Purification system

Abstract

To properly purify nitrogen oxide adsorbing to a catalysis.SOLUTION: A purification system S comprises: a clutch 14 that switches between transmission and transmission-interruption of power of an engine 1 to a device 2 to be driven that is driven by the power of the engine 1 and power of a motor 15; a catalyst 31 that when an air-fuel ratio of an air-fuel mixture is equal to or above an ideal air-fuel ratio, adsorbs nitrogen oxide in exhaust gas of the engine 1, and when the air-fuel ratio is less than the ideal air-fuel ratio, promotes reaction of unburnt fuel exhausted from the engine 1 to the adsorbed nitrogen oxide; an obtaining part that obtains adsorption amounts of the nitrogen oxide adsorbing to the catalyst 31; a clutch control part that when the device 2 to be driven is driven by the power of the engine 1 and when the adsorption amounts are equal to or above a predetermined value, brings the clutch 14 into an interruption state to enable the device 2 to be driven only by the power of the motor 15; and an operation control part that when the device 2 to be driven is driven only by the power of the motor 15, sets the air-fuel ratio of the engine 1 being operated to be less than the ideal air-fuel ratio.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a purification system for purifying engine exhaust gas. [Background technology]

[0002] There are known technologies for purifying engine exhaust gas. Patent Document 1 discloses a storage-reduction catalyst that purifies exhaust gas by storing nitrogen oxides in the exhaust gas when the air-fuel ratio is lean, where the proportion of air is higher than the stoichiometric air-fuel ratio, and promoting the reaction between the stored nitrogen oxides and fuel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-200362 Summary of the Invention [Problem to be solved by the invention]

[0004] Because there is a limit to the amount of nitrogen oxides that can be adsorbed by a storage reduction catalyst, when the amount of nitrogen oxides adsorbed by the catalyst exceeds a predetermined value, fuel must be supplied to the catalyst to reduce and remove the nitrogen oxides. When the air-fuel mixture is kept rich, with a higher fuel content than the stoichiometric air-fuel ratio, so that the nitrogen oxides adsorbed by the catalyst can be reduced with fuel, the engine load may fluctuate. When the air-fuel mixture changes from a rich state to a lean state due to load fluctuations, the nitrogen oxides adsorbed by the catalyst may not be sufficiently reduced.

[0005] The present invention has been made in view of these points, and has as its object to appropriately purify nitrogen oxides adsorbed on a catalyst. [Means for solving the problem]

[0006] One aspect of the present invention provides a purification system comprising: a clutch that switches between transmitting and cutting off engine power to a driven device that is driven by engine power and motor power; a catalyst that adsorbs nitrogen oxides in the exhaust of the engine when the air-fuel ratio is equal to or greater than a predetermined air-fuel ratio and promotes a reaction between the adsorbed nitrogen oxides and unburned fuel emitted from the engine when the air-fuel ratio is less than the predetermined air-fuel ratio; an acquisition unit that acquires an adsorption amount of the nitrogen oxides adsorbed to the catalyst; a clutch control unit that controls the clutch to cut off engine power to the driven device when the driven device is driven by engine power and the adsorption amount is equal to or greater than a predetermined value; and an operation control unit that makes the air-fuel ratio of the engine during operation less than the predetermined air-fuel ratio when the adsorption amount is equal to or greater than the predetermined value and the driven device is driven only by the motor power.

[0007] The motor may be provided between the driven device and the clutch, and the clutch may be provided between the engine and the motor.

[0008] The vehicle may include a generator that generates electricity using the output of the engine, and the motor may be driven by the electric power of the generator.

[0009] The driving force of the driven device may be increased by the operation control unit, which may further include an acquisition unit that acquires a driving load of the driven device, and which may be configured to, when the amount of adsorption is equal to or greater than the predetermined value, reduce the ratio of the engine output to the driving load and increase the ratio of the motor output to the driving load in a transmission state in which the clutch transmits the engine power to the driven device.

[0010] The clutch control unit may bring the clutch into a disconnection state in which transmission of power from the engine to the driven device is interrupted when a ratio of the output of the motor to the driving load becomes 1.

[0011] The catalyst may promote a reaction between the unburned fuel and the nitrogen oxides when the temperature is equal to or higher than an activation temperature, and the operation control unit may make the air-fuel ratio less than the predetermined air-fuel ratio when the exhaust temperature of the engine is equal to or higher than the activation temperature after the clutch is disengaged.

[0012] The clutch control unit may, after putting the clutch into the disengaged state, put the clutch into the transmitted state when the amount of adsorption becomes equal to or less than a lower limit value that is smaller than the predetermined value.

[0013] The operation control unit may reduce a ratio of the output of the motor to the driving load after the clutch is in the transmitting state. [Effects of the Invention]

[0014] According to the present invention, it is possible to appropriately purify nitrogen oxides adsorbed on the catalyst. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram for explaining the configuration of a purification system. [Figure 2] FIG. 2 is a diagram for explaining the configuration of a control device. [Figure 3] FIG. 10 is a sequence diagram illustrating a process for reducing the amount of adsorption. DETAILED DESCRIPTION OF THE INVENTION

[0016] [Configuration of Purification System S] FIG. 1 is a diagram illustrating the configuration of a purification system S. The purification system S is a system that purifies the exhaust gas of an engine 1. The purification system S is mounted on, for example, a vehicle or a ship. In this embodiment, the purification system S will be described as being mounted on a vehicle. The purification system S includes a control device 5, an engine 1, a driven device 2, a purification device 3, the control device 5, a generator 13, a clutch 14, and a motor 15.

[0017] The engine 1 is an internal combustion engine that generates power by burning and expanding a mixture of fuel and intake air (air). The engine 1 is, for example, a diesel engine, but it may also be a gasoline engine. In the following explanation, the ratio of air to fuel in the mixture is referred to as the air-fuel ratio, and the air-fuel ratio at which the fuel in the mixture and the oxygen in the air react in just the right amount is referred to as the stoichiometric air-fuel ratio. A state in which the air-fuel ratio is equal to or higher than the stoichiometric air-fuel ratio is referred to as a lean state, and a state in which the air-fuel ratio is less than the stoichiometric air-fuel ratio is referred to as a rich state. A generator 13 and a clutch 14 are provided on the output shaft 11 of the engine 1.

[0018] The generator 13 is provided on the output shaft 11 between the clutch 14 and the engine 1. The generator 13 generates electricity using the output of the engine 1. The generator 13 generates electricity by rotating upon receiving the rotational force of the engine 1. The generator 13 outputs the AC current generated by the power generation to the inverter 4.

[0019] The inverter 4 is a conversion circuit that converts the voltage of an AC current. The inverter 4 converts the voltage value of the AC current output by the generator 13 into a voltage value of an AC current that can drive the motor 15. When the inverter 4 receives the AC current output by the generator 13 as input, it converts it into a voltage that can drive the motor 15 and supplies it to the motor 15.

[0020] The clutch 14 is provided on the output shaft 11 on the opposite side of the generator 13 from the engine 1. When the clutch 14 is in a transmission state, it transmits the power of the engine 1 to the driven device 2. When the clutch 14 is in a disconnection state in which the power of the engine 1 to the driven device 2 is disconnected, the clutch 14 does not transmit the power of the engine 1 to the driven device 2.

[0021] The motor 15 is connected to the clutch 14 on the opposite side of the clutch 14 from the generator 13. Specifically, the motor 15 is connected to the clutch shaft of the clutch 14. The motor 15 operates by receiving a supply of electric power from the generator 13. The motor 15 operates using the electric power from the generator 13 to drive the driven device 2.

[0022] The driven device 2 is, for example, a transmission, but is not limited to this. In addition to the transmission, the driven device 2 may also include a propeller shaft, a differential, a drive shaft, and wheels connected to the transmission.

[0023] The driven device 2 is driven by at least one of the power of the engine 1 and the power of the motor 15. Specifically, when the clutch 14 is in a transmission state, the driven device 2 is driven by the power of the engine 1. When the clutch 14 is in a disengaged state, the driven device 2 is driven by the power of the motor 15. In the following description, the load required to drive the driven device 2 is referred to as the driving load.

[0024] The purification device 3 is provided in an exhaust pipe 12 that discharges exhaust gas from the engine 1 to the outside. The purification device 3 purifies the exhaust gas from the engine 1. Inside the purification device 3, a catalyst 31 for purifying the exhaust gas is provided.

[0025] The catalyst 31 is a storage reduction catalyst capable of adsorbing and reducing nitrogen oxides. When the air-fuel ratio of the mixture is rich, the catalyst 31 adsorbs nitrogen oxides in the exhaust. However, there is a limit to the amount of nitrogen oxides that can be adsorbed by the catalyst 31. When the amount of nitrogen oxides adsorbed by the catalyst 31 reaches an adsorbable amount, the nitrogen oxides can no longer be adsorbed by the catalyst 31. Therefore, it is necessary to purify the nitrogen oxides adsorbed by the catalyst 31 and reduce the amount of nitrogen oxides adsorbed by the catalyst 31 before the amount of nitrogen oxides adsorbed by the catalyst 31 reaches an adsorbable amount.

[0026] Before nitrogen oxides reach an adsorbable amount on the catalyst 31, the control device 5 makes the air-fuel ratio of the mixture of the engine 1 in operation rich, thereby discharging unburned fuel from the engine 1. As a result, unburned fuel is supplied to the catalyst 31.

[0027] The catalyst 31 purifies nitrogen oxides from unburned fuel emitted from the engine 1. Specifically, the catalyst 31 converts nitrogen oxides into nitrogen by promoting a reaction between the unburned fuel and nitrogen oxides adsorbed on the catalyst 31. More specifically, the catalyst 31 promotes the reaction between unburned fuel and nitrogen oxides when the temperature of the catalyst 31 is equal to or higher than its activation temperature. In this way, the catalyst 31 converts the nitrogen oxides adsorbed on the catalyst 31 into nitrogen, thereby reducing the amount of nitrogen oxides adsorbed on the catalyst 31.

[0028] However, when the air-fuel mixture of the operating engine 1 is kept rich, the drive load of the driven device 2 may fluctuate. If the air-fuel mixture of the operating engine 1 is changed from rich to lean in order to accommodate the fluctuation in the drive load, unburned fuel is no longer supplied to the catalyst 31, and the catalyst 31 is therefore unable to sufficiently purify the nitrogen oxides adsorbed thereon.

[0029] Therefore, the control device 5 disengages the clutch 14 to drive the driven device 2 only with the power of the motor 15, thereby making the mixture in the operating engine 1 rich. This allows the control device 5 to continue to make the mixture in the operating engine 1 rich even if the driving load fluctuates. As a result, the purification system S can continue to supply unburned fuel to the catalyst 31, so that the nitrogen oxides adsorbed on the catalyst 31 can be sufficiently purified. The configuration of the control device 5 will be specifically described below.

[0030] [Configuration of control device 5] 2 is a diagram illustrating the configuration of the control device 5. The control device 5 has a storage unit 51 and a control unit 52. The storage unit 51 is a storage medium including a ROM (Read Only Memory), a RAM (Random Access Memory), a hard disk, etc. The storage unit 51 stores a program to be executed by the control unit 52.

[0031] The control unit 52 is a computational resource including a processor such as a CPU (Central Processing Unit). The control unit 52 executes a program stored in the storage unit 51 to realize functions as an acquisition unit 521, a clutch control unit 523, and an operation control unit 522.

[0032] The acquisition unit 521 acquires the amount of adsorption of nitrogen oxides adsorbed on the catalyst 31. For example, the acquisition unit 521 acquires the amount of adsorption based on the amount of exhaust gas emitted from the engine 1. Specifically, the acquisition unit 521 acquires a larger amount of adsorption as the amount of exhaust gas, which is determined by the rotation speed of the engine 1 and the amount of fuel injected into the combustion chamber of the engine 1, increases. More specifically, the acquisition unit 521 acquires the amount of adsorption corresponding to the integrated value of the amount of exhaust gas emitted per unit time. Note that the amount of adsorption corresponding to the integrated value of the amount of exhaust gas is determined in advance by experiments or the like. A data table showing the relationship between the integrated value of the amount of exhaust gas and the amount of adsorption is stored, for example, in the memory unit 51. The acquisition unit 521 acquires the amount of adsorption corresponding to the integrated value of the amount of exhaust gas by referring to the data table stored in the memory unit 51.

[0033] The acquisition unit 521 acquires the driving load of the driven device 2. The driving load is the magnitude of the load required to drive the driven device 2. For example, the acquisition unit 521 acquires load information indicating the driving load of the driven device 2 from a sensor provided in the driven device 2. To give a specific example, the acquisition unit 521 acquires torque as load information indicating the driving load of the driven device 2 from a sensor that detects the torque of the driven device 2.

[0034] When the amount of adsorption exceeds a predetermined value, the operation control unit 522 and the clutch control unit 523 execute a process to reduce the amount of adsorption. The predetermined value is set to a value that prevents nitrogen oxides from being adsorbed by the catalyst 31 to the amount of nitrogen oxides that can be adsorbed by the catalyst 31 before the process to reduce the amount of adsorption is started. The predetermined value is, for example, 80% of the maximum amount of adsorption by the catalyst 31, but is not limited to this.

[0035] FIG. 3 is a sequence diagram for explaining the process of reducing the amount of adsorption. The horizontal axis of FIG. 3 represents time T. Time A is the time when the amount of adsorption reaches a predetermined value. The engine 1 has been operating in a lean state since before time A. The clutch 14 has been in a transmission state since before time A. Since the motor 15 is not driving, the output ratio of the motor 15 to the drive load is 0%. The amount of adsorption continues to increase while the engine 1 is operating in a lean state.

[0036] After time A, the operation control unit 522 reduces the output of the engine 1 while simultaneously increasing the output of the motor 15. In other words, the operation control unit 522 reduces the ratio of the output of the engine 1 to the drive load and increases the ratio of the output of the motor 15 to the drive load. The operation control unit 522 continues to increase the output of the motor 15 to the drive load and continues to decrease the output of the engine 1 until the ratio of the output of the motor 15 to the drive load reaches 100%. The ratio of the output of the motor 15 to the drive load becomes 100% at time B.

[0037] The clutch control unit 523 disengages the clutch 14 from the transmission state at time B when the ratio of the output of the motor 15 to the drive load reaches 100%. Specifically, the clutch control unit 523 disengages the clutch 14 at the timing when the ratio of the output of the motor 15 to the drive load reaches 100%. By disengaging the clutch 14, the clutch control unit 523 puts the driven device 2 into a state where it is driven only by the power of the motor 15.

[0038] The operation control unit 522 drives the generator 13 with the power of the engine 1 at the timing when the clutch 14 is disengaged. In other words, the generator 13 starts generating electricity at the timing when the clutch 14 is disengaged. This allows the operation control unit 522 to convert the output of the operating engine 1 into electric power without wasting it.

[0039] After the clutch 14 is disengaged, the operation control unit 522 changes the output of the motor 15 in accordance with the drive load. When the drive load increases, the operation control unit 522 increases the output of the motor 15, and when the drive load decreases, the operation control unit 522 decreases the output of the motor 15. In this way, the operation control unit 522 can respond to changes in the drive load by changing the output of the motor 15, eliminating the need to change the load on the engine 1.

[0040] Between time A and time B in FIG. 3, the exhaust gas temperature decreases as the output of the engine 1 decreases. If the exhaust gas temperature is below the activation temperature of the catalyst 31, the catalyst 31 cannot promote the reaction between nitrogen oxides and unburned fuel even when supplied with unburned fuel. The operation control unit 522 raises the exhaust gas temperature after time B to raise the catalyst 31 to the activation temperature or higher. Specifically, the operation control unit 522 increases the combustion temperature of the mixture in the combustion chamber by injecting fuel multiple times into the injection unit that injects fuel into the combustion chamber of the engine 1. More specifically, the operation control unit 522 increases the combustion temperature by injecting a small amount of fuel into the injection unit after the main injection. The exhaust gas temperature increases as the combustion temperature increases.

[0041] The exhaust gas temperature reaches or exceeds the activation temperature at time C. When the exhaust gas temperature reaches or exceeds the activation temperature, the temperature of the catalyst 31 also reaches or exceeds the activation temperature. At time C when the exhaust gas temperature reaches or exceeds the activation temperature, the operation control unit 522 reduces the air-fuel ratio of the operating engine 1 to a value less than a predetermined air-fuel ratio. The predetermined air-fuel ratio is the stoichiometric air-fuel ratio, but may be a value smaller than the stoichiometric air-fuel ratio (for example, approximately 90 percent of the stoichiometric air-fuel ratio). The operation control unit 522 reduces the air-fuel ratio of the operating engine 1 to a rich state less than the stoichiometric air-fuel ratio. For example, the operation control unit 522 reduces the amount of intake air supplied to the combustion chamber to reduce the air-fuel ratio. Furthermore, when exhaust gas can be recirculated to the intake pipe of the engine 1, the operation control unit 522 increases the amount of exhaust gas recirculated to the intake pipe to reduce the air-fuel ratio. The operation control unit 522 may also reduce the air-fuel ratio to a rich state by increasing the amount of fuel injected into the combustion chamber of the engine 1. The operation control unit 522 can make the air-fuel ratio rich by using a known method other than the above.

[0042] When the air-fuel ratio becomes rich, unburned fuel is discharged from the engine 1, and the unburned fuel is supplied to the catalyst 31. Upon receiving the unburned fuel, the catalyst 31 promotes a reaction between the adsorbed nitrogen oxides and the unburned fuel. The unburned fuel and nitrogen oxides react on the catalyst 31 to form nitrogen. As a result, the amount of nitrogen oxides adsorbed on the catalyst 31 decreases. The adsorption amount decreases after time C when the air-fuel ratio of the operating engine 1 becomes rich. At time D, the adsorption amount reaches a lower limit value that is smaller than a predetermined value. The lower limit value is, for example, 0, but is not limited to this.

[0043] Clutch control unit 523 puts clutch 14 in the disengaged state into the transmitted state at time D. Clutch control unit 523 puts clutch 14 into the transmitted state, thereby putting driven device 2 into a state where it is driven by the power of engine 1.

[0044] The operation control unit 522 sets the air-fuel ratio of the operating engine 1 to a lean state when the clutch 14 is in the transmission state. Furthermore, when the output of the engine 1 is smaller than the driving load, the operation control unit 522 increases the output of the engine 1 until the output of the engine 1 becomes equal to the driving load, and when the output of the engine 1 is greater than the driving load, the operation control unit 522 decreases the output of the engine 1 until the output of the engine 1 becomes equal to the driving load.

[0045] After the clutch 14 is in the transmission state, the operation control unit 522 reduces the output of the motor 15 to reduce the ratio of the output of the motor 15 to the drive load. Specifically, the operation control unit 522 reduces the output of the motor 15 until the ratio of the output of the motor 15 to the drive load becomes 0%. In other words, the operation control unit 522 reduces the output of the motor 15 to 0. Furthermore, the operation control unit 522 causes the generator 13 to stop generating power at the timing when the clutch 14 is in the transmission state.

[0046] The operation control unit 522 and the clutch control unit 523 execute a process to reduce the amount of adsorption each time the amount of adsorption exceeds a predetermined value while the engine 1 is operating. In this way, if the amount of adsorption exceeds a predetermined value while the vehicle is running using the power of the engine 1, for example, the purification system S can reduce the amount of nitrogen oxides adsorbed on the catalyst 31 while continuing to run the vehicle using the power of the motor 15.

[0047] (Variation) The motor 15 of the purification system S according to the above embodiment receives power from the inverter 4. However, the purification system S may have a battery instead of the inverter 4, and the motor 15 may receive power from the battery that stores power. The battery receives power from the generator 13 and is charged. The battery supplies the charged power to the motor 15. The purification system S according to a modified example can operate the motor 15 by supplying power from the battery to the motor 15 while charging the battery with power from the generator 13. Note that the purification system S may have both the inverter 4 and the battery.

[0048] [Effects of Purification System S] As explained above, when the amount of nitrogen oxides adsorbed on the catalyst 31 provided in the exhaust pipe 12 reaches or exceeds a predetermined value, the purification system S switches the clutch 14 to a disconnected state in which the power of the engine 1 to the driven device 2 is disconnected, thereby causing the driven device 2 to be driven solely by the power of the motor 15. When the driven device 2 is driven solely by the power of the motor 15, the purification system S switches the air-fuel ratio of the operating engine 1 to a rich state that is less than the stoichiometric air-fuel ratio. When the air-fuel ratio of the operating engine 1 becomes rich, unburned fuel is emitted from the engine 1. The catalyst 31 purifies the nitrogen oxides by promoting a reaction between the unburned fuel emitted from the engine 1 and the adsorbed nitrogen oxides.

[0049] While the air-fuel ratio of the operating engine 1 is kept rich, if the drive load of the driven device 2 changes, the purification system S only needs to change the output of the motor 15, and does not need to change the output of the engine 1. Therefore, the purification system S can continue to keep the air-fuel ratio of the operating engine 1 rich. As a result, unburned fuel continues to be supplied from the engine 1 to the catalyst 31, so the catalyst 31 can continue to promote the reaction between the adsorbed nitrogen oxides and the unburned fuel. In this way, the purification system S can appropriately purify the nitrogen oxides adsorbed on the catalyst 31.

[0050] The present invention has been described above using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by functionally or physically distributing or integrating any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combination also have the effects of the original embodiments. [Explanation of symbols]

[0051] S Purification System 1 engine 11 Output shaft 12 exhaust pipe 13. Generator 14 Clutch 15 Motor 2 Driven equipment 3 Purification equipment 31 Catalyst 4 inverters 5. Control device 51 Storage section 52 Control section 521 Acquisition Department 522 Motion control section 523 Clutch control unit

Claims

1. a clutch that switches between transmitting and cutting off the engine power to a driven device that is driven by the engine power and the motor power; a catalyst that adsorbs nitrogen oxides in the exhaust gas of the engine when the air-fuel ratio is equal to or greater than a predetermined air-fuel ratio, and that promotes a reaction between unburned fuel discharged from the engine and the adsorbed nitrogen oxides when the air-fuel ratio is less than the predetermined air-fuel ratio; an acquisition unit that acquires the amount of nitrogen oxides adsorbed on the catalyst; a clutch control unit that controls the clutch to cut off the power of the engine to the driven device when the driven device is driven by the power of the engine and the amount of adsorption is equal to or greater than a predetermined value; an operation control unit that, when the amount of adsorption is equal to or greater than the predetermined value and the driven device is driven only by power of the motor, makes the air-fuel ratio of the engine during operation less than the predetermined air-fuel ratio; A purification system having:

2. the motor is provided between the driven device and the clutch, The clutch is provided between the engine and the motor. The purification system of claim 1 .

3. a generator that generates electricity using the output of the engine, The motor is driven by the electric power of the generator. The purification system according to claim 1 or 2.

4. an acquisition unit that acquires a drive load of the driven device; when the amount of adsorption is equal to or greater than the predetermined value, the operation control unit reduces a ratio of the output of the engine to the driving load and increases a ratio of the output of the motor to the driving load in a transmission state in which the clutch transmits power of the engine to the driven device; The purification system of claim 1 .

5. the clutch control unit, when a ratio of the output of the motor to the driving load becomes 1, brings the clutch into a disconnected state in which transmission of power from the engine to the driven device is interrupted; The purification system of claim 4.

6. the catalyst promotes the reaction between the unburned fuel and the nitrogen oxides when the catalyst is at or above its activation temperature; the operation control unit makes the air-fuel ratio less than the predetermined air-fuel ratio when the exhaust temperature of the engine is equal to or higher than the activation temperature after the clutch is in the disengaged state. The purification system of claim 5 .

7. the clutch control unit, after putting the clutch into the disengaged state, puts the clutch into the transmitted state when the amount of adsorption becomes equal to or less than a lower limit value that is smaller than the predetermined value; The purification system according to claim 5 or 6.

8. the operation control unit reduces a ratio of the output of the motor to the driving load after the clutch is in the transmitting state; The purification system of claim 7.

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