JPS6362302B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting galling of chips in a sleeve of a molten metal injection plunger used in a die casting machine.

In die-casting, as shown in FIG. 1, when forming a product with molten metal in the cavity 18, first,
The molten metal is supplied into the injection sleeve 12, and then a plunger tip 13 provided in the injection sleeve is advanced by hydraulic pressure at high pressure and at low and high speeds to inject the molten metal in the sleeve into the cavity to perform die casting.

However, if the positional relationship between the injection sleeve and the plunger tip becomes eccentric due to an installation error of the die-casting machine or vibrations during operation, or if there is insufficient lubricant, or if the die-casting machine 10 has been operated for a long time. If this happens, the plunger tip 13 will wear out, and solidified metal particles may adhere or exist within the injection sleeve and become trapped between the plunger 13 and the inner wall of the injection sleeve 12, resulting in so-called galling.

If this kind of galling occurs, the plunger tip will not be able to perform normal injection operation.
Since the predetermined stable injection speed is not achieved, the so-called injection plunger becomes shaky and operates in a static manner, causing the molten metal in the injection sleeve to ripple greatly during injection, causing a drop in molten metal temperature. This may cause air to be entrained in the molten metal, resulting in various defects such as deterioration of the molten metal, formation of cavities in the finished product, and failure to obtain a predetermined strength of the finished product.

Therefore, early detection of the galling that causes this defect and maintenance of the plunger tip and injection sleeve will not only help produce high-quality die-cast products but also prevent damage to the casting mechanism. Furthermore, this is an important matter in terms of safety measures for operators of die-casting machines. Therefore, there have been various galling detection methods.

Conventional detection methods include, for example, measuring the amount of fluid pressure in the drive fluid circuit of the plunger mechanism when the plunger tip is retracted or ejected (approximately equivalent to the movement resistance of the plunger tip), and measuring the amount of change in the fluid pressure (hydraulic pressure). There are methods to measure galling (differential amount) and detect galling.
In both cases, galling was determined based on only one measured quantity.

In these detection methods, it is necessary to determine how long the galling condition continues within the sleeve, or whether the plunger tip exhibits a stick-like movement phenomenon when moving in the galling condition, that is, the degree of risk of galling. In addition, there were drawbacks in making accurate measurements, such as detecting the surge pressure that occurs at the time of speed change as occurrence of galling when it is not actually galling.

The present invention eliminates the drawbacks of the conventional galling detection method and measures the hydraulic pressure of the operating cylinder of the driving hydraulic pressure circuit of the injection plunger, thereby determining the magnitude of the resistance between the injection sleeve and the plunger tip, that is,
By measuring the magnitude of galling and the differential amount of the hydraulic pressure, it is possible to understand the progress of galling or the stepping phenomenon of the plunger tip due to the progress of galling, and also to determine the length of the continuation of abnormal hydraulic pressure values. The present invention relates to a method for determining the degree of galling risk by measuring the degree of galling.

That is, the method according to the present invention measures the hydraulic pressure of the operating cylinder 15 that operates the injection plunger 11 including the plunger tip 13 and the differential value of the hydraulic pressure, and when this hydraulic pressure differential value exceeds a predetermined value, The degree of galling of the die-casting injection plunger mechanism is determined by measuring the injection stroke or the travel time of the injection plunger when the hydraulic pressure continuously appears above a predetermined value, and thereby determining the danger of the degree of galling of the injection plunger mechanism. This is a determination method.

That is, a specific example of the method according to the present invention is described in the second
As shown in the figure, the injection plunger operating cylinder 15
The pressure detector pick-up element 21 detects the liquid pressure, the amplifier 22 amplifies it, sends the amplified pressure signal to the first comparator 25, and the differential circuit 2
3 to the second comparator 26.

By the way, the first comparator 25 compares a predetermined voltage set by the first setter 27 for setting the hydraulic pressure abnormal value with the pressure signal voltage amplified by the amplifier 22, and the pressure signal voltage is A comparator 2 that emits a first output signal when the voltage is higher than a predetermined voltage, that is, when the hydraulic pressure of the operating cylinder 15 exceeds a predetermined value.
It is 5.

Then, the second comparator 26 compares the predetermined voltage set by the second setter 28 that sets the abnormal galling progress value with the differential signal detected by the differentiating circuit 23, and the differential signal is greater than or equal to the predetermined value. That is, the comparator 26 generates a second output signal when the hydraulic pressure change of the operating cylinder 15 is a sudden change exceeding a predetermined value, that is, when a stick-like operation is performed.

Further, both the first output signal and the second output signal described above are input to the first AND circuit 31, and the first
First output signal from comparator 25 Second AND circuit 3
Input to 1 terminal of 2 as a negative input.

Further, the output from the first AND circuit 31 is passed through the monostable multivibrator 33 to the second AND circuit 3.
2 and the second AND element 32 as a latch signal of the first latch counter 36.
The output becomes the latch signal of the second latch counter 37.

Incidentally, a pulse signal corresponding to the plunger position from the position detection pulse generator 35 of the injection plunger 13 is input to the first latch counter 36 and the second latch counter 37.

When a latch signal is input from the first AND element 31, the first latch counter 36 holds the plunger position signal at that time in the first latch counter 36, and at the same time inputs the numerical value to the arithmetic circuit 41.
When a latch signal is input from the second AND element 32, the second latch counter 37 holds the current plunger position signal in the second latch counter 37, and at the same time transmits the value to the arithmetic circuit 41. . That is, the first latch counter 36 detects the injection distance from when the plunger starts until galling occurs, and the second latch counter 37 detects the injection distance from when the plunger starts until galling ends.

Therefore, the arithmetic circuit 41 uses the signal sent from the first latch counter 36 and the second latch counter 37.
When a signal sent from
send a signal to. A third comparator 45 uses the signal to determine the amount of movement of the plunger tip 13 by a third setter 46.
If the amount of movement only in the galling state exceeds a predetermined set value, the alarm system 48 is activated. It goes without saying that the alarm system may optionally utilize various types of alarms, such as lamps, buzzers, and character displays.

The detailed operation of the above embodiment is as follows. Amplifier pressure signal according to cylinder operating pressure P
In FIG. 3a, where V _P is the vertical axis and the elapsed time of movement of the plunger tip 13 is the horizontal axis, the height of the predetermined operating pressure of the operating cylinder 15 during normal operation is P _{S , and the signal voltage at that time is P S} . Shown as VP ₁ . Then, when the injection plunger 11 is operated, a surge pressure is generated at the time of startup.
P ₁ occurs instantaneously and the signal value corresponding to the predetermined pressure P _S
Occurs beyond VP ₁ . Next, the pressure stabilizes at a predetermined pressure P _S , but due to minute galling or vibration of the machine that does not adversely affect the product, a different peak pressure P ₂ Furthermore, the plunger tip 1
Various pressure fluctuations may occur, such as a gentle peak pressure P ₃ due to an increase in friction between the injection sleeve 12 and the inner surface of the injection sleeve 12, and a peak pressure P ₄ due to large galling that affects the product. Therefore, the predetermined pressure
Voltage input to the first comparator 25 according to PS
If the first setter 27 generates a voltage VP ₂ corresponding to the set pressure PK higher than VP ₁ and uses this as a reference signal to the first comparator 25, the first comparator 25 receives the input from the amplifier 22. emits a first output signal when the pressure signal voltage is higher than the reference signal voltage _VP2 . Therefore, if the hydraulic pressure in the operating cylinder 15 exceeds the high pressure PK set for alarm, i.e.
From ts ₁ to tE ₁ and from tB ₂ to tE ₂ in Figure 3a,
The first output signal is generated from the first comparator 25 in the period from tB ₃ to tE ₃ .

Further, when the hydraulic pressure signal VP is differentiated by the differentiating circuit 23, it appears as ΔPV on the vertical axis shown in FIG. 3b, and a signal voltage corresponding to the rate of change of the pressure signal is generated. Therefore, if the predetermined voltage △VP ₁ is set using the second setting device 28, when the fluid pressure changes rapidly,
The second comparator 26 will provide a second output signal at t'S ₁ , t'S ₂ , t'S ₃ , and t'S ₄ .

Therefore, the first AND circuit 31 to which the first output signal and the second output signal are input is connected to the operation cylinder 1.
When the signal △VP corresponding to the rate of change in the _hydraulic pressure _to A latch signal is output and the data of the first latch counter 36 is latched.

As mentioned above, when the output signal of the amplifier circuit is VP ₂ or higher, that is, the hydraulic pressure is higher than the predetermined value PK, and the rate of increase is rapid, the first AND circuit 31 issues a latch signal, and the injection plunger 11 outputs a latch signal. The first latch counter 36, which also receives the position signal, latches the position data, that is, the abnormal pressure generation position, and sends the position data to the arithmetic circuit 41.

On the other hand, the monostable multivibrator 33 is activated by the trigger signal from the first AND circuit 31, and the second AND circuit 32 which receives the output pulse signal of the monostable multivibrator 33 receives the pulse signal as input and performs the first comparison. The first output signal of the device 25 is taken in as a negative input. Therefore, the second AND circuit 32 outputs tE 1 and tE ₄ when the pulse signal is input and the first output signal disappears, that is, when the hydraulic pressure of the operating cylinder 15 falls from abnormally high pressure to _below PK. The second latch counter 3 produces an output.
Sends a latch signal to 7.

When the second latch counter 37 receives the latch signal from the second AND circuit 32 as described above, it latches the plunger position data from the position detection pulse generator 35 to the second latch counter 37, and sends the data to the arithmetic circuit 41. send. The arithmetic circuit 41 receives a plunger position signal from the first latch counter 36 when the hydraulic pressure in the operation cylinder 15 suddenly changes above a predetermined value and reaches a pressure above a predetermined high pressure PK. The plunger position signal when the pressure drops below the high pressure PK of PK is received from the second latch counter.

Therefore, if the calculation circuit 41 calculates the position data from the first latch counter and the position data from the second latch counter, the hydraulic pressure of the operating cylinder 15 can be made equal to or higher than the differential value of the hydraulic pressure, and the hydraulic pressure is continuous. Then, the injection stroke that becomes a predetermined value is calculated. The third comparator 45 detects whether or not the calculated stroke is less than a predetermined value, and if the stroke is greater than or equal to the predetermined value, an alarm is issued by activating the alarm system 48 or the operating cylinder 15
operation can be stopped.

Incidentally, the fact that the consecutive strokes of the abnormally high pressure exceed a predetermined value is the same as that the continuous time of the abnormally high pressure exceeds the predetermined value. Therefore, as shown in FIG. The output signal from the second AND circuit 32 and the output signal from the second AND circuit 32 are directly guided to the timer measurement circuit 42, and the time difference between the output signal and the first AND circuit 32 is measured. After receiving the signal from the AND circuit 31, if the signal from the second AND circuit 32 is not received within a predetermined time, the alarm system 48 is activated.

In addition, the above measurement is performed when the hydraulic pressure and the hydraulic pressure differential value exceed a predetermined value.
A stroke or time exceeding PK was measured, but
Simply measure the duration of the output signal of the first AND circuit 31, and when the hydraulic pressure and the hydraulic pressure differential value exceed a predetermined value, the time period during which the hydraulic pressure differential value continuously exceeds the predetermined value △VP ₁ is determined. It may also be measured.

This measurement is a method for detecting a case in which a rapid pressure increase continues for a longer time after the hydraulic pressure exceeds a predetermined value PK, and it can be detected that the cylinder 15 of the injection plunger is at dangerously high pressure due to galling.

As described above, when the hydraulic pressure or the differential value of the hydraulic pressure exceeds a predetermined value, the method according to the present invention is applied to This is a method of measuring travel time, and since it is activated when the differential value is greater than a predetermined value, it does not have a negative effect on the die-cast product.It does not have a negative effect on the die-cast product.The gradual change in hydraulic pressure in the operating cylinder 15 (P3 in Figure _3a ) prevents unnecessary operation. without causing
In addition, since the measurement is performed when the liquid pressure continuously exceeds a specified level, even if the liquid pressure becomes abnormally high, the change will occur in an extremely short period of time without adversely affecting the die-cast product (P ₁ in Figure 3 a). ), and determines the degree of galling by detecting a sudden pressure change and abnormally high pressure exceeding a predetermined level, or by detecting dangerous abnormally high pressure.

Therefore, it is possible to accurately detect galling that has a negative effect on die-cast products, and prevent the occurrence of unstable injection speed and pressure during injection, waving of the molten metal in the injection sleeve, entrainment of gas, and a drop in molten metal temperature. By taking measures to ensure that hot water flows well into the cavity, it is possible to prevent the formation of cavities in the product, and to manufacture high-quality die-cast products.

Note that the method of determining the galling degree according to the method of the present invention is applicable when measuring the galling caused by the plunger 13 when moving forward or retreating without injecting molten metal into the sleeve 12, or when measuring and determining the galling during actual injection of molten metal. This is a determination method that can be carried out when carrying out a test.Measurement under no load can accurately measure the condition of the plunger tip and the inside of the sleeve without being affected by the flow of hot water into the cavity due to the shape and size of the cavity 18. On the other hand, measurement of actual firing allows accurate knowledge of the movement of the plunger tip during actual operation.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a die-casting machine, Fig. 2 is an example of a circuit implementing the present invention, Fig. 3 is a diagram showing changes in hydraulic pressure of the operating cylinder, etc., and Fig. 4 is an example of another implementation circuit. It is. 10=die casting machine, 11=injection plunger, 12=sleeve, 13=plunger tip,
15=operating cylinder, 18=cavity, 21=
Pickup element, 22 = amplifier, 23 = differentiator, 25, 26 = comparator, 27, 28 = setter,
31, 32 = AND element, 33 = Multivibrator, 35 = Position pulse generator, 36, 37 = Latch counter, 41 = Arithmetic circuit, 42 = Timer measurement circuit, 45 = Comparator, 46 = Setter, 48 =
alarm system.

Claims (1)

[Claims] 1. Measure the hydraulic pressure of the operation cylinder and the differential value of the hydraulic pressure when the injection plunger mechanism moves, and when both the hydraulic pressure and the hydraulic pressure differential value exceed a predetermined value, the hydraulic pressure is The injection stroke or the movement time of the injection plunger is measured when the hydraulic pressure differential value continuously appears above a predetermined value or when the hydraulic pressure differential value continuously appears above a predetermined value, and the risk of galling of the injection plunger mechanism is determined. A method for determining the degree of galling in a die-casting machine injection plunger mechanism.