JPH01142211A - Afterburner of particulate trap - Google Patents

Abstract

PURPOSE:To precisely regenerate, a trap for the afterburner in the caption by calculating the fore and aft differencial pressure ratio between the trap and a fixed restriction connected to the lower course of the trap and starting the afterburning of the trap when the ratio exceeds a reference value. CONSTITUTION:An inlet pressure sensor 12 for detecting the inlet side pressure (in reference atmospheric pressure) of a trap 1 and a differential pressure sensor 13, etc., which detects the pressure loss of the trap 1 i.e. a fore and aft differential pressure sensor 13 are provided and those detected signals are input to a controller 14. In this controller 14, the fore and aft differential pressure of the fixed restriction 2 of an exhaust silencer, etc., connected to the lower course of the trap 1 is calculated due to the inlet signal and also the fore and aft differential ratio between the trap 1 and the fixed restriction 2 is calculated. The fore and aft differential pressure ratio is compared with a predetermined reference value and in case the fore and aft differential pressure ratio exceeds the reference value, it is judged that the particulate collection is in its stable of completion and an electric current is sent to an electric heater 4 to start the afterburning process of the trap 1.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a device for re-burning particulates and whelks that collect particulates in exhaust gas from diesel engines, etc. The present invention relates to a device for controlling the start timing of reburning of a trap (hereinafter simply referred to as a trap).

[Conventional technology]

As the trap continues to collect particulates, it gradually becomes clogged, leading to a decrease in engine output and poor fuel efficiency. To prevent this, it is necessary to re-burn the particulates as the particulates continue to be collected.

As a device for detecting the collection state of such a trap, there is a device that determines when the distance traveled by the vehicle, the cumulative rotational speed of the engine, etc. exceeds a set value (e.g.,
20513), but this method does not take into account the operating condition of the engine at all, so the error is large (not practical).

Another method for detecting trap collection status is to detect the differential pressure across the trap by focusing on the fact that the differential pressure across the trap increases between the exhaust pressure on the inlet side and the exhaust pressure on the outlet side. It is conceivable that when the detected differential pressure reaches a certain differential pressure value, it is determined that trap collection is complete and the trap is re-burned.

A device for starting reburning of a trap based on the differential pressure across the trap is disclosed in Japanese Patent Application Laid-open No. 56-1158.
There is one disclosed in Publication No. 09.

In this Japanese Patent Application Laid-Open No. 56-115809, the differential pressure across the trap (pressure loss) is detected and the detected differential pressure is compared with a preset differential pressure, so that the differential pressure across the trap becomes the set differential pressure. When this happens, the burner is ignited to start reburning the trap, and the reburning ends when the time set by the timer has elapsed.

In this type of reburning method, the start of reburning is determined only based on the pressure difference between the front and rear without considering the engine speed or load, so it is not possible to accurately detect clogging of the trap, Combustion may start too early and damage the trap, or start too late and the particulates cannot be burned sufficiently.

Therefore, in JP-A-59-126019, in addition to the differential pressure across the trap, the engine speed and engine load (or the rate of change of these and the engine speed and load) are considered, and the differential pressure across the trap is set. Re-combustion is started when the differential pressure is reached.

Furthermore, in JP-A-60-108520, the ratio between the differential pressure across the trap and the differential pressure across a fixed throttle downstream of the trap (for example, a silencer) is monitored, and when the ratio exceeds a certain value, the trap is compensated. It determines that the collection is complete and starts reburning the trap.

[Problem that the invention seeks to solve]

In the conventional particulate trap reburning device described in JP-A-59-126019,
The engine speed and load were only taken into consideration in order to exclude from the trap reburning control the low rotational speed and low load areas of the engine with low exhaust pressure, where trap clogging cannot be accurately determined. It was not intended to correlate with differential pressure. For this reason, this JP-A-59-
The device disclosed in No. 126019 is also JP-A-56-115809.
As with the device in the publication, accurate reburning control cannot be achieved.

Furthermore, as mentioned above, in order to take into account not only the low rotational speed region and low load region of the engine, but also the entire range, the front and rear differential pressure (pressure wise) map for the engine speed and load is memorized, and the current It is already known that trap reburning starts when the actual differential pressure exceeds the differential pressure between the front and rear corresponding to the engine speed and load, but the pressure loss with respect to the engine speed and load is accompanied by a time delay. Therefore, the error in the pressure loss map in steady state becomes large.

On the other hand, in the case of JP-A-60-108520, the differential pressure across both the trap and the fixed throttle is measured, but since the position of the fixed throttle is affected by the temperature of the exhaust gas, The differential pressure across the fixed throttle becomes low, and this decrease varies depending on the amount of exhaust gas and gas temperature, so it includes errors that are difficult to correct.

Therefore, an object of the present invention is to be able to determine the reburning timing without directly measuring the differential pressure across the fixed throttle in a particulate trap reburning control device that is installed in the exhaust system of an engine and has a fixed throttle downstream. It lies in realizing the means.

[Means for solving problems]

In order to achieve the above object, the particulate trap reburning device according to the present invention includes a fixed throttle connected downstream of the particulate trap provided in the exhaust system of the engine, an inlet pressure sensor of the trap, A control means that calculates a differential pressure ratio between the trap and the fixed throttle from the inlet pressure and the differential pressure between the front and rear, and starts reburning of the trap when this ratio exceeds a reference value. ing.

[For production]

The principle of operation of the present invention will be explained using FIGS. 3 and 4.

As shown in the figure, a fixed throttle 20 is connected to the downstream side of a particulate trap 1 provided in the exhaust system of the engine.
If the differential pressure between the front and rear is P2, the inlet pressure is P-Pt +Pt, and the inlet pressure of trap 1 (relative to the atmosphere) P and trap 1
If the pressure loss, that is, the differential pressure P between the front and rear, is detected, the pressure loss of the fixed throttle 2, which is connected to the downstream side of the trap 1 and whose outlet pressure is approximately equal to atmospheric pressure, that is, the differential pressure P -P-P, is detected. Desired.

While the differential pressure P across the fixed throttle 2 is constant,
Since the differential pressure P1 across the trap 1 changes depending on the state of particulate collection, the ratio P, /P between the two changes as shown in Fig. 4, and serves as a reference for this ratio P, /Pt. A constant value (slope) K is determined in advance, and the actually determined value P, /
It can be seen that reburning of the trap 1 should be started when P exceeds the reference value K.

Therefore, in the present invention, the inlet pressure P is detected by the inlet pressure sensor, the differential pressure P across the trap 1 is detected by the differential pressure sensor, and the control means determines the pressure between the trap 1 and the fixed throttle 2 from these detected values. The front and rear differential pressure ratio is calculated as described above, and control is performed so that reburning of the trap 1 is started when this ratio exceeds a reference value.

〔Example〕

Embodiments of the particulate trap reburning device according to the present invention will be described below.

FIG. 1 shows an embodiment of the present invention, where l is a trap, 2 is a fixed throttle such as an exhaust silencer, 3 is an exhaust pipe,
4 is an electric heater installed on the front side of the inlet side of trap 1, 5 is a heater relay for turning on the power B of electric heater 4, 6 is a temperature sensor installed on the inlet side of trap 1, and 7 is connected to trap 1 8 is a bypass pipe that bypasses the trap 1; 9 is a bypass pulp that opens and closes the exhaust gas flow to the bypass pipe 8; 10 and 11 are the valves 7 and 9; Vacuum switching pulp (VSV) whose opening and closing are controlled by negative pressure from vacuum pump VP, 1
2 is an inlet pressure sensor that detects the pressure on the inlet side of the trap 1 (relative to atmospheric pressure), 13 is a differential pressure sensor that detects the pressure loss of the trap 1, that is, the differential pressure across the trap 1, and 14 is a sensor 6.1
A controller (CPU) serves as a control means that sends control signals to the heater relay 5 and the switching pulp 10.11 in response to detection signals of 2 and 13. The amount of throttling is determined so that the exhaust resistance is almost the same as the exhaust resistance when particulates are collected, which improves detection accuracy and silences noise when a predetermined amount of particulates are collected in trap 1. It also acts as a heat sink or a heat sink.

FIG. 2 is a diagram showing a flowchart of a program executed by the controller 14. The operation of the particulate trap reburning device shown in FIG. 1 will be described below with reference to the flowchart in FIG.

During normal particulate collection, the controller 14 controls the inlet valve 7 and the bypass valve 9 as shown in FIG. 1 so that the exhaust gas flows only to the trap 1 side.

In this state, the controller 14 always outputs the output signals P and P of the inlet pressure sensor 12 and differential pressure sensor 13.

(Step 31 in FIG. 2).

From these signals, ■ differential pressure p across the fixed throttle 2 is determined.
Calculate g = P - P, and based on this, ■ Trap 1
The ratio PI between the differential pressure P across the front and rear of the fixed throttle 2 and the differential pressure P2 across the fixed throttle 2
/pg =P, / (P-P,) is calculated (step S2).

The differential pressure ratio P I / P t obtained in this way is determined by the fixed orifice 2 which has no relation to the particulate collection state.
This shows how much particulate matter is collected in trap 1 based on the reference value, and therefore, as shown in Figure 4, the relationship between the amount of collected particles and the differential pressure ratio P, /P, is calculated in advance. Then, the slope =B/A can be considered as a value indicating the maximum permissible collection state.

Therefore, this value K is stored in the controller 14,
The actual front and rear differential pressure ratio P obtained by calculating this reference value K, /
P (step S3).

Then, when the ratio P, /P is greater than or equal to the reference value, it is determined that particulate collection has been completed, and the reburning process of the trap 1 is started.

Various types of reburning processes for the trap 1 are well known, but to explain them using the embodiment shown in FIG. 2, the controller 14:
The bypass valve 9 is opened, the inlet valve 7 of the trap 1 is closed, and the electric heater 4 is energized via the heater relay 5 to raise the gas temperature (step S4).

Control of the valves 7.9 is achieved by applying a constant duty ratio from the controller 14 to the solenoids of the respective associated switching valves 10 and 11.

Next, it is checked whether the temperature detected by the inlet temperature sensor 6 of the trap 1 has reached a predetermined value (T) (step S5), and if it has not reached the predetermined value, step S5 is continued until the predetermined value is reached. Repeatedly, since the artificial valve 7 is closed, the inlet temperature of the trap 1 inevitably rises, and when it exceeds a predetermined value, the artificial valve 7 is controlled to be fixed at a predetermined opening degree (step S6).

In this way, the reburning process is advanced, and when a predetermined period of time has elapsed since the inlet temperature reached the predetermined value in step S5 (step S7), the electric heater 4 is turned off.
8) When a predetermined period of time has passed since the heater 4 was turned off (step S9), the artificial valve 7 of the trap 1 is opened and the bypass pulp 9 is closed, thereby ending the reburning process (step 310).

After this, the trap 1 returns to the particulate collection state again.

〔Effect of the invention〕

As described above, in the particulate trap reburning device according to the present invention, the inlet pressure and the differential pressure across the trap are detected, and the differential pressure across the fixed throttle downstream of the trap is calculated based on these detected values. Since the start of reburning is controlled based on the differential pressure ratio between the trap and the fixed orifice, there is no need to actually measure the differential pressure across the fixed orifice, and therefore errors caused by the position of the fixed orifice can be eliminated. It is possible to detect the state of particulate collection with high precision even when the particulates are not contained, and the trap can always be regenerated to its optimal state without clogging or damage.

[Brief explanation of the drawing]

FIG. 1 is a hardware configuration diagram showing an embodiment of a particulate trap reburning device according to the present invention. FIG. 2 is a flow chart diagram of a program executed by the controller shown in FIG. 1 in the present invention. , FIG. 3 and FIG. 4 are diagrams for explaining the principle of operation of the present invention. In Fig. 1, ■ is a trap, 2 is a fixed throttle, 3 is an exhaust pipe, 12 is an inlet pressure sensor, 13 is a front and rear differential pressure sensor, 1
4 indicates a controller, respectively. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A fixed throttle connected downstream of a particulate trap provided in the exhaust system of the engine, an inlet pressure sensor and a differential pressure sensor across the trap, and a connection between the trap and the fixed throttle based on the inlet pressure and differential pressure across the trap. A reburning device for a particulate trap, comprising a control means for calculating a differential pressure ratio and starting reburning of the trap when the ratio exceeds a reference value.