JP2006007802A - Knuckle for automobile and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a knuckle for automobile with necessary and sufficient strength, and a method of manufacturing it. <P>SOLUTION: In this knuckle for automobile composed of aluminum or an alloy thereof manufactured by casting, each component has an average of DASII value of 10-34μm. Each component desirably has an average tensile strength of 260MPa or more, an average load bearing capability of 170MPa or more, and an average elongation of 8% or more. In manufacturing this knuckle, molten metal is injected to a cavity forming the knuckle for automobile, and the molten metal injected to the cavity is cooled at 180-2200°C/min. At the time of casting, a riser part is provided to be continued to a bearing support part, and the average solidification speed of a knuckle body is set higher than that of the riser part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an automobile knuckle and a method for manufacturing the same.

An automobile knuckle is a component that connects a bearing that supports a wheel and a suspension, and needs to have appropriate rigidity and strength. In addition, since the knuckle for an automobile is held by press-fitting or the like, it is necessary to be able to withstand sag due to long-term use.
On the other hand, in recent years, there has been a demand for weight reduction of automobile knuckles due to the demand for higher vehicle efficiency, and some vehicles use aluminum (or an alloy thereof) as a material (for example, , See Patent Document 1).
JP 2004-090034 A (paragraph 0017)

However, until now, material requirements such as necessary strength for an automobile knuckle have not been sufficiently studied, and the cost has been unnecessarily increased or performance has been varied.
This invention is made | formed in view of such a background, and makes it a subject to provide the knuckle for motor vehicles provided with sufficient performance, and its manufacturing method.

  In order to solve the above-mentioned problems, an automotive knuckle according to the present invention is an automotive knuckle manufactured by casting and made of aluminum or an alloy thereof. Each component has an average DAS (Dendrite Arm Spacing) II value. 10 to 34 μm.

  By configuring the knuckle for automobiles with such a fine-structured material, it is possible to have both strength and toughness and higher reliability.

The above-described knuckle for automobiles preferably has an average tensile strength of 260 MPa or more, an average yield strength of 170 MPa or more, and an average elongation of 8% or more in each of the components. Some of the conventional knuckle for automobiles have a tensile strength of 260 MPa, a proof stress of 170 MPa, or an elongation of 8%. However, all of these characteristics are averaged in all of the constituent parts. There was nothing to satisfy. In the present invention, by satisfying this characteristic on the average of all the constituent parts, a knuckle for automobiles having unprecedented strength and reliability can be obtained.
And it is preferable to use a gravity casting method or a low pressure casting method as the above-mentioned casting method. In particular, it is desirable to use a reduction casting method in order to improve the circumference of the hot water.

  The method for producing an automobile knuckle according to the present invention is characterized by injecting molten metal into a cavity forming the automobile knuckle and cooling the molten metal injected into the cavity at 180 to 2200 ° C./min.

  Thus, by performing rapid cooling, the structure can be refined and sufficient performance can be obtained for an automobile knuckle.

  Alternatively, a method for manufacturing an automobile knuckle by casting an automobile knuckle includes a knuckle body forming the automobile knuckle, and a riser section that is continuous with a bearing support section that accommodates a wheel support component of the knuckle body. Is formed as a cavity, the molten metal is injected into the cavity, and an average solidification rate of a portion corresponding to the knuckle body is made higher than an average solidification rate of the riser portion, thereby cooling the molten metal. And

  In this way, by making the average solidification rate of the knuckle body higher than that of the riser part, the hot water can be effectively acted and a dense structure can be obtained.

  Further, it is desirable that an average solidification rate of a portion corresponding to the knuckle body is 180 to 2200 ° C./min, and an average solidification rate of the riser portion is less than 180 ° C./min.

Furthermore, it is desirable to use aluminum or an alloy thereof as the molten metal. Thereby, weight reduction of the knuckle for motor vehicles can be achieved.
In particular, these casting methods are preferably a gravity casting method or a low pressure casting method, and it is more desirable to use a reduction casting method.

  According to the knuckle for automobiles of the present invention, necessary and sufficient strength can be ensured and reliability can be improved.

Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In the drawings to be referred to, FIG. 1 is an external perspective view of an automobile knuckle.
As shown in FIG. 1, the knuckle 1 for an automobile according to the embodiment includes a bearing support 2 that supports a ball bearing 8 that is a support part of a wheel by press-fitting or fastening, and a plurality of parts that are fastened to a suspension of the automobile. The mounting boss 3 includes a plurality of knuckle arms 4 that connect the bearing support portion 2 and the mounting boss 3 to each other. A fitting hole 2 a into which the ball bearing 8 is fitted is formed in the bearing support portion 2. The knuckle 1 for an automobile is preferably made of aluminum or an alloy thereof, and in each constituent part, the average tensile strength is 260 MPa or more, the average proof stress is 170 MPa or more, and the average elongation is 8% or more. The average here means that for a single knuckle 1 for an automobile, a plurality of tensile test pieces are cut out from a plurality of knuckle arm 4 portions and bearing support portion 2 portions, and each of the plurality of tensile test pieces is pulled. The strength, proof stress, and elongation are obtained and the arithmetic average is taken.

  When the automobile knuckle 1 is manufactured from aluminum or an alloy thereof, the average DASII value is preferably 10 to 34 μm. This average is also obtained by measuring DASII values for a plurality of tissues of the knuckle 1 for an automobile and arithmetically averaging them.

The automotive knuckle 1 having such material characteristics has unprecedented durability, sag resistance, and the like. Particularly, when the average tensile strength is 260 MPa or more and the average yield strength is 170 MPa or more, good durability and sag resistance can be realized.
Further, when the average elongation is 8% or more, it is possible to sufficiently absorb energy at the time of breakage and to secure an impact absorbing power.
Moreover, it can be set as the knuckle 1 for motor vehicles which has intensity | strength and toughness because DASII value is 34 micrometers or less.

  Such an automobile knuckle 1 is preferably manufactured by a gravity casting method or a low pressure casting method. In particular, in the gravity casting method or the low pressure casting method, the knuckle 1 for an automobile having excellent characteristics as described above can be manufactured by performing a controlled cooling with a high cooling rate. In order to realize such a high cooling rate, it is more desirable to use a reduction casting method that can improve the circumference of the hot water.

Next, the manufacturing method of the knuckle 1 for motor vehicles is demonstrated.
FIG. 2 is a schematic cross-sectional view of a mold for producing the knuckle for automobiles of the present invention. As shown in FIG. 2, the mold 10 is a mold for casting the knuckle 1 for an automobile by a gravity casting method using a molten aluminum. The mold 10 is formed with a cavity 11 in the shape of the knuckle 1 for an automobile, and a gate 13 communicating with the cavity 11 and opening on the upper surface 10 a of the mold 10. In the cavity 11, the cast product 12 is formed by pouring molten metal. The cast product 12 includes a portion corresponding to the bearing support portion 2 (hereinafter simply referred to as “bearing support portion 2”), a portion corresponding to the mounting boss 3, and a portion corresponding to the knuckle arm 4 (hereinafter simply referred to as “knuckle arm 4”). The cavity 11 is formed with the bearing support portion 2 facing upward. The surface of the cavity 11 is provided with an appropriately selected coating mold in order to obtain a desired cooling rate for the entire surface or for each part.

  On the bearing support portion 2, a riser portion 15 is provided continuously upward at the position, and a feeder port 15 a is opened on the upper surface 10 a of the mold 10 above the riser portion 15. The riser unit 15 is appropriately subjected to heat insulation coating, heat insulation coating, etc. in order to slow down the cooling rate (solidification rate). Or you may form the type | mold part of the riser part 15 with a ceramic with high heat insulation. In the bearing support portion 2 of the cast product 12, the prepared hole 12a of the fitting hole 2a is formed.

  The mold 10 is provided with cooling channels 16 and 17 at a plurality of desired locations, and at two locations in the present embodiment. A cooling medium such as cooling water cooled to a predetermined temperature by the cooling water supply system 18 is supplied to the cooling channels 16 and 17 via the automatic flow rate adjusting valves 16a and 17a.

  The cooling flow paths 16 and 17 are arranged so that a portion of the cavity 11 of the mold 10 that needs to be cooled can be sufficiently cooled. For example, in FIG. 2, the cooling flow path 16 is disposed near the knuckle arm 4, and the cooling flow path 17 is disposed near the riser portion 15. Further, thermocouples 19 and 20 as temperature detecting means are arranged near the surface of the cavity 11 corresponding to the cooling channels 16 and 17, respectively.

  The outputs of the thermocouples 19 and 20 are detected, for example, every 0.1 second by the control means 21 having a CPU and a memory. The control means 21 can adjust the flow rate of the cooling water flowing through the mold 10 by controlling the automatic flow rate adjusting valves 16a and 17a based on a program set in advance and stored in the memory.

  Next, a method for controlling the temperature of the mold 10 will be described with reference to FIG. FIG. 3 is a graph showing a relationship between time and temperature in casting the knuckle for automobiles according to the embodiment. In FIG. 3, the temperature of the cavity surface defining the riser unit 15 and the knuckle arm 4 detected by the thermocouples 19 and 20 is controlled, and the automatic flow control valves 16a and 17a are controlled by the control means 21 based on the detected temperature. Thus, the flow rate of the cooling water flowing through the cooling flow paths 16 and 17 is adjusted. In the graph of FIG. 3, the solid line is the cooling curve of the knuckle arm 4 set for the thermocouple 19, and the broken line is the cooling curve of the riser unit 15 set for the thermocouple 20.

Here, the period from the pouring start time A to the pouring start time A of the next cycle is one cycle of casting.
In the program stored in the control means 21, a set temperature, which is a control target value that changes according to the elapsed time of one cycle, is set based on an actual temperature change when test casting is performed on the mold 10. The set temperature in the present embodiment is the set temperature 32 (temperature T2) that is a constant value from the pouring start time A to the maximum temperature reaching time B for the riser unit 15, and the pouring point coagulation time C2 from the maximum temperature reaching time B. A temperature-time target characteristic 31 until the pouring gate and the pouring gate solidify, temperature T3 is the freezing point, and a temperature-time target characteristic 30 from the pouring point coagulation time C2 to the pouring start time A of the next cycle, And is stored in the memory of the control means 21.

  Further, for the knuckle arm 4, the set temperature is a set temperature 32 (temperature T2) which is a constant value from the pouring start time A to the maximum temperature reaching time B, and the freezing point (temperature T3) below the maximum temperature reaching time B. Temperature-time target characteristic 33 until the knuckle arm solidification time C1 and the temperature-time target characteristic 34 leading to a gradual decrease from the knuckle arm solidification time C1 to the temperature-time target characteristic 30. And a temperature-time target characteristic 30 in a continuous control graph, which is stored in the memory of the control means 21.

  That is, the portion that becomes the knuckle 1 for an automobile including the knuckle arm 4 is rapidly cooled after pouring, whereas the riser portion 15 is set to be slowly cooled to the freezing point (temperature T3). .

  The program stored in the control means 21 opens the automatic flow control valves 16a and 17a if the detected temperature of the thermocouples 19 and 20 (the temperature of the mold 10) is higher than the set temperature stored in the memory. Then, if the cooling water is circulated through the mold 10 and the detection temperature of the thermocouple 20 of the mold 10 is low, the automatic flow control valves 16a and 17a are closed to stop the flow of the cooling water to the mold 10. Yes.

As shown in FIG. 3, the mold 10 controlled based on the program of the control means 21 rapidly rises from the temperature T1 at the pouring start time A and reaches a set temperature 32 (temperature T2) near the maximum temperature reaching time B. Controlled based on Then, the temperature of the riser unit 15 is controlled based on a temperature-time target characteristic 31 that gradually decreases toward the temperature T3 at the pouring point C2 and further continues from the set temperature 32. Then, the temperature-time target characteristic 31 is controlled based on the temperature-time target characteristic 30 that is rapidly cooled from the gate solidification point C2 to the temperature T1 at the pouring start point A of the next cycle.
On the other hand, the temperature of the knuckle arm 4 rapidly decreases from the vicinity of the maximum temperature reaching point B toward the temperature T4 at the knuckle arm solidification point C1 according to the temperature-time target characteristic 33, and further from the temperature T4 to the temperature-time target characteristic 34. Accordingly, the temperature gradually decreases toward the temperature-time target characteristic 30.

  Note that the temperature T1 at the pouring start point A, which is important in the gravity casting method, is controlled so as to always be a constant optimum pouring temperature in each cycle.

In the present embodiment, when the temperature-time target characteristic 33 from the maximum temperature reaching point B to the knuckle arm solidification point C1 is desired to be a relatively gentle cooling characteristic, a test in which cooling water is not circulated depending on the selection of the coating type. Since it can be made almost the same as the actual measurement value of casting, a desired cooling rate can be obtained without passing cooling water between B and C1. In addition, when it is desired to make the cooling rate between B and C1 have a relatively steep cooling characteristic, a coating mold is not provided, and if necessary, the automatic flow control valve 16a is opened to allow the cooling water to flow through the cooling flow path 16. Thus, a desired cooling rate can be obtained.
In contrast, the cooling rate of the riser unit 15 is slow, and the cooling rate of the temperature-time target characteristic 31 is set to 180 ° C./min or less. The cooling rate of the riser unit 15 is more desirably 100 ° C./min or less.

  Furthermore, the program stored in the control means 21 sets a temperature monitoring area for monitoring whether the temperature of the mold 10 detected by the thermocouples 19 and 20 is too high or too low with respect to the set temperature. Has been.

  The temperature monitoring area of the present embodiment includes a first monitoring area 51 and a second monitoring area 52 corresponding to each of A-B, B-C1, B-C2, C1-D, and C2-A. The third monitoring area 53, the fourth monitoring area 54, and the fifth monitoring area 55 are divided.

  In the first monitoring region 51, since the temperature of the mold 10 rises rapidly, and in this region, control for hardly circulating the cooling water is not performed, so the set temperature 32 (temperature T2 when the maximum temperature is reached B). A temperature that is slightly higher than the temperature T1 is a certain upper limit temperature 51a, and a temperature that is slightly lower than the temperature T1 that is the optimum pouring start temperature is a certain lower limit temperature 51b.

  In the second monitoring area 52, an upper limit temperature-time characteristic 52a and a lower limit temperature-time characteristic 52b that change according to the temperature-time target characteristic 33 that is a set temperature are set. The upper limit temperature-time characteristic 52 a and the lower limit temperature-time characteristic 52 b are set in parallel to the temperature-time target characteristic 33. In the second monitoring region 52, since the temperature-time target characteristic 33 is set so as to be rapidly cooled to the temperature T4, the actual temperature of the mold 10 also varies relatively (that is, temperature− The upper limit temperature-time characteristic 52a and the lower limit temperature-time characteristic 52b are symmetrical with respect to the set temperature-time target characteristic 33 and have a relatively wide temperature range. Set in the monitoring area.

  In the third monitoring region 53, an upper limit temperature-time characteristic 53a and a lower limit temperature-time characteristic 53b that change according to the temperature-time target characteristic 31 that is a set temperature are set. The upper limit temperature-time characteristic 53 a and the lower limit temperature-time characteristic 53 b are set in parallel to the temperature-time target characteristic 31. In this third monitoring region 53, since the variation in temperature is small, the upper limit temperature-time characteristic 53a and the lower limit temperature-time characteristic 53b are symmetrical with respect to the set temperature-time target characteristic 31 and have a relatively narrow width. It is set in the temperature monitoring area.

  In the fourth monitoring region 54, an upper limit temperature-time characteristic 54a and a lower limit temperature-time characteristic 54b that change according to the temperature-time target characteristic 34 that is a set temperature are set. The upper limit temperature-time characteristic 54 a and the lower limit temperature-time characteristic 54 b are set in parallel to the temperature-time target characteristic 34. In the fourth monitoring region 54, since the temperature variation is small, the upper limit temperature-time characteristic 54a and the lower limit temperature-time characteristic 54b are symmetrical with respect to the set temperature-time target characteristic 34 and have a relatively narrow width. It is set in the temperature monitoring area.

  In the fifth monitoring area 55, an upper limit temperature-time characteristic 55a and a lower limit temperature-time characteristic 55b that change according to the temperature-time target characteristic 30 that is a set temperature are set. In the fifth monitoring region 55, the temperature-time target characteristic 30 is set so as to rapidly cool to the temperature T1 that is the optimum pouring start temperature between C2 and A, so that the actual temperature of the mold 10 is reached. Since the variation is relatively large (that is, the deviation from the actual value with respect to the temperature-time target characteristic 30 is large), the upper limit temperature-time characteristic 55a and the lower limit temperature-time characteristic 55b are the temperature-time target characteristics of the set temperature. The temperature monitoring region is set symmetrically with respect to 30 and having a relatively wide width.

  By controlling the temperature of each part between such monitoring areas 51 to 55, the casting product 12 has a quality having stable material characteristics as a whole. In particular, there is a difference in the cooling rate (solidification rate) between the portion that becomes the knuckle 1 for an automobile including the knuckle arm 4 and the riser portion 15, and the riser portion 15 solidifies later, so that the hot water is effectively applied. be able to. In particular, the mold 10 forms the cavity 11 with the bearing support 2 facing upward, and the riser 15 is provided continuously on the bearing support 2, so that the bearing support 2, Via the knuckle arm 4, the hot water can be sent relatively uniformly to the entire knuckle 1 for an automobile, and the quality is stabilized.

  The cast product 12 cast as described above is cut into a product portion 12A and a riser portion 15 as shown in FIG. 4 (a), and as shown in FIG. 4 (b), the fitting holes 2a, And other parts are machined to form a knuckle 1 for an automobile.

The automobile knuckle 1 manufactured as described above has material characteristics as shown in FIG. 5 according to the solidification rate when an aluminum alloy of A356 alloy is used as a material. FIG. 5 shows the solidification rate on the horizontal axis, the elongation, DASII value on the horizontal axis, and the vertical axis showing the tensile strength and proof stress in a graph, corresponding to the solidification rate.
As shown in FIG. 5, the tensile strength has sufficient strength at break when the solidification rate is 180 ° C./min or more, and the press-fit portion or tightening when the proof stress is 180 ° C./min or more. It has sufficient strength in the part.
Further, when the solidification rate is 180 ° C./min or more, the DASII value becomes smaller than 32 μm, and a high strength and toughness can be obtained by the fine structure.
Therefore, the knuckle 1 for automobiles of the present invention manufactured by the above-described manufacturing method can secure a necessary and sufficient strength, and can obtain sufficient durability even if the ball bearing 8 (see FIG. 1) supporting the wheels is press-fitted. be able to. Further, since the elongation is 8% or more, energy can be sufficiently absorbed at the time of breakage.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be implemented with appropriate modifications.
For example, in the above-described embodiment, the cooling medium is cooling water, but various types of temperature control fluids that are generally used can be used as long as the temperature of the mold can be controlled efficiently. In the above embodiment, the cooling water is controlled by ON-OFF control when the automatic flow control valve is opened and closed. However, the automatic flow control valve is stored in the memory by adjusting the flow rate in a plurality of stages. The temperature can be controlled smoothly according to the program.

  Further, in the above embodiment, for ease of explanation, the cooling circuit using two cooling channels and a thermocouple is used, but the number of cooling channels is not particularly limited.

In addition, in the manufacturing method of the embodiment, the knuckle for an automobile is configured by an aluminum alloy, but the present invention is not necessarily limited to this, and even when aluminum or a steel material is employed, it has a microstructure and has strength and toughness. It can also be a knuckle for automobiles.
Moreover, the manufacturing method by rapid solidification can utilize water-cooling solidification control with a heat insulation coating mold, casting without a heat insulation coating mold, embossing by metal coating, a reduction casting method, and the like. The reduction casting method is a casting method in which a reducing gas, for example, a magnesium gas having a higher reducing property than aluminum, is introduced into a cavity to prevent oxidation of the surface of aluminum and improve the circumference of the hot water. Details of the reduction casting method are described in, for example, Japanese Patent No. 3422969.

The knuckle for automobiles was cast while controlling solidification according to the method for producing knuckle for automobiles described in the embodiment, and the material properties of each part were measured.
At the time of casting, the solidification rate of the riser portion was 90 ° C./min, and the solidification rates of the other knuckle body portions were 300 ° C./min. The material used for casting was an aluminum alloy, and its composition was A35C.
By this casting, an automotive knuckle having a shape as shown in FIG. 6A was obtained, and a test piece was cut out from the knuckle arm or the bearing support portion (see symbols S1 to S7 shown in FIG. 6A).
Ten test pieces were obtained from one automobile knuckle and measured for tensile strength, yield strength, and elongation. These measurement results are plotted in FIG. 6 (b) and FIG. 6 (c).
As shown in FIG. 6B, in all the test pieces, the tensile strength was 280 MPa or more, and the elongation was 8% or more.
Moreover, as shown in FIG.6 (c), yield strength became 170 Mpa or more in all the test pieces.

It is an external appearance perspective view of the knuckle for motor vehicles. It is a schematic cross section of the casting_mold | template for manufacturing the knuckle for motor vehicles of this invention. It is a graph which shows the relationship between time and temperature in casting of the knuckle for motor vehicles concerning embodiment. It is a figure which shows the post-process of a cast product, (a) shows the division | segmentation process of a riser part, (b) shows a machining process. It is a graph which shows the relationship between a solidification rate and material characteristics. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining an Example, (a) is a figure which shows the position which cut out the test piece, (b) is a figure which shows the relationship between tensile strength and elongation, (c) is a figure which shows the relationship between proof stress and elongation. is there.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Automotive knuckle 2 Bearing support part 3 Mounting boss 4 Knuckle arm 8 Ball bearing 10 Mold 11 Cavity 12 Cast product 15 Riser part 16 Cooling flow path 17 Cooling flow path

Claims (10)

A knuckle for automobiles made of aluminum and made of aluminum or an alloy thereof,
An automobile knuckle characterized by having an average DASII value of 10 to 34 μm in each component.   The knuckle for automobiles according to claim 1, wherein each of the constituent parts has an average tensile strength of 260 MPa or more, an average yield strength of 170 MPa or more, and an average elongation of 8% or more.   The knuckle for automobiles according to claim 1 or 2, wherein the knuckle for automobiles is manufactured by a gravity casting method or a low pressure casting method.   The automobile knuckle according to any one of claims 1 to 3, which is manufactured by a reduction casting method. A method for producing an automotive knuckle by casting,
Injecting molten metal into the cavity forming the knuckle for automobiles,
A method for producing a knuckle for an automobile, wherein the molten metal injected into the cavity is cooled at 180 to 2200 ° C./min. A method for manufacturing an automobile knuckle by casting an automobile knuckle,
A knuckle body that forms the knuckle for automobiles and a riser portion that is continuous with a bearing support portion that accommodates a wheel support component in the knuckle body are formed as cavities.
Injecting molten metal into the cavity,
A method for manufacturing a knuckle for an automobile, wherein the molten metal is cooled by setting an average solidification rate of a portion corresponding to the knuckle body higher than an average solidification rate of the riser part.   The average kneading rate of a portion corresponding to the knuckle body is 180 to 2200 ° C / min, and the average coagulation rate of the riser portion is less than 180 ° C / min. Production method.   The method for manufacturing a knuckle for an automobile according to any one of claims 5 to 7, wherein aluminum or an alloy thereof is used as the molten metal.   The method for manufacturing a knuckle for an automobile according to any one of claims 5 to 8, wherein the casting method is a gravity casting method or a low pressure casting method.   The method for manufacturing a knuckle for an automobile according to any one of claims 5 to 9, wherein the casting method is a reduction casting method.

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