JP4948385B2 - Exhaust temperature control device - Google Patents

Description

  The present invention relates to an exhaust temperature management technique for a catalyst provided in an exhaust system of an engine.

  In recent years, particularly in a diesel engine, in order to purify NOx in exhaust gas into a harmless component by a reduction reaction, a liquid reducing agent or a precursor thereof is supplied to the exhaust gas and a reduction catalyst is provided in an exhaust passage downstream thereof, Alternatively, a DPF (Diesel Particulate Filter) that captures particulate matter in the exhaust is provided in the exhaust passage. It is known that these catalysts provided in the exhaust passage have an activation temperature, and the function can be lowered when the temperature is lower than the activation temperature. In particular, when exhaust gas having a relatively low temperature such as when idling flows to the catalyst and the catalyst temperature decreases, there is a problem that desired catalyst performance is hardly exhibited during subsequent acceleration.

Therefore, in a stopped state, control is performed to raise the temperature of the exhaust by closing the exhaust shutter used for the exhaust brake and increasing the idle rotation speed (see, for example, Patent Document 1).
Japanese Utility Model Publication No. 05-017112

  Such an exhaust shutter used for raising the temperature of the exhaust gas is manufactured so as to have a predetermined opening without being completely closed even by the closing control. As a matter of course, there is a manufacturing error for each product with respect to the opening when fully closed, but if this error is on the open side (that is, the error when opening when fully closed), it will flow out. Since the amount of exhaust increases, the desired temperature rise effect cannot be obtained, and the target exhaust temperature may not be reached at the catalyst inlet.

  The present invention has been made in view of such a technical background, and can obtain a target exhaust temperature even when a factor that affects the temperature rise such as an opening error of the exhaust shutter when it is fully closed fluctuates. An exhaust temperature control device that can be used is proposed.

The exhaust temperature control device proposed in the present invention is an exhaust temperature control device for an engine having an exhaust shutter upstream of the exhaust gas of a catalyst interposed in an exhaust passage, determines a target idle rotation speed, and closes the exhaust shutter. the determined operation control means for engine control to operate at the target idle rotational speed, current value confirmation means for confirming the instruction fuel injection quantity in the operation control by the operation control means, originally Oite the target idle rotational speed with Target value determining means for determining a target commanded fuel injection amount stored in advance as a desired value, and a rotational speed for correcting the target idle rotational speed based on the commanded fuel injection amount and the target commanded fuel injection amount It operates as correction means.

  According to the exhaust temperature control device according to the above proposal, when the exhaust shutter is closed and the engine is idling to raise the exhaust gas temperature, the product error at the exhaust shutter as described above affects the catalyst inlet. If the exhaust temperature does not rise sufficiently, this can be determined from the fuel injection amount, and control can be performed to correct the idle rotation speed and increase the rotation. If the engine speed increases, the exhaust temperature can be raised by that amount, so that even if a factor that affects the temperature rise fluctuates, the target exhaust temperature can be obtained.

  FIG. 1 shows an example in which the present invention is applied to a diesel engine in which a catalyst is interposed in an exhaust passage and an exhaust shutter is provided upstream of the exhaust.

  A turbine 3a of a supercharger 3 is incorporated in the exhaust passage 2 of the engine 1, and an exhaust shutter 4 constituting an exhaust brake is provided downstream of the turbine 3a. A muffler 5 is provided in the exhaust passage E downstream of the exhaust shutter 4 and the catalyst 6 is accommodated therein. The catalyst 6 can be a DPF, a reduction catalyst, an oxidation catalyst or the like as described above. The muffler 5 is provided with an exhaust temperature sensor 7 for measuring the exhaust temperature at the inlet of the catalyst 6. On the other hand, the compressor 3b of the supercharger 3 is incorporated in the intake passage 8, and an air cleaner 9 and an intake air temperature sensor 10 are provided upstream of the intake air. An intercooler 11 is provided downstream of the compressor 3b.

  The exhaust temperature control device of the engine 1 is realized by an ECU (electronic control unit) 12. That is, the ECU 12 operates as an operation control means, a current value confirmation means, a target value judgment means, a rotation speed correction means, and a temperature judgment means according to the program, and executes control. The control flow is shown in FIG. In the flowchart, the operation control means is step S1 to step S4 and step S8, the current value confirmation means is step S5, the target value judgment means is step S6, the rotation speed correction means is step S7, and the temperature judgment means is step S9. Handle. Such an ECU 12 may be configured as being incorporated in the engine ECU, or may be configured as a chip different from the engine ECU.

  First, the ECU 12 determines whether the vehicle speed is zero, the parking brake is applied, and the gear is neutral (clutch off), that is, whether the engine operating condition is idle. At this time, in the case of a vehicle provided with an exhaust gas temperature raising switch that can be switched on / off of the exhaust gas temperature raising control by the driver's operation, the switch on is also determined. As a result, when the idling operation is confirmed, the exhaust gas temperature raising control is started.

  After starting the temperature increase, the ECU 12 operating as the operation control means reads the value of the intake air temperature sensor 10 and determines the outside air temperature (step S1). Based on the read measured value of the intake air temperature, a map of the intake air temperature and the rotational speed as shown in the figure stored in advance in the internal memory is accessed to determine the target idle rotational speed (step S2).

  The reason for determining the target idle speed based on the intake air temperature in steps S1 and S2 is as follows. That is, when the intake air temperature (= outside air temperature) is considerably low, the temperature of the exhaust gas before the temperature increase is originally low, and it takes time to increase the temperature. Further, the temperature in the exhaust passage 2 between the engine 1 and the catalyst 6 is increased. Since the influence of the decrease (cooled by the outside air temperature) also becomes large, there is a case where a sufficient temperature raising effect cannot be obtained even if the exhaust gas temperature raising control is performed. Therefore, when the target idle rotation speed is determined, if the rotation speed is determined according to the intake air temperature, it can be adjusted to increase the temperature rise effect by controlling the rotation at a higher speed when it is cold. .

  After determining the target idle rotation speed, the ECU 12 controls to close the exhaust shutter 4 (step S3), and controls the engine to operate at the target idle rotation speed (step S4). If the ECU 12 is realized in the engine ECU, the engine 1 can be directly controlled. If it is separate from the engine ECU, it can be controlled by issuing a command to the engine ECU.

  During this operation control, the ECU 12 operates as a current value confirmation means, and reads and confirms the commanded fuel injection amount (step S5). The command fuel injection amount is a current command value output from the engine ECU to the fuel injection device of the engine 1.

  The ECU 12 that has confirmed the current value operates as target value determining means, and the target command fuel injection amount at the target idle speed determined in step S2 is stored in the internal memory in advance, as shown in the figure. Judgment is made with reference to the map of the intake air amount Q (step S6). The target command fuel injection amount is a value measured using the exhaust shutter 4 having the median value or the minimum value of the variation in the fully closed opening due to a product error, and the engine when the exhaust shutter 4 is closed and the idling operation is performed. 1 is an indicated fuel injection amount issued by the engine ECU for each rotation speed. That is, it is set as the ideal commanded fuel injection amount that should be.

  The ECU 12 that has determined the target commanded fuel injection amount operates as a rotational speed correcting means, and uses the target fuel injection amount determined in step S2 based on the commanded fuel injection amount in step S5 and the target commanded fuel injection amount in step S6. Correction is made (step S7).

  As shown in the map of Ne and Q in FIG. 2, the commanded fuel injection amount has a relationship that decreases as the opening degree of the exhaust shutter 4 opens. Therefore, the opening degree when the exhaust shutter 4 is fully closed is opened due to a product error. The actual commanded fuel injection amount (dotted line) tends to decrease with respect to the target commanded fuel injection amount (solid line) that should originally be at a predetermined target idle speed. In other words, if there is a difference between the commanded fuel injection amount (step S5) and the target commanded fuel injection amount (step S6), there is an error in the fully closed opening of the exhaust shutter 4 that is mounted, and it swings to the open side. It shows that. Therefore, in order to obtain an exhaust temperature increasing effect equivalent to that of the exhaust shutter 4 having a normal fully closed opening, the target idle rotation speed is increased to compensate for the difference (arrow).

  Based on the difference between the commanded fuel injection amount and the target commanded fuel injection amount, the ECU 12 that operates as the rotational speed correcting means accesses a map of the difference and the correction amount as shown in the figure stored in advance in the internal memory, The correction amount of the target idle rotation speed is determined.

  When the correction amount is determined, the correction amount is added to the target idle rotation speed determined in step S2, and the ECU 12 controls the engine as an operation control means based on the corrected target idle rotation speed (step S8). Thereby, since the target idle rotation speed is increased, the rotation of the engine 1 is increased, and the exhaust gas temperature can be raised accordingly. Therefore, even if a factor that affects the temperature rise of the exhaust is varied, the target exhaust temperature can be obtained.

  After starting the engine control based on the corrected target idle rotation speed, the ECU 12 operates as a temperature determination unit, reads the value of the exhaust temperature sensor 7, and determines the catalyst inlet temperature, that is, the temperature of the exhaust gas flowing into the catalyst 6. (Step S9). For example, if the exhaust gas temperature does not reach the target temperature (for example, the catalyst activation temperature) even if the temperature determination is repeated several times, the driver's seat lamp is turned on, for example. This allows the driver to make a failure determination.

The figure which showed embodiment of the engine provided with the exhaust temperature control apparatus. The flowchart of the control which an exhaust gas temperature control apparatus performs.

Explanation of symbols

1 Engine 2 Exhaust passage 3 Supercharger 4 Exhaust shutter 5 Muffler 6 Catalyst 7 Exhaust temperature sensor 8 Intake passage 9 Air cleaner 10 Intake temperature sensor 11 Intercooler 12 ECU (Exhaust temperature control device)

Claims (4)

An exhaust temperature control device for an engine having an exhaust shutter upstream of exhaust gas from a catalyst interposed in an exhaust passage,
An operation control means for determining a target idle speed, closing the exhaust shutter and controlling the engine so as to operate at the determined target idle speed;
Current value confirmation means for confirming the indicated fuel injection amount during operation control by the operation control means;
Target value determination means for determining a target instruction fuel injection quantity that is previously stored as the rightful value Oite to the target idle rotational speed,
A rotational speed correcting means for correcting the target idle rotational speed based on the commanded fuel injection amount and the target commanded fuel injection amount;
An exhaust gas temperature control device that operates as:   2. The exhaust temperature control apparatus according to claim 1, wherein the rotation speed correction unit determines a correction amount of the target idle rotation speed based on a difference between the commanded fuel injection amount and the target commanded fuel injection amount. .   The exhaust temperature control device according to claim 1 or 2, wherein the operation control means determines the target idle rotation speed based on an intake air temperature.   A temperature determination unit that determines the temperature of the exhaust gas flowing into the catalyst after correcting the target idle rotation speed by the rotation speed correction unit and notifies when the target temperature is not reached, is further operated. Item 4. The exhaust temperature control device according to any one of Items 1 to 3.

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