JP2014001642A - Motor-driven compression device and air supply device for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply a compressed gas of a small discharge amount stably as needed, the compressed gas being discharged when the speed of a rotating shaft of an electric motor is equal to or lower than a floating point rotation speed where the rotating shaft is floated from a radial foil bearing.SOLUTION: A motor-driven compression device 1 comprises: a circulation flow passage 16 connecting an intake port 13 through which a gas is taken in by rotating an impeller 11 of the motor-driven compression device 1, and a discharge flow passage 14 where a compressed gas is discharged by rotating the impeller 11; a rotation speed detector 18 for detecting the rotation speed of rotating shafts 7a and 7b; and a controller 20 which controls opening/closing of a valve 17 based on the rotation speed detected by the rotation speed detector 18. The controller 20 performs control to open the valve 17 when a discharge amount further smaller than the floating point discharge amount of the compressed gas which is discharged in accordance with the floating point rotation speed at which the rotating shafts 7a and 7b are floated from radial foil bearings 8a and 8b is required in the state where the rotating shafts 7a and 7b are rotated at the rotation speed floating the rotating shafts 7a and 7b from the radial foil bearings 8a and 8b.

Description

  The present invention relates to an electric compressor and an air supply device for a fuel cell.

  In recent years, without burning fuel, a fuel cell is provided, and electric power is generated by electrochemically reacting oxygen, hydrogen, alcohol, and other fuels in the air, and the electric motor is rotated by the generated power. The development of fuel cell vehicles is progressing. As an apparatus for supplying air to a fuel cell, an electric motor having a rotor and a stator, and a centrifuge that takes in external air and compresses it by rotating an impeller by a rotating shaft fixed to the rotor of the electric motor. An air supply device for a fuel cell that includes an electric compression device having a compressor and supplies compressed air compressed by the electric compression device to a fuel cell stack of a fuel cell via an air supply path is used. .

  In the electric compressor, the impeller of the centrifugal compressor is rotated at a high speed of about tens of thousands of revolutions / minute or more in order to compress the air to a required pressure and supply it to the fuel cell. For this reason, the bearing of the rotating shaft of the electric motor is not a normal rolling bearing or the like, but a foil bearing or the like is used to support a radial load in a non-contact state during high-speed rotation.

  In a fuel cell, hydrogen and air humidified by an air humidifier are supplied to the fuel cell stack to generate electric power by an electrochemical reaction. However, when oil or the like is mixed into the air and hydrogen supplied to the fuel cell stack. Therefore, it is known that the power generation efficiency is significantly reduced. For this reason, the electric motor of the electric compression device includes a radial foil bearing that does not use oil to support the rotating shaft, and an axial foil bearing or an axial magnetic bearing. Is being used.

  A pair of radial foil bearings are provided on both sides of the rotating shaft across the rotor of the electric motor of the electric compressor to support the load in the radial direction of the rotating shaft in a non-contact manner, and the rotating shaft and the electric motor are sandwiched between the stator. There is a fuel cell air supply device in which a pair of axial magnetic bearings are provided between a main body and a load in the longitudinal direction of a rotary shaft is supported in a non-contact manner (see, for example, Patent Document 1).

  In the radial foil bearing, one or two or more foil segments made of a very thin metal foil or the like are attached to the inner surface of the hole through which the rotating shaft passes. Therefore, in the radial foil bearing, until the rotational speed of the rotating shaft to be supported reaches a predetermined value, the foil segment directly contacts the outer peripheral surface of the rotating shaft to support the rotating shaft from the radial direction. After the rotational speed of the rotating shaft reaches a predetermined value or more, the rotating shaft floats from the surface of the foil segment over the entire circumference by the dynamic pressure generated between the outer peripheral surface of the rotating shaft and the foil segment. It is designed to be supported in contact.

JP 2010-168904 A

  As shown in Patent Document 1, in an electric compression apparatus having a radial foil bearing, when the electric compression apparatus is started from a stopped state, a large driving torque is required until the rotating shaft reaches the levitation rotation speed (the levitation rotation speed). This is necessary, and since the drive torque (power) rapidly decreases at the moment when the rotation shaft reaches the ascent point rotation speed, the rotation shaft rotates at high speed, so the stable rotation speed in a transient situation It had the problem that it was difficult to control. In a centrifugal compressor equipped with an impeller, a discharge amount of compressed gas corresponding to the number of rotations of the rotating shaft (the number of rotations of the impeller) can be obtained, so the discharge amount of the compressed gas is also stable in a transient situation. Control is difficult.

  In the fuel cell, there may be a case where a small discharge amount of compressed air is required, such as compressed air discharged when the rotating shaft of the electric compression device is below the floating point rotation speed rising from the radial foil bearing, Conventional electric compressors cannot stably supply such a small discharge amount of compressed air.

  The present invention has been made in view of the above-described conventional problems, and when a small discharge amount of compressed gas is required to be discharged when the rotation shaft of the electric motor is below the ascent speed at which it floats from the radial foil bearing. It is an object of the present invention to provide an electric compressor and an air supply device for a fuel cell that can be stably supplied.

The present invention provides a rotor, a stator that interacts with the rotor and generates a rotational moment in the rotor, a rotating shaft that transmits the rotation of the rotor to the outside, and the rotating shaft that is rotatably supported. Electric compression having a radial foil bearing, an impeller that rotates integrally with the rotating shaft, a suction port that takes in gas by the rotation of the impeller, and a discharge passage that discharges compressed gas compressed by the rotation of the impeller A device,
A circulation flow path connecting the suction port and the discharge flow path;
A valve provided in the circulation channel, a rotation speed detector for detecting the rotation speed of the rotary shaft, and a controller for controlling opening and closing of the valve based on the rotation speed detected by the rotation speed detector; And
In the state in which the rotating shaft is rotated at the rotational speed at which the rotary shaft is levitated from the radial foil bearing, the controller is configured to obtain a floating point discharge amount of a compressed gas discharged at a floating point rotational speed at which the rotary shaft is levitated from the radial foil bearing. Further, the present invention relates to an electric compressor that performs control to open the valve when a smaller discharge amount is required.

  In the above-described electric compressor, the valve is a flow rate adjusting valve, and a flow rate detector for detecting a discharge flow rate of the compressed gas is provided in the discharge flow path, and the controller has the rotary shaft having the radial foil bearing. When a discharge amount smaller than the floating point discharge amount of the compressed gas discharged by the floating point rotation number at which the rotary shaft floats from the radial foil bearing is It is preferable to perform control to open the flow rate control valve so as to obtain a discharge amount.

  The present invention relates to a fuel cell air supply device, wherein the discharge passage in the electric compressor is connected to an air humidifier of a fuel cell.

  According to the electric compressor and the fuel cell air supply device of the present invention, the rotating shaft rotates at a high rotational speed that is higher than the floating point rotational speed rising from the radial foil bearing, and a large amount of compressed gas is discharged. Sometimes, by opening a valve provided in the circulation flow path, a compressed gas having a discharge amount smaller than the floating point discharge amount of the compressed gas discharged by the floating point rotation speed at which the rotating shaft floats from the radial foil bearing. It is possible to achieve an excellent effect that it can be stably supplied when necessary.

(A) is a schematic block diagram which shows one Example of the electrically-driven compression apparatus of this invention, (b) is a schematic block diagram at the time of providing the opening-and-closing valve instead of the flow regulating valve provided in (a). It is explanatory drawing which showed the state from which the rotation speed of the rotating shaft supported by the radial foil bearing and the discharge amount of compressed gas changed. It is a block diagram which shows an example of the fuel cell to which the air supply apparatus for fuel cells which has the electric compressor of this invention is applied.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 3 is a block diagram in which the fuel cell air supply device 3 having the electric compressor 1 of the present invention is applied to a fuel cell 30. The fuel cell 30 shown in FIG. 3 includes a fuel cell stack 31 and the fuel cell stack. A power controller 32 for controlling the power supplied from the fuel cell 31; a high-pressure hydrogen tank 33 and a hydrogen pump 34 for supplying hydrogen to the fuel cell stack 31; A humidifier 35 and a cooler 36 for cooling the fuel cell stack 31 and the power controller 32 are provided. Then, the electric motor 37 that drives the vehicle by the electric power generated by the electrochemical reaction between hydrogen and air in the fuel cell stack 31 and controlled by the electric power controller 32 is driven.

  The electric compressor 1 takes in air from the outside and compresses it, and supplies the compressed air compressed by the electric compressor 1 to the air humidifier 35 of the fuel cell 30 via the air supply path 2. Thus, the fuel cell air supply device 3 is configured.

  In the fuel cell 30, hydrogen in the high-pressure hydrogen tank 33 is supplied to the fuel cell stack 31 via the hydrogen pump 34, and compressed air obtained by compressing air by the electric compressor 1 of the fuel cell air supply device 3 is air. The humidified air is supplied to the fuel cell stack 31 by being supplied to the air humidifier 35 via the supply system 2, and the electrochemical reaction between the hydrogen in the fuel cell stack 31 and the humidified air is performed. To generate electricity.

  FIG. 1A is a schematic configuration diagram showing an embodiment of an electric compression device of the present invention. The electric compression device 1 of FIG. 1A includes a rotor 4 and the rotation inside a casing 22. An electric motor 6 including a stator 5 that interacts with the rotor 4 and generates a rotational moment in the rotor 4 is provided. On the both sides in the axial direction of the rotor 4, rotary shafts 7a and 7b are provided. There is an output shaft 7 for transmitting the rotation to the outside on one of the rotation shafts 7a.

  The rotary shafts 7a and 7b are supported by radial foil bearings 8a and 8b having the foil segments in a non-contact manner in the radial direction, and a magnetic disk 9 and a casing fixed to the rotary shafts 7a and 7b. Axial magnetic bearings 10a and 10b each including an electromagnet 9 'fixed to 22 support the shafts in the longitudinal direction of the rotary shafts 7a and 7b so that they can rotate without contact.

  An impeller 11 is fixed to the outer end portion of the output shaft 7, and the gas (air) that has passed through the air cleaner 12 is taken in from the suction port 13 by the rotation of the impeller 11 and compressed, and the compressed compressed air is discharged. A centrifugal compressor 15 that discharges from the passage 14 is configured. The compressed air discharged from the discharge flow path 14 of the centrifugal compressor 15 is supplied to the air humidifier 35 of the fuel cell 30 via the air supply system path 2 of FIG.

  A centrifugal compressor 15 shown in FIG. 1A is provided with a circulation channel 16 that connects the suction port 13 and the discharge channel 14, and a valve 17 is provided in the middle of the circulation channel 16. The valve 17 shown to Fig.1 (a) has shown the case of the flow control valve 17a.

  In the electric compressor 1, a rotational speed detector for detecting the rotational speed of the rotary shafts 7a and 7b is provided. FIG. 1A shows a case where a rotation speed detector 18 for detecting the rotation speed of the rotary shafts 7a and 7b by counting the impeller 11 of the centrifugal compressor 15 is provided. A rotary encoder or the like that detects the number of rotations may be provided. A flow rate detector 19 for detecting the discharge flow rate of the compressed air discharged from the discharge flow path 14 is provided.

  A controller 20 is provided to which the rotational speed 18a of the rotary shafts 7a and 7b detected by the rotational speed detector 18 and the discharge flow rate 19a of the compressed air detected by the flow rate detector 19 are input. 20, a discharge amount smaller than the floating point discharge amount when the rotating shafts 7 a, 7 b float at the floating point rotational speed at which they float from the radial foil bearings 8 a, 8 b is input as the request command 21. .

  When a request command 21 for a discharge amount smaller than the floating point discharge amount when the rotating shafts 7a, 7b are at the floating point rotational speed at which the rotary shafts 7a, 7b float from the radial foil bearings 8a, 8b is input to the controller 20. The controller 20 outputs a control signal 20 ′ to the flow control valve 17a so that the discharge flow rate of the compressed gas becomes the request command 21, and opens the flow control valve 17a to control its opening degree. Yes.

  Further, in place of the flow rate adjusting valve 17a shown in FIG. 1A, an on-off valve 17b may be provided as shown in FIG. FIG.1 (b) has shown the case where the on-off valve 17b by an electromagnetic valve is provided.

  Next, the operation of the above embodiment will be described.

  1 is often controlled in a wide range from a low speed to a high speed in accordance with the traveling state of the fuel cell automobile. In the electric compressor 1, in particular, rotation in a state where the foil segments of the radial foil bearings 8a and 8b are in direct contact with the outer peripheral surfaces of the rotary shafts 7a and 7b and support the rotary shafts 7a and 7b from the radial direction (low-speed rotation). When the control is carried out so as to continue for a long time, when the foil segment wears in a short period of time and the wear amount increases, the characteristics for floating the rotary shafts 7a and 7b by the radial foil bearings 8a and 8b deteriorate. Can be lost or lost.

  FIG. 2 shows a state in which the rotation speed of the rotation shafts 7a and 7b and the discharge amount of the compressed gas change when the rotation of the rotation shafts 7a and 7b of the electric compressor 1 increases from the start up to a predetermined rotation speed. In the figure, the solid line indicates the rotation speed, and the alternate long and short dash line indicates the discharge amount. When the rotation of the rotating shafts 7a and 7b in the stopped state is started by the electric motor 6, since a large driving torque is required to reach the floating point rotational speed S1, the rotational speed gradually increases and the surface is lifted. The driving torque (power) decreases at the moment when the rotational speed 7a, 7b rises after reaching the point rotational speed S1, so that the rotational speed is rapidly increased and reaches a predetermined rotational speed S2. In the centrifugal compressor 15, since the discharge amount of the compressed air corresponding to the rotation speed of the impeller 11 is obtained, the discharge amount of the compressed air is the rotation speed at which the rotary shafts 7a and 7b are lifted as shown by the one-dot chain line in FIG. When it reaches S1, it becomes the floating point discharge amount Q1, and when the rotating shafts 7a, 7b rotate at a predetermined rotation speed S2 that is equal to or higher than the floating point rotation number S1, it becomes a predetermined discharge amount Q2.

  When the rotary shafts 7a and 7b are rotating at a rotational speed equal to or higher than the floating point rotational speed S1, the electric compressor 1 can discharge a compressed amount of compressed air corresponding to the rotational speed of the rotary shafts 7a and 7b. it can.

  In the conventional electric compressor, when the rotary shafts 7a and 7b are rotated at a predetermined rotational speed S2 higher than the floating point rotational speed S1 of the radial foil bearings 8a and 8b in FIG. Even when compressed air having a discharge amount smaller than the floating point discharge amount Q1 when the rotary shafts 7a and 7b are at the floating point rotation speed S1 is required, such a small discharge amount of compressed air could not be supplied. .

  On the other hand, in the present invention, when the rotary shafts 7a and 7b rotate at a predetermined rotational speed S2 higher than the floating point rotational speed S1 and discharge compressed air of a predetermined discharge amount Q2, the rotational shaft When a request command 21 for a discharge amount smaller than the floating point discharge amount Q1 at the rising point rotational speed S1 at which the floating points 7a and 7b rise is input to the controller 20 in FIG. 1, the controller 20 adjusts the flow rate. Control to open the valve 17a is performed.

  When the flow rate adjusting valve 17a is opened, a part of the compressed air discharged to the discharge flow path 14 is sucked into the suction port 13 of the impeller 11 through the circulation flow path 16 and circulates. The amount of compressed air supplied to the air humidifier 35 of the fuel cell 30 in FIG. 3 via the path 2 decreases.

  Here, the circulation amount of the compressed air that circulates to the suction port 13 of the impeller 11 through the circulation channel 16 is the pressure of the compressed air that is discharged to the discharge channel 14 and the pressure of the suction port 13 by the impeller 11 (negative pressure). ), And stabilizes to a predetermined value depending on conditions such as the diameter of the circulation channel 16.

  Therefore, when the rotating shafts 7a and 7b are rotated at a high rotational speed S2 which is higher than the floating point rotational speed S1 in FIG. 2 and floats from the radial foil bearings 8a and 8b, compressed gas having a large discharge amount Q2 is discharged. When the valve 17 is opened, a compressed gas having a discharge amount Q ′ that is smaller than the floating point discharge amount Q1 of the compressed gas discharged by the floating point rotation speed S1 at which the rotary shafts 7a and 7b rise from the radial foil bearings 8a and 8b. When necessary, it can be stably supplied to the air humidifier 35 of the fuel cell 30. Further, when the valve 17 is controlled to be closed by the controller 20 shown in FIG. 1, the circulation flow path 16 is closed, and as shown in FIG. 2, the compressed gas having a small discharge amount Q ′ becomes a predetermined discharge amount Q2. To return to.

  When the valve 17 is a flow rate adjusting valve 17a as shown in FIG. 1 (a), by adjusting the opening of the flow rate adjusting valve 17a and adjusting the amount of compressed gas circulated by the circulation flow path 16, The supply amount of the compressed air supplied to the air humidifier 35 of the fuel cell 30 can be adjusted with a certain change width.

  Further, as shown in FIG. 1B, when the valve 17 is an on-off valve 17b, a part of the compressed air in the discharge passage 14 is made to pass through the circulation passage 16 by opening the on-off valve 17b. Since the air is sucked into the inlet 13 of the impeller 11 and circulates, the supply amount of compressed air supplied to the air humidifier 35 of the fuel cell 30 decreases to a predetermined value.

  As described above, when the valve 17 is opened and the compressed gas having a small discharge amount Q ′ is supplied to the fuel cell 30, the temperature of the compressed air circulating to the impeller 11 through the circulation channel 16 rises. However, since the power generation efficiency increases when the temperature of the compressed air supplied to the fuel cell 30 through the air humidifier 35 is high, it is effective that the temperature of the compressed air rises due to the circulation.

  Further, when the operation of opening the valve 17 is performed when starting the electric compressor 1, the compressed gas compressed by the impeller 11 of the centrifugal compressor 15 and discharged to the discharge passage 14 passes through the circulation passage 16. Since the suction load of the impeller 11 is reduced by being circulated through the suction port 13 of the impeller 11, the rotational speed of the rotating shafts 7a and 7b is smaller than that of the conventional one as shown by the broken line A in FIG. Thus, the flying point rotation speed S1 is reached in a short time. As described above, the time until the rotating shafts 7a and 7b reach the levitation point rotational speed S1 is shortened, so that the foil segments of the radial foil bearings 8a and 8b are worn in a short time by rotating at a low speed. Can be reduced.

  The electric compressor and the fuel cell air supply device of the present invention are not limited to the above-described embodiments, and various modifications may be made without departing from the scope of the present invention. .

DESCRIPTION OF SYMBOLS 1 Electric compressor 3 Air supply apparatus for fuel cells 4 Rotor 5 Stator 7a, 7b Rotating shaft 8a, 8b Radial foil bearing 11 Impeller 13 Suction port 14 Discharge flow path 16 Circulation flow path 17 Valve 17a Flow control valve 18 Number of rotations Detector 18a Rotational speed 20 Controller 21 Request command 30 Fuel cell 35 Air humidifier Q1 Floating point discharge amount Q2 Predetermined discharge amount Q ′ Small discharge amount S1 Floating point rotational speed S2 Predetermined rotational speed

Claims (3)

A rotor, a stator that interacts with the rotor and generates a rotational moment in the rotor, a rotating shaft that transmits the rotation of the rotor to the outside, and a radial foil bearing that rotatably supports the rotating shaft; An electric compressor having an impeller that rotates integrally with the rotating shaft, a suction port that takes in gas by the rotation of the impeller, and a discharge passage that discharges compressed gas compressed by the rotation of the impeller. ,
A circulation flow path connecting the suction port and the discharge flow path;
A valve provided in the circulation channel, a rotation speed detector for detecting the rotation speed of the rotary shaft, and a controller for controlling opening and closing of the valve based on the rotation speed detected by the rotation speed detector; And
In the state in which the rotating shaft is rotated at the rotational speed at which the rotary shaft is levitated from the radial foil bearing, the controller is configured to obtain a floating point discharge amount of a compressed gas discharged at a floating point rotational speed at which the rotary shaft is levitated from the radial foil bearing. An electric compressor characterized by performing control to open the valve when a smaller discharge amount is required.   The valve is a flow rate adjusting valve, and a flow rate detector for detecting a discharge flow rate of the compressed gas is provided in the discharge flow path, and the controller has a rotational speed at which the rotating shaft floats from the radial foil bearing. In the rotated state, when the discharge amount smaller than the floating point discharge amount of the compressed gas discharged by the floating point rotational speed at which the rotating shaft ascends from the radial foil bearing is requested, the discharge amount of the request command is obtained. The electric compressor according to claim 1, wherein control for opening the flow rate control valve is performed.   3. An air supply device for a fuel cell, wherein the discharge flow path in the electric compressor according to claim 1 or 2 is connected to an air humidifier of the fuel cell.

Images