JPS63106318A - Regenerator for particulate trap - Google Patents

Abstract

PURPOSE:To perform combustion propagation in optimum conductions, by fixing an inlet valve to the specified opening at a time when detecting ignition to a trap, while controlling the opening of a bypass valve so as to cause differential pressure in the inlet valve to become the specified value corresponding to an optimum flow rate. CONSTITUTION:A control unit 11 first discriminates afterburning timing of a particulate trap 1 on the basis of a signal out of a distance sensor 10. Next, at a point of time reaching the afterburning timing, a bypass valve 6 is opened, and an inlet valve 5 of the trap 1 is closed instead, while an electric heater 2 is energized with a continuous rating current via a power switch 9, making gas temperature go up. And, output of an inlet temperature sensor 3 of the trap 1 is compared with the specified value, and ignition to the trap 1 is detected. In this case, after the inlet valve 5 is fixed to the specified opening, differential pressure at both sides of the inlet valve 5 is detected. And, when the detected differential pressure is not reached to the specified differential pressure, opening of the bypass valve 6 is controlled.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a device for regenerating a trap that collects particulates in the exhaust gas of a diesel engine, etc. This invention relates to a device that controls the flow rate.

[Conventional technology]

Conventional particulate trap regenerators that control the flow rate during reburning include, for example, Utility Model Application No. 59-1.
No. 7213, and Japanese Unexamined Patent Publication No. 59-20514.

First, in Japanese Utility Model Application Publication No. 59-17213, only a bypass valve is provided in the particulate trap, and no valve is provided on the inlet side.

Particulates are collected by closing the bypass valve.

When it is detected that it is time to regenerate the trap, the bypass valve is opened and the electric heater installed on the front of the trap is energized to ignite the particulates that have already been collected. By closing the trap, exhaust gas is introduced into the trap again and particulates are combusted and propagated.

In addition, in JP-A-59-20514, the trap is provided with both an inlet valve and a bypass valve, and when the trap is regenerated (when the cumulative value of the engine rotational speed exceeds a predetermined value), a valve is provided in front of the trap. The electric heater is energized, the inlet valve is closed, the bypass valve is opened, and when the exhaust gas temperature exceeds a predetermined value and ignition of particulates is detected, the amount of gas introduced into the trap is controlled to a constant level. Both the inlet valve and the bypass valve are controlled by reading out the inlet valve opening degree and the bypass valve opening degree from the memory according to the engine speed and load.

[Point S while the invention is trying to solve the problem]

Such conventional particulate trap regeneration devices have the following problems.

First, in the case of Utility Model Application Publication No. 59-17213, the reburning control of the trap is not by controlling the opening degree of the bypass valve, but by smoothly controlling the bypass valve to open and close, thereby reducing the amount of exhaust gas to the trap. Since the method of gradually increasing the amount of gas introduced into the trap is adopted, the amount of gas entering the trap is not particularly controlled, and the amount of incoming gas is too large, causing combustion to propagate toward the trap outlet after ignition by the heater. There were times when it would disappear midway through. This is because a certain optimum amount of gas is required in order to introduce gas after ignition by the heater and to promote combustion.

In addition, in the case of JP-A-59-20514, an engine speed sensor and a load sensor are required, and a map regarding the inlet valve opening and bypass valve opening according to the engine speed and load is stored in memory. Since it is necessary to store the memory, the controller (C
This increases the capacity of PU), leading to a rise in costs.

Therefore, an object of the present invention is to realize a particulate trap regeneration device that can introduce an optimal gas flow rate to the trap using a simple configuration that does not require a memory map.

[Means for solving problems]

As a means to solve the above problems, the particulate trap regeneration device according to the present invention uses a temperature sensor on the inlet side of the particulate trap provided in the exhaust system of the engine, and a temperature sensor that detects the differential pressure before and after the trap inlet valve. A pressure sensor, and a control means for fixing the inlet valve at a predetermined opening degree and controlling a bypass valve so that the differential pressure becomes a predetermined value after ignition is detected based on the energization of the electric heater and the temperature on the inlet side. There is.

[For production]

In the present invention, when it is time to regenerate the particulate trap and the trap is re-burned by an electric heater as usual, the output of the temperature sensor provided on the inlet side of the trap is input to the control means, and the output is When reaches a predetermined value, it is determined that the trap has ignited, and the opening degree of the trap inlet valve is fixed at a predetermined value. Then, the differential pressure on both sides of the inlet valve is detected by a differential pressure sensor so that the amount of gas flowing into the trap is always constant, and the control means controls the opening degree of the bypass valve to maintain the differential pressure of the inlet valve at a predetermined value. The combustion transmission tl is aimed at.

〔Example〕

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

FIG. 1 shows an embodiment of the present invention, where l is a well-known particulate trap (hereinafter simply referred to as trap) connected to the exhaust pipe BP of a diesel engine (not shown) or the like. , an electric heater 2 is attached to the front surface on the entrance side. 3 and 4 are temperature sensors installed on the inlet and outlet sides of the trap 1, respectively; 5 is a trap inlet valve that opens and closes the exhaust gas from the engine flowing into the trap 1; and 6 is a bypass that bypasses the trap 1. 7 is a vacuum switching valve (VSV) that controls the opening and closing of valves 5 and 6; 8 is a differential pressure sensor that is installed on the inlet side of trap l to detect the differential pressure on both sides of trap inlet valve 5; 9 is an electric heater 10 is a distance sensor such as a distance meter that detects the mileage of the vehicle, and 11 is a switching valve 7 and a heater power supply in response to a detection signal from sensor 3.4.8. A control unit (CPU) serves as a control means for sending control signals to the switch 12.

FIG. 2 is a diagram showing a flowchart of a program executed by the control unit 11. The operation of the particulate trap reproducing apparatus shown in FIG. 1 will be described below with reference to the flowchart of FIG. 2.

Before reburning the trap 1, the control unit 11 determines whether it is time to reburn the trap 1 every time the vehicle travels a certain distance based on the distance signal from the distance sensor 10. (Figure 2 step S1)
This is because particulates from the diesel engine accumulate in the trap 1 as the vehicle travels a certain distance, which serves as a guideline for trap regeneration. Instead of a constant mileage, the above-mentioned constant integrated value of the rotational speed is calculated based on the output signal of the engine rotational speed sensor, as shown in Japanese Patent Application Laid-Open No. 59-85417 or the above-mentioned Japanese Patent Application Laid-Open No. 59-20514. The same standard as above may be used, or the reburning timing may be determined by sensing an increase in the exhaust pressure of the trap 1. Both of these are well-known techniques.

When the reburning period is reached, the control unit 11
opens the bypass valve 6, closes the inlet valve 5 of the trap 1 (step S2), and energizes the electric heater 2 via the heater power switch 9 to increase the gas temperature (step S3). 1
The trap state is released and the reburning process begins.

After starting the reburning process, the control unit 11 compares the output of the inlet temperature sensor 3 provided on the inlet side of the trap 1 with a predetermined value in order to detect whether or not the trap 1 is ignited (step S4).

If the inlet temperature does not exceed the predetermined value, step S4 is repeated until the inlet temperature exceeds the predetermined value, and the inlet valve 5
Since the trap 1 is closed, the inlet temperature of the trap 1 inevitably rises, and when it exceeds a predetermined value, it is determined that ignition has been detected, and the inlet valve 5 is controlled to be fixed at a predetermined opening (step S5). This is done by providing a constant duty ratio to the duty solenoid of the switching valve 7.

If the inlet valve 5 is simply fixed at a predetermined opening degree (passage area is constant), if the progress of reburning or ignition condition changes depending on the driving conditions of the vehicle, the reburning may end incompletely or may not occur at all. (In this case, the remaining burnt material becomes dry by the time of the next reburning period, making it even more difficult to reburn), or the reburning may occur excessively (
In this case, the trap burns out (), so the gas flow rate of the trap 1 must be maintained at a constant optimum value for good reburning.

Therefore, in the present invention, the following processing is performed by paying attention to the fact that the optimal flow rate of the trap 1 and the differential pressure between the front and rear sides of the inlet valve 5 have a correlation.

That is, after the inlet valve 5 is fixed at a predetermined opening degree, the differential pressure sensor 8 installed on the inlet side of the trap 1 detects the differential pressure on both sides of the inlet valve 5, and the controller 11 receiving this detection signal The pressure difference is compared with a predetermined differential pressure (corresponding to the optimum flow rate to be stored) (step S6), and when the differential pressure is not at the predetermined value, the opening degree of the bypass pulp 6 is controlled to be changed (step S37). .

In this case, when the differential pressure is smaller than the predetermined value, trap 1
Since the gas flow rate to the gas flow rate is less than the optimum flow rate, the bypass pulp 6 is controlled in the direction of decreasing the opening degree of the bypass pulp 6. 71L, on the contrary, when the differential pressure is greater than a predetermined value, the flow rate of the gas introduced into the trap 1 is greater than the optimum flow rate, so the bypass pulp 6 is controlled in a direction that increases the opening degree of the bypass pulp 6.

In this way, the reburning process is controlled so that the differential pressure across the inlet valve 5 is always constant and an optimum flow rate of gas is introduced into the trap 1.

The reburning process ends when the output of the outlet temperature sensor 4 provided on the outlet side of the trap 1 reaches a predetermined value (step S8), or after a predetermined period of time has elapsed since the electric heater 2 was energized. When this occurs (step S9), the electric heater 2 is turned off, the inlet valve 5 of the trap 1 is opened, and the bypass valve 6 is closed (step 5IO).

After this, it returns to the collecting state again.

〔Effect of the invention〕

As described above, in the particulate trap regeneration device according to the present invention, when ignition of the trap is detected, the inlet valve is fixed at a predetermined opening degree, and the differential pressure of the inlet valve is set to a predetermined opening corresponding to the optimum flow rate. Since the opening degree of the bypass valve is controlled so as to achieve the above value, it is possible to achieve the effect that the combustion propagation after ignition of the particulate can be performed optimally without the need for complicated control means such as a memory map.

[Brief explanation of the drawing]

FIG. 1 is a hardware configuration diagram showing an embodiment of a particulate trap regeneration device according to the present invention, and FIG. 2 is a flowchart of a program executed by the control unit shown in FIG. 1 in the present invention. figure,
It is. In Fig. 1, l is a particulate trap, 2 is a heater, 3.4 is a temperature sensor, 5 is a trap inlet valve, 6 is a bypass valve, 8 is a differential pressure sensor, 11
indicates a control unit, and EP indicates an exhaust pipe.

Claims (4)

[Claims] (1) A temperature sensor on the inlet side of the particulate trap installed in the exhaust system of the engine, a differential pressure sensor that detects the differential pressure before and after the trap inlet valve, 1. A particulate trap regeneration device comprising: control means for fixing the valve at a predetermined opening degree and controlling the bypass valve so that the differential pressure becomes a predetermined value. (2) The particulate trap regeneration device according to claim 1, wherein the control means detects the ignition when the output of the temperature sensor reaches a predetermined value. (3) The particulate trap regeneration device according to claim 1, wherein the control means determines to end the regeneration of the trap when the temperature on the outlet side of the trap reaches a predetermined value. (4) The particulate trap regeneration device according to claim 1, wherein the control means determines to end regeneration of the trap when a certain period of time has elapsed after the ignition.