JPS61218708A - Exhaust fine particle processor of internal-combustion engine - Google Patents

Abstract

PURPOSE:To perform stable combustion of a fine particle while suppressing the worsening of fuel consumption and a smoke discharge amount, by gradually changing an intake pressure and maintaining the exhaust temperature to a predetermined value, in a predetermined operational region at not more than the predetermined temperature with an exhaust fine particle being combustible. CONSTITUTION:When it is decided by a regeneration timing decision means D that a trap C is in the regeneration timing, a processor, on the basis of signals from an operational condition detecting means I and an intake pressure detecting means H, controls and intake throttle valve driving gear G to hold the intake pressure almost to a fixed negative pressure till the exhaust temperature reaches a predetermined value enabling stable combustion of an exhaust fine particle, collectively caught in the trap C, to be performed. The processor controls an intake throttle under the full opening condition of an intake throttle valve, after the exhaust temperature reaches a predetermined value by the control, while so as to gradually increase the intake pressure before the exhaust temperature reaches the predetermined value. While the processor, when the exhaust temperature in higher than the predetermined value, holds the intake throttle valve to the full opening condition.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an exhaust particulate treatment device for an internal combustion engine.

(Prior art) In internal combustion engines such as diesel engines that are equipped with a trap in the exhaust passage to collect particulates such as carbon contained in the exhaust, when the number of exhaust particulates collected in the trap increases, the exhaust pressure rises excessively. However, the exhaust particulates collected in the trap are burned at a predetermined time to regenerate the trap.A conventional example of such an exhaust particulate treatment device is shown in Fig. 5 (Japanese Patent Laid-Open No. 58 −
(See Publication No. 51235).

That is, a trap 3 having a heat-resistant filter structure is interposed in the exhaust passage 2 of the engine 1 to collect exhaust particulates. Then, it determines when the trap 3 may need to be regenerated based on, for example, a predetermined travel distance, travel time, etc., and performs negative pressure control based on the duty signal from the control bag W4 when the engine 1 is in an operating state in which a large amount of surplus air flows into the engine 1. The valve 5 is operated to introduce negative pressure air from the negative pressure pump 7 into the pressure chamber 6a of the diaphragm device 6. As a result, the opening of the intake throttle valve 9 provided in the intake passage 8 is controlled to reduce the amount of excess air introduced and increase the exhaust temperature. In this way, the exhaust particulates collected in the trap 3 are burned by the heat of the heated exhaust gas, thereby regenerating the trap 3.

To explain in detail, the control device 4 includes a fuel injection pump 10.
A load signal and a rotational speed signal are input from a load sensor 11 and a rotational speed sensor 12 provided in the intake throttle valve 9, respectively, and a pressure signal is inputted from an intake pressure sensor 13 provided in the intake passage 8 downstream of the intake throttle valve 9. ing. Then, the control device 4 determines whether the operating state is one in which a large amount of surplus air flows into the engine l from the engine load and engine rotational speed detected when it is determined that it is time to regenerate the trap.

When it is determined that the engine is in the operating state, the control device 4 outputs a duty signal to the negative pressure control valve 5 to control excess air introduced into the engine 1 by the intake throttle valve 9. Here, the control device 4 changes the duty ratio of the duty signal based on the pressure signal of the intake pressure sensor 13. Due to this change, the negative pressure control valve 5
The intake air pressure downstream of the intake throttle valve 9 is maintained at a substantially constant level by controlling the amount of negative pressure air introduced into the intake throttle valve 9 and changing the opening degree of the intake throttle valve 9.

In addition, 6b is a diaphragm, 6C is a return spring,
14 is a rod attached to the diaphragm 6b;
A lever 5 has one end rotatably attached to the rod 14 and the other end attached to the valve shaft 9a of the intake throttle valve 9.

<Problems to be Solved by the Invention> However, in such a conventional exhaust particulate treatment device, when it is determined that the trap is regenerated and the intake throttle area is reached, the opening degree of the intake throttle valve 9 is controlled to reduce the intake negative pressure. Since it is maintained at a substantially constant value, there are the following problems.

Figure 6 shows changes in exhaust temperature, fuel consumption, and smoke emissions with respect to changes in engine load at a predetermined engine speed, when the intake is not throttled, and when the intake negative pressure is controlled to be approximately constant. . In other words, when restricting the intake air, the exhaust temperature is T8 at which the exhaust particulates are stably combusted when the load is above L+.
On the other hand, if the intake air is not throttled, the load reaches T at L2 or higher. Therefore, from the point of view of trap regeneration, it is preferable to release the intake throttle when the load is 2 or more.
However, as is clear from FIG. 6, under heavy load conditions, the intake throttle causes a rapid increase in fuel consumption and smoke emissions.

On the other hand, a control method that keeps the intake negative pressure constant until the load reaches L2 (constant cylinder intake air amount) can suppress the deterioration of fuel consumption and smoke emissions, but the exhaust temperature increases between L and Lt. There are problems in that the above-mentioned exhaust gas temperature Tt cannot be reached, making it difficult to burn exhaust particulates, and the region above the exhaust temperature obtained by the intake throttle becomes narrow.

The present invention was made in view of the above-mentioned circumstances, and provides an exhaust particulate treatment device that can secure an exhaust temperature at which exhaust particulates can be stably combusted over a wide operating range while suppressing deterioration in fuel consumption and smoke emissions. The purpose is to provide.

<Means for Solving the Problems> Therefore, as shown in FIG. 1, the present invention provides a trap C for collecting particulates in the exhaust gas of an internal combustion engine, which is installed in the exhaust passage B of the engine A and collects particulates in the exhaust gas. In the processing device, a regeneration time determining means for determining the regeneration time of the trap, an intake throttle valve F interposed in the intake passage E, an intake throttle valve driving means G for driving the intake throttle valve F to open and close, and the An intake pressure detection means H detects the intake pressure downstream of the intake throttle valve F, an operation state detection means I detects the operating state of the engine, and when it is determined that it is time to regenerate the 6-trap, Based on the signals from the pressure detection means I and the intake pressure detection means H, the intake pressure is controlled by the intake throttle valve drive means G until the exhaust temperature reaches a predetermined temperature at which the exhaust particulates collected in the trap can be stably combusted. The exhaust temperature is controlled to be maintained at a substantially constant voltage, and the exhaust temperature is maintained at the above-mentioned level from the time when the exhaust temperature reaches the predetermined temperature due to the intake throttle control until the operating state in which the exhaust temperature reaches the predetermined temperature under the condition that the intake throttle valve is fully open is reached. Intake throttle valve opening control that performs intake throttle control to gradually increase the intake pressure to maintain it near a predetermined temperature, and controls the intake throttle valve to maintain the intake throttle valve fully open in operating conditions where the exhaust temperature is higher than that. The device is equipped with means J.

In this way, in the predetermined operating range below a predetermined temperature where exhaust particulates can be combusted, the intake pressure is gradually changed to maintain the exhaust temperature at the predetermined temperature, and in the operating range below that temperature, the intake pressure is was kept approximately constant.

(Embodiment) An embodiment of the present invention will be described below based on FIGS. 2 to 4. Elements that are the same as those in the conventional example are given the same reference numerals as in FIG. 5, and their explanation will be omitted. .

In FIG. 2, the control device 20 includes a water temperature sensor 21 that detects the cooling water temperature and a load sensor 2 that detects the engine load.
2, a rotational speed sensor 23 that detects the engine rotational speed, exhaust pressure sensors 25a and 25b that detect the exhaust pressure on the inlet side and outlet side of the trap with catalyst 24, and intake pressure that detects the intake pressure downstream of the intake throttle valve 9. A detection signal is input from an intake pressure sensor 26 as a detection means. Here, the load sensor 22 is constituted by a potentiometer interlocked with a control lever 27a of the fuel injection pump 27, the rotation speed sensor 23 is constituted by, for example, a crank angle sensor, and the exhaust pressure sensors 25a, 25b, and the intake pressure sensor 26 are, for example, semiconductor type. The pressure sensor, particularly the intake pressure sensor 26, is configured to detect intake pressure as an absolute pressure. Further, the catalyst trap 24 is attached to a case 24b via a buffer material 24a.

The control device 20 includes a CPU 28 and a memory (ROM) 29.
In addition, an A/D converter 30 that converts analog data into digital data, an F/V converter 31 to which rotation pulses from the rotation speed sensor 23 are input; Detection voltage of rotational speed sensor 23 ■Detection voltage vL of load sensor 22, detection voltage vw of water temperature sensor 21, detection voltage VP of exhaust pressure sensors 25a and 25b
1. Vl-□, intake pressure sensor 2, a multiplexer 32 that selectively inputs one of the intake pressure output sensors IF to the A/D converter 30, and a PIO (peripheral interface) for interfacing with a grounding device 33 to be described later. l10
) 34. Further, the control device 20 receives the voltage V from the battery 35.

A constant voltage circuit 36 is provided which obtains a constant voltage VCC from the control device 20 and supplies it to each component of the control device 20.

Note that the CPU 2B is connected to the multiplexer 3 via the PIO 34.
EOC (End of Convert) indicates the end of conversion from the A/D converter 30.
) After receiving the signal, the digitally converted data is input.

The grounding device 33 includes a switching circuit 33a interposed in the grounding wire of the control solenoid valve, and a pressure chamber 6 of the diaphragm device 6.
a, and a switching circuit 33 inserted into the ground wire of a three-way switching solenoid valve 39, which is interposed in a pressure passage 38 that communicates the boat a of the control solenoid valve 37, and the switching circuits 33a and 33b are Mainly constructed using transistors. The control solenoid valve 37 is provided with a constant pressure valve 40 that adjusts the negative pressure from the negative pressure pump 7 to a substantially constant level, and a negative pressure extraction passage 41 that takes out the negative pressure from the constant pressure valve 40.
is connected in the middle of the pressure passage 38 that connects the boat a of the control solenoid valve 37 and the boat b of the three-way solenoid valve 39.

The boat a of the three-way solenoid valve 39 and the pressure chamber 6a of the diaphragm device 6 are communicated through the pressure passage 38, and the three-way solenoid valve 3
9 connects atmospheric pressure boat C and boat A in a non-energized state;
It is configured to connect boat b and boat a in an energized state. The control solenoid valve 37 is closed to the valve port 3 in a de-energized state.
7a is closed and energized, the valve port 37a is opened to introduce the atmosphere from the atmosphere introduction boat b, and dilute the negative pressure air in the pressure passage 38 with the atmosphere.

The control solenoid valve 37 normally opens and closes on and off at a frequency of about 30 to 50H2, and the control device 20 controls the on/off time ratio (control duty) and controls the energization of the three-way solenoid valve 39. That is, each switching circuit 33a
, 33b from the CPU 28 via the PI034, the grounding wires are made conductive and the control solenoid valve 37 and the three-way solenoid valve 39 are turned on.

Here, the CPU 28 operates according to a program based on the flowchart shown in FIG.

Here, the control device 20 serves both as a regeneration timing determining means and an intake throttle valve opening control means, and the diaphragm device 6 constitutes an intake throttle valve driving device. Further, the load sensor 22 and the rotational speed sensor 23 constitute an operating state detection means. Note that 42 is an ignition switch.

Next, the operation will be explained based on the flowchart shown in FIG.

Water temperature sensor 21. Load sensor 22. F/V
Rotational speed sensor 23 via transducer 31. The output voltages of the inlet side pressure sensor 25a and the outlet side pressure sensor 25b are vW, VR, Vt, VPl, Vpz.
It is stored in the storage unit (RAM) of PU2B. and S
2, the engine is started, for example, when the engine rotational speed is 50O
The determination is made based on whether or not the rpm is higher than the rpm, and if NO, the process proceeds to S33, where the three-way solenoid valve 39 is turned off, port a and boat c are communicated, the atmosphere is introduced into the pressure chamber 6a of the diaphragm device 6, and the intake throttle is stopped. . Then, the process advances to S34, where the control solenoid valve 37 is turned off (off duty 100%) to prevent power wastage and return to S1.

If YES in S2, the process proceeds to S3, where the differential pressure across the catalytic trap 24 (ΔVP = VPI - Vpz) is determined from the output voltage V p + + V r z, and the process proceeds to S4.

In S4, it is determined whether or not it is currently being played (CPU2
It is determined whether a signal indicating that playback is being stored is stored in the storage unit (RAM) of No. 8). If YES, proceed to S8, but since it is NO the first time after the engine starts, proceed to S5. S
In step 6, the reproduction timing is determined. That is, from (1)8 and vL, the limit difference Jj (differential pressure at the limit of one particle collection) set in the ROM 29 is determined by table lookup based on the rotational speed and load.

Then, proceed to S6, and the front and rear differential pressure ΔV is the limit differential pressure ΔVPxm
Determine whether or not x has been reached. If No, it is not time to play, so proceed to 333; if YES, CP is reached in S7.
The symbol indicating that regeneration is in progress is stored in the memory section (RAM) of U2B, and the symbol is transferred to memory LS8 to determine whether the cooling water temperature is, for example, 60°C or higher.If NO, the engine is insufficiently warmed up. Proceed to 333 because it is not suitable for intake throttle. Yes for S8
In other words, if the engine has been warmed up sufficiently, the process advances to S9, and the exhaust temperature in this operating state is determined from the rotational speed and load to the temperature at which exhaust particulates are stably combusted (in this example, the temperature at which the catalyst is sufficiently activated, for example). 400℃), and
If o, that is, if the exhaust gas temperature is 400° C. or higher, the process proceeds to S33, and if YES, the process proceeds to 810. In SIO, vR and vL
There is a region where the intake negative pressure is controlled to be approximately constant (region A in Figure 4), and a region where the intake negative pressure is changed in response to changes in load and rotational speed so that the exhaust temperature is 400°C (region A in Fig. 4). Control solenoid valve 37 that can obtain negative intake pressure (Fig. 4 Chunichi region)
The drive signal (S, duty ratio) of ROM2
9, and the control target intake negative pressures (■, □) set in the ROM 29 at Sll are determined by looking up the table from Vl and (■).

Here, the control target intake negative pressure v std is set to increase as the engine speed and load decrease in region B in FIG. 4, and to increase as the engine speed and engine load decrease in region A in FIG. is set to the maximum negative pressure in area B regardless of changes in .

Then, the process proceeds to 312 where the output VIP' of the intake pressure sensor 26 is
is stored in memory, and the process proceeds to S13. In S13, the control target value V, t of the intake pressure and the measured value v1. (both absolute pressure)
It is determined whether the control target value V, □ is the same as or larger than the measured value VIP. If YES, that is, if the intake throttle amount is appropriate or is too throttled, proceed to S14 and calculate the correction difference. The pressure ΔVIF (V, ta-V+p) is determined and the process advances to S15.

315, the corrected differential pressure Δv(P is the maximum level (ΔVtP□
8, for example, 50 mmHz), and if YES, the slow
An appropriate correction duty ratio ΔS1 for the on-duty ratio determined by. ．． Correct by adding x (for example, 20%) S19
Proceed to. If S I5TENO(7), then ΔvI in S17
F is the minimum level (ΔvIPI11i1% e.g. 20wm
Determine whether it is the same as or higher than Hg),
If YES, correct duty ratio ΔS at 818.
Add ll&i+s (for example, 10%), and if NO, proceed to 819 without correcting S. In S19, it is determined whether SI is equal to or greater than the maximum limit, that is, S01, and if YES, S is set to the maximum on-duty ratio 5IIIl.
l, l (for example, 90%), and if No, 5 without correction.
Proceed to 28. Here, 84□ is set to an on-duty ratio (for example, 90%) such that the negative pressure in the pressure chamber 6a of the diaphragm device 6 becomes a negative pressure that obtains a reaction force that is somewhat lower than the initial set load of the spring 6C. This improves the response speed of the intake throttle valve 9 to pressure changes.

If No in 313, that is, the measured value VIP is the target value ■st
If it is larger than 4 and the intake throttling amount is small, the process proceeds to S21 and calculates the corrected differential pressure ΔV+r (V+p-V, w) in S22.
Proceed to.

In S22, the corrected differential pressure ΔVIF reaches the maximum level (ΔVIP□
8) Determine whether it is the same as or greater than Ig) (for example, 50 mm), and if YES, subtract the appropriate correction duty ratio ΔSIIImX (for example, 20%) from the on-duty ratio S obtained by SIO in S23. Correct,
Proceed to S26. If No in S22, ΔVIF in S24
is equal to or higher than the minimum level (ΔVIPm!a, for example, 20 mmHg), and if YES, the corrected duty ratio Δ51m1 is determined from the SI in S25.
Subtract n (for example, 10%), and if no, add 3 without correction.
Proceed to step 26. In S26, it is determined whether Sl is less than the minimum on-duty ratio 5lai, 1 (for example, 10%), and if YES, S is set as the minimum on-duty ratio (10%), and if No, it is corrected. 32 without
Proceed to step 8. Here, the minimum on-duty ratio is such that the negative pressure in the pressure chamber 6a is obtained, which provides a reaction force that slightly exceeds the load of the spring 6C at the maximum lift of the rod 14 of the diaphragm device 6, and S2
As in the case of 0, the response speed of the intake throttle valve 9 to changes is increased.

At 32B, the three-way solenoid valve 39 is turned on to connect boats A and C, and at 329, a drive signal (S,) for the control solenoid valve 37 is output to open the valve port 37a at an appropriate on-duty ratio to open the diaphragm device 6. The amount of negative pressure air supplied to the pressure chamber 6a is appropriately controlled, and the opening degree of the intake throttle valve 9 is changed.

Then, in S30, the regeneration determination differential pressure ΔVps5n set in the ROM 29 (differential pressure indicating a state in which there is almost no amount of collected exhaust particulates in the trap) is looked up in the table from ■□ and vL, and in S31, the measured value ΔV, is the judgment value ΔV P
It is determined whether XI in has been reached or is less than that, and if No, the process returns to Sl and repeatedly performs intake throttling control. If YES in 331, initial settings are performed in 332. That is, in S7, the symbol indicating that regeneration is in progress is erased from the storage unit (RAM) of the CPU 2B, and the process proceeds to S33, where the three-way solenoid valve 39 is turned off and the intake throttle is stopped.
At step 4, the control solenoid valve 37 is turned off and the process returns to Sl.

As explained above, when the exhaust temperature is below 400°C, which is the activation temperature of the catalyst, the engine speed and load are As the exhaust temperature decreases, the intake negative pressure downstream of the intake throttle valve 9 is gradually increased (dashed line in Figure 6) to maintain the exhaust temperature at 400°C, so the catalyst is activated even in this operating range. The exhaust particulates collected in the catalyst trap 24 can be burned.

At this time, since the intake negative pressure is gradually increased as the engine speed and load decrease, excessive throttling is not performed, and smoke emissions and fuel consumption are reduced as shown by the broken line in Figure 6. It is possible to regenerate the trap in a wider range of operation than in the past, while also suppressing the deterioration of the trap significantly compared to the conventional one. In addition, in the A'pfJ region in Figure 4, the intake pressure downstream of the intake throttle valve 9 is controlled to be approximately constant, so as in the past, the exhaust temperature rises and the lowest temperature at which the catalyst is activated (
For example, an exhaust temperature of 350° C. or higher can be obtained in a predetermined region, making it possible to burn exhaust particulates.

Further, in an operating region where the exhaust gas temperature exceeds 400° C. (region C in FIG. 4), the trap 24 is regenerated using exhaust heat without restricting the intake air.

Although this embodiment describes a trap with a catalyst, the present invention can also be applied to a trap without a catalyst.

<Effects of the Invention> As explained above, the present invention gradually changes the intake negative pressure to maintain the predetermined temperature in a predetermined region of the operating region where the exhaust gas temperature is below a predetermined temperature at which exhaust particulates can be stably combusted; In addition, in the operating range other than the predetermined operating range, the intake air is throttled to maintain the intake negative pressure approximately constant. The trap can be regenerated by burning exhaust particulates in the operating region.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of the present invention, FIG. 2 is an overall diagram showing an embodiment of the present invention, FIG. 3 is a flowchart of the same, FIG. 4 is a diagram for explaining the operation of the same, and FIG. 6 is an overall view showing a conventional example of an exhaust particulate processing device, and FIG. 6 is a diagram for explaining the operation of the same and the above-mentioned embodiment. 2... Exhaust passage 8... Intake passage 9... Intake throttle valve 20... Control device 22... Load sensor 23... Rotational speed sensor 24... Trap with catalyst 25a. 25b...Exhaust pressure sensor 26...Intake pressure sensor Patent applicant Nissan Motor Co., Ltd. agent Patent attorney Fujio Sasashima Engine rotation speed - 111

Claims (1)

[Claims] An exhaust particulate processing device for an internal combustion engine that includes a trap installed in an exhaust passage of the engine to collect particulates in the exhaust gas, comprising a regeneration timing determination means for determining the regeneration timing of the trap, and an intake throttle installed in the intake passage. a valve, an intake throttle valve drive means for driving the intake throttle valve to open and close, an intake pressure detection means for detecting the intake pressure downstream of the intake throttle valve, an operating state detection means for detecting the operating state of the engine, and a trap. When it is determined that it is time for regeneration, the intake throttle valve is operated until the exhaust temperature reaches a predetermined temperature at which exhaust particulates collected in the trap can be stably combusted based on the signals from the operating state detection means and the intake pressure detection means. An operating state in which the intake pressure is maintained at a substantially constant negative pressure by control of the driving means, and after the exhaust temperature reaches the predetermined temperature by the intake throttle control, the exhaust temperature reaches the predetermined temperature under the condition that the intake throttle valve is fully open. The intake throttle valve is controlled to gradually increase the intake pressure in order to maintain the exhaust gas temperature near a predetermined temperature until the temperature reaches 1. An exhaust particulate treatment device for an internal combustion engine, comprising: an intake throttle valve opening control means.