JPH01116237A - Turbo compound engine - Google Patents

Abstract

PURPOSE:To smoothly increase a speed in a turbine by providing the turbine, bypass valve controlling a bypass passage to be opened and closed for exhaust from the turbine to detour and a control means opening the bypass valve before an exhaust temperature exceeds a preset value in a transfer to an engine drive by the turbine. CONSTITUTION:When an engine 2 is accelerated in its transfer from a low loaded condition (exhaust bypass region) to a high loaded condition (engine drive region), a bypass valve 16 is controlled so as to be forcedly opened before an exhaust temperature exceeds a preset value. Thus ensuring supply of exhaust, increased in its temperature, to a turbine 4, its proper output increase is ensured.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention has a turbine that recovers exhaust energy to drive an engine, and also has a bypass passage for detouring the exhaust gas from the turbine and an opening degree of the bypass passage. The present invention relates to a turbo compound engine having an exhaust bypass mechanism that controls turbine operation and engine operation by including a bypass valve that controls opening and closing.

[Prior Art] Generally, in a turbo compound engine, as shown in FIG. 4, in an engine 2 equipped with an exhaust turbo supercharger 1, exhaust energy used for intake supercharging by the supercharger 1 is transferred to supercharging n.
It is further recovered by a turbine 4 installed in an exhaust passage 3 on the downstream side of the engine 1, and this turbine 4 supplies a significant amount of shaft rotational force to the crankshaft 5 of the engine 2, thereby achieving high output of the engine 2. It has become.

In this engine system, exhaust gas is supplied to the turbine 4 in order to drive the turbine 4 in normal rotation to drive the engine 2 (arrow A in the figure).In addition to the normal exhaust passage 3, the exhaust gas is bypassed from the turbine 4. bypass path 1 (arrow C in the figure)
5, and a bypass valve 1 that controls the opening of this bypass passage 15.
An exhaust bypass machine #117 consisting of 6 is provided. This exhaust bypass mechanism 17 is configured to supply exhaust gas to the turbine 4 when the engine 2 is under low load.
The back pressure in engine 3 is increased needlessly, the supercharging Ill, and by extension engine 2.
Considering that this may cause unnecessary power loss and deterioration of fuel efficiency, in such operating conditions, the exhaust gas is transferred to the turbine 4.
It is designed to detour from

As shown in FIG. 5, this 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 (when the engine speed is 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) This allows the exhaust to be bypassed. If this relationship is shown as a graph, as shown in Figure 3, in the normal operating range of engine 2, H, inside and outside the area surrounded by the set engine speed and engine load (engine drive area and exhaust bypass area). E)
The exhaust bypass will be switched.

In such an engine system, as shown in FIG. The signals are inputted to the CPU 28 via the input circuit 25, A/D converter 26, and waveform shaper 27 of the control unit 24, respectively, and are inputted to the CPU 28, where they are stored in the ROM.
A control signal is outputted from an output circuit 30 by arithmetic processing based on the map shown in FIG. Especially regarding the above-mentioned exhaust bypass control,
Rack sensor 22 and engine speed sensor 23 are involved,
Based on these detected values, exhaust bypass control is performed and E is switched.

Note that the engine system shown in FIG. 4 requires considerable braking ability in addition to intake supercharging, in which the turbine 4 adds rotational driving force to the engine 2. By driving the turbine 4 for exhaust gas recovery from the engine 2 side and reversing its rotation to function as a blower that performs pump work, it can be used as an engine control in addition to the conventional foot brake and exhaust brake. A configuration that increases power is adopted. Between the turbine 4 and the crankshaft 5, there is provided a reversing device rI16 for rotating the turbine 4 forward and reverse, and a reduction gear that absorbs the rotational inertia (slip) when switching between forward and reverse rotation of the turbine 4 and adjusts the rotation speed. Coupling mechanism 7 consisting of a fluid coupling
By interposing them, forward and reverse rotation of the turbine 4 and mutual transmission of driving force between the crankshaft 5 and the turbine 4 are achieved. Note that 8.9 is a hydraulic system for controlling the reversing device 6 and a cooling hydraulic system for cooling heat generated due to slipping and the like when switching between forward and reverse directions. Also, in the exhaust passage 3, there is an engine 2fl! In order to utilize the intake air for the pumping work of the turbine 4 which is driven by the turbine 4 and functions as a blower, an intake air introduction passage 11 is provided for introducing intake air from the intake passage 10 to the outlet side of the turbine 4 (arrow B in the figure). ing. This introduction passage 11 is controlled to open and close by an on-off valve 12 provided therein, and is configured to supply intake air to the 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.

[Problems to be solved by the invention Answers 12 to 1 regarding the above-mentioned engine system
4, 16, especially the bypass valve 1 of the exhaust bypass mechanism 17
The opening/closing of $1161 for 6 was carried out as follows.

If the clutch switch 19 detects that the clutch is engaged at E in the normal operating range, 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 (engine drive range D), the exhaust passage 3 is opened (the check valve 13, When the bypass passage 15 (open) is closed and the bypass valve 16 is closed, the exhaust gas is supplied to the turbine 4 (closed), and the exhaust passage 3 tends to be closed when it is in the exhaust bypass state (exhaust bypass area E) (closed). The bypass passage 15 is opened (bypass valve 16 , open) and the exhaust gas is allowed to bypass the turbine 4 .

Here, when transitioning from the exhaust bypass region E to the engine drive region by the turbine, the control unit 24 receives detection signals from each switch and sensor regardless of the gas state (pressure, temperature, etc.) in the exhaust passage 3. After the reading and arithmetic processing, the exhaust gas is automatically supplied to the turbine 4 and moved from the exhaust bypass region E to the engine drive region by the turbine. control was set. However, such control has the following problems.

That is, when it is desired to instantaneously accelerate the engine 2, this request is detected and recognized by the rack sensor 22 and the engine speed sensor 23, and the bypass valve 16 is activated. The exhaust gas is supplied to the turbine 4 as the engine is sequentially closed, but under such engine operating conditions, the gas condition in the exhaust passage 3, especially the exhaust temperature, does not necessarily rise to a level that allows the turbine 4 to effectively recover energy. It cannot be said that the turbine 4 is being driven from the engine 2 side, and there is a risk that power loss and fuel efficiency will be worsened.

That is, when moving from the exhaust bypass region E to the engine drive region, control is performed in a constant state to close the bypass valve 16 in response to a delay in the rise in exhaust temperature, so that a sufficient rise in exhaust gas temperature is achieved during subsequent turbine drive. It could not be said that this was ensured, and a smooth increase in rotation of the turbine 4 could not be obtained.

[Means for Solving the Problems] The present invention provides a turbine that recovers exhaust energy and drives between l1, a bypass valve that controls the opening and closing of a bypass path that detours exhaust gas from the turbine, and controls turbine operation; and control means for opening the bypass valve until the exhaust gas temperature exceeds the set temperature when the engine is driven by the turbine.

[Operation] To describe the operation of the present invention, when the engine accelerates to transition from low load state B (exhaust bypass region) to high load state (engine drive region), the bypass is forcibly performed until the exhaust temperature exceeds the set temperature. By controlling the valve to remain open, the supply of heated exhaust gas to the turbine is ensured, thereby ensuring an appropriate increase in the output of the turbine.

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

The basic configuration of the engine system itself is the same as the engine system described above (see FIGS. 4 to 6), and as shown in FIG. Exhaust energy is recovered by a turbine 4 connected to the downstream side of the supercharger 1 and taken out as shaft rotational force, and is supplied via a crankshaft 5 to operate the supercharger 1 at high output.

Here, a temperature sensor 32 for detecting the exhaust gas temperature T is provided in the exhaust passage 3 between the exhaust turbo supercharger 1 and the turbine 4 connected downstream thereof.

This temperature sensor 32 is connected to a control unit 24, which is a control means, and is configured to sequentially output detected temperature signals.

The feature of the present invention is that, based on the detection signal from the temperature sensor 32 that detects the exhaust gas temperature T, the engine 2
The purpose of this control is to control the bypass valve 16 when the engine operation shifts to the engine drive range by accelerating the engine.This control content is controlled by the CPU.
28. Below, the second
The control flow will be explained with reference to the drawings.

The control unit 24 inputs and reads various detection signals, especially in relation to the present invention, engine speed N, rack position, and exhaust temperature T, performs calculations, and performs normal exhaust bypass control. 12 is normally open, the exhaust brake valve 14 is normally closed, and when the turbine 4 is in the normal rotation driving state (engine drive range D), the exhaust passage 3 is opened (the check valve 13 is open) and the bypass passage is closed. (Bypass valve 16
, closed) exhaust gas is supplied to the turbine 4, and on the other hand, when in the exhaust bypass state (region E), the exhaust passage 3 tends to be closed (check valve 13, closed or open), and the bypass passage 15 is opened. (Bypass valve 16, open) The exhaust gas is configured to bypass the turbine 4 and flow.

According to the present invention, when moving from the exhaust bypass region E to the engine drive region, control is executed to forcibly maintain the bypass valve 16 in an open state. Specifically, it is determined whether the engine rotation speed N is within the switching boundary R rotation speed range corresponding to the engine drive range (Na < N < Nb) and whether the rack position is within the switching boundary R rack position. (L>Ls) is determined, and when it is detected that the operating state of the engine 2 has already shifted to the engine drive range (indicated by K in the figure), the exhaust gas temperature T is lower than the set temperature Ta, the bypass valve 16 is maintained in an open state. Note that the check valve 13 is closed at this time. Here, Na is the switching boundary R lower limit rotation speed, Nb is the switching boundary R upper limit rotation speed, and LS is the switching boundary R lower limit rack position.

In this way, when transitioning from the exhaust bypass region E to the engine drive region, the exhaust bypass control is forcibly cut and the bypass valve 16 is maintained in an open state, especially during sudden acceleration. The bypass valve 16 is closed and low-temperature exhaust gas is supplied to the turbine 4, which eliminates the power loss caused by not being able to sufficiently drive the turbine 4. This eliminates the power loss that occurs when the bypass valve 16 is closed, ensuring an appropriate exhaust temperature and ensuring smooth operation of the turbine 4. It is possible to secure a significant increase in output.

Here, the set temperature Ta is set as a temperature necessary to drive the turbine 4 for engine performance and general engine acceleration control.

Thereafter, when it is determined that the exhaust gas temperature T has exceeded the set temperature Ta, normal exhaust bypass control is returned to.

On the other hand, these judgment conditions (Na <N<Nb, L>LS
), the engine 2 is assumed to be in the exhaust bypass region E and the bypass valve 16 is not forcibly operated.
Further, if the exhaust gas temperature T is equal to or higher than the set temperature Ta, normal bypass valve control causes a transition from the exhaust bypass region E to the engine drive region.

It goes without saying that instead of detecting the rack, the amount of depression of the accelerator pedal or the like may be detected.

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

A bypass valve that controls engine operation by controlling the opening of a bypass path that detours exhaust gas from a turbine that recovers exhaust energy and drives the engine is kept open by a control means until the exhaust gas temperature exceeds a set temperature during engine acceleration. Since the temperature is maintained, the temperature of the exhaust gas to be supplied to the turbine can be increased, and an appropriate increase in the output of the turbine can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a turbo compound engine showing a preferred embodiment of the present invention, Fig. 2 is a flow chart adopted for control of the present invention, and Fig. 3 is a graph showing the relationship between engine load and engine speed. , FIG. 4 is a system diagram showing an example of the proposed turbo compound engine, FIG. 5 is a circuit diagram showing the control logic of the bypass valve, and FIG. 6 is a circuit diagram showing the control system of the turbo compound engine. In the figure, 2 is the engine, 4 is the turbine, 15 is the bypass path, 1
6 is a bypass valve, and 24 is a control unit serving as a control means. Patent applicant: Patent attorney representing Isuzu Motors Co., Ltd.
Nobuo Kinuya Figure 2

Claims (1)

[Claims] A turbine that recovers exhaust energy to drive the engine; a bypass valve that controls the opening and closing of a bypass path that detours exhaust gas from the turbine to control turbine operation; and control means for opening the bypass valve until the bypass valve exceeds .