Robot controller cooling system

Abstract

To enable a cooling system for a robot controller to perform detailed control based on a temperature of heating elements in a servo driver.SOLUTION: A cooling system consists of a fin member 42 to which a heating element (IPM 41) is attached, a temperature sensor 55, a heat-conductive sheet 52 that transfers heat generated by the heating element to the temperature sensor 55, fans 71,72 that generate an airflow toward the fin member 52, and the fan control unit 73,74 controlling the fans 71,72 on the basis of the detected values of the temperature sensors 55. The heat-conductive sheet 52 is between a circuit board 43 and the heat-generating element in a servo driver 11 and contacts both the circuit board 43 and the heating element. The temperature sensor 55 is provided on the circuit board 43 so that the temperature sensor is covered with the heat-conductive sheet 52.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a cooling device for a robot controller.

Background Art

[0002] In industrial robots, a motor for driving each axis is provided for each axis in a manipulator (robot body). A robot controller that uses the control of the manipulator includes a servo driver that drives and controls the motor corresponding to each axis. If the manipulator has 8 axes, the robot controller also includes 8 servo drivers. Since the motor provided in the manipulator is, for example, a three-phase motor, the servo driver includes an inverter circuit that generates three-phase AC power to be supplied to the corresponding motor, for example, by PWM (pulse width modulation). The inverter circuit includes, for each phase of the motor, a series connection of two switching elements called a high-side switch and a low-side switch. As the switching element, for example, semiconductor elements such as a power MOSFET (metal oxide semiconductor field effect transistor) and an IGBT (insulated gate bipolar transistor) are used. In recent years, an IPM (intelligent power module) that houses a plurality of switching elements constituting the inverter circuit, a gate drive circuit for driving the gates of the switching elements, a protection circuit, etc. in one package has been widely used.

[0003] When an inverter circuit generates AC power to drive a motor, the switching elements within the inverter circuit generate heat. Since switching elements are semiconductor devices, it is necessary to ensure that their junction temperature does not exceed a predetermined rated maximum. Therefore, a heat-dissipating fin component, also called a heat sink, is attached to the switching element, and a cooling fan is used to direct airflow along the fin component to cool the switching element. Similar cooling methods are used when using IPMs. The cooling fan is driven by a motor called a fan motor. Previously, the fan was operated at maximum airflow continuously, but this is disadvantageous from the standpoint of power consumption and fan motor lifespan. Therefore, it has been proposed to operate the fan at the required airflow only when needed. For example, Patent Document 1 discloses controlling the fan's rotation on / off and fan speed by determining the amount of heat generated by a command to the servo driver when cooling an inverter circuit used in a servo driver. Patent Document 2 discloses calculating the power consumed as heat in the switching element from the output current of a power conversion circuit such as an inverter circuit to estimate the temperature, and controlling the cooling fan based on the estimated temperature. Patent Document 3 discloses a method for estimating the junction temperature of a switching element based on the output current from an inverter circuit, the airflow rate in a fin member, and the ambient temperature of the switching element, and controlling a cooling fan based on the estimated junction temperature.

[0004] Electrolytic capacitors are often used for smoothing in power supply circuits and the like, but they have the property that their lifespan is shortened when the ambient temperature is high. Patent document 4 discloses a method for controlling the amount of air blown by a cooling fan used to cool semiconductor elements when the fan also cools electrolytic capacitors, based on the relationship between the amount of air blown by the fan, the lifespan of the fan, and the lifespan of the electrolytic capacitor. Patent document 5 also discloses a temperature sensor that can accurately measure the temperature of electronic components such as semiconductor elements, which consists of a thermal conductive sheet that is in close contact with the electronic component and the substrate on which the electronic component is mounted, or a heat sink attached to the electronic component, with a thermal sensing element installed on the thermal conductive sheet. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 6-117393 [Patent Document 2] Patent No. 4796841 [Patent Document 3] Patent No. 5486434 [Patent Document 4] Patent No. 6498371 [Patent Document 5] Japanese Patent Publication No. 2011-33479 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] When using the techniques described in Patent Documents 1-4 to remove heat generated by a servo driver in a robot controller using a cooling fan, there is a problem in that it only estimates the junction temperature of the switching element, which is the heat-generating element, and it is difficult to finely control the cooling fan based on the actual temperature of the heat-generating element.

[0007] The object of the present invention is to provide a cooling device for a robot controller that can perform fine-grained control based on the temperature of a heat-generating element included in a servo driver provided within the robot controller. [Means for solving the problem]

[0008] A cooling device according to one aspect of the present invention is a cooling device for a robot controller having a servo driver comprising a circuit board and a heating element, comprising: a fin member attached to the heating element; a temperature sensor; a heat conductive sheet that transfers heat generated by the heating element to the temperature sensor; a fan that generates airflow toward the fin member; and a fan control unit that controls the fan based on the value detected by the temperature sensor. The fin member comprises a bottom plate arranged parallel to the circuit board at a predetermined distance, and a plurality of mutually parallel fins formed on one surface of the bottom plate. The heating element is attached to the other surface of the bottom plate, and the connection pins of the heating element are soldered to the circuit board.The thermal conductive sheet is located between the circuit board and the heating element in the servo driver, making contact with both the circuit board and the heating element, and the temperature sensor is provided on the circuit board in the area covered by the thermal conductive sheet.

[0009] In one embodiment of the cooling device, heat is transferred to a temperature sensor provided on the circuit board via a thermal conductive sheet, 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, thereby reducing power consumption and extending the fan's lifespan.

[0010] In a cooling system, it is preferable that the fan control unit controls the airflow generated by the fan so that the temperature measured by the temperature sensor does not exceed a specified value. By performing such control, it is possible to prevent the temperature of the heat-generating element from rising excessively.

[0011] In a cooling system, if the robot controller has multiple servo drivers, the airflow generated by one fan can be divided and flow along the fin members of each of the multiple servo drivers. This configuration reduces the number of fans and allows for efficient use of space within the robot controller, thereby achieving miniaturization of the robot controller. In this case, it is preferable for the fan control unit to control the airflow generated by the fan so that the temperature measured by the temperature sensors provided on each of the multiple servo drivers does not exceed a specified value. By performing such control, it is possible to prevent the temperature of the heat-generating elements of any of the servo drivers from rising excessively.

[0012] In one embodiment of a cooling device, the heat-generating element is a semiconductor element constituting an inverter circuit, and in this case, the specified value used for controlling the airflow is preferably a value determined based on the rated maximum value for the junction temperature of the semiconductor element. By setting the specified value in this way, it becomes possible to perform control that optimizes the operation of the fan within a range in which the junction temperature of the semiconductor element does not exceed the rated maximum value. [Effects of the Invention]

[0013] According to the present invention, a cooling device for a robot controller is obtained that can perform fine-grained control based on the temperature of a heating element included in a servo driver provided within the robot controller. [Brief explanation of the drawing]

[0014] [Figure 1] A block diagram showing a robot controller as one embodiment of the present invention. [Figure 2] This is a schematic perspective view showing a servo driver. [Figure 3] (a) is a plan view of the servo driver, (b) is a cross-sectional view of the BB line in Figure 3(a), and (c) is an enlarged view of section C in Figure 3(b). [Figure 4] This is a schematic front view showing the arrangement of servo drivers and cooling fans in a robot controller. [Figure 5] This is a block diagram showing the control mechanism for a cooling fan. [Modes for carrying out the invention]

[0015] Next, embodiments of the present invention will be described with reference to the drawings. Figure 1 is a block diagram showing the configuration of a robot controller in one embodiment of the present invention, which incorporates a cooling device based on the present invention. This robot controller is capable of controlling an 8-axis manipulator and is equipped with 8 servo drivers 11 to 18 corresponding to 8 motors 80 provided on the manipulator. Furthermore, the robot controller includes a higher-level control circuit 21 that sends commands to the servo drivers 11 to 18, and a main power supply circuit 22 that receives AC power from an external power supply 81 and rectifies it. Each of the servo drivers 11 to 18 is equipped with a control circuit 31 that performs calculations for servo control of the motor 80 based on commands from the higher-level control circuit 21, and an inverter circuit 32 that generates AC power to drive the motor 80 based on the calculation results of the control circuit 31. The control circuit 31 receives a signal indicating the position of the motor 80 from an encoder (not shown) attached to the corresponding motor 80 as feedback. The inverter circuit 32 is supplied with DC power from the main power supply circuit 22. As mentioned above, the inverter circuit 32 is equipped with switching elements such as IGBTs to generate three-phase AC power supplied to the motor 80 from DC power. In this embodiment, the inverter circuit 32 uses an IPM41 (see Figure 2) which houses the switching elements, their gate drive circuit, and protection circuit in a single package. Switching elements are heat-generating elements because they generate a considerable amount of heat during their operation.

[0016] Next, the servo drivers 11 to 18 will be described. Since the servo drivers 11 to 18 have the same configuration, the servo drivers 11 to 18 will be described here by the servo driver 11. FIG. 2 is a schematic perspective view of the servo driver 11. The IPM 41 that constitutes the inverter circuit 32, which is a heating element, is attached to the heat radiating fin member (heat sink) 42 by a screw 54 (see FIG. 3(c)). Further, the fin member 42 is attached to the circuit board 43 via a spacer 44 so as to be disposed at a predetermined interval with respect to one surface of the circuit board 43. The fin member 42 has a shape in which a plurality of ridge (ridge) - shaped fins are provided parallel to each other with respect to a plate - shaped bottom plate. In the example shown here, the bottom plate of the fin member 42 is arranged to be parallel to the circuit board 43, and the IPM 41 is attached to the bottom plate of the fin member 42. As will be described later, airflows toward the fin member 42 are generated by the fans 71, 72 (see FIG. 4), and thereby the IPM 41, which is a heating element, is cooled. On one surface of the circuit board 43, a connector 45 for supplying AC power to the motor 80, signal connectors 46, 48, and a connector 47 for receiving DC power from the main power supply circuit 22 are provided. Among the signal connectors 46, 48, the connector 48 is used for both communication with the encoder attached to the motor 80 and communication with the upper - level control circuit 21.

[0017] Fig. 3(a) is a plan view of the servo driver 11, Fig. 3(b) is a sectional view taken along the line B - B of Fig. 3(a), and Fig. 3(c) is an enlarged view of part C in Fig. 3(b). In the servo driver 11, basically, the control circuit 31 processes logic signals of several volts or less, and the inverter circuit 32 processes dangerous voltages defined by safety standards for driving the motor 80. Therefore, for purposes such as ensuring safety, as shown in Fig. 3(a), the circuit board 43 is divided into a region P and a region S. The inverter circuit 32 and related circuits are arranged in the region P, and the control circuit 31 is arranged in the region S. The connectors 45 and 47 that handle high power are arranged in the region P, and the signal connectors 46 and 48 are arranged in the region S. The signal exchange between the control circuit 31 and the inverter circuit 32 is performed via a photocoupler 49 provided on the circuit board 43 so as to straddle the region P and the region S.

[0018] As described above, the fin member 42 is attached to one surface of the circuit board 43 via the spacer 44. In this state, the IPM 41 attached to the fin member 42 faces the side of one surface of the circuit board 43. The connection pins 53 of the IPM 41 extend toward the circuit board 43 and penetrate the circuit board 43, and are soldered to the circuit board 43 at that position. A heat conduction sheet 52 is arranged in the gap between the IPM 41 and the circuit board 43 so as to fill this gap. A temperature sensor 55 is provided on one surface of the circuit board 43 so as to face the IPM 41 with the heat conduction sheet 52 interposed therebetween. The temperature sensor 55 is covered by the heat conduction sheet 52. Since the position where the temperature sensor 55 is provided is in the region P on the side that handles high power, it is preferable to use a temperature sensor that outputs a pulse signal based on the measured temperature as the temperature sensor 55, and the output result of the temperature sensor 55 is transmitted to the side of the region S via the photocoupler 49 or the like. Circuit element groups 51 that constitute the control circuit 31 are provided on the other surface of the circuit board 43.

[0019] The thermal conductive sheet 52 is preferably an adhesive insulating sheet. As an example, the thermal conductive sheet 52 is a sheet made of a material with relatively high thermal conductivity, such as acrylic, silicone rubber, elastomer-based silicone, glass fiber, dielectric film, or polyester film, as described in Patent Document 5. The thermal conductive sheet 52 is intended to measure the junction temperature in the IPM 41 more accurately using the temperature sensor 55. Therefore, the thermal conductive sheet 52 needs to be in contact with both the surface of the IPM 41 and one surface of the circuit board 43, and it is preferable that they are in close contact. When the thermal conductive sheet 52 is in contact with one surface of the circuit board 43, the temperature sensor 55, which is placed on one surface of the circuit board 43, is substantially embedded in the thermal conductive sheet 52.

[0020] Figure 4 shows how the servo drivers 11-18 are actually arranged in the robot controller. The eight servo drivers 11-18 are arranged to be stacked at equal intervals in the thickness direction of the circuit board 43. Cooling fans 71 and 72 are provided. The fans 71 and 72 are positioned so that the airflow generated by the fans 71 and 72 is divided among the servo drivers 11-18 and flows along the fins of the fin members 42 of each servo driver 11-18. The airflow from the fans 71 and 72 is indicated by arrows in the figure. In the illustrated example, the four upper servo drivers 11-14 are cooled by the airflow generated by fan 71, and the four lower servo drivers 15-18 are cooled by the airflow generated by fan 72. In this robot controller, the rotation amount of fans 71 and 72, i.e., the airflow generated by fans 71 and 72, is controlled based on the temperature measured by temperature sensors 55 provided on each of the servo drivers 11-18. To implement this type of control, fans 71 and 72 are used that can change the amount of air they generate by changing their drive voltage or by changing the PWM duty cycle of the control signals supplied to fans 71 and 72. The control of fans 71 and 72 based on the temperature measured by the temperature sensor 55 will be described below.

[0021] Figure 5 shows the mechanism for controlling fans 71 and 72. Each of the servo drivers 11 to 18 is equipped with a temperature sensor 55. There is a fan control unit 73 that receives signals from the temperature sensors 55 of the upper servo drivers 11 to 14, and a fan control unit 74 that receives signals from the temperature sensors 55 of the lower servo drivers 15 to 18. The fan control unit 73 controls the airflow generated by the fan 71 so that the temperature measured by any of the temperature sensors 55 of the servo drivers 11 to 14 does not exceed a specified value. The specified value is determined based on the rated maximum value of the junction temperature specified in the IPM 41. Similarly, the fan control unit 74 controls the fan motor that drives the fan 72 so that the temperature measured by any of the temperature sensors 55 of the servo drivers 15 to 18 does not exceed a specified value. The fan control units 73 and 74 are provided separately from the servo drivers 11 to 18 in the robot controller. The functions of the fan control units 73 and 74 may also be provided in the higher-level control circuit 21. By configuring it in this way, the robot controller can optimize the operation of fans 71 and 72 while ensuring that the junction temperature of the heat-generating element does not exceed the rated maximum value. This extends the lifespan of fans 71 and 72 and reduces the power consumption of fans 71 and 72.

[0022] In this embodiment, heat is conducted to the temperature sensor 55 provided on the surface of the circuit board 43 by a thermal conductive sheet that is in close contact with the IPM 41 and the circuit board 43. As a result, the temperature measured by the temperature sensor 55 is considered to more accurately represent the junction temperature of the switching elements in the IPM 41 than the junction temperature estimated from 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, the lifespan of the fans 71 and 72 can be greatly extended, and the power consumption of the fans 71 and 72 can be greatly reduced. In particular, in the case of industrial robots, the motors 80 of each axis are usually driven only intermittently, and the heat generated in the servo drivers 11 to 18 is small on average over time, so the effect of reducing power consumption and extending the lifespan of the fans by applying the control of this embodiment is remarkable. Furthermore, in a robot controller, the motor specifications may differ for each robot connected to it, which can result in different heat generation in the servo drivers 11-18. However, by applying this embodiment, the fans 71 and 72 can always be driven to provide the optimal airflow without having to individually set the speed of the fans 71 and 72 for each connected robot.

[0023] The servo drivers 11-18, each comprising a circuit board 43 and a fin member 42 having a bottom plate arranged parallel to the circuit board 43, have an overall flat shape, with the fin member 42 exposed on the flat surface. On the other hand, the cooling fans 71 and 72 have a square frame shape that can accommodate the rotating blades. If a cooling fan were provided for each flat servo driver, the space utilization efficiency in the robot controller would decrease. However, in this embodiment, multiple servo drivers can be cooled by a single fan, thus improving the space utilization efficiency in the robot controller. In the example described above, four servo drivers are cooled by one fan, but the number of servo drivers cooled by one fan is not limited to four. When the number of servo drivers increases or decreases according to the number of motors provided in the robot, the number of fans should also be increased or decreased accordingly. In the example shown in Figure 4, the servo drivers 11-18 are positioned upstream of the fans 71 and 72 to generate an airflow that is drawn in by the fans 71 and 72, and this airflow is directed towards the fin member 42. However, the positional relationship between the fin member and the fan in this invention is not limited to this, and the fin member may be positioned downstream of the fan so that the airflow discharged from the fan goes directly towards the fin member. [Explanation of symbols]

[0024] 11-18...Servo driver; 21...Higher-level control circuit; 22...Main power supply circuit; 31...Control circuit; 32...Inverter circuit; 41...IPM; 42...Fin component; 43...Circuit board; 44...Spacer; 45-48...Connector; 49...Photocoupler; 51...Circuit element group; 52...Thermal conductive sheet; 53...Connecting pin; 54...Screw; 55...Temperature sensor; 71,72...Fan; 73,74...Fan control unit; 80...Motor; 81...External power supply.

Claims

1. A cooling device for a robot controller having a servo driver comprising a circuit board and a heating element, A fin member attached to the aforementioned heating element, A temperature sensor and A heat conductive sheet that transfers the heat generated by the heating element to the temperature sensor, A fan that generates airflow toward the fin member, A fan control unit that controls the fan based on the value detected by the temperature sensor, Equipped with, The fin member comprises a bottom plate arranged parallel to the circuit board at a predetermined distance, and a plurality of mutually parallel fins formed on one surface of the bottom plate. The heating element is attached to the other side of the bottom plate, and the connection pins of the heating element are soldered to the circuit board. The thermal conductive sheet 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 provided on the circuit board and covered by the heat conductive sheet in the cooling device.

2. The cooling device according to claim 1, wherein the fan control unit controls the amount of air generated by the fan so that the temperature measured by the temperature sensor does not exceed a specified value.

3. The robot controller comprises a plurality of servo drivers, The cooling device according to claim 1, wherein the airflow generated by one of the fans is divided and flows along the fin members of each of the plurality of servo drivers.

4. The cooling device according to claim 3, wherein the fan control unit controls the airflow generated by the fan so that the temperatures measured by the temperature sensors provided in each of the plurality of servo drivers do not exceed a specified value.

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

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