RU2563398C2 - Device for pistons manufacturing of internal combustion engine - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention relates to machine building, in particular, to casting industry. The device contains a movable 3 and fixed 4 half-shapes, pushing out 7 and pressing 8 plungers. In the fixed half-shape a bushing 6 is installed, it connects the filling hole with the shape cavity. In the movable half-shape a Ni-resist iron insert 15 is installed. The half-shapes are provided with bandages 12, on them slotted channels are made, and sealing ring 13 with union 14 connected with the vacuum system is installed. In the bandages the hydraulic cylinders 11 with pistons and rods 10 forming dents in the casting for the piston pin holes are installed.

EFFECT: increased mechanical properties of the piston, increased strength of connection of the Ni-resist iron insert with the aluminium casing, increased productivity.

1 dwg

Description

The invention relates to mechanical engineering, to foundry, in particular to the manufacture of pistons of internal combustion engines (ICE), including with a nresist ring, injection molding with crystallization.

A known method of manufacturing ICE pistons (patent RU 2093301), in which a ceramic insert is installed in the stamp and fixed using a niresist insert in the process of its subsequent placement and fixation in the stamp. After that, liquid metal is poured into the stamp, stamped to obtain a body with inserts fixed in it, the side holes in the body are pierced, the lower prepress and soak under pressure to ensure crystallization. Alitirovanie inserts produced immediately before placement in the stamp. Stamping is carried out in two stages at a reduced and nominal pressure with a holding time of 10-15 seconds between stages to form a sealing girdle. The flashing of the side holes and the lower prepress are performed sequentially after stamping.

The disadvantages of the device are:

1) the danger of maintenance due to shots in the mold connector associated with an unstable dose of the poured metal;

2) the danger of maintenance and inconvenience in work due to the reduction of the space between the fixed matrix and the punch due to the location of the container with the matrix;

3) instability in the work due to the difficulty of removing the casting from the sleeve due to a burr in the holes of the matrix under the side firmware;

4) restrictions on the shape of the piston due to the need to push out of the matrix, the inability to perform arresters on the piston in the area of the holes for the piston pins and other surfaces.

Closest to the claimed is a device (Patent RU 2324574), which consists of movable half-molds, plunger, rods, which are in extreme positions until they stop in the half-molds. The plunger is located below the bottom of the piston, decorated with a liner. The alitized niresist insert extracted from the crucible is installed on the liner supports.

The disadvantages of the device are:

1) pressure is applied during the crystallization process, which, under conditions of uneven cooling of various volumes of the piston billet, inevitably leads to the fact that some parts of the volume become solid and resist pressure, while other parts of the volume (thermal units) remain in the liquid condition. Crystallization of metal in thermal nodes occurs in conditions of a shortage of liquid metal to compensate for shrinkage. In thermal nodes, in this way, obvious and latent defects are formed in the form of shells, looseness, micropores, etc. The consequence of the simultaneous crystallization of the metal in the entire volume is a decrease in the density of the metal, a decrease in its strength and plastic properties, which is unacceptable for turbocharged engines with a high compression ratio and a high operating temperature;

2) the use of cast aluminum alloys, while it is known that leading companies in the automotive industry have mastered the production of pistons by hot stamping from deformable thermally hardened alloys such as alloy D16;

3) insufficiently effective use of pressure as a factor of external influence on the formation of casting properties — the pressure value and the nature of its change in time during the first and second stages of the process are not given, and the fact of increasing the properties of the piston metal is not related to the claims

4) the metal is poured into a stamp with a vertical axis of the piston, which leads to delays in closing the mold and the supply of the punch. Disclosing a form also requires actions that are difficult to automate.

The technical effect achieved from the proposed invention is to improve the quality of the manufactured piston, obtain a stable piston size, improve the microstructure of the piston material, increase the mechanical properties, increase the productivity of the process.

A device that implements a method comprising two half-forms fixed in plates, pressing and pushing out plungers, a niresist insert installed in the form, one of the half-forms fixed on the plate is fixed, a sleeve with a horizontal cylindrical channel is installed in the fixed half-shape, connecting the filling hole with the cavity of the half-mold, the niresist insert is installed in the movable half-mold, the half-molds are reinforced with bandages with slotted channels made on them, a sealing ring is installed on the bandages, in which the fitting is connected, connected to the vacuum system of the working cavity of the mold, grooves are made in the bandages, in which the rods are set, which are driven by the pistons of the hydraulic cylinders, while the end part of the rod is made in the form of a conical protrusion, forming grooves under the holes of the piston pin.

The drawing shows the proposed device, including installed on the movable 1 and fixed 2 plates of the press with a horizontal axis of the pressing plungers and stamped piston, movable 3 and fixed 4 half-molds, left 5 and right 6 of the sleeve, left ejector 7 and right pressing 8 plungers, and also the pouring bowl 9. The auxiliary elements of technological equipment include a rod 10, which is driven by a piston of a hydraulic cylinder 11, bandages 12, a ring 13 with a fitting 14 connected to a working vacuum system her cavity forms. The rod 10 is made in such a way that its end part in the form of a conical protrusion forms the recesses - the basting under the holes of the piston pin. The rod 10 under the pressure of the working fluid in the hydraulic cylinder 11 enters the corresponding recess in the half-molds 3 and 4 and, making holes on the side surface of the piston, seals the mold cavity from a possible breakthrough of the liquid metal. The plunger 7 in the initial position with its right end face is aligned with the end surface of the left side of the mold cavity. Here, on the protrusions of the working surface of form 3, a pre-aliased niresist insert 15 is installed.

Before the start of the cycle, the pressing plunger 8 is installed to the right of the vertical opening of the pouring bowl 9. On the working surface of the mold cavity in the open state after heating with a gas flame to a temperature of 250 ± 10 ° C, a layer of graphite-containing paint is applied using a spray gun. By moving the plate 1, the half-mold 3 is brought into contact by the half-mold 4. The alignment of the axes of the half-molds is ensured by the fact that the plate 1 moves along the columns of the press along the guides processed with high accuracy. On the half-molds 3 and 4, hot bandages are installed to hold high pressure in the mold cavity. In the bandages 12, recesses are provided for mounting the hydraulic cylinder 11. The hydraulic cylinder 11 is rigidly connected to the band of the half mold 4 and freely enters the cavity of the half mold 3.

The force applied to the half-molds at the moment the cavity closes should be greater than the force that opens the mold under pressure of the molten metal. This force is calculated by the formula P _app > pF, where p is the pressure applied to the liquid metal, F is the projection area of the piston on the plane of the connector.

So, at a pressure of p = 400 MPa and a piston diameter of 90 mm, _Psp = 255 tf = 2.55 MN.

The molten metal, superheated above the crystallization onset temperature by 120 ± 10 K, is poured into the mold cavity with a measured dose with an accuracy of ± 2% through the casting bowl 9. The volume of air inside the mold during heating by the cast metal increases 5 ... 10 times and without taking measures, the fill metal can stop and part of the cavity will remain empty. Therefore, it is provided that at the moment liquid metal enters the pouring bowl, a temperature sensor is triggered, a signal from which opens an electromechanical valve connecting through the slot-like channels through the cavity of the mold connector through the gap between the bandages 12 and the ring 13 through an opening in the nozzle 14 with the vacuum system. The created vacuum up to 1 ... 5 mm Hg ensures the required ventilation and efficient filling of the mold with liquid metal. In the working cavity of the mold, a recess of the conical shape is provided, into which the reserve volume of the liquid metal enters. According to experimental data, this volume is

V _p = 0.2 V _p

where V _p is the volume of the piston metal.

At the end of the filling, the pressing plunger 8 is turned on.

For reasons of quick assembly of the mold, the level of the poured metal should not exceed the level of the plunger 8 more than a = 5 ... 10 mm.

When the plunger 8 moves, the filling hole is blocked, and a metal volume is pressed into the mold cavity, which ensures at the first stage the metal level rises to the upper point of the mold, and at the second stage, compensation of the metal volume shrinkage by applying high pressure on the metal before crystallization begins.

During the movement of the plunger in a section of length L in thin sections, in particular where the piston skirt is formed, a layer of crystallized metal can form. The metal crystallizes along the contact surface with the plunger 8 and the sleeve 6. At this time, the plunger 8 pushes the crystallizing metal forward into the mold cavity, creating pressure on the liquid metal in a relatively massive place of the piston. This pressure extends to all points of the piston space, providing effective feeding of crystallizing metal through the internal channels between the dendrites. In the second stage of the movement of the plunger 8, the pressure applied to the liquid metal in the pressure chamber is 300 ± 10 MPa. If the movement time of the plunger 8 in a section of length L does not exceed 3 ± 0.2 s, the casting of the piston guarantees the absence of casting defects of gas-shrink origin, and the metal density and its physical and mechanical properties are not inferior to the properties of a wrought or stamped alloy of the same composition.

The manufacturing process of the piston thus proceeds in the sequence:

- pouring a measured portion of metal;

- inclusion of a vacuum system within 1 ... 2 s after the start of pouring;

- the inclusion of the pressing plunger 8, the movement to overlap the filling hole for 0.2 ... 0.3 s;

- further movement of the plunger 8 with a speed of 40 ± 5 mm / s - stage of filling;

- increasing the pressure developed by the pressing plunger 8, to a level of 300 ± 10 MPa;

- holding under pressure for a time sufficient to complete crystallization and cooling to a temperature of 350 ... 400 ° C;

- disclosure of the mold when the plate 1 moves to the left with the extraction of the casting from the right side of the mold cavity;

- removal of the pressing plunger 8 to its original position.

The length of the plot L is calculated by the formula:

L = L ₁ + L ₂ .

,Here

,

where V _N.C. - the unfilled part of the piston volume, d is the diameter of the plunger. L ₂ - the stroke of the plunger necessary to compensate for the volumetric shrinkage of the piston. Based on the studies, it was found that alloys based on aluminum, such as alloy D16 at a temperature t = t _L + 120 ... 130 under a pressure of 300 ± 10 MPa, reduce their volume by 11 ... 12%, therefore

where V is the total volume of metal poured into the mold. The total volume can be calculated or established empirically.

The unfilled part of the volume can also be calculated by the formulas of geometry or determined by the formula:

Thus, the main process parameters can be defined and fixed.

As an example of determining the values of L and d, we can take the manufacture of the aforementioned piston with dimensions of ⌀90 × 60 mm.

Assume that V is 400 cm ³ .

V _f = 280 cm ³ . Press force applied to the plunger, P = 0.3 MN.

Plunger diameter

Here p is the pressure applied to the metal.

P = 300 ± 10 MPa.

We find d = 35 mm.

V _ODA = (0.11 ... 0.12) V = 44 ... 48 cm ³ .

Hence L ₂ = 45 ... 50 mm.

V _n.a. = VV _f -V _ODA = 400-280- (44 ... 48) = 400-280-46 = 74 cm ³ .

.Then $$L_{\mathrm{one}}=\frac{\mathrm{four}{V}_{n.s.}}{\pi d^2}=80\text{mm}$$

.

Thus, L = 80 + 50 = 130 mm.

The fundamental difference between the invention and the known analogues and prototypes is that the molten liquid metal is pushed into the mold through a cylindrical channel in the sleeve 6 using a pressing plunger. A part of the pushed volume ensures filling of the form, and the remaining part of the volume is pressed into the piston volume under high pressure. A liquid metal decreases in volume, its atoms come together almost the same distance as in a solid metal, therefore, after pressure testing in a liquid state, subsequent crystallization occurs without shrinkage, without the formation of defects.

Given the design of the piston, it would be possible to pressure test the liquid metal inside the mold cavity. This option is unacceptable, because with the reverse movement of the plunger 8, the metal falls into the gap between the plunger 8 and the sleeve 6, which inevitably leads to scuffing, destruction of both the plunger and the sleeve.

The overflow of liquid metal is also unacceptable above the mark a (see drawing) a = 5 ... 10 mm, since the metal that has crystallized in the pouring hole can only be removed by turning the pouring bowl 9 through the thread, which leads to an unjustified loss of time, to a decrease performance.

The provided d × L channel, thus, performs complex functions of piston shaping and the formation of a dense defect-free structure by pressing crystallizing metal into molten metal, which will transfer pressure to all points of the piston space through the channels between dendrites, namely:

- blowing out metal residues from the filling hole;

- the inclusion of hydraulic cylinders 11, undermining and removing the rods 10 from the piston;

- ejection of the piston by the pressing plunger 7 from the left mold cavity;

- preparation of technological equipment for the next pouring cycle.

According to preliminary data, the full cycle time is 150 ... 180 s. Productivity 20 ... 25 castings per hour. However, taking into account that the set of technological equipment is quick-detachable, the holding time of the equipment in the working space of the press can be reduced to 30 ... 40, and cooling to a temperature of 350 ... 400 ° C is carried out outside the press in the technological device, since there is not much effort to push the casting out required. In this case, productivity increases by 3 ... 4 times and the process, according to technical and economic criteria, reaches higher competitiveness in comparison with the processes used by leading world companies.

The claimed invention allows to improve the quality of the pistons due to the formation of a dense uniform fine-grained structure in both thin and massive sections by increasing the mechanical properties, increasing the strength of the connection of the niresist insert with an aluminum case. Improved working conditions, increased work safety. Productivity is increased due to the continuity, mechanization and automation of the processes of mold assembly, metal crimping, and casting extraction.

Claims (1)

A device for the manufacture of pistons of internal combustion engines, containing two half-molds mounted on plates, pressing and pushing plungers, a niresist insert, hydraulic cylinders with rods, the end part of which is made in the form of a conical protrusion, forming grooves under the holes of the piston pin, characterized in that one of the half-mold is made stationary and provided with a sleeve with a horizontal cylindrical channel connecting the filling hole with the cavity of the half-mold, a niresist insert is installed in Vision mold half, the mold halves are provided with cable ties, which are made slotted channels and bands mounted on the sealing ring with a nipple associated with the system operating vacuum mold cavity, wherein the recesses in the shroud in which are installed cylinders with pistons and rods.