JP2000315515A - Compressor control device of fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compressor control device of fuel cell system capable of putting a compressor in a dry condition certainly and of minimizing the amount of power consumption of a secondary battery used to drive the compressor. SOLUTION: When system is stopped, a controller 27 judges whether the temp. T1 discharged from the outlet of a compressor 5 has exceeded the specified level, or the temporal varying rate of the discharged air temp. T1 has exceeded its specified value, and if at least one of these conditions is met, a presumption is made that inside the compressor 5 is in dry condition, and in this case, control is executed so that the compressor 5 is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compressor control device for a fuel cell system capable of preventing breakage due to freezing of water remaining in the compressor after the system is stopped.

[0002]

2. Description of the Related Art As a conventional compressor control device of a fuel cell system, a compressor having a water injection mechanism is known.

If water injected into the compressor case remains after the system is stopped, the water freezes in the case, so it is important to drain the water from the case to prevent damage to the compressor. is there. For this reason, a method is employed in which the compressor is operated for a fixed time to dry the water after the system is stopped.

[0004]

However, in a situation where the water remaining in the compressor case freezes, the temperature of the secondary battery provided for supplying power to the compressor becomes low. Since the power capacity that can be taken out is extremely smaller than at room temperature, there is a limit to the usage time of the secondary battery.

[0005] In the conventional compressor control device for a fuel cell system, the compressor is operated for a certain period of time after the system is stopped to dry the inside of the compressor case.
For this reason, there has been a problem that the compressor continues to be operated more than necessary and the power of the secondary battery is consumed.

Further, even if the inside of the compressor case is dried for a certain period of time, if the operation of the compressor is stopped before the inside of the case is sufficiently dried, water freezes in the case and damages the compressor. There was a fear.

[0007] The present invention has been made in view of the above,
The purpose is to ensure that the compressor is in a dry state and to use the compressor to drive the compressor.
An object of the present invention is to provide a compressor control device for a fuel cell system that can minimize the power consumption of a secondary battery.

[0008]

According to the first aspect of the present invention,
In order to solve the above problem, in a compressor control device of a fuel cell system configured to supply air from a compressor having a water injection mechanism to a fuel cell, a discharge discharged from a compressor outlet when the system is stopped. Air temperature detecting means for detecting the air temperature; and determining whether the discharge air temperature has exceeded a predetermined value and / or whether the time rate of change of the discharge air temperature has exceeded a predetermined value. Dry state estimating means for estimating that the inside of the compressor is in a dry state when the condition holds, and control means for controlling to stop the compressor when estimating that the inside of the compressor is in a dry state. The gist is to have

According to a second aspect of the present invention, in order to solve the above-mentioned problems, a pressure valve is provided in an air flow path discharged from the compressor outlet through the fuel cell, and the control means estimates the dry state. If the means determines that the temperature of the discharge air discharged from the compressor outlet is lower than 100 ° C.,
The gist of the present invention is to control the pressure valve so as to restrict the pressure in the compressor.

[0010]

According to the first aspect of the present invention, when the system is stopped, the temperature of the discharge air discharged from the compressor outlet exceeds a predetermined value, and / or the time change rate of the discharge air temperature is reduced. It is determined whether or not a predetermined value has been exceeded.If one or both of the determinations are satisfied, it is estimated that the inside of the compressor has been in a dry state. By controlling to stop the compressor, the compressor can be surely brought into the dry state, and breakage due to freezing of water remaining in the compressor after the system is stopped can be prevented. In addition, the power consumption of the secondary battery used to drive the compressor can be minimized.

According to the present invention, a pressure valve is provided in an air passage discharged from the compressor outlet through the fuel cell, and the temperature of the discharge air discharged from the compressor outlet is reduced. When it is determined that the temperature is lower than 100 ° C., the temperature of the discharge air discharged from the compressor outlet is rapidly increased by controlling the pressure valve to increase the pressure in the compressor. The power consumption of the secondary battery used to drive the compressor can be minimized.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a diagram showing a compressor control device of a fuel cell system according to a first embodiment of the present invention.

First, the configuration of the fuel cell system will be described with reference to FIG.

During operation of the fuel cell system, the filter 3
The air sucked through is compressed by the compressor 5 and supplied to the fuel cell 7. At the inlet of the fuel cell 7, a thermometer 9 for measuring the temperature T1 of the discharge air discharged from the compressor 5 is provided.
Is attached. At the outlet of the fuel cell 7, a pressure valve 11 whose opening can be adjusted to control the discharge air pressure discharged from the compressor 5 is attached. Fuel cell 7
The air that has passed through passes through the pressure valve 11 and is discharged from the reformer 13 to the atmosphere as exhaust gas.

A water injection mechanism is attached to the compressor 5, and water stored in a water tank 15 is sucked by a water pump 17, the injection amount is increased or decreased or stopped by an injector 19, and supplied to the compressor 5. You.

Further, electric power is supplied to the motor 21 for driving the compressor 5 from the secondary battery 25 via the motor control unit 23 during operation after the system is stopped.

The controller 27 receives the discharge air temperature T1 measured by the thermometer 9, and uses a timer provided inside the controller 27 based on the elapsed time after the system stoppage and the discharge air temperature T1. If the discharge air temperature T1 exceeds a predetermined value, or if the time rate of change of the discharge air temperature T1 exceeds a predetermined value, it is assumed that the inside of the compressor 5 is in a dry state, and Is controlled to stop.

Next, the operation of the compressor control device of the fuel cell system shown in FIG. 1 will be described with reference to FIG.

After stopping the fuel cell system, first, the injection of water into the compressor 5 by the injector 19 is stopped. Here, as the operation state of the compressor 5, the discharge pressure, the flow rate, the number of revolutions, and the like are not changed from the state before the system stop. Also, the opening of the pressure valve 11 is not changed. Then, the controller 27 determines the discharge air temperature T1 of the compressor 5
Is continuously monitored by the thermometer 4.

The temperature T1 of the discharge air discharged from the compressor 5
Is in a water-mixed state while the injected water remains in the case of the compressor 5, and is cooled by this water and shows a lower value than the dry state. However, when the water in the case of the compressor 5 dries to a dry state, even if the operation state of the compressor 5 is constant, the discharge air temperature T1 discharged from the compressor 5 by that much when the water in the case starts to dry. Rises.

Here, as shown in FIG. 2, the discharge air temperature T1 measured by the thermometer 9 is higher than the discharge air temperature T10 when the system is stopped by a predetermined value ΔT or more (A), the discharge air temperature T1. The point (A) at which the time change rate dT1 / dt exceeds the predetermined value, it can be estimated that the inside of the case of the compressor 5 is in a dry state.

It should be noted that the criterion (1) is that when the compressor 5 is in a dry state, the discharge air temperature T1 is a value when it is estimated that T1−T10> ΔT, that is, the discharge air temperatures T1 and T
It is sufficient that the difference of 10 is equal to or more than the predetermined value ΔT.

The criterion (2) is that when the compressor 5 is in a dry state, the discharge air temperature T1 is a predetermined value when dT1 / dt> predetermined value, that is, the discharge air temperature T1
It is sufficient that the time change rate dT1 / dt is not less than a predetermined value.

Therefore, as the criterion to be performed by the controller 27, the criterion (1) or the criterion (2) may be used.

The controller 27 stops the control signal output to the motor control unit 23 at the time point tp, and stops the operation of the compressor 5 by the motor 21.

Thus, after the system is stopped, the compressor 5
The operation of the compressor 5 is stopped at the time when it is estimated that the inside of the case has shifted from the water-mixed state to the dry state, so that the power consumption of the secondary battery 25 used for driving the compressor 5 is minimized. And the compressor 5 can be reliably brought into the dry state.

As a criterion, whether the change amount of the discharge air temperature T1 discharged from the compressor 5 or the time change rate of the discharge air temperature T1 is to be used is determined by selecting the one that is easier to detect. In addition, both can be used together to prevent erroneous determination of the discharge air temperature T1.

(Second Embodiment) FIG. 3 is a diagram showing a compressor control device of a fuel cell system according to a second embodiment of the present invention.

The feature of the second embodiment is that, in addition to the structure shown in the first embodiment, the suction air temperature T2 of the compressor 5 is supplied to the air passage from the filter 3 to the suction port of the compressor 5. It comprises a thermometer 31 for measuring and a pressure gauge 33 for measuring a discharge air pressure P2 discharged from the compressor 5.

Next, the operation of the compressor control device of the fuel cell system shown in FIG. 3 will be described with reference to FIG.

In the second embodiment, the temperature T1 of the discharge air discharged from the compressor 5 is measured by the thermometer 9, and the temperature of the compressor 5 is measured.
It is determined whether or not the discharge air temperature T1 discharged from the device exceeds 100 ° C.

First, when the temperature T1 of the discharge air discharged from the compressor 5 is T1> 100 ° C., the compressor 5 is stopped according to the same procedure as in the first embodiment.

On the other hand, when the temperature T1 of the discharge air discharged from the compressor 5 is less than 100 ° C. T1 <100 ° C., the temperature T1 of the discharge air discharged from the compressor 5 becomes T1> 100 ° C. Next, the pressure valve 11 is throttled to change the operation state of the compressor 5.

Here, the operating conditions of the compressor will be described.

The compressor efficiency η representing the operating efficiency of the compressor is:
Generally, the pressure ratio π of the compressor, the discharge air temperature T1 when the compressor is in a dry state, and the suction air temperature T2 of the compressor 5
On the basis of the,

Η = (πΛ0.2857-1) / (T1 / T2-1) (1)

The pressure ratio π is equal to the inlet pressure P of the compressor 5.
When 1 is set to the atmospheric pressure and the outlet air pressure P2 of the compressor 5 is measured by the pressure gauge 9,

Π = P2 / P1 (2)

By transforming the equations (1) and (2) to obtain 1 / 0.2857 ≒ 3.5, the outlet air pressure P2 of the compressor 5 is obtained.

P2 = P1 * π = P1 * {(η * (T1 / T2-1) +1)} 3.5} (3)

As the compressor efficiency η, a characteristic map is obtained in advance based on the flow rate, the pressure ratio π, the number of revolutions, etc. of the compressor, and corresponds to the actually measured values of the flow rate, the pressure ratio π, the number of revolutions, etc. The compressor efficiency η to be obtained may be referred to from this characteristic map.

Accordingly, while the outlet air pressure P2 of the compressor 5 is measured by the pressure gauge 33, the opening of the pressure valve 11 may be throttled so that the outlet air pressure P2 satisfies the expression (3). As a result, the pressure in the compressor 5 increases,
The water in the case tends to become hot. Therefore, as shown in FIG. 4, when the system is stopped, the measured value T1 of the pressure gauge 9 changes relatively quickly from T0 (for example, 60 ° C.) shown at the point (C) to T10 (for example, 80 ° C.) shown at the point (B). Will rise. As a result, the power consumption of the secondary battery used for driving the compressor can be minimized.

This is because, when the discharge air temperature T1 becomes 100 ° C. or more, when the water accumulated in the case of the compressor 5 is scraped out together with the discharge air, the water is vaporized to take a large amount of heat and compress. The discharge air temperature T1 of the machine 5 is greatly reduced. As a result, when there is no more water in the case of the compressor 5 and the compressor 5 enters a dry state, the degree of increase in the discharge air temperature T1 of the compressor 5 increases, and the detection of the dry state can be made easier.

Then, by changing the operation state of the compressor 5,
After the pressure valve 11 is throttled so that the discharge air temperature T1 discharged from the compressor 5 becomes T1> 100 ° C., the compressor 5 is stopped according to the same procedure as in the first embodiment.

Since the operating state of the compressor 5 is changed after the system is stopped, as shown in FIG. 4, the discharge air temperature Td from the compressor 5 changes from the point (C) (for example, 60 ° C.) to (B).
To a point (eg, 80 ° C.).

This transient state is at the point (B) (for example, at 80 ° C.).
Whether the change of the discharge air temperature Td occurs from the stable state as shown in FIG. 4 to the dry state after the point (A) after exceeding 100 ° C. is determined by the water injection amount during the operation of the system or the compression changed after the system is stopped. It depends on the amount of change in the operating state of the machine.

Therefore, the discharge air temperature Td from the compressor 5
The determination criterion (3) is to be introduced assuming that the change is continuously increasing.

This criterion (3) is a value when the discharge air temperature T1 is estimated to be T1> 100 ° C. when the compressor 5 is in a dry state, that is, the discharge air temperatures T1 and T
It is sufficient that the difference of d is equal to or less than the predetermined value ΔT ′.

T1−Td <ΔT ′ Therefore, as a criterion performed by the controller 27, a set of {criterion (1) and criterion (3)} or {criterion (2) and criterion (3)} is set. Judgment may be made in combination.

As described above, after the system is stopped, the controller 27 monitors the discharge air temperature T1 supplied to the fuel cell by the compressor 5, and calculates the temperature rise amount of the discharge air temperature T1.
Alternatively, it is determined that the compressor 5 is in a dry state because the time change rate of the discharge air temperature T1 exceeds a predetermined value, and the compressor 5 is stopped. The inside can be reliably shifted to the dry state, and the power consumption of the secondary battery required to operate the compressor 5 after the system stops can be minimized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a compressor control device of a fuel cell system according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining an operation of the compressor control device of the fuel cell system according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a compressor control device of a fuel cell system according to a second embodiment of the present invention.

FIG. 4 is a diagram for explaining an operation of a compressor control device of a fuel cell system according to a fourth embodiment of the present invention.

[Explanation of symbols]

 3 Filter 5 Compressor 7 Fuel Cell 9, 31 Thermometer 11 Pressure Valve 13 Reformer 21 Motor 27 Controller 33 Pressure Gauge

Claims (2)

[Claims] 1. A compressor control device for a fuel cell system configured to supply air to a fuel cell from a compressor having a water injection mechanism, wherein a temperature of a discharge air discharged from a compressor outlet when the system is stopped. And an air temperature detecting means for detecting whether the discharge air temperature has exceeded a predetermined value and / or whether a time rate of change of the discharge air temperature has exceeded a predetermined value. In this case, dry state estimating means for estimating that the inside of the compressor is in a dry state, and control means for controlling to stop the compressor when estimating that the inside of the compressor is in a dry state are provided. A compressor control device for a fuel cell system, comprising: 2. A compressor according to claim 1, further comprising a pressure valve in an air passage discharged from said compressor outlet through said fuel cell, wherein said control means controls a temperature of a discharge air discharged from said compressor outlet by said dry state estimating means. 2. The compressor control device for a fuel cell system according to claim 1, wherein when it is determined that the pressure is lower than 100 ° C., the pressure valve is controlled to increase the pressure in the compressor.