JP2555655B2 - Turbo compound engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention has a turbine that recovers exhaust energy and drives an engine, and a bypass path that bypasses exhaust gas from the turbine and an opening degree of the bypass path. The present invention relates to a turbo compound engine having an exhaust bypass mechanism that is configured by a bypass valve that controls opening and closing and that controls turbine operation and engine operation.

[Prior Art] Generally, in a turbo compound engine, as shown in FIG. 5, in an engine 2 equipped with an exhaust turbo supercharger 1, the exhaust energy used for intake supercharging by the supercharger 1 is transferred to the supercharger 1. Further, the turbine 4 installed in the exhaust passage 3 on the downstream side further collects the shaft rotational force extracted by the turbine 4 and supplies the shaft rotational force to the crankshaft 5 of the engine 2 to achieve high output of the engine 2. Has become.

In this engine system, exhaust gas is diverted from the turbine 4 in addition to a normal exhaust passage 3 that supplies exhaust gas to the turbine 4 in order to drive the engine 4 in the forward direction to drive the engine 2 (arrow A in the figure). Bypass (arrow C in the figure) Bypass
An exhaust bypass mechanism 17 including a valve 15 and a bypass valve 16 that controls the opening of the bypass 15 is provided. The exhaust bypass mechanism 17 supplies exhaust gas to the turbine 4 when the engine 2 has a low load, and rather raises the back pressure in the exhaust passage 3, which is unnecessary for the supercharger 1 and the engine 2. In consideration of causing power loss and deterioration of fuel efficiency, the exhaust gas is diverted from the turbine 4 in such an operating state. As shown in FIG. 6, the bypass valve 16 corresponds to the engine load, for example, when the rack position of the governor is within the set load range and the engine speed is within the set speed range (engine by the turbine). Drive range D)
Is closed to stop the exhaust bypass, supply the exhaust gas to the turbine 4 to drive the engine 2 by the turbine 4, and open the exhaust gas when the exhaust gas is outside the range (exhaust gas bypass region E). It is designed to be bypassed. When this relationship is shown as a graph, as shown in FIG.
In the normal operating regions D and E of the engine 2, the exhaust bypass is switched inside and outside the region surrounded by the set engine speed and the engine load (engine drive region D and exhaust bypass region E).

In such an engine system, as shown in FIG. 8, each detection from the key switch 31, the accelerator switch 18, the clutch switch 19, the exhaust brake switch 20, the turbine brake switch 21, the rack sensor 22, and the engine speed sensor 23 is performed. The signals are input to the CPU 28 via the input circuit 25 of the control unit 24, the A / D converter 26, and the waveform shaper 27, respectively, and are processed by the map shown in FIG. 7 stored in the ROM 29. A control signal is output from the output circuit 30. In particular, regarding the exhaust bypass control described above, the rack sensor 22 and the engine speed sensor
The exhaust bypass controls D and E can be switched depending on the detection values from these.

The engine system shown in FIG. 5 requires a considerable braking ability in the engine system in which the turbine 4 adds the rotational driving force to the engine 2 in addition to the intake supercharging. By driving the turbine 4 for exhaust energy recovery from the engine 2 side in reverse, and reversing its rotation to function as a blower for pump work, the engine braking force is increased in addition to the conventional foot brake and exhaust brake. The configuration is adopted. Between the turbine 4 and the crankshaft 5, a reversing device 6 for rotating the turbine 4 in the forward and reverse directions, and a reduction gear for absorbing rotational inertia (sliding) when switching the forward and reverse rotation of the turbine 4 and adjusting the rotational speed. By interposing the coupling mechanism 7 including 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. In addition, 8 and 9 are respectively the reversing device 6
And a cooling hydraulic system for cooling heat generated by slippage when switching between forward and reverse rotation. Further, in order to use the intake air for pumping work of the turbine 4 which is driven from the engine 2 side and functions as a blower, the exhaust passage 3 is introduced from the intake passage 10 to the outlet side of the turbine 4 (in the figure,
Arrow B) An intake passage 11 is provided. This introduction route 11
Is controlled to be opened and closed by an on-off valve 12 provided on the
The intake air is supplied to the turbine 4 only during engine braking (when the turbine reverses). Further, the exhaust passage 3 has a check valve that closes the exhaust passage 3 at the time of reverse rotation of the turbine to regulate the reverse flow of exhaust gas.
13 are provided. Further, an exhaust brake valve 14 is provided between the supercharger 1 and the turbine 4 for closing the exhaust passage 3 when operating the exhaust brake.

[Problems to be Solved by the Invention] Each valve 12 to 1 in the engine system described above
Opening / closing control of the bypass valves 16 of the exhaust bypass mechanism 17 was performed as follows.

When it is detected by the clutch switch 19 that the clutch is connected in the normal operating regions D and E, the exhaust bypass control is performed based on the engine load and the engine speed. In this case, the on-off valve 12 is normally closed and the exhaust brake valve
14 is normally open, and when the turbine 4 is in the normal rotation drive state (engine drive range D), the exhaust passage 3 is opened (check valve 13,
The open) bypass passage 15 is closed (bypass valve 16, closed) to supply the exhaust gas to the turbine 4, while the exhaust passage 3 tends to be closed when in the exhaust bypass state (exhaust bypass area E) (reverse). The stop valve 13, closed or open) The bypass passage 15 is opened (bypass valve 16, open), so that the exhaust gas bypasses the turbine 4 and flows.

Here, at the time of shifting from the exhaust bypass area E to the engine drive area D by the turbine, regardless of the engine operating state such as the rapid acceleration control of the engine 2, each switch or sensor, especially the rack sensor 22 or the engine rotation speed is used. The bypass valve 16 is to be opened / closed after a lapse of a valve control time corresponding to the calculation time for the detection signal from the number sensor 23 or the bypass valve 16 opening / closing operation time.

However, such control has the following problems. That is, when it is desired to instantly accelerate the engine 2 from the low load state (exhaust gas bypass region E), this request is that the engine load and the instantaneous increase of the engine speed are detected by the rack sensor 22 and the engine speed sensor 23. Although recognized (indicated by J in FIG. 7), since the bypass valve 16 is closed after a considerable control time has elapsed, the engine operating state instantaneously shifts from the exhaust bypass region E to the engine driving region D. Even if the bypass valve 16 is closed, the bypass passage 15 is kept open for a considerable time, and as shown in FIG. 2, the bypass valve 16 is closed at the final stage of the exhaust bypass area E. As a result, the pressure in the exhaust passage 3 also rises and the turbine speed also rises, 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 rises, the increased pressure is released through the bypass passage 15 and the pressure in the exhaust passage 3 is increased. There is a problem in that the response cannot be sufficiently obtained and "rotation" of the rotation of the turbine 4 occurs, which causes a step difference in the output response, resulting in poor response. That is, when the engine control is changed from the low engine load state to the high engine load state, the turbine operation is controlled through the opening state of the bypass valve 16 in the exhaust gas bypass area E for a corresponding time, so that the exhaust gas temperature and the exhaust gas pressure rise. It was not possible to obtain a smooth rotation increase of the turbine according to.

[Means for Solving the Problems] The present invention relates to a turbine that recovers exhaust energy to drive an engine, a bypass valve that is opened to bypass exhaust gas from the turbine, and an engine speed during engine acceleration drives the turbine. In order to do so, the control unit is configured to close the bypass valve in the vicinity of the engine speed range for closing the bypass valve and close the bypass valve when the rack moving speed exceeds the set speed.

[Operation] To describe the operation of the present invention, the engine speed is a speed in the vicinity of the engine drive range during engine acceleration when the engine shifts from a low load state (exhaust bypass region) to a high load state (engine drive region). Based on the assumption that the rack movement speed exceeds the set speed in response to a large change in engine load, the bypass valve is forcibly closed and controlled.
By appropriately securing the pressure increase in the exhaust passage that supplies the exhaust gas to the turbine, a smooth output increase is obtained with respect to instantaneous engine acceleration control.

[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 the same as that described in the conventional example (see FIGS. 5 to 8). The feature of the present invention lies in a control unit as a control means.
Exhaust gas bypass control when the engine 2 is accelerated from the exhaust gas bypass region E to the engine drive region D by the turbine 4 in 24, especially the control of the bypass valve 16, and this control content is the control flow in the CPU 28. Is set as.

Hereinafter, a control flow will be described with reference to FIGS. 1 to 4.

First, in the control unit 24, various detection signals are input and read to perform calculation.

In the normal exhaust bypass control H, if the clutch switch 19 detects that the clutch is engaged, the exhaust bypass control is performed based on the engine load and the 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 (engine drive range D), the exhaust passage 3 is opened (check valve 13, Open bypass passage 15 is closed (bypass valve
16. While the closed exhaust gas is supplied to the turbine 4, the exhaust passage 3 tends to be closed when the exhaust gas is in the exhaust bypass state (exhaust bypass region E) (check valve 13, closed or open).
The bypass passage 15 is opened (bypass valve 16 is open), and the exhaust gas bypasses the turbine 4 to flow.

According to the present invention, the engine 2 has the exhaust bypass area E.
When the moving speed dL / dt of the rack (L is the moving amount of the rack) exceeds the set speed α, it is determined that the engine 2 is in a considerable acceleration state, and the bypass is performed in the exhaust bypass area E. A control for forcibly closing the valve 16 is executed. Specifically, the rack movement amount L corresponding to the new engine control is input and read from the rack sensor 22, and the rack movement speed dL
/ dt is calculated. As shown in FIG. 3, this calculation is performed by detecting the rack movement amount dL at every minute time dt (about 0.1 second). Then, basically, when it is determined that the rack moving speed dL / dt exceeds the set speed α, the bypass valve 16 is forcibly closed from the open state in advance in the exhaust bypass region E. Furthermore, as shown in FIG.
When the engine 2 is accelerated (indicated by K in the figure) while the engine 2 is operated in the vicinity of the switching boundary B of the exhaust bypass control, the exhaust bypass region E often shifts to the engine drive region D. In consideration of the above, the engine speed N is determined by the engine drive range D
The engine 2 also determines whether or not it exists in the rotational speed range near the switching boundary R (Na <N <Nb), which is easy to shift to, and in response to these being satisfied, the engine 2 moves from the exhaust bypass region E to the engine. The bypass valve is assumed to be in a rapid acceleration state where it is easy to shift to the drive range D.
16 is closed and the control of the engine drive range D is performed in advance. Where Na is the lower limit rotation speed near the switching boundary R,
Nb is the upper limit rotation speed near the switching boundary R. In other words, if these determination conditions are not satisfied, it is unlikely that the engine 2 shifts to the engine drive range D, and the bypass valve 16 is not closed, and the bypass valve 16 is closed in a low load state. It is set so as not to cause harmful effects. Further, by performing the control based on the engine speed N, the bypass valve 16 will not be closed when the rack moving speed dL / dt instantaneously exceeds the set speed α in the low engine load range.
It is possible to prevent sudden acceleration feeling.

After that, when it is determined that the rack moving speed dL / dt is lower than the set speed α, the normal exhaust bypass control is returned to.

On the other hand, when the moving speed dL / dt of the rack is less than or equal to the set speed α, the exhaust bypass area E is taken over the normal control time.
From the engine drive range D.

Here, the set speed α is given in consideration of the rate of increase of the exhaust pressure in the exhaust passage 3, the exhaust temperature, etc. in engine performance and general acceleration control of the engine.

As described above, by forcibly closing the bypass valve 16 in advance when shifting from the exhaust bypass region E during acceleration of the engine 2 to the engine drive region D, by opening the bypass valve 16 that was conventionally interposed during this shift control. The rotation increase of the turbine 4 was delayed due to the obstruction of the pressure increase in the exhaust passage 3 and the output response was not sufficient. Therefore, the proper pressure increase was secured as shown by the solid line in FIG. It is possible to secure a smooth output increase.

Of course, instead of detecting the rack, the amount of depression of the accelerator pedal may be detected.

[Effects of the Invention] In summary, according to the present invention, the following excellent effects are exhibited.

The bypass valve that controls the engine operation by collecting exhaust energy and bypassing the exhaust gas from the turbine that drives the engine, and the engine rotation speed during engine acceleration is a rack in the engine speed range where the bypass valve is closed to drive the turbine. When the moving speed of the engine exceeds the set speed, the control means closes it in advance.Therefore, the engine acceleration state is determined by the rack on the assumption of the engine speed that easily shifts to the engine drive range, and the exhaust bypass range is set. Even if the pressure rise in the exhaust passage that supplies the exhaust gas to the turbine is properly secured, a smooth output increase according to the engine acceleration can be obtained without hindering the exhaust bypass control that corresponds to the normal low engine load. You can

[Brief description of drawings]

FIG. 1 is a flow chart used for controlling a turbo compound engine showing an embodiment of the present invention, FIG. 2 is a graph showing the relationship between engine output and control time, and FIG. FIG. 4, FIG. 4 is a diagram showing a control map of a bypass valve, FIG. 5 is a system diagram showing an example of a turbo compound engine in which the present invention is adopted, and FIG. 6 is a circuit diagram showing a control logic of the bypass valve, FIG. 7 is a diagram showing a control map of the bypass valve, and FIG. 8 is a circuit diagram showing a control system of the turbo compound engine. In the figure, 2 is an engine, 4 is a turbine, 16 is a bypass valve, and 24 is a control unit as a control means.

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-61-38127 (JP, A) JP-A-61-169624 (JP, A) JP-A-60-8425 (JP, A) JP-A-58- 106153 (JP, A) Actually opened 61-62248 (JP, U) Actually opened 59-52139 (JP, U)

Claims (1)

(57) [Claims] Claim: What is claimed is: 1. A turbine that recovers exhaust energy to drive an engine, a bypass valve that is opened to bypass exhaust from the turbine, and an engine speed at which the engine speed during engine acceleration closes the bypass valve to drive the turbine. A turbo compound engine having control means for closing a bypass valve when the rack moving speed exceeds a set speed in the vicinity of the range.