CN1003572B - Repairing method for crack of diesel engine casting frame - Google Patents

Abstract

The method of repairing the crack damage on the top surface of the diesel engine cast frame is to use the method of additional repair parts, and the compressive force of the cylinder head concentrated on the annular area of the top surface of the frame is distributed from the repair parts to a larger area in contact with the frame In order to avoid or reduce the expansion of cracks and ensure that the repaired diesel engine can continue to work normally for a long time. Applying this repair method can prevent the entire diesel engine or frame from being scrapped. The repaired frame structure is more reasonable than the original design in bearing the cylinder head compressive force. Therefore, the repaired diesel engine is more reliable.

Description

Repairing method for crack of diesel engine casting frame

The invention relates to a method for repairing cracked top panel of a diesel engine casting machine frame.

The cylinder body and the upper crankcase of the medium and small diesel engine are generally cast into a whole. The cylinder block and the upper crankcase of the medium and large diesel engine are generally separately cast and then connected into a whole after being processed. Both of which are referred to as a body or frame and constitute the skeleton of the diesel engine, hereinafter collectively referred to as a frame.

All parts and accessories of the diesel engine are arranged inside and outside the frame, and bear complex load. In actual use, circumferential cracks (9) are generated on the supporting ring-shaped surface of the top surface of the casting machine frame relative to the shoulder of the cylinder sleeve due to the pressing force of the cylinder head (see fig. 1 and 2).

The traditional repairing method is to bore the pressure bearing surface on the panel of the frame and to increase the diameter of the concave shoulder (see figure 3), and to pad a red copper ring (7) at the bottom to contact with the cracked surface and to pad a steel gasket (6) on the red copper ring (7), so that the pressing force of the cylinder cover still acts on the cracked surface. Therefore, the secondary cracks (10) with enlarged diameters are generated after the continuous use, and the concave shoulders have no room for further boring and enlarging the diameters, so that the whole diesel engine or the frame faces the situation of scrapping.

The invention aims to avoid or reduce the crack propagation of the top surface of the casting machine frame to the maximum extent and ensure that the repaired diesel engine can work reliably for a long time.

The technical scheme of the invention is as follows: a diesel engine casting frame crack repairing method comprises the following steps: the split surface of the frame top surface and the cylinder sleeve shoulder joint is honed with a concave shoulder, the diameter of the concave shoulder is increased, the concave shoulder is deepened, and then the shoulder is thinned, and then the cylinder with the correct compression ratio is kept to be installed. The invention is characterized in that: the cylinder of the repairing part is arranged in the annular concave shoulder of the frame, a gap must be kept between the bottom surface of the cylinder and the bottom surface of the annular concave shoulder on the top surface of the frame, the shoulder of the repairing part is pressed on the top surface of the frame by a fixing part, and a cooling water pipeline of the frame, which is communicated with the cylinder cover, passes through the shoulder of the repairing part. The invention uses the method of additional repairing parts to disperse the pressing force of the cylinder cover on the annular area of the top surface of the frame according to the principle of diffusion stress, and the pressure per unit area on the top surface of the frame can be reduced by several times compared with the pressure before repair under the condition of pressing the cylinder cover. As long as the repairing part has a reasonable structure, the cracked annular surface can not bear pressing force any more or only bear small pressing force after being installed, and the crack propagation of the top surface of the casting machine frame is avoided or reduced to the maximum extent. The diesel engine or the frame which is facing to be scrapped is saved. Compared with the original design, the condition that the repaired frame structure bears the pressing force of the cylinder cover is more reasonable. Therefore, the repaired diesel engine can reliably work for a long time.

The invention has the advantage of thoroughly solving the problem of repairing the cracked top panel of the diesel engine casting machine frame. And the bad condition that the casting frame originally bears the pressing force of the cylinder cover is improved. The repair requires replacement of only spare parts after a long period of use. When the repaired diesel engine needs to be disassembled and assembled in daily management and maintenance, no work needs to be added. The repair work is simple and quick, does not require disassembling the engine frame, and can be carried out on the original machine body, for example, the repair of each cylinder of the medium-sized diesel engine can be completed in about 8 hours, and the repair period is very short.

Several details of the invention will be described in conjunction with the following examples: example-repaired model: 8HvD48A-2U diesel engine

Rated output power: 970KW (1320 PS)

A production plant: the magedburgh, democratic, germany "karl lipeck entz" heavy machinery plant.

The frame structure is as follows: the whole casting is made of common cast iron and weighs about 4 tons.

The shape of the frame is as follows: length × width × height 3960mm × 960mm × 1450mm

Description of the drawings:

FIG. 1: a top partial cross-sectional view of the caster frame of this example is shown.

FIG. 2: showing an enlarged view of the casting machine frame top surface crack (9) and the installation position of the relevant accessory (as shown by an ideal line on the figure).

FIG. 3: before the present invention, a conventional repair method is shown, and the position of the second crack (10) is generated.

FIG. 4: a general structural diagram showing a repair method to which the present invention is applied.

FIG. 5: a structural view of a repair member (5) used in the repair method of the present invention is shown.

FIG. 6: a view showing a hold-down stud (2) with a collar shoulder that is used to replace the original cylinder head hold-down stud (8) by the inventive repair method.

FIG. 7: the schematic diagram shows that the original frame (1) requires partial processing due to the requirement of correct matching on the structure.

FIG. 8: the schematic diagram shows that the original cylinder sleeve (4) requires partial processing due to the requirement of correct matching on the structure.

The reference numbers of the specification indicate:

(1) compression of casting frame (2) with shaft collar shoulder

(3) Cylinder head stud

(4) Cylinder sleeve (5) repair part

(6) Steel washer (7) red copper ring

(8) The original cylinder cover pressing stud (9) represents a first crack

(10) Represents a second crack (11) through the cooling water conduit

(12) The diameter of the concave shoulder of the repair part after the matching diameter (13) of the repair part is increased

(14) Original thickness of cylinder sleeve shoulder

(15) Thickness of cylinder sleeve after shoulder smooth turning and thinning

0-0 represents the position of the fracture surface

Before repair, the casting frame (1) of the diesel engine is cracked, cracks (9) are positioned at right-angle vertexes on an annular concave shoulder of the top surface of the frame corresponding to the shoulder of the cylinder sleeve, and the inclined cracks are expanded along the circumferential direction (shown in figures 1 and 2).

The repairing method is characterized in that a concave shoulder is honed on a crack surface of the top surface of a frame (1) and the shoulder joint of a cylinder sleeve, the diameter of the concave shoulder is increased, the concave shoulder is deepened, the right-angle vertex of the bottom surface of the concave shoulder is in transition (shown in figure 7) on the increased diameter (13) through an arc of R2, a newly-added repairing part is installed as shown in figure 5, the repairing part is provided with a shoulder and a cylindrical part, and the diameter (12) of the cylindrical part is in sliding fit with the diameter (13) of the concave shoulder which is deepened through honing of the frame, so that a repaired cylinder has a correct central line. The existence of the original cracks is allowed on the deepened annular concave shoulder plane of the rack, but a gap must be kept between the cylindrical bottom surface of the repairing piece (5) and the annular concave shoulder plane of the rack, so that the pressing force of the cylinder cover is prevented from not acting on the annular concave shoulder plane of the rack, the shoulder bottom surface of the repairing piece (5) vertical to the axis of the cylindrical shaft is pressed on the rack surface by applying a fixing piece, and the pressing force concentrated by the cylinder cover can be dispersed to a larger bearing surface of the top surface of the rack because the area of the shoulder bottom surface is several times larger than that of the original annular concave shoulder plane of the rack, thereby greatly reducing the pressure born by the unit area of the top surface of the rack.

The method comprises the steps of boring and cutting an enlarged and deepened annular concave shoulder, coating a sealant, coating the sealant on the back surface of a repairing part (5), installing the repairing part (5) at a corresponding position on a rack (1), screwing six compression studs (2) with shaft collar shoulders, firmly pressing the repairing part (5) on the top surface of the rack, and sealing the contact surface by the sealant to prevent cooling water from leaking.

In order to ensure that the diesel engine has the correct compression ratio after repair, the original shoulder thickness (14) at the top of the cylinder liner (4) must be finished down to the thickness (15) (see fig. 8). The internal corner for processing the cylinder sleeve shoulder is in transition by adopting an arc R3, so that stress concentration is avoided. The outer corners of the shoulders can be correctly arranged on the repairing part (5) only by adopting 3 multiplied by 45 chamfered edges.

The fixing mode of the repairing part can use bolts, locating pins and pressing plates, but in order to simplify the installation structure, the original cylinder cover pressing stud (8) is changed into the structure of a pressing stud (2) with a shaft collar shoulder to expand the application of the repairing part, the lower shoulder is used for pressing the repairing part (5), the lower thread of the stud can be installed in an original threaded hole on a frame, and the upper thread of the stud is still used for pressing the cylinder cover (see figure 6).

The repair must have sufficient strength, and the total stress σ ∑ of the repair (5) of this example in the dangerous cross section of O — O shown in fig. 5 is 2855.8Kg/cm²For example, 40Cr or 45 steel is selected for tempering H_B255-285 with tensile strength of 9100Kg/cm²The safety factor A of the dangerous section is 3.186, so that the repairing part (5) is reliably used.

The shape of the repair shoulder can also be polygonal, circular or elliptical according to different models. The repairing part (5) can be made into one cylinder or several cylinders. The circular shoulder of the repairing part (5) is cut into two circular notches in a circular shape, the repairing part has the advantages that the mechanical processing is easy, the circular notches before and after being cut are used for avoiding the limitation of the center distance between two adjacent cylinders, the contact area of the repairing part and a panel of the rack can be increased, the unit area pressure of the top surface of the rack is reduced, and the mounting of the repairing parts of the adjacent cylinders is facilitated.

At several corners of the repair part, solid circular arcs R2 should be used for transition to prevent stress concentration.

The through hole (11) with a special structure on the repair part shoulder (see figure 5) is provided with an arc-shaped shoulder, and after the repair part (5) is installed on the rack, the through hole and the top surface of the rack form the same plane, so that a cooling water guide pipe of the rack, which leads to the cylinder cover, can keep the original structure and pass through the hole (11) on the repair part shoulder, and meanwhile, the original upper sealing ring and the original lower sealing ring of the cooling water guide pipe can be correctly installed.

Claims (6)

1. A method for repairing cracks in a cast diesel engine frame, comprising the following steps: boring a shoulder at the cracked surface where the frame top surface meets the cylinder liner shoulder, increasing the shoulder diameter and deepening the shoulder; and finally, installing the cylinder with the correct compression ratio after thinning the shoulder. The method is characterized in that a repair piece having a shoulder and a cylindrical portion is used; the cylindrical portion of the repair piece is installed into the annular shoulder of the frame; a clearance is maintained between the bottom surface of the cylindrical portion and the bottom surface of the annular shoulder on the frame top surface; the shoulder of the repair piece is pressed against the frame top surface by a fixing member; and a cooling water pipe from the frame to the cylinder head passes through the shoulder of the repair piece. 2. The repair method according to claim 1, characterized in that: there is a hole (11) on the shoulder of the repair part for the cooling water pipe to pass through, and the hole (11) has an arc-shaped shoulder so that it forms the same plane with the top surface of the frame after being installed on the frame to ensure the correct installation of the cooling water pipe and its sealing ring. 3. The repair method according to claim 1, wherein the shoulder of the repairing piece is circular, polygonal or elliptical in shape. 4. The repair method according to claim 1, wherein the repair piece is made into one piece for each cylinder or one piece for several cylinders. 5. The repair method according to claim 1, wherein the fixing member is a stud with a shaft collar shoulder that fixes the repair member and the cylinder head together in the original threaded hole of the frame. 6. The repair method according to claim 1, wherein the fixing member is a stud, a positioning pin or a pressure plate.

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