JPH07150930A - Duty controller of electric motor and exhaust emission control device of diesel engine - Google Patents

Abstract

PURPOSE:To provide a duty controller of an electric motor and an exhaust emission control device of a diesel engine at low cost, capable of driving the electric motor having little rush current. CONSTITUTION:A filter 7 and an electric heater 8 are provided on an exhaust system of a diesel engine 1, and an electrically powered air pump 11 supplies secondary air to the filter 7. An ECU 12 is provided with a microcomputer 13 for outputting a low-frequency duty signal as a driving signal of an electric motor 11a of the electrically powered air pump 11, a high frequency generating circuit 14 for outputting a high-frequency pulse signal, and an AND gate for outputting a signal by taking the logical product of the signal of the high frequency generating circuit 14 and the signal of the microcomputer 13. The microcomputer 13 ignites particulates collected by the filter 7 in an electric heater 8 and also incinerates particulates collected by the filter 7 by driving the electric motor 11a, so as to regenerate the filter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a duty control device for an electric motor and an exhaust emission control device for a diesel engine.

[0002]

2. Description of the Related Art D as a measure against black smoke in diesel engines
A PF (diesel particulate filter) system is adopted (for example, Japanese Patent Laid-Open No. 62-1627).
13 publication). For example, as shown in FIG. 5, a DPF 32 that collects particulates is provided in the exhaust system of the diesel engine 31, and the electric heater 34 is energized when the filter is regenerated by the ECU 33.
The particulate matter collected in 2 is ignited, and D is driven by driving the DC motor 35a of the electric air pump 35.
Secondary air was supplied to the PF 32 to incinerate the particulates collected by the DPF 32.

In order to prevent the filter (DPF 32) from cracking or melting during regeneration in the DPF system, the electric air pump 3 is controlled by duty control or the like.
It is necessary to control the flow rate of the air pump body 35b of No. 5 to be constant. In FIG. 5, reference numeral 36 denotes a rotation speed sensor, 37,
38 is a pressure sensor, 39 is a temperature sensor, 40 is a regeneration request lamp, and 41 is a regeneration start switch.

[0004]

However, in the case of duty-controlling the electric motor 35a of the electric air pump 35, in the duty driving of a low frequency which can be directly controlled by the microcomputer incorporated in the ECU 33, the inrush current is small when the duty ratio is small. Many flows, exceeding the rating of the electric motor 35a, causing a failure. Further, it is difficult to directly drive a high-frequency signal with a microcomputer in high-frequency duty driving, and an external circuit is added to the microcomputer to perform high-frequency duty driving. In this case, the external circuit In addition, an expensive D / A converter is required, resulting in high cost.

That is, the electric motor 35a is operated only by the low frequency signal.
When is driven, it becomes as follows. As shown in FIG. 6, when the duty ratio is large, a large inrush current flows in the first ON period, but gradually decreases and the current in the ON period falls to a small value. However, as shown in FIG. 7, when the duty ratio is small, a large inrush current of the first ON period flows similarly even after a lapse of time. This is because the rotation of the electric motor 35a is slow and the back electromotive force is small, so that the same current as at the time of starting flows. Further, in the case of generating a high frequency duty signal for driving an electric motor using a microcomputer, if a high frequency signal is directly generated from the microcomputer, the processing of the microcomputer cannot be performed in time and cannot be generated. Therefore, as shown in FIG. 8, the output of the microcomputer 42 is changed to the D / A converter 43.
Is converted into analog output with and the output and the triangular wave generator 44
The output from the above is compared by the comparator 45 to generate a high frequency duty signal. But with this method,
The D / A converter 43 and the like are expensive, and the cost is high as a whole.

Therefore, an object of the present invention is to provide a duty control device for an electric motor and an exhaust emission control device for a diesel engine that can drive the electric motor at a low cost and with a small inrush current.

[0007]

According to a first aspect of the present invention, in a control device in which a motor is duty-controlled, a microcomputer that outputs a low-frequency duty signal as a drive signal for the electric motor and a high-frequency pulse signal are output. A duty control device for an electric motor, comprising: a high-frequency pulse signal generating circuit; and an AND gate configured to output a logical product of a high-frequency pulse signal from the high-frequency pulse signal generating circuit and a low-frequency duty signal of the microcomputer. Use as a summary.

According to a second aspect of the present invention, a filter provided in the exhaust system of the diesel engine for collecting particulates, a heater arranged in the vicinity of the filter, and a secondary air for supplying the filter with secondary air are provided. An electric air pump, and a control circuit for igniting the particulates collected by the filter by the heater and driving the electric air pump to incinerate the particulates collected by the filter to regenerate the filter In a diesel engine exhaust emission control device, the control circuit includes a microcomputer that outputs a low-frequency duty signal as a drive signal for a motor of an electric air pump, a high-frequency pulse signal generation circuit that outputs a high-frequency pulse signal, and the high-frequency pulse. High frequency pulse signal from the signal generation circuit and low frequency duty of the microcomputer No. The exhaust purification device for a diesel engine provided with the AND gate to output a logical product of the one in which the gist thereof.

[0009]

The microcomputer outputs a low-frequency duty signal as a drive signal for the electric motor. A high frequency pulse signal is output from the high frequency pulse signal generation circuit.
Then, the AND gate takes the logical product of the high frequency pulse signal from the high frequency pulse signal generation circuit and the low frequency duty signal of the microcomputer and outputs the logical product to the electric motor. Therefore, by combining a high-frequency signal with a low-frequency signal having a small duty ratio, the applied voltage becomes “0” before the inrush current rises, so that the inrush current becomes small.
Further, a high frequency duty signal can be generated without using the circuit shown in FIG.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an overall configuration diagram of an exhaust emission control device for a diesel engine.

The vehicle is equipped with a diesel engine 1. The diesel engine 1 has an intake pipe 2 and an exhaust pipe 3
And are connected. The intake pipe 2 is provided with an engine air cleaner 4. Also, diesel engine 1
The exhaust pipe 3 is provided with a housing 6 of an exhaust emission control device 5. The housing 6 communicates with the exhaust pipe 3, and the exhaust gas of the diesel engine 1 passes through the housing 6. A filter (DPF) 7 is provided in the housing 6, and the filter 7 collects particulates discharged from the diesel engine 1. Further, an electric heater 8 is provided at the upstream end of the filter 7, and when the electric heater 8 is energized, the electric heater 8 generates heat to ignite the particulates collected by the filter 7.

A secondary air supply pipe 9 is branched on the upstream side of the housing 6 in the exhaust pipe 3, and an electromagnetic valve 10 is arranged in the middle of the secondary air supply pipe 9. The electromagnetic valve 10 is for preventing exhaust gas from flowing back into the secondary air supply path during normal operation. The discharge side of the air pump body 11b of the electric air pump 11 is connected to the tip of the secondary air supply pipe 9. Air pump body 1
A DC motor 11a is drivingly connected to 1b. Then, when the electromagnetic valve 10 is opened, the secondary air is supplied to the exhaust pipe 3 of the diesel engine 1 by driving the air pump body 11b by the rotation of the electric motor 11a.

As shown in FIG. 2, the ECU 12 as a control circuit comprises a microcomputer 13, a high frequency generating circuit (high frequency pulse signal generating circuit) 14 and an AND gate 15. The high frequency (20 KH
The pulse signal of z) is output to the AND gate 15.
Further, a low frequency (100 Hz) signal with a variable duty ratio is output from the microcomputer 13 to the AND gate 15.
The AND gate 15 outputs a signal that is the logical product of the signal from the high frequency generation circuit 14 and the signal from the microcomputer 13 to the electric motor 11a of the electric air pump 11. The drive of the electric motor 11a of the electric air pump 11 is controlled by this signal.

Further, in FIG. 1, the microcomputer 13 is connected to the switching element 24, and the energization of the electric heater 8 is controlled according to the control signal from the microcomputer 13. further,
The microcomputer 13 is connected to the electromagnetic valve 10, and the microcomputer 1
The opening / closing of the electromagnetic valve 10 is controlled according to the control signal from the control unit 3.

Further, a rotation speed sensor 16 for detecting the engine rotation speed, a front pressure sensor 17, a rear pressure sensor 18, and a filter 7 for detecting pressures on the upstream side and the downstream side of the filter 7, respectively.
Incoming gas temperature sensor 19 for detecting the temperature of exhaust gas flowing into the
Is provided, and the output signals of these sensors 16, 17, 18, 19 are fetched by the microcomputer 13.

Further, the reproduction request lamp 20 is provided in the microcomputer 13.
Is connected, and the regeneration request lamp 20 is for lighting to inform the driver of the regeneration time. Further, the reproduction start switch 21 is connected to the microcomputer 13, and the driver operates the reproduction start switch 21 to start the reproduction of the filter 7.

A plug 23 is connected to the power supply circuit 22,
When the plug 23 is connected to an external power source when the vehicle is stopped, external electric power can be supplied to the electric heater 8 and the electric motor 11a of the electric air pump 11.

Next, the operation of the exhaust gas purifying apparatus for a diesel engine thus constructed will be described. During operation of the diesel engine 1, the microcomputer 13 detects the exhaust gas temperature from the inlet gas temperature sensor 19 and the engine from the rotational speed sensor 16 with respect to the differential pressure across the filter 7 obtained from the front pressure sensor 17 and the rear pressure sensor 18. The clogging state of the filter 7 is estimated by adding the correction of the rotation speed and the like. And the microcomputer 13
Determines when regeneration is necessary from the clogging state of the filter 7 and informs the driver of the regeneration timing by turning on the regeneration request lamp 20.

After the plug 23 is connected to the external power source when the diesel engine 1 is stopped, the driver pushes the regeneration start switch 21 to filter the filter 7.
Will start playing.

The operation of the microcomputer 13 during reproduction is shown in FIG.
It will be described according to the flowchart of First, the microcomputer 1
3 detects the clogging of the filter 7 in step 100 by the above-mentioned method, and as a result, when it is determined that the regeneration is not necessary, this routine is ended. On the other hand, if the reproduction is required, the microcomputer 13 determines in step 101 whether or not the reproduction start switch 21 is pressed, and if it is pressed, the reproduction process is executed in step 102 and subsequent steps.

The microcomputer 13 opens the electromagnetic valve 10 in step 102 so that air (oxygen) can be supplied from the electric air pump 11. Further, the microcomputer 13 controls the energization of the electric heater 8 so as to obtain the optimum electric power in step 103, and controls the drive of the electric motor 11a of the electric air pump 11 so as to obtain the optimum amount of secondary air in step 104. The electric motor 11a of the electric air pump 11
At the time of driving, the high-frequency pulse signal from the high-frequency generation circuit 14 and the low-frequency signal with a variable duty ratio from the microcomputer 13 are input to the AND gate 15 in the ECU 12, and the AND gate 15 performs logical product Is taken and the signal is output to the electric motor 11a of the electric air pump 11. As shown in FIG. 4, by combining a low-frequency signal with a small duty ratio with a high-frequency signal, this signal has an applied voltage of "0" before the inrush current rises, so the inrush current becomes small.

In this way, the particulate matter collected in the filter 7 is ignited by the electric heater 8 and the electric motor 11a of the electric air pump 11 is driven by the duty control to collect the particulate matter collected in the filter 7. It is incinerated and the filter is regenerated.

Then, in FIG. 3, the microcomputer 13 determines the elapsed time after the start of reproduction in step 105, and terminates the reproduction if the set time has elapsed. As described above, in the present embodiment, the ECU 12 (control circuit) outputs the low frequency (100 Hz) duty signal as the drive signal for the electric motor 11a of the electric air pump 11 to the microcomputer 1.
3, a high frequency generation circuit 14 (high frequency pulse signal generation circuit) that outputs a high frequency (20 KHz) pulse signal, a high frequency pulse signal from the high frequency generation circuit 14 and a low frequency duty signal of the microcomputer 13 And an AND gate 15 for outputting. That is, the microcomputer 13 outputs a low-frequency duty signal as a drive signal for the electric motor 11a of the electric air pump 11.
Further, a high frequency pulse signal is output from the high frequency generation circuit 14. Then, the AND gate 15 calculates the logical product of the high frequency pulse signal from the high frequency generation circuit 14 and the low frequency duty signal of the microcomputer 13, and outputs the logical product to the electric motor 11 a of the electric air pump 11. Therefore, by combining a high-frequency signal with a low-frequency signal having a small duty ratio, the applied voltage becomes “0” before the inrush current rises, so that the inrush current becomes small. Also, FIG.
A high frequency duty signal can be generated without using the expensive D / A converter 43 or the like in the circuit shown in FIG. In this way, it becomes possible to drive the electric motor 11a at low cost and with a small inrush current.

The present invention is not limited to the above-described embodiment. For example, although the present invention is embodied as an exhaust emission control device for a diesel engine in the above-described embodiments, various devices using duty control devices for other electric motors are used. May be embodied in.

[0025]

As described above in detail, according to the present invention,
The excellent effect of being able to drive an electric motor that is inexpensive and has a small inrush current is exhibited.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an exhaust emission control device for a diesel engine of an embodiment.

FIG. 2 is an electrical configuration diagram of an ECU.

FIG. 3 is a flowchart for explaining the operation of the embodiment.

FIG. 4 is a timing chart for explaining the operation of the embodiment.

FIG. 5 is an overall configuration diagram of a conventional diesel engine exhaust emission control device.

FIG. 6 is a timing chart showing waveforms.

FIG. 7 is a timing chart showing waveforms.

FIG. 8 is an electric circuit diagram for explaining a conventional technique.

[Explanation of symbols]

1 Diesel Engine 7 Filter 8 Electric Heater 11 Electric Air Pump 11a Electric Motor 12 ECU as Control Circuit 13 Microcomputer 14 High Frequency Generation Circuit as High Frequency Pulse Signal Generation Circuit 15 AND GATE

Front page continuation (72) Inventor Nobufumi Houra, 1-1, Showa-cho, Kariya, Aichi Prefecture, Nihon Denso Co., Ltd. (72) Inventor, Shuji Yoshida, 1-1, Showa-cho, Kariya, Aichi Nippondenso Co., Ltd. (72) Inventor Keiichi Kato, 1-1, Showa-cho, Kariya city, Aichi prefecture, Nihon Denso Co., Ltd. (72) Inventor, Takayuki Toya, 1-1, Showa-cho, Kariya city, Aichi prefecture, Nihon Denso Co., Ltd. (72) Inventor Kiyoji Kobata Toyota Automobile Co., Ltd. 1 Toyota Town, Toyota City, Aichi Prefecture (72) Inventor Kotaro Hayashi 1 Toyota Toyota Co., Ltd. Toyota City, Aichi Prefecture (72) Inventor Hiroyuki Taniguchi Kariya Karie, Aichi Prefecture 2-chome Toyota-cho, Yokohama-shi Stock company Toyota Industries Corporation

Claims (2)

[Claims] 1. A control device for duty-controlling an electric motor, comprising: a microcomputer that outputs a low-frequency duty signal as a drive signal for the electric motor; a high-frequency pulse signal generation circuit that outputs a high-frequency pulse signal; and the high-frequency pulse signal. A duty control device for an electric motor, comprising: an AND gate that outputs a logical product of a high frequency pulse signal from a generation circuit and a low frequency duty signal of the microcomputer. 2. A filter provided in an exhaust system of a diesel engine for collecting particulates, a heater arranged in the vicinity of the filter, an electric air pump for supplying secondary air to the filter, Exhaust gas purification of a diesel engine provided with a control circuit for igniting the particulate matter collected in the filter by the heater and driving the electric air pump to incinerate the particulate matter collected in the filter to regenerate the filter In the device, the control circuit, a microcomputer that outputs a low-frequency duty signal as a drive signal of the electric motor of the electric air pump,
A high frequency pulse signal generation circuit for outputting a high frequency pulse signal, and an AND gate for performing a logical product of the high frequency pulse signal from the high frequency pulse signal generation circuit and the low frequency duty signal of the microcomputer and outputting the AND gate An exhaust emission control device for diesel engines, which is characterized in that