Mobile monitoring device

Abstract

Provided is a moving-body monitoring device that can more accurately determine the presence or absence of positional deviation of a moving body.　This moving-body monitoring device is provided with: a position detection unit 12 that outputs positional information of a moving body; a proximity sensor 22 that detects the moving body; a first storage unit 25 that stores a position when the moving body having moved in a first direction is detected by the proximity sensor 22 as first positional information, and stores a position when the moving body having moved in a second direction is detected by the proximity sensor 22 as second positional information; a calculation unit 26 that calculates a fixed-point position of a detecting region of the proximity sensor 22 during monitoring as fixed-point positional information on the basis of the first positional information and the second positional information; a second storage unit 27 that stores reference fixed-point positional information; and a monitoring unit 29 that, when a deviation between the fixed-point positional information calculated by the calculation unit 26 during the monitoring of the moving body and the reference fixed-point positional information goes beyond a stipulated range, determines that a positional deviation amount of the moving body exceeds a tolerance.

Description

[Technical field]

[0001] The present invention relates to a monitoring device for a moving object. [Background technology]

[0002] Many machine tools, industrial robots, molding devices, and the like are equipped with multiple moving parts. For example, an injection molding machine is equipped with an injection device, a mold clamping device, an ejector device, and the like as moving parts. These moving parts are provided with a power transmission mechanism that transmits the driving force of a motor to a moving body (object to be driven). As such a power transmission mechanism, a mechanism is known in the ejector device of an injection molding machine that transmits driving force from the drive shaft of one motor to multiple driven shafts via a timing belt, and drives ball screws via pulleys connected to the driven shafts (see, for example, Patent Document 1). In this mechanism, the moving body reciprocates as the ball screw is driven. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-284931 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned power transmission mechanism, if tooth jumping occurs between the timing belt and the driven pulley, a positional deviation occurs between the position of the moving body detected by the rotary encoder on the motor side and the actual position of the moving body. Conventionally, a proximity sensor has been widely used as a sensor for detecting the positional deviation of the moving body. The proximity sensor is provided in the moving path of the moving body that reciprocates by the drive of the ball screw.

[0005] Although proximity sensors are relatively inexpensive, they have the characteristic that the size of their detection area changes depending on the environmental temperature, power supply voltage, etc. If the temperature difference between winter and summer is large in the environment in which the proximity sensor is installed, the rate of change of the detection distance of the proximity sensor will be, for example, about 10%. Therefore, if the minimum positional deviation amount of the moving object caused by tooth skipping is within the range of the rate of change of the proximity sensor, there is a problem in that it is difficult to accurately determine whether or not the moving object is misaligned.

[0006] An object of the present invention is to provide a monitoring device for a moving object that can more accurately determine whether or not the moving object has shifted in position. [Means for solving the problem]

[0007] One aspect of the present invention is a monitoring device for a moving body that moves back and forth in a first direction and a second direction opposite to the first direction, comprising a position detection unit that detects the position of the moving body and outputs it as position information, a proximity sensor that detects when the moving body has passed a specific position, a first memory unit that stores the position of the moving body when a moving body moving in the first direction is detected by the proximity sensor as first position information and stores the position of the moving body when a moving body moving in the second direction is detected by the proximity sensor as second position information, a calculation unit that calculates a fixed-point position of the detection area of ​​the proximity sensor during monitoring as fixed-point position information based on at least one of the first position information and at least one of the second position information stored in the first memory unit, a second memory unit that stores reference fixed-point position information, and a monitoring unit that determines that the position deviation of the moving body has exceeded a tolerance if the deviation between the fixed-point position information calculated by the calculation unit and the reference fixed-point position information stored in the second memory unit during monitoring of the moving body falls outside a specified range. Effect of the Invention

[0008] According to the moving object monitoring device of the present invention, the presence or absence of positional deviation of the moving object can be determined more accurately. [Brief description of the drawings]

[0009] [Figure 1]1 is a block diagram showing a system configuration of an ejector device 1. FIG. [Diagram 2] 11A to 11C are diagrams illustrating the operation of the proximity sensor 22 when the table 15 is moved in two directions. [Diagram 3] 11A to 11C are diagrams illustrating the operation of the proximity sensor 22 when the table 15 is moved in one direction. [Figure 4] 5 is a flowchart showing a procedure of a process for detecting a positional deviation of a table 15 in the ejector device 1 of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the monitoring device for a moving object according to the present invention will be described in which it is applied to an ejector device of an injection molding machine. The ejector device is a device that has a function of removing a molded product from within a mold of a mold clamping device (not shown) in an injection molding machine.

[0011] Fig. 1 is a block diagram showing a system configuration of the ejector device 1. Fig. 2 is a diagram explaining the operation of the proximity sensor 22 when the table 15 is moved in two directions. Fig. 3 is a diagram explaining the operation of the proximity sensor 22 when the table 15 is moved in one direction.

[0012] Note that all drawings attached to this specification are schematic diagrams, and the shape, scale, aspect ratio, etc. of each part are modified or exaggerated from the actual one in consideration of ease of understanding, etc. Furthermore, in this specification, etc., terms that specify shapes, geometric conditions, and the extent of these, such as the term "direction," include the range that can be roughly regarded as that direction in addition to the strict meaning of the term.

[0013] As shown in FIG. 1, the ejector device 1 includes a movable mechanism 10 and a control device 20. The movable mechanism 10 includes a motor 11, a position detector 12, a power transmission unit 13, a ball screw 14, and a table (moving body) 15. Note that in Fig. 1, only parts of the movable mechanism 10 that are necessary for explaining the monitoring device for a moving body according to the present invention are shown.

[0014] The motor 11 is a power source that generates a rotational force for driving the ball screw 14. The motor 11 is configured by a servo motor. The motor 11 is provided with a position detection unit 12. The position detection unit 12 is a detection device that detects the position of the table 15 (described later) and outputs it as position information. The position detection unit 12 counts the number of pulses generated with the rotation of the motor 11, and outputs the position information of the table 15 on the ball screw 14 as the number of pulses corresponding to the rotation angle of the motor 11. The position detection unit 12 is configured by, for example, a rotary encoder. The position signal output from the position detection unit 12 is transmitted to the control unit 21 as a semi-closed feedback signal, and is also transmitted to the first storage unit 25.

[0015] The power transmission unit 13 is a mechanism that transmits the rotational force generated by the motor 11 to the ball screw 14. The power transmission unit 13 includes a driving pulley 131, a driven pulley 132, and a timing belt 133. The driving pulley 131 is a pulley provided on a drive shaft of the motor 11. The driven pulley 132 is a pulley connected to the ball screw 14. Although a plurality of driven pulleys 132 are often provided for the ball screw 14, FIG. 1 shows a simplified configuration in which one driven pulley 132 is connected to the ball screw 14. The timing belt 133 is an endless belt that transmits the rotational force of the driving pulley 131 to the driven pulley 132. The timing belt 133 is stretched between the driving pulley 131 and the driven pulley 132.

[0016] The ball screw 14 is a mechanism that converts the rotational motion generated by the motor 11 into linear motion. The table 15 is connected to the ball screw 14. The table 15 can be reciprocated by controlling the rotation of the motor 11 to rotate the ball screw 14 forward or backward. In this specification, the movement direction of the table 15 is defined as the X direction. In the X direction, the direction in which the table 15 moves away from the driven pulley 132 is defined as the X1 direction (first direction), and the direction in which the table 15 moves toward the driven pulley 132, which is opposite to the X1 direction, is defined as the X2 direction (second direction). In this specification, the "direction" is also referred to as the "side" as appropriate.

[0017] The table 15 is a moving body connected to an ejector rod (not shown) that moves in and out of the mold. When the table 15 moves in the X1 direction, the tip of the ejector rod advances and is protruded into the mold, and the molded product is pushed out from the mold. When the table 15 moves in the X2 direction, the tip of the ejector rod retreats to a predetermined position in the mold. In this way, the ejector rod advances and retreats in conjunction with the reciprocating motion of the table 15, so that the molded product can be removed from the mold for each molding cycle. In FIG. 1, the base point that is the origin position of the table 15 is represented by "X00", and the end point that is the turning point of the table 15 moved in the X1 direction is represented by "X0Z". In addition, FIG. 1 shows the state where the table 15 is located at the base point X00 and the end point X0Z, respectively.

[0018] The control device 20 includes a control unit 21, a proximity sensor 22, a detection unit 23, a command generation unit 24, a first storage unit 25, a calculation unit 26, a second storage unit 27, a fixed-point position selection unit 28, and a monitoring unit 29. In Fig. 1, the position detection unit 12, the proximity sensor 22, the first storage unit 25, the calculation unit 26, the second storage unit 27, and the monitoring unit 29 constitute a monitoring device 2 for a moving object in this embodiment.

[0019] The control unit 21 is a control unit that controls the driving of the motor 11 based on the operation command generated by the command generation unit 24, and is configured with a microprocessor including a CPU (Central Processing Unit), memory, etc. The functions of the control unit 21 may be realized by a combination of hardware and software, or may be realized only by hardware (electronic circuits).

[0020] The proximity sensor 22 is a non-contact sensor that detects when the table 15 has passed a specific position on the ball screw 14. The signal output from the proximity sensor 22 changes to either ON (operation) or OFF (return) level depending on the detection result. When the table 15 enters the detection area (described below) of the proximity sensor 22, the signal output from the proximity sensor 22 becomes ON level. On the other hand, when the table 15 leaves the detection area of ​​the proximity sensor 22, the signal output from the proximity sensor 22 becomes OFF level. Note that in this specification and the like, a line passing through the center of the proximity sensor 22 will be described as the "reference axis CX" as shown in Figures 2 and 3 (described below).

[0021] The detection unit 23 detects whether the table 15 has approached or moved away from the proximity sensor 22 based on the level (ON / OFF) of the signal output from the proximity sensor 22. When the signal output from the proximity sensor 22 changes from an OFF level to an ON level, the detection unit 23 transmits a detection signal to the command generation unit 24 and the first storage unit 25.

[0022] The command generating unit 24 generates an operation command for the control unit 21 to drive the motor 11. The command generating unit 24 is provided with an operation program describing the operation of the ejector device 1. The command generating unit 24 generates an operation command based on the provided operation program. For example, the command generating unit 24 creates an operation command to drive the ball screw 14 by the motor 11 so that the table 15 approaches the proximity sensor 22. The command generating unit 24 also creates an operation command to drive the ball screw 14 by the motor 11 so that the table 15 moves away from the proximity sensor 22. The operation command generated by the command generating unit 24 is transmitted to the control unit 21. The operation command transmitted from the command generating unit 24 to the control unit 21 controls the rotation direction, rotation speed, rotation amount (rotation angle), etc. of the motor 11. As a result, the forward / rearward movement of an ejector rod (not shown) connected to the table 15 is controlled in one molding cycle.

[0023] The first storage unit 25 is a storage device that stores position information of the table 15 and the like. The first storage unit 25 stores, as first position information, a position of the table 15 moved in the X1 direction (first direction) by the ball screw 14 when the proximity sensor 22 detects the table 15. The first storage unit 25 stores, as second position information, a position of the table 15 moved in the X2 direction (second direction) by the ball screw 14 when the proximity sensor 22 detects the table 15. The first storage unit 25 also stores information about a specified range that is used in the monitoring unit 29 when determining the magnitude of deviation between the fixed-point position information calculated by the calculation unit 26 and the reference fixed-point position information stored in the second storage unit 27. The information about the specified range may be stored not only in the first storage unit 25 but also in the monitoring unit 29 or another storage unit.

[0024] At the time of receiving a detection signal from detection unit 23, first storage unit 25 stores the position information indicating the position of table 15 transmitted from position detection unit 12 as first position information. The same applies to the second position information. Note that first storage unit 25 may store one set of the first position information and the second position information, or may store multiple sets. Storing multiple sets of the first position information and the second position information means that table 15 is caused to reciprocate multiple times in succession, and the first position information and the second position information are stored in association with each reciprocation.

[0025] As described above, the size of the detection area S of the proximity sensor 22 changes depending on the environmental temperature, power supply voltage, etc. Fig. 2 shows the change in level of the signal output from the proximity sensor 22 when the table 15 is reciprocated in two directions (X1 direction and X2 direction) in two detection areas S of different sizes. The upper diagram of Fig. 2 shows the change in level of the signal when the detection area S of the proximity sensor 22 is large. The lower diagram of Fig. 2 shows the change in level of the signal when the detection area S of the proximity sensor 22 is small. Note that the time axes of the timing charts showing the change in level of the signal are the same in the upper and lower diagrams of Fig. 2.

[0026] 2, the range of detection area S of proximity sensor 22 is indicated by solid and dashed lines. In detection area S, the solid line portion indicates the range where proximity sensor 22 is at ON level. Moreover, the dashed line portion indicates the range where proximity sensor 22 is at OFF level. As shown in FIG. 2, the signal output from proximity sensor 22 becomes ON level when table 15 approaches proximity sensor 22 and enters the solid line range of detection area S, and becomes OFF level when table 15 moves away from proximity sensor 22 and leaves the dashed line range of detection area S.

[0027] 2, when the table 15, which has moved from the base point side (X2 side) in the X1 direction, is detected by the proximity sensor 22 at position X11, the signal output from the proximity sensor 22 changes from OFF level to ON level at position X11. The position X11 at which the table 15 was detected by the proximity sensor 22 is stored as first position information in the first storage unit 25. When the table 15 further moves away from the proximity sensor 22 in the X1 direction and is no longer detected by the proximity sensor 22, the signal output from the proximity sensor 22 changes from ON level to OFF level.

[0028] On the other hand, when the table 15, which has moved from the end point side (X1 side) in the X2 direction, is detected by the proximity sensor 22 at position X21, the signal output from the proximity sensor 22 changes from OFF level to ON level at position X21. The position X21 at which the table 15 was detected by the proximity sensor 22 is stored as second position information in the first storage unit 25. When the table 15 further moves away from the proximity sensor 22 in the X2 direction and is no longer detected by the proximity sensor 22, the signal output from the proximity sensor 22 changes from ON level to OFF level. The relationship between the size of the detection area S and the change in the level of the signal output from the proximity sensor 22 in the upper and lower diagrams of FIG. 2 will be described later.

[0029] The calculation unit 26 calculates the fixed position of the detection area S of the proximity sensor 22 during positional deviation monitoring as fixed position information based on the first position information and the second position information stored in the first storage unit 25. The fixed position is the position indicated by symbol X01 in the upper diagram of FIG. 2, and the position indicated by symbol X02 in the lower diagram of FIG. 2. Hereinafter, the fixed positions X01 and X02 are collectively referred to as "fixed position X0k." In the calculation unit 26, the fixed position X0k is calculated as the average value of the position of the table 15 indicated by the first position information and the position of the table 15 indicated by the second position information. The fixed position information calculated by the calculation unit 26 is transmitted to the monitoring unit 29.

[0030] In addition, when the calculation unit 26 calculates the fixed-point position information based on a plurality of sets of first position information and second position information, the calculation unit 26 calculates the fixed-point position information based on these position information when the required number of the first position information and the second position information is complete in the first storage unit 25. For example, in a plurality of sets of first position information and second position information, the fixed-point position may be calculated for each set, and the average value of the plurality of fixed-point positions may be used as the final fixed-point position information.

[0031] For example, in the upper diagram of FIG. 2, when the table 15 moved in the X1 direction is detected by the proximity sensor 22 at the position X11, the distance from the reference point (position X00 in FIG. 1) to the position X11 is set to 500 mm. Then, after turning back at the end point, when the table 15 moved in the X2 direction is detected by the proximity sensor 22 at the position X21, if the distance from the reference point to the position X21 is set to 800 mm, the fixed-point position X01 calculated by the calculation unit 26 is 650 mm. Similarly, in the lower diagram of FIG. 2, when the table 15 moved in the X1 direction is detected by the proximity sensor 22 at the position X12, the distance from the reference point to the position X12 is set to 600 mm. Then, after turning back at the end point, when the table 15 moved in the X2 direction is detected by the proximity sensor 22 at the position X22, if the distance from the reference point to the position X22 is set to 700 mm, the fixed-point position X02 calculated by the calculation unit 26 is 650 mm.

[0032] As shown in FIG. 2, even when the size of the detection region S of the proximity sensor 22 changes due to environmental temperature, power supply voltage, etc., if the shape of the detection region S is line-symmetric with respect to the reference axis CX, regardless of the size of the detection region S, the fixed-point position X0k is at the same position (X01 = X02). Such a characteristic is, as shown in FIG. 2, not only when the distances L1 and L2 between the table 15 and the proximity sensor 22 are the same and the size of the detection region S of the proximity sensor 22 changes, but also when the size of the detection region S is the same and the distances L1 and L2 between the table 15 and the proximity sensor 22 change (L1 > L2 or L1 < L2).

[0033] For comparison, the operation of the proximity sensor 22 when the table 15 is moved in one direction will now be described. Fig. 3 shows the change in signal level output from the proximity sensor 22 when the table 15 is moved in one direction (for example, the X1 direction). The upper diagram of Fig. 3 shows the change in signal level when the detection area S of the proximity sensor 22 is large. The lower diagram of Fig. 3 shows the change in signal level when the detection area S of the proximity sensor 22 is small. In the upper and lower diagrams of Fig. 3, the time axes of the timing charts showing the change in signal level are the same.

[0034] In the upper diagram of Fig. 3, when table 15, which has moved in the X1 direction from the base point side, is detected by proximity sensor 22 at position X11, the signal output from proximity sensor 22 changes from OFF level to ON level at position X11. In this detection example, position X11 when table 15 is detected by proximity sensor 22 becomes first position information. After that, when table 15 moves away from proximity sensor 22 in the X1 direction and is no longer detected by proximity sensor 22, the signal output from proximity sensor 22 changes from ON level to OFF level. In this detection example, position X11a where table 15, which has been moved in the X1 direction, is no longer detected by proximity sensor 22 becomes second position information.

[0035] In the operation example shown in the upper diagram of Fig. 3, when the average value of the position X11 of the table 15 represented by the first position information and the position X11a of the table 15 represented by the second position information is calculated, the fixed point position is X01a. Here, although not shown in the upper diagram of Fig. 3, if the position at which the table 15 is detected by the proximity sensor 22 when the proximity sensor 22 is moved from the end point side (X1 side) in the X2 direction is the position X21 as in the upper diagram of Fig. 2, the hysteresis is D1. The hysteresis refers to the difference between the position at which the signal level turns ON when the table 15 approaches the proximity sensor 22 and the position at which the signal level turns OFF when the table 15 moves away from the proximity sensor 22. The effect of the hysteresis will be described later.

[0036] On the other hand, in the lower diagram of Fig. 3, when the table 15 that has moved in the X1 direction from the base point side is detected by the proximity sensor 22 at position X12, the signal output from the proximity sensor 22 changes from OFF level to ON level at position X12. In this detection example, position X12 when the table 15 is detected by the proximity sensor 22 becomes the first position information. After that, when the table 15 moves away from the proximity sensor 22 in the X1 direction and is no longer detected by the proximity sensor 22, the signal output from the proximity sensor 22 changes from ON level to OFF level. In this detection example, position X12a where the table 15 that has been moved in the X1 direction is no longer detected by the proximity sensor 22 becomes the second position information.

[0037] In the operation example shown in the lower diagram of Fig. 3, when the average value of the position X12 of the table 15 represented by the first position information and the position X12a of the table 15 represented by the second position information is calculated, the fixed point position becomes X02a. Here, although not shown in the lower diagram of Fig. 3, if the position where the table 15 is detected by the proximity sensor 22 when the proximity sensor 22 is moved from the end point side (X1 side) in the X2 direction is the position X22 as in the lower diagram of Fig. 2, the response differential becomes D2.

[0038] Comparing the upper and lower diagrams of FIG. 3, the fixed-point position X01a calculated under the conditions in the upper diagram and the fixed-point position X02a calculated under the conditions in the lower diagram are not the same position, but are shifted by 1 / 2 the amount of change in the hysteresis (D1-D2). This is because the hysteresis also changes in proportion to the change in the size of the detection area S (D1>D2). If the fixed-point position is calculated based on the first position information and the second position information detected when the table 15 is moved in one direction, if the size of the detection area S changes, the fixed-point position will be shifted due to the influence of the hysteresis. Thus, in this detection example, if the size of the detection area S changes due to the influence of the environmental temperature, the power supply voltage, etc., the detection accuracy of the positional deviation of the table 15 will decrease.

[0039] On the other hand, in this embodiment, the calculation unit 26 calculates the fixed-point position based on the first position information and the second position information detected when the table 15 is reciprocated in two directions, as shown in Fig. 2. In this way, even if the size of the detection area S changes, the fixed-point position can be accurately calculated without being affected by the response differential, and therefore the detection accuracy of the positional deviation of the table 15 can be improved.

[0040] Returning to FIG. 1, the explanation will be given. The second storage unit 27 stores the fixed-point position information calculated by the calculation unit 26 when the fixed-point position is calibrated as reference fixed-point position information. Calibration of the fixed-point position refers to the operation of registering a correct fixed-point position as a reference before performing the operation of monitoring the deviation of the fixed-point position. An example of the time of calibration of the fixed-point position is when the ejector device 1 is set up. When the ejector device 1 is set up, each part of the power transmission unit 13 is adjusted to a normal state, and then the table 15 is reciprocated once or multiple times on a trial basis to detect the first and second position information, and the fixed-point position is calculated based on these position information, thereby obtaining the reference fixed-point position information. The reference fixed-point position information stored in the second storage unit 27 is read out to the monitoring unit 29 at a predetermined timing.

[0041] The reference fixed point position information does not necessarily have to be a value calculated by the calculation unit 26. During calibration, an external measuring device may be used to measure the distance from the base point X00 to the reference axis CX (see FIG. 2), and the result may be stored in the second storage unit 27 as the reference fixed point position information. As the external measuring device, for example, a laser displacement meter may be used. Alternatively, the base point X00 of the position detection unit 12 may be set in a state in which the table 15 is stopped on the reference axis CX. Generally, the coordinate value of the base point X00 is set to 0 (zero), so the reference fixed point position information is 0, and 0 may also be recorded in the second storage unit 27.

[0042] The fixed-point position selection unit 28 switches between electrical continuity between the calculation unit 26 and the second storage unit 27 and electrical continuity between the calculation unit 26 and the monitoring unit 29. When the fixed-point position selection unit 28 switches to electrical continuity between the calculation unit 26 and the second storage unit 27, reference fixed-point position information calculated by the calculation unit 26 is stored in the second storage unit 27 during calibration of the fixed-point position. On the other hand, when the fixed-point position selection unit 28 switches to electrical continuity between the calculation unit 26 and the monitoring unit 29, point position information calculated by the calculation unit 26 is transmitted to the monitoring unit 29 during positional deviation monitoring.

[0043] The monitoring unit 29 judges whether the deviation between the fixed-point position information calculated by the calculation unit 26 and the reference fixed-point position information stored in the second storage unit 27 falls outside a specified range. When the monitoring unit 29 judges that the deviation between the fixed-point position information acquired from the calculation unit 26 and the reference fixed-point position information acquired from the second storage unit 27 falls within a specified range, the monitoring unit 29 notifies a higher-level device (not shown) that controls the injection molding machine of normality (no positional deviation of the table 15). On the other hand, when the monitoring unit 29 judges that the deviation between the fixed-point position information acquired from the calculation unit 26 and the reference fixed-point position information acquired from the second storage unit 27 falls outside the specified range, that is, when the monitoring unit 29 judges that the positional deviation amount of the table 15 exceeds an allowable value, the monitoring unit 29 notifies an abnormality (there is a positional deviation of the table 15) to the higher-level device that controls the injection molding machine. After this, a predetermined abnormality process is performed in the higher-level device.

[0044] Next, a description will be given of a process for detecting a positional deviation of the table 15 in the ejector device 1 of this embodiment. Fig. 4 is a flowchart showing a process for detecting a positional deviation of the table 15 in the ejector device 1 of this embodiment. The reciprocating motion of the table 15 by the ball screw 14 is executed by transmitting an operation command generated by a command generating unit 24 to the control unit 21, and therefore a description thereof will be omitted here.

[0045] In step S101, the detection unit 23 determines whether or not the signal output from the proximity sensor 22 has changed from the OFF level to the ON level. In step S102, if the detection unit 23 determines that the signal output from the proximity sensor 22 has changed from the OFF level to the ON level, the process proceeds to step S102. On the other hand, in step S101, if the detection unit 23 determines that the signal output from the proximity sensor 22 has not changed from the OFF level to the ON level, the process proceeds to step S101.

[0046] In step S102 (step S101: YES), the detection unit 23 transmits a detection signal to the command generation unit 24 and the first storage unit 25. As a result, the first storage unit 25 stores the first position information.

[0047] In step S103, the detection unit 23 determines whether or not the signal output from the proximity sensor 22 has changed from the OFF level to the ON level. If the detection unit 23 determines in step S103 that the signal output from the proximity sensor 22 has changed from the OFF level to the ON level, the process proceeds to step S104. On the other hand, if the detection unit 23 determines in step S103 that the signal output from the proximity sensor 22 has not changed from the OFF level to the ON level, the process proceeds to step S103.

[0048] In step S104 (step S103: YES), the detection unit 23 transmits a detection signal to the command generation unit 24 and the first storage unit 25. As a result, the first storage unit 25 stores the second position information.

[0049] In step S105, the calculation unit 26 determines whether or not the required number of pieces of first position information and second position information have been stored in the first storage unit 25. If the calculation unit 26 determines in step S105 that the required number of pieces of first position information and second position information have been stored in the first storage unit 25, the process proceeds to step S106. If the calculation unit 26 determines in step S105 that the required number of pieces of first position information and second position information have not been stored in the first storage unit 25, the process proceeds to step S101.

[0050] In step S106, the calculation unit 26 calculates a fixed position of the detection area S of the proximity sensor 22 when monitoring the position shift based on the first position information and the second position information stored in the first memory unit 25, and transmits the fixed position information to the monitoring unit 29.

[0051] In step S107, the monitoring unit 29 determines whether the deviation between the fixed-point position information calculated by the calculation unit 26 and the reference fixed-point position information stored in the second storage unit 27 falls outside a specified range. If the monitoring unit 29 determines in step S107 that the deviation between the fixed-point position information and the reference fixed-point position information falls outside the specified range, the process proceeds to step S108. On the other hand, if the monitoring unit 29 determines in step S107 that the deviation between the fixed-point position information and the reference fixed-point position information does not fall outside the specified range, the process proceeds to step S109.

[0052] In step S108 (step S107: YES), monitoring unit 29 notifies a host device that controls the injection molding machine of an abnormality (there is a positional deviation of table 15). After completion of step S108, the process of this flowchart ends.

[0053] In step S109 (step S107: NO), monitoring unit 29 notifies the host device that controls the injection molding machine of normality (no positional deviation of table 15). After completion of step S109, the processing of this flowchart ends. Note that, if monitoring unit 29 determines in step S107 that the deviation between the fixed-point position information and the reference fixed-point position information does not fall outside the specified range, the processing of this flowchart may end without monitoring unit 29 notifying the host device that controls the injection molding machine of normality.

[0054] According to the above-described mobile object monitoring device 2 of the present embodiment, for example, the following effects are achieved. In the mobile body monitoring device 2 of this embodiment, the calculation unit 26 calculates the fixed-point position based on the first position information and the second position information detected when the table (mobile body) 15 is reciprocated in two directions. Therefore, even if the size of the detection area S of the proximity sensor 22 changes, the fixed-point position can be accurately calculated without being affected by the response differential. As a result, even if the size of the detection area S changes due to the environmental temperature, power supply voltage, etc., the fixed-point position can be accurately calculated without being affected by the response differential, so that the detection accuracy of the positional deviation of the table 15 can be further improved.

[0055] A specific example will now be described. In the location where the ejector device is installed, when the temperature difference in the environmental temperature is 40°C throughout the year, the rate of change in the detection distance (operating range) of the proximity sensor is assumed to be 12% in absolute value. If one side of a commonly available inexpensive rectangular proximity sensor is 17 mm and the length of this side is used as the standard for the detection distance, the maximum fluctuation range of the detection distance due to the environmental temperature is 17 mm x 0.12 ≒ 2 mm. In addition, if the hysteresis of the proximity sensor is 10% of the detection distance, the error due to the hysteresis of the position detected when the moving body is moved in one direction is 2 mm x 0.10 x 1 / 2 = 0.1 mm.

[0056] On the other hand, in an ejector device used in a small injection molding machine, if the number of teeth of the driven pulley is 40 and the moving pitch of the ball screw is 10 mm, the moving amount of the ball screw per tooth of the driven pulley is 10 / 40 = 0.25 mm. If this value is the minimum positional deviation to be detected, the above-mentioned fluctuation range of the detection distance and errors due to the response difference make it impossible to detect the positional deviation with high accuracy. However, according to the monitoring device 2 for the moving body of this embodiment, errors due to the fluctuation range of the detection distance and the response difference can be eliminated, so that the detection accuracy of the positional deviation of the moving body can be further improved.

[0057] According to the moving object monitoring device 2 of this embodiment, a proximity sensor is used as a sensor for detecting that the table 15 has passed a specific position, so that it is possible to determine whether or not the table 15 has shifted in position using inexpensive means. According to the mobile object monitoring device 2 of this embodiment, the monitoring unit 29 judges whether or not the deviation between the fixed-point position information calculated based on one or more pieces of first position information and second position information and the reference fixed-point position information calculated when calibrating the fixed-point position falls outside a specified range. This makes it possible to eliminate the influence of the variance in the fixed-point position information calculated by the calculation unit 26, and therefore makes it possible to more accurately judge whether or not the table 15 has shifted in position.

[0058] Although the embodiment of the present invention has been described above, the present invention is not limited to the above-mentioned embodiment, and various modifications and changes are possible, such as the modified forms described below, which are also included in the technical scope of the present invention. Furthermore, the effects described in the embodiment are merely a list of the most preferable effects resulting from the present invention, and are not limited to those described in the embodiment. The above-mentioned embodiment and the modified forms described below can be used in appropriate combination, but detailed description will be omitted.

[0059] (Variations) In the embodiment, an example has been described in which the detection unit 23 outputs a detection signal for the table (moving body) 15 when the signal output from the proximity sensor 22 changes from an OFF level to an ON level, but the present invention is not limited to this. The detection signal for the table 15 may be output when the signal output from the proximity sensor 22 changes from an ON level to an OFF level.

[0060] In the embodiment, an example has been described in which the proximity sensor 22 for detecting the positional deviation of the table 15 is provided near the ball screw 14, but the present invention is not limited to this. A proximity sensor for confirming the retreat of the ejector rod (not shown) may also be used as the proximity sensor 22. With such a configuration, the cost of the monitoring device can be reduced. [Explanation of symbols]

[0061] 1: ejector device, 2: moving body monitoring device, 10: movable mechanism, 11: motor, 12: position detection unit, 13: power transmission unit, 14: ball screw, 15: table (moving body), 20: control device, 21: control unit, 22: proximity sensor, 23: detection unit, 24: command generation unit, 25: first memory unit, 26: calculation unit, 27: second memory unit, 28: fixed point position selection unit, 29: monitoring unit

Claims

1. A monitoring device for a moving object that reciprocates in a first direction and a second direction opposite to the first direction, a position detection unit that detects the position of a moving object and outputs the detected position as position information; A proximity sensor that detects when a moving object passes a specific position; a first storage unit that stores a position of the moving body when the moving body moving in the first direction is detected by the proximity sensor as first position information, and stores a position of the moving body when the moving body moving in the second direction is detected by the proximity sensor as second position information; a calculation unit that calculates a fixed-point position of a detection area of ​​the proximity sensor during monitoring as fixed-point position information based on at least one of the first position information and at least one of the second position information stored in the first storage unit; A second storage unit that stores reference fixed point position information; a monitoring unit that determines that a positional deviation amount of the moving body has exceeded an allowable value when a deviation between the fixed-point position information calculated by the calculation unit and the reference fixed-point position information stored in the second storage unit falls outside a specified range during monitoring of the moving body; A monitoring device for a moving object comprising:

2. The second storage unit stores the fixed-point position information calculated by the calculation unit at the time of calibration of the fixed-point position as reference fixed-point position information. The monitoring device according to claim 1.

3. The first storage unit is When the proximity sensor detects that the moving object moving in the first direction has entered a detection area of ​​the proximity sensor, the position of the moving object at that time is stored as first position information; when the proximity sensor detects that the moving object moving in the second direction has entered a detection area of ​​the proximity sensor, the position of the moving object at that time is stored as second position information; 3. A monitoring device according to claim 1 or 2.

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