Technical field of the invention

The present invention relates to actuators for fluid flow controllers, such as damper or HVAC actuators.

Background of the invention

Most actuators for fluid flow controllers, such as damper actuators, comprise an electric motor, a gearing, a motor driver circuit, a microcontroller, a housing, and a mounting system fitted for the shaft of the fluid flow controller. In addition, damper actuators further often comprise various mechanisms e.g., for smart control, mounting, fault protection, and voltage conversion.

The actuator needs to be able to rotate the shaft of the fluid flow controller in both directions. When the fluid flow controller is correctly positioned, the actuator needs to be able to counteract the forces of the fluid pressure acting on the fluid flow controller to avoid that the fluid flow controller’s position displaces. Furthermore, the standby power consumption needs to be minimized. For solutions, which do not require a spring return actuator, the actuator should be able to hold the shaft in a fixed position, even if the power supply is cut off.

To achieve an actuator with a high output torque for acting on the shaft, a high gear ratio is needed between the mounting system fitted for the shaft of the fluid flow controller and the electric motor (providing the input torque). Flowever, when the motor is deactivated, the input torque from the electric motor is quite low, which in turn limits the output torque exerted on the fluid flow controller’s shaft significantly. Despite this fact, this is still the most commonly used method. To provide a more acceptable input torque, a very high gearing ratio is used, which in turn makes the actuator slow at moving from one position to another.

Some damper actuators use an electric motor that in the deactivated state is provided with a current through the motor (i.e., US10112456). However, this solution has the drawback of a very high standby energy consumption, which also requires a housing design to handle the heating of the electric motor. Some customers incorrectly try to limit this standby energy consumption by incorporating a relay to turn off power to the damper actuator when it is finished rotating. However, this solution disables the holding torque, enabling the fluid flow controller to displace as it is pushed by the internal pressure in the system in which it is positioned.

Other actuators have an electric circuit to short circuit the electric motor (e.g., CN207316187) when not in use, effectively turning it into an electric generator. This solution only slightly increases the holding torque and is therefore still unsatisfactory, as this limits the actuator’s applications.

Other actuators use a locking gear (e.g., CN104315783, EP1646817,

GB1 133642, KR101898555, CN207648154, CN109130785, CN208947032,

CN106515380, CN209063851 , CN204354764, US2004129102, US2010025610, US10069448, WO2017204593, KR101595326, KR200463307, and KR20110051673), often referred to as a worm gear, that enable a very high holding torque but often have an energy loss due to friction of more than 50%. This gearing further requires orthogonality between the motor shaft and the fluid flow controller shaft. Further, the forces exerted between the worm and the worm gear result in strong axial forces that require a housing design that clamps them together.

Other actuators use a braking mechanism (e.g., US2008009236), which can be activated and deactivated. These mechanisms are costly to manufacture as they require extra parts as well as extra actuators to engage the brake. Furthermore, the brake increases the standby energy consumption.

Still other actuators use a locking arm mechanism (e.g., WO2015135988,

CN102095018, US7913972, EP3597973, WO2018060221 , and US5986369), which can engage and disengage with a locking cog. The wheels have a limited number of locking holes to engage in, which leads to the damper shaft having to rotate back to the nearest locking hole. The mechanism is expensive to manufacture and requires extra actuators for both engaging and disengaging the locking. In some mounting circumstances the locking arm can get stuck in the locking cog, as the damper blade is tensioned against the damper face given a high input torque of the electric motor and gearing, which is released after the locking arm is engaged, leading to the locking arm becoming stuck due to the high forces and no longer able to disengage with the, often weak, disengaging actuators.

Yet other solutions (WO2013013334) accept an inadequate holding torque and have a set interval to continuously re-activate the electric motor to move the fluid flow controller shaft back to its intended position. However, the standby energy consumption is still significantly high and the wear on the system is much higher, making this solution more expensive. The construction of the housing needs to be such that the generated heat by the abnormally active electric motor is directed away. Some customers incorrectly try to limit this standby energy consumption by incorporating a relay to turn off the power to the damper actuator when it is finished rotating. However, this solution disables the holding torque.

To reduce the standby energy consumption, the above solutions need to be employed at the correct position, often being at the end stop position.

Some actuators (e.g., EP1048905) have a timer that counts for a preset time, after which it is assumed that the actuator has finished rotating and can enter a state of low standby energy consumption, often by turning power off. However, depending on the holding torque enabling mechanism, the damper shaft may rotate back. The electric motor is also running for longer time than necessary, increasing the power consumption. Further, a microcontroller is needed to count the time, and in order to power down the actuator a switching component is required, which both adds to the cost. Again, other solutions use current sensing (e.g., US6495981 B2) to identify the end stop, thus reducing the time that the damper actuator is powered on, improving upon the solution using a timer. However, motor drivers with this feature require a microcontroller to control this mechanism, which adds to the cost. Yet other solutions use an encoder or similar feature (e.g., KR20110051673, US2015261226, US2015261225, US2013049644, CN101506747, JP2018155529, US2020041153, EP3173705, US2016141985, US6097123, US6198243, CN204963092) to know or estimate the position of the fluid flow controller shaft in relation to their end stop positions However, this requires a microcontroller, which adds to the cost.

Description of the invention

It is an object of the present invention to overcome the above-mentioned problems. The present invention provides an actuator with reduced power consumption obtained by deactivating the actuator’s motor unit, without the use of a microcontroller, when further rotation of the shaft of a fluid flow controller is no longer possible, and at the same time maintaining an adequate holding torque. The advantages of not using a microcontroller are many. The microcontroller adds to the volume size of an actuator (e.g., a larger Printed Circuit Board (PCB) is needed), thereby obstructing the fluid flow, in which it is often installed. Hence, removing that component allows for a better flow or for installing a larger heat exchanger, thereby allowing the entire system to function more efficiently. Furthermore, preparing a microcontroller with the program code adds to the production time, and thus to the costs of the actuator. Additionally, a lower electromagnetic interference (EMI) is obtained.

One aspect relates to an actuator comprising:

- a mounting system fitted for the rotatable shaft of a fluid flow controller;

- an electric motor unit adapted to transfer a torque to said mounting system via a worm drive; and

- a motor driver; wherein said motor driver comprises current sensing and current regulation mechanism comprising a mechanism configured for deactivating the motor unit when further rotation of said shaft of said fluid flow controller is no longer possible.

In one or more embodiments, the actuator further comprises a housing or mounting plate adapted for supporting the mounting system.

It is contemplated that the mounting system may be used to drive the rotatable shaft of any suitable fluid flow controller, including but not limited to water valves within hydronic heating and/or cooling systems, other fluid or gas valves, and/or any other actuatable valve as desired. The term “fluid flow controller” may encompass any actuatable valve, such as air dampers, water valves, gas valves, ventilation flaps, louvers, and/or other actuatable valves that help regulate or control the flow of fluid in e.g., an HVAC system.

The mounting system may comprise a ring- or tube-shaped drive shaft rotatably mounted in/on a housing or mounting plate. Preferably, the drive shaft comprises a toothed outer face adapted for engaging with a worm gear of the worm drive or a spur gear of a torque increasing gearing operably connected to the worm gear of the worm drive. The drive shaft may comprise a channel adapted for receiving a rotatable shaft of a fluid flow controller.

Although the worm drive does result in an energy loss due to frictional forces, it is chosen by the inventors of the present invention to provide a holding torque (a self-locking gearing) resisting displacement of the fluid flow controller’s position when the motor unit is deactivated. This in order to obtain a low energy consumption at standby.

In one or more embodiments, the actuator further comprises a first torque increasing gearing, such as a micro drive, operably connected to said worm drive and said electric motor unit.

In one or more embodiments, the actuator further comprises a second torque increasing gearing operably connected to said mounting system and said worm drive. Preferably, the second torque increasing gearing and the worm gear of said worm drive are sandwiched such that two spur gears are positioned on each side of said worm gear. The worm gear must be in the middle to reduce the risk that axial forces pushe the worm gear and worm apart. The sandwich gear enables a high output torque in the thinnest possible form. The ring- or tube shaped drive shaft may preferably be embodied as two toothed rings delimiting a guide track adapted for receiving the worm gear.

In one or more embodiments, the mounting system, preferably the drive shaft, comprises a guide recess with a stop, and wherein the housing or mounting plate of the actuator comprises a guide pin adapted for moving within said guide recess and to engage with said stop, thereby allowing the drive shaft of the mounting system to rotate a predefined number of degrees around its axis of rotation. This configuration allows the user or manufacturer to define the allowable degrees of rotation that the mounting system can move the rotatable shaft of the fluid flow controller.

In one or more embodiments, the current sensing and current regulation mechanism is performed without the use of a microcontroller.

In one or more embodiments, the actuator further comprises a first power and signal line connected to a direction input of said motor driver, and a second power and signal line connected to a supply or direction input of said motor driver; and wherein a diode is configured for conducting a current from said first power and signal line to said second power and signal line. With this circuit, the actuator can be operated without using a microcontroller to convert the power and signal input lines to a control output.

In one or more embodiments, the actuator further comprises:

- a first power and signal line connected to a supply or direction input of said motor driver,

- a second power and signal line connected to a supply or direction input of said motor driver; and - a diode configured for conducting a current from said first power and signal line to said second power and signal line. With this circuit, the actuator can be operated without using a microcontroller to convert the power and signal input lines to a control output. Actuators may be controlled by different ways, such as two-wire control and three-wire control as exemplified in Figure 6. The use of the diode allows the actuator to function with both types of control. Hence, the diode either allows a current to pass or not to pass, as shown in Figure 3.

In one or more embodiments, the current sensing and current regulation mechanism comprises performing current chopping on the current supplying the unit. The current chopping may preferably be performed by using cycle-by-cycle current regulation mode but could also be performed by using off-time current regulation mode. Many actuators use off-time current regulation mode without a holding torque (a self-locking gearing), which result in the fluid flow controller being slowly reopened by the pressure within the fluid channel. Therefore, the actuator needs to be reactivated at predefined time periods, which increases the energy consumption and results in a faster wear and tear of the actuator. Such actuators cannot operate in a cycle-by-cycle current regulation mode as it will result in too much leakage of the fluid flow controller.

Other actuators are provided with a locking gearing, but without current control. Such actuators are active even after the fluid flow controller is closed, which results in unwanted power consumption, motor heating, and wear and tear of the system. These actuators require a microcontroller to power off the motor at a predetermined time.

CN208587507 discloses an actuator using a hall-effect sensor for analogue reading of the power consumption as a function of the electrical field. From this reading, a microcontroller performs current regulation.

It should be noted that embodiments and features described in the context of one of the aspects of the present invention also apply to the other aspects of the invention.

Brief description of the figures

Figure 1 shows a mounting system and gearing in accordance with various embodiments of the invention.

Figure 2 shows a first side view of the actuator in accordance with various embodiments of the invention mounted on a rotatable shaft of a fluid flow controller.

Figure 3 shows a part of an electrical circuit diagram in accordance with various embodiments of the invention and working without a microcontroller.

Figure 4 shows an example of off-time current regulation.

Figure 5 shows an example of cycle-by-cycle current regulation.

Detailed description of the invention

The following description is to be a non-limiting example of an actuator according to various embodiments of the present invention.

Most actuators for fluid flow controllers, such as damper actuators, comprise an electric motor, a gearing, a motor driver circuit, a microcontroller, a housing, and a mounting system fitted for the shaft of the fluid flow controller.

Figure 1 shows a mounting system 200, an electric motor unit 300, and a gearing 400, 800, 900 in accordance with various embodiments of the invention. The mounting system 200 is fitted for the rotatable shaft 10 of a fluid flow controller. The mounting system 200 comprises a guide recess 210 with a stop 220. The housing or mounting plate 700 (see Figure 2) comprises a guide pin 710 adapted for moving within said guide recess 210 and to engage with said stop 220. This embodiment allows the drive shaft of the mounting system 200 only to rotate a by the guide recess 210 defined number of degrees around its axis of rotation.

The gearing as exemplified in Figure 1 comprises a first torque increasing gearing 800 operably connected to a worm drive 500 and the electric motor unit 400. A second torque increasing gearing 900 is operably connected to the mounting system 200 and the worm drive 500. The second torque increasing gearing 900 and the worm gear 420 of said worm drive 400 are sandwiched such that two spur gears 910, 920 are positioned on each side of said worm gear 420. The mounting system 200 is here embodied with a tube-shaped drive shaft comprising two toothed rings 230 delimiting a guide track 240 adapted for receiving the worm gear 420.

The actuator’s motor driver 500 comprises a current sensing and current regulation mechanism comprising a mechanism configured for deactivating the motor unit 300 when further rotation of said shaft 10 of said fluid flow controller is no longer possible. In this example, this situation occurs when the guide pin 710 engages with one of the end stops 220 of the guide recess 210.

The current sensing and current regulation mechanism may have any suitable embodiment. An exemplary embodiment may be an H-Bridge motor driver with integrated current Sense and regulation, such as one from the DRV88xx or DRV87xx family by Texas Instruments. The DRV88xx family of devices are flexible motor drivers for a wide variety of applications. The devices integrate an N-channel H-bridge, charge pump regulator, current sensing and regulation, current proportional output, and protection circuitry. The charge pump improves efficiency by allowing for both high-side and low-side N-channels MOSFETs and 100% duty cycle support. The integrated current sensing allows for the driver to regulate the motor current during start up and high load events. A current limit can be set with an adjustable external voltage reference or a resistor that works like a voltage divider. Additionally, the devices provide an output current proportional to the motor load current. This can be used to detect motor stall or change in load conditions. The integrated current sensing uses an internal current mirror architecture, removing the need for a large power shunt resistor, saving board area and reducing system cost. Other examples of suitable motor drivers with integrated current sense and regulation are STSPIN250 from STMicroelectronics, and TMC7300 and TMC2100 from TRINAMIC Motion Control.

Figure 3 shows a part of an electrical circuit diagram in accordance with various embodiments of the invention and working without a microcontroller. The actuator 100 may comprise a first power and signal line 610 connected to a supply or direction input 510 of said motor driver 500, and a second power and signal line 620 connected to a second 520 supply or direction input of said motor driver 500. A diode 630, such as any suitable power diode, is configured for conducting a current from said first power and signal line 610 to said second power and signal line 620. The actuator comprises two power and signal lines 610, 620 and a ground/neutral line 640. If 610 is low and 620 is high, then the motor of the motor unit 300 rotates the first direction and the diode 630 blocks current from 620 from entering the first supply or direction input 510. If 610 is high and 620 is low, then the then the motor of the motor unit 300 rotates in the second direction and the diode 630 enables current to run into the second supply or direction input 520, thereby powering the H-bridge. If both 610 and 620 are high, then the motor of the motor unit 300 rotates in the second direction, and no current runs through the diode 630, as the voltage level on both sides of the diode 630 are nearly the same. With this circuit, the actuator can be run without using a microcontroller to convert the power and signal lines to a control output to the H-bridge.

The H-bridge uses current sensing to stop the motor of the motor unit 300 from running against any one end stops 220, where further rotation is no longer possible, thus reducing the power consumption of the circuit. However, this also reduces the holding torque of the motor significantly. However, when used together with a worm gear as described above, the worm gear is self-locking, removing the need for the motor to provide this holding torque. If the H-bridge uses current chopping using cycle-by-cycle current regulation mode (see Figure 5), the H-bridge will run the motor while the control input is high (Vout is high), and when the current drawn by the motor lout is not higher than the set maximum et. Vout is reenabled at the next control input. This mode does not reapply force, and the actuator will therefore wait for a new control signal from a control unit to change position of the fluid flow controller onto which it is mounted.

When the H-bridge uses current chopping using off-time current regulation mode (see Figure 4), the H-bridge will run the motor while the control input is high (Vout is high), and when the current drawn by the motor lout is not higher than the set maximum et. When the current drawn by the motor lout exceeds the set maximum, et, then Vout is off for a set amount of time after which Vout goes back on. However, this mode consumes more power than the cycle-by-cycle current regulation mode.

References

10 Rotatable shaft

100 Actuator

200 Mounting system 210 Guide recess

220 Stop

230 Ring

240 Guide track

300 Motor unit 400 Worm drive

410 Worm

420 Worm gear

500 Motor driver

510 Supply or direction input 520 Supply or direction input

610 First power and signal line

620 Second power and signal line

630 Diode

700 Housing 710 Guide pin

800 First torque increasing gearing

900 Second torque increasing gearing

910 Spur gear

920 Spur gear