GB2545189A

GB2545189A - Screw for sealing a bore

Info

Publication number: GB2545189A
Application number: GB1521580.9A
Authority: GB
Inventors: Guisasola Inigo
Original assignee: Caterpillar Energy Solutions GmbH
Current assignee: Caterpillar Energy Solutions GmbH
Priority date: 2015-12-08
Filing date: 2015-12-08
Publication date: 2017-06-14
Anticipated expiration: 2035-12-08
Also published as: GB201521580D0; GB2545189B

Abstract

Screw 14 for sealing a hole 13 in a cylinder head 2, the screw including a longitudinal axis and a screw tip asymmetric with respect to the longitudinal axis. The screw may feature an angled planar surface at the tip and may be threaded into a cylinder head so that angled surface aligns with an internal surface of the cylinder head. The bolt 14 may feature an element (26, figure 4; 26a, figure 6) on its head to indicate its angular alignment. The cylinder head may feature a recess (29, figure 4; 29, figure 6), into which an asymmetric washer or a key may be placed to prevent angular movement of the screw. The screw may be used to seal an inspection bore of an endoscope.

Description

SCREW FOR SEALING A BORE

Technical Field [0001] The present disclosure is directed to a screw for sealing a bore in a cylinder head, a cylinder head and a method to seal a bore.

Background [0002] Internal combustion engines, such as engines using gaseous fuel, have in general at least one combustion chamber, where the fuel is ignited and combusted. The combustion chamber may be defined by a cylinder or a cylinder liner, a reciprocating motion piston, which is positioned in the cylinder or the cylinder liner and a cylinder head. The cylinder head covers the top of the combustion chamber, where the piston defines the lower end of the combustion chamber. Inspection bores are used to inspect the combustion chamber while the engine is fully assembled. The inspection bores are positioned in the cylinder head and extend from an outer side of the cylinder head facing the outside of the engine to a lower side of the cylinder head facing the combustion chamber. Such bores in cylinder heads may be used to inspect the combustion chamber of an internal combustion engine without removing the cylinder head and/or the cylinder from the combustion engine. For inspection, endoscopes are inserted into the combustion chamber through the bore in the cylinder head. The endoscope may include a light source to light the combustion chamber and an optical device like a conductor or a camera to transport an optical image of the combustion chamber to the outside of the engine.

[0003] During operation of the engine, the bore must be sealed to prevent the fuel, exhaust, pressure etc. from escaping the combustion chamber through the bore. The term “to seal” means in this disclosure to stop and/or to reduce the flow of a fluid like gaseous fuel, air and/or exhaust through the bore. To seal the bore screws may be used, which are inserted into the bore. The screws may have a threaded cylindrical body and an element at the screw head for turning the screw. Such element may be a slit to insert a top of a screwdriver or a hexagonal screw head to connect a wrench to the screw.

[0004] A fuel-air mixture in the combustion chamber is ignited by ignition means like a spark plug. The ignited fuel combusts and ignites the surrounding fuel. This may result in a combustion of all fuel in the combustion chamber.

[0005] A residual volume defined by that part of bore which is not filled by the screw and is open to the combustion chamber will be filled with fuel during operation of the engine, for example during the compression stroke. This fuel may not be ignited and combusted, as the volume is not directly in the stream of the ignited fuel in the combustion chamber but only connected to the combustion chamber by a relative small opening of the bore. This results in an increased amount of unbumed fuel in the exhaust as this unburned fuel may also be expelled from the combustion chamber during the exhaust stroke. To minimize the size of the volume, screws may be used with a flat tip opposite to the screw head. Such screw may be inserted into the bore, so the flat tip aligns with the lower plane of the cylinder head and the open volume defined by the cylinder head and the screw tip is minimized.

[0006] As there are multiple elements, like two inlet valves, two outlet valves, a spark plug and a fuel injector, positioned at the cylinder head on top of the combustion chamber, it might not be possible to position the bore rectangular to the lower plane of the cylinder head, so the bore is positioned inclined to the lower plane of said cylinder. When sealing the inclined bore with a flat tipped screw the residual volume may be significant, which increases the amount of unbumed fuel in the exhaust.

[0007] The present disclosure is directed to reduce the residual volume defined by the bore.

Summary of the Disclosure [0008] In a first aspect of the present disclosure a screw is provided to seal a bore in a cylinder head. The screw has a longitudinal axis and a screw tip, which is asymmetric in respect to the longitudinal axis.

[0009] According to a second aspect of the present disclosure a method is provided to seal a bore in the cylinder head by a screw. The method comprises the steps of inserting the screw in the bore, retracting the screw until a planar surface at the top of the screw is parallel to the plane of the cylinder head facing the combustion chamber and fixating the screw in that position.

[0010] Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.

Brief Description of the Drawings [0011] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate exemplary embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure. In the drawings: [0012] FIG. 1 shows an internal combustion engine with a bore in the cylinder head; [0013] FIG. 2 shows a first embodiment of a screw in the cylinder head; [0014] FIG. 3 shows a second embodiment of a screw to seal a bore in the cylinder head; [0015] FIG. 4 shows the screw according to FIG. 3 positioned in the cylinder head; [0016] FIG. 5 shows a third embodiment of a screw to seal a bore in the cylinder head; [0017] FIG. 6 shows the screw according to FIG. 5 to seal the bore in the cylinder head.

[0018] FIG. 7 shows a method to mount the screw according to FIG. 3 and 4: [0019] FIG. 8 shows a method to dismount the screw according to FIG. 3 and 4 [0020] FIG. 9 shows a method to mount the screw according to FIG. 5 and 6..

Detailed Description [0021] The following is a detailed description of exemplary embodiments of the present disclosure. The exemplary embodiments described therein and illustrated in the drawings are intended to teach the principles of the present disclosure, enabling those of ordinary skill in the art to implement and use the present disclosure in many different environments and for many different applications. Therefore, the exemplary embodiments are not intended to be, and should not be considered as, a limiting description of the scope of patent protection. Rather, the scope of patent protection shall be defined by the appended claims.

[0022] FIG. 1 shows an internal combustion engine 1. Such an internal combustion engine 1 may be a reciprocating piston engine like an engine operating on gaseous fuel, a diesel engine, a dual fuel engine etc. The engine 1 has a cylinder head 2, an engine body 3, a combustion chamber 4 and a piston 5. The cylinder head 2 may comprise inlet manifolds 6 to supply the combustion chamber 4 with fuel and/or air and outlet manifolds 7 to guide exhaust from the combustion chamber 4. Further the cylinder head 2 forms a bay 8 to hold a spark plug 9. A lower surface 10 of the cylinder head 2 faces the combustion chamber 4 of the internal combustion engine 1.

[0023] The engine body 3 holds a cylinder 11 and is adjacent to the lower plane 10 of the cylinder head 2. In the cylinder 11 the piston 5 is positioned in a manner such that the piston 5 can be moved reciprocally in the cylinder 11. The combustion chamber 4 is defined by the lower plane 10 of the cylinder head 2, the cylinder 11 and a piston crown 12 of the piston 5.

[0024] For inspecting the combustion chamber 4 after the engine 1 has been assembled, the cylinder head 2 features a bore 13, through which an endoscope may be inserted into the combustion chamber 4. The bore 13 is inclined to the lower surface 10 of the cylinder head 2, so the bore 13 extends from the combustion chamber 4 to an outer surface 40 of the cylinder head 2. The bore 13 is sealed by a screw 14, which is inserted in the bore 13.

[0025] As shown in FIG. 2 the screw 14 may be positioned in the bore 13. The screw 14 may have an at least partly threaded first cylindrical body 15, which also defines the longitudinal axis 16 of the screw 14. A screw head 17 of the screw 14 is arranged at a first end of the first cylindrical body 15 of the screw 14 and protrudes sideways from the first cylindrical body 15.

[0026] A screw tip 18 is positioned on the first cylindrical body 15 opposite to the screw head 17. The screw tip 18 is asymmetric with respect to the longitudinal axis 16 and has a planar surface 19, which extends over the full diameter of the first cylindrical body 15. An angle alpha between the longitudinal axis 16 of the screw 14 and the planar surface 19 of the screw 14 corresponds with an angle beta between the longitudinal axis 20 of the bore 13 and the lower surface 10 of the cylinder head 2. When the screw 14 is inserted into the at least partly threaded bore 13 the longitudinal axis 16 of the screw 14 corresponds to the longitudinal axis 20 of the bore 13. The thread of the first cylindrical body 15 corresponds with the thread of the bore 13, so the thread of the first cylindrical body 15 may mesh with the thread of the bore 13.

[0027] The planar surface 19 of the screw 14 is facing, when inserted into the bore as intended, the combustion chamber 4 and may align with the lower surface 10 of the cylinder head 2.

[0028] FIG. 3 shows another embodiment of the screw 14 to seal the bore 13 in the cylinder head 2. The screw 14 includes the first cylindrical body 15 with the screw tip 18. The screw tip 18 comprises the planar surface 19, which faces the combustion chamber 4. A second cylindrical body 21 is arranged adjacent to the first cylindrical body 15 and positioned on an end of the first cylindrical body 15 opposite to the screw tip 18. The second cylindrical body 21 comprises threaded sidewalls 22. The second cylindrical body 21 protrudes from the first cylindrical body 15 in a direction rectangular to the main axis 16 of the screw 14. When the screw 14 is in a sealing position, the threaded side walls 22 mesh with threaded inner walls 23 of the bore 13 and a lower surface 24 of the second cylindrical body 21 is positioned above and/or abuts an upper surface 38 of a step 25 formed by the cylinder head 2 in the bore 13.

[0029] Adjacent to a top surface 36 of the second cylindrical body 21 opposite to the first cylindrical body 15 an asymmetric body 26 is positioned. The asymmetric body 26 may be form one piece with the first cylindrical body 15 or may be fixed permanently or detachable to the first cylindrical body 15. The asymmetric body 26 is rotationally asymmetric in respect to the longitudinal axis 16. The asymmetric body 26 may be hexagonal, rectangular, star-shaped etc. A washer 27 with an opening 28 is positioned around the asymmetric body 26. The opening 28 of the washer 27 comprises an inner contour 41 which corresponds to an outer contour 34 of the asymmetric body 26. An outer contour 39 of the washer 21 is rotationally asymmetric with respect to the longitudinal axis 16 of the screw 14. The outer contour 39 of the washer 27 may comprise a protrusion 35, which corresponds to an inner contour 42 of a recess 29 in the cylinder head 2, so the protrusion 35 may be positioned as a whole or parts thereof in the recess 29 of the cylinder head 2.

[0030] Next to the asymmetric body 26 along the longitudinal axis 16 is a threaded body 30 with threaded sidewalls 31. In a sealing position of the screw 14, the threaded body 30 protrudes from the cylinder head 2. A nut 32 may be positioned around the threaded body 30 and abut an upper surface 33 of the cylinder head 2.

[0031] FIG. 4 is a top view of the screw 14 in the cylinder head 2 as previously shown in FIG. 3. The asymmetric body 26 of the screw 14 has a cylindrical outer contour 34 with a planar surface 35 at one side. Other asymmetric shapes of the outer contour 34 may be possible. The shape of the opening 28 of the washer 27 may correspond to the shape of the outer contour 34 of the asymmetric body 26. The inner contour 41 of the washer 27 meshes with the outer contour 34 of the asymmetric body. The outer contour 39 of the washer 27 may comprise a protrusion 35 which corresponds to the recess 29 in the cylinder head 2.

[0032] A nut 32 is placed on the threaded body 30 of the screw 14 on top of the washer 27 and the asymmetric body 26 and abuts the outer surface 33 of the cylinder head 2.

[0033] Fig. 5 shows another embodiment of a screw 14. The screw 14 comprises a first cylindrical body 15 with a planar surface 19 at the tip. Along the longitudinal axis 16 of the screw 14 the second cylindrical body 21 may be attached to the first cylindrical body 15. The second cylindrical body 21 may have threaded sidewalls 22. The asymmetric body 26 is positioned on top of the second cylindrical body 21. The asymmetric body 26 may be cylindrical with a recess 37 at one side. The recess 37 may be open to the top 38 and the side 31 of the asymmetric body 26a. On top of the asymmetric body 26 is a threaded body 30 which may comprise a notch to turn the screw 14.

[0034] Referring to Fig. 6 the screw 14 is positioned in the cylinder head 2 and the recess 37 in the asymmetric body 26a is directed to a recess 36a in the cylinder head 2. A key 43 is placed in the recess 37 of the asymmetric body 26a and the recess 36 in the cylinder head 2. A nut (not shown) may be placed on the screw 14 on top of the asymmetric body and the key 43 to lock the screw in the predefined position.

Industrial Applicability [0035] With reference to FIG 7, a method 100 for mounting and dismounting of the screw 14 is described.

[0036] In a first step 100 the screw 14 is inserted in the bore 13 by turning the screw 14 until the second cylindrical body 21 abuts the step 25 of the cylinder head 2.The upper surface of the step 25 may be produced from a soft sealing material or a flexible sealing ring may be arranged at the step 25, so the second cylindrical body 21 may still abut the step 25, after the screw has been retracted to position the planar surface 19. In a second step 101 the screw 14 is retracted by turning the screw 14 until the asymmetric body 16 is in a predefined angular position indicating that the planar surface 19 of the screw 14 is now aligned with the lower surface 10 of the cylinder head 2. In a third step 102 the washer 27 may be placed over the asymmetric body 26, so the asymmetric body 26 meshes with the opening of the washer 27and the protrusion 35 of the washer 27 is inserted in the recess 36 of the cylinder head 2. This allows the screw 14 to be positioned in a predefined angular position, so the planar surface 19 at the tip of the screw 14 stays aligned with the lower surface 10 of the cylinder head 2. In a forth step the nut 32 is screwed on the threaded body 13 until the nut 32 abuts the outer surface of the cylinder head 2 and positions the washer 27 in the desired position.

[0037] Referring to FIG. 8 the method 200 discloses to dismount the screw 14 from the bore 13 to insert an endoscope into the cylinder. In a first step 201 the nut 32 may be unscrewed from the threaded body 30. In a second step 202 the washer 27 is removed from the asymmetric body 26 of the screw 14, so the screw 14 can be moved in an angular direction. In a third step 203 the screw 14 will be unscrewed from the bore 13 for example by using a device like a screwdriver which may be connected to the threaded body 13.

[0038] Referring to FIG 9, the mounting 300 of the screw 14 according to the embodiment disclosed in FIG 5 and 6 is described. In a first step 301 the screw 14 is inserted in the bore 13 by turning the screw 14, so the threaded sidewalls 22 of the second cylindrical body 21a meshes with the threaded walls of the bore 13 in the cylinder head 2. In a second step 302, when a lower surface of the second cylindrical body 21 abuts the upper side of the step 25 in the bore 13 of the cylinder head 2, the screw 14 is retracted by turning until the asymmetric body 26 is in a predefined angular position, indicating that the planar surface 19 of the tip of the screw 14 is aligned with the lower surface of the cylinder head 2. In this position the recess 37 of the asymmetric body 26a is aligned with the recess 36a in the cylinder head 2. In a third step 303 a key 43 may be inserted in both recesses 36a, 37 to prevent angular motion of the screw 14 with respect to the cylinder head 2. In a forth step, a nut 26 may be placed on the threaded body 30 to position the key 43 in the desired position.

[0039] As the preferred embodiments of this invention have been described herein, improvements and modifications may be incorporated without departing from the scope of the following claims.

Claims

1. Screw (14) for sealing a bore (13) in a cylinder head (2), the screw (14) comprising a longitudinal axis (16) and a screw tip (18) asymmetric in respect to the longitudinal axis (16).

2. Screw (14) of claim 1 with a planar surface (19) at the screw tip (18) , which planar surface (16) is inclined in respect to the longitudinal axis (16).

3. Screw (14) of claim 2, where the planar surface (16) defines the screw tip (18).

4. Screw (14) of any of the claims 2 to 3, where an angle (beta) between a longitudinal axis (20) of the bore (13) and a lower surface (38) of the cylinder head (2) intended to face a combustion chamber (4) corresponds to an angle (alpha) between the longitudinal axis (16) of the screw (14) and the planar surface (16).

5. Screw (14) of any of the claims 2 to 4, where the planar surface (19) extends over the cross section (40) of the screw (14).

6. Screw (14) of any of the claims 1 to 4, with an element (26, 26a) to determine the angular positon of the screw (14).

7. Screw (14) of claim 6 with a rotational asymmetric part with a recess(29).

8. Cylinder head (2) with an endoscopic bore (13) and a screw (14) according to any of claim 1 to 7 to seal the endoscopic bore (13), whereas the screw (14) is connected to the cylinder head (2) to prevent angular motion of the screw (14).

9. Cylinder head (2) of claim 8, where the screw (14) is connected to the cylinder head (2) by a washer (27) with an asymmetric opening (28) and an asymmetric outer shape and the screw (14) is placed through the opening (28) and the outside of the washer (27) engages with a recess (29) and/or a protrusion of the cylinder head (2).

10. Cylinder head (2) of claim 8, where the screw (14) is connected to the cylinder head (2) by a key (43) to prevent angular motion of the screw (14).

11. Method to seal a bore (13) in the cylinder head (2) comprising the steps: - inserting the screw (14) of one of the claims 1 to 7 in the bore (13) until a tip (18) of the screw (14) enters the combustion chamber (4); - retracting the screw (14) until the planar surface (19) of the screw (14) aligns with the lower surface (38) of the cylinder head (2); and - positioning the screw (14) with respect to the cylinder head (2) to prevent angular motion of the screw (14).