JP3331528B2 - Injection method of horizontal die casting machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection method for a horizontal die casting machine in which air entrapment is minimized.

2. Description of the Related Art When mass-producing aluminum cast products, FIG.
The horizontal die casting machine shown in FIG. According to this machine, molten metal is supplied into the injection sleeve 4, injected at a low speed by the injection plunger 5, filled into the cavities 3 of the molds 1 and 2 at a high speed, and subjected to pressure molding to obtain an aluminum cast product. be able to. In die casting in Japan, the inner diameter of the injection sleeve is 5 to 15 cm, and the initial volume filling rate of the molten metal is often 20 to 30%. Here, the initial volume filling rate is the sectional area of the injection sleeve and the injection three.
The initial ratio of the cross-sectional area of the molten metal filled in the tube is 100%
(Hereinafter, the initial volume filling rate is simply referred to as the filling rate). As shown in FIG. 2, the die casting is roughly divided into a low-speed injection step A, a high-speed injection step B, and a pressure increase step C.
Consists of

[0002] The role and value of the speed of the injection plunger differ greatly in the first half and the second half of the process in which the tip of the molten metal reaches the mold gate. Low-speed injection process A
At the stage where the molten metal filled in the injection sleeve is filled into the cavity as soon as possible, if the injection plunger is moved quickly, the air entrainment increases and the quality is adversely affected. Must. The high-speed injection step B is a step of filling the cavity with the molten metal having a filling rate of 100% at a high speed, and the pressure-increasing step C is for improving the density of the casting. The entrainment of air in the casting is divided into the first half of low-speed injection and the second half of high-speed injection, and the ratio is 2: 1. In particular, air entrapment during low-speed injection is a problem. Was. Regarding the standard for setting the constant low-speed injection speed, Dr. University of Rhode Island in the United States
Lester and W.C. Garber used a high-speed movie and the water analogy method in a magazine "Diecast Engineer" published in May and June 1982 to investigate the behavior of the molten metal in the injection sleeve as water.

As a result, air entrainment in the injection sleeve depends on plunger speed, initial filling rate, and injection three.
It found that depend blanking diameter.

In general, when a plunger is moved at a constant speed with respect to a molten metal having a predetermined filling rate, as shown in FIG. 3, a wave is formed on the front surface, rises to a certain height, and proceeds in the traveling direction of the plunger. Go by. In this case, it is preferable that the waves travel without the molten metal getting into the air. They set the plunger speed at the time when the molten metal comes into contact with the uppermost part of the inner surface of the sleeve without entraining air as shown in FIG.
In the injection sleeve, the relationship between the wave speed and wave height
It was expressed as the relationship between the initial filling rate of the molten metal , the plunger speed and the plunger diameter, and was a recommended value for a low injection speed. As an example of the critical injection speed, the injection sleeve diameter D = 1 to 6
(In), experiments and observations of the critical injection speed in the range of filling ratio rv = 55 to 95% were performed.

According to the results, when the filling ratio rv is 50% or more, the liquid can be raised to the uppermost portion of the sleeve on the front surface of the plunger and sent forward at almost the critical injection speed as expected. When the rv was less than 50%, the water that had swelled upward was immediately ejected forward and dropped as shown in FIG. 6, causing severe air entrapment. As an injection method for varying the low-speed injection speed, there is a constant acceleration injection method in which the speed is increased at a constant acceleration from zero as recommended by Buehler, as shown in FIG. It is known that it is smooth and hard to collapse.

[0006] Apart from the above-mentioned report, the present inventors have published a low-speed injection speed in the paper of the 1988 Japan Die Casting Conference entitled "Theory and Practice of Air Mixing in the Injection Sleeve". In this paper the present inventors describe the filling rate r
v If is less than 50%, that is to produce the entrainment of air into the molten metal in the effects of wave speed Vas long wave of the molten metal in the sleeve when not use critical injection speed Vc1
In the case where the low injection speed is obtained, the critical injection speed Vc1
(M / s) was proposed to be obtained from the following equation.

Vc1 = 1/100 · √ ( 2 · g · (D−
Y) · (100−rv) / (100 + rv) ) Y = Y (D, rv) D: Injection sleeve inner diameter (cm), g: Gravity acceleration (c)
m / s ² ) Y: initial filling height (cm), rv: filling rate (%) Here, g is constant, and the initial filling height Y is determined by the inner diameter D of the injection sleeve and the filling rate rv. The injection speed Vc1 is determined by numerical calculation.

In this paper, the theoretical wave speed of a long wave of a minute height to be generated on the molten metal surface in the injection sleeve is:
A function Vas = Vas (D, rv) is obtained from the filling rate rv (10% ≦ rv <50%) determined by the amount of molten metal to be filled in the injection sleeve having the inner diameter D, and the inner diameter D and the filling rate rv of the injection sleeve. Can be obtained from

The wave speed Vas (m / s) of the long wave of the molten metal in the sleeve
Is determined by the following equation.

Vas = 1/100 · √ ( g · A / T ) A = A (D, rv) T = T (D, rv) A: cross section area of molten metal at filling rate rv (cm ² ) T : Width of cross section of molten metal at filling rate rv (cm) D: Inner diameter of injection sleeve (cm) Further, wave speed when a minute wave is formed on the surface of molten metal,
As a result of theoretically examining the wave speed Vas (m / s) of a so-called long wave by the present inventors, the wave speed Vas increases as the filling rate rv increases, and the wave speed Vas (m / s) of the long wave and the critical injection speed Vc1 ( m / s), the filling rate rv is about 4
Long wave of the wave speed Vas at 7% value as (m / s) and values of the critical injection speed Vc1 is found to be consistent. FIG. 8 shows the relationship among the filling rate rv, the wave speed Vas of a long wave, the critical injection speed Vc1, and the injection speed Vc3 using a folded wave. Using the concept of the wave speed of a long wave, it can be understood that when the filling rate rv is small, a severe air entrainment occurs.

The wave speed Vas of a long wave is the speed of a surface wave corresponding to the speed of sound propagating in the air.
The nature of the waves formed by the plunger pressing can be understood. That is, the plunger speed VL is changed to the critical injection speed V
When injecting at a constant speed at c1, if the filling rate rv is 47% or more, there is a relationship of Vas−Vc1> 0.
At a slower speed, it is injected forward, a thin layer of molten metal at the lower front part of the plunger is spread out horizontally, and a stable wave can travel at a constant wave height.

When the filling rate rv is less than 47%, the critical injection speed Vc1 is faster than the long wave speed Vas, and Vas-Vc1.
Since the relation of <0 is satisfied, thin layers of the molten metal on the lower part of the front surface of the plunger are vertically stacked one after another at a speed higher than the wave speed Vas of the long wave, and a swelling of the wave is formed but cannot spread. Therefore, as shown in FIG. 6, the front of the plunger is formed with a swelling of waves in the vertical direction, and the wave front is pushed forward and falls, causing violent air entrainment.

Further, as an example of the injection method, a small wave is formed at a constant speed which is considerably lower than the critical injection speed Vc1, and the wave travels, is reflected on the mold side of the cylinder, and returns ascending. However, there is a method in which the wave is turned up at the tip of the plunger and the top of the wave is brought into contact with the top of the cylinder. According to this method, the constant plunger speed Vc3 using the folded wave can be obtained by repeatedly using a method of numerically solving the wave equation.

Further, the value of the plunger speed Vc3 is about 1/3 of the critical injection speed Vc1. It is a speed that is qualified to be the recommended value of the low speed injection speed as well as the critical injection speed, but if such a low speed is used when the filling rate rv is small,
It is not suitable for practical use because many solidified pieces are generated in the molten metal during injection.

[0015]

In the low-speed injection method at a constant speed, when the filling rate of the injection sleeve is 50% or more, the liquid is injected almost as expected at the critical injection speed Vc1 at the top of the injection sleeve at the front surface of the piston. It was able to extrude forward, but when the filling ratio rv was 50% or less, the liquid that had swelled upward immediately dropped forward, causing intense air entrainment and quantitatively producing good products. It was difficult to do.

In the constant acceleration injection method of Bühler, no suitable acceleration value is disclosed, so that the low injection speed when the filling rate is less than 50%, which is frequently used, is intuitive, experience, and trial and error. And the situation had to be determined, and the establishment of that theory was required.

The present invention has been made in view of the conventional problems, and an object thereof is to provide a filling rate rv (10% ≦ rv <4).
7%) , in the injection method of the horizontal die casting machine that injects the molten metal at a constant speed or a variable speed at a low speed , with less labor and faster than in the state where values were determined by trial and error from conventional intuition and experience. , Air entrainment and mixing of coagulated pieces
To provide a low-speed injection method for obtaining a less high-quality die-casting product.

[0018]

The present invention has the following means to solve the above-mentioned problems.

The first means is to hold the injection control valve of the low-speed injection hydraulic circuit at a constant opening, inject the molten metal filled in the injection sleeve at a low speed by the injection plunger, and then fill the cavity at a high speed and increase the pressure. Filling rate rv (10% ≦ rv <) determined by the amount of molten metal to be filled into the injection sleeve having an inner diameter D in the injection method of the horizontal die casting machine controlled as described above.
47%) and the theoretical wave speed Vas = Vas (D, r) of a long wave of a minute height to be generated on the melt surface from the inner diameter D and the filling rate rv.
v) is determined, and the molten metal is injected at a low speed at a constant speed with a value 0.9 to 1.2 times the theoretical wave speed of the long wave as a low injection speed.

The second means is such that the opening degree of the digital injection control valve of the low-speed injection hydraulic circuit is made variable, and after low-speed injection, the molten metal filled in the injection sleeve is charged at a high speed by the injection plunger and the pressure is increased. In the injection method of a horizontal die casting machine, a filling rate rv (10% ≦ rv <47) determined by an amount of molten metal to be filled into an injection sleeve having an inner diameter D.
%) And the theoretical wave velocity Vas of a long wave having a minute height to be generated on the melt surface from the inner diameter D of the injection sleeve and the filling rate rv.
= Vas (D, rv), and the theoretical wave speed of this long wave is 0.8 to
A value of 1.1 times is set as the initial value of the low speed injection speed, and the moving speed of the injection plunger where the top of the molten metal contacts the uppermost portion of the injection sleeve, based on the inner diameter D of the injection sleeve and the filling rate rv, that is, The critical injection speed VC1 = VC1 (D, rv) is determined, and the injection speed is increased so that a value 0.9 to 1.2 times the critical injection speed becomes the final value of the low-speed injection speed.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the "low-speed injection method" of the present invention will be described below with reference to the drawings.

The outline of the device commonly used in the first embodiment and the second embodiment is as follows.

FIG. 1 shows a configuration of a molten metal injection section of a horizontal die casting machine to which the present invention is applied.

Reference numerals 1 and 2 denote dies, and reference numeral 3 denotes a cavity formed by the dies 1 and 2. Reference numeral 4 denotes an injection sleeve fixed to the rod 8a of the injection cylinder 8, and the injection sleeve 4
Is fitted with an injection plunger 5. Reference numeral 6 denotes an injection control valve for controlling the injection speed of the injection plunger 5, and the injection control valve 6 is a controller 7 of a die casting machine having a built-in arithmetic unit.
Is controlled by When the injection control valve 6 is a digital injection control valve, an operation signal is generated by the controller 7 and is given to the digital injection control valve 6. The memory in the controller 7 has a formula for calculating the filling rate rv (%) of the molten metal from the molten metal input amount V (cm ³ ) given to the injection sleeve 4, and a critical injection speed Vc1 based on the filling rate rv (%). An equation for calculating (m / s) and an equation for calculating the long wave velocity Vas (m / s) from the filling rate rv (%) are stored. Using this apparatus, the filling rate rv (%), the critical injection speed Vc1 (m / s), and the wave speed Vas (m / s) of the long wave shown in the following first and second embodiments are obtained. By injecting at this injection speed, it is possible to inject the molten metal into the cavity 3 in which the entrainment of air in the injection sleeve 4 is minimized.

[First Embodiment] This is an example in which a molten metal is injected at a constant low injection speed at a long wave speed Vas (m / s). Practically, in order to increase the productivity, the injection is performed early even if the wave breaks a little, and a value obtained by increasing the injection speed by a minute amount than this speed is used as the center value so as not to form an empty space above the cylinder.

Controlling a suitable injection speed VL at a constant speed
The procedure for calculation in step 7 is as follows. Filling ratio rv determined by the amount of molten metal to be filled into the injection sleeve of inner diameter D
(10% ≦ rv <47%), and from this inner diameter D and the filling rate rv, a theoretical wave velocity V of a long wave having a minute height to be generated on the melt surface.
as (m / s) is obtained by the following equation.

Vas = 1/100 · √ ( g · A / T ) A = A (D, rv) T = T (D, rv) A: Cross section area of molten metal at filling rate rv (cm ² ) T : The width (cm) of the surface of the section of the molten metal at the filling ratio rv D: The inner diameter of the injection sleeve (cm) The input signal of the digital injection control valve 6 is controlled based on the calculated value of the low injection speed VL. The injection control valve 6 of the low-speed injection hydraulic circuit is maintained at a constant opening to control the speed of the injection plunger 5 to the low injection speed VL. Note that the value 0.9 to 1.2 times the wave speed Vas (m / s) is set to the low injection speed VL.
(M / s).

After the low-speed injection, the cavity is filled at a high speed and the pressure is controlled to increase, so that a die-cast product with stable quality can be obtained.

When the filling rate rv is less than 47%, the injection method in which the plunger is moved at the long wave speed Vas is a wave having a stable swell as shown in FIG. Can be launched. In this case, the air content is considerably lower than in the case where the critical injection speed is used, and the amount of solidified pieces deposited is also smaller than in the case where the return wave is used. [Second Embodiment] The present embodiment is a low-speed injection method in which the filling rate rv is 47% or less, and the opening of the digital injection control valve 6 set in the low-speed injection hydraulic circuit is made variable to increase the speed.

Using a horizontal die casting machine equipped with a digital injection control valve 6 capable of setting a low-speed injection speed to a variable speed, the initial speed is set to a speed slightly less than the long-wave wave speed Vas. At a position slightly before the plunger position that arrives at the position, the final speed is set to be slightly higher than the critical injection speed Vc1 obtained from the filling rate rv. The injection speed in the middle is set so that the increase in the position of the plunger and the increase in the injection speed maintain a proportional relationship. Filling rate
An initial value VL1 and a final value VL2 of a suitable low-speed injection speed of a variable speed are calculated from rv. Next, a filling rate rv (10% ≦ rv) determined by the amount of molten metal to be filled into the injection sleeve having the inner diameter D.
<47%), and the theoretical wave velocity Vas = Vas (D, rv) of a long wave having a minute height to be generated on the molten metal from the same inner diameter D and the filling rate rv.
0.8 to 1.1 times the initial value of the low-speed injection speed VL1
Set as Initial value VL1 is plunger stroke 0
The initial value V of the low-speed injection speed at the plunger speed in (cm)
L1 is obtained from the following equation which gives the wave speed Vas (m / s) of the long wave of the molten metal in the sleeve.

Vas = 1/100 · √ ( g · A / T ) A = A (D, rv) T = T (D, rv) A: Cross-sectional area (cm ² ) of the molten metal at the filling rate rv : Surface width of the cross section of the molten metal at filling rate rv (cm) D: Inner diameter of injection sleeve (cm) Final value VL2 is the plunger speed just before the gate of the molten metal, and the critical injection speed Vc1 ( m / s) from the following equation.

Vc1 = 1/100 · √ ( 2 · g · (D−
Y) · (100−rv) / (100 + rv) ) Y = Y (D, rv) D: Injection sleeve inner diameter (cm), g: Gravity acceleration (c)
m / s ² ) Y: Initial filling height (cm), rv: Filling rate (%) Obtain the final value VL2 of the low-speed injection speed from the above formula, and set it to 1.0 to 1.2 times the injection speed. . Then, based on the initial value VL1 and the final value VL2, the intermediate data is provided with data so as to increase the speed of the intermediate data at a constant acceleration, or data which gives an increase in speed in proportion to the increase in position. To give. Initial velocity V from the initial position of the plunger
Start moving at L1, increase the speed in proportion to the increase of the plunger position, and perform the speed increase pattern that reaches the corresponding final speed VL2 slightly before the plunger position when the tip of the molten metal reaches the gate. The calculated input signal of the low-speed injection unit is calculated and automatically set so as to be given to the digital injection valve. The speed increase control is performed so that 0.9 to 1.2 times the critical injection speed becomes the final value of the low speed injection speed. This wave is theoretically produced smoothly by the injection plunger which continuously increases in speed, but in practical use, it is generated by intermittent acceleration of the plunger as shown in FIG. The reason why the waves do not collapse even if the speed is increased when the filling rate rv is less than 47% is that when the waves on the front face of the plunger are slightly raised, the apparent filling rate of the portion increases and the wave speed increases. In practice, a sufficient effect can be obtained even with a variable speed low speed injection by roughly three stages of coarse speed increase.

[0033]

According to the present invention, there is provided a low-speed injection control method for a horizontal die casting machine for injecting molten metal filled in an injection sleeve at low speed while maintaining an injection control valve of a low-speed injection hydraulic circuit at a constant opening. As soon as the amount of molten metal gives the filling rate, a suitable value of the low-speed injection speed with less air entrainment and generation of coagulated pieces is shown, and the automatic setting of the low-speed injection speed becomes possible. A high-quality die-cast product can be obtained quickly and with less labor than a state where values are determined by trial and error from experience.

[Brief description of the drawings]

FIG. 1 shows a configuration of a molten metal injection section of a horizontal die casting machine which is an object of the present invention.

FIG. 2 shows a normal injection speed control pattern.

FIG. 3 shows a waveform generated by normal constant speed injection.

FIG. 4 shows a waveform of a molten metal at a normal critical injection speed VCL1.

FIG. 5 shows the collapse of the melt wave when the molten metal is injected at a speed higher than the critical injection speed VC1.

FIG. 6 shows the breaking of a wave of a molten metal when the molten metal is ejected at a speed higher than the wave speed Vas of a long wave.

FIG. 7 shows a waveform of a molten metal generated at the time of accelerated injection.

FIG. 8: Filling ratio rv, critical injection speed Vc1, and wave speed V of long wave
It is a graph which shows the relationship of as and injection speed Vc3 which uses a folding wave.

FIG. 9 shows a waveform of a molten metal when the molten metal is injected at a speed of a long wave wave speed Vas of the present invention.

FIG. 10 shows a waveform of a molten metal when a long-wave wave velocity Vas of the present invention is set as an initial value, a velocity critical injection speed is set as a final value, and injection is performed at an increased speed in the middle.

[Explanation of symbols]

 Reference Signs List 1 mold 2 mold 3 cavity 4 injection cylinder 5 injection plunger 6 injection control valve 7 controller

Claims (2)

(57) [Claims] 1. An injection control valve of a low-speed injection hydraulic circuit is maintained at a constant opening, and after a molten metal filled in an injection sleeve is injected at a low speed by an injection plunger, the cavity is filled at a high speed and the pressure is increased. In the injection method of a horizontal die casting machine, an initial volume filling ratio rv (10% ≦ rv) determined by an amount of molten metal to be filled into an injection sleeve having an inner diameter D.
<47%), and the theoretical wave velocity Vas of a long wave having a minute height to be generated on the melt surface from the inner diameter D and the initial volume filling rate rv.
= Vas (D, rv), and the theoretical wave speed of this long wave is 0.9 to
An injection method for a horizontal die casting machine, characterized in that the molten metal is injected at a low speed at a constant speed, with a value of 1.2 times as a low injection speed. 2. A horizontal die-casting machine in which the opening degree of a digital injection control valve of a low-speed injection hydraulic circuit is made variable, and after low-speed injection, molten metal filled in an injection sleeve is filled at a high speed by an injection plunger and the pressure is increased. In the injection method, an initial volume filling rate rv (10% ≦ rv <47%) determined by an amount of molten metal to be filled in an injection sleeve having an inner diameter D is obtained, and an initial volume filling rate rv on the molten metal surface is determined from the inner diameter D of the injection sleeve and the initial volume filling rate rv. Wave velocity V of a minute long wave to be generated
as = Vas (D, rv) asking to set the 0.8 to 1.1 times the value of the long-wave theoretical wave speed Vas as an initial value of the slow injection speed, the inner diameter D and the initial volume filling of the injection sleeve The moving speed (critical injection speed) Vc of the injection plunger at which the top of the molten metal contacts the top of the injection sleeve from the ratio rv.
1 = Vc1 (D, rv) is obtained, and the value of 0.9 to 1.2 times the critical injection speed is increased so as to become the final value of the low speed injection speed. Injection method.