Patent Description:
Generally, a wire electrical discharge machine has an auto wire feeding function of automatically inserting a wire electrode into a machining start hole formed in an object to be machined (workpiece) or a machining groove formed by wire electrical discharge machining to perform wire feeding.

However, there are cases where the tip of the wire electrode cannot be inserted into the machining start hole or the machining groove in the workpiece but touches the workpiece, and then the wire electrode is deflected or bent, resulting in failure in auto wire feeding. For this reason, <CIT> discloses a configuration in which when a deflection of the wire electrode is detected, a retry process of auto wire feeding is executed by turning the wire electrode feed rollers in reverse to rewind the wire electrode and then turning the rollers forward to feed the wire electrode.

<CIT> discloses a wire electrical discharge machine comprising a vertical drive device supplying compressed air in upward and downward directions to periodically move a wire electrode vertically.

However, since the motor for turning the roller requires a drive time for actuating the roller from the starting torque to the rated torque, the retry process tends to take time. As a result, there is a concern that the time required for auto wire feeding becomes long disadvantageously.

The present invention has been devised to solve the above problem, it is therefore an object of the present invention to provide a wire electrical discharge machine and an auto wire feeding method of a wire electrical discharge machine, which can shorten the time required for auto wire feeding.

A first aspect of the present invention resides in a wire electrical discharge machine according to claim <NUM>.

A second aspect of the present invention resides in an auto wire feeding method of a wire electrical discharge machine for automatically feeding a wire electrode according to claim <NUM>.

In the present invention, the compressed air slightly moves the tip of the wire electrode in a random manner, so that it is possible to retry insertion of the wire electrode into the machining start hole or the machining groove of the workpiece. Therefore, compared to the case where the motor is controlled to alternately repeat the rewinding and feeding of the wire electrode, it is possible to achieve retry of wire feeding without requiring time to drive the motor from the starting torque to the rated torque. Thus, according to the present invention, it is possible to shorten the time required for auto wire feeding.

The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.

Now, the wire electrical discharge machine and the auto wire feeding method of the wire electrical discharge machine according to the present invention will be detailed by describing preferred embodiments with reference to the accompanying drawings.

<FIG> is a diagram showing a configuration of essential components of a wire electrical discharge machine <NUM> according to the embodiment. The wire electrical discharge machine <NUM> is a machine tool for machining a workpiece W with electric discharge generated between the workpiece W and a wire electrode <NUM>.

The workpiece W is supported on an unillustrated table. The workpiece W may also be referred to as a work. The material of the workpiece W is, for example, a metal material such as an iron-based material or a superhard material (e.g., tungsten carbide). The wire electrode <NUM> is formed of, for example, tungsten-based, copper alloy-based, brass-based metal or the like.

The wire electrical discharge machine <NUM> includes a supply system unit <NUM> for supplying the wire electrode <NUM> to the workpiece W and a collection system unit <NUM> for collecting the wire electrode <NUM> exhausted by machining on the workpiece W.

The supply system unit <NUM> is a unit for feeding the wire electrode <NUM> toward the workpiece W and is arranged above the workpiece W. The supply system unit <NUM> includes at least an unillustrated wire bobbin, feed rollers <NUM>, a guide pipe <NUM>, and a supply side wire guide <NUM>, arranged in order from the upstream side in the feed direction of the wire electrode <NUM>.

The feed rollers <NUM> deliver or feed the wire electrode <NUM> supplied from an unillustrated wire bobbin, which is the supply source of the wire electrode <NUM>, to the workpiece W. The feed rollers <NUM> are rotated by the torque given by a supply side motor <NUM>.

The guide pipe <NUM> is a guide member for guiding the wire electrode <NUM> sent out from the feed rollers <NUM> toward the workpiece W. The guide pipe <NUM> is laid out in a path for feeding the wire electrode <NUM> from the feed rollers <NUM> toward the workpiece W. In the guide pipe <NUM>, an passage hole 22a for allowing the wire electrode <NUM> to pass through is formed in the feed direction (axial direction of the guide pipe <NUM>).

The supply side wire guide <NUM> guides the wire electrode <NUM> that passes through the passage hole 22a of the guide pipe <NUM> toward the downstream side. The supply side wire guide <NUM> has a supply side die guide 24a. The supply side die guide 24a positions the wire electrode <NUM> to be fed to the workpiece W above and near the workpiece W.

The collection system unit <NUM> is a unit for collecting the wire electrode <NUM> fed downward through the workpiece W, and is arranged below the workpiece W. The collection system unit <NUM> includes, at least, a collection side wire guide <NUM>, collecting rollers <NUM> and an unillustrated bucket for collecting the spent wire electrode <NUM>, arranged in order from the upstream side in the feed direction of the wire electrode <NUM>.

The collection side wire guide <NUM> guides the wire electrode <NUM> that has passed through the machining start hole wa or the machining groove wb of the workpiece W, toward the collecting rollers <NUM>. The collection side wire guide <NUM> has a collection side die guide 30a. The collection side die guide 30a positions the wire electrode <NUM> that has passed through the workpiece W, below and near the workpiece W. The wire electrode <NUM> is supported by the supply side die guide 24a and the collection side die guide 30a.

The collecting rollers <NUM> are arranged under the collection side wire guide <NUM> to collect the spent wire electrode <NUM>. The collecting rollers <NUM> are rotated by the torque given by a collection side motor <NUM>. The wire electrode <NUM> taken up by the collecting rollers <NUM> is collected by the unillustrated bucket.

The feed rollers <NUM>, the guide pipe <NUM>, the supply side wire guide <NUM>, the collection side wire guide <NUM>, and the collecting rollers <NUM> are arranged on a straight line in the vertical direction (the direction in which the force of gravity acts). Therefore, the wire electrode <NUM>, which is fed from the feed rollers <NUM> and collected by the collecting rollers <NUM>, is sent along the vertical direction. When the wire electrode <NUM> is collected by the collecting rollers <NUM>, a predetermined tension is applied to the wire electrode <NUM>.

The wire electrical discharge machine <NUM> further includes a wire cutter <NUM>, an airflow generator <NUM>, a deflection detector <NUM>, a tension detector <NUM>, and a control device <NUM>.

The wire cutter <NUM> is provided, for example, between the guide pipe <NUM> and the supply side wire guide <NUM> to cut the wire electrode <NUM>. The wire cutter <NUM> may be controlled by the control device <NUM>. In <FIG>, a blade type cutting tool is illustrated as the wire cutter <NUM> for cutting the wire electrode <NUM>, but other cutting means may be used for the wire cutter <NUM>. For example, electric current may be applied locally to a portion of the wire electrode <NUM> to be cut, to thereby heat and anneal the portion, and thereafter apply torque to the wire electrode <NUM>, whereby the wire electrode is cut at the annealed portion.

The airflow generator <NUM> is a device for generating a flow of compressed air in the passage hole 22a of the guide pipe <NUM>, and includes an air compressor <NUM>, a supply pipe <NUM> and a three-way valve <NUM>. The air compressor <NUM> generates compressed air and injects the generated compressed air into the supply pipe <NUM>.

The supply pipe <NUM> guides the compressed air ejected from the air compressor <NUM> to the passage hole 22a of the guide pipe <NUM>. The supply pipe <NUM> includes a main pipe 52a that communicates the air compressor <NUM> with the three-way valve <NUM>, a first branch pipe 52b that communicates the three-way valve <NUM> with an upper air port 23a of the guide pipe <NUM>, and a second branch pipe 52c that communicates the three-way valve <NUM> with a lower air port 23b of the pipe <NUM>.

The upper air port 23a is formed in the passage hole 22a at a position near an inlet for the wire electrode <NUM> (i.e., on an inlet side for the wire electrode <NUM>) and is located at a different position from the inlet for the wire electrode <NUM>, and communicates with the passage hole 22a. The lower air port 23b is formed in the passage hole 22a at a position near an outlet for the wire electrode <NUM> (i.e., on an outlet side for the wire electrode <NUM>) and is located at a position different from the outlet for the wire electrode <NUM>, and communicates with the passage hole 22a.

The three-way valve <NUM> communicates the main pipe 52a with the first branch pipe 52b or the second branch pipe 52c, and is controlled by the control device <NUM>. When the three-way valve <NUM> communicates the main pipe 52a with the first branch pipe 52b, the compressed air generated by the air compressor <NUM> is injected into the passage hole 22a from the upper air port 23a of the guide pipe <NUM>. An upper part of the passage hole 22a above the upper air port 23a is narrower than a part of the passage hole 22a between the upper air port 23a and the lower air port 23b so that the air-flow resistance in the passage hole 22a becomes higher on the upper side than on the lower side of the upper air port 23a. Therefore, the compressed air flows forward through the passage hole 22a in the same direction as the feed direction of the wire electrode <NUM>.

On the other hand, when the three-way valve <NUM> communicates the main pipe 52a with the second branch pipe 52c, the compressed air generated by the air compressor <NUM> is injected into the passage hole 22a from the lower air port 23b of the guide pipe <NUM>. A lower part of the passage hole 22a below the lower air port 23b is narrower than the part of the passage hole 22a between the upper air port 23a and the lower air port 23b so that the air-flow resistance in the passage hole 22a becomes higher on the lower side than on the upper side of the lower air port 23b. Therefore, the compressed air flows in reverse through the passage hole 22a in the direction opposite to the feed direction of the wire electrode <NUM>.

In this way, the airflow generator <NUM> can switch the direction of the compressed air flowing through the passage hole 22a of the guide pipe <NUM> between the forward direction and the reverse direction.

The deflection detector <NUM> detects deflection of the wire electrode <NUM>. Although the deflection detector <NUM> is installed between the feed rollers <NUM> and the guide pipe <NUM> in <FIG>, the deflection detector <NUM> may be installed at another position. The detection result detected by the deflection detector <NUM> is output to the control device <NUM>.

The tension detector <NUM> detects the tension of the connected wire electrode <NUM>. Although the tension detector <NUM> is installed upstream of the feed rollers <NUM> in <FIG>, the tension detector <NUM> may be installed at another position. The detection result detected by the tension detector <NUM> is output to the control device <NUM>.

The control device <NUM> includes a processor such as a CPU and a memory in which a program is stored, and the processor runs a program stored in the memory to thereby provide the function as the control device <NUM> of the present embodiment. The control device <NUM> is a computer that appropriately controls diverse parts (the supply side motor <NUM>, the collection side motor <NUM> and the airflow generator <NUM>) of the wire electrical discharge machine <NUM>.

The control device <NUM> starts the auto wire feeding process at the start of machining or after cutting of the wire electrode <NUM> by the wire cutter <NUM>. That is, the control device <NUM> controls the airflow generator <NUM> to thereby generate a forward flow of compressed air in the passage hole 22a of the guide pipe <NUM>. Specifically, the control device <NUM> controls the three-way valve <NUM> to establish communication between the main pipe 52a and the first branch pipe 52b, and thereafter actuates the air compressor <NUM> to thereby create forward flow of compressed air in the passage hole 22a of the guide pipe <NUM>.

In this state, as the control device <NUM> controls the supply side motor <NUM> to rotate the feed rollers <NUM>, the wire electrode <NUM> is sent out from the wire bobbin to the workpiece W.

In this way, the control device <NUM> feeds the wire electrode <NUM> to the workpiece W while generating compressed air flowing in the forward direction through the passage hole 22a of the guide pipe <NUM>. As a result, the control device <NUM> can move the wire electrode <NUM> forward while preventing slack of the wire electrode <NUM> by compressed air. Therefore, the wire electrode <NUM> can be easily inserted into the machining start hole wa or the machining groove wb of the workpiece W.

In order to collect the wire electrode <NUM> passing through the machining start hole wa or the machining groove wb of the workpiece W, the control device <NUM> controls the collection side motor <NUM> to start rotating the collecting rollers <NUM> before the wire electrode <NUM> fed by the feed rollers <NUM> reaches the collecting rollers <NUM>.

Further, when starting auto wire feeding, the control device <NUM> monitors the deflection and tension of the wire electrode <NUM> during auto wire feeding, based on the outputs from the deflection detector <NUM> and the tension detector <NUM>. The term "during auto wire feeding" means a period from the time at which the feed rollers <NUM> starts feeding the wire electrode <NUM> downward in order to start auto wire feeding of the wire electrode <NUM> until the time at which the wire electrode <NUM> is fed by a predetermined length. The predetermined length is a distance from the feed rollers <NUM> to the collecting rollers <NUM> at least. If the wire electrode <NUM> is fed downward by at least the distance from the feed rollers <NUM> to the collecting rollers <NUM>, the wire electrode <NUM> is collected by the collecting rollers <NUM> so that a predetermined tension is applied to the wire electrode <NUM>. Therefore, the control device <NUM> can determine that the auto wire feeding is successful, based on the output from the tension detector <NUM>.

Specifically, when the deflection detector <NUM> has detected no deflection of the wire electrode <NUM> while the tension detector <NUM> detects a tension equal to or higher than a threshold until the predetermined length of the wire electrode <NUM> is fed, the control device <NUM> determines that the auto wire feeding is successful. In this case, the control device <NUM> stops the airflow generator <NUM>, the supply side motor <NUM> and the collection side motor <NUM> to complete the auto wire feeding process.

On the other hand, when the deflection detector <NUM> detects a deflection of the wire electrode <NUM> before the predetermined length of the wire electrode <NUM> is fed, the tip of the wire electrode <NUM> abuts against the workpiece W or any other object because the wire electrode <NUM> cannot be inserted through the machining start hole wa or the machining groove wb of the workpiece W or for any other reason. In this case, the control device <NUM> starts a retry process.

That is, the control device <NUM> controls the supply side motor <NUM> and the collection side motor <NUM> to stop the feed rollers <NUM> and the collecting rollers <NUM>. In this state, the control device <NUM> controls the airflow generator <NUM> to alternately switch the direction of the compressed air flowing through the passage hole 22a of the guide pipe <NUM> between the reverse direction and the forward direction.

Specifically, the control device <NUM> controls the three-way valve <NUM> so as to switch connection of the main pipe 52a of the supply pipe <NUM> in turns to the second branch pipe 52c and to the first branch pipe 52b, thereby switch the direction of compressed air flowing through the passage hole 22a of the pipe <NUM> between the reverse direction and the forward direction. Note that this switching operation is performed, for example, about several times per second.

As a result, the control device <NUM> can slightly move the tip of the wire electrode <NUM> in a random manner. Therefore, the wire electrode <NUM> can be easily inserted into the machining start hole wa or the machining groove wb of the workpiece W even if the tip of the wire electrode <NUM> collides with or touches the workpiece W or any other object because the wire electrode <NUM> cannot be inserted through the machining start hole wa or the machining groove wb of the workpiece W or for any other reason.

When the deflection that has been detected by the deflection detector <NUM> becomes undetected, the control device <NUM> controls the airflow generator <NUM> to maintain the direction of compressed air flowing through the passage hole 22a of the guide pipe <NUM> in the forward direction, and terminates the retry process. Thereafter, the control device <NUM> controls the supply side motor <NUM> to rotate the feed rollers <NUM> again and resume the feeding of the wire electrode <NUM>, thereby resuming auto wire feeding.

On the other hand, when the deflection of the wire electrode <NUM> does not become undetected by the deflection detector <NUM> even after the number of times that the flowing direction of the compressed air has been alternately switched between the reverse direction and the forward direction exceeds a predetermined number of times, the control device <NUM> determines that auto wire feeding has failed. In this case, the control device <NUM> stops the airflow generator <NUM> and terminates the retry process and the auto wire feeding process. When the auto wire feeding fails, the wire electrode <NUM> is cut by the wire cutter <NUM>, and the auto wire feeding process is restarted as necessary.

Next, the auto wire feeding method of the wire electrical discharge machine <NUM> will be described. <FIG> is a flow chart showing a flow of an auto wire feeding process executed by the control device <NUM> of the wire electrical discharge machine <NUM>.

At step S1, the control device <NUM> controls the airflow generator <NUM> so as to generate a forward flow of compressed air in the passage hole 22a of the guide pipe <NUM>, then the control goes to step S2. At step S2, the control device <NUM> controls the supply side motor <NUM> to turn the feed rollers <NUM>, thereby starting feeding of the wire electrode <NUM>. The control device <NUM> also controls the collection side motor <NUM> to turn the collecting rollers <NUM>, and the control proceeds to step S3.

At step S3, the control device <NUM> determines whether or not a deflection of the wire electrode <NUM> has been detected by the deflection detector <NUM>. When no deflection of the wire electrode <NUM> is detected, the control proceeds to step S4.

At step S4, the control device <NUM> determines whether or not the auto wire feeding has succeeded. Here, when the wire electrode <NUM> is collected by the collecting rollers <NUM> without slack or deflection of the wire electrode <NUM> and the tension detector <NUM> detects a tension that is equal to or greater than the threshold value, the control device <NUM> determines that the auto wire feeding has been successfully done. On the other hand, if the wire electrode <NUM> has not yet been collected by the collecting rollers <NUM> and tension equal to or greater than the threshold value is not detected, the control device <NUM> determines that the auto wire feeding has not yet been successful, and the control returns to step S3 so as to monitor the deflection of the wire electrode <NUM> based on the output from the deflection detector <NUM>.

When deflection of the wire electrode <NUM> is detected at step S3, the control proceeds to step S5, in which the control device <NUM> executes a retry process. The operation of this retry process will be described later. When the deflection of the wire electrode <NUM> becomes undetected by executing the retry process, the control proceeds to step S4. When the deflection of the wire electrode <NUM> does not become undetected even after the retry process has been executed, the control goes to step S6.

At step S6, the control device <NUM> stops the airflow generator <NUM>, and the control proceeds to step S7. At step S7, the control device <NUM> controls the supply side motor <NUM> to stop the feed rollers <NUM>, whereby feeding of the wire electrode <NUM> is stopped. Thus, the auto wire feeding process is completed.

Next, the retry process will be described. <FIG> is a flowchart showing the flow of the retry process at step S5 shown in <FIG>.

At step S11, the control device <NUM>, by controlling the supply side motor <NUM> and the collection side motor <NUM>, stops the feed rollers <NUM> and the collecting rollers <NUM> so that feeding of the wire electrode <NUM> is stopped. Then, the control proceeds to step S12.

The control device <NUM> controls the airflow generator <NUM> so as to cause compressed air to flow in the passage hole 22a of the guide pipe <NUM> in the reverse direction at step S12, and then controls the airflow generator <NUM> so as to cause compressed air to flow in the passage hole 22a of the guide pipe <NUM> in the forward direction at step S13. Thereafter, the control device <NUM> proceeds to step S14.

At step S14, the control device <NUM> determines whether or not deflection of the wire electrode <NUM> has become undetected by the deflection detector <NUM>. If it is undetected, the control device <NUM> proceeds to step S15. At step S15, the control device <NUM> controls the supply side motor <NUM> and the collection side motor <NUM> to turn the feed rollers <NUM> and the collecting rollers <NUM> again so as to resume the feeding of the wire electrode <NUM>. Thus, the control device <NUM> terminates the retry process and goes to step S4 (see <FIG>).

On the other hand, if the deflection of the wire electrode <NUM> has not become undetected at step S14, the control device <NUM> proceeds to step S16 and determines whether or not the number of times the retry operation has been performed exceeds a predetermined number of times. The retry operation is an operation for switching the flow direction of compressed air in the passage hole 22a between the reverse direction and the forward direction successively at steps S12 and S13, and one set of the steps S12 and S13 corresponds to one retry operation.

If the number of times of retry operation does not exceed the predetermined number of times, the control device <NUM> returns to step S12 and sequentially executes step S12 and step S13 to alternately switch the flow direction of the compressed air between the reverse direction and the forward direction. When the number of times of retry operation exceeds the predetermined number of times, the control device <NUM> determines that the auto wire feeding has failed. In this case, the control device <NUM> ends the retry process and proceeds to step S6 (see <FIG>).

As described above, in the present embodiment, when deflection of the wire electrode <NUM> is detected during auto wire feeding, the feeding of the wire electrode <NUM> is stopped while the airflow generator <NUM> is controlled so as to change the direction of the compressed air flowing through the passage hole 22a in the guide pipe <NUM> to the reverse direction and then switch to the forward direction.

As a result, in this embodiment, the tip of the wire electrode <NUM> can be slightly moved in a random manner by compressed air. Therefore, in the present embodiment, when the wire electrode <NUM> touches or abuts against the workpiece W or any other object and thereby undergoes a deflection due to deviation of the wire electrode <NUM> from the machining start hole wa or the machining groove wb, it is possible to retry to insert the wire electrode <NUM> into the machining start hole wa or the machining groove wb by compressed air.

Accordingly, in the present embodiment, it is possible to achieve retry of auto wire feeding without requiring time to drive the motor from the starting torque to the rated torque, which would be needed in the case where the supply side motor <NUM> is controlled to repeat rewinding and feeding of the wire electrode <NUM> alternately. As a result, according to the present embodiment, it is possible to shorten the time required for auto wire feeding.

When the supply side motor <NUM> is controlled to alternately repeat the rewinding and feeding of the wire electrode <NUM>, the wire electrode <NUM> tends to move up and down regularly at the same position. In contrast to this, in the present embodiment, as described above, the tip of the wire electrode <NUM> is slightly moved irregularly at different positions by the viscosity of the compressed air. Therefore, according to the present embodiment, as compared to the case where the supply side motor <NUM> is controlled to alternately repeat the rewinding and feeding of the wire electrode <NUM>, the wire electrode <NUM> can be inserted more easily through the machining start hole wa or the machining groove wb.

In addition, as compared to the case where the supply side motor <NUM> is controlled to alternately repeat the rewinding and feeding of the wire electrode <NUM>, the moving length of the tip of the wire electrode <NUM> when it slightly moves tends to be smaller. Therefore, according to the present embodiment, by slightly moving the tip of the wire electrode <NUM> finely and irregularly in a short time in a minutely vibrating manner, it is possible to shorten the time required for auto wire feeding while enabling easy insertion of the wire electrode <NUM> into the machining start hole wa or the machining groove wb.

Though the present invention has been described by referring to the embodiment as an example, the technical scope of the present invention should not be limited to the range of the above embodiment. It goes without saying that various modifications and improvements can be added to the above embodiment. Further, it is also apparent from the scope of claims that those added with such modifications and improvements should be incorporated in the technical scope of the invention.

<FIG> is a partly enlarged diagram showing a wire electrical discharge machine of Modification <NUM> according to the invention, modified from that shown in <FIG>. Herein, the same components as those described above are allotted with the same reference numerals and repeated explanation will be omitted as appropriate.

The airflow generator <NUM> in the wire electrical discharge machine <NUM> of Modification <NUM> further includes a turbulence generating member <NUM>. The turbulence generating member <NUM> disturbs the flow of compressed air and is detachably arranged in the lower air port 23b of the guide pipe <NUM>.

<FIG> is a diagram showing a configuration example (<NUM>) of the turbulence generating member <NUM>. The turbulence generating member <NUM> shown in <FIG> has a substantially oval shaped main body 56a and flow passages 56b formed in the main body 56a. The flow passage 56b is a recessed portion on the minor axis side of the main body 56a. Screw thread grooves 56c are formed on the major axis side of the main body 56a. The screw thread grooves 56c correspond to screw thread ridges formed on the wall of the guide pipe <NUM> around the lower air port 23b.

Therefore, the turbulence generating member <NUM> shown in <FIG> can be screwed to the wall of the guide pipe <NUM> around the lower air port 23b. In this arrangement, gaps are formed between the wall of the guide pipe <NUM> around the lower air port 23b and the flow passages 56b of the turbulence generating member <NUM> provided in the lower air port 23b, and compressed air passes through the gaps. The flow passages 56b can be shifted by turning the main body 56a on the screw thread grooves 56c.

Instead of the turbulence generating member <NUM> shown in <FIG>, it is also possible to provide a turbulence generating member <NUM> shown in <FIG> or a turbulence generating member <NUM> shown in <FIG>. The turbulence generating members <NUM> shown in <FIG> and <FIG> have a cylindrical main body 56d and flow passages 56e formed in the main body 56d.

The main body 56d is fitted into the lower air port 23b in a slidable manner on the wall of the guide pipe <NUM> around the lower air port 23b. Therefore, the flow passages 56e can be shifted by sliding the main body 56d. The flow passage 56e penetrates from one end face of the main body 56d to the other end face. The flow passage in the example shown in <FIG> has a circular cross-section, whereas the flow passage in the example shown in <FIG> has a fan shaped cross-section, but other shapes may be used. Although the number of the flow passages 56e is three in the examples shown in <FIG> and <FIG>, more than three flow passages or a single flow passage is possible.

In the wire electrical discharge machine <NUM> of Modification <NUM>, the turbulence generating member <NUM> is provided in the lower air port 23b of the guide pipe <NUM>, so that it is possible to disperse the compressed air injected from the air compressor <NUM> into the lower air port 23b via the second branch pipe 52c to thereby produce turbulent flow of air. As a result, it is possible to slightly move the tip of the wire electrode <NUM> more irregularly by the compressed air flowing through the passage hole 22a of the guide pipe <NUM> through the flow passages 56b of the turbulence generating member <NUM>.

It should be noted that the turbulence generating member <NUM> may have a configuration other than the configurations shown in <FIG>, for example, a protrusion or the like which protrudes from the wall of the guide pipe <NUM> around the lower air port 23b toward the interior of the lower air port 23b.

In addition, although the turbulence generating member <NUM> is provided in the lower air port 23b of the guide pipe <NUM>, it may be provided in the second branch pipe 52c. In other words, the turbulence generating member <NUM> may be provided on the flow path through which compressed air flows between a position at which the compressed air is injected and a position near the outlet for the wire electrode <NUM> in the passage hole 22a. More specifically, this flow path corresponds to a flow path from the air compressor <NUM> to the lower air port 23b. In order to slightly move or vibrate the tip of the wire electrode <NUM> in a more random manner, the turbulence generating member <NUM> is preferably arranged in the lower air port 23b.

<FIG> is a diagram showing a configuration of essential components of a wire electrical discharge machine <NUM> of Modification <NUM>. Herein, the same components as those described above are allotted with the same reference numerals and repeated explanation will be omitted as appropriate.

The wire electrical discharge machine <NUM> of Modification <NUM> has an airflow generator 42A that is different from the airflow generator <NUM> of the above embodiment. The airflow generator 42A further includes an ejector <NUM>. The ejector <NUM> communicates with the three-way valve <NUM> via the second branch pipe 52c and communicates with the first branch pipe 52b via a communication pipe 60a.

In this airflow generator 42A, when the three-way valve <NUM> connects the main pipe 52a with the first branch pipe 52b, the compressed air generated by the air compressor <NUM> is injected from the upper air port 23a of the guide pipe <NUM> into the passage hole 22a. Therefore, the compressed air flows through the passage hole 22a in the forward direction or the same direction as the feed direction of the wire electrode <NUM>.

On the other hand, when the three-way valve <NUM> connects the main pipe 52a with the second branch pipe 52c, the compressed air generated by the air compressor <NUM> is discharged to the outside via the ejector <NUM>. Along with this discharge, the air (compressed air) of the guide pipe <NUM> flows in the reverse direction through the passage hole 22a and is drawn from the upper air port 23a via the communication pipe 60a by the ejector <NUM>.

In this way, the airflow generator 42A of Modification <NUM> draws in the air inside the passage hole 22a from the inlet side for the wire electrode <NUM> in the passage hole 22a so that the compressed air flows through the passage hole 22a in the reverse direction.

Therefore, similarly to the airflow generator <NUM> of the above-described embodiment in which compressed air is injected from the outlet side for the wire electrode <NUM> in the passage hole 22a, the airflow generator 42A of Modification <NUM> is able to switch the flow direction of compressed air flowing through the passage hole 22a between the forward direction and the reverse direction.

In the above embodiments, the feed rollers <NUM>, the guide pipe <NUM>, the supply side wire guide <NUM>, the collection side wire guide <NUM> and the collecting rollers <NUM> are arranged vertically (i.e., in the direction of gravitational force) on a straight line in this order from the upstream side of the wire feeding direction. However, the feed rollers <NUM>, the guide pipe <NUM>, the supply side wire guide <NUM>, the collection side wire guide <NUM>, and the collecting rollers <NUM> may be arranged on a straight line in order from the upstream side of the wire feeding direction in a direction intersecting the vertical direction or the direction of gravitational force.

In the above embodiment, determining the success or failure of auto wire feeding is based on whether or not the tension detector <NUM> detects a tension that is equal to or greater than the threshold when the wire electrode <NUM> is collected by the collecting rollers <NUM> without slack or deflection of the wire electrode <NUM>. However, other methods may be used as a method for determining the success or failure of auto wire feeding.

For example, a detector plate may be arranged on the downstream side of the collecting rollers <NUM> in the wire feeding direction, so as to determine that the auto wire feeding is successful when contact of the wire electrode <NUM> is detected by the detector plate and determine that the auto wire feeding has failed when no contact is detected by the detector plate. It should be noted that this determination method and the determination method of the above embodiments may be used together.

Claim 1:
A wire electrical discharge machine (<NUM>), comprising:
a feed roller (<NUM>) configured to feed a wire electrode (<NUM>) toward a workpiece (W);
a collecting roller (<NUM>) configured to collect the wire electrode (<NUM>) having passed through the workpiece (W);
a guide member (<NUM>) arranged on a path for feeding the wire electrode (<NUM>) from the feed roller (<NUM>) toward the workpiece (W) and having therein a passage hole (22a) through which the wire electrode (<NUM>) is passed;
an airflow generator (<NUM>, 42A) configured to generate a flow of compressed air in the passage hole (22a) and to switch a flow direction of the compressed air flowing through the passage hole (22a) between a forward direction which corresponds to a feeding direction of the wire electrode (<NUM>) and a reverse direction opposite to the feeding direction of the wire electrode (<NUM>);
a deflection detector (<NUM>) configured to detect a deflection of the wire electrode (<NUM>); and
a control device (<NUM>) configured to control the airflow generator (<NUM>, 42A) so as to generate a flow of the compressed air in the forward direction in the passage hole (22a) during auto wire feeding and so as to, when the deflection detector (<NUM>) detects the deflection, change the flow direction of the compressed air flowing through the passage hole (22a) to the reverse direction and thereafter switch the flow direction of the compressed air from the reverse direction to the forward direction,
wherein the airflow generator (<NUM>, 42A) is configured to inject the compressed air into the passage hole (22a) from an outlet side for the wire electrode (<NUM>) in the passage hole (22a) so that the compressed air flows through the passage hole (22a) in the reverse direction,
characterised in that
the airflow generator (<NUM>) includes a turbulence generating member (<NUM>) configured to disturb the flow of the compressed air, the turbulence generating member (<NUM>) being arranged on a flow path of the compressed air between the outlet side for the wire electrode (<NUM>) in the passage hole (22a) and a position at which the compressed air is injected.