JPH0456131B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a plurality of turbo superchargers each comprising a turbine driven by engine exhaust gas and a blower connected to the turbine by a rotating shaft, and each of the turbines and the blower is connected to the turbine. The present invention relates to an engine with a turbo supercharger arranged in parallel in an exhaust passage and an intake passage of the engine.

The technical idea of improving engine output performance by boosting intake air pressure using a turbocharger and improving charging efficiency has been well known, and currently it is only possible to improve engine output performance when the engine is running at high speed. First, there is a demand for improving output performance through supercharging even during low-speed operation.

However, it is actually extremely difficult to satisfy the above requirements with a single turbocharger from the viewpoint of turbocharger efficiency, and it is recommended to install multiple turbochargers in parallel. Therefore, technical ideas have been proposed to deal with such requirements (see Japanese Utility Model Application Publication No. 159626/1982 and Japanese Patent Application Publication No. 18117/1983).

Additionally, a turbocharger has the characteristic that the supercharging pressure increases almost in proportion to the increase in engine speed, but increasing the supercharging pressure unnecessarily is not desirable from the standpoint of engine reliability. , Usually, it is necessary to control the maximum boost pressure so that the boost pressure does not rise above a predetermined value. Such control of the maximum boost pressure is necessary to prevent knocking not only in the high speed range but also in the low speed range when supercharging is performed in both the low speed range and the high speed range as described above.

Therefore, in an engine in which multiple turbochargers are installed in parallel as described above, the turbine and blower of each turbocharger must be arranged and connected to the exhaust passage and intake passage of the engine, respectively. In addition, the structure of the intake and exhaust passages becomes complicated, and there are differences in passage resistance between each intake passage and each exhaust passage where each turbocharger is arranged. Engines that use switching turbochargers for high-speed use have problems such as the operating range of each turbocharger being different, making control of boost pressure, especially maximum boost pressure, complicated. There is a problem that has become difficult. That is, as in the case of an engine with a single turbocharger, a pressure sensor is simply installed downstream of the blower to check the boost pressure (commercially available models have a pressure sensor installed directly downstream of the blower). ), the operating range of each turbocharger may be different, or even if the operating range is not different, it may be due to differences in the performance of individual turbochargers, differences in passage resistance, etc. , it becomes difficult to obtain an accurate control signal for the maximum boost pressure actually supplied to the engine.
In order to obtain an effective control signal, it is necessary to correlate the supercharging pressures of each turbocharger, resulting in problems such as complicated control.

The present invention has been made in view of this problem, and includes a plurality of turbo superchargers each including a turbine driven by engine exhaust gas and a blower connected to the turbine by a rotating shaft. Each turbine and blower are arranged in parallel in the exhaust passage and intake passage of the engine, respectively, and when the engine is operating at low speeds, some of the turbo superchargers are used, while when the engine is operating at high speeds, some of the turbo superchargers are used. In a turbocharged engine that uses all turbochargers, the intake air between the engine and the confluence where the intake passages downstream of the blowers of multiple turbochargers arranged in parallel merge. A maximum boost pressure control device that extracts the boost pressure in the passage and, when this boost pressure reaches a set value, responds to the boost pressure and limits the boost pressure to a maximum boost pressure equal to the set value. It is an object of the present invention to provide a boost pressure control device for a turbocharged engine that can effectively and reliably control the maximum boost pressure using a single signal source.

Hereinafter, the present invention will be described in more detail based on illustrated embodiments.

<First Embodiment> In FIG. 1, 1 is an engine, 2 is an intake passage of the engine 1, 3 is an exhaust passage of the engine 1, and 4 is the highest point of the intake passage 2 for measuring the momentary intake air amount of the engine 1. The air flow sensors 5 and 6 are arranged in the upstream part, and the first and second branch intake passages are formed in parallel between the downstream side of the air flow sensor 4 of the intake passage 2 and the upstream side of the throttle valve 7. 1,
Blower 8a, 9b interposed in the middle of the second branch intake passages 5, 6 is interposed in the first and second branch exhaust passages 10, 11 formed by bifurcating the exhaust passage 3 in the middle, respectively. The turbines 8b, 9b have rotating shafts 8c,
These are primary and secondary turbo superchargers connected by 9c.

The above-mentioned primary and secondary turbochargers 8 and 9 are basically equivalent, and the engine 1 with a small intake air amount
During low speed operation, the primary turbo supercharger 8 is used,
During high-speed operation of engine 1 where the intake air amount increases,
The increasing amount of intake air is shared between the primary and secondary turbochargers 8 and 9 to perform supercharging.

For this reason, a check valve 32 is provided downstream of the blower of the second branch passage 6 in which the blower 9a of the secondary turbocharger 9 is provided, and the turbine 9b of the secondary turbocharger 9 is An exhaust control valve 33 is provided upstream of the turbine in the second branch exhaust passage 11, and the operation of the secondary turbocharger 9 is controlled by a control circuit 14, which will be described later.

Further, reference numeral 21 denotes a downstream intake passage 2 between the confluence part 2a of the first and second branch intake passages 5 and 6 and the engine 1.
d and the upstream intake passage 2u downstream of the air flow sensor 4, bypassing the first and second branch intake passages 5 and 6, and 22 is a valve seat provided in the middle of the intake bypass passage 21. 23 is a supercharging pressure control valve that opens and closes; 24 is a diaphragm device for controlling the supercharging pressure control valve 22 in which the supercharging pressure control valve 22 is supported on a diaphragm 24b via a rod 24a;
25 is a positive pressure chamber 24 of the control diaphragm device 24
c is a supercharging pressure introduction passage that introduces the supercharging pressure of the downstream intake passage 2d. The positive pressure chamber 24 is controlled by the diaphragm 24b of the control diaphragm device 24.
Another chamber 24d, which is partitioned off from the air chamber 24c, is formed as an atmospheric chamber communicated with the atmosphere through an atmospheric opening 24e, and a coil spring 24f is compressed in this atmospheric chamber 24d.
The set load of 4f is set according to the maximum boost pressure that is the control target.

As described above, this maximum boost pressure is basically set in consideration of the reliability of the engine 1.

The control circuit 14, as shown in FIG. Exhaust control valve 33
The actuator 34 provided to the exhaust control valve 33 is operated to open the second branch exhaust passage 11.
I'm trying to open it.

When the second branch exhaust passage 11 is opened, the exhaust gas flowing down this passage 11 causes the turbine 9b to
is driven, and the secondary turbo supercharger 9 starts supercharging. When the drive of the secondary turbo supercharger 9 is started,
The check valve 32 is opened, and supercharging pressure provided by the primary turbo supercharger 8 is applied to the downstream intake passage 2d downstream of the merging section 2a where the first and second branch intake passages 5 and 6 merge. A composite pressure of the supercharging pressure provided by the secondary turbocharger 9 is generated.

Therefore, when engine 1 is operating at low speed, 1
The supercharging pressure given by the next turbo supercharger 8 is
Furthermore, during high-speed operation of the engine 1, when the combined boost pressure given by the primary and secondary turbochargers 8 and 9 reaches a predetermined maximum boost pressure, the control diaphragm device 24 By opening the supercharging pressure control valve 22 and opening the intake bypass passage 21, the supercharging pressure can be controlled to be below the maximum supercharging pressure.

That is, in a type of turbocharged engine that uses both the primary and secondary turbochargers 8 and 9, the control diaphragm 24 is activated by a signal from a certain point, regardless of whether it is used alone or in combination. Therefore, even if there is a difference in the passage resistance of the first and second branch intake passages 5 and 6 and the passage resistance of the first and second branch exhaust passages 10 and 11, the excess that is actually supplied to the engine 1 is The maximum boost pressure of air supply can be effectively and accurately controlled.

In the above embodiment, the maximum boost pressure was controlled using the intake bypass passage 21, but as shown by the imaginary line in FIG. 1, the maximum boost pressure was controlled using the exhaust bypass passage 26. You may do so.

That is, the exhaust passage 3 upstream of the exhaust switching valve 12 and the exhaust passages 3, 10, 1 downstream of each turbine 8b, 9b.
A supercharging pressure control valve 27 that opens and closes the exhaust bypass passage 26 that communicates with The downstream intake passage 2 is connected to the boost pressure introduction passage 29.
By introducing the boost pressure of d, when the boost pressure reaches the preset maximum boost pressure, the turbine 8
The supercharging pressure may be controlled by bypassing b or 9b and guiding a part of the exhaust gas to the downstream exhaust passage 3 to lower the exhaust pressure.

As is clear from the above description, according to the present invention, the present invention is effective regardless of differences in the individual characteristics and operating ranges of turbochargers arranged in parallel, as well as differences in intake passage resistance downstream of the blower. , since the boost pressure of the boost air actually supplied to the engine is taken out,
Maximum boost pressure can always be controlled with high precision.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an engine system showing an embodiment of the present invention, and FIG. 2 is a block diagram of the control circuit shown in FIG. 1...engine, 2...intake passage, 5, 6...first,
Second branch intake passage, 2a...merging part, 3...exhaust passage, 10, 11...first and second branch exhaust passage, 8,
9... Primary and secondary turbo superchargers, 8a, 9a... Blower, 8b, 9b... Turbine, 8c, 9c... Rotating shaft, 21... Intake bypass passage, 22... Boost pressure control valve, 24... Control diaphragm Device, 25...supercharging pressure introduction passage.

Claims (1)

[Scope of Claims] 1. A plurality of turbo superchargers each consisting of a turbine driven by engine exhaust gas and a blower connected to the turbine by a rotating shaft, each of the turbines and the blower being connected to the engine exhaust passage. and are arranged in parallel in the intake passage, and when the engine is operating at low speeds, some of the turbo superchargers are used, while when the engine is operating at high speeds, all the turbo superchargers are used. In such a turbocharged engine, the intake passages downstream of each of the blowers are merged, supercharging pressure is taken out from the intake passage between the joining part and the engine, and according to the taken out supercharging pressure, Supercharging of an engine with a turbocharger, characterized in that a maximum supercharging pressure control device is provided, which reduces the supercharging pressure to limit the maximum supercharging pressure when the supercharging pressure is operated and the supercharging pressure is equal to or higher than a set value. Pressure control device.