JP7611528B2 - Non-contact power transmission device - Google Patents

Description

The present invention relates to a non-contact power transmission device that transmits power in multiple stages by non-contact power transmission.

In recent years, non-contact power transmission, which does not use wires for power transmission, has come to be widely used. One of the most difficult aspects of designing such non-contact power transmission is output control. Many output control techniques use a method of feeding back information from the output side to the power transmission side via wireless communication, but problems such as delays and uncertainties in wireless communication make it difficult to build a control system. Against this background, there is a "load-independent technology" that attempts to keep the output (e.g., voltage and current) constant in the face of load fluctuations without a control mechanism.

One of the load-independent technologies is called the "load-independent inverter" (see, for example, Non-Patent Document 1). This is a circuit that configures multiple resonant circuits within the inverter, so that the output current or output voltage remains constant even when load fluctuations occur. Furthermore, this circuit always achieves soft switching in response to load fluctuations.

Wireless power supply systems using this load-independent inverter have also been proposed. For example, in the following non-patent document 2, a wireless power supply system has been developed in which a coupling section and an output circuit are connected to a load-independent inverter, thereby making the output current constant.

R. E. Zulinski, K. J. Grady, "Load-independent class E power inverters: part I. theoretical development," IEEE Trans. Circ. Syst. -I, vol. 37, no. 8, pp. 1010-1018, August 1990 S. Aldhaher, D. C. Yates, P. D. Mitcheson, "Load-independent class E/EF inverters and rectifiers for MHz-switching applications," IEEE Trans. Power Electron., vol.33, no.10, pp. 8270-8287, October 2018

In the wireless power supply system using the load-independent inverter described in Non-Patent Document 2, contactless power transmission is performed at only one location. On the other hand, for example, when contactless power transmission is performed at the joint of a robot arm, power is transmitted in multiple stages by contactless power transmission. For this reason, there is a demand for load independence even in multi-stage contactless power transmission.

The present invention has been made in response to the above situation, and aims to provide a non-contact power transmission device that can achieve load independence when transmitting power in multiple stages by non-contact power transmission.

In order to achieve the above object, a non-contact power transmission device according to one aspect of the present invention is a non-contact power transmission device that transmits power in multiple stages by non-contact power transmission, and includes a first stage unit having a load-independent inverter and a power transmission unit that transmits power converted to AC by the inverter in a non-contact manner, second stage to N-1th stage units having a power receiving unit that receives power in a non-contact manner from the previous stage unit and a power transmission unit that transmits power in a non-contact manner to the subsequent stage unit, and an Nth stage unit having a power receiving unit that receives power in a non-contact manner from the N-1th stage unit, where N is an integer of 3 or more, and one or more of the second stage to Nth stage units have a rectifier that rectifies the AC power transmitted in a non-contact manner and outputs a constant voltage or current, and the power transmission unit and the power receiving unit perform non-contact power transmission by series resonance or parallel resonance according to the voltage or current that is constant at the output of the rectifier.

This configuration makes it possible to achieve load independence when transmitting power in multiple stages through non-contact power transmission. In addition, by appropriately selecting the resonance form of the power transmitting unit and the power receiving unit, the output of each rectifier can be made to have a constant voltage or a constant current. Therefore, for example, it is possible to make the output of all rectifiers a constant voltage, or to make multiple rectifiers alternately have a constant voltage and a constant current.

In addition, in a contactless power transmission device according to one aspect of the present invention, the rectifiers all output a constant voltage or all output a constant current, and contactless power transmission between the two units may be performed by a combination of series resonance and parallel resonance using the power transmitting unit and the power receiving unit, respectively.

This configuration allows the outputs of all rectifiers to be consistent at a constant voltage or current, independent of the load. The constant voltage or current value may be the same for each unit, or may be different. In the latter case, for example, the output voltage of one unit may be constant at 5 (V), and the output voltage of another unit may be constant at 10 (V).

In addition, in a non-contact power transmission device according to one aspect of the present invention, two or more of the units in the second stage to the Nth stage may have a rectifier.

With this configuration, in two or more units with rectifiers, the rectifier output can be made constant voltage and current, independent of the load.

In addition, in a non-contact power transmission device according to one aspect of the present invention, the units are links, and the units in the first to Nth stages are connected by joints to form a link mechanism, and non-contact power transmission may be performed at the connection points.

With this configuration, in a link mechanism having multiple links connected by joints, the output of the rectifiers in the second and subsequent links can be made to have a constant voltage and current, independent of the load.

According to one aspect of the present invention, a contactless power transmission device can achieve a constant voltage or current regardless of the load when transmitting power in multiple stages by contactless power transmission.

FIG. 1 is a functional block diagram showing a configuration of a non-contact power transmission device according to an embodiment of the present invention. FIG. 2 is a circuit diagram showing a configuration of a non-contact power transmission device according to the embodiment. FIG. 4 is a schematic diagram showing a link mechanism for performing non-contact power transmission by the non-contact power transmission device according to the embodiment. 1 is a table showing a list of combinations of power transmission modes, power receiving modes, and resonance forms in non-contact power transmission according to the embodiment. FIG. 11 is a circuit diagram showing another example of the configuration of the non-contact power transmission device according to the embodiment.

The contactless power transmission device according to the present invention will be described below using an embodiment. Note that in the following embodiment, components with the same reference numerals are the same or equivalent, and repeated description may be omitted. The contactless power transmission device according to this embodiment realizes load independence when transmitting power in multiple stages by contactless power transmission, and by appropriately selecting the resonance form in contactless power transmission, the output of each rectifier can be made to be a constant voltage or current. Note that multistage transmission means performing contactless power transmission at two or more points.

Figure 1 is a functional block diagram showing the configuration of a non-contact power transmission device 1 according to this embodiment, Figure 2 is a circuit diagram showing the configuration of the non-contact power transmission device 1, and Figure 3 is a schematic diagram showing a link mechanism that performs non-contact power transmission using the non-contact power transmission device 1.

The contactless power transmission device 1 according to this embodiment transmits power in multiple stages by contactless power transmission, and includes a first stage unit 10, a second stage unit 20, and a third stage unit 30. Note that the contactless power transmission according to this embodiment may be performed, for example, by a magnetic resonance method. As the form of resonance (resonance), an appropriate combination of series resonance and parallel resonance is used, as described later. In addition, in this embodiment, a case where the contactless power transmission device 1 has three units, i.e., the first to third stage units 10 to 30, is described, but the contactless power transmission device 1 may also have N units, i.e., the first to Nth stage units, as described later. Here, N is an integer equal to or greater than 3.

In this embodiment, the first to third stage units 10 to 30 are each links, and a link mechanism is formed by connecting them via joints. In this case, non-contact power transmission between the units is performed at the connection points, i.e., at the joint positions.

The link mechanism may have three or more links connected in series. The link mechanism may be, for example, a robot arm, or may be something other than a robot arm. In the latter case, the link mechanism may be, for example, the legs of a quadruped robot, the arms or legs of a humanoid robot, or a link mechanism such as a crane. In this embodiment, the first stage unit 10 is the base end link, the second stage unit 20 is the link connected to the tip side of the first stage unit 10, and the third stage unit 30 is the link connected to the tip side of the second stage unit 20.

The first stage unit 10 includes an inverter 11 and a power transmission unit 12. The first stage unit 10 may be connected to a DC power source 13, for example, as shown in the circuit diagram of FIG. 2. As an example, the first stage unit 10 may be fixed to a base member 3 on the base end side, as shown in FIG. 3.

The inverter 11 converts DC power into AC power and outputs it to the power transmission unit 12. Note that this inverter 11 is a load-independent inverter. For information on load-independent inverters, see, for example, the above-mentioned non-patent document 2. As an example, the inverter 11 may be the circuit shown in FIG. 2. The inverter 11 shown in the circuit diagram of FIG. 2 is a class E inverter that is load-independent and has a constant voltage.

The power transmission unit 12 transmits the power converted to AC by the inverter 11 to the power receiving unit 21 of the second stage unit 20 in a non-contact manner. As an example, the power transmission unit 12 may be a series resonant type in which a capacitor and a coil are connected in series, as shown in FIG. 2.

The second stage unit 20 includes a power receiving unit 21, a rectifier 22, a power transmitting unit 23, and a load 24. The second stage unit 20 drives the load 24 with power received contactlessly from the first stage unit 10, and also transmits the power contactlessly to the third stage unit 30.

The power receiving unit 21 receives power contactlessly from the first stage unit 10. The received power is output to the rectifier 22 and the power transmitting unit 23. As an example, the power receiving unit 21 may be a parallel resonant unit in which a capacitor and a coil are connected in parallel, as shown in FIG. 2.

The rectifier 22 rectifies the AC power transmitted contactlessly and outputs DC power. The DC power is used by the load 24. The rectifier 22 is preferably one that does not have a reactance component in its input impedance. As an example, the rectifier 22 may be the circuit shown in FIG. 2. The rectifier 22 shown in the circuit diagram of FIG. 2 is a voltage-driven class D rectifier that has a constant output voltage.

The power transmitting unit 23 transmits the power received by the power receiving unit 21 to the third stage unit 30 in a non-contact manner. As an example, the power transmitting unit 23 may be a series resonant unit in which a capacitor and a coil are connected in series, as shown in FIG. 2.

The load 24 may be, for example, a motor that rotates the third stage unit 30 at a joint on the tip side of the second stage unit 20. As described later, when the non-contact power transmission device 1 is the circuit shown in FIG. 2, the output voltage of the rectifier 22 is constant, regardless of the load 24.

The third stage unit 30 includes a power receiving section 31, a rectifier 32, and a load 33. The third stage unit 30 drives the load 33 with power received contactlessly from the second stage unit 20. The third stage unit 30 is the tip link of the link mechanism. In this embodiment, a case where the third stage unit 30 has a gripping section at the tip side capable of gripping an object will be mainly described.

The power receiving unit 31 receives power from the second stage unit 20 in a non-contact manner. The received power is output to the rectifier 32. As an example, the power receiving unit 31 may be a parallel resonant unit in which a capacitor and a coil are connected in parallel, as shown in FIG. 2.

The rectifier 32 rectifies the AC power transmitted contactlessly and outputs DC power. The DC power is used by the load 33. Like the rectifier 22, the rectifier 32 is preferably one that does not have a reactance component in its input impedance. As an example, the rectifier 32 may be the circuit shown in FIG. 2. Like the rectifier 22, the rectifier 32 shown in the circuit diagram of FIG. 2 is a voltage-driven rectifier of class D with a constant output voltage.

The load 33 may be, for example, a motor of an opening/closing mechanism that opens and closes the gripping portion in the third-stage unit 30. As described later, when the non-contact power transmission device 1 is the circuit shown in FIG. 2, the output voltage of the rectifier 32 is constant, regardless of the load 33.

As shown in FIG. 3, at the connection between the first stage unit 10 and the second stage unit 20, power may be transmitted contactlessly between the power transmission coil 12a of the power transmission unit 12 and the power receiving coil 21a of the power receiving unit 21. Also, at the connection between the second stage unit 20 and the third stage unit 30, power may be transmitted contactlessly between the power transmission coil 23a of the power transmission unit 23 and the power receiving coil 31a of the power receiving unit 31.

The power transmission coil 12a and the power receiving coil 21a may each be cylindrical, and the rotation axis 41 of the joint may be the central axis of the cylindrical shape, with the coils 12a and 21a facing each other in the axial direction. By disposing the power transmission coil 12a and the power receiving coil 21a in this manner, the positional relationship between the two coils does not change even if the joint rotates around the rotation axis 41. Therefore, the coupling coefficient between the power transmission unit 12 and the power receiving unit 21 does not change and remains constant even if the joint rotates around the rotation axis 41. The same is true for the power transmission coil 23a and the power receiving coil 31a and the rotation axis 42. In order for the output of each rectifier 22, 32 to be a constant voltage or current, it is preferable that the coupling coefficient between the power transmission unit and the power receiving unit used in non-contact power transmission between the two units does not change and remains constant.

Next, the selection of the resonance form according to the output form of the rectifier will be described. In the contactless power transmission device 1 according to the present embodiment, since the inverter 11 of the base unit, i.e., the first-stage unit 10, is a load-independent inverter, the output of the rectifier 22 on the rear stage side is a constant voltage or a constant current, and the output of the rectifier 32 is also a constant voltage or a constant current. Here, as a result of intensive research, the inventor has found that in contactless power transmission, there is a relationship shown in the table of FIG. 4 among the transmission mode of the front stage side, the resonance form of the power transmission unit on the front stage side (primary side), the resonance form of the power receiving unit on the rear stage side (secondary side), the type of the rectifier on the rear stage side, and the power receiving mode on the rear stage side. The ID in the table of FIG. 4 is for identifying a combination of the transmission mode, etc. The transmission mode is the output form of the rectifier and inverter in the front stage unit. The power receiving mode is the output form of the rectifier in the rear stage unit. The front stage side refers to the base end side.

In the table of FIG. 4, the combinations of IDs "2", "4", "6", and "8" have the same power transmission mode and power receiving mode, and it can be seen that the resonance form on the power transmitting side and the resonance form on the power receiving side are a combination of series resonance and parallel resonance. Therefore, in non-contact power transmission, if it is not desired to change the output form of the unit on the front stage and the output form of the unit on the rear stage, non-contact power transmission can be performed by a combination of series resonance and parallel resonance using the power transmitting unit and power receiving unit between the two units. In other words, non-contact power transmission can be performed between the two units using a series resonant power transmitting unit and a parallel resonant power receiving unit, or a parallel resonant power transmitting unit and a series resonant receiving unit.

On the other hand, in the combinations of IDs "1", "3", "5", and "7", the transmission mode and the reception mode are reversed, and it can be seen that the resonance form on the transmission side and the resonance form on the reception side are a combination of series resonances, or a combination of parallel resonances. Therefore, in non-contact power transmission, if you want to change the output form of the unit on the front side and the unit on the rear side, you can perform non-contact power transmission with the same combination of resonance forms using the power transmission unit and power receiving unit between the two units. In other words, you can perform non-contact power transmission between the two units using a series resonance power transmission unit and a series resonance power receiving unit, or a parallel resonance power transmission unit and a parallel resonance receiving unit.

In this way, the output form of the rectifier on the subsequent stage, i.e., constant voltage or constant current, can be determined according to the combination of resonance forms for contactless power transmission. Therefore, the resonance form in contactless power transmission can be appropriately adopted according to the desired output form of the rectifier of each unit. For example, if it is desired to make the output form of the subsequent stage the same as the output form of the preceding stage, a combination of series resonance and parallel resonance can be adopted in contactless power transmission. Also, for example, if it is desired to make the output form of the subsequent stage different from the output form of the preceding stage, the same combination of resonance forms can be adopted in contactless power transmission.

Normally, it is thought that the rectifiers of each unit are all aligned to output a constant voltage or all aligned to output a constant current. This is because it is thought that similar loads (for example, motors for rotating joints in a link mechanism) are often used for all units having rectifiers. In this case, it is sufficient to perform non-contact power transmission between two units by combining series resonance and parallel resonance using the power transmitting unit and power receiving unit. Note that since it is thought that there are many loads that are driven by power with a constant voltage, it is thought that the output of each rectifier is usually made constant voltage. On the other hand, if the output of the rectifier is constant current, it is possible to obtain the effect of preventing overcurrent.

In the contactless power transmission device 1 shown in the circuit diagram of FIG. 2, the power transmission unit 12 is series resonant and the power receiving unit 21 is parallel resonant, so the output form of the rectifier 22 is the same constant voltage as the inverter 11. Also, since the power transmission unit 23 is series resonant and the power receiving unit 31 is parallel resonant, the output form of the rectifier 32 is the same constant voltage as the rectifier 22. Therefore, in the contactless power transmission device 1 shown in FIG. 2, the voltage is uniformly constant in each of the units 10 to 30. The output voltages of the rectifiers 22 and 32 may be the same or different.

As an example of a circuit diagram other than FIG. 2, the circuit diagram of FIG. 5 will be briefly described. In the circuit diagram of FIG. 5, the inverter 11 is a class EF inverter that is load-independent and has a constant current. The rectifiers 22 and 32 are current-driven class D rectifiers that have a constant output voltage. In the circuit diagram of FIG. 5, the power transmission unit 12 is series resonant, and the power receiving unit 21 is also series resonant. The power transmission unit 23 is parallel resonant, and the power receiving unit 31 is series resonant. Therefore, the output form changes due to the contactless power transmission between the first stage unit 10 and the second stage unit 20, and the inverter 11 has a constant current, but the output of the rectifier 22 has a constant voltage as described above. In addition, the output form does not change in the contactless power transmission between the second stage unit 20 and the third stage unit 30, so the output of the rectifier 32 has a constant voltage as described above, just like the rectifier 22. As in the example circuit diagram of Figure 5, even if the outputs of the rectifiers 22, 32 of the units 20, 30 in the second stage and onwards are uniform and have a constant voltage, the output of the inverter 11 of the unit 10 in the first stage may be a constant current. In this way, various specific circuits can be adopted for the contactless power transmission device 1 according to this embodiment.

When designing the contactless power transmission device 1 according to this embodiment, first, it is determined whether the rectifier of each unit is to be constant voltage or constant current, and the load-independent inverter 11 of the first stage unit is determined to be constant voltage or constant current. Next, the combination of resonance forms in each contactless power transmission is determined so that the output form of the rectifier of the second stage unit is determined according to the determination. Note that the combination of resonance forms may be selected from the combination of different resonance forms and the combination of the same resonance form according to the output form. There are two combinations of different resonance forms, and two combinations of the same resonance form. Therefore, there are two options for the combination of resonance forms in each contactless power transmission, which the designer can freely select.

As described above, according to the non-contact power transmission device 1 of the present embodiment, load independence can be achieved when transmitting power in multiple stages by non-contact power transmission. In addition, the rectifier of each unit can be made to have a desired output form by making the power transmission unit and the power receiving unit perform non-contact power transmission by combining the resonance forms according to the output form of the rectifier. For example, the output of all rectifiers can be made to be constant voltage. In addition, for example, the output of the rectifier can be made to alternately repeat constant voltage and constant current from the base end side. In addition, for example, only the output of the rectifier of a unit of a specific stage can be made to be constant current, and the output of the other rectifiers can be made to be constant voltage. In addition, since the inverter 11 is load independent, switching loss can be made zero with respect to load fluctuations. As a result, power transmission at high frequencies is possible, and the non-contact power transmission device 1 can be made smaller and lighter.

In the present embodiment, the contactless power transmission device 1 is mainly described as being composed of three units as shown in Figures 1 and 2, but this is not essential. The contactless power transmission device 1 may have N units, from a first stage unit to an Nth stage unit, where N is an integer equal to or greater than 3. In this case, as in the above description, each rectifier can be made to have the desired output form by selecting a combination of resonance forms in each contactless power transmission according to the output form of each rectifier in the second stage unit to the Nth stage unit.

In addition, in this embodiment, the case where all the units from the second stage onwards have a rectifier has been described, but this is not necessary. One or more units from the second stage to the Nth stage may not have a rectifier. Even in this case, one or more units from the second stage to the Nth stage are assumed to have a rectifier. This is because output cannot be obtained otherwise. Note that a unit that does not have a rectifier usually does not have a load driven by the output power of the rectifier. Also, a unit that does not have a rectifier and a load may have a circuit in which the rectifier 22 and the load 24 are deleted from the second stage unit 20 in FIG. 2, for example. In other words, a unit that does not have a rectifier and a load may be a unit that has a power receiving unit and a power transmitting unit. Note that if the Nth stage unit does not have a rectifier, it is considered that there is no need to transmit power to the Nth stage unit, so the Nth stage unit may have a rectifier. Even if there is a unit that does not have a rectifier, the combination of resonance forms for contactless power transmission can be determined in the same way as when each unit from the second stage onwards has a rectifier. However, in units that do not have a rectifier, two patterns of constant voltage and constant current can be assumed, so the flexibility of the combination of resonance forms increases.

In addition, in this embodiment, the case where each unit is a link and each unit that is a link is connected by a joint to form a link mechanism has been mainly described, but this is not necessarily the case. The contactless power transmission device 1 according to this embodiment may be used in multi-stage contactless power transmission other than a link mechanism.

In addition, in the above embodiments, each process or function may be realized by centralized processing in a single device or a single system, or may be realized by distributed processing in multiple devices or multiple systems.

Furthermore, the present invention is not limited to the above-described embodiment, and various modifications are possible, and it goes without saying that these are also included within the scope of the present invention.

As described above, the non-contact power transmission device according to one aspect of the present invention has the effect of realizing multi-stage non-contact power transmission independent of the load, and is useful, for example, as a device for non-contact power transmission in a link mechanism having multiple links.

REFERENCE SIGNS LIST 1 non-contact power transmission device 10 first stage unit 11 inverter 12, 23 power transmission section 20 second stage unit 21, 31 power reception section 22, 32 rectifier 24, 33 load 30 third stage unit

Claims (4)

A non-contact power transmission device that transmits power in multiple stages by non-contact power transmission,
A first stage unit having a load-independent inverter and a power transmission unit that transmits, in a non-contact manner, the power converted into AC by the inverter;
A second to (N-1)th stage unit has a power receiving unit that receives power from a previous stage unit in a non-contact manner and a power transmitting unit that transmits power to a subsequent stage unit in a non-contact manner;
An N-th stage unit having a power receiving unit that receives power from the N-1-th stage unit in a non-contact manner,
N is an integer of 3 or more,
At least one unit among the second stage to the Nth stage units has a rectifier that rectifies AC power transmitted in a non-contact manner and outputs a constant voltage or a constant current,
The power transmitting unit and the power receiving unit perform contactless power transmission by series resonance or parallel resonance in response to a constant voltage or current at the output of the rectifier. The rectifiers all output a constant voltage or all output a constant current;
The contactless power transmission device according to claim 1 , wherein contactless power transmission between the two units is performed by a combination of series resonance and parallel resonance using the power transmitting section and the power receiving section. A non-contact power transmission device according to claim 1 or claim 2, wherein two or more of the units in the second stage to the Nth stage have the rectifier. the unit is a link,
the first stage to the Nth stage units are connected by joints to form a link mechanism;
The contactless power transmission device according to claim 1 , wherein contactless power transmission is performed at the connection point.

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