JP3950306B2 - Ball screw device and injection molding machine equipped with the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ball screw nut support device that converts rotational motion into linear motion, or conversely, a ball screw nut support device that converts linear motion into rotational motion, and an injection molding machine incorporating the ball screw nut support device, More particularly, the present invention relates to a support structure for a plurality of ball screw nuts that share and support a load in one side of a ball screw used for linear drive such as injection, mold opening / closing, mold clamping, and ejector of an electric injection molding machine.
[0002]
[Prior art]
In the past, hydraulic pressure was mainly used as the drive source for the linear movement axis of injection molding machines. Recently, however, it has the advantages of improving the working environment, improving power energy efficiency, and easily controlling the speed and position of the operating part. The type drive is often used, and the linear servo drive and the most mechanically efficient ball screw structure that changes the rotation of the motor to the linear drive are used.
[0003]
In the injection drive of an injection molding machine, when the molten resin stored at the tip of the injection screw is pushed forward into the mold cavity by advancing the injection screw, the injection screw requires a large pressing force. When a ball screw is used, one side direction of the linear reciprocating drive by the ball screw becomes a high load, and the allowable maximum load force of the ball screw is selected so as to correspond to the pressing force at the time of the injection drive. In addition, the load force of the ball screw is calculated by the rolling pressure resistance of the ball sandwiched between the screw groove and the ball screw nut groove, and the design load capacity is equal to the action ball on the action spiral of the screw. Calculated as to
[0004]
When a ball screw is used for the injection drive of a small injection molding machine, even if a ball screw having a load capacity corresponding to the driving force of the ball screw or a size exceeding the load capacity is selected, a commercially available standard The cost of the ball screw device is not a problem because it can be selected from the size, but if the injection pressure increases with an injection molding machine of medium size or larger, the size of the ball screw will deviate from the standard, so the cost will become a big problem and the limit design will be Required.
[0005]
When a high tensile force is applied in the axial direction of the ball screw shaft, the ball screw shaft extends between the bearing on the fixed side and the ball screw nut, and the ball screw nut also expands and contracts by receiving the axial force. The screw pitch between the screw side of the screw and the ball screw nut side shifts, and the ball receiving pressure changes depending on the position in the axial direction.
[0006]
FIG. 9 shows a conventional ball screw device disclosed in Japanese Patent Laid-Open No. 2000-108175. In the configuration of this ball screw device, the ball screw shaft 010 is driven and rotated on the left fixed side (not shown), and the axial direction of the ball screw shaft 010 is constrained by a strong thrust bearing. As a result, the moving frame 06 coupled to the injection screw is pushed by the ball screw nut 011 and moves in the injection direction indicated by the arrow. Reference numeral 59 denotes a flange-shaped pressure detection sensor (load cell). In the configuration of this ball screw device, as shown in the schematic diagram (I) of FIG. 10 and the characteristic graph (II) of the load with respect to the axial nut width, the ball at the working end of the ball screw nut 011 has a pressure receiving load of the ball. Becomes larger. Even if the length of the ball screw nut 011 is increased in order to increase the capacity of the ball screw 050, the end of the ball screw nut 011 is greatly deformed, and thus the load on the working end side tends to increase more and more. . Reference numeral 04 denotes a fixed-side member that rotatably supports the ball screw shaft 010 with a bearing.
[0007]
As shown in FIG. 11, a ball screw device for injection driving of an injection molding machine disclosed in Japanese Patent Application Laid-Open No. 2000-185339 has a ball screw nut 052 that is fitted to a ball screw shaft 051 driven by an electric motor. , 053 are arranged in series on one ball screw shaft, and fluid pressure cylinders 054, 055 for transmitting thrust from the ball screw nuts 052, 053 to the movable member 060 of the electric injection molding machine are respectively ball screw nuts. Are connected to each other, and the cylinder chambers of the fluid pressure cylinders 054 and 055 are communicated with each other by a communication pipe 056, and the load applied to the ball screw shaft is evenly distributed by a plurality of ball screw nuts. Thus, the life of the ball screw shaft is extended.
[0008]
[Problems to be solved by the invention]
As described in the above conventional example, if the length of the ball screw nut is increased in order to obtain a high load ball screw nut, the deformation at the end of the nut is large, so that the load on the working end side is large. Tends to increase more and more. In addition, a plurality of ball screw nuts are screwed in series with the ball screw shaft, the action body and each ball screw nut are connected by a fluid pressure cylinder, and the cylinder chamber of each fluid pressure cylinder is communicated by a communication pipe. The ball screw device with the configuration can equally share the load applied to the nut, but the fluid leaks from the hydraulic cylinder or the position of the ball screw nut fluctuates due to oil compression by the pipe volume, and the injection The screw may not be able to keep the correct injection start or injection end position. An object of the present invention is to provide a ball screw device in which a plurality of ball screw nuts can share a heavy load of a ball screw shaft without changing a mounting position of the ball screw nut with respect to an action body.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the present invention solves the problem by means characterized by the constitution of the following items.
[0010]
(1) Instead of linear movement of a ball screw nut that rotates and drives a ball screw shaft that restrains the thrust direction to a fixed member and is screwed to the ball screw, the acting body coupled to the ball screw nut is moved in one direction. In a ball screw device having a load configuration in which the load load is significantly larger than the load load in the opposite direction,
A first ball screw nut provided on the front side of the working body such that a mounting flange is located on the opposite side of the heavy load direction of the ball screw shaft;
A hydraulic cylinder fixed to the working body;
A hydraulic piston fitted inside the hydraulic cylinder in a fluid-tight manner and attached to a first ball screw nut;
A hydraulic pressure source for applying a predetermined hydraulic pressure to a ring-shaped hydraulic chamber formed by the hydraulic piston and the hydraulic cylinder;
With mounting flange and a second ball screw nuts fixedly attached to the rear side of the working body so as to be positioned on the opposite side with respect to the heavy load direction of the ball screw shaft,
The hydraulic cylinder and the hydraulic piston, holds filled with hydraulic oil at a predetermined pressure to the ring-shaped hydraulic chamber, so as to apply a preload force of a predetermined ratio at all times the maximum load to the working body, the ball screw together with the shaft is pulled in the first direction opposite the heavy load direction by the ball screw nut, said at maximum load the first and second ball screw nut are configured so as to share the maximum load of the ball screw shaft A ball screw device characterized by the above.
[0011]
(2) Instead of linear movement of the ball screw nut that rotates and drives the ball screw shaft that restrains the thrust direction to the fixed member and engages with the ball screw, the action body coupled to the ball screw nut moves in one direction. In a ball screw device having a load configuration in which the load load is significantly larger than the load load in the opposite direction,
A first ball screw nut provided on the front side of the working body such that a mounting flange is located on the opposite side of the heavy load direction of the ball screw shaft;
A hydraulic cylinder fixed to the working body;
A hydraulic piston fitted inside the hydraulic cylinder in a fluid-tight manner and attached to a first ball screw nut;
A hydraulic pressure source for applying a predetermined hydraulic pressure to a ring-shaped hydraulic chamber formed by the hydraulic piston and the hydraulic cylinder;
With mounting flange and a second ball screw nuts fixedly attached to the rear side of the working body so as to be positioned on the opposite side with respect to the heavy load direction of the ball screw shaft,
The hydraulic cylinder and the hydraulic piston, holds filled with hydraulic oil at a predetermined pressure to the ring-shaped hydraulic chamber, so as to add 40-50% of the preload force constantly maximum load to the working body, wherein with the ball screw shaft is pulled in the first by a ball screw nut and the heavy load direction opposite direction, is configured to the at full load the first and second ball screw nut to share the maximum load of the ball screw shaft ball screw device, characterized in that there.
[0012]
(3) Instead of linear movement of the ball screw nut that rotates and drives the ball screw shaft that restrains the thrust direction to the fixed member and is screwed to the ball screw, the action body coupled to the ball screw nut is moved in one direction. In a ball screw device having a load configuration in which the load load is significantly larger than the load load in the opposite direction,
A first ball screw nut provided on the front side of the working body such that a mounting flange is located on the opposite side of the heavy load direction of the ball screw shaft;
An elastic body sandwiched between the working body and an annular plate attached to the first ball screw nut;
With mounting flange and a second ball screw nuts fixedly attached to the rear side of the working body so as to be positioned on the opposite side with respect to the heavy load direction of the ball screw shaft,
Elastic body is mounted in a state where the compressive force is preloaded to a predetermined percentage of the maximum load, the pulled in the opposite direction to the heavy load direction by the ball screw shaft is the first ball screw nut, the maximum load ball screw device, characterized in that during the first and second ball screw nut are configured so as to share the maximum load of the ball screw shaft.
[0013]
(4) Instead of linear movement of the ball screw nut that rotates and drives the ball screw shaft that restrains the thrust direction to the fixed member and is screwed to the ball screw, the action body coupled to the ball screw nut is moved in one direction. In a ball screw device having a load configuration in which the load load is significantly larger than the load load in the opposite direction,
A first ball screw nut provided on the front side of the working body such that a mounting flange is located on the opposite side of the heavy load direction of the ball screw shaft;
An elastic body sandwiched between the working body and an annular plate attached to the first ball screw nut;
With mounting flange and a second ball screw nuts fixedly attached to the rear side of the working body so as to be positioned on the opposite side with respect to the heavy load direction of the ball screw shaft,
Elastic body, the compression force is attached in a state of pre-load such that 40-50% of the maximum load, the pulled in the opposite direction to the heavy load direction by the ball screw shaft is the first ball screw nut, ball screw device, characterized in that said at maximum load the first and second ball screw nut are configured so as to share the maximum load of the ball screw shaft.
[0014]
(5) In the ball screw device of the above (2), a load sensor is attached to a member that receives the load of the ball screw shaft, and a control valve for controlling the pressure oil to the ring-shaped hydraulic chamber is provided by a detection value of the sensor. When the detected value is 1/2 (50%) or more of the maximum load, the hydraulic chamber is filled and held with a predetermined pressure of pressure to apply a load of 40 to 50% of the maximum load to the working body. ball screw device, characterized in that said at maximum load the first and second ball screw nut share the maximum load of the ball screw shaft in the.
[0015]
(6) A plurality of ball screw devices including a plurality of load sharing type nuts as described in any one of (1) to (5) above are used to drive a linear injection drive of an injection screw of an injection molding machine. An injection molding machine characterized in that all ball screw nuts can share the load.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
[First Embodiment]
A first embodiment of the present invention will be described with reference to the drawings. 1 is a side sectional view showing the configuration of the ball screw device, FIG. 2 is an overall side view of an injection unit using the ball screw device of FIG. 1, and FIG. 3 is a plan view of the injection unit of FIG. 4) and a hydraulic system diagram of the ball screw device, FIG. 4 is a graph showing the load load of two ball screw nuts with respect to the load of the ball screw shaft of the ball screw device of FIG. 1, and FIG. 5 is a schematic diagram of the ball screw device of FIG. FIG. 2 is a graph (II) and a graph (II) showing the load that the ball receives in the axial direction of the ball screw nut.
[0017]
A ball screw device 20 shown in FIG. 1 includes a ball screw shaft 21, two sets of (first) ball screw nuts 22A, (second) ball screw nuts 22B, and ball screw nuts. A hydraulic cylinder 35, a hydraulic piston 36, a spacer 37 that fixedly couples the hydraulic cylinder 35 to the moving frame 6, and a hydraulic cylinder 35 that moves between the moving frame 6 and the moving frame 6 when mounting 22A. 6 and a plurality of bolts 38 to be attached to 6 and an attachment disk 34 to attach the ball screw nut 22B to the moving frame 6. The hydraulic piston 36 is slidably fitted in the hydraulic cylinder 35 in a fluid-tight manner, and a hydraulic pipe 44 </ b> A is coupled to a hydraulic chamber r formed by the hydraulic piston 36 and the hydraulic cylinder 35. A part of the bolt 38 also serves as a detent for the ball screw nut 22A.
[0018]
The load load of the two ball screw nuts 22A and 22B with respect to the change in the load of the ball screw shaft 21 will be described with reference to the graph showing the load load of the two ball screw nuts in FIG. 4, the horizontal axis represents the load on the ball screw shaft 21, and the vertical axis represents the load on the ball screw nut 22A (the straight line A in the figure) and the ball screw nut 22B (the oblique straight line B in the figure). When a high pressure is applied to the ring-shaped hydraulic chamber r through the hydraulic piping 44A and a constant load 1 / 2F is applied to the ball screw nut 22A through the hydraulic piston 36 (horizontal straight line A), the ball screw shaft 21 is externally applied. When there is no load (the left end in FIG. 4), the ball screw shaft 21 is pulled with a force 1 / 2F in a direction opposite to the heavy load direction by the ball screw nut 22A. Hydraulic pressure in the reaction force of the hydraulic chambers r (1 / 2F) is transferred from the mounting disk 34 through the working body 6 from the hydraulic cylinder 35 to the ball screw nut 22B, ball Lumpur screw nut 22B heavy load side of the ball screw shaft 21 Pulled in the direction and subjected to compression by the ball screw shaft 21 (−½ F), this force does not act to the outside.
[0019]
Next, when a tensile force 1 / 2F is applied to the ball screw shaft 21 in the direction indicated by the arrow in FIG. 1, the tensile force of the ball screw shaft 21 is borne only by the ball screw nut 22A as shown in the center of FIG. Thus, the force applied to the ball screw nut 22B becomes zero.
Further, when the maximum load F is applied to the ball screw shaft 21 in the direction of the arrow, the ball screw nut 22A and the ball screw nut 22B share the same force 1 / 2F as shown at the right end of FIG. .
In this way, if the ball screw nut 22A is always applied with a pressing force that is ½ of the maximum load, the two ball screw nuts 22A and 22B have the maximum load of the ball screw shaft 21 at the maximum load. Can be shared in half.
[0020]
Also, as shown in FIG. 5 (I), if ball screw nuts 22A and 22B are arranged in series and the load load of ball screw nut 22A and ball screw nut 22B is shared in half, the ball in the axial direction The calculated values of the load received by the ball are as shown in FIGS. 5 (II) and 5- (III), and the areas m and n obtained by integrating the load received by the ball in the axial direction are equal. 5- (II) and FIG. 5- (III) showing the load received by the ball are calculated values of the load received by the ball in the axial direction of the ball screw nut 011 shown in FIG. By comparison, it is apparent that the maximum value of the load received by the balls constituting the ball screw is small.
[0021]
Next, the outline of the injection unit 1 using two sets of the above-described ball screw device 20 and the configuration of the ball screw device 20 and its periphery will be described with reference to FIGS. The injection unit 1 performs resin feeding and plasticization of the injection screw 7 by driving the electric motor 8, and at the same time, the ball screw device 20 advances straight while synchronously controlling the rotation of two servo motors 11 provided separately. These are converted into motions, and these two rectilinear motions are simultaneously applied to the injection screw 7 to advance and retreat the injection.
[0022]
In the figure, a base portion of an injection cylinder 5 is attached to a side surface of a fixed side frame 4 installed on the drive unit base 3. The moving frame 6 is movable in the injection direction horizontally on the rail 31 laid on the upper surface of the drive unit base 3 via the linear bearing 32. An injection screw rotation drive (resin feed, plasticization) speed reducer 19 is attached to the rear of the moving frame 6, and the speed reducer 19 is driven by a motor 8 attached to the upper part of the moving frame 6.
[0023]
The ball screw shafts 21 and 21 of the ball screw device 20 are rotatable and can handle a large thrust. A large-capacity taper roller bearing 18 and a ball bearing 17 are fixed to the fixed side frame via bearing covers 60 and 61. 4 is attached. A pair of servo motors 11 and 11 for injection driving are attached to the lower part of the fixed side frame 4, and a small pulley 12 is attached to the output shaft of each servo motor 11 with its rotational direction being restrained. The driving force is transmitted by the toothed belt 14 to the large pulley 13 fixed to the pair of ball screw shafts 21, 21. Further, another pulley having the same diameter is fixed to the output shaft of each servo motor 11, and another toothed belt is hung on the pulley having the same diameter to rotate the output shafts of both servo motors 11 synchronously. .
[0024]
The hydraulic oil pressure-fed to the hydraulic chamber r surrounded by the hydraulic piston 36 and the hydraulic cylinder 35 attached to the ball screw nut 22A is pressurized oil sent from the hydraulic pump 41 with a small oil-feed amount rotated by the motor 42. Is adjusted to a predetermined pressure by a hydraulic pressure adjusting valve 43 and sent by hydraulic pipes 44A and 44B.
The ball screw nut 22A has a constant preload load, the ball screw nut 22B has the same load value, and a negative (compressed) load is applied. When the load is generated and becomes a positive (tensile) load, the ball screw shaft 21, the ball moves between the screw shaft grooves and the ball deformation due to the load, but all the components constituting the ball screw have high rigidity, and the moving distance due to the fluctuation of the load is small. The length of the chamber r may be very small. Therefore, the clearance e (see FIG. 1) between the hydraulic piston 36 and the spacer 37 may be small.
[0025]
The operation of the ball screw device 20 of the injection unit 1 having the above-described configuration will be described.
In the resin feeding and plasticizing process (at the position indicated by the solid line in FIG. 3), the motor 8 is rotated and the injection screw 7 is rotated, the resin pellets are introduced from the hopper 9 and heated while being fed, and the resin is melt plasticized. Turn into. At the same time, the two injection drive motors 11 are operated slowly and synchronously to move the moving frame 6 backward, the injection screw 7 is slowly retracted, and the molten resin is accumulated at the tip of the injection screw 7.
When one shot of resin has been accumulated in the mold (the moving frame 6 moves to the position indicated by the two-dot chain line in FIG. 3), the injection screw rotating motor 8 is stopped and the injection drive servo is stopped. The motor 11 is rotated at a high speed in a synchronous operation, and the injection screw 7 is moved at a high speed to inject the resin into the cavity of the mold (return to the solid line position in FIG. 3). The process proceeds to the resin feeding and plasticizing process for the next cycle, and the same process is repeated.
[0026]
In the injection process that requires a large force, the ball screw shaft 21 is configured to be on the pulling side, so the ball screw shaft 21 is not likely to be bent (if the ball screw shaft 21 is on the compression side). Unstable bending-buckling (buckling deformation) is likely to occur). Further, since the operating force in the return direction of the moving frame 6 is smaller than the operating force at the time of injection, the moving frame 6 can be stably operated even if the rear end portion of the ball screw shaft 21 does not have a bearing support.
Since one of the ball screw nuts of each ball screw shaft is attached to the working body via a fixing flange, and a preload is always applied between the ball screw nut and the working body, it moves. When the frame 6 returns to the original position, the reproducibility of the position of the ball screw nut 22 relative to the ball screw shaft 21 can be ensured.
Further, the oil chamber r of the hydraulic cylinder 35 to which the ball screw nut 22A is attached can cover an attachment angle error between the ball screw shaft 21 and the ball screw nut 22A.
[0027]
In this way, each of the two ball screw nuts 22A and 22A of the two sets of ball screw nuts arranged in series with the ball screw shaft 21 of the two sets of ball screw devices 20 is subjected to a certain preload by hydraulic pressure. With a simple configuration of placing, the load load of the ball screw nut can be shared when the load load is maximum.
[0028]
[Second Embodiment]
The second embodiment of the present invention is elastic between the ball screw nut on one side and the action body (moving frame 6) instead of the function of preloading the ball screw nut on one side with hydraulic pressure in the first embodiment. A body is interposed, and the elastic body is preloaded so as to have the same function as that of the first embodiment. Hereinafter, the configuration and function will be described with reference to a side sectional view of the ball screw device of FIG.
[0029]
The ball screw device 30 includes a ball screw shaft 21, a ball screw nut 22 </ b> A that is screwed to the ball screw shaft 21, a ball screw nut 22 </ b> B, a ring-shaped elastic body 51, and a support ring that is attached to the ball screw nut 22 </ b> A and supports the elastic body 51. 52, a cover ring 53 of the elastic body 51, a holding base 54 attached to the moving frame 6, an adjusting screw 55 and a lock nut 56 screwed into the holding base 54, and a free rotation of the ball screw nut 22A implanted in the moving frame 6. A stopper pin 57 for stopping the mounting and a mounting disk 34 for mounting the ball screw nut 22B on the rear side of the moving frame 6.
[0030]
The ball screw shaft 21 of the ball screw device 30, the ball screw nut 22A, and the ball screw nut 22B are matched to each other so that the components are mounted without any gaps. After the components are assembled, the adjusting screw 55 is turned to press the cover ring 53 and elastic body. After compressing 51 until a predetermined compression force is reached, the adjusting screw 55 is locked with a lock nut 56. The ball screw nut 22A and the ball screw nut 22B that are preloaded in this way have the same function as the ball screw device 20 of the first embodiment, and the description thereof will be omitted.
[0031]
[Third Embodiment]
In the third embodiment of the present invention, a bearing cover, which is a member that receives the thrust of the ball screw shaft in the first embodiment, is used as a load sensor, and an electromagnetic valve that turns on and off the pressure oil is controlled by a detection value of the sensor. A control device is added.
7 is a plan view (partially sectional view) of the injection unit, a hydraulic system diagram of the ball screw device, a graph showing the load applied to the ball screw shaft and the load applied to the ball screw nut in FIG. Will be explained.
[0032]
A load sensor (load cell) 62 is mounted on the bearing cover 60 that receives the thrust of the ball screw shaft 21. The output of the load sensor 62, which is a detected value of the load applied to the ball screw shaft 21, is input to the control device 63. As shown in FIG. 8, when the load applied to the ball screw shaft 21 exceeds 1/2 of the maximum load F, the hydraulic pump 41 with a small oil feed amount that is energized by the solenoid 64 a of the solenoid valve 64 and rotated by the motor 42. Is adjusted to a predetermined pressure by the hydraulic pressure adjusting valve 43 and is sent to the hydraulic chamber r surrounded by the hydraulic piston 36 and the hydraulic cylinder 35 by the hydraulic pipes 44A and 44B, and a constant load ( Apply preload).
[0033]
Therefore, the load load of the ball screw nut 22B shares the load reduced by the constant load of the ball screw nut 22A. That is, at the maximum load, the maximum load is shared by half.
When the load applied to the ball screw shaft is ½ or less of the maximum load F, the solenoid 64a of the solenoid valve 64 is switched to non-excitation and the pressure oil in the hydraulic chamber r is drained to the tank through the solenoid valve 64 and the ball screw nut. No load is applied to 22A.
[0034]
The preload described in each of the above embodiments is preferably in the range of 40 to 50% of the maximum load.
[0035]
【The invention's effect】
In the present invention, when the acting body is moved, the mounting flange is positioned on the rear side with respect to the heavy load direction of the ball screw shaft when the load load in one direction of the ball screw device is significantly larger than the load load in the opposite direction movement. The first and second ball screw nuts are screwed together, and the second ball screw nut is fixedly attached to the rear side of the working body, and the first ball screw nut is attached to the front side of the working body with respect to the working body. It is attached via a load means (hydraulic mechanism with a hydraulic cylinder and piston or an elastic body) that always applies a predetermined ratio of the maximum load, and a preload of a predetermined ratio of the maximum load is always applied to the working body. , together with the ball screw shaft is pulled in the direction opposite to the heavy load direction by the first ball screw nut, since the first and second ball screw nuts at maximum load in the configuration which is adapted to share the maximum load No complicated hydraulic control is required, only a simple pressure regulating valve and hydraulic source that generate constant hydraulic pressure, or a simple elastic body and elastic force adjusting mechanism, and a standard size ball screw nut is used. Can be low cost.
[0036]
The life of the ball screw nut on the preload side is determined by applying a preload of 40 to 50% of the maximum load when the load is detected by the load detection sensor and is 1/2 (50%) or more of the maximum load. Can be extended.
[0037]
Further, the fluid pressure support mechanism or the elastic body support mechanism of the ball screw nut can cover the mounting angle error between the ball screw nut and the working body, and the effect of improving the reliability and durability of the ball screw nut is achieved. is there. Also, one of the ball screw nuts of each ball screw shaft is attached to the working body via a fixing flange, and a preload is always applied between the ball screw nut and the working body. When the operating body returns to the original position, the reproducibility of the original position of the ball screw nut with respect to the ball screw shaft can be ensured.
The ball screw device of the present invention is particularly suitable for use in an electric power drive that requires a large pressing force only in one side direction of reciprocation, such as an injection drive.
[Brief description of the drawings]
FIG. 1 is a side sectional view of a ball screw device according to a first embodiment of the present invention.
FIG. 2 is an overall side view of an injection unit that uses the ball screw device of the embodiment of FIG. 1;
3 is a plan view (partially sectional view) of the injection unit of FIG. 2 and a hydraulic system diagram of a ball screw device. FIG.
4 is a graph showing load loads of two ball screw nuts with respect to a load of a ball screw shaft of the ball screw device of FIG. 1;
FIG. 5 is a schematic diagram (I) of the ball screw device of FIG. 1 and graphs (II) and (III) showing the load that the ball receives in the axial direction of the ball screw nut.
FIG. 6 is a side sectional view of a ball screw device according to a second embodiment of the present invention.
FIG. 7 is a plan view (partially sectional view) of an injection unit and a hydraulic system diagram of a ball screw device according to a third embodiment of the present invention.
8 is a graph showing the load applied to the ball screw shaft in FIG. 7 and the load applied to the ball screw nut.
FIG. 9 is a sectional side view showing a conventional ball screw device.
10 is a schematic diagram (I) of the conventional ball screw device of FIG. 9 and a graph (II) showing a load that the ball receives in the axial direction of the ball screw nut.
FIG. 11 is a schematic view showing another configuration of a conventional ball screw device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Injection unit 4 Fixed frame 5 Injection cylinder 6 Moving frame 7 Injection screw 11 Servo motor 20, 30 Ball screw device 21 Ball screw shafts 22, 22A, 22B Ball screw nut 34 Mounting disk 35 Hydraulic cylinder 36 Hydraulic piston 41 Hydraulic pump 43 Hydraulic adjustment valve 51 Elastic body 52 Support ring 53 Cover ring 54 Holding stand 55 Adjustment screw 60 Bearing cover 62 Load sensor 64 Solenoid valve

Claims (6)

Instead of linear movement of the ball screw nut that rotates the ball screw shaft that restrains the thrust direction to the fixed member and is screwed to the ball screw, the load coupled to the ball screw nut is moved in one direction. In a ball screw device having a load configuration in which the load is significantly larger than the load applied in the opposite direction movement,
A first ball screw nut provided on the front side of the working body such that a mounting flange is located on the opposite side of the heavy load direction of the ball screw shaft;
A hydraulic cylinder fixed to the working body;
A hydraulic piston fitted inside the hydraulic cylinder in a fluid-tight manner and attached to a first ball screw nut;
A hydraulic pressure source for applying a predetermined hydraulic pressure to a ring-shaped hydraulic chamber formed by the hydraulic piston and the hydraulic cylinder;
With mounting flange and a second ball screw nuts fixedly attached to the rear side of the working body so as to be positioned on the opposite side with respect to the heavy load direction of the ball screw shaft,
The hydraulic cylinder and the hydraulic piston, holds filled with hydraulic oil at a predetermined pressure to the ring-shaped hydraulic chamber, so as to apply a preload force of a predetermined ratio at all times the maximum load to the working body, the ball screw together with the shaft is pulled in the first direction opposite the heavy load direction by the ball screw nut, said at maximum load the first and second ball screw nut are configured so as to share the maximum load of the ball screw shaft A ball screw device characterized by the above. Instead of linear movement of the ball screw nut that rotates the ball screw shaft that restrains the thrust direction to the fixed member and is screwed to the ball screw, the load coupled to the ball screw nut is moved in one direction. In a ball screw device having a load configuration in which the load is significantly larger than the load applied in the opposite direction movement,
A first ball screw nut provided on the front side of the working body such that a mounting flange is located on the opposite side of the heavy load direction of the ball screw shaft;
A hydraulic cylinder fixed to the working body;
A hydraulic piston fitted inside the hydraulic cylinder in a fluid-tight manner and attached to a first ball screw nut;
A hydraulic pressure source for applying a predetermined hydraulic pressure to a ring-shaped hydraulic chamber formed by the hydraulic piston and the hydraulic cylinder;
With mounting flange and a second ball screw nuts fixedly attached to the rear side of the working body so as to be positioned on the opposite side with respect to the heavy load direction of the ball screw shaft,
The hydraulic cylinder and the hydraulic piston, holds filled with hydraulic oil at a predetermined pressure to the ring-shaped hydraulic chamber, so as to add 40-50% of the preload force constantly maximum load to the working body, wherein with the ball screw shaft is pulled in the first by a ball screw nut and the heavy load direction opposite direction, is configured to the at full load the first and second ball screw nut to share the maximum load of the ball screw shaft ball screw device, characterized in that there. Instead of linear movement of the ball screw nut that rotates the ball screw shaft that restrains the thrust direction to the fixed member and is screwed to the ball screw, the load coupled to the ball screw nut is moved in one direction. In a ball screw device having a load configuration in which the load is significantly larger than the load applied in the opposite direction movement,
A first ball screw nut provided on the front side of the working body such that a mounting flange is located on the opposite side of the heavy load direction of the ball screw shaft;
An elastic body sandwiched between the working body and an annular plate attached to the first ball screw nut;
With mounting flange and a second ball screw nuts fixedly attached to the rear side of the working body so as to be positioned on the opposite side with respect to the heavy load direction of the ball screw shaft,
Elastic body is mounted in a state where the compressive force is preloaded to a predetermined percentage of the maximum load, the pulled in the opposite direction to the heavy load direction by the ball screw shaft is the first ball screw nut, the maximum load ball screw device, characterized in that during the first and second ball screw nut are configured so as to share the maximum load of the ball screw shaft. Instead of linear movement of the ball screw nut that rotates the ball screw shaft that restrains the thrust direction to the fixed member and is screwed to the ball screw, the load coupled to the ball screw nut is moved in one direction. In a ball screw device having a load configuration in which the load is significantly larger than the load applied in the opposite direction movement,
A first ball screw nut provided on the front side of the working body such that a mounting flange is located on the opposite side of the heavy load direction of the ball screw shaft;
An elastic body sandwiched between the working body and an annular plate attached to the first ball screw nut;
With mounting flange and a second ball screw nuts fixedly attached to the rear side of the working body so as to be positioned on the opposite side with respect to the heavy load direction of the ball screw shaft,
Elastic body, the compression force is attached in a state of pre-load such that 40-50% of the maximum load, the pulled in the opposite direction to the heavy load direction by the ball screw shaft is the first ball screw nut, ball screw device, characterized in that said at maximum load the first and second ball screw nut are configured so as to share the maximum load of the ball screw shaft. 3. The ball screw device according to claim 2, wherein a load sensor is attached to a member that receives the load of the ball screw shaft, and a control valve that controls pressure oil to the ring-shaped hydraulic chamber is provided by a detection value of the sensor. When the value is ½ (50%) or more of the maximum load, the hydraulic chamber is filled and held with a predetermined pressure of pressure, and a load of 40 to 50% of the maximum load is applied to the working body. ball screw device, characterized in that said at load first and second ball screw nut to share the maximum load of the ball screw shaft.   A plurality of ball screw devices each provided with a plurality of load sharing type nuts according to any one of claims 1 to 5 are provided in parallel to the injection screw shaft for driving a straight injection of an injection screw of an injection molding machine. An injection molding machine characterized in that the ball screw nut can share the load.

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