JP7559628B2 - Extrusion press device and extrusion pressure control method - Google Patents

Description

The present invention relates to an extrusion press device equipped with a main pump unit that selectively drives multiple hydraulic pumps connected in parallel to discharge the required amount of hydraulic oil, and a method for controlling the extrusion pressure.

An extrusion press is a device that manufactures aluminum products by pressing an easily processed metal material, such as aluminum or its alloy (hereafter referred to as aluminum material), against a die and continuously extruding (extrusion molding) aluminum products of a specified cross-sectional shape from the die. The die has an opening that mimics the cross-sectional shape of the aluminum product, and the extruded long aluminum product is cut to a specified length to become individual aluminum products.

The process in which this extrusion molding is carried out is called the extrusion process to distinguish it from other processes. In this extrusion process, the pressure that presses the aluminum material against the die is called the extrusion pressure, and this extrusion pressure is controlled by a hydraulic circuit. In addition, the speed at which the aluminum material is pressed against the die, i.e., the speed at which the extrusion stem, described below, advances, is called the extrusion speed (ram speed), and this extrusion speed is controlled by increasing or decreasing the discharge rate of the main pump unit that supplies hydraulic oil to the hydraulic circuit.

A conventional extrusion press device and its extrusion pressure control method will be described with reference to Figures 1 to 3. Figure 1 shows an outline of the configuration of an extrusion press device, with detailed configuration illustrations omitted. The aluminum material to be extruded is formed into a cylindrical billet B of a predetermined diameter that corresponds to the aluminum product W to be manufactured, and is inserted into a billet storage section in a container 1.

At one end of the container 1, a die 2 is placed, which has an opening that mimics the cross-sectional shape of the aluminum product W, and from the other end, an extrusion stem 3 is inserted that presses the billet B. Normally, a dummy block is attached to the tip of the extrusion stem 3, and in this application, this dummy block is also referred to as the extrusion stem 3.

The main cylinder 4, which generates the extrusion pressure, constitutes a hydraulic cylinder having only an oil chamber for advancing the cylinder rod, and the main ram 4a corresponds to the cylinder rod. The extrusion stem 3 is attached to this main ram 4a. When the position of the main ram 4a (ram position) moves toward the die 2 (forward/right side in Figure 1) due to hydraulic oil supplied from the main pump unit 5 to the oil chamber of the main cylinder 4 via a hydraulic circuit, the extrusion stem 3 also moves (forward), pressing the billet B against the die 2. Due to this pressing, the billet B is pressurized in the container 1, and is continuously extruded from the opening of the die 2, which imitates the cross-sectional shape of the aluminum product W. In Figure 1, the main pump unit 5 is illustrated as a hydraulic pump to simplify the drawing.

In the extrusion press shown in FIG. 1, for example, a billet B is extruded at a ram speed as shown in FIG. 2 to form an aluminum product W. FIG. 2 is a graph showing an example of ram speed control relative to ram position. The ram speed is the forward speed of the main ram 4a (extrusion stem 3) that is controlled so that the extrusion speed described above becomes a suitable speed (set extrusion speed) for extruding a good product. In FIG. 2, the horizontal axis shows the ram position L, and the vertical axis shows the ram speed V. In actual control, it takes a certain amount of time to accelerate the ram speed from zero to a predetermined speed, or to accelerate or decelerate a predetermined ram speed to a different ram speed. In FIG. 2, when the main ram 4a (extrusion stem 3) is moving, the change in the ram position corresponds to that time, but for ease of understanding, the time required for acceleration and deceleration (change in ram position) is omitted.

The section from ram position L1 to ram position L2 indicates upset. Upset is the section in which, at ram position L1, the extrusion stem 3 is pressed against the billet B and the billet B is pressed at ram speed V1. This pressing causes the billet B to be crushed and plastically deformed in the diametric direction, filling the gap between the billet B and the billet storage section in the container 1 with the billet B, completing preparations for extrusion molding.

This upset ends when the actual extrusion pressure generated in the main cylinder 4 reaches the set pressure. Note that the upset does not cause the aluminum product W to be extruded from the die 2. This set pressure is generally 8 to 10 MPa.

After the upset is completed, the forward movement of the extrusion stem 3 is stopped at the ram position L2. Then, the container 1 and the extrusion stem 3 are moved slightly backward (to the left in FIG. 1), thereby discharging the air that was trapped in the billet storage area in the container 1 by the upset from the gap between the die 2 and the container 1. This process of discharging the gas from the billet storage area in the container 1 is called a burp cycle.

Next, the container 1 is advanced and pressed against the die 2 (container seal), and the extrusion stem 3 is advanced and returned to the ram position L2. This ends the burp cycle. Note that the movement of the extrusion stem 3 in this burp cycle is not shown in FIG. 2. After that, in the section from the ram position L2 to the ram position L3, the extrusion stem 3 presses the billet B at the ram speed V2. The ram position L2 is the extrusion start point. In this section, the tip portion of the billet B pressed against the end face of the die 2 at the beginning of the extrusion process is extruded into the opening of the die 2 that imitates the cross-sectional shape of the aluminum product W, and the billet B is pressed until a flow of aluminum material (metal flow) is formed in the die 2. The ram speed V2 is set to a low speed in order to protect the die 2.

Next, in the section from ram position L3 to ram position L4, the extrusion stem 3 presses the billet B at ram speed V3. This section is where the actual extrusion molding takes place. This pressing causes the extrusion stem 3 to advance at a set extrusion speed that is in accordance with the ram speed V3, and the aluminum product W is continuously extruded from the die 2.

When the billet B in the billet storage section of the container 1 becomes short, the section where the extrusion molding of the billet B ends is entered. If ram position L5 is the end point of extrusion, the end section begins at ram position L4. Ram position L4 and ram position L5 are determined based on various conditions, such as the thickness of the billet B (called discard, etc.) that is intentionally left in the billet storage section of the container 1. Such control of the ram speed is controlled by increasing or decreasing the amount of hydraulic oil discharged from the main pump unit 5.

On the other hand, during extrusion molding, the actual extrusion pressure generated in the main cylinder 4 changes in response to the control of the ram speed as shown in Figure 3. In Figure 3, to facilitate comparison with Figure 2, the horizontal axis indicates the ram position L, and the vertical axis indicates the actual extrusion pressure P generated in the main cylinder 4. The change in the actual extrusion pressure during extrusion molding will be explained with reference to Figure 3. Note that the upset end extrusion pressure Pup in Figure 3 is the set pressure that ends the upset, as explained above. The rated extrusion pressure Pmax in Figure 3 will be described later.

First, in the section from ram position L0 to ram position L1 until the extrusion stem 3 contacts the billet B, an actual extrusion pressure is generated that corresponds to the load required to advance the main ram 4a (extrusion stem 3). When the main ram 4a reaches ram position L1, the extrusion stem 3 contacts the billet B and upsetting begins. This upsetting crushes the billet B, increasing the extrusion resistance, and the actual extrusion pressure increases accordingly. The actual extrusion pressure continues to increase until it reaches the upsetting end extrusion pressure Pup and the upsetting ends at ram position L2. Note that the movement of the extrusion stem 3 during the burp cycle (degassing) performed after the upsetting ends is not shown in FIG. 3, as in FIG. 2.

After the burp cycle is completed, extrusion molding begins at ram position L2. As explained above, in the section from ram position L2 to ram position L3, billet B is pressed at a low speed (ram speed V2) to protect die 2, and the actual extrusion pressure continues to rise.

In the section from ram position L2 to ram position L5, in addition to the force required to push billet B out of die 2, a force that resists the frictional force acting between the inner peripheral surface of the billet storage section of container 1 and the outer peripheral surface of billet B is generated as actual extrusion pressure. Also, in the vicinity of ram position L3, the ram speed V2 is increased to ram speed V3. Therefore, the actual extrusion pressure is maximum in the vicinity of ram position L3 where the total length of billet B is the longest, the ram speed is increased, and the extrusion resistance is greatest.

On the other hand, the force required to push the billet B out of the die 2 is considered to be approximately constant, excluding the effect of temperature changes in the billet B. Therefore, when the billet B shortens as the extrusion stem 3 advances, the frictional force decreases in proportion to this, and the actual extrusion pressure, which peaked near the ram position L3, also gradually decreases. Then, near the ram position L4 where the ram speed decelerates from V3 to V4, the rate of decrease in the actual extrusion pressure increases, and the extrusion is completed at the ram position L5.

In an extrusion press device, the maximum extrusion pressure that can be generated according to the specifications is determined in consideration of such changes in the actual extrusion pressure. This maximum extrusion pressure is called the rated extrusion pressure. This corresponds to the rated extrusion pressure Pmax in Figure 3. The rated extrusion pressure is determined by the set relief pressure set in the relief valve 10 provided in the hydraulic circuit on the discharge side of the hydraulic oil of the main pump unit 5, as shown in the hydraulic circuit HC in Figure 4. Figure 4 is a conceptual diagram of a hydraulic circuit in a typical extrusion press device in which the rated extrusion pressure is determined by the relief valve.

For example, the set relief pressure of the relief valve 10 is set to 25 MPa. When the pressure of the hydraulic oil in the hydraulic circuit HC (hereinafter referred to as the actual discharge pressure) exceeds this set relief pressure, the valve of the relief valve 10 to the tank 6 side is opened, the hydraulic oil is discharged to the tank 6 side, and the actual discharge pressure of the hydraulic circuit HC decreases. When the actual discharge pressure of the hydraulic circuit HC falls below the set relief pressure, the valve of the relief valve 10 to the tank 6 side is closed, the hydraulic circuit HC becomes a closed circuit again, and the actual discharge pressure of the hydraulic circuit HC rises to the set relief pressure. Even if the actual discharge pressure in the hydraulic circuit HC continues to exceed the set relief pressure, the opening and closing of the valve of the relief valve 10 to the tank 6 side causes the actual discharge pressure of the hydraulic circuit HC to fluctuate slightly, but is controlled to be approximately the set relief pressure.

The valve of the relief valve 10 to the tank 6 side employs an opening and closing mechanism using a compression spring or the like. The overall length of the compression spring or the like built in as a pressure adjustment spring is configured to be manually adjustable mechanically (with a screw or the like), and the set relief pressure of the relief valve 10 can be adjusted by adjusting the elastic force of the pressure adjustment spring. Depending on the aluminum product W, the actual extrusion pressure may be sufficiently lower than the rated extrusion pressure when the aluminum product is stably extruded from the die 2. However, as explained above, the actual extrusion pressure is maximum near the ram position L3. In addition, in recent extrusion molding, the need for weight reduction has increased, and high-strength aluminum alloys have become thinner, leading to higher extrusion pressures and slower extrusion speeds. Therefore, it is preferable that the actual extrusion pressure of the hydraulic circuit HC can reach the rated extrusion pressure or a high extrusion pressure in the vicinity of the rated extrusion pressure.

It is known that the relief valve has an override characteristic (pressure override) that corresponds to the flow rate of hydraulic oil supplied to the hydraulic circuit in which the relief valve is arranged, as shown in Figure 5. The horizontal axis of Figure 5 indicates the flow rate (%) of hydraulic oil supplied from the main pump unit 5 to the hydraulic circuit, with the maximum flow rate being 100%. The vertical axis indicates the relief pressure (actual relief pressure/MPa) at which the relief valve operates (opens) to the tank side.

In an ideal relief valve, regardless of the flow rate of hydraulic oil supplied to the hydraulic circuit, when the pressure of the hydraulic oil in the hydraulic circuit exceeds the set relief pressure of 25 MPa shown by line a in Figure 5, the relief valve opens to the tank side, and the actual discharge pressure of the hydraulic circuit is controlled with the set relief pressure as its upper limit.

However, in reality, due to the mechanical structure of the relief valve described above, the actual relief pressure at which the valve to the tank side opens differs from the set relief pressure depending on the flow rate of hydraulic oil supplied to the hydraulic circuit. Specifically, the lower the flow rate of hydraulic oil supplied to the hydraulic circuit, the lower the pressure at which the valve to the tank side opens, and the actual discharge pressure of the hydraulic circuit does not reach the set relief pressure. On the other hand, the higher the flow rate of hydraulic oil supplied to the hydraulic circuit, the higher the pressure at which the valve to the tank side opens exceeds the set relief pressure, and the actual discharge pressure of the hydraulic circuit exceeds the set relief pressure.

This characteristic of a relief valve is called pressure override. This pressure override is shown by the upward sloping line b in Figure 5. That is, depending on the flow rate of hydraulic oil supplied to the hydraulic circuit, a pressure difference of (a-b) occurs in the hydraulic oil pressure at which the relief valve opens, as shown by the diagonal lines in Figure 5. As an example, Figure 5 shows that when the flow rate of hydraulic oil supplied to the hydraulic circuit is 50%, the valve to the tank of the relief valve opens at the set relief pressure of 25 MPa.

By using such a relief valve with pressure override as the relief valve 10 of the hydraulic circuit HC shown in Figure 4, the discharge amount of hydraulic oil from the main pump unit 5 is controlled according to the ram speed as shown in Figure 2, for example.

The problem here is the control of the extrusion pressure near ram position L3 where the actual extrusion pressure is at its maximum. As explained above, it is preferable that the actual extrusion pressure of the hydraulic circuit HC can reach the rated extrusion pressure or a high extrusion pressure in the vicinity of it. In addition, the extrusion speed is becoming slower. That is, in extrusion molding, when the ram speed V3 in the section from ram position L3 to ram position L4 where the aluminum product W is actually extruded from the die 2 is set to a low speed, the flow rate of the hydraulic oil supplied to the hydraulic circuit HC, i.e., the discharge rate of the main pump unit 5, is also controlled to be lower than the maximum discharge rate specified.

As a result, in the shaded area of the pressure override shown in Figure 5 where the flow rate of hydraulic oil supplied to the hydraulic circuit HC is 50% or less, the valve to the tank 6 opens at a pressure (a-b) lower than the set relief pressure (line a), and the actual extrusion pressure of the hydraulic circuit HC near the ram position L3 does not reach the set relief pressure (line a).

The image of the actual extrusion pressure in this case is shown in Figure 6. The dashed line part in Figure 6 is the peak part of the actual extrusion pressure in Figure 3, and due to the pressure override of the relief valve 10, the actual extrusion pressure rises only to a pressure lower than the rated extrusion pressure Pmax near the ram position L3, as shown in the peak part of the actual extrusion pressure shown by the solid line in Figure 6. Therefore, there is a problem that the actual extrusion pressure of the hydraulic circuit does not reach the rated extrusion pressure in the specifications or a high extrusion pressure in the vicinity of it. In addition, since the actual extrusion pressure is lower than the rated extrusion pressure, the rise time of the ram speed is also longer than the rise time when the rated extrusion pressure is generated, which causes a problem that the cycle time of the extrusion molding is longer. In low-speed extrusion molding, the longer rise time of the ram speed has a large impact on the cycle time of the extrusion molding.

On the other hand, in order to hasten the rise of the ram speed at ram position L3, feedback control is performed near ram position L3 to temporarily increase the discharge rate of the main pump unit 5 above the flow rate of hydraulic oil required to advance the main ram 4a at ram speed V3.

In this case, depending on the increased flow rate of hydraulic oil, as shown in the shaded area of the pressure override in Figure 5 where the flow rate of hydraulic oil supplied to the hydraulic circuit HC is 50% or more, the valve to the tank side may open at a pressure (b-a) higher than the set relief pressure (line a), and the pressure of the hydraulic oil in the hydraulic circuit HC may exceed the set relief pressure (line a).

Figure 7 shows an image of the actual extrusion pressure in this case. The dashed line in Figure 7 is the peak of the actual extrusion pressure in Figure 3, and due to the pressure override of the relief valve 10, the actual extrusion pressure reaches a pressure that exceeds the rated extrusion pressure Pmax in the vicinity of ram position L3, as shown by the peak of the actual extrusion pressure in the solid line in Figure 7. If there is a large pressure difference between the reached pressure and the rated extrusion pressure Pmax, there is a problem that an overload will occur in the pressure-receiving parts of the die and extrusion press device.

In order to solve the problems caused by the pressure override of the relief valve in the extrusion process of the extrusion press, an extrusion press is disclosed that employs an electromagnetic relief valve as the relief valve that determines the rated extrusion pressure in the hydraulic circuit. There are various types of electromagnetic relief valves that can adjust the set relief pressure in real time, but the relief valve that sets the rated extrusion pressure of the extrusion press generally employs a mechanical relief valve in which the valve to the tank 6 is equipped with a compression spring or the like and a hydraulic opening and closing mechanism, and a pilot electromagnetic valve that supplies hydraulic oil for opening and closing from the hydraulic circuit in accordance with an opening and closing control signal to the hydraulic opening and closing mechanism of the valve to the tank 6 of the mechanical relief valve.

For example, in the extrusion press device of Patent Document 1, a main relief valve 36 is set to a set pressure P1 during steady extrusion (the rated extrusion pressure Pmax in this application) in the hydraulic line, and an electromagnetic relief valve 40 is set to a predetermined set pressure P0 higher than the set pressure P1 at the beginning of the extrusion process. Immediately after the start of extrusion, when the extrusion speed is low and the flow rate of hydraulic oil supplied to the hydraulic line is low, the hydraulic oil is discharged to the tank side not from the main relief valve 36 but from the electromagnetic relief valve 40 set to a predetermined set pressure P0 higher than the set pressure P1. This causes the pressure of the hydraulic oil in the hydraulic line, i.e., the actual extrusion pressure, to quickly reach a pressure close to the set pressure P1, which is lower than the predetermined set pressure P0.

Then, as the extrusion speed approaches a predetermined speed and the amount of hydraulic oil supplied to the hydraulic line increases, the predetermined set pressure P0 of the electromagnetic relief valve 40 is reduced, and finally the set pressure P1 is reached. This makes it possible to quickly reach the desired extrusion pressure and reduce the flow rate of hydraulic oil discharged from the relief valve to the tank, resulting in high energy efficiency.

Japanese Patent Application Publication No. 07-124632

A pilot solenoid valve is incorporated in the electromagnetic relief valve used in Patent Document 1. This pilot solenoid valve controls a very small flow rate (pilot oil amount) of hydraulic oil compared to the flow rate of hydraulic oil controlled by the combined mechanical relief valve. This is because the role of the pilot solenoid valve is to supply hydraulic oil for opening and closing control to the opening and closing mechanism of the valve on the tank 6 side of the mechanical relief valve. For this reason, the pilot solenoid valve incorporates control-related parts such as a solenoid coil as a solenoid valve, and a valve body (spool) that slides inside the solenoid valve body by excitation of the solenoid coil to control the opening and closing of the pipeline and the opening and closing amount, and these solenoid valve bodies and valve bodies through which a small amount of hydraulic oil flows are small and have complex shapes and structures. For this reason, there is a problem that they are prone to malfunction due to impurities (so-called contamination) contained in the hydraulic oil in the hydraulic circuit (hydraulic pipeline). If the valve to the tank side is opened at a pressure lower than the set relief pressure due to malfunction, the pressure of the hydraulic oil in the hydraulic circuit does not reach the rated discharge pressure or a high discharge pressure close to it. Conversely, if the valve to the tank opens or does not open at a pressure higher than the set relief pressure, the pressure of the hydraulic oil in the hydraulic circuit will exceed the rated discharge pressure Pmax.

The present invention was made in consideration of the above-mentioned problems, and aims to provide an extrusion press device and an extrusion pressure control method that can suppress pressure override of the relief valve without using an electromagnetic relief valve.

The object of the present invention is to provide an extrusion press apparatus including a main pump unit that selectively drives a plurality of hydraulic pumps connected in parallel to discharge a required amount of hydraulic oil,
a mechanical relief valve including a plurality of compression springs or the like and a hydraulic opening/closing mechanism disposed in a hydraulic circuit on a discharge side of the main pump unit;
A selection means for arbitrarily selecting one of the plurality of mechanical relief valves;
a control device that selects the mechanical relief valve by the selection means in accordance with a set discharge amount of the main pump unit based on a set extrusion speed in an extrusion process;
a reference discharge rate relief valve, which is set with a main set relief pressure at which an actual discharge pressure of the hydraulic circuit reaches a rated discharge pressure when the discharge rate of the main pump unit is equal to a reference discharge rate, among the plurality of mechanical relief valves;
a small discharge amount relief valve in which a high set relief pressure is set that is higher by a predetermined amount than the main set relief pressure;
This is achieved by an extrusion press apparatus comprising:

In the extrusion press device according to the present invention, the mechanical relief valve is provided with a large discharge amount relief valve in which a low set relief pressure lower than the main set relief pressure by a predetermined amount is set,
It may further include.

The above object of the present invention is to provide an extrusion pressure control method for the above-mentioned extrusion press apparatus, comprising: a relief valve characteristic storage step of selecting the reference discharge rate relief valve, gradually increasing the discharge rate of the hydraulic oil from the main pump unit, measuring the actual extrusion pressure generated, and storing a relationship between the discharge rate and the actual extrusion pressure;
A reference discharge amount range including the reference discharge amount is set, and the reference discharge amount relief valve is selected based on the relationship between the discharge amount and the actual extrusion pressure;
a discharge amount section setting step in which the small discharge amount relief valve is selected and a section with a discharge amount smaller than the reference discharge amount section is set as the small discharge amount section;
a pump selection step of calculating the set discharge amount of the main pump unit and selecting the hydraulic pump to be driven based on the set discharge amount;
a relief valve selection step of determining whether the set discharge amount is included in the standard discharge amount category or the small discharge amount category, and selecting the mechanical relief valve set in the determined category;
The above object is also achieved by a method for controlling an extrusion pressure of an extrusion press apparatus, comprising:

In addition, in the extrusion pressure control method for an extrusion press apparatus according to the present invention, in the discharge rate category setting step, the large discharge rate relief valve is selected, and a category having a discharge rate larger than the reference discharge rate category is set as the large discharge rate category,
In the relief valve selecting step, when it is determined that the set discharge amount is included in the large discharge amount category, the large discharge amount relief valve may be selected.

Furthermore, in the extrusion pressure control method for an extrusion press device according to the present invention, in the discharge rate category setting step, an allowable upper limit extrusion pressure and an allowable lower limit extrusion pressure are set for the rated extrusion pressure, and in a relationship between the discharge rate and the actual extrusion pressure, a discharge rate corresponding to an actual extrusion pressure equal to the allowable upper limit extrusion pressure is set as an upper limit of the standard discharge rate category,
A discharge amount corresponding to an actual extrusion pressure equal to the allowable lower limit extrusion pressure may be set as a lower limit of the reference discharge amount range.

Here, in the extrusion pressure control method for an extrusion press device according to the present invention, it is preferable that the method further includes an actual extrusion pressure monitoring process in which, when the measured actual extrusion pressure during the extrusion process exceeds the rated extrusion pressure, the mechanical relief valve having a lower set relief pressure than the selected mechanical relief valve is reselected regardless of the relief valve selection process.

In addition, in the method for controlling the extrusion pressure of an extrusion press device according to the present invention, the relief valve characteristic storage step is performed at a predetermined frequency, a relationship between the discharge rate and the actual extrusion pressure is newly stored, and the newly stored relationship is compared with a relationship between the discharge rate and the actual extrusion pressure immediately before the stored relationship,
It is preferable to further include a discharge amount category resetting step for performing the discharge amount category setting step based on the new relationship between the discharge amount and the actual extrusion pressure when a difference occurs in the actual extrusion pressure relative to the standard discharge amount that exceeds a preset tolerance value in the relationship between each of the discharge amounts and the actual extrusion pressure, and resetting the standard discharge amount category.

The extrusion press apparatus according to the present invention is an extrusion press apparatus including a main pump unit that selectively drives a plurality of hydraulic pumps connected in parallel to discharge a required amount of hydraulic oil,
a mechanical relief valve including a plurality of compression springs or the like and a hydraulic opening/closing mechanism disposed in a hydraulic circuit on a discharge side of the main pump unit;
A selection means for arbitrarily selecting one of the plurality of mechanical relief valves;
a control device that selects the mechanical relief valve by the selection means in accordance with a set discharge amount of the main pump unit based on a set extrusion speed in an extrusion process;
a reference discharge rate relief valve, which is set with a main set relief pressure at which an actual discharge pressure of the hydraulic circuit reaches a rated discharge pressure when the discharge rate of the main pump unit is equal to a reference discharge rate, among the plurality of mechanical relief valves;
a small discharge amount relief valve in which a high set relief pressure is set that is higher by a predetermined amount than the main set relief pressure;
Since the pressure relief valve includes the pressure relief valve, pressure override of the relief valve can be suppressed without using an electromagnetic relief valve.

In addition, in the extrusion pressure control method of the present invention for the extrusion press apparatus of the present invention, the method includes a relief valve characteristic storage step of selecting the reference discharge rate relief valve, gradually increasing the discharge rate of the hydraulic oil from the main pump unit, measuring the actual extrusion pressure generated, and storing the relationship between the discharge rate and the actual extrusion pressure;
A reference discharge amount range including the reference discharge amount is set, and the reference discharge amount relief valve is selected based on the relationship between the discharge amount and the actual extrusion pressure;
a discharge amount section setting step in which the small discharge amount relief valve is selected and a section with a discharge amount smaller than the reference discharge amount section is set as the small discharge amount section;
a pump selection step of calculating the set discharge amount of the main pump unit and selecting the hydraulic pump to be driven based on the set discharge amount;
a relief valve selection step of determining whether the set discharge amount is included in the standard discharge amount category or the small discharge amount category, and selecting the mechanical relief valve set in the determined category;
Since the pressure relief valve is provided with the pressure relief valve, pressure override of the relief valve can be suppressed without using an electromagnetic relief valve.

FIG. 1 is a diagram showing an outline of the configuration of an extrusion press device. 1 is a graph showing an example of control of ram velocity versus ram position. 1 is a graph showing the change in actual extrusion pressure with respect to ram position. FIG. 1 is a conceptual diagram of a typical hydraulic circuit of an extrusion press device in which the rated extrusion pressure is determined by a relief valve. FIG. 4 is a diagram illustrating pressure override of a relief valve. 13 is a graph showing a change in actual extrusion pressure when the flow rate of hydraulic oil is low. 13 is a graph showing a change in actual extrusion pressure when the flow rate of hydraulic oil is large. 2 is a conceptual diagram of a hydraulic circuit of the extrusion press device according to the first embodiment, in which a rated extrusion pressure is determined by a relief valve. FIG. FIG. 3 is an image diagram of a control flow of the extrusion pressure control method according to the first embodiment. FIG. 4 is a diagram showing the relationship between the discharge rate and the actual extrusion pressure stored in a relief valve characteristic storing step in the extrusion pressure control method according to the first embodiment. FIG. 11 is an image diagram of a control flow of an actual extrusion pressure monitoring step in the extrusion pressure control method according to the second embodiment of the present invention. FIG. 11 is a diagram showing the relationship between the discharge volume stored in the relief valve characteristic storing step, which is newly performed in the discharge volume classification resetting step, and the actual discharge pressure, in the discharge pressure control method according to the third embodiment of the present invention. FIG. 13 is a diagram showing resetting of the reference discharge rate range in the discharge rate range resetting step of the extrusion pressure control method according to the third embodiment of the present invention.

Below, the embodiments for carrying out the present invention will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the inventions according to the claims, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[First embodiment]
The basic configuration of the extrusion press apparatus according to the first embodiment is the same as that previously described with reference to Fig. 1, and therefore will not be described here. Meanwhile, in the extrusion press apparatus according to the first embodiment, the rated extrusion pressure Pmax of the hydraulic circuit HC2 is determined by the hydraulic circuit HC2 shown in Fig. 8. Fig. 8 is a conceptual diagram of a hydraulic circuit in which the rated extrusion pressure is determined by a relief valve in the extrusion press apparatus according to the first embodiment.

The difference between the hydraulic circuit HC shown in FIG. 4 and the hydraulic circuit HC2 shown in FIG. 8 is that the hydraulic circuit HC2 on the hydraulic oil discharge side of the main pump unit 5 has multiple (three) relief valves instead of one, and is provided with a selection means for arbitrarily selecting from the multiple (three) relief valves.

As shown in FIG. 8, the hydraulic circuit (hydraulic line) on the discharge side of the main pump unit 5 that supplies hydraulic oil to the hydraulic circuit HC2 is connected to three branched lines, and each branch line is provided with a small discharge amount relief valve 101, a standard discharge amount relief valve 102, and a large discharge amount relief valve 103 via on-off valves 101a, 102a, and 103a as a selection means for arbitrarily selecting a relief valve, which will be described later. In the extrusion process, a control device is provided that selects these multiple relief valves using the on-off valves 101a, 102a, and 103a, which are selection means, in accordance with the set discharge amount of the main pump unit 5 based on the set extrusion speed. This control device does not need to be a control device that only has the function of selecting these multiple relief valves, and it is sufficient that the control device for the extrusion press device that controls the operation of a part or the entire extrusion press device has this function, so it is not shown in FIG. 8.

Although these relief valves each have a pressure override, they are simpler in structure than solenoid relief valves incorporating pilot solenoid valves, and are highly reliable with an extremely low possibility of malfunction due to impurities (so-called contamination) contained in the hydraulic oil in the hydraulic circuit (hydraulic lines). In addition, the opening and closing valves that serve as a selection means for arbitrarily selecting these relief valves are not flow rate control valves, but valves that only open and close the hydraulic lines, so it goes without saying that, like these relief valves, they are simple in structure and highly reliable.

First, the standard discharge rate relief valve 102 will be described. A main set relief pressure MRP is set in the standard discharge rate relief valve 102. The main set relief pressure MRP is a value that is set during a test run performed by the manufacturer of the extrusion press before shipping, or during a test run performed when the extrusion press is installed in a customer's factory, etc.

Specifically, during a trial run of an extrusion press, a cold billet for trial run, a dummy die, etc. are used, and only the on-off valve 102a of the hydraulic circuit HC2 is opened, and extrusion pressure is generated in the hydraulic circuit HC2 with the standard discharge relief valve 102 selected. The dummy die does not have an opening that resembles the cross-sectional shape of an aluminum product, so the cold billet is not extruded from the dummy die. At this time, the maximum discharge amount of the hydraulic oil from the main pump unit 5 is set to 100%, and a predetermined flow rate (e.g., 30%) of hydraulic oil is discharged from the main pump unit 5 to set the main set relief pressure MRP. This flow rate is called the standard discharge amount. Then, when the discharge amount of the main pump unit 5 is the standard discharge amount, the set relief pressure (main set relief pressure MRP) of the standard discharge relief valve 102 is set so that the actual extrusion pressure of the hydraulic circuit HC2 reaches the rated extrusion pressure Pmax.

Next, the small discharge relief valve 101 will be described. The small discharge relief valve 101 is set to a high set relief pressure HRP. This small discharge relief valve 101 is intended to suppress pressure override of the relief valve when the flow rate of hydraulic oil supplied to the hydraulic circuit HC2 is low. That is, on the premise that the discharge rate of the main pump unit 5 is low and the valve to the tank side is opened at a pressure lower than the set relief pressure, a high set relief pressure HRP that is a predetermined amount higher than the main set relief pressure MRP is intentionally set in the small discharge relief valve 101. As a result, even when the discharge rate of the main pump unit 5 is low, the actual discharge pressure of the hydraulic circuit HC2 can be made to reach the rated discharge pressure or a high discharge pressure close to it by selecting the small discharge relief valve 101.

Finally, the large discharge relief valve 103 will be described. The large discharge relief valve 103 is set to a low set relief pressure LRP. This large discharge relief valve 103 is intended to suppress pressure override of the relief valve when the flow rate of hydraulic oil supplied to the hydraulic circuit HC2 is large. That is, on the premise that the discharge rate of the main pump unit 5 is large and the valve to the tank side is opened at a pressure higher than the set relief pressure, a low set relief pressure LRP that is a predetermined amount lower than the main set relief pressure MRP is intentionally set in the large discharge relief valve 103. As a result, even when the discharge rate of the main pump unit 5 is large, by selecting the large discharge relief valve 103, the actual discharge pressure of the hydraulic circuit HC2 can be controlled with the rated discharge pressure or a high discharge pressure close to it as the upper limit.

Continuing, with reference to Figures 9 and 10, the extrusion press device according to the first embodiment and the extrusion pressure control method according to the first embodiment will be described. First, with reference to Figure 9, an overview of the extrusion pressure control method according to the first embodiment will be described. Figure 9 is an image diagram of the control flow of the extrusion pressure control method according to the first embodiment.

As shown in FIG. 9, the control flow of the extrusion pressure control method according to the first embodiment includes four steps: a relief valve characteristic storage step (F101), a discharge rate category setting step (F102), a pump selection step (F103), and a relief valve selection step (F104). These four controls are not performed during the extrusion process, but before the extrusion process starts. Please note that FIG. 9 is an image diagram showing the main control flow, and is not a control flow that accurately shows the controls that are actually performed or their order.

The first relief valve characteristic storage step (F101) is a preparation step for extrusion pressure control that is performed during the trial run described above. Specifically, first, in an extrusion press device with trial run specifications in which a cold billet for trial run, a dummy die, etc. are set, only the opening/closing valve 102a of the hydraulic circuit HC2 is opened and the standard discharge relief valve 102 is selected. Then, after setting the discharge rate of the main pump unit 5 to the standard discharge rate (e.g., 30%), the main ram 4a is advanced to generate extrusion pressure in the hydraulic circuit HC2.

In this state, the set relief pressure of the standard discharge rate relief valve 102 is adjusted so that the actual discharge pressure of the hydraulic circuit HC2 reaches the rated discharge pressure Pmax. Since it is difficult to adjust the set relief pressure of the standard discharge rate relief valve 102 when actual discharge pressure is being generated, a trial-and-error approach is used in which the actual discharge pressure of the hydraulic circuit HC2 is checked, compared with the rated discharge pressure Pmax, and the set relief pressure is adjusted. In this way, the main set relief pressure MRP is set for the standard discharge rate relief valve 102.

This completes preparation for the relief valve characteristic storage step (F101). After the main set relief pressure MRP is set in the reference discharge relief valve 102, the main ram 4a is advanced again to generate a discharge pressure in the hydraulic circuit HC2. At this time, the discharge volume of the main pump unit 5 is increased from 0 (zero)% to 100%, and the actual discharge pressure corresponding to the discharge volume is measured by a pressure detection means or the like (not shown) arranged in the hydraulic circuit HC2. It is desirable to continuously increase the discharge volume and measure the increase in the actual discharge pressure linearly, but since the purpose is to grasp the pressure override of the relief valve, the discharge volume may be increased in several stages and the actual discharge pressure measured at each stage.

For example, if emphasis is placed on extrusion molding in which the discharge volume of the main pump unit 5 is low, i.e., the set extrusion speed is low, then for the sections where the discharge volume is less than the reference discharge volume, including the vicinity of the reference discharge volume, the discharge volume is increased in small increments of 5% or 10%, and the actual extrusion pressure corresponding to each discharge volume is measured. Then, for sections where the discharge volume is greater than the reference discharge volume, the discharge volume is increased in about two steps, from the maximum discharge volume of 100% to another 70%, for example, and the actual extrusion pressure corresponding to each discharge volume is measured.

The actual extrusion pressure measured in accordance with the discharge rate of the main pump unit 5 as described above is stored in the control device of the extrusion press as the relationship between the discharge rate and the actual extrusion pressure. This relationship between the discharge rate and the actual extrusion pressure is shown in Figures 10(a) and 10(b). As shown in Figures 10(a) and 10(b), at the reference discharge rate (30%), the actual extrusion pressure of the hydraulic circuit HC2 reaches the rated extrusion pressure Pmax. For this relief valve characteristic storage step (F101), it is preferable to determine in advance the form of increase in the discharge rate of the main pump unit 5 (whether to increase continuously or in stages, and if increasing in stages, what percentage of the discharge rate at each stage, etc.), so that after preparation for the relief valve characteristic storage step (F101) is completed, the discharge rate of the main pump unit 5 is increased and the corresponding actual extrusion pressure of the hydraulic circuit HC2 is measured automatically by a program.

Next, the discharge rate category setting process (F102) will be described. This discharge rate category setting process (F102) is also a preparation process for extrusion pressure control that is performed during test operation, etc. Specifically, the relief valve to be applied and the discharge rate category to which the relief valve is applied are set based on the relationship between the discharge rate and the actual extrusion pressure stored in the relief valve characteristic storage process (F101).

Specifically, first, the standard discharge rate category SDV is set so that it includes the standard discharge rate (30%). In order to set the standard discharge rate category SDV, it is necessary to take into consideration various conditions such as the relief characteristics of the applied relief valve, the set extrusion speed, the rated extrusion pressure, and the degree of difficulty of forming the aluminum material to be extruded. As an example of a method for setting the standard discharge rate category SDV, FIG. 10(a) shows a state in which the upper limit of the standard discharge rate category SDV is set to 40% of the discharge rate and the lower limit is set to 10% of the discharge rate. When it is determined in the relief valve selection process (F104) to be described later that the set discharge rate calculated in the pump selection process (F103) to be described later is included in the standard discharge rate category SDV due to the setting of this standard discharge rate category SDV, the standard discharge rate relief valve 102 is selected as the relief valve that controls the actual extrusion pressure during the extrusion process.

When the standard discharge rate category SDV is set, a category with a discharge rate lower than the standard discharge rate category SDV is set as the small discharge rate category LDV, and when the set discharge rate calculated in the pump selection process (F103) described below is determined to be included in the small discharge rate category LDV in the relief valve selection process (F104) also described below, the small discharge rate relief valve 101 is selected as the relief valve that controls the actual extrusion pressure during the extrusion process.

In addition, in the discharge rate category setting step (F102), a category with a discharge rate greater than the standard discharge rate category SDV may be set as the large discharge rate category HDV. As with the other discharge rate categories, when the set discharge rate calculated in the pump selection step (F103) described below is determined to be included in the large discharge rate category HDV in the relief valve selection step (F104) also described below, the large discharge rate relief valve 103 is selected as the relief valve that controls the actual extrusion pressure during the extrusion step.

In the discharge rate category setting process (F102), as another example of a method for setting the standard discharge rate category SDV, an allowable upper extrusion pressure Pmaxup and an allowable lower extrusion pressure Pmaxlow for the rated extrusion pressure Pmax may be set. Specifically, in the relationship between the discharge rate and the actual extrusion pressure stored in the relief valve characteristic storage process (F101), the discharge rate Q2 corresponding to the actual extrusion pressure that is the same as the allowable upper extrusion pressure Pmaxup is set as the upper limit of the standard discharge rate category SDV, and the discharge rate Q1 corresponding to the actual extrusion pressure that is the same as the allowable lower extrusion pressure Pmaxlow is set as the lower limit of the standard discharge rate category SDV. Figure 10(b) shows the state set in this way.

In trial runs, etc., the standard discharge rate category SDV is set in this manner, and if there is a problem with the selection of the relief valve in the relief valve selection process (F104) described below during the actual extrusion process, the standard discharge rate category SDV can be reset as appropriate. Needless to say, by resetting the standard discharge rate category SDV, the category with a lower discharge rate than the standard discharge rate category SDV is reset to a new small discharge rate category LDV. Similarly, by resetting the standard discharge rate category SDV, the category with a higher discharge rate than the standard discharge rate category SDV may be reset to a large discharge rate category HDV.

As explained above, the set relief pressure of the small discharge relief valve 101 is set to a high set relief pressure HRP that is a predetermined amount higher than the main set relief pressure MRP that is set in the standard discharge relief valve 102. The set relief pressure of the large discharge relief valve 103 is set to a low set relief pressure LRP that is a predetermined amount lower than the main set relief pressure MRP that is set in the standard discharge relief valve 102.

How much higher the high relief pressure HRP should be set relative to the main relief pressure MRP, or how much lower the low relief pressure LRP should be set relative to the main relief pressure MRP, must be determined in consideration of various conditions, such as the relief characteristics of the applied relief valve, the set extrusion speed, the rated extrusion pressure, and the difficulty of forming the aluminum material to be extruded.

On the other hand, a predetermined difference between the high set relief pressure HRP and the low set relief pressure LRP and the main set relief pressure MRP may be determined in advance. For example, the high set relief pressure HRP is set 1 MPa higher than the main set relief pressure MRP, and the low set relief pressure LRP is set 1 MPa lower than the main set relief pressure MRP. With these settings, extrusion molding is actually performed, and if there is a problem with these settings, they are readjusted. Based on such accumulated experience, a predetermined difference between the high set relief pressure HRP and the low set relief pressure LRP and the main set relief pressure MRP that is suitable for extrusion molding by the user of the extrusion press device may be determined.

Here is another example. In the relief valve characteristic storage step (F101), a low discharge amount and a high discharge amount are selected as a guideline for a standard discharge amount (e.g., 30%). Let us assume that the low discharge amount is 10% and the high discharge amount is 90%. Due to pressure override of the standard discharge amount relief valve 102, at the low discharge amount of 10%, the actual discharge pressure of the hydraulic circuit HC2 becomes lower than the main set relief pressure MRP. This actual discharge pressure is Plow (MRP>Plow). On the other hand, at the high discharge amount of 90%, the actual discharge pressure of the hydraulic circuit HC2 becomes higher than the main set relief pressure MRP. This actual discharge pressure is Phigh (MRP<Phigh).

Then, the difference between each actual extrusion pressure and the main set relief pressure MRP is added or subtracted from the main set relief pressure MRP and set as the high set relief pressure HRP or the low set relief pressure LRP. Specifically, the pressure obtained by adding the difference between the main set relief pressure MRP and the actual extrusion pressure Plow (MRP-Plow) to the main set relief pressure MRP is set as the high set relief pressure HRP and as the set relief pressure of the small discharge volume relief valve 101. On the other hand, the pressure obtained by subtracting the difference between the actual extrusion pressure Phigh and the main set relief pressure MRP (Phigh-MRP) from the main set relief pressure MRP is set as the low set relief pressure LRP and as the set relief pressure of the large discharge volume relief valve 103. With this method, by setting a low and high discharge amount as a guideline for the reference discharge amount in advance, the high set relief pressure HRP and low set relief pressure LRP can be calculated in the relief valve characteristic storage process (F101).

Here is another example. For the high set relief pressure HRP, a specific discharge volume (for example, around 10%) for which the actual extrusion pressure is particularly desired to be controlled is targeted within the small discharge volume category LDV for which the small discharge volume relief valve 101 is selected. Then, even for that specific discharge volume, the set relief pressure may be adjusted during trial operation so that the actual extrusion pressure can reach the rated extrusion pressure Pmax or a high extrusion pressure close to that.

On the other hand, for the low set relief pressure LRP, a specific discharge amount (for example, around 40%) for which the actual extrusion pressure is particularly desired to be controlled is targeted within the large discharge amount category HDV for which the large discharge amount relief valve 103 is selected. Then, even for that specific discharge amount, the set relief pressure may be adjusted during trial operation so that the actual extrusion pressure does not exceed the rated extrusion pressure Pmax or a high extrusion pressure nearby it. In this way, the specific discharge amount (%) for which the actual extrusion pressure is particularly desired to be controlled may be used as a guideline for determining the upper and lower limits of the standard discharge amount category, in conjunction with the adjustment of the set relief pressure of each of the small discharge amount relief valve 101 and the large discharge amount relief valve 103.

The large discharge relief valve 103 may also function as a safety device, with a function to respond to pressure override caused by a temporary increase in the discharge rate of the main pump unit 5 in feedback control performed when the ram speed rises. Specifically, in the large discharge category HDV in which the large discharge relief valve 103 is used, a set relief pressure (low set relief pressure LRP) is adjusted during trial operation so that the actual extrusion pressure does not exceed the rated extrusion pressure Pmax or a high extrusion pressure nearby it, even if the discharge rate of the main pump unit 5 is 100%.

With the low set relief pressure LRP adjusted in this way, when the large discharge relief valve 103 is selected during the extrusion process, even if the discharge volume of the main pump unit 5 increases more than expected due to a setting error or control malfunction during feedback control, the actual extrusion pressure of the hydraulic circuit HC2 is controlled so as not to exceed the rated extrusion pressure Pmax or a high extrusion pressure close to it, thereby preventing overload from occurring in the pressure-receiving parts of the die or extrusion press device.

Here, in recent extrusion molding, for the purpose of energy saving, the discharge amount is often controlled by limiting the number of hydraulic pumps driven in each process in the main pump unit 5. In the extrusion process where the set extrusion speed is low and the discharge amount of the main pump unit 5 is small, the number of hydraulic pumps driven is particularly small. Therefore, in the feedback control performed when the ram speed rises, even if there is a pressure override due to the discharge amount of the main pump unit 5 that is temporarily increased, such a limitation on the number of hydraulic pumps to be driven makes it unlikely that the actual extrusion pressure of the hydraulic circuit HC2 will greatly exceed the rated extrusion pressure Pmax. Therefore, depending on the aluminum product to be extruded by the extrusion press device, the type of aluminum material, and the extrusion molding conditions, the large discharge amount relief valve 103 with the low set relief pressure LRP may not be essential.

On the other hand, in the feedback control performed when the ram speed rises, there is a possibility that the actual extrusion pressure of the hydraulic circuit HC2 may greatly exceed the rated extrusion pressure Pmax due to pressure override, and in some configurations it may be preferable to place a large discharge relief valve 103 as a safety device. One example is the extrusion molding of aluminum material that is difficult to extrude because it has a higher hardness than normal aluminum material. In the extrusion molding of such difficult-to-extrude materials, in order to hasten the rise of the ram speed, during feedback control of the extrusion speed, the number of hydraulic pumps that can be driven in the main pump unit 5 is set to be greater than the number of hydraulic pumps required to ensure the flow rate of hydraulic oil required for a ram speed that corresponds to the set extrusion speed.

For example, even if the set discharge rate (required discharge rate) based on the set extrusion rate is 200 L/min. and the set extrusion rate can be obtained with one hydraulic pump with a maximum discharge rate of 400 L/min., in consideration of the control to increase the discharge rate of the main pump unit 5 during feedback control, the four hydraulic pumps are set to be driven at 50 L/min. each (discharge rate 12.5% per pump), for a total of 200 L/min. The discharge rate command (%) to the hydraulic pumps is not an individual discharge rate command to each hydraulic pump, but is sent as a common discharge rate command to the four hydraulic pumps that are set to be operable. Therefore, when a 100% discharge rate command is sent during feedback control, if there is one hydraulic pump to be driven, the maximum discharge rate is 400 L/min., but with four hydraulic pumps, the maximum discharge rate may be increased to 1,600 L/min. In such a configuration, it is preferable to provide a large discharge rate relief valve 103 as a safety device.

Returning to the explanation of the control flow of the extrusion pressure control method according to the first embodiment shown in FIG. 9, the relief valve characteristic storage process (F101) and the discharge rate classification setting process (F102) described above are preparatory processes for extrusion pressure control carried out during test operation, etc. Meanwhile, the pump selection process (F103) described next is a control carried out before the extrusion process, in which a set discharge rate is calculated based on a set extrusion speed input as one of the extrusion molding conditions when extruding the aluminum product W, and a hydraulic pump to be driven during the extrusion process is selected in the main pump unit 5 based on the calculated set discharge rate.

Here, the ram speed is the flow rate (volume per unit time) of hydraulic oil supplied to the main cylinder 4 divided by the cross-sectional area of the oil chamber of the main cylinder 4. This flow rate of hydraulic oil is called the set discharge amount of the main pump unit 5 based on the set extrusion speed, and this set discharge amount is calculated from the product of the set extrusion speed and the cross-sectional area of the oil chamber of the main cylinder 4 according to the relationship described above. In practice, the forward speed of the extrusion stem 3 or the main ram 4a is measured using a speed detection means (not shown) arranged so as to be detectable, and feedback control (control to increase or decrease the flow rate of hydraulic oil supplied to the main cylinder 4) is performed to match this to the set extrusion speed.

Then, based on the calculated set discharge volume, the hydraulic pump to be driven is selected (set) in the main pump unit 5. At this time, it is preferable to also take into consideration the increase in the discharge volume of the main pump unit 5 in the feedback control near the ram position L3. Also, it is preferable to change the hydraulic pump to be driven each time the extrusion process is performed or according to the preset number of cycles of the extrusion process, etc., so that the hydraulic pumps to be driven are not concentrated on a specific hydraulic pump.

After the pump selection step (F103), a relief valve selection step (F104) is performed. The relief valve selection step (F104) is also a control performed before the extrusion step, and it is determined whether the set discharge amount calculated in the pump selection step (F103) is included in the standard discharge amount category SDV or the small discharge amount category LDV set in the discharge amount category setting step (F102). Then, the relief valve set in the determined discharge amount category is selected in the extrusion step. Note that the large discharge amount relief valve 103 may be selected in the extrusion step if it is determined in the relief valve selection step (F104) that the set discharge amount is included in the large discharge amount category HDV.

As described above, in the extrusion press apparatus according to the first embodiment, the extrusion pressure control method according to the first embodiment allows a relief valve to be selected by a control device (not shown) with a set relief pressure that allows the actual extrusion pressure of the hydraulic circuit HC2 near the ram position L3 where the actual extrusion pressure is highest to reach the rated extrusion pressure Pmax or a high extrusion pressure in the vicinity thereof in accordance with the set discharge volume of the main pump unit 5 based on the set extrusion speed in the extrusion process where extrusion molding is performed, so that pressure override of the relief valve can be suppressed without using an electromagnetic relief valve. Furthermore, regardless of the set discharge volume of the main pump unit 5, the actual extrusion pressure of the hydraulic circuit HC2 near the ram position L3 where the actual extrusion pressure is highest can be made to reach the rated extrusion pressure Pmax or a high extrusion pressure in the vicinity thereof.

Furthermore, since the multiple relief valves include a large discharge relief valve 103 set to a low set relief pressure LRP, in order to hasten the rise of the ram speed, during feedback control of the extrusion speed, the number of hydraulic pumps to be driven in the main pump unit 5 is set to be greater than the number of hydraulic pumps required to ensure the flow rate of hydraulic oil required for a ram speed corresponding to the set extrusion speed. Even in extrusion molding, such as extrusion molding of difficult-to-extrude materials, the large discharge relief valve 103 is selected, thereby suppressing pressure override of the relief valve.

[Second embodiment]
Next, the extrusion pressure control method according to the second embodiment will be described with reference to FIG. 11. The basic configuration of the extrusion press device according to the second embodiment is basically the same as that of the extrusion press device according to the first embodiment, so the description will be omitted. FIG. 11 is an image diagram of the control flow of the actual extrusion pressure monitoring process in the extrusion pressure control method according to the second embodiment of the present invention. Please note that FIG. 11 is an image diagram showing the main control flow, and is not a control flow that accurately shows the control that is actually performed or the order of the control.

The control flow of the extrusion pressure control method according to the first embodiment shown in FIG. 9 is carried out after the various conditions for extrusion molding are input to the extrusion press device, not during the extrusion process, but during a test run of the extrusion press device or before the extrusion process is started. In contrast, the extrusion pressure control method according to the second embodiment is different from the extrusion pressure control method according to the first embodiment in that it further includes an actual extrusion pressure monitoring process that is activated during the extrusion process. Therefore, the actual extrusion pressure monitoring process will be described with reference to FIG. 11.

In the second embodiment, in the relief valve selection process (F104/Figure 9), it is determined that the set discharge volume of the main pump unit 5 is included in the small discharge volume category LDV, and only the on-off valve 101a is opened, and the extrusion process is started in a state in which the small discharge volume relief valve 101 is selected. The actual extrusion pressure monitoring process is started when the extrusion process starts (ram position L2/Figure 2), and the actual extrusion pressure measured is monitored by a pressure detection means (not shown) arranged in the hydraulic circuit HC2 to see if it is equal to or lower than the rated extrusion pressure Pmax (F201).

The control flow F201 continues until the completion of the extrusion process (ram position L5/Figure 2) (F204). Here, the discharge rate of the main pump unit 5 is increased by feedback control of the extrusion speed near the ram position L3 (Figure 2), and the actual extrusion pressure of the hydraulic circuit HC2 exceeds the rated extrusion pressure Pmax due to the pressure override of the small discharge relief valve 101. If this excess exceeds a preset allowable value, the control flow F201 determines that the actual extrusion pressure is not equal to or lower than the rated extrusion pressure Pmax (NO). As a result, the control flow moves to F202, and it is determined whether it is possible to switch to a relief valve with a lower set relief pressure than the currently selected relief valve (in this case, the small discharge relief valve 101).

In this embodiment, the standard discharge relief valve 102 can be selected, which is set to a main set relief pressure MRP that is lower than the high set relief pressure HRP set in the small discharge relief valve 101. Therefore, in the control flow F202, it is determined that the relief valve can be switched (YES). As a result, the opening/closing valve 101a of the small discharge relief valve 101 selected in the initial relief valve selection process (F104/FIG. 9) is closed, and the opening/closing valve 102a is opened, and reselection is performed to switch the relief valve to the standard discharge relief valve 102 (F203).

In the control flow F203, even after the relief valve is switched from the small discharge relief valve 101 to the standard discharge relief valve 102, the actual extrusion pressure monitoring process continues until the extrusion process is completed (ram position L5/Figure 2) (F204). When the main ram 4a advances further from near the ram position L3, the actual extrusion pressure of the hydraulic circuit HC2 decreases as explained in Figure 3 and elsewhere. Therefore, unless a malfunction or the like occurs in the extrusion press device, it is unlikely that the actual extrusion pressure of the hydraulic circuit HC2 will exceed the rated extrusion pressure Pmax again. As a result, the standard discharge relief valve 102 remains reselected and the extrusion process is completed (F204/YES).

By providing such an actual extrusion pressure monitoring process, in extrusion molding where the set extrusion speed is low and the small discharge relief valve 101 is selected in the relief valve selection process (F104/Figure 9), the reference discharge relief valve 102 responds to the pressure override caused by the temporary increase in the discharge rate of the main pump unit 5 in the feedback control performed when the ram speed rises, and also functions as a safety device in place of the large discharge relief valve 103. In other words, even if the discharge rate of the main pump unit 5 increases during feedback control, the actual extrusion pressure of the hydraulic circuit HC2 is controlled so as not to exceed the rated extrusion pressure Pmax or a high extrusion pressure nearby it.

In addition, even if the relief valve selection process (F104/FIG. 9) determines that the set discharge rate of the main pump unit 5 is included in the standard discharge rate category SDV and the extrusion process is started with only the on-off valve 102a open and the standard discharge rate relief valve 102 selected, it is preferable to operate the actual extrusion pressure monitoring process. That is, if the actual extrusion pressure of the hydraulic circuit HC2 exceeds the rated extrusion pressure Pmax in the actual extrusion pressure monitoring process, reselection may be performed in the control flow F203 to switch the relief valve from the standard discharge rate relief valve 102 to the large discharge rate relief valve 103. Therefore, a detailed description will be omitted.

In rare cases, if the relief valve selection process (F104/Figure 9) determines that the set discharge volume of the main pump unit 5 is included in the large discharge volume category HDV, and if only the on-off valve 103a is opened and the large discharge volume relief valve 103 is selected during the extrusion process and the extrusion process is started, if the actual extrusion pressure of the hydraulic circuit HC2 exceeds the rated extrusion pressure Pmax during the actual extrusion pressure monitoring process, it is determined in control flow F202 that it is difficult to switch the relief valve (NO). If it is determined in control flow F205 that the actual extrusion pressure of the hydraulic circuit HC2 at this time is equal to or lower than the high-pressure abnormal stop pressure, the extrusion process is continued. The high-pressure abnormal stop pressure is the maximum allowable pressure of the actual extrusion pressure of the hydraulic circuit HC2. Therefore, in control flow F205, if it is determined that the actual extrusion pressure of the hydraulic circuit HC2 at this time is not equal to or less than the high-pressure abnormal stop pressure, i.e., exceeds the high-pressure abnormal stop pressure, protection of the extrusion press device is given priority and the extrusion process is stopped at that point (high-pressure abnormal stop/F206).

In such rare cases, when it is expected that the set discharge volume will be determined to be within the large discharge volume category HVD, as explained above, it is preferable to avoid stopping the extrusion process midway through the extrusion process by setting the large discharge volume relief valve 103 to a low set relief pressure LRP that allows the actual extrusion pressure to reach the rated extrusion pressure Pmax or a high extrusion pressure close to it, even if the discharge volume of the main pump unit 5 is 100%.

[Third embodiment]
Next, an extrusion pressure control method according to a third embodiment will be described with reference to Fig. 12 and Fig. 13. The basic configuration of the extrusion press device according to the third embodiment is also basically the same as that of the extrusion press device according to the first embodiment, and therefore the description will be omitted. Fig. 12 is a diagram showing the relationship between the discharge rate stored in the relief valve characteristic storage step, which is newly performed in the discharge rate classification resetting step, and the actual extrusion pressure in the extrusion pressure control according to the third embodiment of the present invention.

In addition to the pressure override caused by the mechanical structure of the relief valve described above, the relief valve has a problem that, due to aging, hydraulic oil leaks from the valve to the tank side, or the amount of hydraulic oil leaks from the valve to the tank side increases, causing a decrease in the actual relief pressure for the same discharge volume of the main pump unit. This will be explained with reference to FIG. 12. FIG. 12 is based on a diagram showing the relationship between the discharge volume stored in the relief valve characteristic storage process F101 described in the extrusion pressure control method according to the first embodiment and the actual extrusion pressure, and the dashed line X in FIG. 12 shows the relationship between the stored discharge volume and the actual extrusion pressure (FIGS. 10(a) and (b)) at the beginning of use of the extrusion press device, such as during a trial run.

On the other hand, in a state where the actual relief pressure for the same discharge volume of the main pump unit has decreased due to aging of the relief valve, the relationship between the newly stored discharge volume and the actual extrusion pressure in the relief valve characteristic storage step F101 of the discharge volume classification resetting step is shown by the solid line Y in FIG. 12. In reality, the smaller the discharge volume of the main pump unit, the more significant the drop in the actual relief pressure is, but for ease of understanding, the broken line X has been moved downward by ΔP and shown by the solid line Y. As shown by the broken line X in FIG. 12, in the relationship between the discharge volume stored in the relief valve characteristic storage step and the actual extrusion pressure in the initial stage of use of the extrusion press device, such as a trial run, a set relief pressure (main set relief pressure MRP) is set at which the actual relief pressure of the hydraulic circuit HC2 reaches the rated extrusion pressure Pmax for the reference discharge volume (30%).

However, as the relief valve ages, specifically as wear occurs in the valve body and seal parts of the tank-facing valve that come into contact when the valve is opened and closed, and as the seal material hardens and deteriorates, the sealing ability of the valve part on the tank side decreases, causing hydraulic oil to leak from the valve to the tank side, or increasing the amount of leakage. As a result, the actual discharge pressure (actual relief pressure) of the hydraulic circuit HC2 becomes lower than the set relief pressure. In Figure 12, the actual relief pressure for the standard discharge volume (30%) is ΔP lower than the main set relief pressure MRP.

When this happens, the premise of the set relief pressure of each relief valve set during trial operation, etc., and similarly the discharge volume classification corresponding to each relief valve set in the discharge volume classification setting step (FIG. 9/F102) during trial operation, etc., will collapse, and the effect of the extrusion pressure control method according to the present invention may be reduced. Therefore, it is preferable that the extrusion pressure control method according to the present invention includes a discharge volume classification resetting step.

The discharge rate category resetting process according to the third embodiment will be described with reference to FIG. 13. FIG. 13 is a diagram showing the resetting of the reference discharge rate category in the discharge rate category resetting process of the extrusion pressure control method according to the third embodiment. As in FIG. 12, the dashed line X shows the relationship between the stored discharge rate and the actual extrusion pressure in the initial stage of use of the extrusion press device, such as a test run. In addition, the solid line Y in FIG. 12 shows the relationship between the newly stored discharge rate and the actual extrusion pressure in the relief valve characteristic storage process F101 of the discharge rate category resetting process in a state in which the actual relief pressure for the same discharge rate of the main pump unit has decreased due to aging of the relief valve.

In the discharge volume classification resetting process, it is preferable to determine in advance a predetermined frequency for performing the relief valve characteristic storage process (F101/FIG. 9). This predetermined frequency is preferably determined for the purpose of avoiding the effect of a decrease in the actual relief pressure for the same discharge volume of the main pump unit due to aging on the quality of the aluminum product W and the molding cycle time in extrusion molding.

On the other hand, as explained above, in order to perform the relief valve characteristic storage process (F101/Fig. 9), it is necessary to return the extrusion press to the trial operation specifications with a trial cold billet, dummy die, etc. set. Therefore, it is preferable that this frequency be set at a frequency that does not significantly affect the productivity of aluminum products, such as the operating rate of the extrusion press. As an example, in the early stages after the extrusion press is installed in a customer's factory, etc. and the actual production of aluminum products W begins, the relief valve characteristic storage process (F101/Fig. 9) is performed relatively frequently, for example, every 2 to 3 months, to check the degree of reduction in actual relief pressure (ΔP/Fig. 12) relative to the standard discharge rate.

If the above frequency is checked and the drop in actual relief pressure relative to the standard discharge volume is small, the frequency can be increased, or if it is greater than expected, the frequency can be decreased. Alternatively, apart from the frequency, a criterion for determining whether the quality of the aluminum product W or the molding cycle time in extrusion molding is being affected can be determined as an allowable value for the aluminum product quality standard, molding cycle time, etc., and when a deviation from this allowable value is confirmed, the relief valve characteristic storage process (F101/Figure 9) can be performed as appropriate.

In addition, the relief valve characteristic storage process (F101/Fig. 9), which is performed at a predetermined frequency or when it is judged necessary, may perform the discharge volume classification setting process (F102/Fig. 9) each time, but the discharge volume classification setting process (F102/Fig. 9) may also be performed when the decrease ΔP in the actual relief pressure relative to the reference discharge volume exceeds a preset allowable value.

In the second and subsequent discharge rate category setting steps (F102/Fig. 9) performed in the discharge rate category resetting step, the standard discharge rate category SDV needs to be reset in consideration of the newly stored relationship between the discharge rate and the actual extrusion pressure, the relief characteristics of the applied relief valve, the set extrusion speed, the rated extrusion pressure, the molding difficulty of the aluminum material to be extruded, and other conditions. Here, an example of a method for resetting the standard discharge rate category SDV in the second and subsequent discharge rate category setting steps (F102/Fig. 9) is given, assuming that the discharge rate of 40% is set as the upper limit of the standard discharge rate category SDV and the discharge rate of 10% is set as the lower limit of the standard discharge rate category SDV in the first (first) discharge rate category setting step (F102/Fig. 9) performed during trial operation, etc., as described with reference to Fig. 10(a).

As shown in FIG. 13, the upper limit of the standard discharge rate category SDV is the actual extrusion pressure (point PU1) of the broken line X corresponding to the previously set upper limit of 40% discharge rate, and the discharge rate Q4 (%) of the solid line Y corresponding to the same actual extrusion pressure (point PU1'). On the other hand, the lower limit is similarly set to the actual extrusion pressure (point PL1) of the broken line X corresponding to the previously set lower limit of 10% discharge rate, and the discharge rate Q3 (%) of the solid line Y corresponding to the same actual extrusion pressure (point PL1'). The standard discharge rate category SDV defined by the new upper limit Q4 and lower limit Q4 is set as the corrected standard discharge rate category SDV2, and the subsequent pump selection process (F103/FIG. 9) and relief valve selection process (F104/FIG. 9) are performed. These processes are the same as those described above, so their description will be omitted.

In addition, in the method of setting the allowable upper limit extrusion pressure Pmaxup and the allowable lower limit extrusion pressure Pmaxlow for the rated extrusion pressure Pmax, which is given as another example of the method of resetting the standard discharge volume category SDV in the initial (first) discharge volume category setting process (F102/Figure 9) performed during trial operation, etc., as explained with reference to Figure 10 (b), although not shown, in the relationship between the discharge volume newly stored by the relief valve characteristic storage process (F101/Figure 9) and the actual extrusion pressure (solid line Y in Figures 12 and 13), the discharge volume corresponding to the actual extrusion pressure that is the same as the allowable upper limit extrusion pressure Pmaxup is set to the upper limit of the corrected standard discharge volume category SDV2, and the discharge volume corresponding to the actual extrusion pressure that is the same as the allowable lower limit extrusion pressure Pmaxlow is set to the lower limit of the corrected standard discharge volume category SDV2. It goes without saying that in the discharge rate category resetting process, a category with a lower discharge rate than the corrected standard discharge rate category SDV2 is reset as a new small discharge rate category LDV by resetting the corrected standard discharge rate category SDV2. Similarly, a category with a higher discharge rate than the corrected standard discharge rate category SDV2 may be reset as a new large discharge rate category HDV.

As described above, with the discharge pressure control method according to the third embodiment, even if the actual relief pressure of the hydraulic circuit for the same discharge volume of the main pump unit 5 drops due to aging or the like, the discharge volume category corresponding to each relief valve is reset, so that it is possible to avoid a decrease in the effect of the discharge pressure control method according to the present invention. In addition, because the amount of leakage due to aging of the relief valve is corrected by resetting the discharge volume category corresponding to each relief valve, there is no need to readjust the set relief pressure of each relief valve.

1 Container, 2 Die, 3 Extrusion stem, 4 Main cylinder, 4a Main ram, 5 Main pump unit, 6 Tank, 10 Relief valve,
101: Small discharge amount relief valve, 102: Standard discharge amount relief valve, 103: Large discharge amount relief valve, 101a/102a/103a: Opening/closing valve,
B Billet, W Aluminum products, HC/HC2 Hydraulic circuits,
LRP Low setting relief pressure, MRP Main setting relief pressure, HRP High setting relief pressure,
LDV small discharge amount classification, SDV standard discharge amount classification, SDV2 corrected standard discharge amount classification,
HDV large discharge volume classification,
X The relationship between the discharge amount stored at the beginning of the test run and the actual discharge pressure (dashed line),
Y: Relationship between the newly stored discharge amount and the actual extrusion pressure (solid line),
a line indicating set relief pressure, b line indicating pressure override,
P: Actual extrusion pressure, Pup: Extrusion pressure at end of upset, Pmax: Rated extrusion pressure,
Pmaxup: upper limit of allowable extrusion pressure, Pmaxlow: lower limit of allowable extrusion pressure,
PU1/PU1'PL1/PL1' Point Q1/Q2/Q3/Q4 Discharge amount (%)

Claims (7)

An extrusion press apparatus including a main pump unit that selectively drives a plurality of hydraulic pumps connected in parallel to discharge a required amount of hydraulic oil,
a mechanical relief valve including a plurality of compression springs or the like and a hydraulic opening/closing mechanism disposed in a hydraulic circuit on a discharge side of the main pump unit;
A selection means for arbitrarily selecting one of the plurality of mechanical relief valves;
a control device that selects the mechanical relief valve by the selection means in accordance with a set discharge amount of the main pump unit based on a set extrusion speed in an extrusion process;
a reference discharge rate relief valve, which is set with a main set relief pressure at which an actual discharge pressure of the hydraulic circuit reaches a rated discharge pressure when the discharge rate of the main pump unit is equal to a reference discharge rate, among the plurality of mechanical relief valves;
a small discharge amount relief valve in which a high set relief pressure is set that is higher by a predetermined amount than the main set relief pressure;
An extrusion press apparatus comprising: The mechanical relief valve is provided with a large discharge amount relief valve in which a low set relief pressure lower than the main set relief pressure by a predetermined amount is set.
The extrusion press apparatus of claim 1 further comprising: 3. A method for controlling an extrusion pressure of an extrusion press apparatus according to claim 1,
a relief valve characteristic storage step of selecting the reference discharge rate relief valve, gradually increasing the discharge rate of the hydraulic oil from the main pump unit while measuring the actual discharge pressure generated, and storing a relationship between the discharge rate and the actual discharge pressure;
A reference discharge amount range including the reference discharge amount is set, and the reference discharge amount relief valve is selected based on the relationship between the discharge amount and the actual extrusion pressure;
a discharge amount section setting step in which the small discharge amount relief valve is selected and a section with a discharge amount smaller than the reference discharge amount section is set as the small discharge amount section;
a pump selection step of calculating the set discharge amount of the main pump unit and selecting the hydraulic pump to be driven based on the set discharge amount;
a relief valve selection step of determining whether the set discharge amount is included in the standard discharge amount category or the small discharge amount category, and selecting the mechanical relief valve set in the determined category;
An extrusion pressure control method for an extrusion press apparatus, comprising: In the discharge amount category setting step, the large discharge amount relief valve is selected, and a category having a discharge amount larger than the reference discharge amount category is set as the large discharge amount category,
When it is determined in the relief valve selection step that the set discharge amount is included in the large discharge amount category, the large discharge amount relief valve is selected.
4. The extrusion pressure control method according to claim 3, for the extrusion press apparatus according to claim 2. In the discharge rate category setting step, an allowable upper limit extrusion pressure and an allowable lower limit extrusion pressure are set with respect to the rated extrusion pressure, and in a relationship between the discharge rate and the actual extrusion pressure, a discharge rate corresponding to an actual extrusion pressure equal to the allowable upper limit extrusion pressure is set as an upper limit of the standard discharge rate category;
5. The extrusion pressure control method for an extrusion press device according to claim 3, wherein a discharge rate corresponding to an actual extrusion pressure equal to the allowable lower limit extrusion pressure is set as a lower limit of the reference discharge rate range. The method further includes an actual extrusion pressure monitoring step of reselecting the mechanical relief valve having a lower set relief pressure than the selected mechanical relief valve, regardless of the relief valve selection step, when the measured actual extrusion pressure exceeds the rated extrusion pressure in the extrusion step .
6. The method for controlling an extrusion pressure of an extrusion press apparatus according to claim 3 . The relief valve characteristic storing step is performed at a predetermined frequency, a new relationship between the discharge amount and the actual extrusion pressure is stored, and the new relationship is compared with the previous relationship between the discharge amount and the actual extrusion pressure.
7. The extrusion pressure control method for an extrusion press device according to claim 3, further comprising a discharge rate category resetting step of, when a difference occurs in the actual extrusion pressure relative to the standard discharge rate in the relationship between each of the discharge rates and the actual extrusion pressure that exceeds a preset allowable value, performing the discharge rate category setting step based on a new relationship between the discharge rate and the actual extrusion pressure, and resetting the standard discharge rate category.

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