JPH0568619B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a turbine that recovers exhaust energy to drive an engine, and that performs pumping work and brakes the engine by being reversely driven from the engine side. The present invention relates to a turbo compound engine having an exhaust bypass mechanism for controlling turbine operation and engine operation, which is composed of a bypass passage for detouring exhaust gas from the turbine and a bypass valve for adjusting the opening degree of the bypass passage.

[Prior Art] Generally, a turbo compound engine has an engine 2 equipped with an exhaust turbo supercharger 1, as shown in FIG.
In this case, the exhaust energy used for intake supercharging by the supercharger 1 is further recovered by the turbine 4 installed in the exhaust passage 3 on the downstream side of the supercharger 1, and taken out by the turbine 4. The shaft rotational force is supplied to the crankshaft 5 of the engine 2 to achieve high output of the engine 2. On the other hand, such an engine system in which rotational driving force is applied to the engine 2 by the turbine 4 in addition to intake supercharging requires considerable braking ability.

In recent years, the above-mentioned turbine 4 for exhaust energy recovery has been developed.
On the other hand, an engine system is proposed that adds engine braking force in addition to the conventional foot brake and exhaust brake by driving the pump from the engine 2 side and reversing its rotation to function as a floor for pump work. There is. What is shown in the figure is an example, and there is a reversing device 6 between the turbine 4 and the crankshaft 5 for rotating the turbine 4 in the forward and reverse directions, and a reversing device 6 that absorbs the rotational inertia (slip) when the turbine 4 is switched between the forward and reverse directions. By interposing a coupling mechanism 7 consisting of a reduction gear that adjusts the rotation speed and a fluid coupling, forward and reverse rotation of the turbine 4 and mutual transmission of driving force between the crankshaft 5 and the turbine 4 are achieved. It's summery. Furthermore, 8,9
are a hydraulic system for controlling the reversing device 6 and a cooling hydraulic system for cooling heat generated due to slipping and the like during forward/reverse switching.

In addition, this engine system supplies exhaust gas to the turbine 4 in order to drive the engine 2 by driving the turbine 4 in normal rotation (arrow A in the figure), in addition to the normal exhaust passage 3. In order to utilize the intake air for the pumping work of the turbine 4 which functions as a blower, the turbine 4 is
An intake air introduction path 11 (arrow B in the figure) for introducing intake air is provided on the exit side of the engine. This introduction path 11
is controlled to open and close by an on-off valve 12 installed therein, and is designed to supply air to the intake turbine 4 only when the engine is braked (when the turbine is reversed). Further, the exhaust passage 3 is provided with a check valve 13 that closes the check valve when the turbine reverses rotation to restrict backflow of exhaust gas. Furthermore, an exhaust brake valve 14 is provided between the supercharger 1 and the turbine 4 to close the exhaust passage 3 when the exhaust brake is activated.

Furthermore, this system includes a bypass passage 15 for detouring exhaust gas from the turbine 4 (arrow C in the figure), and a bypass valve 16 for controlling the opening of this bypass passage 15.
An exhaust bypass mechanism 17 is provided. This exhaust bypass mechanism 17 is designed to supply exhaust gas to the turbine 4 when the engine 2 is under a low load, instead of increasing the back pressure in the exhaust passage 3, which is useless for the supercharger 1 and, by extension, the engine 2. In consideration of the fact that a large power loss occurs, the exhaust gas is detoured from the turbine 4 under such operating conditions. As shown in FIG. 5, this bypass valve 16 is operated in response to the engine load, for example, when the governor's easy position is within the set load range and the engine speed is within the set speed range (when the engine speed is controlled by the turbine). It is closed in the drive range D) to interrupt the exhaust bypass and supply exhaust gas to the turbine 4, causing the turbine 4 to drive the engine 2. On the other hand, when it is outside this range (exhaust bypass range E) It is designed to bypass the exhaust gas. If this relationship is shown as a graph, as shown in Fig. 6, in the normal operating ranges D and E of the engine 2 (other than the engine braking range F by the turbine), inside and outside the area surrounded by the set engine speed and engine load. (engine drive range D
The exhaust bypass is switched in the exhaust bypass area E).

In such an engine system, as shown in FIG. 7, each detection signal from the key switch 31, accelerator switch 18, clutch switch 19, exhaust brake switch 20, turbine brake switch 21, rack sensor 22, and engine speed sensor 23 is control unit 24
The input circuit 25, the A/D converter 26, and the waveform shaper 27 are input to the CPU 28, where the ROM 2
9 is stored in the map shown in FIG.
Control signals are output to terminals 2 to 14 and 16. In particular, regarding the above-mentioned exhaust bypass control, the rack sensor 22 and the engine speed sensor 23
and the turbine brake switch 21 are involved, and under the condition that the turbine brake switch 21 is switched, the engine braking range F by the turbine and the normal operating ranges D and E of the engine are switched. Exhaust bypass controls D and E can be switched depending on the detected value.

[Problems to be solved by the invention] By the way, each of the conventional valves 12 to 14, 16,
In particular, the control of the bypass valve 16 of the exhaust bypass mechanism 17 has been performed according to the following flow (see FIGS. 8 and 9).

In the engine operating state after initialization to set the initial value in the control unit 24,
The control unit 24 inputs and reads various detection signals and performs calculations.

First, in the normal operating range, clutch switch 1
If it is detected at 9 that the clutch is engaged, exhaust bypass control is performed based on the engine load and engine speed. At this time, the on-off valve 12 is normally closed, the exhaust brake valve 14 is normally open, and when the turbine 4 is in the normal rotation drive state (region D), the exhaust passage 3 is opened (check valve 13 is open).
Bypass path 15 is closed (bypass valve 16,
Closed) exhaust gas is supplied to the turbine, and on the other hand, when in the exhaust bypass state (area E), the exhaust passage 3 tends to be closed (check valve 13, closed or open), and the bypass passage 15 is opened (bypass Valve 1
6, open), the exhaust gas is allowed to flow around the turbine 4.

Next, the turbine brake switch 21 is turned on.
When activated, the turbine 4 is reversed and enters brake control of the engine 2 (area F). Each valve 1 at this time
Controls 2 to 14 and 16 are such that the on-off valve 12 of the intake introduction passage 11 and the bypass valve 16 of the bypass passage 15 are opened to drive the turbine 4 as a blower, and the check valve 13 of the exhaust passage 3 is closed. It turns out. Further, the exhaust brake valve 14 is opened and closed under the operation of the exhaust brake switch 20.

After that, the turbine brake switch 21
When the OFF operation is performed, the normal exhaust bypass control described above is returned again.

Here, when transitioning from the engine braking area F by the turbine to the engine driving area D by the turbine, the sixth
As shown in the figure, the control was set to move from the engine braking area F, through the exhaust bypass area E in exhaust bypass control in the normal operating area, to the engine drive area D by the turbine (indicated by H in the figure). ). However, such control has the following problems. That is, when it is desired to instantaneously accelerate the engine 2 from the engine braking state, this request is recognized when an instantaneous increase in the engine load and engine speed is detected by the rack sensor 22 and the engine speed sensor 23. 6) is the bypass valve 1
6, conventionally, as shown in FIG. 9, due to the existence of the exhaust bypass region E, the bypass valve 16 is kept open and the bypass passage 15 is kept open for a considerable period of time, as shown in FIG. In the final stage of the exhaust bypass region E, the bypass valve 16 is also closed, the pressure in the exhaust passage 3 increases, and the turbine rotational speed also increases, but until then (indicated by G in the figure) Even if a large amount of fuel is supplied to the engine in response to the acceleration of the engine 2 and the pressure in the exhaust passage 3 increases, the increased pressure is released via the bypass passage 15, causing the pressure in the exhaust passage 3 to increase. There was a problem that a sufficient amount of power could not be obtained, and a "breathing" occurred as the rotation of the turbine 4 increased, resulting in steps in the output response and poor response. That is, when moving from engine braking release to engine control in the normal operating range, turbine operation is always controlled through opening control of the bypass valve 16 in the exhaust bypass region E, so that the turbine operation is controlled in response to increases in exhaust gas temperature and exhaust gas pressure. It was not possible to obtain a smooth rotational rise.

[Means for Solving the Problems] The present invention controls engine operation by controlling the opening of a bypass path that detours exhaust gas from a turbine that recovers exhaust energy to drive the engine and is reversed to brake the engine. The present invention includes a control means for closing the bypass valve for a set time when the amount of rack movement exceeds a set amount when shifting from engine braking to engine driving.

[Function] To describe the function of the present invention, when the engine moves from the engine braking state due to reverse rotation of the turbine to the engine normal operating state, the amount of movement of the rack exceeds the set amount in response to large fluctuations in the engine load. By controlling the bypass valve to be forcibly closed for a set period of time, an appropriate pressure rise in the exhaust passage that supplies exhaust gas to the turbine is ensured, resulting in smooth output for instantaneous engine acceleration control. It's starting to get better.

Embodiment A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

The configuration of the engine system itself is similar to that described in the conventional example (see FIGS. 4 to 7).
The feature of the present invention is that the control unit 24 serving as the control means controls the exhaust bypass when the engine 2 is accelerated from the reverse rotation of the turbine 4 (engine braking region F) to the engine driving region D by the turbine 4. Control, especially control of the bypass valve 16, is performed, and the content of this control is set as a control flow in the CPU 28. The control flow will be explained below with reference to FIGS. 1 to 3. The basic control flow is the same as before.

In the engine operating state after initialization to set the initial value in the control unit 24,
The control unit 24 inputs and reads various detection signals and performs calculations.

First, if it is detected by the clutch switch 19 that the clutch is engaged in engine operating ranges D and E, exhaust bypass control is performed based on the engine load and engine speed. At this time, the on-off valve 12 is normally closed, the exhaust brake valve 14 is normally open, and the turbine 4 is in a normal rotation driving state (region D).
, the exhaust passage 3 is opened (check valve 1
3, open), the bypass passage 15 is closed (bypass valve 16, closed) and exhaust gas is supplied to the turbine 4, and on the other hand, when in the exhaust bypass state (area E), the exhaust passage 3 tends to be closed (reversely). The stop valve 13 is closed or open) and the bypass passage 15 is opened (bypass valve 16 opened) so that the exhaust gas is allowed to flow around the turbine 4.

Next, the turbine brake switch 21 is turned on.
When activated, the turbine 4 is reversed to enter braking control of the engine 2 (area F). Each valve 1 at this time
Controls 2 to 14 and 16 are such that the on-off valve 12 of the intake introduction passage 11 and the bypass valve 16 of the bypass passage 15 are opened to drive the turbine 4 as a blower, and the check valve 13 of the exhaust passage 3 is closed. It turns out. Further, the exhaust brake valve 14 is opened and closed under the operation of the exhaust brake switch 20.
The above is the same as before.

After that, turbine brake switch 21 is turned off.
When activated, the braking state of the engine due to reverse rotation of the turbine is released.

In the present invention, if the rack movement Le exceeds the set amount Ls in the exhaust bypass area E after the turbine brake switch 21 is turned off, it is determined that the engine 2 is in a considerably accelerated state. , control for forcibly closing the bypass valve 16 is executed (second
(see figure). Specifically, after the turbine brake switch 21 is turned OFF, the bypass valve 16 is immediately closed, and a timer in the CPU 28 is started, and this state is maintained for a predetermined time ta (about 0.5 seconds).
This turns the turbine brake switch 21 OFF.
This is set as the waiting time until the next engine control is performed. Thereafter, the rack movement amount Le corresponding to the new control is input and read from the rack sensor 22, and calculation is performed. If this amount of easy movement Le exceeds the set amount Ls, it is determined that the engine 2 is under a considerable acceleration control, and the bypass valve 16 is forcibly turned on unless the turbine brake switch 21 is turned ON again. It will close for the set time tc (see Figure 3). When determining the amount of rack movement, another time tb (approximately 0.1 seconds) is set, and if the set amount is not exceeded within the set time (FLG tb = N) from the timer activation (INC FLG tb), engine 2's Acceleration control is either not performed or is assumed to be small and shifts to normal exhaust bypass control. And once the set time tc has elapsed,
The system is configured to shift to normal exhaust bypass control, that is, engine operation control by controlling the bypass valve 16. Note that each time ta to tc is then cleared (CLR FLG ta to tc). Here, the set time tc refers to the time required from the OFF of the turbine brake switch 21 to the transition to engine drive by the turbine 4 (exhaust pressure in the exhaust passage 3) in terms of engine performance and general engine acceleration control. , time considering the rate of increase in exhaust temperature, etc.), for example,
It is set to about 3 to 5 seconds.

By forcibly cutting off the exhaust bypass control when transitioning from the engine braking state to the engine driving state, the pressure in the exhaust passage 3 increases due to the opening of the bypass valve 16, which conventionally intervened during this transition control. The problem that the rotation increase of the turbine 4 was delayed due to the obstruction, and the output response was not sufficient due to this, was resolved, and as shown by the solid line in Figure 3, an appropriate pressure increase was ensured and a smooth output increase was ensured. can do.

[Effects of the Invention] In summary, the present invention exhibits the following excellent effects.

The bypass valve, which controls the opening of the bypass passage that detours exhaust gas from the turbine that recovers exhaust energy to drive the engine and brakes the reversed engine, controls the engine operation when transitioning from engine braking to engine drive. Since the control means closes the engine for a set time when the amount of movement exceeds the set amount, the engine acceleration state can be easily determined and the exhaust gas can be sent to the turbine even when the engine is accelerated immediately after engine braking. It is possible to appropriately ensure a pressure rise in the supplied exhaust passage, and it is possible to obtain a smooth increase in output in accordance with engine acceleration without interfering with exhaust bypass control that normally corresponds to low engine loads.

[Brief explanation of the drawing]

Fig. 1 is a flowchart adopted for controlling a turbo compound engine showing a preferred embodiment of the present invention, Fig. 2 is a diagram for explaining the opening and closing states of each valve, and Fig. 3 is an engine output and control time. FIG. 4 is a system diagram showing an example of a turbo compound engine to which the present invention is applied, FIG. 5 is a circuit diagram showing the control logic of the bypass valve, and FIG.
Figure 7 shows a control map for the bypass valve, Figure 7 is a circuit diagram showing the control system of a turbo compound engine, Figure 8 is a flowchart showing the conventional control flow, and Figure 9 shows the conventional open/close states of each valve. FIG. In the figure, 2 is an engine, 4 is a turbine, 15 is a bypass passage, 16 is a bypass valve, and 24 is a control unit as a control means.

Claims (1)

[Claims] 1 The bypass valve, which controls engine operation by controlling the opening of the bypass passage that detours exhaust gas from the turbine that recovers exhaust energy and drives the engine and is reversed to brake the engine, is used when switching from engine braking to engine driving. A turbo compound engine characterized by comprising a control means that closes for a set time when the amount of rack movement exceeds a set amount.