Low-Pressure Mold and Production Process for Aluminum Alloy Integrated Brake Calipers

The present invention relates to the technical field of casting, specifically to a low-pressure mold and production process for aluminum alloy integrated brake calipers.

Brake calipers are an important component of automobile brake systems. Integrated brake calipers have better rigidity, deformation resistance, and more stable braking performance than split calipers. Meanwhile, aluminum alloy calipers are more advantageous than cast iron calipers in weight, heat dissipation, corrosion resistance, and visual effect. Therefore, as the automobile industry increasingly focuses on green environmental protection and appearance, the proportion of integrated aluminum alloy brake calipers in medium- and high-end passenger vehicles is increasing. Production processes for brake calipers are currently mainly based on gravity casting. Because the flow and feeding of molten metal rely on natural gravity during gravity casting, the filling and feeding capabilities of the molten metal are relatively poor, resulting in poor compactness and high porosity of casting structures and thus affecting the quality and performance of the calipers. In addition, relatively low dimensional accuracy and poor surface quality of gravity casting cannot meet the appearance requirements of medium- and high-end vehicles for attractive and fashionable calipers.

In view of the above technical problems, the technical solution adopted by the present invention is as follows: A low-pressure mold for aluminum alloy integrated brake calipers includes a bottom plate, a right mold core and a left mold core are provided on the bottom plate, and the right mold core and the left mold core have the same internal structure and are each provided with a sprue assembly; the mold further includes an ejection rod pushing plate, an ejection rod is provided on the ejection rod pushing plate, the ejection rod pushing plate drives the ejection rod to rise and fall, and a casting is released from the mold through the ejection rod; the right mold core includes an upper mold core and a lower mold core, the upper mold core is fixedly mounted on a top plate, the lower mold core is fixedly mounted on the bottom plate, the top plate drives the upper mold core to move up and down to open and close the mold, a sand core is provided between the upper mold core and the lower mold core for forming a cavity structure of the casting, and the sand core is connected to a negative pressure exhaust device; the sprue assembly includes a sprue bush and a sprue cup fixed on the lower mold core through a pressure plate; the sprue assembly further includes a sprue spreader, the sprue spreader is fixedly mounted on the upper mold core, and the sprue bush, the sprue cup and the sprue spreader are arranged coaxially.

Further, a filter screen is placed on the sprue bush, and the filter screen is made of fibers.

Further, the sprue bush and the sprue cup are made of ceramic.

Further, a riser is further provided on the right mold core, an insulation insert is provided at an upper portion of the riser, and asbestos is placed inside the insulation insert.

Further, the insulation insert has a thickness of 3-5 mm.

Further, a novel cooling insert is further provided on the right mold core, and the novel cooling insert on the right mold core is located at a thick position of the casting; the novel cooling insert consists of an insert I and an insert II, which are tightly matched and welded together; the insert I has a cavity structure with a wall thickness of 15-20 mm; and the insert II has a water inlet pipeline and a water outlet pipeline, with diameters of 8 mm.

Further, an exhaust groove with a depth of 0.1-0.25 mm and a width of 20-35 mm is provided on a parting surface between the upper mold core and the lower mold core.

Further, an aluminum stopper with a height of 15-40 mm and a fit clearance of 2-4 mm is further provided between the upper mold core and the lower mold core.

Further, the ejection rod has a diameter of 8-16 mm and is used with an ejection rod sleeve, and the ejection rod sleeve is provided with an exhaust groove.

A production process for aluminum alloy integrated brake calipers includes the following steps:

Compared to the prior art, the beneficial effects of the present invention are as follows: (1) the low-pressure casting process has higher production efficiency and yield than gravity casting; (2) castings produced by low-pressure casting have higher structural compactness and more excellent mechanical properties than those produced by gravity casting; (3) aluminum alloy integrated brake calipers produced by the process of the present invention have a yield strength greater than 280 MPa, a tensile strength greater than 320 MPa, an elongation rate greater than 2%, a casting production efficiency up to two pieces in 300 seconds, and a yield rate greater than 95%; and (4) due to the similarity in the design of brake calipers, the present invention has strong universality for integrated brake calipers.

In the figures:—bottom plate;—top plate;—connecting plate;—ejection rod pushing plate;—right mold core;—left mold core;—reset rod;—positioning key;—negative pressure exhaust device;—ejection rod;—insulation insert;—upper mold core;—aluminum stopper;—ejection rod sleeve;—casting;—lower mold core;—point cooling joint;—sprue spreader;—exhaust plug;—sand core;—filter screen;—sprue bush;—sprue cup;—pressure plate;—ejection rod boss;—riser.

The technical solution of the present invention will be further illustrated in conjunction with the accompanying drawings and specific embodiments.

A low-pressure casting mold for aluminum alloy integrated brake calipers, as shown in, first requires a lean pouring system design. On the one hand, sufficient feeding capability is required to achieve sequential solidification of castings and ensure casting yield. On the other hand, the weight of the pouring system is minimized to improve material utilization and shorten a casting cycle. Based on the product structure characteristics of integrated calipers, two sprues are provided on two sides of a casting, the two sprues are connected to 2 inner runners and 3 inner runners respectively, and the inner runners are connected to the castingfor feeding. By simulation analysis and calculation, the weight of the castingis 3-5 kg, the minimum diameter of the sprue is 50 mm, the thickness of the sprue is 25-40 mm, the width of the inner runner is 35-55 mm, and the thickness of the inner runner is greater than ⅔ of the thickness of the cross section of the castingat a sprue entrance. Meanwhile, a riseris provided at a distance of 10-15 mm from the casting on each inner runner to ensure the feeding capability of the runner, and the height of the riseris greater than twice the thickness of the cross section of the castingat the sprue entrance.

A low-pressure casting mold for aluminum alloy integrated brake calipers includes a bottom plate, a top plate, a connecting plate, an ejection rod pushing plate, a right mold core, a left mold core, a reset rod, positioning keys, and an ejection rod. The right mold coreand the left mold coreare provided on the bottom plate, the right mold coreand the left mold corehave the same structure and are mirror images of each other, and both the right mold coreand the left mold coreare provided with a sprue assembly. The ejection rod pushing plateis connected to an ejection oil cylinder of the mold, the ejection rodis arranged on the ejection rod pushing plate, and the ejection rod pushing platedrives the ejection rodto eject. The ejection rodis in contact with an ejection rod bosson the castingto achieve mold release of the casting, which can, on the one hand, prevent the ejection rodfrom leaving an ejection mark on the castingto affect the appearance of the casting, and on the other hand, avoid the problem of empty ejection of the ejection roddue to runner shrinkage. The ejection rodhas a diameter of 8-16 mm and is used with an ejection rod sleeveto protect the mold. In addition, the ejection rod sleeveis provided with an exhaust groove for exhausting. When the mold is closed, the reset rodcan completely reset the ejection rod pushing plate. The reset rodis arranged on the bottom plate, a limit rod is arranged above the reset rod, the reset rodis in contact with the limit rod, the limit rod is arranged on the ejection rod pushing plate, a spring is sleeved on the limit rod, a first end of the spring is fixedly mounted on the ejection rod pushing plate, and a second end of the spring is fixedly mounted on the top plate.

The right mold coreincludes an upper mold core, a lower mold core, and a sand core. The lower mold coreis fixedly mounted on the bottom plate, and four groups of positioning keysare provided on the lower mold core. When the mold is closed, the lower mold coreand the upper mold coreare accurately closed through the positioning keys.

The bottom plateis fixedly connected to a low-pressure casting machine, the upper mold coreis fixedly mounted on the top plate, the top plateis fixedly mounted to the connecting plate, the top plateis connected to a moving platform plate through the connecting plate, and the moving platform plate drives the top plateand the upper mold coreto move up and down through the connecting plate, achieving the opening and closing of the mold. The sand coreis provided between the upper mold coreand the lower mold corefor forming a cavity structure of the casting, and the sand coreis connected to a negative pressure exhaust device. A large amount of gas is generated by heating the sand core, resulting in the occurrence of pores and pin holes in the casting. Therefore, the negative pressure exhaust deviceis provided at a thick position of the sand core. An exhaust plughaving a diameter of 8-12 mm is placed on the sand core, and then is connected to the negative pressure exhaust deviceabove through a straight hole of the mold. When air is introduced into the negative pressure exhaust device, negative pressure is generated in channels to suck out the gas generated by heating the sand core.

The sprue assembly includes a sprue bush, a sprue cup, a pressure plate, and a sprue spreader. The sprue bushand the sprue cupare fixed to the lower mold corethrough the pressure plate, the sprue spreaderis fixed to the upper mold core, and axes of the sprue bush, the sprue cup, and the sprue spreaderare on a straight line. Both the sprue bushand the sprue cupare made of ceramic. The ceramic sprue bushand sprue cupcan effectively improve the heat preservation capability of a sprue position, reduce the temperature loss of molten aluminum at the sprue, and improve the feeding capability of the sprue position. A point cooling jointis provided on the sprue spreader. When molten aluminum is filled, the sprue spreadercan change the flow direction of the molten aluminum. During solidification, the sprue spreadercan cool the sprue and shorten the casting cycle.

A conical filter screenis placed on the sprue bush. After the mold is closed, the sprue spreaderis used to press the filter screento prevent the molten aluminum from flushing away the filter screen. The filter screenis made of fibers, so that the sprue with the filter screencan be directly used for melting after being cut off, and the fiber screen will not pollute the molten aluminum, reducing raw material waste and improving economic efficiency.

The riseris provided on the runner of the right mold core, an insulation insertis provided at an upper portion of the riser, and asbestos is placed inside the insulation insertto increase the feeding capability of the riser.

The insulation inserthas a thickness of 3-5 mm.

A novel cooling insert is further provided on the right mold core. The novel cooling insert on the right mold coreis located at a thick position of the castingto improve the local cooling speed of the casting, achieve sequential solidification, and obtain finer grain structures. The novel cooling insert consists of an insert I and an insert II, which are tightly matched and welded together to prevent water leakage.

The insert I has a cavity with a wall thickness of 15-20 mm; and the insert II has a water inlet pipeline and a water outlet pipeline, with diameters of 8 mm. During working, cooling water enters the cavity of the insert I through the water inlet pipeline and can flow out through the water outlet pipeline after filling the cavity. A conventional cooling insert has only a cooling pipeline, while the novel cooling insert having the water cavity inside achieves more sufficient heat exchange and much greater cooling capacity than the conventional cooling insert.

An exhaust groove with a depth of 0.1-0.25 mm and a width of 20-35 mm is provided on a parting surface between the upper mold coreand the lower mold core.

An aluminum stopperwith a height of 15-40 mm and a fit clearance of 2-4 mm is further provided between the upper mold coreand the lower mold core. The aluminum stoppercan prevent molten aluminum leakage during production.

A production process for aluminum alloy integrated brake calipers includes the following steps:

Efficient and stable production of aluminum alloy brake calipers is achieved through low-pressure casting. Aluminum alloy integrated brake calipers produced by this process have a yield strength greater than 280 MPa, a tensile strength greater than 320 MPa, an elongation rate greater than 2%, a casting production efficiency up to two pieces in 300 seconds, and a yield rate greater than 95%.