JP2977246B2 - Injection control method for die casting machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an injection control method for a die-casting machine, and more particularly to a linkage control of a single-acting cylinder and a pressure-intensifying cylinder.

(Background technology)

Conventionally, it has been known that the quality of a die-cast molded product is greatly affected by an injection speed and an injection pressure when a molten metal is filled in a mold. In particular, it is necessary to perform sufficient pressurization within the time until the molten metal solidifies, and a die casting machine having a two-stage drive cylinder is used.

As shown in FIG. 6, the die casting machine 90 supplies the molten metal 92 to be filled in the mold cavity 91 into the injection sleeve 93 and injects the molten metal with the plunger 94. Oil is increased in pressure by a large-diameter intensifying cylinder 96 and a single-acting cylinder 95 is
The pressure of the molten metal 92 filled in is increased.

FIG. 7B shows the transition of the injection speed in the die casting machine 90. In the figure, forward single-acting cylinder 95 is initially advanced at a low speed, then filled in once high speed from the time t _1, it is braked by receiving a filling pressure of the molten metal 92 along with the complete filling, increasing at the time point t ₂ pressure cylinder 96 is boosted operating, stopping at single acting cylinder 95 the time t ₃ and further forward.
This position is the stroke end position Dse of the single-acting cylinder 95.
And

FIG. 7A shows the transition of the injection pressure in the die casting machine 90. In the figure, the time point t ₂ when the filling is completed
Then, the pressure-intensifying cylinder 96 starts to advance, and the pressure is increased according to the pressure increasing curve L1.

Each cylinder 95, 9 in the aforementioned die casting machine 90
A sequence valve system as shown in FIG. 8 and a limit switch system as shown in FIG.

In FIG. 8, the single-acting cylinder 95 has a check valve.
A single-acting-side hydraulic circuit 114 is connected to the accumulator 113 via the speed control valve 112 and the speed control valve 112. On the other hand, the pressure-intensifying cylinder 96 is connected to a pressure-increasing hydraulic circuit 117 that reaches the accumulator 113 via a pilot-operated pressure-intensifying valve 116 that is opened and closed by a sequence valve 115. The sequence valve 115 is set to open the pressure-intensifying valve 116 when the pressure of the single-acting-side hydraulic circuit 114 exceeds a preset pressure-increasing start pressure. Accordingly, the operation of the speed adjusting valve 112 starts the forward movement of the single-acting cylinder 95 to perform injection, and the increase in the filling pressure accompanying the completion of filling causes the sequence valve 115 to operate at the pressure increasing start pressure to open the pressure increasing valve 116. Then, the pressure-intensifying cylinder 96 starts moving forward to increase the pressure.

In FIG. 9, a single-acting cylinder 95 is
A single-acting-side accumulator 123 is connected via a check valve 121 and a switching valve 122 that also serves as a speed adjustment. On the other hand, the solenoid valve 12
A pressure-increasing accumulator 126 is connected via a pressure-increasing switching valve 125 that is opened and closed in step 4. A limit switch 127 is connected to the electromagnetic valve 124, and the limit switch 127 is a rod extending from the single-acting cylinder 95 just before the filling is completed.
It is set at the position where it operates by contacting 128 Docs 129. Therefore, the operation of the switching valve 122 causes the single-acting cylinder 95
Is started, injection is performed, and the limit switch 127 is switched just before the filling is completed.
Is started to increase the pressure.

[Problems to be solved by the invention]

Incidentally, in the above-described die casting machine 90, in order to obtain an appropriate boosting curve L1 in the boosting of FIG. 7A, the linkage control of the cylinders 95 and 96, in particular, the forward start timing of the boosting cylinder 96 Must be set correctly.

For example, if the start of advance of the pressure-intensifying cylinder 96 is early, the pressure-intensifying cylinder 96 starts to advance before the filling is completed, and a desired pressure-increasing effect can be obtained as shown in a pressure-up curve L2 in FIG. 7 (A). Absent. When the forward movement of the pressure-intensifying cylinder 96 is delayed, the pressure-increasing starts after the forward movement of the single-acting cylinder 95 is stopped, as shown by the pressure-up curve L3 in FIG. Cooling proceeds, and the desired effect of increasing the pressure cannot be obtained.

However, in the conventional linkage control described above, the booster cylinder
It is difficult to always properly switch the start timing of 96 forwards.

That is, in the sequence valve system as shown in FIG. 8, if the pressure increase start pressure of the sequence valve 115 is set low, the pressure peak accompanying the switching of the injection speed from low speed to high speed and the resistance between the injection sleeve and the plunger are reduced. Sequence valve 115 even when the filling pressure increases
Is activated, and the pressure-intensifying cylinder 96 is likely to erroneously start before filling is completed. If the set pressure is high, the pressure increasing cylinder 96 starts moving due to a rise in the filling pressure after the filling is completed, and a time lag occurs. Further, since the filling pressure accompanying the completion of the filling varies depending on the mold to be used, it is necessary to adjust the set pressure of the sequence valve 115 each time.

On the other hand, in the limit switch system as shown in FIG. 9, since the stop position of the plunger differs depending on the die used, it is necessary to adjust the set position of the limit switch 127 each time. Even if the same mold is used, if the supply amount of the molten metal 92 to the injection sleeve 93 in FIG. 6 is different, the molten metal 92 remaining in the injection sleeve 93 after the filling is completed.
(So-called biscuits) have different thicknesses. Therefore, the position detected by the limit switch 127 is not limited to immediately before the filling completion position, and the pressure increase start position cannot always be made appropriate. Further, when the opening degree of the pressure-intensifying valve 125 is increased, the movement of the pressure-intensifying cylinder 96 is increased, and the forward stroke of the pressure-intensifying cylinder 96 becomes larger than a predetermined stroke or reaches the stroke end position Dse. There is a problem that can not be.

SUMMARY OF THE INVENTION An object of the present invention is to provide an injection control method for a die casting machine capable of always performing an appropriate pressure increasing operation.

[Means for solving the problem]

The present invention detects the stroke end position Dse of the single-acting cylinder in the previous injection cycle, sets the pressure increase start signal transmission position before the position by a preset reference pressure increase stroke Sa, and In this injection cycle, when the single-acting cylinder that is moving forward reaches the pressure increase start signal transmission position, a pressure increase start signal for instructing the pressure increase cylinder to advance is transmitted.

Further, if necessary, the actual stroke of the pressure increasing cylinder is detected, and the pressure increasing start signal transmission position is adjusted so that the stroke becomes constant.

The reference pressure-increasing stroke Sa may be set as appropriate according to the die used, the pressure-intensifying cylinder, and the required pressure-increasing capacity, and may be input and stored in a storage means of a control system.

In setting the pressure increase start signal transmission position, an average value of a predetermined number of times of sampling or the like may be adopted in order to avoid an inadvertent effect due to, for example, a one-time variation in each injection cycle.

(Operation)

In the present invention, by increasing the pressure-intensifying cylinder by the pressure-intensifying start signal transmitted at the pressure-intensifying start signal transmitting position set for each injection cycle,
Even if the supply amount of the molten metal changes gradually and the stroke end position Dse of the single-acting cylinder changes, the pressure increase start signal transmission position in the next cycle is automatically corrected based on the change. become.

In addition, by performing the adjustment based on the actual stroke of the pressure-intensifying cylinder to the pressure-intensification start signal transmission position based on the stroke end position Dse of the single-acting cylinder set earlier, the single-acting cylinder based on the leakage of the hydraulic oil and the like is adjusted. It is also possible to compensate for the difference in the amount of movement from the pressure-intensifying cylinder, and the like, and a stable pressure-increasing operation is always performed.

Therefore, in the present invention, it is possible to automatically take appropriate measures against changes in the molten metal supply amount and the mold, and to deal with various fluctuations as in the conventional sequence valve system and limit switch system. The accompanying malfunctions, complicated adjustments, and the like are eliminated, and the above object is achieved.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, the die casting machine of the present embodiment is a die casting machine having a single-acting cylinder 10 and a pressure-intensifying cylinder 20. The single-acting cylinder 10 is connected to a single-acting-side hydraulic circuit 14 that reaches the accumulator 13 via a check valve 11 and a speed adjusting valve 12. The booster cylinder 20
A pressure-increasing hydraulic circuit 24 that connects to the accumulator 13 via a pilot-operated pressure-intensifying valve 22 that is opened and closed by an electromagnetic valve 21 is connected. The solenoid valve 21 is connected to control means 30 for controlling the start of the pressure-intensifying cylinder 20.
The single-acting-side encoder 15 for detecting the moving amount of the pressure-increasing cylinder 10 and the pressure-increasing-side encoder 25 for detecting the moving amount of the pressure-increasing cylinder are connected.

As shown in FIG. 2, the single-acting cylinder 10 is
Has a piston 17 in each of the ports 16A, 16B
It is moved forward and backward by the hydraulic oil introduced and discharged from. Rod 18 extending to an injection plunger (not shown)
An annular or spiral groove 19 is formed on the outer peripheral surface of the rod 18, and non-magnetic plating is applied. The single-acting-side encoder 15 is, for example, an electromagnetic pickup installed at an end of the single-acting cylinder 10, and the tip thereof is disposed to be close to the rod 18. Accordingly, a pulse corresponding to the unevenness of the groove 19 passing through the tip is output from the single-acting-side encoder 15, and the current position Ds of the single-acting cylinder 10 can be detected.

The pressure-intensifying cylinder 20 has a piston 27 in a sleeve 26, and the piston 27 is moved forward and backward by hydraulic oil introduced and discharged from each of the ports 26A and 26B. The piston 27 has a larger diameter than the piston 17 on the single acting side, and can generate a larger driving force than the piston on the single acting side even when receiving the same oil pressure. The piston 27 is inserted on the right end side of the sleeve 16 in the drawing with the single acting side having a small diameter, and increases the operating oil in the sleeve 16 to drive the piston 17 on the end moving side from behind. A rod 28 is connected to the piston 27, and an annular or spiral groove 29 is formed on the peripheral surface of the rod 28, and non-magnetic plating is applied. The pressure-increasing encoder 25 is an electromagnetic pickup or the like provided at an end of the pressure-intensifying cylinder 20, and the tip thereof is disposed close to and facing the rod 28. Therefore, a pulse corresponding to the unevenness of the groove 29 passing through the front end is output from the pressure-increasing encoder 25, and the current position Da of the pressure-intensifying cylinder 20 can be detected.

In FIG. 4, a control means 30 is composed of various signal processing circuits, and includes a single-acting side drive control section 31, a pressure-increasing side drive control section.
32, stroke end detection unit 33, pressure increase stroke setting unit
34, a sampling frequency setting section 35, a previous pressure increase start signal transmission position storage section 36, a pressure increase start signal transmission position setting section 37, and a pressure increase start signal transmission position detection section 38.

The single-acting drive control unit 31 operates the single-acting hydraulic circuit 14 based on a predetermined command to control the forward / backward movement of the single-acting cylinder 10. For control, use the single-acting encoder 15
Is referred to as feedback.
Dse is the stroke end position.

The pressure-increase-side drive control section 32 operates the pressure-increase-side hydraulic circuit 24 based on a predetermined command, and controls the forward / backward movement of the pressure-increase cylinder 20. For control, the pressure booster encoder 25
The current position Da from is referred to as feedback.

The stroke end detection unit 33 detects the stroke end of the single-acting cylinder 10 and outputs a stroke end signal E. For example, the change amount becomes zero with reference to the current position Ds from the single-acting encoder 15. It is determined to be stopped at the point of time.

The pressure-increasing stroke setting section 34 is means for storing a reference pressure-increasing stroke Sa externally set by the operator.

The sampling number setting unit 35 is means for storing the sampling number N externally set by the operator.

The previous pressure increase start signal transmission position storage unit 36 calculates an average value DseM of N actual measured values of the past N stroke end positions Dse calculated by the pressure increase start signal transmission position setting unit 37, and obtains Dx ₀
= DseM-Sa to determine the pressure increase start signal transmission position Dx described later.
Corrected to Dx ₀ and memorized.

The pressure increase start signal transmission position setting unit 37 sets the current position Ds, Da at the time of receiving the stroke end signal E as the stroke end position Dse, Dae, performs a calculation according to the state from each value, and performs a pressure increase start signal. The transmission position Dx is set.
Specifically, as shown in FIG. 3, when the previous position Dx, etc., such as immediately after starting, has not been set yet, the single-acting stroke end position set value DsE is obtained from the biscuit thickness Sb, and this DsE A value Dx obtained by subtracting the reference pressure increase stroke Sa from the above is stored as the previous pressure increase start signal transmission position Dx ₀ in the previous pressure increase start signal transmission position storage unit 36 according to the flowchart of FIG. measure. Then, a Dx ₀ by calculating the Dse-Sa from the next injection cycle, the previous pressure increase start signal transmitting position storage section 3
Remember in 6. If the number of samplings N = n, the stroke end positions Dse ₁ , D of each injection cycle for n times
the average value DseM of se ₂ ... Dse _n, and stores the previous pressure increase start signal transmitting position storage unit 36 as a previous pressure increase start signal transmitting position Dx ₀ seeking DseM-Sa.

The pressure increase start signal transmission position detector 38 is a single-acting
The current position Ds from 15 is monitored, and when the single-acting-side current position Ds reaches the pressure increase start signal transmission position Dx, a command is issued to the pressure increase side drive control unit 32 to start.

The present embodiment will be described in more detail.
The injection control is performed according to the procedure shown in the figure.

First, at the start of the injection cycle, as shown in FIG. 3, a stroke end position set value DsE obtained from the biscuit thickness Sb, a reference pressure increase stroke Sa, a sampling number N, and DaE, β, and α described later are input. And Dx
= DsE-Sa is obtained and stored (process 40).

Next, the cylinders 10 and 20 on the single acting side and the pressure increasing side are moved to the retreat limit by the respective drive control units 31 and 32, and the encoders 15 and 25 are moved.
The respective current positions Ds and Da are set to 0 (processing 4
1). In this state, the molten metal is injected into the injection sleeve 93 (Step 42).

Subsequently, the single-acting drive control section 31 starts the forward movement of the single-acting cylinder 10 (step 43). When the stroke of the single-acting cylinder 10 during forward movement reaches the pressure increasing start signal transmitting position Dx, the pressure increasing start signal is transmitted. A pressure increase start signal is transmitted by the detection unit 38 (process 44). Thus, the pressure-intensifying cylinder 20 is moved forward to increase the pressure (step 45).

When the pressure increase is completed, the stroke end position Dse of the single-acting cylinder 10 is actually measured and stored (step 46).

Here, if the number of samplings N is 1, (processing 4
7) determine the pressure increase start position Dx = Dse-Sa by pressure increase start signal transmitting position setting unit 37, and stores to modify the Dx to Dx ₀ (process 48).

If the number of samplings N is n (process 49),
Average value D of _n stroke end positions Dse ₁ , Dse ₂ … Dse _n
seeking SEM (process 50), determine the Dx ₀ = DseM-Sa, the Dx Dx ₀
(Step 51).

Although not shown, an allowable value ± γ is given to DseM, and DsM
upper limit eM + gamma, may be corrected to Dx ₀ when the stroke end position setting value DsE the DseM-γ as the lower limit value exceeds the upper limit value.

After these processes, the process returns to the process 41 and enters the next injection cycle.

On the other hand, another feature of the present invention,
The case where the stroke end position Dae is controlled to be constant will be described.

As described above, at the start of the injection cycle, DaE, β, and α are input along with the stroke end position set value DsE, the reference voltage stroke Sa, and the number of samplings N. Among them, DaE is a stroke end position set value of the pressure-intensifying cylinder 20, and an allowable value of ± β is given to DaE. α is set to empirically 5~10mm a modified value of the pressure increase start signal transmitting position Dx _0.

Here, if the number of samplings N is 1, (processing 4
7) Compare the pressure increase stroke end position Dae with the pressure increase stroke end position set value DaE ± β (processing 52), and find that Dae> DaE
+ Beta that is, if it exceeds the upper limit value delayed by the pressure increase start signal transmitting position Dx ₀ as Dx ₀ + α α (process 53). On the other hand, when Dae <DaE-β, that is, when the value exceeds the lower limit, Dx ₀ −
advancing only alpha-increasing pressure start signal transmitting position Dx ₀ as alpha (process 54).

If the number of samplings N is n (process 49),
pressure increasing stroke end position Dae ₁ n times, Dae ₂ ... an average value DAEM of Dae _n (process 55), compares the DAEM the pressure increase stroke end position setting value DAE ± beta (process 56), DAEM> D
aE + beta that is, if it exceeds the upper limit value delayed by the pressure increase start signal transmitting position Dx ₀ as Dx ₀ + α α (process 57).
On the other hand, when DaeM <DaE-β, that is, when the value exceeds the lower limit, Dx ₀
Advancing only α a pressure increase start signal transmitting position Dx ₀ as-.alpha. (process 58).

According to this embodiment, the following effects can be obtained.

In other words, the single-acting cylinder 10 is
The start timing of the booster cylinder 20 is always set by starting the booster cylinder 20 when the pressure has reached, and changing the setting of the booster start signal transmission position Dx for each injection cycle according to the previous operation result. It can be adjusted to an optimal state.

Therefore, a single-acting cylinder
Even if the 10 stroke end position Dse changes, it can be automatically responded to by changing the setting of the pressure increase start signal transmission position Dx in each cycle, so that the appropriate pressure increase is always performed without the operator changing the setting. Actions can be taken.

Therefore, it is possible to solve problems such as malfunctions and complicated adjustments caused by various fluctuations in the conventional sequence valve system and limit switch system in the die casting machine.

In setting the pressure increase start signal transmission position Dx for each cycle, the actual stroke of the pressure increase cylinder 20 is referred to.
It is possible to reliably cope with the 20 movement amount differences and the like.

For this reason, the amount of movement of the pressure-intensifying cylinder 20 can always be a constant amount corresponding to the reference pressure-increasing stroke Sa, and the pressure at the time of pressure-increasing can be made uniform to perform a more stable pressure-increasing operation.

Furthermore, by performing averaging for the number of times of sampling N for the pressure increase start position Dx, it is possible to appropriately avoid inconveniences such as the setting being excessively sensitive to one-off fluctuations and the like. Can be arbitrarily adjusted by setting the number of samplings N.

Note that the present invention is not limited to the above-described embodiment, and for example, the types of the encoders 15 and 25 for detecting the movement amounts on the single acting side and the pressure increasing side are arbitrary. The types of the single-acting cylinder 10 and the pressure-intensifying cylinder 20 are also arbitrary, and the present invention can be applied to injection control of various die casting machines.

〔The invention's effect〕

As described above, according to the present invention, by controlling the pressure increase operation based on the preset reference pressure increase stroke and the pressure increase start signal transmission position obtained from the stroke end position in the previous injection cycle, various pressure increase operations are performed. Automatic correction can be performed for fluctuations and the like, and an appropriate pressure increasing operation can always be performed.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, FIG. 2 is a cross-sectional view showing a main part of the embodiment, FIG. 3 is a cross-sectional view showing a main part of an injection cylinder, and FIG. FIG. 5 is a flow chart showing a processing procedure of the embodiment, FIG. 6 is a sectional view showing a basic configuration of a conventional die casting machine, and FIG. 7 is a conventional die casting machine. FIGS. 8 and 9 are hydraulic circuit diagrams showing a driving method in a conventional die casting machine, respectively. 10 …… Single acting cylinder, 15 …… Single acting encoder, 20 ……
Pressure booster cylinder, 25 Pressure booster encoder, 30 Control means, 33 Stroke end detection unit, 34 Pressure boost stroke setting unit, 37 Pressure boost start signal transmission position setting unit, 38
... Pressure increase start signal transmission position detector.

Claims (2)

(57) [Claims] An injection control method for a die-casting machine in which a single-acting cylinder is advanced to perform filling when a molten metal is injected, and then a pressure-intensifying cylinder is advanced to increase pressure. Detects the stroke end position after the pressure is completed, sets the pressure increase start signal transmission position before the position by the reference pressure increase stroke set in advance, and advances the single-acting cylinder to advance the molten metal in the next injection cycle. An injection control method for a die casting machine, characterized in that when the stroke of a single-acting cylinder that is being charged and moving forward reaches a pressure-increasing start signal transmission position, a pressure-increasing start signal for instructing the pressure-intensifying cylinder to advance is transmitted. 2. The injection control of a die-casting machine according to claim 1, wherein an actual stroke of the pressure-intensifying cylinder is detected and a pressure-intensifying start signal transmission position is adjusted so that the stroke is constant. Method.