Fuel cell system

Patent metadata

Field	Value
Publication number	US-9947948-B2
Application number	US-201314403810-A
Country	US
Kind code	B2
Filing date	May 28, 2013
Priority date	Jun 1, 2012
Publication date	Apr 17, 2018
Grant date	Apr 17, 2018

Abstract

A fuel cell system includes a compressor provided in a cathode gas supply passage configured to feed the cathode gas under pressure to the fuel cell, a bypass passage configured to discharge the cathode gas fed under pressure by the compressor to a cathode gas discharge passage while bypassing the fuel cell, a bypass valve provided in the bypass passage and configured to adjust a flow rate of the cathode gas flowing in the bypass passage, a system stopping unit configured to stop the fuel cell system by performing a predetermined stop sequence process when a request to stop the fuel cell system is made, and a stop-time bypass valve control unit configured to control a valve body of the bypass valve to a predetermined initialization position in parallel with the sequence process during the stop sequence process.

First claim

The invention claimed is:

1. A fuel cell system configured to generate power by supplying anode gas and cathode gas to a fuel cell, comprising:
a compressor provided in a cathode gas supply passage and configured to feed the cathode gas under pressure to the fuel cell;
a bypass passage configured to discharge a portion of the cathode gas fed under pressure by the compressor to a cathode gas discharge passage while bypassing the fuel cell;
a cathode gas discharge passage in which the cathode gas discharged from the fuel cell flows, the cathode gas discharge passage being connected to the bypass passage;
an anode gas discharge passage in which an anode gas discharged from the fuel cell flows, the anode gas discharge passage being connected to the cathode gas discharge passage;
a bypass valve provided in the bypass passage and configured to adjust a flow rate of the cathode gas flowing in the bypass passage;
a system stopping unit configured to stop the fuel cell system by performing a predetermined stop sequence process when a request to stop the fuel cell system is made;
a stop-time bypass valve control unit configured to perform a stop-time full closing process, the stop-time full closing process being a process of controlling a valve body of the bypass valve to a fully closed initialization position in a voltage limiting process during the stop sequence process for reducing a voltage of the fuel cell after the compressor is stopped; and
a stepping motor configured to drive the bypass valve;
a determination unit configured to determine whether or not the stop-time full closing process has been performed by the stop-time bypass valve control unit; and
a minimum initialization unit configured to rotate the stepping motor after the stop sequence process, wherein:
the stop-time bypass valve control unit is further configured to:
start to control the bypass valve during the voltage limiting process; and
control a rotation speed of the stepping motor so that the rotation speed when a step number of the stepping motor is lower than a predetermined step number becomes slower than the rotation speed when the step number of the stepping motor is higher than the predetermined step number; and

the minimum initialization unit is further configured to:
when the determination unit determines that the stop-time full closing process has been performed, rotate the stepping motor by an initialization step number smaller than a fully open step number; and
when the determination unit determines that the stop-time full closing process has not been performed, rotate the stepping motor by the fully open step number.

2. The fuel cell system according to claim 1 , further comprising:
a strong electric battery; and
a weak electric battery having a lower electromotive force than the strong electric battery, wherein the stop sequence process includes:
a power generation stopping process for stopping power generation in the fuel cell after the voltage limiting process is finished, the power generation stopping process including:
a strong electric stopping process for stopping the supply of power from the strong electric battery after the voltage limiting process is finished, and
a weak electric stopping process for stopping the supply of power from the weak electric battery after the strong electric stopping process is finished; and
the stop-time bypass valve control unit starts the control of the bypass valve so as to be able to control the bypass valve to the initialization position before the weak electric stopping process is started.

3. The fuel cell system according to claim 1 , wherein:
the stop-time bypass valve control unit sets a moving speed of the bypass valve slower than a speed of moving a valve body of the bypass valve to a predetermined position when a valve body position of the bypass valve reaches the predetermined position near the initialization position.

4. The fuel cell system according to claim 1 , wherein:
the stop-time bypass valve control unit determines that the compressor has stopped when a rotation speed of the compressor drops to or below a predetermined speed.

5. The fuel cell system according to claim 1 , wherein, during control of the bypass valve during the voltage limiting process, the stop-time bypass valve control unit is further configured to:
determine a step number of the stepping motor of the bypass valve;
determine an initialization step number; and
if the step number is larger than the initialization step number, rotate the stepping motor at a normal rotation speed to reach the initialization step number; and
if the step number is smaller than the initialization step number, rotate the stepping motor at a slower than normal speed until the step number is zero.

6. The fuel cell system according to claim 1 , wherein the stop-time bypass valve control unit is further configured to:
on condition that the step number is larger than the predetermined step number, rotate the stepping motor at a first rotation speed; and on condition that the step number is smaller than the initialization step number, rotate the stepping motor at a second rotation speed that is slower than the first rotation speed.

Assignees

• Nissan Motor

Inventors

• Shimada Kazuhide
• Chikugo Hayato

Classifications

• H01M8/04089 Primary

  of gaseous reactants · CPC title

• H01M8/04303

  applied during shut-down · CPC title

• H01M8/0488

  of fuel cell stacks · CPC title

• H01M8/04955

  Shut-off or shut-down of fuel cells · CPC title

• H01M8/2457

  with both reactants being gaseous or vaporised · CPC title