Monitoring device for a moving body

Abstract

A mobile body monitoring device capable of more accurately determining whether or not a position of a mobile body is shifted is provided. The mobile body monitoring device includes a position detection unit (12) that outputs position information of a mobile body; a proximity sensor (22) that detects the mobile body; a first storage unit (25) that stores, as first position information, a position at which the mobile body that has moved in a first direction is detected by the proximity sensor (22), and stores, as second position information, a position at which the mobile body that has moved in a second direction is detected by the proximity sensor (22); a calculation unit (26) that calculates, as point position information, a point position of a detection area of the proximity sensor (22) at a monitoring time based on the first position information and the second position information; a second storage unit (27) that stores reference point position information; and a monitoring unit (29) that determines that a position shift amount of the mobile body exceeds an allowable value when a deviation between the point position information calculated by the calculation unit (26) at the time of monitoring the mobile body and the reference point position information exceeds a prescribed range.

Description

Technical Field

[0001] This invention relates to a monitoring device for a moving body. Background Technology

[0002] Machine tools, industrial robots, molding equipment, and similar devices often have multiple movable parts. For example, an injection molding machine has an injection unit, a mold clamping unit, and a demolding unit as movable parts. These movable parts are equipped with a power transmission mechanism for transmitting the driving force of a motor to a moving body (the object being driven). As such a power transmission mechanism, a known method is a mechanism in the demolding unit of an injection molding machine that transmits driving force from a motor drive shaft to multiple driven shafts via a timing belt, and drives a ball screw via pulleys connected to the driven shafts (see, for example, Patent Document 1). In this mechanism, the moving body is driven by the ball screw to perform reciprocating motion.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2010-284931 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In such a power transmission mechanism, when tooth skipping occurs between the timing belt and the driven pulley, a positional offset occurs between the position of the moving part detected by the rotary encoder on the motor side and the actual position of the moving part. Conventionally, proximity sensors have been commonly used as sensors to detect this positional offset. These proximity sensors are positioned along the movement path of the moving part, which reciprocates via a ball screw.

[0008] Proximity sensors are relatively inexpensive, but their detection area size varies depending on ambient temperature, power supply voltage, and other factors. In environments where proximity sensors are installed, the detection distance can change by a factor of approximately ten in winter and summer due to significant temperature differences. Therefore, a problem arises: when the minimum positional offset of a moving object caused by skipping teeth falls within the range of the proximity sensor's rate of change, it becomes difficult to accurately determine whether the object's positional offset has occurred.

[0009] The purpose of this invention is to provide a monitoring device for a moving body that can more accurately determine the presence or absence of a moving body's positional shift.

[0010] Solution for solving the problem

[0011] One aspect of the present invention is a monitoring device for a moving body that reciprocates in a first direction and a second direction, the second direction being opposite to the first direction. The monitoring device comprises: a position detection unit that detects the position of the moving body and outputs the position of the moving body as position information; a proximity sensor that detects when the moving body has passed a specific position; a first storage unit that stores the position of the moving body when it is detected by the proximity sensor in the first direction as first position information, and the position of the moving body when it is detected by the proximity sensor in the second direction as second position information; a calculation unit that calculates a fixed-point position of the detection area of ​​the proximity sensor during monitoring 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, as fixed-point position information; a second storage unit that stores reference fixed-point position information; and a monitoring unit that determines that the position offset of the moving body exceeds an allowable value 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 storage unit exceeds a predetermined range during monitoring of the moving body.

[0012] The effects of the invention

[0013] According to the monitoring device for moving bodies of the present invention, it is possible to more accurately determine whether there is a positional shift of the moving body. Attached Figure Description

[0014] Figure 1 This is a block diagram showing the system structure of the demolding device 1.

[0015] Figure 2 This diagram illustrates the action of the proximity sensor 22 when the plate 15 is moved in two directions.

[0016] Figure 3 This diagram illustrates the action of the proximity sensor 22 when the plate 15 is moved in one direction.

[0017] Figure 4 This is a flowchart illustrating the process of detecting the positional offset of the plate 15 in the demolding device 1 of the embodiment. Detailed Implementation

[0018] The following describes an embodiment in which the monitoring device for the moving body according to the present invention is applied to a demolding device of an injection molding machine. The demolding device is a device in an injection molding machine that has the function of removing the molded article from the mold of a mold closing device (not shown).

[0019] Figure 1This is a block diagram showing the system structure of the demolding device 1. Figure 2 This diagram illustrates the action of the proximity sensor 22 when the plate 15 is moved in two directions. Figure 3 This diagram illustrates the action of the proximity sensor 22 when the plate 15 is moved in one direction.

[0020] Furthermore, the accompanying drawings are all schematic diagrams. To facilitate understanding, the shapes, scales, and aspect ratios of each part have been altered or exaggerated compared to the actual object. Additionally, in this specification, terms used to describe shapes, geometric conditions, and the degree to which they are determined, such as the term "direction," include not only its strict meaning but also the range that is roughly considered to be that direction.

[0021] like Figure 1 As shown, the demolding device 1 includes a movable mechanism 10 and a control device 20.

[0022] The movable mechanism 10 includes a motor 11, a position detection unit 12, a power transmission unit 13, a ball screw 14, and a flat plate (moving body) 15. Furthermore, in Figure 1 The structure of the movable mechanism 10 is shown only for the purposes of describing the monitoring device for the moving body involved in this invention.

[0023] Motor 11 is a power source that generates rotational force to drive ball screw 14. Motor 11 is a servo motor. A position detection unit 12 is provided in motor 11.

[0024] The position detection unit 12 is a detection device for detecting the position of the plate 15 (described later) and outputting that position as position information. The position detection unit 12 counts the number of pulses generated as the motor 11 rotates, and outputs the position information of the plate 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, for example, composed of a rotary encoder. The position signal output from the position detection unit 12 is sent to the control unit 21 as a semi-closed feedback signal, and also to the first storage unit 25.

[0025] The power transmission unit 13 is a mechanism for transmitting the rotational force generated by the motor 11 to the ball screw 14. The power transmission unit 13 includes a drive pulley 131, a driven pulley 132, and a timing belt 133. The drive pulley 131 is a pulley mounted on the drive shaft of the motor 11. The driven pulley 132 is a pulley connected to the ball screw 14. Furthermore, multiple driven pulleys 132 are typically provided for the ball screw 14, but... Figure 1To simplify the structure, a configuration is shown for connecting a ball screw 14 to a driven pulley 132. A timing belt 133 is an annular belt used to transmit the rotational force of the drive pulley 131 to the driven pulley 132. The timing belt 133 is positioned between the drive pulley 131 and the driven pulley 132.

[0026] The ball screw 14 is a mechanism for converting the rotary motion generated by the motor 11 into linear motion. A plate 15 is connected to the ball screw 14. By controlling the rotation of the motor 11, the ball screw 14 can be rotated forward or backward, enabling the plate 15 to reciprocate. Furthermore, in this specification, the direction of movement of the plate 15 is defined as the X direction. The direction in the X direction where the plate 15 moves away from the driven pulley 132 is defined as the X1 direction (first direction), and the direction opposite to the X1 direction where the plate 15 moves towards the driven pulley 132 is defined as the X2 direction (second direction). Additionally, in this specification, the "~ direction" is appropriately referred to as the "~ side".

[0027] Plate 15 is a moving body connected to an ejector rod (not shown) that enters and exits the mold. When plate 15 moves in the X1 direction, the front end of the ejector rod advances and protrudes into the mold to push the molded part out of the mold. When plate 15 moves in the X2 direction, the front end of the ejector rod retracts to a predetermined position within the mold. In this way, by linking the forward and backward movements of the ejector rod and plate 15, the molded part can be removed from the mold in each molding cycle. Furthermore, in Figure 1 In the diagram, "X00" represents the base point as the origin of plate 15, and "X0Z" represents the endpoint as the turning point of plate 15 after it has moved in the X1 direction. Additionally, in... Figure 1 The diagram schematically illustrates the states of the plate 15 at the base point X00 and the endpoint X0Z, respectively.

[0028] 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. Figure 1 In this embodiment, 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 body.

[0029] The control unit 21 is a control unit that controls the drive of the motor 11 based on the action commands generated by the instruction generation unit 24. It is composed of a microcontroller including a CPU (central processing unit), memory, etc. Furthermore, the functions of the control unit 21 can be implemented either through the cooperation of hardware and software or solely through hardware (electronic circuitry).

[0030] The proximity sensor 22 is a sensor that detects the passage of the plate 15 to a specific position on the ball screw 14 in a non-contact manner. The signal output from the proximity sensor 22 changes to either an ON (operation) or OFF (reset) level depending on the detection result. When the plate 15 enters the detection area of ​​the proximity sensor 22 (described later), the signal output from the proximity sensor 22 is at an ON level. On the other hand, when the plate 15 leaves the detection area of ​​the proximity sensor 22, the signal output from the proximity sensor 22 is at an OFF level. Furthermore, in this specification, etc., as... Figure 2 and Figure 3 As shown (described later), the line passing through the center of the proximity sensor 22 will be designated as the "reference axis CX" for explanation.

[0031] The detection unit 23 detects whether the plate 15 is moving closer to or 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 sends a detection signal to the instruction generation unit 24 and the first storage unit 25.

[0032] The instruction generation unit 24 generates motion commands for the control unit 21 to drive the motor 11. An action program describing the operation of the demolding device 1 is provided to the instruction generation unit 24. The instruction generation unit 24 generates motion commands based on the provided action program. For example, the instruction generation unit 24 generates a motion command that drives the ball screw 14 by the motor 11 to move the plate 15 closer to the proximity sensor 22. Additionally, the instruction generation unit 24 generates a motion command that drives the ball screw 14 by the motor 11 to move the plate 15 away from the proximity sensor 22. The motion commands generated by the instruction generation unit 24 are sent to the control unit 21. By sending motion commands from the instruction generation unit 24 to the control unit 21, the rotation direction, rotation speed, and rotation amount (rotation angle) of the motor 11 are controlled. Thus, in one molding cycle, the forward / backward movement of the ejector rod (not shown) connected to the plate 15 is controlled.

[0033] The first storage unit 25 is a storage device for storing position information, etc., of the plate 15. In the first storage unit 25, the position of the plate 15 when it is moved in the X1 direction (first direction) by the ball screw 14 and detected by the proximity sensor 22 is stored as first position information. The first storage unit 25 also stores the position of the plate 15 when it is moved in the X2 direction (second direction) by the ball screw 14 and detected by the proximity sensor 22 as second position information. Furthermore, the first storage unit 25 stores information related to a defined range, which is used in the monitoring unit 29 to determine the magnitude of 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. Moreover, the information related to the defined range is not limited to being stored in the first storage unit 25; it may also be stored in the monitoring unit 29 or other storage units.

[0034] At the moment the detection signal is received from the detection unit 23, the first storage unit 25 stores the position information indicating the position of the tablet 15 sent from the position detection unit 12 as first position information. The same applies to the second position information. Furthermore, the first storage unit 25 can store either one set of first and second position information or multiple sets of first and second position information. Storing multiple sets of first and second position information means that the tablet 15 is continuously reciprocated multiple times, and the first and second position information are stored in association for each reciprocation.

[0035] As described above, the size of the detection area S of the proximity sensor 22 varies depending on the ambient temperature, power supply voltage, etc. Figure 2 The diagram shows the level change of the signal output from the proximity sensor 22 when the plate 15 is reciprocated in two directions (X1 and X2) in two detection areas S of different sizes. Figure 2 The figure above shows the signal level change when the detection area S of the proximity sensor 22 is large. Figure 2 The figure below shows the signal level change when the detection area S of the proximity sensor 22 is small. Furthermore, in Figure 2 In the upper and lower diagrams, the time axis of the timing diagram showing the signal level changes is consistent.

[0036] exist Figure 2 In the diagram, the detection area S of the proximity sensor 22 is shown using solid and dashed lines. Within the detection area S, the solid lines represent the range where the proximity sensor 22 is at an ON level, while the dashed lines represent the range where it is at an OFF level. Figure 2As shown, the signal output from the proximity sensor 22 becomes ON when the plate 15 moves closer to the proximity sensor 22 and enters the range of the solid line of the detection area S, and becomes OFF when the plate 15 moves away from the proximity sensor 22 and exceeds the range of the dashed line of the detection area S.

[0037] like Figure 2 As shown, when the plate 15, which has moved from the base point side (X2 side) towards the X1 direction, is detected by the proximity sensor 22 at position X11, the signal output from the proximity sensor 22 changes from an OFF level to an ON level at position X11. The position X11 of the plate 15 when it is detected by the proximity sensor 22 is stored in the first storage unit 25 as first position information. When the plate 15 moves further away from the proximity sensor 22 towards the X1 direction and becomes undetectable by the proximity sensor 22, the signal output from the proximity sensor 22 changes from an ON level to an OFF level.

[0038] On the other hand, when the plate 15, which has moved from the endpoint side (X1 side) towards the X2 direction, is detected by the proximity sensor 22 at position X21, the signal output from the proximity sensor 22 changes from an OFF level to an ON level at position X21. The position X21 of the plate 15 when it is detected by the proximity sensor 22 is stored in the first storage unit 25 as second position information. When the plate 15 moves further away from the proximity sensor 22 in the X2 direction and becomes undetectable by the proximity sensor 22, the signal output from the proximity sensor 22 changes from an ON level to an OFF level.

[0039] In addition, for in Figure 2 The relationship between the size of the detection area S in the upper and lower figures and the level change of the signal output from the proximity sensor 22 will be described later.

[0040] The calculation unit 26 calculates the fixed-point position of the detection area S of the proximity sensor 22 during position offset monitoring based on the first position information and the second position information stored in the first storage unit 25, and uses this as the fixed-point position information. Figure 2 The image above shows the location of reference numeral X01. Figure 2 The figure below shows the position of reference numeral X02. Hereinafter, fixed positions X01 and X02 will also be collectively referred to as "fixed position X0k". In the calculation unit 26, the fixed position X0k is calculated as the average of the position of the plate 15 represented by the first position information and the position of the plate 15 represented by the second position information. The fixed position information calculated by the calculation unit 26 is sent to the monitoring unit 29.

[0041] Furthermore, when the calculation unit 26 calculates the fixed-point location information based on multiple sets of first and second location information, and the first storage unit 25 contains the required number of first and second location information sets, the calculation unit 26 calculates the fixed-point location information based on these location information sets. For example, for multiple sets of first and second location information sets, the fixed-point location can be calculated separately for each set, and the average value of the multiple fixed-point locations can be used as the final fixed-point location information.

[0042] For example, in Figure 2 In the above figure, when the plate 15, which has moved in the X1 direction, is detected by the proximity sensor 22 at position X11, it will move from the base point ( Figure 1 The distance from position X00 to position X11 is set to 500mm. Then, after turning back at the endpoint, the plate 15, which has moved in the X2 direction, is detected by the proximity sensor 22 at position X21. The distance from the base point to position X21 is set to 800mm. In this case, the fixed position X01 calculated by the calculation unit 26 is 650mm.

[0043] Similarly, in Figure 2 In the figure below, when the plate 15, which has moved in the X1 direction, is detected by the proximity sensor 22 at position X12, the distance from the base point to position X12 is set to 600 mm. Then, when the plate 15, which has turned back at the endpoint and moved in the X2 direction, is detected by the proximity sensor 22 at position X22, the distance from the base point to position X22 is set to 700 mm. In this case, the fixed position X02 calculated by the calculation unit 26 is 650 mm.

[0044] like Figure 2 As shown, even when the size of the detection area S of the proximity sensor 22 changes due to ambient temperature, power supply voltage, etc., as long as the shape of the detection area S is linearly symmetrical with respect to the reference axis CX, the fixed point position X0k remains the same regardless of the size of the detection area S (X01=X02). This applies not only to situations like... Figure 2 As shown, when the distances L1 and L2 between the plate 15 and the proximity sensor 22 are the same and the size of the detection area S of the proximity sensor 22 changes, the same characteristic applies when the size of the detection area S is the same and the distances L1 and L2 between the plate 15 and the proximity sensor 22 change (L1 > L2 or L1 < L2).

[0045] Here, for comparison, the action of the proximity sensor 22 when the plate 15 is moved in one direction will be explained. Figure 3The diagram shows the level change of the signal output from the proximity sensor 22 when the plate 15 is moved in one direction (e.g., the X1 direction). Figure 3 The figure above shows the signal level change when the detection area S of the proximity sensor 22 is large. Figure 3 The figure below shows the signal level change when the detection area S of the proximity sensor 22 is small. Figure 3 In both the upper and lower diagrams, the time axis of the timing diagram showing the signal level changes is consistent.

[0046] exist Figure 3 In the diagram above, when the plate 15, which has moved from the base point towards direction X1, is detected by the proximity sensor 22 at position X11, the signal output from the proximity sensor 22 changes from an OFF level to an ON level at position X11. In this detection example, position X11 when the plate 15 is detected by the proximity sensor 22 is the first position information. Subsequently, when the plate 15 moves away from the proximity sensor 22 towards direction X1 and becomes undetectable by the proximity sensor 22, the signal output from the proximity sensor 22 changes from an ON level to an OFF level. In this detection example, position X11a where the plate 15, having moved towards direction X1, is no longer detectable by the proximity sensor 22 is the second position information.

[0047] exist Figure 3 In the action example shown in the above figure, if the average value of the position X11 of the plate 15 represented by the first position information and the position X11a of the plate 15 represented by the second position information is calculated, then the fixed position is X01a. Here, although in Figure 3 The above figure does not show the position, but if the position where the plate 15 is detected by the proximity sensor 22 when the proximity sensor 22 moves from the end point side (X1 side) to the X2 direction is set to the position where the plate 15 is detected by the proximity sensor 22, the position where the plate 15 is detected by the proximity sensor 22 is set to the position where the plate 15 is detected by the proximity sensor 22 when the plate 15 moves from the end point side (X1 side) to Figure 2 If the position is the same as X21 in the above diagram, then the difference is D1. The difference refers to the difference between the position where the signal level becomes ON when the plate 15 moves closer to the proximity sensor 22 and the position where the signal level becomes OFF when the plate 15 moves away from the proximity sensor 22. The impact of the difference will be described later.

[0048] On the other hand, Figure 3In the figure below, when the plate 15, which has moved from the base point in the X1 direction, is detected by the proximity sensor 22 at position X12, the signal output from the proximity sensor 22 changes from an OFF level to an ON level at position X12. In this detection example, position X12 when the plate 15 is detected by the proximity sensor 22 is the first position information. Subsequently, when the plate 15 moves away from the proximity sensor 22 in the X1 direction and becomes undetectable by the proximity sensor 22, the signal output from the proximity sensor 22 changes from an ON level to an OFF level. In this detection example, position X12a, where the plate 15, which has moved in the X1 direction, is no longer detectable by the proximity sensor 22, is the second position information.

[0049] exist Figure 3 In the action example shown in the figure below, if the average value of the position X12 of the plate 15 represented by the first position information and the position X12a of the plate 15 represented by the second position information is calculated, then the fixed position is X02a. Here, although in Figure 3 The figure below is not shown, but if the position where the plate 15 is detected by the proximity sensor 22 when the proximity sensor 22 moves from the end point side (X1 side) to the X2 direction is set to the position of the plate 15, the position where the proximity sensor 22 is detected by the proximity sensor 22 is the same as the position where the plate 15 is moved from the end point side (X1 side) to the X2 direction, the position of the plate 15 is the same as the position where the proximity sensor Figure 2 If the same position X22 is shown in the image below, then the difference should be D2.

[0050] If comparison Figure 3 The fixed position X01a calculated under the conditions in the upper figure and the fixed position X02a calculated under the conditions in the lower figure are not the same. The change in position offset is half the amount of the difference (D1-D2). This is because the difference changes proportionally to the change in the size of the detection area S (D1>D2). If the fixed position is calculated based on the first and second position information detected when the plate 15 is moved in one direction, the fixed position will shift due to the difference when the size of the detection area S changes. Thus, in this detection example, the detection accuracy of the position offset of the plate 15 will decrease when the size of the detection area S changes due to the influence of ambient temperature, power supply voltage, etc.

[0051] On the other hand, in this embodiment, such as Figure 2 As shown, the calculation unit 26 calculates the fixed position based on the first position information and the second position information detected when the plate 15 reciprocates in two directions. Therefore, even if the size of the detection area S changes, the fixed position can be accurately calculated without being affected by the difference, thus improving the detection accuracy of the positional offset of the plate 15.

[0052] Back to Figure 1The following explanation will be provided. The second storage unit 27 stores the fixed-point position information calculated by the calculation unit 26 during fixed-point position calibration as reference fixed-point position information. Fixed-point position calibration refers to the operation of registering the correct fixed-point position as a reference before performing the operation of monitoring the deviation of the fixed-point position. For example, when installing the demolding device 1, the following example can be given: When installing the demolding device 1, after adjusting each part of the power transmission unit 13 to a normal state, the plate 15 can be experimentally reciprocated once or multiple times to detect the first position information and the 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 time.

[0053] Furthermore, the reference point position information does not necessarily have to be a value calculated by the calculation unit 26. An external measuring device can also be used during calibration to measure the distance from the base point X00 to the reference axis CX (see reference 2000). Figure 2 The distance is measured and the result is stored in the second storage unit 27 as reference fixed-point position information. An external measuring device, such as a laser displacement meter, can be used. Alternatively, the base point X00 of the position detection unit 12 can be set while the plate 15 is stopped at 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 only 0 needs to be recorded in the second storage unit 27.

[0054] The fixed-point selection unit 28 switches the connection between the calculation unit 26 and the second storage unit 27, as well as the connection between the calculation unit 26 and the monitoring unit 29. When the connection between the calculation unit 26 and the second storage unit 27 is switched in the fixed-point selection unit 28, the reference fixed-point position information calculated by the calculation unit 26 is stored in the second storage unit 27 during fixed-point position calibration. On the other hand, when the connection between the calculation unit 26 and the monitoring unit 29 is switched in the fixed-point selection unit 28, the point position information calculated by the calculation unit 26 is sent to the monitoring unit 29 during position offset monitoring.

[0055] 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 exceeds a predetermined range. If the monitoring unit 29 determines that the deviation between the fixed-point position information obtained from the calculation unit 26 and the reference fixed-point position information obtained from the second storage unit 27 is within the predetermined range, it notifies the upstream device (not shown) controlling the injection molding machine that it is normal (no positional offset of the plate 15). On the other hand, if the monitoring unit 29 determines that the deviation between the fixed-point position information obtained from the calculation unit 26 and the reference fixed-point position information obtained from the second storage unit 27 exceeds the predetermined range, that is, if it determines that the positional offset of the plate 15 exceeds the allowable value, it notifies the upstream device controlling the injection molding machine that there is an anomaly (positional offset of the plate 15 exists). Then, the upstream device performs the prescribed anomaly handling.

[0056] Next, the process of detecting the positional offset of the plate 15 in the demolding device 1 of this embodiment will be described. Figure 4 This is a flowchart illustrating the process of detecting the positional offset of the plate 15 in the demolding device 1 of this embodiment.

[0057] Furthermore, the reciprocating motion of the plate 15 caused by the ball screw 14 is executed by sending an action command generated by the command generation unit 24 to the control unit 21, so the description is omitted here.

[0058] In step S101, the detection unit 23 determines whether the signal output from the proximity sensor 22 changes from an OFF level to an ON level. If the detection unit 23 determines in step S101 that the signal output from the proximity sensor 22 has changed from an OFF level to an ON level, the process proceeds to step S102. On the other hand, if the detection unit 23 determines in step S101 that the signal output from the proximity sensor 22 has not changed from an OFF level to an ON level, the process proceeds to step S101.

[0059] In step S102 (step S101: "Yes"), the detection unit 23 sends a detection signal to the instruction generation unit 24 and the first storage unit 25. As a result, the first position information is stored in the first storage unit 25.

[0060] In step S103, the detection unit 23 determines whether the signal output from the proximity sensor 22 changes from an OFF level to an ON level. If the detection unit 23 determines in step S103 that the signal output from the proximity sensor 22 has changed from an OFF level to an 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 an OFF level to an ON level, the process proceeds to step S103.

[0061] In step S104 (step S103: "Yes"), the detection unit 23 sends a detection signal to the instruction generation unit 24 and the first storage unit 25. As a result, the second position information is stored in the first storage unit 25.

[0062] In step S105, the calculation unit 26 determines whether the required quantity of first position information and second position information is stored in the first storage unit 25. If the calculation unit 26 determines in step S105 that the required quantity of first position information and second position information is 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 quantity of first position information and second position information is not stored in the first storage unit 25, the process proceeds to step S101.

[0063] In step S106, the calculation unit 26 calculates the fixed position of the detection area S of the proximity sensor 22 during position offset monitoring based on the first position information and the second position information stored in the first storage unit 25, and sends it as fixed position information to the monitoring unit 29.

[0064] 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 exceeds a predetermined 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 exceeds the predetermined 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 exceed the predetermined range, the process proceeds to step S109.

[0065] In step S108 (step S107: "Yes"), the monitoring unit 29 notifies the upstream device controlling the injection molding machine of an abnormality (positional offset of the plate 15). After step S108 is completed, the processing of this flowchart ends.

[0066] In step S109 (step S107: "No"), the monitoring unit 29 notifies the upstream device controlling the injection molding machine that everything is normal (there is no positional offset of the plate 15). After step S109 is completed, the processing of this flowchart ends. Alternatively, if in step S107 the monitoring unit 29 determines that the deviation between the fixed-point position information and the reference fixed-point position information does not exceed a specified range, the processing of this flowchart may also end without the monitoring unit 29 notifying the upstream device controlling the injection molding machine that everything is normal.

[0067] The monitoring device 2 for the moving body according to the above embodiment has the following effects, for example.

[0068] In the moving body monitoring device 2 of this embodiment, the calculation unit 26 calculates the fixed position based on the first position information and the second position information detected when the plate (moving body) 15 reciprocates in two directions. Therefore, even if the size of the detection area S of the proximity sensor 22 changes, the fixed position can be calculated accurately without being affected by the strain. Accordingly, even if the size of the detection area S changes according to the ambient temperature, power supply voltage, etc., the fixed position can be calculated accurately without being affected by the strain, thus further improving the detection accuracy of the positional deviation of the plate 15.

[0069] Here, a specific example will be explained. At the location where the demolding device is installed, with an ambient temperature difference of 40°C throughout the year, the absolute value of the rate of change of the detection distance (operation range) of the proximity sensor is set to 12%. Furthermore, when one side of a commonly available, inexpensive square proximity sensor is set to 17mm and the length of this side is used as the reference for the detection distance, the maximum variation in the detection distance due to ambient temperature is approximately 17mm × 0.12 ≈ 2mm. Additionally, when the proximity sensor's tolerance is set to 10% of the detection distance, the error in the detected position due to the tolerance when the moving object moves in one direction is 2mm × 0.10 × 1 / 2 = 0.1mm.

[0070] On the other hand, in the demolding device used in a small injection molding machine, when the number of teeth on the driven pulley is set to 40 and the ball screw travel pitch is set to 10 mm, the travel of the ball screw for each tooth of the driven pulley is 10 / 40 = 0.25 mm. If this value is set as the minimum positional offset to be detected, the positional offset cannot be detected with high precision when errors caused by variations in the detection distance exist. However, the moving body monitoring device 2 according to this embodiment can eliminate errors caused by variations in the detection distance, thus further improving the detection accuracy of the moving body's positional offset.

[0071] According to the moving body monitoring device 2 of this embodiment, a proximity sensor is used as a sensor to detect that the plate 15 has passed through a specific position, so that the positional shift of the plate 15 can be determined with an inexpensive unit.

[0072] According to the monitoring device 2 for the moving body in this embodiment, the monitoring unit 29 determines whether the deviation between the fixed-point position information calculated based on one or more first position information and second position information and the reference fixed-point position information calculated during fixed-point position calibration exceeds a predetermined range. Therefore, the influence of the deviation in the fixed-point position information calculated by the calculation unit 26 can be eliminated, and thus the presence or absence of positional offset of the plate 15 can be determined more accurately.

[0073] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. Various modifications and alterations can be made as described below, and these are also included within the technical scope of the present invention. Furthermore, the effects described in the embodiments are merely examples of the best effects produced by the present invention and are not limited to the contents described in the embodiments. The above embodiments and the following modifications can also be appropriately combined, but detailed descriptions are omitted.

[0074] (Deformation method)

[0075] In this embodiment, an example of outputting a detection signal for the plate (moving body) 15 when the signal output from the proximity sensor 22 in the detection unit 23 changes from an OFF level to an ON level has been described, but this is not a limitation. It is also possible to output a detection signal for the plate 15 when the signal output from the proximity sensor 22 changes from an ON level to an OFF level.

[0076] In this embodiment, an example of a proximity sensor 22 for detecting the position offset of the plate 15 being provided near the ball screw 14 has been described, but it is not limited to this. Alternatively, the proximity sensor 22 could be shared with the proximity sensor used for confirming the retraction of the ejector rod (not shown). This configuration reduces the cost of the monitoring device.

[0077] Explanation of reference numerals in the attached figures

[0078] 1: Demolding device; 2: Monitoring device for moving body; 10: Movable mechanism; 11: Motor; 12: Position detection unit; 13: Power transmission unit; 14: Ball screw; 15: Flat plate (moving body); 20: Control device; 21: Control unit; 22: Proximity sensor; 23: Detection unit; 24: Command generation unit; 25: First storage unit; 26: Calculation unit; 27: Second storage unit; 28: Fixed position selection unit; 29: Monitoring unit.

Claims

1. A monitoring device for a moving body, the moving body reciprocating along a moving direction in a first direction and a second direction, the second direction being opposite to the first direction, the monitoring device comprising: The position detection unit detects the position of the moving object and outputs the position of the moving object as position information. A proximity sensor is used to detect when a moving object has passed through a specific location; The first storage unit stores the position of the moving body in the direction of movement when the proximity sensor detects the moving body that has moved in the first direction as first position information, and stores the position of the moving body in the direction of movement when the proximity sensor detects the moving body that has moved in the second direction as second position information. The computing unit calculates a fixed position in the direction of movement of the detection area of ​​the proximity sensor during monitoring, based on at least one first position information and at least one second position information stored in the first storage unit, as fixed position information. The second storage unit stores reference fixed-point location information; as well as 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 storage unit exceeds a predetermined range when monitoring a moving body, the monitoring unit determines that the positional offset of the moving body in the direction of movement exceeds the allowable value.

2. The monitoring device for a moving body according to claim 1, wherein, The second storage unit stores the fixed-point position information calculated by the calculation unit during fixed-point position calibration as the reference fixed-point position information.

3. The monitoring device for a moving body according to claim 1 or 2, wherein, When the proximity sensor detects that a moving object moving in the first direction has entered the detection area of ​​the proximity sensor, the first storage unit stores the position of the moving object at this time as first position information. When the proximity sensor detects that a moving object moving in the second direction has entered the detection area of ​​the proximity sensor, the first storage unit stores the position of the moving object at this time as second position information.

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