool further includes a spring element provided within the second passage and in contact with the sealing element. The first end is configured to block fluid communication between outer passages of adjacent portions of the double walled fuel rail system.

Abstract: An objective of the present invention is to provide a fuel rail that can be used at a high fuel pressure of 50 MPa or more, for example, has good engine mountability, and has improved material yield.

Abstract: Provided is a steel fuel conveying pipe with high quality which has high resistance to corrosive fuel and followability, and allows working after plating. The steel fuel conveying pipe is characterized in that a Ni-plate layer is formed on an inner surface of a steel pipe of base material, the Ni-plated layer is wholly composed of a mutual diffusion layer including the base material and Ni and a non-mutual diffusion layer including only Ni formed on an outermost surface of the diffusion layer, a layer thickness of the non-mutual diffusion layer is 3 ?m or more, and a total layer thickness of the mutual diffusion layer and the non-mutual diffusion layer is 10 ?m or more and 25 ?m or less.

Abstract: A tank lid includes: a lid main body that covers an opening portion of a fuel tank; a metal terminal that is for electrical driving and penetrates through the lid main body between an inside and an outside of the fuel tank; a connector that includes an outer tubular portion, which projects from a lid front surface to the outside of the fuel tank, while a bottomed tubular inner surface of the outer tubular portion surrounds the metal terminal; and a resin coating film that is acid resistant and is dielectric. The resin coating film is formed by dry coating through chemical vapor deposition on: an outer exposed surface of the outer tubular portion, which includes the bottomed tubular inner surface of the outer tubular portion as a surface exposed to the outside of the fuel tank; and the lid front surface.

Abstract: An accumulator clamp for an accumulator assembly in an engine assembly is disclosed. The accumulator assembly further includes an accumulator body and a fuel line adapter connected thereto, and the accumulator assembly is mountable into a cylinder head accumulator bore of a cylinder head. The accumulator clamp includes a clamp body having a clamp accumulator bore receiving an end of the accumulator body, and a bolt bore on either side of the clamp accumulator bore for receiving threaded portions of accumulator mounting bolts that secure the accumulator assembly to the cylinder head. The bolt bores include bolt slots through the walls of the accumulator body so that the threaded portions of the accumulator mounting bolts are insertable into and removable from the bolt bores through the bolt slots to allow installation and removal of the accumulator assembly without disassembling components of the engine assembly around the cylinder head.

Abstract: A cylinder block including: a plurality of cylinders; a cylinder head attached on the cylinder block and including, for each of the cylinders, an intake port extending from a combustion chamber upward and obliquely relative to an axis of the cylinder; a direct injector disposed at a position on an outer side of the intake port in a cylinder radial direction and directly injecting fuel into the combustion chamber; a port injector disposed at a position on a same side as the direct injector relative to the intake port, and injecting fuel into the intake port are provided. The intake port includes: a valve seat provided at an intake air inlet opened to the combustion chamber; and an arc portion protruding downward in a center area of the intake port on an upstream side of the valve seat, and an injection direction of the port injector is orientated in a direction in which the fuel injected from the port injector passes through a lower area of the arc portion.

Abstract: A hand-guided power tool has a power tool housing and an internal combustion engine arranged in the power tool housing and configured to drive a tool member of the power tool. A fuel tank and at least one electric component are provided. A control device that is an electronic control unit is connected to the at least one electric component of the power tool and controls the at least one electric component. The power tool has a top face which, when parking the power tool in a usual parking position on a flat horizontal support surface, is facing upwardly. The electronic control unit is positioned laterally adjacent to the fuel tank device, when viewing the power tool in the usual parking position.

Abstract: A method for manufacturing an injector having an extrusion coating, including the following steps: providing an injection module, pushing a disk-shaped alignment element onto a part of the injection module, the alignment element having a slot in order to have sufficient flexibility, welding the alignment element onto the part of the injection module, at least part of the slot also being welded shut at the same time during the welding-on step in order to stiffen the alignment element, and molding the extrusion coating onto the injection module.

Abstract: The invention relates to an anti-rotation device of a fuel lance arranged in a bore extending through a cylinder head of a cylinder head from an intake opening until a hole provided for receiving a fuel injector, the lance allowing high-pressure fuel to circulate from an intake opening of the lance until the outlet opening of the lance engaging with the intake opening of the fuel injector, the fuel lance including a nut for being screwed into the intake opening of the bore and a tubular member compressed between the nut and the injector, the lance also including the anti-rotation device. The anti-rotation device is a resilient element which is deformed by rotation of the nut, such as to be blocked between the tubular member and an inner wall of the bore, and thus prevent rotation of the tubular member when the nut is screwed.

Abstract: A metal fastener is provided having a first threaded screw portion for engaging a complementary threaded portion of a bore of a metal member at a first temperature, and a sealing portion disposed proximal a distal end of the first screw portion, the sealing portion having a greater coefficient of thermal expansion than the metal member, wherein the sealing portion is configured to thermally expand and provide a seal between the sealing portion and an inner circumference of the bore at a second temperature higher than the first temperature, such that the first screw portion of the fastener is immobile relative to the bore at the second temperature.

Abstract: A fuel injector rail for supplying fuel to at least one fuel injector. The fuel injector rail includes a delivery pipe, an injector port, and a flow director. The delivery pipe defines a fuel passage therein. The delivery pipe defines an injector port that fluidly that couples the fuel passage to the at least one fuel injector. The flow director is located in the fuel passage at a surface opposite to the injector port. The flow director guides a flow of fuel to the injector port.

Abstract: A distal end portion of an injector is fitted into a mounting member. A fuel joint having a connecting pipe portion is connected to a proximal portion of the injector. A joint pressing member which restricts the displacement of the fuel joint in the direction away from the mounting member is fixed by fastening to the mounting member. The injector is fixed to the mounting member by restricting the displacement of the fuel joint by the joint pressing member.

Abstract: An injection valve may have a nozzle body with a longitudinal axis, in which a nozzle body aperture and at least one injection opening are arranged, wherein the nozzle body aperture can be coupled hydraulically to a high-pressure circuit for a fluid, at least one nozzle needle arranged in an axially movable manner in the nozzle body aperture, wherein the nozzle needle prevents fluid flow through the at least one injection opening in a closing position and allows fluid flow through the at least one injection opening outside the closing position, an actuator housing, which is designed to accommodate an actuator designed to act on the nozzle needle, and at least one fluid line, which is designed for hydraulic coupling to the high-pressure circuit for the fluid and is constructed and arranged separately from the actuator housing, and is directly coupled hydraulically to the nozzle body aperture.

Abstract: Provided is a terminal structure of a high-pressure fuel pipe for a direct injection engine which can prevent stress concentration to a brazed portion between a pipe and a connection part effectively. In the terminal structure of a high-pressure fuel pipe for a direct injection engine where a connection head is brazed to an end of a fuel pipe, the end of the fuel pipe continued to a fuel pipe insertion portion of the connection head is provided with a drawn portion, an outer diameter D1 of the drawn portion to a fuel pipe diameter D satisfies 0.8D?D1?0.9D, and a length L1 of the drawn portion having the outer diameter D1 in a pipe-axial direction from an end of the fuel pipe insertion portion satisfies L1?0.06D.

Abstract: An injector mount for mounting an injector adjacent a curved fluid flow path includes an inner surface defining a boundary of the curved fluid flow path and an aperture between the inner surface and an outer surface. The aperture is configured to receive an injector. The inner surface includes a peripheral region, a central region recessed relative to the peripheral region, and an intermediate region including a convex surface that joins an inner edge of the peripheral region to an outer edge of the central region.

Abstract: Various embodiments relating to controlling a fuel injection quantity of a fuel injector are provided. In one embodiment, a fuel injector for an internal combustion engine includes a fuel supply channel, a nozzle valve including a valve stem, and an actuator to actuate the nozzle valve. The nozzle valve and an inner wall of the fuel supply channel form a first flow cross section and at least one second flow cross section that is greater than the first flow cross section.

Abstract: Provided is a terminal structure of a high-pressure fuel pipe for a direct injection engine which can prevent stress concentration to a brazed portion between a pipe and a connection part effectively. In the terminal structure of a high-pressure fuel pipe for a direct injection engine where a connection head is brazed to an end of a fuel pipe, the end of the fuel pipe continued to a fuel pipe insertion portion of the connection head is provided with a drawn portion, an outer diameter D1 of the drawn portion to a fuel pipe diameter D satisfies 0.8D?D1?0.9D, and a length L1 of the drawn portion having the outer diameter D1 in a pipe-axial direction from an end of the fuel pipe insertion portion satisfies L1?0.06D.

Abstract: In order to constitute a fuel high-pressure pipe that is compact and easy to connect to injectors, one of both the end sections of a fuel high-pressure pipe is formed as a first connecting section connected to a fuel supply port of one injector, and the other one of the end sections of the fuel high-pressure pipe is formed as a second connecting section connected to a fuel discharge port of another injector. The first connecting section and the second connecting section are linearly formed parallel to each other, and head sections of the first connecting section and the second connecting section, said head sections being on the connecting side to respective injectors, are formed in the directions opposite to each other.

Abstract: A fuel line, in particular a fuel line for a gasoline direct injection line system, having an inner steel tube and an outer steel tube, wherein the inner steel tube is accommodated in the outer steel tube in a force-locking manner. The inner steel tube is made of a corrosion resistant steel and the outer steel tube is made of an outer steel tube alloy, wherein a wall thickness of the inner steel tube is smaller than a wall thickness of the outer steel tube. A maximum carbon content of the outer steel tube alloy is higher than a maximum carbon content of the corrosion resistant steel. A thickness of the fuel line amounts to between 5% and 60% of an inner diameter of the motor vehicle fluid line.

Abstract: A fluid injector includes a housing and an inlet tube having a portion received in the housing. A primary seal creates a seal between surfaces of the housing, the inlet tube, and an inlet of the injector. A groove is in the housing and a secondary seal is in the groove to defining a seal between the housing and a portion of the inlet of the injector. A recessed portion is defined in the housing and is in communication with the groove. The recessed portion defines a blow-out volume such that when the primary seal is leak tested, an indication of a leak of the primary seal can be detected when the pressurized air moves past the primary seal and forces a portion of the secondary seal to an unsealed position into the blow-out volume.

Abstract: The present invention refers to a fuel rail made of plastic material with a heating system (10,100). The said rail is applied, mainly, in the form of devices for aiding the cold start of engines which consume fuels whose specific vaporization heat is high, for example, alcohol. The fuel rail made of plastic material with a heating system presents reduced cost and weight and the same functional characteristics if compared to the fuel rails known by the state of the art, which are usually made of metal. Furthermore, the said fuel rail made of plastic material with a heating system presents internal compartments configured in such a manner that the sliders containing slide pins (51, 52, 53) of the injection mold can be easily removed, since there is no formation of negative faces.

Abstract: A needle for use in a needle valve, such as the needle valve of a fuel injector, comprises a tip section (2), a first guide section (1a) and a second guide section (3). The tip section (2a) has a needle tip. The first guide section (1a) is remote from the needle tip. The second guide section comprises a tube, wherein the first guide section (1a) and the tip section (2a) are comprised in an integrated inner needle component (7) extending through the tube (3). A method of manufacturing such a needle is also described.

Abstract: A connection arrangement for a fuel line. The fuel line has a pressure nipple having a forward a sealing surface and a rear pressure receiving surface. A cap screw element projects into the passage with a tube portion which when tightened exerts on a pressure transmission arrangement a force which is directed axially towards the nozzle holder and which is transmitted to the pressure receiving surface of the pressure nipple to press its sealing surface against a counterpart sealing surface on the nozzle holder. A sealing arrangement which seals off a first free space between the outside wall of the fuel line and the inside wall of the pressure transmission arrangement and a second free space between the outside wall of the pressure transmission arrangement and the inside wall of the passage relative to the exterior is positioned completely in the interior of the passage.

Abstract: A quill tube is provided. The quill tube includes a hollow body and a spherical head. The hollow body defines a bore within the quill tube. The bore is configured to direct a flow of fuel into a fuel injector. The spherical head is located at a first end of the hollow body. The spherical head includes a tip, a first surface and a second surface. The tip is located at a distal end of the spherical head. The first surface is configured to engage with the fuel injector. The second surface is positioned between the tip and the first surface. Further, a flange is located proximate to the spherical head. The flange is angularly positioned relative to the first surface. If the spherical head is contacted against an external surface, the flange is configured to cause the second surface to touch the external surface.

Abstract: A method for cooling an ECU and an ECU or ECU module mounted to be cooled by fuel flow through a fuel rail. In a preferred embodiment, the ECU has a decentralized distributed processing configuration, with a main ECU module and at least one remote module. The remote ECU module is packaged in an assembly with an elongate hollow metal fuel rail having injector seats. Fuel injectors are received into and seal against the seats and are supplied with fuel via the fuel rail. A printed circuit board carries electronic ECU components. One or more connector assemblies are connected to printed circuit board for electrically connecting the ECU circuitry and may pass through notches formed in the fuel rail. The electronics are potted and mounted to the fuel rail. A thermally conductive wetting compound may be disposed between the electronic assembly and the fuel rail.

Abstract: A dual fuel common rail engine supplies pressurized natural gas and liquid diesel fuel at different pressures through a co-axial quill assembly for direct injection from a single fuel injector into an engine cylinder. Each coaxial quill assembly includes a matched pair of inner and outer quills that are chosen to have dimensions that allow both quills to sealingly engage each fuel injector at a common conical seat responsive to a clamping force applied along an axis. Matched pairs of inner and outer quills are retained together during pre-installation handling with a retainer that is left between the inner and outer quills after installation in an engine.

Abstract: A dual fuel common rail engine supplies pressurized natural gas and liquid diesel fuel at different pressures through a co-axial quill assembly for direct injection from a single fuel injector into an engine cylinder. Pressure waves in the gaseous fuel common rail are damped in a pressure damping chamber of the co-axial quill assembly before the pressure wave can undermine consistent gaseous fuel injection rates and quantities from the fuel injector.

Abstract: A device for the discharge of urea solution into an exhaust gas conduit (40) includes an injection nozzle (2) with a conduit connection (14) for the supply of urea solution, and a nozzle head which is conductively connected thereto. The urea solution may be supplied to an exhaust gas flow in a finely distributed manner by way of the nozzle head. Furthermore, the device includes a receiver (42), which surrounds an opening (46) in the exhaust gas conduit wall (44) and which is designed for the tight bearing of the nozzle head and for the releasable fastening of the injection nozzle (2). Moreover, a spring is provided for the non-positive fit bearing of the nozzle head in the receiver (42).

Abstract: A fuel feed device for attachment to a cylinder head of an internal combustion engine has at least one fuel distribution element extending along a longitudinal direction, and at least one connecting element extending transversely to the longitudinal direction, wherein the connecting element can be used to connect the fuel distribution element to the cylinder head. The fuel feed device further includes at least one reinforcing element which is connected, on one hand, to an outer surface of the fuel distribution element and, on the other hand, to the connecting element outside the fuel distribution element.

Abstract: This disclosure provides a fuel system for supplying fuel to an internal combustion engine, an internal combustion engine that includes such a fuel system, a connector for connecting a single-walled high pressure common rail to a double-walled fuel line segment, and a fluid containment system. Each embodiment includes drain plumbing having a leakage drain connector that can be used to provide an interface between a single-walled high pressure common rail and a double-walled high pressure fuel line segment, and also provide part of a low pressure passage fluidly connected with a low pressure passage of the double-walled high pressure fuel line segment. The drain plumbing also can provide an interface with a low pressure fuel drain line fluidly coupled to a leakage detector.

Abstract: A coaxial quill assembly is used for supplying gaseous and liquid fuels from separate common rails to individual fuel injectors of a compression ignition engine. Each coaxial quill assembly includes a matched pair of an outer quill and an inner quill that are matched based upon a fuel system dimensional specification that causes both the inner and outer quills to sealingly engage a common conical seat of a fuel injector. During pre-installation handling, the matched pair of inner and outer quills are retained together with a retainer.

Abstract: The invention relates to a multiple-layer fuel line, comprising an inner layer which comes into contact with the fuel and an other layer which forms the outer surface of the fuel line and is formed from a polyamide. According to the invention, the inner layer comprises polyethylene.

Abstract: An engine includes a head cover covering an upper part of a cylinder head to accommodate a valve gear mechanism and an injector. The head cover is separatable into a lower cover body and an upper cover body detachable from and attachable to the lower cover body. The lower cover body includes a fuel pipe and a relay connector. Through the fuel pipe, fuel is supplied to the injector. The fuel pipe penetrates through the lower cover body. The relay connector is configured to relay power supply from outside the head cover. The relay connector is attached to the lower cover body. One end side of an injector harness disposed in the head cover is coupled to a terminal portion of the injector. Another end side of the injector harness is coupled to the relay connector.

Abstract: A method is described for adjusting the amount of gaseous fuel injected based on the sonic choked flow rate through a restriction. Because the sonic choke flow rate continues to decrease as tank pressure decreases, the method includes computing the sonic choke flow rate through the restriction based on system variables and enforcing the rate of CNG injection to be less than the sonic choke flow rate through the restriction. Thereby, the mass flow rate to the fuel injector can be substantially maximized to substantially minimize the time for fuel tank emptying, particularly during the last amount of tank emptying when the contents of the gaseous storage tank is low.

Abstract: System for supplying fuel from a tank (2) to a manifold (5) that distributes fuel into an engine (3); the system (1) having a pumping unit which connects together the tank (2) and the manifold (5) and has a fluid line (11) with a first or low-pressure portion (P1), a second or high-pressure portion (P2), a high-pressure pump (9) connecting together the first and second portions (P1, P2); the first portion (P1) having a plurality of low-pressure branches (23-28, 30-34), a plurality of fluid components (8, 13, 21, 29, 231, 232, 233, 241, 242, 251, 261, 271, 311), each of which has at least one connector (36) and at least one tubular coupling (40; 140; 340; 440), which latter is inserted partly into the connector (36) and partly into a low-pressure branch (23-28; 30-34); each coupling (40; 140; 340; 440) having a plastic tubular body (145; 345; 445).

Abstract: A delivery pipe is molded of resin and internally formed with a fuel passage. The delivery pipe has a shape of cross section including a single straight part, a single curved part, and joint parts at joints between ends of the straight part and the curved part. The joint part has an outer appearance protruding outward. The resin contains reinforcing glass fibers. A corresponding portion to a resin injection gate is located at an end region of the straight part in a longitudinal direction of the fuel passage.

Abstract: A refueling system includes a filling station configured to store a first volume of liquid fuel, the filling station including a station receptacle, a removable fuel cartridge configured to store a second volume of liquid fuel less than the first volume of liquid fuel, and outdoor power equipment including an engine having an engine receptacle, wherein inserting the removable fuel cartridge into the station receptacle fluidly couples the filling station and the removable fuel cartridge to automatically fill the removable fuel cartridge with liquid fuel, and wherein inserting the removable fuel cartridge into the engine receptacle fluidly couples the removable fuel cartridge and the engine to provide liquid fuel to the engine.

Abstract: A duel fuel quill assembly and method for assembling such an assembly for an engine are disclosed. The dual fuel quill assembly may comprise a cylinder head including a main bore and a receiving cavity, an outer quill tube, an inner quill tube nested within the outer quill tube, an adapter slidingly received inside the main bore of the cylinder head, and a manifold secured to the adapter. The adapter may be moveable between a first position and a second position and may define an axial bore configured to receive the outer quill tube and the nested inner quill tube. The manifold may define a recess configured to compress the outer and inner quill tubes against the cylinder head cavity when the adapter is in the second position.

Abstract: A charge pipe passage includes a second pipe passage part which is connected to a fuel tank by way of a first pipe passage part and extends toward the other side from one side in the vehicle widthwise direction, and a third pipe passage part which is communicably connected with the second pipe passage part on the other side in the vehicle widthwise direction and has a highest part arranged at a highest position of the charge pipe passage at an intermediate position thereof. A first check valve is interposed on the third pipe passage part downstream of the highest part, an atmospheric air introducing pipe passage is connected to the third pipe passage part upstream of the first check valve, and a second check valve is interposed on the atmospheric air introducing pipe passage at a position higher than the highest part.

Abstract: A vibration isolation fuel rail mounting arrangement is configured for in-plane shear type damping by spacing the mid-width points of the elastomer compression areas of two stacked-layer isolators away from the central fastener axis by a distance between about 1.5 times the bolt diameter and about 3.0 times the bolt diameter.

Abstract: The invention relates to an unheated fuel-line assembly, in particular for use in a motor vehicle, where an inner tube is provided as a fuel line and an outer tube is provided that surrounds the inner tube with a spacing therefrom. The inner surface of the outer tube that faces toward the inner tube is formed with a plurality of grooves that extend at least over a portion of the length of the outer tube longitudinally of the outer tube.