JPS62279233A - Variable capacity turbocharger - Google Patents

Abstract

PURPOSE:To improve the fuel consumption performance by controlling a control valve based upon a supercharge pressure and an engine rotary speed while controlling an exhaust bypass valve based only upon the supercharge pressure thereby lowering the engine back pressure under a partial load condition of engine. CONSTITUTION:Under a low engine rotary speed, a supply valve 55 is closed and an atmospheric pressure is applied through a flow path 51 against a negative pressure chamber 28 of a main actuator 24. Although a supercharge pressure is applied through a conduit 38 against a supercharge pressure chamber 30, a control valve 18 is fully closed if the supercharge pressure is low. When the supercharge pressure reaches to a predetermined level, the control valve 18 opens slightly to cause a throttle loss which causes the lowering of turbine efficiency. When the rotary speed reaches to a predetermined level, the supply valve 55 opens to lead the negative pressure through a flow path 50 to the negative pressure chamber 28 so as to fully open the control valve 18. When the supercharge pressure rises furthermore, the pressure in a supercharge pressure chamber 43 of a sub-actuator 40 increases to open an exhaust bypass valve 22.

Description

[Detailed description of the invention] 3. Detailed description of the invention [Industrial application field] The present invention relates to a variable displacement turbocharger.

In particular, the present invention relates to a variable displacement turbocharger suitable for, for example, an automobile engine, which is driven by engine exhaust gas energy.

[Conventional technology]

As a type of variable capacity turbocharger.

The scroll part of the turbine casing is divided into two in the direction of the rotation axis, and a control valve is provided in at least one exhaust gas flow path,
In a low engine speed range, there is a method in which exhaust gas is introduced into only one scroll part to drive the turbine.

In a conventional variable displacement turbocharger of this type, a control valve is controlled by supercharging pressure, as described in Japanese Patent Application Laid-Open No. 60-212623. However, no consideration was given to controlling the turbocharger in a partial load state of the engine.

Furthermore, in the turbocharged engine described in Japanese Patent Application Laid-Open No. 60-173315, the opening degree of the control valve is controlled so that the shaft torque of the engine is maximized depending on the steady state of each operating state of the engine. However, the control mechanism and control circuit are complicated.

No consideration was given to cost.

[Problem that the invention seeks to solve]

In the technology described in the above-mentioned Japanese Patent Application Laid-Open No. 60-212623, the control valve may close when the engine is under partial load, and as a result, the back pressure of the engine increases and the amount of power required to generate unit power is increased. This has the drawback of increasing fuel consumption and reducing the fuel efficiency of the engine.

Furthermore, with the technology described in Japanese Patent Application Laid-Open No. 60-173315, the control valve can be controlled so that the shaft torque is maximized even in a partial load state of the engine, but the control device is equipped with an arithmetic circuit, a memory circuit, a step motor, etc. Because it is configured,
There was a problem that the structure became complicated and the cost increased.

The present invention has been made to solve the problems of the prior art described above, and can improve fuel efficiency by lowering engine back pressure when the engine is under partial load.

The objective is to provide a variable displacement turbocharger with a simple control device structure.

[Means for solving problems]

In order to achieve the above object, a variable capacity turbocharger according to the present invention has a configuration in which a turbine impeller in a turbine casing and a compressor impeller in a compressor casing rotate on the same axis, and °The exhaust gas flow path from the engine is branched into two flow paths, and each of these exhaust gas flow paths is communicated with each scroll portion of the turbine casing, which is divided into two in the rotational axis direction of the turbine impeller. In a variable capacity turbocharger provided with a control valve for opening and closing at least one exhaust gas flow path, an exhaust bypass comprising an exhaust bypass valve capable of communicating an upstream side and a downstream side of the exhaust turbine impeller. means for forming a flow path and controlling the opening degree of the control valve according to the supercharging pressure and engine rotation speed in the discharge pipe of the compressor casing; and means controlling the opening degree of the exhaust bypass valve according to the supercharging pressure. established.

The control circuit is configured to control the boost pressure by the control valve in a range where the engine rotation speed is low, and to fully open the control valve and control the boost pressure by the exhaust bypass valve in a range where the engine rotation speed is high. It was established.

As an additional note, the above purpose is to control the control valve provided in one of the exhaust gas flow paths by boost pressure and engine rotation speed, and to control the exhaust bypass valve only by boost pressure, so that the engine rotation speed This is achieved by controlling the control valve only by the boost pressure in the low speed range, and by fully opening the control valve in the high engine speed range and controlling the boost pressure by the exhaust bypass valve.

[Effect]

In a variable displacement turbocharger that divides the scroll passage in the turbine casing into two, the shape of one of the scroll passages can be selected to achieve optimal turbine flow characteristics for the engine's low-speed rotation range. Compared to a charger, the supercharging pressure is higher in the engine's low speed rotation range, making it possible to improve engine output. As a result, effects such as improved acceleration of the automobile can be obtained. Since the control valve is fully open in the low engine speed range, exhaust gas does not flow into the other scroll flow path. The two scroll passages will be referred to as sub-scroll passages.

As the engine rotation speed increases, the flow rate of exhaust gas increases, so the rotation speed of the turbocharger increases and the supercharging pressure increases beyond the limit value. At this time, the opening degree of the control valve can be increased to control the supercharging pressure to be constant. In this state, most of the exhaust gas flows through the main scroll passage, and a portion passes through the control valve and drives the turbine impeller from the sub-scroll passage. When the engine rotational speed falls into the medium speed range, the turbine flow rate characteristics of the main scroll flow path and the exhaust gas flow rate do not match, and also throttling loss in the control valve is added, resulting in a decrease in turbine efficiency. When the turbine efficiency decreases, the back pressure of the engine increases, and when the back pressure increases, the pumping loss of the engine increases, which causes a decrease in the fuel efficiency of the engine. Therefore, from the viewpoint of fuel efficiency, it is preferable to control the back pressure of the engine to be low.

On the other hand, when the engine is in a high-speed rotation range, the frequency of acceleration of the vehicle is lower than in the low-speed rotation range, and the period of steady driving under partial load is longer. In this state,
Even if the engine output is when the turbocharger is not operating sufficiently, there is no problem with steady driving. Therefore, in the engine.

In a partial load state in a high speed rotation range, a low supercharging pressure is allowed, so if the back pressure of the engine is lowered, fuel efficiency in this range can be improved.

For this reason, in order to sufficiently reduce the back pressure inside the engine and in the high-speed rotation range, even when the control valve is fully opened and the turbine has the maximum flow characteristic, the engine approaches full load. Since this increases the boost pressure, the exhaust bypass valve is used to control the boost pressure so that it does not exceed the limit value. However, the range over which the exhaust bypass valve operates can be narrower than in conventional turbochargers.

In the medium to high speed range, the control system holds the control valve in the fully open state, and the boost pressure is controlled by the exhaust bypass valve, which simplifies the configuration of the control device, resulting in low cost and improved fuel efficiency. It is possible to provide an improved variable displacement turbocharger.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

Here, FIG. 1 is a longitudinal sectional view of a variable displacement turbocharger according to an embodiment of the present invention, and FIG. 2 is a diagram showing changes in valve opening and pressure with respect to engine rotational speed.

In FIG. 1, reference numeral 1 denotes a turbocharger that is operated by exhaust gas from an engine (not shown).

2 is a turbine impeller which is a main component and element of the turbocharger 1; 3 is a compressor impeller which is also a main component of the turbocharger 1; 4 is a rotating shaft;
These turbine blades 112 and compressor blades JE4 are fitted on the same rotating shaft 4, and this rotation @4 is caused by the bearings 5,
It is rotatably supported by 6.

7 is a compressor casing formed to cover the compressor impeller 3; 8 is a diffuser formed within the compressor casing 7; and 9 is a discharge pipe connected to the diffuser 8. This discharge pipe 9 is connected to an air supply pipe of an engine (not shown).

10 is a turbine casing formed so as to cover the turbine impeller 2.

Inside the turbine casing 10 , on the outer periphery of the turbine impeller 2 , two scroll passages divided by a partition wall 11 , namely a main scroll passage 12 and a sub-scroll passage 13 , are arranged around the rotation axis of the turbine impeller 3 . It is formed in the direction.

14 is a main exhaust gas passage communicating with the main scroll passage 12, and this main exhaust gas passage 14 is connected to an exhaust gas collecting pipe 17. Reference numeral 15 denotes a sub-exhaust gas passage communicating with the sub-scroll passage 13, which is connected to the main exhaust gas passage 1.
4 and the sub-exhaust gas flow path 15, a partition wall 16 is formed, and one end of this partition wall 16 is a partition! Connected to 11. The collecting pipe 17 is connected to an exhaust manifold of an engine (not shown). In other words, the exhaust gas flow path from the engine passes through the collecting pipe 17 to the main exhaust gas flow path 1.
4. The auxiliary exhaust gas passage 15 is branched into two passages, and these main and auxiliary exhaust gas passages 14 and 15 are the main and auxiliary scroll passages of the turbine casing, which are divided into two in the rotation axis direction of the turbine impeller 2. It is connected to 12.13.

Reference numeral 18 denotes a control valve that opens and closes at least one of the exhaust gas flow paths, and in the example shown in FIG. 1, the control valve 18 is provided in the auxiliary exhaust gas flow path.

The partition wall 16 is provided with a valve hole 19 for a control valve 18 that communicates the collecting pipe 17 and the sub-exhaust gas flow path 15 .

Reference numeral 20 indicates a discharge flow path of the turbine that opens in the direction of the rotation axis of the turbine impeller 2, and reference numeral 21 indicates the upstream and downstream sides of the turbine impeller 2, that is, the sub-exhaust gas flow path 15 and the discharge flow path 20 of the turbine. This is an exhaust bypass flow path that is formed in a manner that it communicates with the air.

Reference numeral 22 designates an exhaust bypass valve provided in the exhaust bypass flow path 21 , and a valve hole 61 of the exhaust bypass valve 22 is provided in the wall of the turbine casing 10 so that the sub-exhaust gas flow path 15 and the exhaust bypass flow path 21 are connected. It is set up so that it can be communicated with.

What has been explained above is the configuration of the main body of the turbocharger 1, and the primary one is the means for controlling the opening degree of the control valve 18;
The details of the means for controlling the opening degree of the exhaust bypass valve 22 will be explained below.

First, 24 is a main actuator related to a first actuator that opens and closes the control valve 18.

A link 23 is coupled to the control valve 18 and is configured to be driven by a main actuator 24 . The interior of the main actuator 24 is hollow, and is divided into three working chambers by elastic plates 25 and 26 serving as partition walls.

The upper case 27 of the main actuator 24 and the elastic plate 25 form a negative pressure chamber 28, and the elastic plate 25 and the elastic plate 26 form an atmospheric chamber 29. Further, the lower case 31 of the main actuator 24 and the elastic plate 26 form a boost pressure chamber 30.

An actuator rod 32 is attached to the center of the main actuator 24 so as to be movable in the axial direction.

It passes through the lower case 31 and is connected to the link 23.

The portion through which the actuator rod 32 passes through the lower case 31 is kept airtight from the atmosphere. Elastic plates 25 and 26 are fixed to the actuator rod 32,
A spring 33 is provided in the negative pressure chamber 28 so as to be able to generate a downward operating force on the actuator rod 32 via the elastic plate 25 .

The negative pressure chamber 28 is connected by a conduit 34 to a B flow path 36 of a three-way solenoid valve 35, which will be described later. Atmospheric chamber 29
is in communication with the atmosphere through an opening 37. Further, the boost pressure chamber 3o is connected to the discharge pipe 9 of the compressor casing 7 via a conduit 38.

On the other hand, 40 is a second valve that opens and closes the exhaust bypass valve 22.
This is a sub actuator related to the actuator. A link 39 is coupled to the exhaust bypass valve 22, and this link 39 is configured to be driven by the sub actuator 4o. The interior of the sub actuator 4o is hollow, and is divided into two working chambers by one elastic plate 41 serving as a partition wall.

The upper case 44 and the elastic plate 41 of the sub actuator 40 form an atmospheric chamber 42, and the lower case 45 and the elastic plate 41 form a boost pressure chamber 43.

An actuator rod 46 is attached to the center of the sub actuator 40 so as to be movable in the axial direction.

It passes through the upper case 44 and is connected to the link 39.

The other end of the actuator rod 46 is fixed to the elastic plate 41. A spring 47 is provided in the atmospheric chamber 42 so as to generate a downward operating force to the actuator mouth 46 via an elastic plate 41. The atmospheric chamber 42 has an opening 48
communicates with the atmosphere through The boost pressure chamber 43 is connected to the conduit 4
9 to the discharge pipe 9 of the compressor casing 7.

35 is the A flow path 50. B flow path 36. and a C flow path 51.

Inside this three-way solenoid valve 35, an electromagnetic coil 52
．． Movable iron core 53. Spring 54. Supply valve 55 and exhaust valve 5
It consists of 6. A movable core 53 is disposed at the center of the electromagnetic coil 52 so as to be movable in the axial direction, and the movable core 53 is pushed downward by a spring 54 .

The upper and lower end surfaces of the movable core 53 form valve plates for the exhaust valve 56 and the supply valve 55, respectively, and when the movable core 53 is pushed downward by the spring 54, the supply valve 55 is closed and the A flow path 50 is closed. The B flow path 36 and the C flow path 51 become electrically connected. When current flows through the electromagnetic coil 52, the movable iron core 53 closes the exhaust valve 56, and the A flow path 50 and the B flow path 36 become electrically connected.

57 is a rotation speed sensor that detects the rotation speed of the engine, and 58 is an arithmetic circuit that electrically calculates the rotation speed based on the signal from the rotation speed sensor 57. 59 sets the current of the electromagnetic coil 52 to 0 based on the command issued by the arithmetic circuit 58.
This is a solenoid operating circuit that turns N-OFF, and is connected to the electromagnetic coil 52 through an electric wire 60.

The A flow path 5o of the three-way solenoid valve 35 is connected to a pressure section lower than atmospheric pressure (not shown), and the C flow path 5o
1 is open to the atmosphere.

Next, the operation of the variable capacity turbocharger having such a configuration will be explained.

In a low speed range where the engine speed detected by the rotational speed sensor 57 and calculated by the arithmetic circuit 58 is lower than a certain value, the solenoid operating circuit 59 activates the three-way solenoid valve 3.
The current to the electromagnetic coil 52 of No. 5 is cut off, and the electromagnetic coil 52
does not generate magnetic force.

Therefore, the movable core 53 is pushed downward by the spring 54 and the supply valve 55 is closed.

Therefore, the A flow path 5o is blocked, and the B flow path 36 and the C flow path 51 are communicated with each other, so that the pressure in the negative pressure chamber 28 of the main actuator 24 becomes equal to atmospheric pressure through the conduit 34. Further, when the engine is rotating at a low speed, the pressure in the discharge pipe 9 of the compressor, that is, the boost pressure is low, so the pressure in the boost pressure chamber 30 of the main actuator 24 through the conduit 38 is in a low state. Therefore, the downward force of the spring 33 becomes dominant and pushes the actuator rod 32 downward, keeping the control valve 18 in the fully open state via the link 23.

Exhaust gas from the engine is transferred to the collecting pipe 17. Main exhaust gas flow path 14. It passes through the main scroll flow path 12.

It drives the turbine impeller 2 and is discharged to the discharge passage 20 of the turbine. At this time, since the boost pressure in the discharge pipe 9 is low, the pressure in the boost pressure chamber 43 of the sub actuator 40 through the conduit 49 is in a low state. For this reason, the downward force of the spring 47 becomes dominant and pushes the actuator rod 46 downward, causing the exhaust bypass valve 22 to move through the link 39.
keep it fully closed.

The cross-sectional area of the main scroll flow path 12 is determined to have a flow rate characteristic suitable for the engine's low-speed rotation range, so a higher supercharging pressure can be obtained than in the case of a conventional turbocharger, increasing the output in the engine's low-speed rotation range. can be done.

As the engine speed increases, the boost pressure increases, and when the boost pressure reaches a certain value, the pressure in the boost pressure chamber 3o of the main actuator 24 increases, so the actuator rod 32 resists the force of the spring 33. moves upward, and the control valve 18 opens slightly. Therefore, a part of the exhaust gas flows through the valve hole 19. The exhaust gas flows through the sub-exhaust gas passage 15 and passes through the sub-scroll passage 13 to drive the turbine impeller 2 .

At this time, the flow rate of exhaust gas flowing through the sub-scroll passage 13 is small, and the cross-sectional area of the sub-scroll passage 13 is large, so the flow velocity inside the sub-scroll passage 13 is low.
The rotational speed of the turbine impeller 2 does not increase, and the boost pressure is kept at a constant value. In such a state, throttling loss occurs in the control valve 18, resulting in a slight decrease in turbine efficiency.
This is undesirable because engine back pressure increases.

Therefore, when the engine rotation speed detected by the rotation speed sensor 57 and the arithmetic circuit 58 reaches a certain value and enters the high speed range, the solenoid operation circuit 59 is activated and current flows through the electromagnetic coil 52 of the three-way solenoid valve 35. ,
The movable iron core 53 moves upward to close the exhaust valve 56, and the A flow path 50 and the B flow path 36 communicate with each other, and negative pressure is guided to the negative pressure chamber 28 of the main actuator 24 via the conduit 34. Since the atmospheric chamber 29 is maintained at atmospheric pressure, a large upward force acts on the elastic plate 25, and the actuator rod 32 moves upward significantly against the force of the spring 33, causing the link 23 to move upward.
The control valve 18 becomes fully open via the . Exhaust gas enters the sub-exhaust gas passage 15 through the valve hole 19 without resistance, and the sub-scroll passage 13 operates together with the main scroll passage 12, so the turbine characteristics become maximum flow characteristics and the back pressure of the engine is reduced. decreases and improves the engine's fuel efficiency.

Since the control valve 18 is always kept fully open when the engine speed is above a certain value, the maximum flow rate characteristic of the turbine is maintained even under partial load, and the back pressure of the engine can be lowered.

In this range, when the boost pressure in the discharge pipe 9 reaches the above-mentioned constant value, the pressure in the boost pressure chamber 43 of the sub actuator 40 increases through the conduit 49, so that the actuator rod resists the force of the spring 47. 46 moves upward, and the exhaust bypass valve 22 is actuated in the opening direction via the link 39. Therefore.

A portion of the exhaust gas is transferred from the sub-exhaust gas flow path 15 to the valve hole 61,
Passing through the exhaust bypass flow path 21, the turbine discharge flow path 20
flows to

In Figure 2, the horizontal axis shows the engine rotation speed, and the vertical axis shows (
Fig. a) shows the control valve opening, Fig. (b) shows the exhaust bypass valve opening, Fig. (C) shows the boost pressure, and Fig. (d) shows the engine back pressure, and qualitatively shows the changes in each. There is.

As is clear from Fig. 2, when the control valve opening is fully opened, the supercharging pressure tends to decrease in the engine medium speed range, but the minimum flow rate characteristic where only the main scroll passage 12 of the turbine operates, The combination of the maximum flow rate characteristic in which both the main scroll passage 12 and the sub-scroll passage 13 operate and the engine rotational speed with the control valve fully open can reduce the drop in supercharging pressure.

Further, although not shown, hunting in control can be prevented by shifting the control valve switching engine speed when the engine speed increases and when the engine speed decreases.

In this embodiment, since the axial position of the main scroll passage 12 is placed on the compressor side, higher turbine efficiency can be obtained in the low engine speed rotation range.

Further, since the exhaust bypass passage 21 is provided between the sub-exhaust gas passage 15 and the discharge passage 2o of the turbine, the exhaust bypass passage 21 can be formed integrally with the turbine casing 10. Since the main actuator 24 is actuated by spring force and pressure, the structure of the control device is simple. Although we have explained an example in which the actuator rod is moved via a plate and a spring and the valve is opened and closed by a link mechanism, the present invention is not limited to this, and other shapes and mechanisms may be used as long as the same effect is expected. There is no problem in using something.

(Effects of the Invention) As described above, the present invention provides a variable displacement turbocharger with a simple control device structure that can reduce engine back pressure in a partial load state of the engine and improve fuel efficiency. can do.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a variable displacement turbocharger according to an embodiment of the present invention, and FIG. 2 is a diagram showing changes in valve opening and pressure with respect to engine rotational speed. 2...Turbine impeller, 3...Compressor impeller,
4...Rotating shaft, 7...Compressor casing, 9
...Discharge pipe, 10...Turbine casing, 11.
...Partition wall, 12...Main scroll channel, 13...
Sub scroll flow path, 14... Main exhaust gas flow path, 15.
... Sub-exhaust gas flow path, 18... Control valve, 21... Exhaust bypass flow path, 22... Exhaust bypass valve, 24...
・Main actuator. 28... Negative pressure chamber, 30... Boost pressure chamber, 34, 38° 49... Conduit, 35... Three-way solenoid valve, 40
...Subactuator, 43...Supercharging pressure chamber, 52.
...Electromagnetic coil, 53...Movable iron core, 57...Rotational speed sensor, S8°°' calculation circuit, 59-°'So'noid operating circuit, 1.:, 1.2. ',・-1?1 Agent Patent attorney Kosaku Fukuda 3. 'N゛: q, the, vomit) (2 idiots) Figure 2

Claims (1)

[Claims] 1. A turbocharger in which a turbine impeller in a turbine casing and a compressor impeller in a compressor casing rotate on the same axis, and the exhaust gas flow path from the engine is branched into two flow paths. and controlling to communicate each of these exhaust gas flow paths with each scroll portion of a turbine casing divided into two in the rotation axis direction of the turbine impeller, and to open and close at least one of the exhaust gas flow paths. In a variable displacement turbocharger provided with a valve, an upstream side and a downstream side of the exhaust turbine impeller can be communicated with each other,
forming an exhaust bypass flow path including an exhaust bypass valve;
means for controlling the opening degree of the control valve according to the boost pressure and engine rotation speed in the discharge pipe of the compressor casing; and means for controlling the opening degree of the exhaust bypass valve according to the boost pressure; A control circuit is provided so that the boost pressure is controlled by the control valve in a low speed range, and the control valve is fully opened in a high engine speed range, and the boost pressure is controlled by the exhaust bypass valve. A variable capacity turbocharger featuring: 2. In the device described in claim 1, the means for controlling the opening degree of the control valve includes a first actuator that opens and closes the control valve, and a plurality of working chambers of the first actuator, A variable displacement turbocharger that is connected via conduits to the discharge pipe of the compressor casing and a solenoid valve that is controlled according to the engine speed. 3. In the device described in claim 1, the means for controlling the opening degree of the exhaust bypass valve includes a second actuator for opening and closing the exhaust bypass valve;
A variable displacement turbocharger in which the working chamber of the actuator is connected to the discharge pipe of the compressor casing via a conduit.