Gas spring maintenance and management devices, robot systems, and gas spring maintenance and management methods

Abstract

This invention provides a maintenance management device (1), a robot system, and a maintenance management method for gas springs, which can determine appropriate maintenance based on the amount of reduction in gas pressure. The maintenance management device (1) manages the maintenance of gas springs installed on the arm of a multi-joint robot. The maintenance management device includes: a gas pressure measuring unit (11) that periodically measures the gas pressure inside the gas spring; a maintenance judgment unit (12) that determines whether the gas spring is abnormal based on the amount of reduction in gas pressure per unit time or per unit working distance; and a notification unit (13) that notifies the operator of the judgment result based on the maintenance judgment unit.

Description

Technical Field

[0001] This invention relates to a maintenance and management device for gas springs, a robot system, and a maintenance and management method for gas springs. Background Technology

[0002] A known robot incorporates a gas spring as a pneumatic balancer (see, for example, Patent Documents 1 and 2). A load, caused by gravity acting on the robot arm, acts on a servo motor that drives the robot arm to rotate about a horizontal axis. The pneumatic balancer is provided to reduce the load on the servo motor caused by gravity. The gas spring has a cylinder filled with gas and a piston rod that compresses the gas within the cylinder, generating a rebound force through gas compression. As the piston rod moves relative to the cylinder, the gas pressure inside the cylinder gradually decreases.

[0003] Various methods for detecting a decrease in gas pressure have been proposed (see, for example, Patent Documents 1-4). For instance, in Patent Document 2, the amount of decrease in gas pressure inside the cylinder is estimated based on the difference between the current value of the servo motor and the reference current value.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-159402

[0007] Patent Document 2: Japanese Patent Application Publication No. 2014-195849

[0008] Patent Document 3: Japanese Patent Application Publication No. 2007-098494

[0009] Patent Document 4: Japanese Patent Application Publication No. 08-313322 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] As mentioned above, even in a normal gas spring, the gas pressure will gradually decrease. Therefore, as routine maintenance, the gas spring needs to be periodically refilled with gas. On the other hand, there are cases where the gas pressure decreases due to a malfunction of the gas spring. In this case, the gas spring needs to be replaced, rather than refilling the cylinder with gas. Thus, while appropriate maintenance varies depending on the condition of the gas spring, it is difficult to determine appropriate maintenance based solely on the amount of gas pressure reduction.

[0012] Solution for solving the problem

[0013] One aspect of the present invention is a maintenance management device for managing the maintenance of gas springs installed on the arm of a multi-joint robot. The maintenance management device includes: a gas pressure measuring unit that periodically measures the gas pressure inside the gas spring; a maintenance judgment unit that determines whether the gas spring is abnormal based on the amount of decrease in gas pressure per unit time or per unit working distance; and a notification unit that notifies the operator of the judgment result based on the judgment result of the maintenance judgment unit. Attached Figure Description

[0014] Figure 1 This is an overall structural diagram of a robot system implemented in one way.

[0015] Figure 2 This is a graph illustrating the relationship between the torque Tg generated by the gas spring and the torque Ts generated by the servo motor.

[0016] Figure 3 This is a structural diagram of a maintenance and management device for one implementation method.

[0017] Figure 4 (a) is a graph showing the change in gas pressure relative to the working distance of the gas spring, and (b) is a magnified graph of region E in (a).

[0018] Figure 5 This is a cross-sectional view showing a structural example of a gas spring.

[0019] Figure 6 This is a flowchart illustrating the maintenance and management methods for gas springs.

[0020] Explanation of reference numerals in the attached figures:

[0021] 1: Maintenance and management device

[0022] 2: Multi-joint robots

[0023] 3: Gas spring

[0024] 4: Robotics Mechanism Department

[0025] 4c: Lower arm

[0026] 5: Control device

[0027] 6: Servo motor

[0028] 10: Robotic Systems

[0029] 11: Gas Pressure Measurement Section

[0030] 12: Maintenance Judgment Department

[0031] 13: Notification Department Detailed Implementation

[0032] The following description, with reference to the accompanying drawings, describes a gas spring maintenance and management device 1 and a robot system 10 according to one embodiment of the present invention.

[0033] like Figure 1 As shown, the robot system 10 includes a multi-joint robot 2 and a maintenance management device 1, which manages the maintenance of the gas springs 3 installed on the multi-joint robot 2.

[0034] The multi-joint robot 2 includes: a robot mechanism 4 having at least one arm; a gas spring 3 connected to the at least one arm; and a control device 5 that controls the robot mechanism 4. A maintenance and management device 1 is disposed in the control device 5.

[0035] One example of the robot mechanism 4 is a vertical multi-joint robot, which includes: a base 4a; a rotating part 4b rotatably mounted on the base 4a; a lower arm 4c rotatably mounted on the rotating part 4b; an upper arm 4d rotatably mounted on the lower arm 4c; and a wrist part 4e disposed at the front end of the upper arm 4d. In this embodiment, the robot mechanism 4 is a welding robot, and a welding tool 4f is mounted on the wrist part 4e.

[0036] A servo motor is installed in the robot mechanism section 4, which drives the rotating part 4b and the arms 4c and 4d. The control device 5 is connected to the robot mechanism section 4 via a power supply cable 7 and controls the operation of each servo motor.

[0037] The servo motor 6, which rotates around a horizontal axis, is subjected to a load caused by gravity acting on the lower arm 4c. The gas spring 3 serves as a pneumatic balancer to reduce the load on the servo motor 6 caused by gravity.

[0038] like Figure 1 and Figure 5 As shown, the gas spring 3 has a cylinder 3a and a piston rod 3b. An inert and compressible gas is sealed inside the cylinder 3a. The piston rod 3b can slide within the cylinder 3a, compressing the gas inside. The cylinder 3a is rotatably mounted on a lower arm 4c, and the piston rod 3b is rotatably mounted on a rotating part 4b. As the lower arm 4c rotates, the insertion depth of the piston rod 3b into the cylinder 3a changes; as the insertion depth of the piston rod 3b into the cylinder 3a increases, the gas pressure inside the cylinder 3a increases.

[0039] Figure 2This illustrates the torque required to control the displacement and speed of the lower arm 4c under predetermined conditions. Graph (A) shows the state where the gas spring 3 is filled with an appropriate amount of gas, and graph (B) shows the state where the gas pressure of the gas spring 3 decreases due to gas leakage. Since the gas spring is used as a pneumatic balancer, the torque Tr required to drive the lower arm 4c is the sum of the torque Ts generated by the servo motor 6 and the torque Tg generated by the gas spring 3. The higher the gas pressure of the gas spring 3, the greater the torque Tg. In (B), the torque Tg of the gas spring 3 decreases by ΔTs due to gas leakage; therefore, to obtain the predetermined torque Tr, the torque Ts of the servo motor 6 needs to be increased by ΔTs.

[0040] like Figure 3 As shown, the maintenance management device 1 includes: a gas pressure measuring unit 11, which periodically measures the gas pressure inside the gas spring 3; a maintenance judgment unit 12, which determines whether the gas spring 3 is malfunctioning based on the amount of gas pressure decrease per unit time or per unit working distance; a notification unit 13, which notifies the operator of the judgment result based on the judgment result of the maintenance judgment unit 12; and a storage unit 14, which has RAM, ROM, and other arbitrary storage devices. The maintenance management device 1 has a processor, and the following processes of the gas pressure measuring unit 11, the maintenance judgment unit 12, and the notification unit 13 are executed by the processor.

[0041] As described above, there is a correlation between the torque Ts of the servo motor 6 and the gas pressure inside the gas spring 3. The gas pressure measuring unit 11 obtains the current value of the servo motor 6 from the control unit within the control device 5 that controls the servo motor 6. Next, based on a predetermined relationship between the current value of the servo motor 6 and the gas pressure, the gas pressure measuring unit 11 converts the current value of the servo motor 6 into gas pressure, thereby indirectly measuring the gas pressure based on the current value. The measured gas pressure values ​​are stored in the storage unit 14 in a time sequence.

[0042] Figure 4 (a) shows an example of how gas pressure changes over time. Figure 4 In the graph (a), the left half (before gas filling) shows the normal decrease in gas pressure when the gas spring 3 is functioning normally, and the right half (after gas filling) shows the decrease in gas pressure when the gas spring 3 experiences a sealing performance abnormality. Since the gas inside the gas spring 3 will leak during use even under normal conditions, the gas pressure gradually decreases from the initial value Pi as the working distance of the gas spring 3 increases.

[0043] The gas pressure varies depending on the position and orientation of the robot mechanism 4. Therefore, preferably, the gas pressure measuring unit 11 measures the gas pressure when the robot mechanism 4 is positioned in a predetermined position and orientation. For example, when the gas pressure measuring unit 11 performs the gas pressure measurement, the control device 5 can control the robot mechanism 4 to position it in the predetermined position and orientation.

[0044] The frequency of gas pressure measurement is appropriately set according to the working conditions of the articulated robot 2. For example, the gas pressure measuring unit 11 measures the gas pressure once a week or once a month. Alternatively, the gas pressure measuring unit 11 measures the gas pressure whenever the working distance increases by a predetermined distance.

[0045] Each time the gas pressure is measured by the gas pressure measuring unit 11, the maintenance judgment unit 12 calculates the decrease in gas pressure per unit time or per unit working distance, i.e., the decrease rate ΔP / ΔD. An example of a unit time is the length of the predetermined working time of the robot mechanism unit 4, and an example of a unit working distance is the predetermined working distance of the gas spring 3. The working distance of the gas spring 3 is calculated based on the total movement of the lower arm 4c. For example, ΔP is the difference between the gas pressure measured this time and the gas pressure measured last time, while ΔD is the difference between the working distance measured this time and the working distance measured last time.

[0046] Next, the maintenance judgment unit 12 determines whether the gas spring 3 is malfunctioning by comparing the reduction rate ΔP / ΔD with a predetermined threshold C. Furthermore, based on the determination of whether or not a malfunction has occurred, the maintenance judgment unit 12 determines the maintenance that should be performed on the gas spring 3.

[0047] The threshold C is a value set based on the rate of decrease in gas pressure caused by normal gas leakage. For example... Figure 4 As shown in the left half of (a), in the case of a gas pressure decrease caused solely by normal gas leakage, the gas pressure decreases relative to the working distance at a roughly constant rate of decrease ΔP / ΔD, and this rate of decrease ΔP / ΔD is below the threshold C. On the other hand, as... Figure 4 As shown in the right half of (a), when the sealing performance of the gas spring 3 is abnormal, the gas pressure decreases more rapidly with the increase of the working distance, the rate of decrease ΔP / ΔD gradually increases, and the rate of decrease ΔP / ΔD becomes greater than the threshold C. Figure 4 (b) is Figure 4 (a) Enlarged view of region E.

[0048] When the reduction rate ΔP / ΔD is below the threshold C, the maintenance judgment unit 12 determines that the gas spring 3 is not abnormal, and determines that the maintenance to be performed is to refill the gas. Next, assuming that the gas pressure continues to decrease at the reduction rate ΔP / ΔD, the maintenance judgment unit 12 calculates the remaining time until the gas pressure decreases to a predetermined threshold Pth. The threshold Pth is the lower limit of the gas pressure required to output the torque Tg required by the gas spring 3 as a pneumatic balancer. The remaining time can be the working distance of the gas spring 3 until the gas pressure decreases to the threshold Pth or the working time of the robot mechanism 4.

[0049] On the other hand, when the reduction rate ΔP / ΔD is greater than the threshold C, the maintenance judgment unit 12 determines that the gas spring 3 is abnormal and determines that the maintenance to be performed is to replace the gas spring 3.

[0050] Figure 5 An example of the structure of the gas spring 3 is shown. The sealing performance inside the cylinder 3a is mainly achieved by the rod seal 3c. Due to scratches on the surface of the piston rod 3b, or foreign objects stuck between the piston rod 3b and the rod seal 3c, the sealing performance between the piston rod 3b and the rod seal 3c is reduced, thereby causing abnormal sealing performance of the gas spring 3.

[0051] For example, foreign matter generated by the operation of the robot mechanism 4, such as spatter from welding, may sometimes adhere to the surface of the exposed piston rod 3b. Normally, the intrusion of foreign matter into the gas spring 3 is prevented by the dust seal 3d. However, foreign matter may sometimes pass through the dust seal 3d and intrude between the piston rod 3b and the rod guide 3e, scratching the surface of the piston rod 3b. Additionally, foreign matter such as abrasive particles generated by the sliding of the gas spring 3 components may sometimes become trapped between the piston rod 3b and the rod seal 3c.

[0052] In addition, factors such as aging over the years, heat-induced deterioration, or chemical corrosion caused by foreign objects may also reduce the sealing performance of the rod seal 3c.

[0053] exist Figure 5 In the figure, reference numeral 3f is a piston guide bearing that guides the piston rod 3b to slide within the cylinder 3a, reference numeral 3g is a one-way valve for filling the cylinder 3a with gas, and reference numeral 3h represents lubricating oil.

[0054] When it is determined that the gas spring 3 is not malfunctioning, the notification unit 13 notifies the operator about the remaining time. For example, the notification unit 13 displays an instruction on the operation panel 5a of the control device 5 to fill the gas spring 3 with gas within the remaining time. On the other hand, when it is determined that the gas spring is malfunctioning, the notification unit 13 notifies the operator about replacing the gas spring 3. For example, the notification unit 13 displays an instruction on the operation panel 5a to replace the gas spring 3 immediately. Instead of the operation panel 5a, the notification unit 13 may also display the above instructions on the display of the portable teaching operation panel (not shown) of the control device 5.

[0055] Next, refer to Figure 6 The maintenance and management method for the gas spring 3 performed by the maintenance and management device 1 will be described.

[0056] The gas pressure measuring unit 11 periodically measures the gas pressure inside the gas spring 3 (step S1). After measuring the gas pressure, the maintenance judgment unit 12 calculates the amount of gas pressure reduction per unit time or per unit working distance, i.e., the reduction rate ΔP / ΔD (step S2). Based on the reduction rate ΔP / ΔD, it determines whether the gas spring 3 is abnormal and what maintenance should be performed on the gas spring 3 (step S3).

[0057] Specifically, when the reduction rate ΔP / ΔD is below the threshold C (Yes in step S3), the maintenance judgment unit 12 determines that the gas spring 3 is not abnormal and that the maintenance to be performed is to fill the gas (step S4), and calculates the remaining time until the gas pressure drops to the threshold Pth (step S5). Then, the notification unit 13 notifies the operators about the remaining time (step S6).

[0058] Based on the notification, the operator fills the cylinder 3a with gas from the one-way valve 3g within the remaining time until the gas pressure inside the cylinder 3a returns to the initial value Pi.

[0059] On the other hand, when the reduction rate ΔP / ΔD is greater than the threshold C (No in step S3), the maintenance judgment unit 12 determines that the gas spring 3 is abnormal and that the maintenance to be performed is to replace the gas spring 3 (step S7). Then, the notification unit 13 notifies the operators about replacing the gas spring 3 (step S8).

[0060] Based on the notification, the operators quickly replaced gas spring 3 with a new gas spring 3.

[0061] As described above, since the gas pressure of the gas spring 3 gradually decreases as the robot mechanism 4 operates, it is necessary to periodically refill the gas spring 3 as part of routine maintenance. Therefore, it is assumed that when the operator is notified of the gas pressure decrease or the amount of decrease, the operator first refills the gas spring 3 with gas. However, if the sealing performance of the gas spring 3 malfunctions, the gas pressure will immediately drop due to a rapid gas leak after the robot mechanism 4 resumes operation, even though it has just been refilled. At this point, the operator will notice the abnormality in the gas spring 3 and replace it. In this situation, time and maintenance are wasted, and the downtime of the production line due to the maintenance of the articulated robot 2 is prolonged.

[0062] In contrast, according to this embodiment, based on the gas pressure reduction rate ΔP / ΔD, it is determined whether the gas pressure reduction is caused by normal gas leakage or by an abnormality in the sealing performance of the gas spring 3. Furthermore, the appropriate maintenance notification corresponding to the cause of the gas pressure reduction is sent to the operator. Based on the notification, the operator can identify whether the gas pressure reduction is normal or abnormal, and can perform appropriate maintenance on the gas spring 3 without hesitation.

[0063] In addition, when the gas spring 3 experiences abnormal sealing performance, the abnormality of the gas spring can be detected in advance based on the reduction rate ΔP / ΔD, and the necessity of replacing the gas spring 3 can be notified to the operators in advance.

[0064] In addition, when the gas springs are functioning normally, the remaining time that the articulated robot 2 can operate normally is communicated to the operator. Based on the communicated remaining time, the operator can perform maintenance on the gas springs 3 in a planned manner.

[0065] The gas pressure measured by the gas pressure measuring unit 11 varies depending on the temperature inside the cylinder 3a. Therefore, the maintenance judgment unit 12 can also convert the measured gas pressure into the gas pressure at a predetermined temperature and use the gas pressure at the predetermined temperature to calculate the reduction rate ΔP / ΔD.

[0066] For example, the maintenance judgment unit 12 obtains the temperature T around the gas spring 3 from the temperature sensor installed on the gas spring 3, and converts the measured gas pressure P into the gas pressure P at 20°C according to the following formula (20).

[0067] P(20)=P×(273.15+T) / (273.15+20)

[0068] In the above embodiment, the gas pressure measuring unit 11 indirectly measures the gas pressure based on the current value of the servo motor 6. Alternatively, other means can be used to measure the gas pressure. For example, the gas pressure measuring unit 11 may also include a pressure sensor disposed inside the cylinder 3a, and the gas pressure may be measured directly using the pressure sensor.

[0069] In the above embodiments, the maintenance management device 1 is disposed within the control device 5. Alternatively, the maintenance management device 1 can be a separate device from the control device 5. For example, the maintenance management device 1 can also be a computer connected to the control device 5.

[0070] Alternatively, a portion of the functions of the maintenance management device 1 can be housed in a higher-level control system connected to multiple articulated robots 2. For example, a gas pressure measuring unit 11 can be installed on each articulated robot 2, while a maintenance judgment unit 12 and a notification unit 13 can be installed in the higher-level control system.

[0071] The upper control system receives gas pressure data from each of the multiple articulated robots 2 and makes judgments on the presence and maintenance of the gas springs 3 of each articulated robot 2.

[0072] In this way, by having a single upper-level control system manage the maintenance information of the gas springs 3 installed on multiple jointed robots 2, operators can perform maintenance on multiple gas springs 3 in a more planned manner, such as filling multiple gas springs 3 with gas at the same time.

Claims

1. A maintenance and management device, characterized in that, The maintenance management device manages the maintenance of the gas springs installed on the arm of the multi-joint robot, and the maintenance management device includes: A gas pressure measuring unit periodically measures the gas pressure inside the gas spring; The maintenance judgment unit determines whether the gas spring is abnormal and the type of maintenance required based on the amount of decrease in gas pressure per unit time or per unit working distance. as well as The notification department informs the operators of the judgment results based on those of the maintenance judgment department. The maintenance judgment unit determines that the gas spring is malfunctioning when the gas pressure drop exceeds a predetermined threshold, and determines that the maintenance required for the gas spring is to replace it; when the gas pressure drop is below the predetermined threshold, it determines that the gas spring is not malfunctioning, and determines that the maintenance required for the gas spring is to refill it with gas, and calculates the remaining time until the gas pressure drops to the predetermined threshold. The notification department will notify you of either the replacement of the gas spring or the remaining time.

2. A robot system, characterized in that, have: A multi-joint robot comprising: a robot mechanism having at least one arm; a gas spring disposed on the arm; and a control device for controlling the robot mechanism, wherein the gas spring serves as a pneumatic balancer to reduce the load on the servo motor driving the arm. as well as The maintenance management device according to claim 1 manages the maintenance of the gas spring.

3. A maintenance and management method, characterized in that, The maintenance management method manages the maintenance of the gas springs installed on the arm of a multi-joint robot, and the maintenance management method includes the following steps: Periodically measure the gas pressure inside the gas spring; Based on the amount of gas pressure reduction per unit time or per unit working distance, determine whether the gas spring is abnormal and the type of maintenance that should be performed. Notify the workers based on the judgment results. Determining whether the gas spring is malfunctioning includes: if the decrease in gas pressure is greater than a predetermined threshold, determining that the gas spring is malfunctioning and that the maintenance required is to replace the gas spring; if the decrease in gas pressure is less than the predetermined threshold, determining that the gas spring is not malfunctioning and that the maintenance required is to refill the gas spring, and calculating the remaining time until the gas pressure decreases to the predetermined threshold. Notify the user of the need to replace the gas spring, or notify the user of the remaining time.

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