Exhaust emission control device and control device

Abstract

To provide an exhaust emission control device and a control device capable of inhibiting an occupant from being aware of noise of a reactor while suppressing deterioration of exhaust emission control performance.SOLUTION: An exhaust emission control device is used for an internal combustion engine of a vehicle. The exhaust emission control device includes a power source, a reactor and a control device. The reactor generates plasma by receiving supply of voltage from the power source and purifies exhaust gas of the internal combustion engine. The control device changes frequency of the voltage to be supplied by the power source on the basis of vehicle speed, speed of the internal combustion engine or an opening of a throttle valve of the vehicle.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an exhaust gas purification device and a control device. [Background technology]

[0002] Known examples of inventions relating to conventional exhaust gas purification devices include the exhaust gas purification device described in Patent Document 1 and the exhaust gas purification device described in Patent Document 2. The exhaust gas purification device described in Patent Document 1 and the exhaust gas purification device described in Patent Document 2 purify exhaust gas by using plasma. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-195960 A [Patent Document 2] JP 2002-266626 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, to generate plasma, an AC voltage is applied to a number of electrodes, which causes vibrations in the electrodes and produces sound.

[0005] Therefore, an object of the present invention is to provide an exhaust purification device and a control device that can suppress a decrease in exhaust purification performance while suppressing passengers from being aware of the reactor noise. [Means for solving the problem]

[0006] The first aspect is An exhaust gas purification device for use in an internal combustion engine of a vehicle, The exhaust purification device includes a power source, a reactor, and a control device, the reactor generates plasma by receiving a voltage from the power source to purify exhaust gas from the internal combustion engine; the control device changes a frequency of the voltage supplied by the power source based on a speed of the vehicle, a rotation speed of the internal combustion engine, or an opening degree of a throttle valve of the vehicle. It is an exhaust purification device.

[0007] The second aspect is, The second frequency is higher than the first frequency, the control device sets the frequency of the voltage supplied by the power source to a first frequency when the speed of the vehicle is faster than a first speed, and sets the frequency of the voltage supplied by the power source to the second frequency when the speed of the vehicle is slower than the first speed. The exhaust purification device according to the first aspect.

[0008] The third aspect is, The second speed is slower than the first speed, When the differential value of the opening degree of the throttle valve of the vehicle is smaller than a predetermined value, the control device sets the frequency of the voltage supplied by the power source to a first frequency when the speed of the vehicle is faster than the first speed, and sets the frequency of the voltage supplied by the power source to the second frequency when the speed of the vehicle is slower than the first speed; When the differential value of the opening degree of the throttle valve of the vehicle is greater than the predetermined value, the control device sets the frequency of the voltage supplied by the power source to a first frequency if the speed of the vehicle is faster than the second speed, and sets the frequency of the voltage supplied by the power source to the second frequency if the speed of the vehicle is slower than the second speed. The exhaust purification device according to the second aspect.

[0009] The fourth aspect is A control device for an exhaust gas purification device used in an internal combustion engine of a vehicle, The exhaust purification device includes a power source and a reactor, the reactor generates plasma by receiving a voltage from the power source to purify exhaust gas from the internal combustion engine; the control device changes a frequency of the voltage supplied by the power source based on a speed of the vehicle, a rotation speed of the internal combustion engine, or an opening degree of a throttle valve of the vehicle. It is a control device. Effect of the Invention

[0010] According to the present invention, it is possible to suppress a decrease in exhaust purification performance while suppressing passengers from being aware of the reactor noise. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of a vehicle 10. [Diagram 2] FIG. 2 is a graph showing the relationship between the speed V of the vehicle 10 and time, and a graph showing the relationship between the frequency of the AC voltage and time. [Diagram 3] FIG. 3 is a graph showing the relationship between the value of the current flowing between adjacent electrodes and time. [Figure 4] FIG. 4 is a flowchart executed by the control device 12. [Diagram 5] FIG. 5 is a graph showing the relationship between the speed V of the vehicle 10 and time, a graph showing the relationship between the opening φ of the throttle valve 23 and time, a graph showing the relationship between the derivative of the opening φ of the throttle valve 23 and time, and a graph showing the relationship between the frequency of the AC voltage and time. [Figure 6] FIG. 6 is a flowchart executed by the control device 12. [Figure 7] FIG. 7 is a flowchart executed by the control device 12. [Figure 8] FIG. 8 is a flowchart executed by the control device 12. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] (Embodiment) [Vehicle structure] The structure of a vehicle 10 equipped with an exhaust gas purification device 11 according to an embodiment of the present invention will be described below with reference to the drawings.

[0013] The vehicle 10 runs on power generated by an internal combustion engine 20. The vehicle 10 is, for example, a four-wheeled automobile. As shown in Fig. 1, the vehicle 10 includes an exhaust purification device 11, an internal combustion engine 20, a speed sensor 22, a throttle valve 23, a throttle position sensor 24, and a crank angle sensor 26.

[0014] The internal combustion engine 20 is used as a power source for an automobile. The internal combustion engine 20 is, for example, a four-stroke engine that uses gasoline as fuel. Note that the structure of the internal combustion engine 20 is a general structure, and therefore a description thereof will be omitted.

[0015] An intake path R1 and an exhaust path R2 are connected to the internal combustion engine 20. The intake path R1 is a path through which air passes. The exhaust path R2 is a path through which exhaust gas passes.

[0016] The throttle valve 23 is provided in the intake path R1. The throttle valve 23 opens and closes the intake path R1 in response to the driver's operation of the accelerator pedal, thereby adjusting the amount of air supplied to the internal combustion engine 20.

[0017] The throttle position sensor 24 detects the opening degree φ of the throttle valve 23. The opening degree φ is indicated, for example, by the rotation angle of the throttle valve 23 from a fully closed state. As the rotation angle increases, the opening degree φ increases. In this embodiment, the throttle position sensor 24 outputs a signal indicating the rotation angle of the throttle valve 23 from a fully closed state to the control device 12.

[0018] The speed sensor 22 detects the speed V of the vehicle 10. The speed sensor 22 outputs, for example, a signal indicating the rotation speed of the wheels to the control device 12. The control device 12 can obtain the speed V from the rotation speed of the wheels.

[0019] The crank angle sensor 26 detects the rotation speed VR of the internal combustion engine 20. The rotation speed VR is the number of rotations per unit time of the crankshaft of the internal combustion engine 20. The crank angle sensor 26 outputs, for example, a signal indicating the rotation angle of the crankshaft of the internal combustion engine 20 to the control device 12. The control device 12 can obtain the rotation speed VR based on the signal from the crank angle sensor 26.

[0020] The exhaust purification device 11 is used in an internal combustion engine 20 of a vehicle 10. The exhaust purification device 11 reduces the particulate number (PN) by removing particulate matter (PM) from exhaust gas. As shown in Fig. 1, the exhaust purification device 11 includes a control device 12, a battery 14, a power source 16, and a reactor 18.

[0021] The battery 14 generates a DC voltage of 12V. The battery 14 is, for example, a lead-acid battery. The power source 16 converts the DC voltage of the battery 14 into an AC voltage. At this time, the power source 16 boosts the AC voltage up to 4 kV. The power source 16 can also generate an AC voltage having a first frequency f1 and an AC voltage having a second frequency f2. The second frequency f2 is higher than the first frequency f1. The first frequency f1 is, for example, 1 kHz. The second frequency f2 is, for example, 20 kHz.

[0022] The reactor 18 is provided in the exhaust path R2. The reactor 18 generates plasma by receiving a voltage from the power source 16, and purifies the exhaust gas of the internal combustion engine 20. The reactor 18 includes a plurality of electrodes. The plurality of electrodes are stacked while being insulated from each other. An AC voltage generated by the power source 16 is applied to the plurality of electrodes. This causes a discharge to occur between two adjacent electrodes. As a result, plasma is generated between the two adjacent electrodes. The plasma decomposes PM.

[0023] The control device 12 is an ECU (Electric Control Unit). The control device 12 is a combination of a circuit board, a semiconductor device, and electronic components. The control device 12 changes the frequency of the voltage supplied by the power source 16 based on the speed V of the vehicle 10.

[0024] [Operation of exhaust purification device] Next, the operation of the exhaust purification device 11 will be described. FIG. 2 is a graph showing the relationship between the speed V of the vehicle 10 and time, and a graph showing the relationship between the frequency of the AC voltage and time. The horizontal axis indicates time. In the upper graph, the vertical axis indicates the speed V. In the lower graph, the vertical axis indicates the frequency. FIG. 3 is a graph showing the relationship between the value of the current flowing between adjacent electrodes and time. The upper graph in FIG. 3 is a graph when an AC voltage of a first frequency f1 is applied to multiple electrodes. The lower graph in FIG. 3 is a graph when an AC voltage of a second frequency f2 is applied to multiple electrodes. The horizontal axis indicates time. The vertical axis indicates the current value.

[0025] 2, the vehicle 10 accelerates, then travels at a constant speed, and then decelerates. Before time t1, the speed V is slower than the first speed V1. Between times t1 and t2, the speed V is equal to or greater than the first speed V1. After time t2, the speed V is slower than the first speed V1.

[0026] Therefore, when the speed V of the vehicle 10 is equal to or greater than the first speed V1, the control device 12 sets the frequency of the voltage supplied by the power source 16 to the first frequency f1, and when the speed V of the vehicle 10 is slower than the first speed V1, the control device 12 sets the frequency of the voltage supplied by the power source 16 to the second frequency f2. As a result, as shown in the graph in the lower part of FIG. 2, before time t1, the reactor 18 operates with an AC voltage of the second frequency f2. From time t1 to t2, the reactor 18 operates with an AC voltage of the first frequency f1. After time t2, the reactor 18 operates with an AC voltage of the second frequency f2.

[0027] Here, as shown in the upper graph of FIG. 3, when the reactor 18 operates with an AC voltage of a first frequency f1 (for example, 1 kHz), a pulse wave is generated 1000 times per second. The pulse wave has a large current value. Therefore, the intensity of the plasma generated by the reactor 18 is high. In other words, the PN removal performance by the reactor 18 is high. The PN removal performance when the reactor 18 is driven at the first frequency f1 is higher than the PN removal performance when the reactor 18 is driven at the second frequency f2. However, since the multiple electrodes vibrate significantly, the reactor 18 generates a loud noise.

[0028] On the other hand, as shown in the lower graph of FIG. 3, when the reactor 18 operates with an AC voltage of the second frequency f2 (for example, 20 kHz), a pulse wave is generated 20,000 times per second. The pulse wave has a small current value. Therefore, the intensity of the plasma generated by the reactor 18 is small. In other words, the PN removal performance of the reactor 18 is low. However, since the multiple electrodes do not vibrate significantly, the reactor 18 does not generate a large sound. Therefore, the sound generated by the reactor 18 when the reactor 18 is driven at the second frequency f2 is smaller than the sound generated by the reactor 18 when the reactor 18 is driven at the first frequency f1.

[0029] [Operation of control device 12] Next, the operation of the control device 12 for causing the exhaust purification device 11 to perform the above-mentioned operation will be described with reference to the drawings. Fig. 4 is a flowchart executed by the control device 12. The control device 12 executes the above-mentioned flowchart by reading out a program stored in a storage device (not shown).

[0030] This process begins with the start of operation of the internal combustion engine 20. The speed sensor 22 outputs a signal indicating the rotation speed of the wheels to the control device 12. In response to this, the control device 12 obtains the speed V of the vehicle 10 (step S1).

[0031] The control device 12 determines whether the speed V is equal to or greater than the first speed V1 (step S2). If the speed V is equal to or greater than the first speed V1, the process proceeds to step S3. If the speed V is slower than the first speed V1, the process proceeds to step S4.

[0032] If the speed V is equal to or greater than the first speed V1, the control device 12 sets the frequency of the voltage supplied by the power source 16 to the first frequency f1 (step S3). As a result, the reactor 18 operates on the AC voltage of the first frequency f1. Therefore, the reactor 18 exhibits high PN removal performance. However, the reactor 18 generates a large sound. After this, the process proceeds to step S5.

[0033] If the speed V is slower than the first speed V1, the control device 12 sets the frequency of the voltage supplied by the power source 16 to the second frequency f2 (step S4). As a result, the reactor 18 operates with an AC voltage of the second frequency f2. Therefore, the reactor 18 exhibits low PN removal performance. However, the reactor 18 does not generate a large sound. After this, the process proceeds to step S5.

[0034] In step S5, the control device 12 determines whether or not the operation of the internal combustion engine 20 has stopped, thereby determining whether or not to end this process (step S5). If the operation of the internal combustion engine 20 has not stopped, this process returns to step S1. If the operation of the internal combustion engine 20 has stopped, this process ends.

[0035] [effect] According to the exhaust purification device 11, it is possible to suppress the passengers from being aware of the sound of the reactor while suppressing the deterioration of the exhaust purification performance. More specifically, when the speed V of the vehicle 10 is equal to or higher than the first speed V1, the wind noise (900 Hz to 10 kHz), road noise (100 Hz to 1 kHz), and noises due to the engine, motor, etc. are large. Therefore, even if the reactor 18 generates a large sound, the passengers of the vehicle 10 are unlikely to be aware of the sound of the reactor 18 due to these noises. On the other hand, when the speed V of the vehicle 10 is slower than the first speed V1, the wind noise (900 Hz to 10 kHz), road noise (100 Hz to 1 kHz), and noises due to the engine, motor, etc. are small. Therefore, when the reactor 18 generates a large sound, the passengers of the vehicle 10 are likely to be aware of the sound of the reactor 18.

[0036] Therefore, the control device 12 changes the frequency of the voltage supplied by the power source 16 based on the speed V of the vehicle 10. More specifically, when the speed V of the vehicle 10 is faster than a first speed V1, the control device 12 sets the frequency of the voltage supplied by the power source 16 to a first frequency f1. This allows the reactor 18 to exhibit high exhaust purification performance (PN removal performance). Furthermore, passengers are less likely to be aware of the sound produced by the reactor 18 due to wind noise (900 Hz to 10 kHz), road noise (100 Hz to 1 kHz), and noise from the engine, motor, etc.

[0037] On the other hand, when the speed V of the vehicle 10 is slower than the first speed V1, the control device 12 sets the frequency of the voltage supplied by the power source 16 to the second frequency f2. This allows the reactor 18 to exert low exhaust purification performance (PN removal performance) without generating a loud noise. In other words, the occupants are less likely to be aware of the sound produced by the reactor 18. Through the above operation, the exhaust purification device 11 can prevent the occupants from being aware of the reactor sound while suppressing a decrease in the exhaust purification performance.

[0038] (First Modification) The exhaust gas purification device 11a according to the first modification will be described below with reference to the drawings. FIG. 1 is used for a schematic diagram of the vehicle 10 according to the first modification. FIG. 5 is a graph showing the relationship between the speed V of the vehicle 10 and time, a graph showing the relationship between the opening degree φ of the throttle valve 23 and time, a graph showing the relationship between the differential value of the opening degree φ of the throttle valve 23 and time, and a graph showing the relationship between the frequency of the AC voltage and time. The horizontal axis indicates time. In the first graph, the vertical axis indicates the speed V. In the second graph, the vertical axis indicates the opening degree φ. In the third graph, the vertical axis indicates the differential value of the opening degree φ. The differential value of the opening degree φ means the amount of change in the opening degree φ. Therefore, when the differential value of the opening degree φ is large, the throttle valve 23 suddenly opens the intake path R1. In the fourth graph, the vertical axis indicates the frequency.

[0039] In the exhaust purification device 11, the control device 12 judges whether the speed V is equal to or greater than the first speed V1. On the other hand, in the exhaust purification device 11a, when the differential value of the opening degree φ is equal to or greater than the predetermined value φT, the control device 12 judges whether the speed V is equal to or greater than the first speed V1. Also, when the differential value of the opening degree φ is smaller than the predetermined value φT, the control device 12 judges whether the speed V is equal to or greater than the second speed V2. The control device 12 judges whether the throttle valve 23 has suddenly opened the intake path R1 by judging whether the differential value of the opening degree φ is equal to or greater than the predetermined value φT. The second speed V2 is slower than the first speed V1. This will be explained below.

[0040] 5, the derivative of the opening angle φ of the throttle valve 23 of the vehicle 10 is smaller than the predetermined value φT, and the speed V of the vehicle 10 is slower than the first speed V1. Therefore, the control device 12 sets the frequency of the voltage supplied by the power source 16 to the second frequency f2.

[0041] 5, the derivative of the opening degree φ of the throttle valve 23 of the vehicle 10 is equal to or greater than the predetermined value φT, and the speed V of the vehicle 10 is slower than the second speed V2. Therefore, the control device 12 sets the frequency of the voltage supplied by the power source 16 to the second frequency f2.

[0042] 5, the derivative of the opening degree φ of the throttle valve 23 of the vehicle 10 is equal to or greater than a predetermined value φT, and the speed V of the vehicle 10 is equal to or greater than a second speed V2. Therefore, the control device 12 sets the frequency of the voltage supplied by the power source 16 to a first frequency f1.

[0043] 5, the derivative of the opening angle φ of the throttle valve 23 of the vehicle 10 is smaller than the predetermined value φT, and the speed V of the vehicle 10 is equal to or greater than the first speed V1. Therefore, the control device 12 sets the frequency of the voltage supplied by the power source 16 to the first frequency f1.

[0044] Next, the operation of the control device 12 for causing the exhaust purification device 11a to perform the above-mentioned operation will be described with reference to the drawings. Fig. 6 is a flowchart executed by the control device 12. The control device 12 executes the above-mentioned flowchart by reading out a program stored in a storage device (not shown).

[0045] This process begins when the internal combustion engine 20 starts operating. The speed sensor 22 outputs a signal indicating the rotation speed of the wheels to the control device 12. In addition, the throttle position sensor 24 outputs a signal indicating the rotation angle of the throttle valve 23 from a fully closed state to the control device 12. In response to this, the control device 12 obtains the speed V of the vehicle 10 (step S1). In addition, the control device 12 obtains the opening angle φ of the throttle valve 23 (step S11).

[0046] Next, the control device 12 differentiates the opening degree φ with respect to time (step S12). Then, the control device 12 determines whether or not the differentiated value of the opening degree φ is equal to or greater than a predetermined value φT (step S13). If the differentiated value of the opening degree φ is equal to or greater than the predetermined value φT, the process proceeds to step S14. If the differentiated value of the opening degree φ is smaller than the predetermined value φT, the process proceeds to step S2. Note that steps S2 to S5 in FIG. 6 are the same as steps S2 to S5 in FIG. 4, and therefore will not be described.

[0047] If the differential value of the opening φ is equal to or greater than the predetermined value φT, the control device 12 determines whether the speed V is equal to or greater than the second speed V2 (step S14). If the speed V is equal to or greater than the second speed V2, the process proceeds to step S15. If the speed V is slower than the second speed V2, the process proceeds to step S16.

[0048] If the speed V is equal to or greater than the second speed V2, the control device 12 sets the frequency of the voltage supplied by the power source 16 to the first frequency f1 (step S15). As a result, the reactor 18 operates on the AC voltage of the first frequency f1. Therefore, the reactor 18 exhibits high PN removal performance. However, the reactor 18 generates a large sound. After this, the process proceeds to step S5.

[0049] If the speed V is slower than the second speed V2, the control device 12 sets the frequency of the voltage supplied by the power source 16 to the second frequency f2 (step S16). As a result, the reactor 18 operates with an AC voltage of the second frequency f2. Therefore, the reactor 18 exhibits low PN removal performance. However, the reactor 18 does not generate a large sound. After this, the process proceeds to step S5.

[0050] For the same reasons as those of the exhaust purification device 11, the exhaust purification device 11a can suppress a decrease in exhaust purification performance while suppressing passengers from being aware of the reactor noise.

[0051] According to the exhaust purification device 11a, the performance of exhaust purification is improved. More specifically, when the differential value of the opening degree φ of the throttle valve 23 of the vehicle 10 is larger than a predetermined value φT, the rotation speed of the internal combustion engine 20 becomes higher. Therefore, the sound generated by the internal combustion engine 20 becomes louder, so that the passengers are less aware of the sound generated by the reactor 18. Therefore, when the differential value of the opening degree φ of the throttle valve 23 of the vehicle 10 is larger than the predetermined value φT, the control device 12 determines whether the speed V of the vehicle 10 is equal to or higher than a second speed V2 that is slower than the first speed V1. Therefore, the speed V when the control device 12 operates the reactor 18 by the AC voltage of the first frequency f1 in the exhaust purification device 11a is slower than the speed V when the control device 12 operates the reactor 18 by the AC voltage of the first frequency f1 in the exhaust purification device 11. As a result, the period during which the reactor 18 operates by the AC voltage of the first frequency f1 becomes longer. Therefore, the exhaust gas purification device 11a improves the exhaust gas purification performance.

[0052] (Second Modification) An exhaust gas purification device 11b according to the second modified example will be described below with reference to the drawings. FIG. 1 is used as a schematic diagram of a vehicle 10 according to the second modified example.

[0053] The exhaust purification device 11b differs from the exhaust purification device 11 in that the control device 12 changes the frequency of the voltage supplied by the power source 16 based on the opening degree φ of the throttle valve 23 of the vehicle 10. The difference will be described below with reference to the drawings. Figure 7 is a flowchart executed by the control device 12. The control device 12 executes the above flowchart by reading out a program stored in a storage device (not shown).

[0054] This process begins when the internal combustion engine 20 starts operating. The throttle position sensor 24 outputs a signal indicating the rotation angle of the throttle valve 23 from the fully closed state to the control device 12. As a result, the control device 12 obtains the opening degree φ of the throttle valve 23 (step S21).

[0055] Next, the control device 12 differentiates the opening degree φ with respect to time (step S22). Then, the control device 12 determines whether or not the differential value of the opening degree φ is equal to or greater than the first differential value φ1 (step S23). If the differential value of the opening degree φ is equal to or greater than the first differential value φ1, the process proceeds to step S24. If the differential value of the opening degree φ is smaller than the first differential value φ1, the process proceeds to step S25.

[0056] When the differential value of the opening φ is equal to or greater than the first differential value φ1, the control device 12 sets the frequency of the voltage supplied by the power source 16 to the first frequency f1 (step S24). As a result, the reactor 18 operates on the AC voltage of the first frequency f1. Therefore, the reactor 18 exhibits high PN removal performance. However, the reactor 18 generates a large sound. After this, the process proceeds to step S26.

[0057] If the differential value of the opening φ is smaller than the first differential value φ1, the control device 12 sets the frequency of the voltage supplied by the power source 16 to the second frequency f2 (step S25). As a result, the reactor 18 operates with an AC voltage of the second frequency f2. Therefore, the reactor 18 exhibits low PN removal performance. However, the reactor 25 does not generate a large sound. After this, the process proceeds to step S26.

[0058] In step S26, the control device 12 determines whether or not the operation of the internal combustion engine 20 has stopped, thereby determining whether or not to end this process (step S26). If the operation of the internal combustion engine 20 has not stopped, this process returns to step S21. If the operation of the internal combustion engine 20 has stopped, this process ends.

[0059] According to the exhaust purification device 11b, it is possible to suppress the passengers from being aware of the sound of the reactor while suppressing the deterioration of the exhaust purification performance. More specifically, when the derivative value of the opening degree φ is equal to or greater than the first derivative value φ1, the rotation speed of the internal combustion engine 20 increases. Therefore, the sound generated by the internal combustion engine 20 becomes louder, and the passengers are less likely to be aware of the sound generated by the reactor 18. On the other hand, when the derivative value of the opening degree φ is smaller than the first derivative value φ1, the rotation speed of the internal combustion engine 20 decreases. Therefore, the sound generated by the internal combustion engine 20 becomes quieter, and the passengers are more likely to be aware of the sound generated by the reactor 18.

[0060] Therefore, the control device 12 changes the frequency of the voltage supplied by the power source 16 based on the opening degree φ of the throttle valve 23. More specifically, when the derivative value of the opening degree φ is equal to or greater than the first derivative value φ1, the control device 12 sets the frequency of the voltage supplied by the power source 16 to the first frequency f1. This allows the reactor 18 to exhibit high exhaust purification performance (PN removal performance). Furthermore, the sound generated by the internal combustion engine 20 makes it difficult for the occupants to be aware of the sound produced by the reactor 18.

[0061] On the other hand, when the derivative value of the opening degree φ is smaller than the first derivative value φ1, the control device 12 sets the frequency of the voltage supplied by the power source 16 to the second frequency f2. This allows the reactor 18 to exhibit low exhaust purification performance (PN removal performance) without generating a loud noise. In other words, the passengers are less likely to be aware of the sound made by the reactor. Through the above operation, the exhaust purification device 11b can prevent the passengers from being aware of the sound made by the reactor while suppressing the reduction in exhaust purification performance.

[0062] (Third Modification) An exhaust gas purification device 11c according to a third modified example will be described below with reference to the drawings. FIG. 1 is used as a schematic diagram of a vehicle 10 according to the third modified example.

[0063] The exhaust purification device 11c differs from the exhaust purification device 11 in that the control device 12 changes the frequency of the voltage supplied by the power source 16 based on the rotation speed VR of the internal combustion engine 20. The difference will be described below with reference to the drawings. Figure 8 is a flowchart executed by the control device 12. The control device 12 executes the above flowchart by reading out a program stored in a storage device (not shown).

[0064] This process begins when the internal combustion engine 20 starts operating. The crank angle sensor 26 outputs a signal indicating the rotation angle of the crankshaft of the internal combustion engine 20 to the control device 12. As a result, the control device 12 obtains the rotation speed VR of the internal combustion engine 20 (step S31).

[0065] Next, the control device 12 determines whether the rotation speed VR is equal to or greater than the first rotation speed VR1 (step S32). If the rotation speed VR is equal to or greater than the first rotation speed VR1, the process proceeds to step S33. If the rotation speed VR is slower than the first rotation speed VR1, the process proceeds to step S34.

[0066] When the rotation speed VR is equal to or higher than the first rotation speed VR1, the control device 12 sets the frequency of the voltage supplied by the power source 16 to the first frequency f1 (step S33). As a result, the reactor 18 operates on the AC voltage of the first frequency f1. Therefore, the reactor 18 exhibits high PN removal performance. However, the reactor 18 generates a large sound. After this, the process proceeds to step S35.

[0067] When the rotation speed VR is slower than the first rotation speed VR1, the control device 12 sets the frequency of the voltage supplied by the power source 16 to the second frequency f2 (step S34). As a result, the reactor 18 operates with the AC voltage of the second frequency f2. Therefore, the reactor 18 exhibits low PN removal performance. However, the reactor 25 does not generate a large sound. After this, the process proceeds to step S35.

[0068] In step S35, the control device 12 determines whether or not the operation of the internal combustion engine 20 has stopped, thereby determining whether or not to end this process (step S35). If the operation of the internal combustion engine 20 has not stopped, this process returns to step S31. If the operation of the internal combustion engine 20 has stopped, this process ends.

[0069] According to the exhaust purification device 11c, it is possible to suppress a decrease in exhaust purification performance while suppressing occupants from being aware of the sound of the reactor. More specifically, when the rotation speed VR is equal to or higher than the first rotation speed VR1, the sound generated by the internal combustion engine 20 becomes louder. Therefore, the occupants are less likely to be aware of the sound generated by the reactor 18. On the other hand, when the rotation speed VR is slower than the first rotation speed VR1, the sound generated by the internal combustion engine 20 becomes quieter. Therefore, the occupants are more likely to be aware of the sound generated by the reactor 18.

[0070] Therefore, the control device 12 changes the frequency of the voltage supplied by the power source 16 based on the opening degree φ of the throttle valve 23. More specifically, when the derivative value of the opening degree φ is equal to or greater than the first derivative value φ1, the control device 12 sets the frequency of the voltage supplied by the power source 16 to the first frequency f1. This allows the reactor 18 to exhibit high exhaust purification performance (PN removal performance). Furthermore, the sound generated by the internal combustion engine 20 makes it difficult for the occupants to be aware of the sound produced by the reactor 18.

[0071] On the other hand, when the derivative value of the opening φ is not equal to or greater than the first derivative value φ1, the control device 12 sets the frequency of the voltage supplied by the power source 16 to the second frequency f2. This allows the reactor 18 to exert low exhaust purification performance (PN removal performance) without generating a loud noise. In other words, the passengers are less likely to be aware of the sound made by the reactor. Through the above operation, the exhaust purification device 11b can suppress the deterioration of the exhaust purification performance while suppressing the passengers from being aware of the sound made by the reactor.

[0072] (Other embodiments) The exhaust purification device and control device according to the present invention are not limited to the exhaust purification devices 11, 11a to 11c and the control device 12, and may be modified within the scope of the invention. Furthermore, the structures and operations of the exhaust purification devices 11, 11a to 11c may be combined in any manner.

[0073] In addition, when the speed V of the vehicle 10 is a first speed V1, the control device 12 may set the frequency of the voltage supplied by the power source 16 to a first frequency f1, or may set the frequency of the voltage supplied by the power source 16 to a second frequency f2.

[0074] In addition, when the speed V of the vehicle 10 is a second speed V2, the control device 12 may set the frequency of the voltage supplied by the power source 16 to a first frequency f1, or may set the frequency of the voltage supplied by the power source 16 to a second frequency f2.

[0075] When the differential value of the opening degree φ of the throttle valve 23 of the vehicle 10 is a predetermined value φT, the control device 12 may set the frequency of the voltage supplied by the power source 16 to a first frequency f1 if the speed V of the vehicle 10 is equal to or greater than a first speed V1, and may set the frequency of the voltage supplied by the power source 16 to a second frequency f2 if the speed V of the vehicle 10 is slower than the first speed V1. Also, when the differential value of the opening degree φ of the throttle valve 23 of the vehicle 10 is a predetermined value φT, the control device 12 may set the frequency of the voltage supplied by the power source 16 to the first frequency f1 if the speed V of the vehicle 10 is equal to or greater than a second speed V2, and may set the frequency of the voltage supplied by the power source 16 to the second frequency f2 if the speed V of the vehicle 10 is slower than the second speed V2.

[0076] In the exhaust purification device 11c, like the exhaust purification device 11a, the control device 12 may determine whether or not the derivative value of the opening degree φ is equal to or greater than a predetermined value φT. If the derivative value of the opening degree φ is equal to or greater than the predetermined value φT, the control device 12 determines whether or not the rotation speed VR of the internal combustion engine 20 is equal to or greater than a second rotation speed VR2. If the derivative value of the opening degree φ is not equal to or greater than the predetermined value φT, the control device 12 determines whether or not the rotation speed VR of the internal combustion engine 20 is equal to or greater than a first rotation speed VR1. The second rotation speed VR2 is slower than the first rotation speed VR1.

[0077] In the exhaust purification device 11, the speed V may repeatedly increase and decrease in a short period of time. In such a case, the speed V repeatedly becomes larger than the first speed V1 and then becomes smaller than the first speed V1 in a short period of time. In this case, the control device 12 frequently switches the frequency of the voltage supplied by the power source 16 between the first frequency f1 and the second frequency f2.

[0078] Therefore, when the speed V becomes smaller than the first speed V1 immediately after the speed V becomes larger than the first speed V1, the control device 12 does not switch the frequency of the voltage supplied by the power source 16 from the first frequency f1 to the second frequency f2. Specifically, when the speed V becomes smaller than the third speed V3 within a predetermined time after the speed V becomes larger than the first speed V1, the control device 12 switches the frequency of the voltage supplied by the power source 16 from the first frequency f1 to the second frequency f2. The third speed V3 is slower than the first speed V1. The predetermined time is, for example, one second. [Explanation of symbols]

[0079] 10: Vehicle 11, 11a to 11c: Exhaust purification device 12: Control device 14: Battery 16: Power supply 18: Reactor 20: Internal combustion engine 22: Speed ​​sensor 23:Throttle valve 24: Throttle position sensor 25: Reactor 26: Crank angle sensor R1: Intake path R2: Exhaust route

Claims

1. An exhaust gas purification device for use in an internal combustion engine of a vehicle, The exhaust purification device includes a power source, a reactor, and a control device, the reactor generates plasma by receiving a voltage from the power source to purify exhaust gas from the internal combustion engine; the control device changes a frequency of the voltage supplied by the power source based on a speed of the vehicle, a rotation speed of the internal combustion engine, or an opening degree of a throttle valve of the vehicle. Exhaust purification device.

2. The second frequency is higher than the first frequency; the control device sets a frequency of the voltage supplied by the power source to a first frequency when the speed of the vehicle is faster than a first speed, and sets a frequency of the voltage supplied by the power source to the second frequency when the speed of the vehicle is slower than the first speed. The exhaust gas purification device according to claim 1 .

3. The second speed is slower than the first speed; When the differential value of the opening degree of the throttle valve of the vehicle is smaller than a predetermined value, the control device sets the frequency of the voltage supplied by the power source to a first frequency when the speed of the vehicle is faster than the first speed, and sets the frequency of the voltage supplied by the power source to the second frequency when the speed of the vehicle is slower than the first speed; When the differential value of the opening degree of the throttle valve of the vehicle is greater than the predetermined value, the control device sets the frequency of the voltage supplied by the power source to a first frequency if the speed of the vehicle is faster than the second speed, and sets the frequency of the voltage supplied by the power source to the second frequency if the speed of the vehicle is slower than the second speed. The exhaust gas purification device according to claim 2 .

4. A control device for an exhaust gas purification device used in an internal combustion engine of a vehicle, The exhaust purification device includes a power source and a reactor, the reactor generates plasma by receiving a voltage from the power source to purify exhaust gas from the internal combustion engine; the control device changes a frequency of the voltage supplied by the power source based on a speed of the vehicle, a rotation speed of the internal combustion engine, or an opening degree of a throttle valve of the vehicle. Control device.

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