JP6779271B2 - Machine Tools - Google Patents

Description

The present invention relates to a machine tool, in particular a machine tool configured to hold a tool at the front end, which is one end in the longitudinal direction of the ram, and move the ram back and forth with respect to the bed. is there.

Conventionally, for example, as shown in Patent Documents 1 and 2, a ram having a machining head for holding a tool is attached to a front end portion which is one end portion in the length direction, and this ram is moved in the front-rear direction. Machine tools such as electric discharge machines that change the machining position with a tool are known. In the present specification, the length direction of the ram is referred to as the front-rear direction, and the end portion that holds the tool is referred to as the front end portion. This type of machine tool has a so-called overhang structure in which the ram protrudes forward with respect to the column that supports the ram so as to be movable in the front-rear direction.

In the overhang structure, the mass of the machining head and the weight of the ram, especially in the case of a die-sinking electric discharge machine, the mass of the holding tool electrode is also added, and the part near the front end of the ram is deformed so as to bend downward. It will be easier. In order to set a wide machining area of the machine tool, the larger the moving stroke of the ram in the front-rear direction, the larger the overhang and the more remarkable the deformation of the ram. When the ram is deformed in this way, the machining head including the tool is displaced, which causes a decrease in machining accuracy corresponding to the amount of this displacement. If the movement stroke of the ram in the front-rear direction is small, the overhang of the ram is small and the amount of displacement is small, but it is not always possible to completely prevent the deterioration of machining accuracy. Further, even when the ram does not move in the front-rear direction, if the overhang amount of the ram is relatively large or the mass of the processing head is large, the same problem as described above may occur.

In order to prevent the deformation of the ram as described above, it is conceivable to form the ram so as to have high physical rigidity. However, since the ram, which is the structure of the machine, is basically formed of cast iron, the weight of the ram increases when trying to form it with high rigidity, and on the contrary, the rigidity of the ram increases in response to the increased weight. It falls into the contradiction that it is required to be high. Further, when the ram is a moving body, when the weight of the ram becomes large, a larger output is required for a drive device including a servomotor or the like that moves the ram in order to secure a predetermined control responsiveness. It also becomes.

In order to prevent a decrease in machining accuracy due to the deformation of the ram described above, it is conceivable to eliminate the error in the machining position in the machining head by correction by software. However, such a method is effective to some extent when the machining head is relatively lightweight and therefore the ram is relatively small, but it is often not effective for large machine tools. Further, since the machining head moves, the correction cannot follow the relative fluctuation of the error, and it is difficult to obtain high machining accuracy.

Conventionally, other techniques for preventing the above-mentioned deformation of the ram and the resulting decrease in processing accuracy have also been proposed. For example, Patent Document 1 discloses a technique for ensuring high rigidity while suppressing an increase in weight by providing some ribs on a ram. Further, Patent Document 2 discloses a technique in which the rear end side of the ram is positively deformed by a spring or the like, and the deformation of the front end side of the ram is offset by the deformation of the rear end side.

Japanese Patent No. 3837910 Japanese Patent No. 3570006

However, although the technique shown in Patent Document 1 can suppress an increase in the weight of the ram, it still cannot fundamentally solve the above-mentioned conventional problems. Further, the technique shown in Patent Document 2 cannot prevent deformation of both the front end side and the rear end side of the ram.

The present invention has been made in view of the above circumstances, and provides a machine tool capable of preventing deformation of the ram on the front end side and being compact and lightweight, particularly when the front end side of the ram is in an overhang state. The purpose is to do.

The machine tool according to the present invention
A ram that supports the tool at the front end, which is one end in the length direction,
A column that supports the ram so that it can move in the front-back direction, with its length extending approximately horizontally.
A ram driving means that moves the ram back and forth,
In machine tools that have
It consists of a member arranged so as to extend along the length direction of the ram, and is supported by the ram by being rotatable around a substantially horizontal axis set at a predetermined position of the member and the ram, and is supported by the ram. On the front side, a rotating member that is connected to a part of the ram so that the upward force due to the rotation can be transmitted.
A balance weight mounted on this rotating member so that it can move in the front-rear direction,
A balance weight driving means that moves this balance weight more backward as the ram moves forward with respect to the column.
It is characterized by having.

In addition, regardless of the name of the "column", a structure that can be regarded as a structure equivalent to the column in terms of structure is included in the present invention. The above "front-back direction" is the length direction of the ram, and the side holding the tool is defined as "front" and the opposite side is defined as "rear". Further, the "predetermined position" of the member and the ram constituting the rotating member refers to a position between the front end and the rear end of each of the rotating member and the ram, and the rotating member can be seen. When the horizontal axis at the predetermined position is used as the fulcrum of the lever, the predetermined position is provided so that the center position of the balance weight is always located behind the ram with respect to the center of this axis.

Further, as described above, the structure in which the rotating member is rotatably supported by the ram is held in, for example, a hole such as a circular hole or an elongated hole formed in one of the ram and the rotating member and held in the other. A structure in which the shaft body is inserted can be applied. Further, as a structure in which the rotating member is rotatably supported by the ram, a shaft body held by the other is inserted into an internal hole of a rubber bush formed in one of the ram and the rotating member. A structure in which the ram is supported in a seesaw shape on a fulcrum provided on the ram can also be applied.

On the other hand, as a structure for transmitting an upward force due to the rotation of the rotating member to a part of the ram, for example, a hole such as a circular hole or an elongated hole formed in one of the ram and the rotating member may be used. A structure or the like through which a shaft body held on the other side is inserted can be applied. Further, as a structure in which an upward force due to the rotation of the rotating member is transmitably connected to a part of the ram in this way, in addition, one of the rams is attached to the ascending moving portion of the rotating rotating member. A structure in which the portions are brought into contact with each other from above is also applicable.

In the machine tool according to the present invention, further
An arm suspension member fixed in an upright position at an intermediate position in the length direction of the ram,
A front arm in which one end is connected to the arm suspension member and the other end is connected to a portion near the front end of the ram below the front side of the connection position.
A first tension-applying means that applies tension to the front arm that acts to pull up the connecting ram portion.
A rear arm in which one end is connected to an arm suspension member and the other end is connected to a portion near the rear end of the ram below the position of this connection.
A second tension applying means that applies tension to the rear arm that acts to pull up the connecting ram portion, and
Is desirable to be provided.

Here, the "portion near the front end" of the ram is a portion between the front end and the center within a range in which the effect of sufficiently pulling up the ram in the present invention can be obtained. Specifically, in the case of a ram having a general structure made of cast iron, it refers to a portion in a range of up to 20% of the total length of the ram from the front end to the center side. The same applies to the "near rear end portion".

In the machine tool of the present invention, since the rotating member, the balance weight, and the balance weight driving means as described above are provided, when the ram moves forward and the overhang amount becomes large, the rotating member Due to the balance weight located behind the above-mentioned axis, a moment for rotating the rotating member around the axis acts. Since this moment acts in the direction of pushing down the rotating member of the portion on which the balance weight is placed, the rotating member applies an upward force to a part of the ram on the front side of the shaft. As a result, the front end portion of the ram is pulled up to prevent the front end portion from being deformed so as to bend downward, and thus the position of the tool is prevented from shifting and the machining accuracy is prevented from deteriorating. Since the machine tool of the present invention does not have to make the ram itself unnecessarily rigid, it can be constructed to be compact and lightweight.

Top view showing a machine tool according to the first embodiment of the present invention. Side view showing the machine tool of FIG. Partial front view showing a part of the machine tool of FIG. 1 along the AA line. Partial side view showing a part of the machine tool of FIG. Side view showing a state different from FIG. 2 of the machine tool of FIG. Side view showing a state further different from FIG. 2 of the machine tool of FIG. Top view showing the main part of the machine tool of FIG. Side view showing the main part of the machine tool of FIG. Top view showing a machine tool according to the second embodiment of the present invention. Side view showing the machine tool of FIG. Partial front view showing a portion of the machine tool of FIG. 9 along the AA line. Partial side view showing a part of the machine tool of FIG. Side view showing a state different from FIG. 10 of the machine tool of FIG. A side view showing a state further different from that of FIG. 10 of the machine tool of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1, FIG. 2 and FIG. 3 show a planar shape, a side surface shape, and a partial front shape of the machine tool 1 according to the first embodiment of the present invention, respectively. The machine tool 1 of the present embodiment is an electric discharge machine as an example, and has a structure 10, a ram 30 mounted on the structure 10, and a rotating member 50 combined with the ram 30. ing. As shown in FIGS. 1 to 3, the front-rear direction of the ram 30 made of horizontally arranged long members is the Y-axis direction, and the horizontal direction perpendicular to the Y-axis direction is the X-axis direction, the vertical direction, that is, the vertical direction. Is defined as the Z-axis direction. Regarding the Y-axis direction, the front end side of the ram 30 (the end that holds the electric discharge machining head 31 described later) is the + Y-axis direction, and the rear end side of the ram 30 is the −Y-axis direction.

The structure 10 is fixed on a rear bed 12, which is a base horizontally fixed to a fixed surface 11 such as a factory floor, a slider 13 arranged on the bed 12, and the slider 13. It is composed of a saddle 14 and a column that reciprocates in the X-axis direction. Two rails 15 are fixed to the upper surface of the bed 12 as an example of extending in the X-axis direction. A plurality of linear guides 16 fixed to the lower surface of the slider 13 are engaged with each of these rails 15, whereby the column can be reciprocated in the X-axis direction on the bed 12.

Two rails 17 are fixed to the lower surface of the ram 30 as an example of extending in the Y-axis direction. Each of these rails 17 is engaged with a plurality of linear guides 18 fixed to the upper surface of the saddle 14, whereby the ram 30 can reciprocate on the saddle 14 in the Y-axis direction. Further, the electric discharge machining head 31 held at the front end of the ram 30 holds the tool electrode 31a at the lower portion, and the tool electrode 31a can be reciprocated in the Z-axis direction by a driving means (not shown) housed inside. It is configured.

On the front side of the rear bed 12, the front bed 20 is fixed to the fixed surface 11, and the processing tank 21 is supported on the bed 20. The processing liquid 22 is stored in the processing tank 21, and the work piece 23 is placed on a table provided on the bed 20. EDM is performed by the tool electrode 31a that moves relative to the workpiece 23 arranged in the machining fluid 22 in the horizontal biaxial direction and the vertical uniaxial direction. Regarding the position of electric discharge machining on the workpiece 23, the slider 13 is moved by a driving means (not shown) in the X-axis direction, the ram 30 is moved by a driving means (not shown) in the Y-axis direction, and the ram 30 is moved by a driving means (not shown) in the Z-axis direction. The electric discharge machining head 31 is moved by a driving means (not shown) and can be changed as appropriate.

In the side view of FIG. 2, the position where the ram 30 protrudes most forward (in the + Y direction) with respect to the column consisting of the slider 13 and the saddle 14, that is, the position where the overhang amount is maximum is shown. The relative position of the ram 30 with respect to this column is a position where the overhang amount is medium, a position where the overhang amount is minimum, and the like, corresponding to changing the position of electric discharge machining on the workpiece 23. obtain. 5 and 6 show the side shapes when the ram 30 takes those positions, respectively.

Next, the structure of the ram 30 and its surroundings will be described in detail. Here, in FIGS. 7 and 8, the ram 30 and the structure integrated with the ram 30 are extracted, and their planar shape and side surface shape are shown. In the following, these figures will also be referred to and described. The ram 30 is a long member made of cast iron, for example, and holds the electric discharge machining head 31 at the front end portion which is the end portion in the + Y axis direction. An arm suspension member 32 standing upward is fixed at an intermediate position in the length direction of the ram 30. The "intermediate position" means a position between the front end and the rear end of the ram 30, and it is desirable, but not limited to, a central position where the distances from both ends are equal. Note that FIG. 3 is a partial front view showing a part of the machine tool 1 as viewed from a portion along the line AA shown in FIG. 2, and some bolts and the like are omitted in FIG.

The arm suspension member 32 is made of steel, for example, and is composed of a base portion 33 fixed to the ram 30 and an arm connecting portion 34 supported by the base portion 33 so as to be movable in the vertical direction above the base portion 33. .. The arm connecting portion 34 is connected to, for example, a steel front arm 35 and a rear arm 36, which are connected to the ram 30, respectively. That is, one end of the front arm 35 is connected to the arm connecting portion 34, and the other end of the front arm 35 is connected to the portion near the front end of the ram 30 at the lower front side of the connecting position. Further, one end of the rear arm 36 is connected to the arm connecting portion 34, and the other end of the rear arm 36 is connected to a portion near the rear end of the ram 30 below the rear end of the connecting position. .. Here, the "portion near the front end" and the "portion near the rear end" of the ram 30 are, for example, a range within the center of the ram from the front end and the rear end of the ram 30 by a length of 20% or less of the total length of the ram. It shall point to.

More specifically, the base 33 is fixed to the upper surface of the ram 30 by a plurality of bolts 43. Further, the arm connecting portion 34 is composed of a bracket (horizontal plate) 34a arranged so as to extend in the horizontal direction, and two vertical plates 34b rising from the bracket 34a. An arm upper support shaft 44 extending in the X-axis direction is fixed to the vertical plate 34b, and an arm upper support shaft 45 extending in the X-axis direction rearward from the arm upper support shaft 44, that is, in the −Y axis direction. It is fixed. One end of the front arm 35 described above is connected to the arm connecting portion 34 by inserting the arm upper support shaft 44 into the circular hole 35a so that the arm upper support shaft 44 can rotate around the arm upper support shaft 44. One end of the rear arm 36 described above is connected to the arm connecting portion 34 by inserting the arm upper support shaft 45 into the circular hole 36a so as to be rotatable around the arm upper support shaft 45.

On the other hand, the front end side bracket 38 and the rear end side bracket 39 are fixed to the ram 30 by a plurality of bolts 40, respectively, on the upper surfaces of the front end vicinity portion and the rear end vicinity portion of the ram 30. An arm lower support shaft 41 extending in the X-axis direction is fixed to the front end side bracket 38. The other end of the front arm 35 described above is connected to the front end bracket 38 so as to be rotatable around the arm lower support shaft 41 by inserting the arm lower support shaft 41 into the circular hole 35b. An arm lower support shaft 42 extending in the X-axis direction is fixed to the rear end side bracket 39. The other end of the rear arm 36 described above is connected to the rear end bracket 39 so as to be rotatable around the arm lower support shaft 42 by inserting the arm lower support shaft 42 into the circular hole 36b. There is. A stopper 38a and a rear end side bracket 39a are fixed to the inside of each of the front end side bracket 38 and the rear end side bracket 39, that is, on the central side of the ram 30, by welding or the like.

Next, a structure for assembling the base portion 33 and the arm connecting portion 34 will be described. A spacer 46 extending in the horizontal direction is arranged between the lower surface of the bracket 34a constituting the arm connecting portion 34 and the upper surface of the base portion 33. The spacer 46 and the bracket 34a are provided with a plurality of circular holes (not shown) through which the bracket fixing bolt 47 is inserted. The plurality of bracket fixing bolts 47 are passed through the circular holes from the upper side of the bracket 34a, and the bolt portions formed at the tip portions are screwed and fastened to the screw holes 33a of the base portion 33. As a result, the arm connecting portion 34 is supported on the base portion 33 via the spacer 46 in a state where it does not move in the horizontal direction but can move in the vertical direction. Further, the base portion 33 is provided with a plurality of screw holes 33b on the outer side (end side of the ram 30) of the screw holes 33a. Jack-up bolts 48 arranged so that the head is in contact with the lower surface of the bracket 34a are screwed into the screw holes 33b.

The head of the jack-up bolt 48 is formed thinner than the spacer 46. Initially, the plurality of jack-up bolts 48 are screwed as deep as possible into the screw holes 33b, that is, the lower surface of the head is in contact with the upper surface of the base 33. In this state, the plurality of jack-up bolts 48 are rotated in the loosening direction and evenly screwed upward. As a result, the plurality of jack-up bolts 48 push up the bracket 34a upward to form a space between the lower surface of the bracket 34a and the upper surface of the base 33.

Here, when the arm connecting portion 34 is at a predetermined height position, it is assumed that the required appropriate tension is applied to the front arm 35 and the rear arm 36, respectively. Therefore, when the arm connecting portion 34 is pushed up to a position higher than the predetermined height position, a spacer 46 manufactured in advance with a predetermined thickness according to the predetermined height is attached to the lower surface of the bracket 34a. It is inserted into the space formed between it and the upper surface of the base 33. Then, the plurality of jack-up bolts 48 are tightened again to the initial state where the lower surface of the head is in contact with the upper surface of the base 33, and after the lower surface of the bracket 34a is in contact with the upper surface of the base 33, the plurality of bracket fixing bolts 47 are fastened. The arm connecting portion 34 is completely fixed. As is clear from the above description, the plurality of jack-up bolts 48 and the base 33 have a first tension applying means for applying the tension to the front arm 35 and a second tension applying the tension to the rear arm 36. It constitutes a tension applying means.

The first tension applying means for applying tension to the front arm 35 and the second tension applying means for applying tension to the rear arm 36 are not limited to the above-mentioned configurations, but are configured separately from each other. It doesn't matter.

As described above, the ram 30 made of cast iron is suspended and supported by the steel arm suspension member 32, the front arm 35 and the rear arm 36, and the ram 30 connected to the arms 35 and 36 is connected to the ram 30. By applying a tension that acts to pull up the portion, it is possible to prevent the portion near the front end and the rear end of the ram 30 from being deformed so as to bend downward. In particular, in the present embodiment, as shown in FIG. 2, the ram 30 can take a position where the saddle 14 is largely overhanged. Under this state, the portion near the front end of the ram 30 is likely to undergo the above deformation, and being able to prevent this deformation is very effective in improving the accuracy of electric discharge machining. Further, since the machine tool 1 of the present embodiment is not configured so that the ram 30 itself has particularly high rigidity, it can be configured to be compact and lightweight. In particular, by arranging the position of the arm lower support shaft 41 provided near the front end of the ram 30 as high as possible, not only the amount of deformation of the ram 30 is reduced, but also the front end side of the ram 30 is more inclined. The ram 30 can be pulled up so as to be in a state close to horizontal, the inclination of the electric discharge machining head 31 can be reduced, and the machining accuracy can be further improved.

In order to prevent the deformation of the ram 30, it is conceivable that the ram 30 itself is configured to have high rigidity. However, if this is done, the ram 30 is more likely to be deformed due to its own weight increase, and it becomes necessary to take further measures to prevent deformation. As a result, the ram 30 and the machine tool 1 are further increased in size and weight. In particular, since the machine tool 1 of the present embodiment moves the electric discharge machining head 31 in the three axial directions of X, Y and Z, when the ram 30 becomes heavier, the positioning accuracy of the movement, that is, the accuracy of the electric discharge machining It becomes disadvantageous in keeping high.

Further, in the present embodiment, the front arm 35 and the rear arm 36 are made of a steel material having a Young's modulus larger than that of the cast iron constituting the ram 30. By the way, for example, the Young's modulus of gray cast iron and rolled steel (SS400) is 100 and 206 (GPa), respectively. Constructing both arms 35 and 36 from such materials would be advantageous in making these arms 35 and 36 lighter and more rigid to prevent deformation of the ram 30.

Next, the rotating member 50 and the structure around the rotating member 50 will be described in detail. One rotating member 50 formed in a plate shape is arranged on the left and right sides of the ram 30 on the outside, that is, on the + X side and the −X side, respectively. As shown in FIG. 4, each rotating member 50 has circular shaft holes 50a and 50b. On the other hand, columnar shafts 51 and 52 extending in the X-axis direction are fixed to the ram 30. The rotating member 50 is combined with the ram 30 by inserting the shafts 51 and 52 into the shaft holes 50a and 50b in a loosely fitted state, respectively.

On the saddle 14 at a position corresponding to the outer left and right sides of each rotating member 50, a set of a bearing portion 60 for driving a balance weight 65, which will be described later, and a pulley 61 mounted on the bearing portion 60 are arranged in the Y-axis direction. They are arranged at intervals from each other. An endless belt 62 is wound around the two pulleys 61. In this way, between the two pulleys 61, the two portions of one endless belt 62 extend apart from each other in the X-axis direction. Of these two parts, the part closer to the rotating member 50 is connected to the rotating member 50 via the first connecting portion 63, and the part farther from the rotating member 50 is passed through the second connecting portion 64. It is connected to the balance weight 65.

The balance weight 65 is arranged on the outer side of each rotating member 50. Although the balance weight 65 is cut and shown in the horizontal plane (XY plane) in FIG. 1, it is not hatched in order to avoid complication of the drawing. The two balance weights 65 are connected and integrated by a connecting member 66 bridged above each. A rail 55 is fixed to the upper surface of each rotating member 50, and each balance weight 65 is mounted on the rail 55, that is, on the rotating member 50 so that the balance weight 65 can travel along the rail 55. There is. That is, the upper portion of each balance weight 65 is bent so as to be slightly toward the rotating member 50 side, and the linear guide 67 attached to the lower surface of the upper portion is engaged with the rail 55 from above. Further, each balance weight 65 is rotatably held around a vertical rotation axis by a wheel 68 made of rubber or the like that contacts the rotation member 50 from the outside. These wheels 68 define the position of the balance weight 65 in the X-axis direction.

As described above, the Y-axis position of the ram 30 with respect to the saddle 14 (that is, with respect to the column) corresponds to the change of the electric discharge machining position in the workpiece 23 as shown in FIGS. 2, 5 and 6. When changed to, the movement of the ram 30 is transmitted to the endless belt 62 via the rotating member 50 and the first connecting portion 63, and the endless belt 62 rotates. The rotation of the endless belt 62 is transmitted to the balance weight 65 via the second connecting portion 64, and the balance weight 65 moves in the Y-axis direction. In the endless belt 62, the portion where the first connecting portion 63 is connected and the portion where the second connecting portion 64 is connected move in opposite directions with respect to the Y-axis direction. Therefore, as the position of the ram 30 in the Y-axis direction moves in the −Y direction as shown in FIGS. 2, 5 and 6, the balance weight 65 sequentially moves in the + Y direction.

That is, the balance weight 65 moves further backward as the ram 30 moves further forward (+ Y direction) with respect to the column. The bearing portion 60, the pulley 61, the endless belt 62, the first connecting portion 63 and the second connecting portion 64 constitute a balance weight driving means for moving the balance weight 65 as described above. As the amount of overhang in which the ram 30 protrudes forward from the column increases, the ram 30 holding the heavy electric discharge machining head 31 at the front end is likely to be deformed so that the front end bends downward.

However, here, when the balance weight 65 resting on the rail 55 moves as described above according to the position of the ram 30, the balance weight 65 is the rear end of the ram 30 rather than the shaft 51. When it is positioned on the side (-Y side), a moment that tends to rotate the rotating member 50 clockwise in FIG. 2 acts around the axis 51. And this moment becomes larger as the amount of the overhang of the ram 30 increases. When this moment acts on the rotating member 50, the front end portion of the rotating member 50 applies an upward force to the ram 30 via the shaft hole 50b and the shaft 52. As a result, the front end portion of the ram 30 is pulled up to prevent the front end portion from being deformed so as to bend downward, and thus the electric discharge machining head 31 is prevented from being tilted from the Z axis and the machining accuracy is prevented from deteriorating.

Further, from a point other than the above moment, even if an overhang of the ram 30 occurs, the deformation of the ram 30 can be suppressed to be smaller. This point will be described in detail below. 2, 5 and 6, respectively, show the balance weight 65 and the associated linear guide 67 and wheels 68 from the X-axis moving body (that is, the structure above the linear guide 16) loading the rail 15, respectively. The Y-axis direction center of gravity position of the structure excluding the connecting member 66 is indicated by the one-point chain line C1, and the Y-axis direction center of gravity position of the X-axis direction moving body is indicated by the one-point chain line C2.

As can be seen from the comparison of the two center of gravity positions, the moving balance weight 65 and the connecting member 66 are provided, so that the center of gravity position of the moving body in the X-axis direction is separated in the Y-axis direction as compared with the case where they are not provided. It is located closer to the center of the two moving body support positions (between the two rails 17). If this is the case, when the ram 30 is overhanged, the load applied to the portion outside the two moving body support positions is reduced, so that the deformation of the ram 30 is more reliably prevented.

In order to reduce the load applied to the portion outside the two moving body support positions when the ram 30 is overhanged, the width of the bed 12, that is, the dimension in the Y-axis direction is increased to support the two moving bodies. It is desirable to set the position spacing larger. However, if the center of gravity of the moving body in the X-axis direction is located closer to the center of the two moving body support positions separated in the Y-axis direction as described above, the width of the bed 12 can be set smaller. Therefore, it is advantageous in reducing the size and weight of the machine tool 1.

Here, the preferable weight of the balance weight 65 will be considered. The weight of the moving body in the Y-axis direction excluding the balance weight 65 is W1, and the weight of the balance weight 65 is W2. Here, the linear guide 67 and the wheels 68 attached to the balance weight 65, and the connecting member 66 are not considered. In order to prevent the center of gravity from moving forward and tilting the ram 30 by giving a counterbalance to the moving ram 30, at least the sum of the weight W1 and the weight W2 is calculated. It is clear that the position of the entire center of gravity including the balance weight 65 and the moving body in the Y-axis direction must be located behind the position of the linear guide 18 arranged on the front side. At this time, the weight W2 of the balance weight to be applied is preferably as small as possible so as not to unnecessarily increase the weight of the entire moving body, and on the other hand, it must be large enough to impart balance. is there. From this, it can be said that it is sufficient for the weight W2 to be about one-fourth to one-half of the weight W1 when the weight W1 is set to "1" in relative ratio to the weight W2.

Next, the second embodiment of the present invention will be described. 9, 10 and 11, respectively, show the planar shape, the side surface shape, and the partial front shape of the machine tool 2 according to the second embodiment of the present invention. In addition, in these FIGS. 9 to 11, the elements equivalent to those in FIGS. 1 to 3 described above are given the same number, and the description thereof will be omitted unless otherwise specified (the description thereof). The same applies below). Note that FIG. 11 shows a part of the machine tool 2 as viewed from the portion along the line AA shown in FIG.

The machine tool 2 of the present embodiment is also an electric discharge machine as an example, but in comparison with the machine tool 1 of the first embodiment, a ram suspension mechanism including an arm suspension member 32, a front arm 35, a rear arm 36, and the like. There is basically no difference in that one rotating member 250 is used instead of the two rotating members 50, and that the mechanism for moving the balance weight is vertical. doing.

The one rotating member 250 is a member extending in the Y-axis direction, and is arranged at a central position in the width direction, that is, in the X-axis direction with respect to the ram 30. FIG. 12 shows the ram 30 and the rotating member 250 in an exploded manner, and will be described below with reference to FIG. The rotating member 250 has circular shaft holes 250a and 250b. On the other hand, columnar shafts 51 and 52 extending in the X-axis direction are fixed to the ram 30. That is, after the shafts 51 and 52 are loosely fitted into the shaft holes 250a and 250b of the rotating member 250, the shafts 51 and 52 are fixed to the ram 30, and the rotating member 250 is combined with the ram 30. ..

A rail 55 extending in the length direction, that is, the Y-axis direction is fixed to the upper surface of the rotating member 250. The balance weight 265 has a roof-shaped upper portion, and is engaged with the rail 55 via a linear guide 67 fixed to the lower surface of the uppermost portion. In this way, the balance weight 265 is mounted on the rail 55, that is, on the rotating member 250, and is movable along the rail 55. Further, in the balance weight 265, wheels 68 made of rubber or the like that are in contact with the ram 30 from the outer left side and the outer right side of the ram 30 are rotatably held about a vertical rotation axis. These wheels 68 define the position of the balance weight 265 in the X-axis direction.

Two bearing portions 60 are arranged on the saddle 14 at positions corresponding to the outer left side and the outer right side of the ram 30. The two bearing portions 60 are arranged so as to be spaced apart from each other in the Y-axis direction both on the left outer side and the right side outer side of the ram 30. A pulley 61 is supported in each bearing portion 60 so as to be rotatable around a rotating shaft extending in a direction parallel to the X axis.

An endless belt 62 is wound around the two pulleys 61 supported in this way. In this way, between the two pulleys 61, the two portions of one endless belt 62 extend in the vertical direction, that is, in the Z-axis direction. The lower portion of the two belt portions is connected to the ram 30 via the first connecting portion 63, and the upper portion is connected to the balance weight 265 via the second connecting portion 64.

Also in the machine tool 2 of the present embodiment having the above configuration, the Y-axis direction position of the ram 30 with respect to the saddle 14 (that is, with respect to the column) corresponds to the change of the electric discharge machining position in the workpiece 23. 10. As shown in FIGS. 13 and 14, when the balance weight 265 is moved in the −Y direction, the balance weight 265 is sequentially moved in the + Y direction. That is, also in this embodiment, the balance weight 265 moves further backward as the ram 30 moves more forward (+ Y direction) with respect to the column.

In the side view of FIG. 10, the position where the ram 30 protrudes most forward (in the + Y direction) with respect to the saddle 14, that is, the position where the overhang amount is maximum is shown. The relative position of the ram 30 with respect to the saddle 14 is a position where the overhang amount is medium, a position where the overhang amount is minimum, and the like corresponding to changing the position of electric discharge machining on the workpiece 23. It can be taken. 13 and 14, respectively, show the side shape when the ram 30 takes those positions. In addition, FIG. 10, FIG. 13 and FIG. 14 show the position of the center of gravity in the Y-axis direction of the structure in which the balance weight 265 and the linear guide 67 and the wheels 68 associated therewith are removed from the moving body in the X-axis direction applying the load to the rail 15. The one-point chain line C1 and the position of the center of gravity of the moving body in the X-axis direction in the Y-axis direction are indicated by the one-point chain line C2.

By moving the balance weight 265 as described above, also in the present embodiment, when the balance weight 265 is positioned on the rear end side (−Y side) of the ram 30 with respect to the shaft 51, the rotating member 250 is moved to the shaft 51. A moment that tries to rotate clockwise in FIG. 10 acts around it. And this moment becomes larger as the amount of the overhang of the ram 30 increases. When this moment acts on the rotating member 250, the front end portion of the rotating member 250 applies an upward force to the ram 30 via the shaft hole 250b and the shaft 52. As a result, the front end portion of the ram 30 is pulled up to prevent the front end portion from being deformed so as to bend downward, and thus the electric discharge machining head 31 is prevented from tilting from the Z axis and deteriorating the machining accuracy.

If the action of lifting the front end side of the ram 30 in the second embodiment is compared to the principle of leverage, the horizontal shaft 51 at the center where the rotating member 250 rotates corresponds to the fulcrum of the lever. Therefore, when the distance from the shaft 51 to the shaft 52 is α, the distance from the shaft 51 to the center of the balance weight 265 is β, and the mass of the balance weight is W3, the force for lifting the front end side of the ram 30 is It is (β / α) × W3, and it is clear that the force is not applied unless the center of the balance weight 265 is always located behind the ram 30 with respect to the shaft 51. Therefore, in the second embodiment, in order to lift the front end of the ram 30 more effectively, it is desirable that α <β when the ram 30 advances most, and the ratio of α to β is 1: 1 to 1. It is desirable that the relationship is about 2 to 2. It is also desirable that the position of the shaft 51 be closer to the center of the ram 30 and closer to the bearing on the front side of the linear guide 18 when the ram 30 is most advanced.

Further, by moving the balance weight 265 as described above, as in the case of the first embodiment in the present embodiment, the position of the center of gravity of the moving body in the X-axis direction (the above-mentioned alternate long and short dash line) as compared with the case without the balance weight 265. (See C2) will be located at two moving body support positions separated in the Y-axis direction, that is, on the more central side between the two rails 17. If this is the case, when the ram 30 is overhanged, the load applied to the portion outside the two moving body support positions is reduced, so that the deformation of the ram 30 is more reliably prevented.

As described above, in a machine tool having no ram suspension mechanism including an arm suspension member 32, a front arm 35, a rear arm 36, etc., one rotating member 250 is used, and a vertical mechanism for moving a balance weight. Although the second embodiment in which the above is used has been described, the configuration using one rotating member 250 and the vertical mechanism for moving the balance weight is similarly applied to the machine tool having the ram suspension mechanism. Applicable.

It is desirable that the rotating member 50 in the first embodiment is made of a material having a Young's modulus larger than that of the material constituting the ram 30. Examples of such a combination of materials include a combination of rolled steel (SS400) and gray cast iron exemplified as the materials of both arms 35 and 36 and the ram 30 in the first embodiment. If the rotating member 50 and the ram 30 are made of such a material, the rotating member 50 is made lighter and more rigid, which is advantageous in preventing the ram 30 from being deformed. Further, in the case of the second embodiment, since the structure is such that the ram 30 is pulled up by the principle of leverage while giving the counter balance by moving the balance weight, the rotating member 250 is required to have high rigidity. However, there is an advantage that a lightweight material such as carbon fiber reinforced plastic (CFRP) can be used as the material of the rotating member 250, for example.

Further, although the machine tools of the two embodiments described above are both electric discharge machines, the present invention is not limited to the electric discharge machine, and the tool is held at the front end portion which is one end portion in the length direction of the ram. It is applicable to any machine tool configured to move this ram back and forth with respect to the bed.

1, 2 Machine tool 10 Base 12 Bed 13 Slider 14 Column 15, 17 Rail 16, 18 Linear guide 21 Processing tank 22 Processing liquid 23 Work piece 30 Ram 31 Electric discharge machining head 32 Arm suspension member 33 Arm suspension member base 34 Arm connecting part of arm suspension member 35 Front arm 36 Rear arm 38 Front end bracket 39 Rear end bracket 41, 42 Arm lower support shaft 44, 45 Arm upper support shaft 46 Spacer 47 Bracket fixing bolt 48 Jack-up bolt 51 , 52 Shaft 50, 250 Rotating member 60 Bearing part 61 Pulley 62 Endless belt 63 First connecting part 64 Second connecting part 65, 265 Balance weight 66 Connecting member

Claims (4)

A ram that supports the tool at the front end, which is one end in the length direction,
A column that supports the ram so that it can move in the front-rear direction with its length extending substantially horizontally, and
A ram driving means for moving the ram in the front-rear direction and
In machine tools that have
It is composed of a member arranged so as to extend along the length direction of the ram, and is supported by the ram so as to be rotatable around a substantially horizontal axis set at a predetermined position of the member and the ram. Also on the front side, a rotating member that connects to a part of the ram so that an upward force due to the rotation can be transmitted.
A balance weight mounted on the rotating member so as to be movable in the front-rear direction,
A balance weight driving means that moves the balance weight more rearward as the ram moves more forward with respect to the column.
Machine tools with. The structure in which the rotating member is rotatably supported by the ram is a structure in which a shaft body held by the other is inserted into a hole formed in one of the ram and the rotating member.
The machine tool according to claim 1. The structure in which the upward force due to the rotation is transmitably connected to a part of the ram is a structure in which the shaft body held in the other is inserted into the hole formed in one of the ram and the rotating member. ,
The machine tool according to claim 1 or 2. At an intermediate position in the length direction of the ram, an arm suspension member fixed in an upwardly standing state and
One end is connected to the arm suspension member, and the other end is connected to a portion near the front end of the ram below the front side of the connection position.
A first tension applying means that applies a tension that acts to pull up a portion of the ram that is connected to the front arm.
A rear arm in which one end is connected to the arm suspension member and the other end is connected to a portion near the rear end of the ram below the rear side of the connection position.
A second tension applying means that applies a tension that acts to pull up the portion of the ram that is connected to the rear arm.
The machine tool according to any one of claims 1 to 3.