Cooling device for a robot controller

Abstract

A cooling device of a robot controller capable of performing fine control based on the temperature of a heat generating element included in a servo driver is provided. The cooling device includes a heat sink member (42) to which the heat generating element (IPM 41) is attached, a temperature sensor (55), a heat conducting sheet (52) that transfers heat generated by the heat generating element to the temperature sensor (55), a fan (71, 72) that generates an air current toward the heat sink member (52), and a fan control section (73, 74) that controls the fan (71, 72) based on a detection value of the temperature sensor (55). The heat conducting sheet (52) is located between the circuit board (43) and the heat generating element in the servo driver (11) and is in contact with both the circuit board (43) and the heat generating element. The temperature sensor (55) is provided on the circuit board (43) in a manner covered by the heat conducting sheet (52).

Description

Technical Field

[0001] This invention relates to a cooling device for robot controllers. Background Technology

[0002] In industrial robots, a motor is installed on each axis of the manipulator (robot body) to drive that axis. The robot controller, which controls the manipulator, has a servo driver that drives and controls the motor corresponding to each axis. If the manipulator is an 8-axis manipulator, the robot controller also has 8 servo drivers. Because the motors installed on the manipulator are, for example, three-phase motors, the servo drivers have an inverter circuit that generates, for example, the three-phase AC power to be supplied to the corresponding motor via PWM (Pulse Width Modulation). The inverter circuit has a circuit with two switching elements, called a high-side switch and a low-side switch, connected in series for each phase of the motor. As switching elements, for example, semiconductor devices such as power MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) or IGBTs (Insulated-Gate Bipolar Transistors) are used. In recent years, IPMs (Intelligent Power Modules) have been widely used, which integrate multiple switching elements constituting the inverter circuit, gate drive circuits driving the gates of the switching elements, and protection circuits into a single package.

[0003] When an inverter circuit generates AC power to drive a motor, the switching elements within the inverter circuit generate heat. As semiconductor components, the switching elements require their junction temperature to remain below a specified maximum value. Therefore, a heat sink, also known as a radiator, is mounted on the switching elements, and airflow is directed along the heat sink by a cooling fan to cool the switching elements. Cooling is performed in the same way when using an IPM (Integrated Power Module). The cooling fan is driven by a motor called a fan motor. While this ensures the fan always operates at maximum airflow, this is disadvantageous from the perspective of power consumption and fan motor lifespan. Therefore, a solution is proposed to operate the fan at the necessary airflow when necessary. For example, Patent Document 1 discloses a solution where, when cooling an inverter circuit used in a servo drive, the heat generated is calculated based on instructions from the servo drive, and the fan's rotation is controlled to switch on / off and its speed. Patent Document 2 discloses a solution where the temperature is estimated by calculating the power consumed as heat in the switching elements based on the output current of the power conversion circuit, such as the inverter circuit, and the cooling fan is controlled based on the estimated temperature. Patent document 3 discloses a scheme that estimates the junction temperature of a switching element based on the output current from the inverter circuit, the airflow of the heat sink component, and the ambient temperature of the switching element, and controls the cooling fan based on the estimated junction temperature.

[0004] Electrolytic capacitors are frequently used for smoothing in power supply circuits, but they have the property of shortening their lifespan when the ambient temperature is high. Patent Document 4 discloses a solution where, when a cooling fan used for cooling semiconductor components also cools the electrolytic capacitor, the fan's airflow is controlled based on the relationship between the fan's airflow, the fan's lifespan, and the electrolytic capacitor's lifespan. Patent Document 5 discloses a solution that serves as a temperature sensor capable of accurately measuring the temperature of electronic components such as semiconductor components. A heat-conducting sheet is provided in close contact between the electronic component and the substrate on which it is mounted, or a heat sink mounted on the electronic component, and a heat-sensing element is provided on the heat-conducting sheet.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 6-117393

[0008] Patent Document 2: Patent No. 4796841

[0009] Patent Document 3: Patent No. 5486434

[0010] Patent Document 4: Patent No. 6498371

[0011] Patent Document 5: Japanese Patent Application Publication No. 2011-33479 Summary of the Invention

[0012] The technical problem that the invention aims to solve

[0013] When using a cooling fan to remove heat generated by a servo drive mounted on a robot controller, if the technology described in Patent Documents 1 to 4 is used, there is a technical problem that it is difficult to perform precise control of the cooling fan based on the actual temperature of the heat-generating element by only estimating the junction temperature of the switching element, which is the heat-generating element.

[0014] The purpose of this invention is to provide a cooling device for a robot controller, which is capable of precise control based on the temperature of the heat-generating elements contained in the servo drive within the robot controller.

[0015] Technical solutions adopted to solve technical problems

[0016] One aspect of the present invention provides a cooling device for a robot controller having a servo driver. The servo driver includes a circuit board and a heating element. The cooling device includes: a heat sink component mounted on the heating element; a temperature sensor; a heat-conducting plate that transfers heat generated by the heating element to the temperature sensor; a fan that generates airflow toward the heat sink component; and a fan control unit that controls the fan based on the detection value of the temperature sensor. The heat-conducting plate is located between the circuit board and the heating element in the servo driver and is in contact with both the circuit board and the heating element. The temperature sensor is disposed on the circuit board in an area covered by the heat-conducting plate.

[0017] In one aspect of the cooling device, heat is transferred to a temperature sensor mounted on the circuit board via a heat-conducting plate, allowing the temperature sensor to detect the actual temperature of the heat-generating element. This enables precise control of the cooling fan based on the actual temperature of the heat-generating element, resulting in reduced power consumption and extended fan lifespan.

[0018] In the cooling device, it is preferable that the fan control unit controls the airflow generated by the fan to ensure that the temperature measured by the temperature sensor does not exceed a predetermined value. Such control prevents the temperature of the heating element from rising excessively.

[0019] In a cooling system where the robot controller has multiple servo drives, the airflow generated by a single fan can be split and flow along the heat sink components of each of the multiple servo drives. This configuration reduces the number of fans and allows for efficient use of space within the robot controller, enabling miniaturization. Preferably, the fan control unit controls the airflow generated by the fans to ensure that the temperatures measured by temperature sensors located in each of the multiple servo drives do not exceed predetermined values. This control prevents excessive temperature rise of the heat-generating elements in any servo drive.

[0020] In one aspect of the cooling device, the heat-generating element is a semiconductor element constituting the inverter circuit. In this case, it is preferable that the specified value for controlling the airflow is determined based on the rated maximum value of the junction temperature of the semiconductor element. By determining the specified value in this way, it is possible to optimize the fan operation within a range where the junction temperature of the semiconductor element does not exceed its rated maximum value.

[0021] Invention Effects

[0022] According to the present invention, a cooling device for a robot controller is available, which is capable of precise control based on the temperature of the heat-generating element contained in the servo drive provided within the robot controller. Attached Figure Description

[0023] Figure 1 This is a block diagram illustrating a robot controller according to an embodiment of the present invention.

[0024] Figure 2 This is a schematic 3D diagram representing a servo driver.

[0025] Figure 3 (a) is a top view of the servo drive. Figure 3 (b) is Figure 3 (a) is a cross-sectional view of the BB line. Figure 3 (c) is Figure 3 Enlarged view of part C in (b).

[0026] Figure 4 This is a general front view showing the configuration of the servo drives and cooling fans in the robot controller.

[0027] Figure 5 This is a block diagram showing the mechanism for controlling the cooling fan.

[0028] Explanation of reference numerals in the attached figures

[0029] 11-18…Servo driver; 21…Host control circuit; 22…Main power supply circuit; 31…Control circuit; 32…Inverter circuit; 41…IPM; 42…Heat sink assembly; 43…Circuit board; 44…Spacer bar; 45-48…Connector; 49…Optocoupler; 51…Circuit component group; 52…Heat conductive sheet; 53…Connecting pin; 54…Screw; 55…Temperature sensor; 71, 72…Fan; 73, 74…Fan control unit; 80…Motor; 81…External power supply. Detailed Implementation

[0030] Next, embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1This is a block diagram illustrating the structure of a robot controller according to an embodiment of the present invention, equipped with a cooling device based on the present invention. The robot controller is capable of controlling an 8-axis manipulator and includes eight servo drives 11-18 corresponding to the eight motors 80 mounted on the manipulator. Furthermore, the robot controller includes a host control circuit 21 that sends commands to the servo drives 11-18, and a main power supply circuit 22 that receives and rectifies AC power from an external power source 81. Each of the servo drives 11-18 includes a control circuit 31 that performs servo control calculations for the motors 80 based on commands from the host control circuit 21, and an inverter circuit 32 that generates AC power for driving the motors 80 based on the calculation results of the control circuit 31. An encoder (not shown) attached to the corresponding motor 80 feeds back a signal indicating the position of the motor 80 to the control circuit 31. DC power is supplied from the main power supply circuit 22 to the inverter circuit 32. As described above, the inverter circuit 32 includes switching elements such as IGBTs to generate three-phase AC power from DC power to supply to the motors 80. In this embodiment, in the inverter circuit 32, an IPM41 (see reference) is used, which houses the switching elements or their gate drive circuits, protection circuits, etc., in a single package. Figure 2 Switching elements generate a considerable amount of heat during their operation, thus they are heat-generating elements.

[0031] Next, servo drives 11 to 18 will be described. Since servo drives 11 to 18 have the same structure, servo drives 11 to 18 will be described here using servo drive 11 as an example. Figure 2 This is a schematic perspective view of the servo driver 11. The IPM41, which forms the inverter circuit 32 as a heat-generating element, is connected to screw 54 (see reference). Figure 3 (c) is mounted on a heat sink component (heat sink) 42 for heat dissipation. Furthermore, the heat sink component 42 is mounted on the circuit board 43 with spacers 44 at predetermined intervals relative to one surface of the circuit board 43. The heat sink component 42 has a plurality of ridge-shaped heat sinks arranged parallel to each other relative to a plate-shaped base plate. In the example shown here, the base plate of the heat sink component 42 is configured parallel to the circuit board 43, and the IPM 41 is mounted on the base plate of the heat sink component 42. As described later, fans 71 and 72 (see reference) Figure 4 An airflow is generated toward the heat sink component 42, thereby cooling the IPM41, which is a heat-generating element. On one surface of the circuit board 43, a connector 45 for supplying AC power to the motor 80, signal connectors 46 and 48, and a connector 47 for receiving DC power from the main power supply circuit 22 are provided. Connector 48 of the signal connectors 46 and 48 is used for both communication with the encoder attached to the motor 80 and communication with the upper control circuit 21.

[0032] Figure 3 (a) is a top view of servo drive 11. Figure 3 (b) is Figure 3 (a) is a cross-sectional view of the BB line. Figure 3 (c) is Figure 3 An enlarged view of section C in (b). In the servo driver 11, the control circuit 31 basically processes logic signals below a few volts, while the inverter circuit 32 processes dangerous voltages specified by safety standards to drive the motor 80. Therefore, for safety and other purposes, such as... Figure 3 As shown in (a), the circuit board 43 is divided into region P and region S. The inverter circuit 32 and its associated circuits are disposed in region P, and the control circuit 31 is disposed in region S. High-power connectors 45 and 47 are disposed in region P, and signal connectors 46 and 48 are disposed in region S. Signal exchange between the control circuit 31 and the inverter circuit 32 is performed via an optocoupler 49 disposed on the circuit board 43 in a manner that spans regions P and S.

[0033] As described above, the heat sink component 42 is mounted on one surface of the circuit board 43 via a spacer bar 44. In this state, the IPM 41 mounted on the heat sink component 42 faces the surface of the circuit board 43. Furthermore, the connection pin 53 of the IPM 41 extends toward and through the circuit board 43, and is soldered to the circuit board 43 at this location. A heat-conducting sheet 52 is disposed in the gap between the IPM 41 and the circuit board 43 to fill the gap. A temperature sensor 55 is provided on one surface of the circuit board 43, sandwiching the heat-conducting sheet 52 and facing the IPM 41. The temperature sensor 55 is covered by the heat-conducting sheet 52. The temperature sensor 55 is located in region P, which is the side handling high power; therefore, it is preferable to use a sensor that outputs a pulse signal based on the measured temperature as the temperature sensor 55. The output of the temperature sensor 55 is transmitted to region S via an optocoupler 49 or the like. A group of circuit elements 51 constituting the control circuit 31 is provided on the other surface of the circuit board 43.

[0034] The heat-conducting sheet 52 is preferably an adhesive insulating sheet. For example, as described in Patent Document 5, the heat-conducting sheet 52 is made of materials with high thermal conductivity, such as acrylic acid, silicone rubber, silicone elastomer, glass fiber, dielectric film, or polyester film. The purpose of the heat-conducting sheet 52 is to more accurately measure the junction temperature in the IPM 41 using the temperature sensor 55. Therefore, the heat-conducting sheet 52 needs to be in contact with the surface of the IPM 41 and one surface of the circuit board 43, preferably in close contact. When one surface of the circuit board 43 is in contact with the heat-conducting sheet 52, the temperature sensor 55 disposed on one surface of the circuit board 43 is essentially embedded in the heat-conducting sheet 52.

[0035] Figure 4 This diagram illustrates the actual configuration of the servo drives 11-18 in the robot controller. The eight servo drives 11-18 are stacked at equal intervals along the thickness direction of the circuit board 43. Cooling fans 71 and 72 are also provided. The fans 71 and 72 are configured such that the airflow generated by them is split according to each servo drive 11-18 and flows along the heat sinks of the heat sink components 42 of each servo drive 11-18. The airflow from the fans 71 and 72 is indicated by arrows in the diagram. In the illustrated example, the four servo drives 11-14 on the upper side of the diagram are cooled by the airflow generated by the fans 71, and the four servo drives 15-18 on the lower side are cooled by the airflow generated by the fans 72. In this robot controller, the rotational speed of the fans 71 and 72, i.e., the airflow generated by the fans 71 and 72, is controlled based on the temperature measured by temperature sensors 55 respectively installed on the servo drives 11-18. To implement such control, fans 71 and 72 are used that can vary the generated airflow by changing their drive voltage or by changing the PWM duty cycle of the control signal supplied to fans 71 and 72. The control of fans 71 and 72 based on the temperature measured by temperature sensor 55 will be described below.

[0036] Figure 5 This diagram illustrates the mechanisms used to control fans 71 and 72. Temperature sensors 55 are installed in servo drives 11-18, and fan control units 73 and 74 are provided. Fan control unit 73 receives signals from the temperature sensors 55 of servo drives 11-14 (top view); fan control unit 74 receives signals from the temperature sensors 55 of servo drives 15-18 (bottom view). Fan control unit 73 controls the airflow generated by fan 71 to ensure that the temperature measured by any temperature sensor 55 in servo drives 11-14 does not exceed a specified value. The specified value is determined based on the rated maximum junction temperature specified in IPM41. Similarly, fan control unit 74 controls the fan motor driving fan 72 to ensure that the temperature measured by any temperature sensor 55 in servo drives 15-18 does not exceed the specified value. Fan control units 73 and 74 are separately installed from servo drives 11-18 in the robot controller. Alternatively, the host control circuit 21 can also have the functions of fan control units 73 and 74. With this configuration, the junction temperature of the heating element in the robot controller can be kept below the rated maximum value, the drive of fans 71 and 72 can be optimized, the lifespan of fans 71 and 72 can be extended, and the power consumption of fans 71 and 72 can be reduced.

[0037] In this embodiment, heat is conducted to the temperature sensor 55 disposed on the surface of the circuit board 43 via a heat-conducting sheet that is in close contact with the IPM41 and the circuit board 43. As a result, the temperature measured by the temperature sensor 55 more accurately represents the junction temperature of the switching elements within the IPM41 than the junction temperature estimated based on the output current of the inverter circuit 32. Therefore, in this embodiment, the drive of the fans 71 and 72 can be controlled more precisely based on the junction temperature of the switching elements, significantly extending the lifespan of the fans 71 and 72 and significantly reducing their power consumption. Especially in the case of industrial robots, the motors 80 of each axis are usually driven only intermittently. As long as the heat generation in the servo drives 11 to 18 is relatively small when averaged over time, the power reduction effect and the effect of extending the lifespan of the fans achieved by applying the control of this embodiment are significant. Furthermore, in the robot controller, the specifications of the motors of each robot connected to it are different, and the heat generation in the servo drives 11 to 18 is different. However, by applying this embodiment, even if the speed of the fans 71 and 72 is not set individually for each connected robot, the fans 71 and 72 can always be driven in a way that achieves the optimal airflow.

[0038] The servo drives 11-18, which include a circuit board 43 and a heat sink component 42 having a base plate arranged parallel to the circuit board 43, generally have a flat shape, with the heat sink component 42 exposed on the flat surface. On the other hand, the cooling fans 71 and 72 are square, frame-like shapes capable of accommodating rotating blades. If a cooling fan is provided for each flat servo drive, the space utilization efficiency in the robot controller decreases; however, in this embodiment, since multiple servo drives are cooled by a single fan, the space utilization efficiency in the robot controller can be improved. In the example above, four servo drives are cooled by one fan, but the number of servo drives cooled by one fan is not limited to four. When the number of servo drives is increased or decreased according to the number of motors installed on the robot, the number of fans can also be increased or decreased accordingly. Furthermore, in Figure 4 In the example shown, servo drivers 11-18 are positioned upstream of fans 71 and 72 to generate airflow drawn in by fans 71 and 72, which flows toward the heat sink component 42. However, the positional relationship between the heat sink component and the fans in this invention is not limited to this. The heat sink component can also be positioned downstream of the fans so that the airflow exhausted from the fans flows directly toward the heat sink component.

Claims

1. A cooling device for a robot controller, comprising a servo driver, the servo driver having a circuit board, a control circuit, and a heat-generating element, wherein the cooling device comprises: A heat sink component, wherein the heat sink component is mounted on the heat-generating element; Temperature sensor; A heat-conducting sheet that transfers heat generated by the heating element to the temperature sensor; A fan that generates airflow toward the heat sink assembly; as well as A fan control unit controls the fan based on the temperature sensor's detection value. The heat-conducting plate is located between the circuit board and the heating element in the servo driver, and is in contact with both the circuit board and the heating element. The temperature sensor is disposed on the first surface of the circuit board and embedded in the thermal conductive sheet. The control circuit is disposed on the second surface of the circuit board opposite to the first surface. When viewed from the thickness direction of the circuit board, the temperature sensor and the control circuit do not overlap.

2. The cooling device for the robot controller according to claim 1, wherein, The fan control unit controls the airflow generated by the fan to ensure that the temperature measured by the temperature sensor does not exceed a specified value.

3. The cooling device for the robot controller according to claim 1, wherein, The robot controller has multiple servo drivers. The airflow generated by one of the fans is split and flows along the heat sink components of each of the plurality of servo drives.

4. The cooling device for the robot controller according to claim 3, wherein, The fan control unit controls the airflow generated by the fan so that the temperature measured by the temperature sensor installed on each of the plurality of servo drives does not exceed a specified value.

5. The cooling device for the robot controller according to claim 2 or 4, wherein, The heating element is a semiconductor element that constitutes the inverter circuit, and the specified value is determined based on the rated maximum value of the junction temperature of the semiconductor element.

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