JPH06307251A - Supercharging pressure controller for turbocharger - Google Patents

Abstract

PURPOSE:To improve control precision of a supercharging pressure, to reduce a turbo lag, and to suppress the increase of a manufacturing cost in a supercharging pressure controller for a turbocharger. CONSTITUTION:An impeller 35, which is rotated and driven by a turbine 20 of a turbo charger, of a compressor 30 is provided with a blade 35b, whose one end edge is overhangingly supported by a disk part 35a. A housing movable part 34 provided with an inner face 34b, whose shape corresponds to that of the other end edge 35c of the blade 35b, is supported by a compressor housing 31 coaxially with the impeller 35 and movably in the axial direction. The axial position of the housing movable part 34 is feedback-controlled by an electronic controller 40 so that a chip clearance (e) between the inner face 34b and the other end edge 35c is set to the predetermined value, which corresponds to the operating condition of the engine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbocharger in which a compressor provided in an intake passage is driven by a turbine provided in an exhaust passage to supercharge an engine, and more particularly to a supercharging pressure control device for the turbocharger.

[0002]

2. Description of the Related Art In an engine equipped with a turbocharger of this type, it is necessary to control the supercharging pressure in order to prevent problems such as knocking due to an excessive rise in the supercharging pressure. In the technology disclosed in the publication, if the boost pressure on the compressor outlet side reaches the set pressure,
A diaphragm actuator opens a control valve that bypasses the exhaust passages in front of and behind the turbine to reduce the turbine output and prevent the boost pressure from becoming excessive. Or install a relief valve in the intake passage on the downstream side of the compressor,
When the boost pressure reaches the set pressure, the intake air is relieved to the outside,
Some have been designed to prevent the boost pressure from becoming excessive.

[0003]

However, in these techniques, the operating points of the bypass control valve and the relief valve are affected by accumulated errors of components such as diaphragms and springs, and feedback control is not performed. However, there is a problem that the supercharging pressure control accuracy is poor. Further, in the former technique, since the bypass control valve controls high-temperature exhaust gas, it is necessary to use a heat-resistant material, which causes a problem of increasing manufacturing cost.

Further, in this type of engine with a turbocharger, a turbo lag (a time delay from the start of acceleration until the supercharger substantially starts operating) occurs when the vehicle is rapidly accelerated from a low-load low-rotation state. Therefore, there is a problem that the rise of the engine output is delayed. This is because even if the exhaust energy increases, the rotation speed of the compressor is delayed due to the inertial mass of the impeller system, etc. Although it solves the problem, there is a problem that such a solution becomes expensive.

The present invention solves each of the problems described above, and provides a turbocharger supercharging pressure control device which has high supercharging pressure control accuracy, can reduce turbo lag, and is small in manufacturing cost increase. The purpose is to do.

[0006]

To this end, the turbocharger supercharging pressure control device according to the present invention, as illustrated in FIGS. 1 to 3, includes a turbine 20 driven by the exhaust energy of an engine, and a turbine 20. The compressor 30 includes an impeller 35 rotatably driven by a turbine and a compressor housing 31, and supplies air to the engine by compressing air. The impeller 35 has a disk portion 35a that cantilevers one side edge of a plurality of blades 35b. In a turbocharger supercharging pressure control device having the following structure, the compressor housing 31 has an inner surface 34b having a shape corresponding to the other end edge 35c of the blade 35b and is axially movable coaxially with the impeller 35. The housing movable part 34 and the housing movable part 34 via a drive device.
By electronically controlling the axial position of the movable part of the housing so that the tip clearance e between the other end edge 35c and the inner surface 34b becomes a predetermined value according to the operating state of the engine. It is characterized by including the device 40.

[0007]

When the engine is in a low load and low rotation state, the electronic control unit 40 controls the axial position of the movable portion 34 of the housing so that the tip clearance e becomes large. Since the pressure decreases, the load on the compressor 30 decreases, and the rotation speed of the impeller 35 increases. If the acceleration is suddenly performed from this state, the electronic control unit 40 feedback-controls the position of the housing movable portion 34 so that the tip clearance e is reduced, whereby the compressor 30 already at a high rotation speed is delayed by almost the time. Since the efficiency is increased without any, a considerable amount of supercharging is immediately started and turbo lag does not occur.

When the output of the engine increases, the electronic control unit 40 feedback-controls the axial position of the movable portion 34 of the housing so that the tip clearance e becomes a predetermined value according to the operating state of the engine. When the output of the engine further increases and the signal indicating the operating state of the engine such as supercharging pressure reaches the set value, the electronic control unit 40 feedback-controls the position of the housing movable portion 34 so that the tip clearance e increases. This prevents the supply air pressure from becoming excessive.

[0009]

As described above, according to the present invention, the supercharging pressure is controlled by feedback-controlling the position of the movable portion of the housing, so that the supercharging pressure can be controlled with high accuracy and low load and low rotation. Even if the vehicle suddenly accelerates from the state, a considerable amount of supercharging does not immediately start and turbo lag does not occur.
In addition, the housing movable part, which is a main control member, is provided on the compressor side, and it is not necessary to use an expensive heat-resistant material or to consider thermal distortion, so that the manufacturing cost can be slightly increased.

[0010]

Embodiments of the present invention will be described below with reference to FIGS. The turbocharger used in the present invention is provided with a turbine 20 and a compressor 30 on both sides of a center housing 10 as shown in FIG.
At both ends of the shaft 11 supported by the center housing 10 via the
And the impeller 35 of the compressor 30 are fixed coaxially. A mechanical seal 13 is provided on the center housing 10 side of the impeller 35, and a labyrinth seal (not shown) on the center housing 10 side of the turbine wheel 25.

The housing 21 of the turbine 20 is fixed to one end of the center housing 10. A scroll 22 formed on the outer peripheral portion of the turbine housing 21 introduces exhaust gas from an engine (neither of which is shown) through an exhaust gas inlet and sends the exhaust gas to a turbine wheel 25 to rotationally drive it. The exhaust gas that has passed through the turbine wheel 25 is discharged from the exhaust gas outlet 23 to the outside.

The housing 31 of the compressor 30 is fixed to the other end of the center housing 10. The impeller 35, which is rotationally driven by the turbine wheel 25 via the shaft 11, compresses the air sucked from the intake air inlet 32 of the compressor housing 31 and sends the compressed air to the diffuser 33. Compressed air in the diffuser 33 is supplied from an intake air outlet to an intake pipe of an engine (none of which is shown).

The impeller 35 is composed of a disk portion 35a coaxially fixed to the shaft 11 by screws, and a large number of blades 35b whose one side edge is integrally cantilevered and supported by the disk portion 35a. The shaft 11 is provided on the inner surface of the compressor housing 31 following the intake air inlet 32.
A supported surface 34a on the outer periphery of the housing movable portion 34 is fitted to the cylindrical supporting surface 31a formed coaxially with the axially slidable surface. The housing movable portion 34 has a curved inner surface 34b having a shape corresponding to the other end edge (free end edge) 35c of the blade 35b. The tip clearance e between the inner surface 34b and the other end edge 35c is the compressor housing 31. On the other hand, it is increased or decreased by moving the housing movable portion 34 in the axial direction.

If the tip clearance e increases,
Air leakage inside the compressor 30 is increased and the compressor efficiency is reduced. Therefore, the tip clearance e
The characteristics of the compressor 30 are changed by changing the. As a result, the supercharging pressure generated at the intake air outlet of the compressor 30 has a characteristic that it decreases as the tip clearance e increases, as shown in FIG. 2A, when the rotational speed of the impeller 35 is constant. This is compressor 3
It means that the load is reduced by 0. Therefore, the rotation speed of the turbine 20 is:
As shown in FIG. 2 (b), the characteristics increase as the tip clearance e increases.

As shown in FIG. 1, the housing movable portion 34.
The axial position of is controlled by the electronic control unit 40 via the step motor 41. The electronic control unit 40 controls the housing movable part 34 based on at least one of the signals indicating the operating state of the engine such as the boost pressure, the throttle opening, the engine rotation speed, the intake air temperature, the cooling water temperature, and the fuel injection amount.
The axial position is set, the housing movable part 34 is positioned at the set position by feedback control via the step motor 41, and the tip clearance e is also set to a value corresponding to this. The setting position of the movable part 34 of the housing is
As an example, when the engine is in a low throttle opening low rotation speed state, the position where the tip clearance e is maximized (the position moved to the leftmost side in FIG. 1) is set, and the throttle opening, its increase speed, and the engine rotation speed increase. The tip clearance e is decreased according to the above, and the tip clearance e is increased so that the boost pressure does not increase any more when the boost pressure increases due to the increase in output and reaches the set value.

The operation of the above embodiment will now be described. When the engine has a low throttle opening and a low rotational speed, the tip clearance e is maximum, which lowers the efficiency of the compressor 30 and exceeds the limit. Since the supply pressure is reduced, the load on the compressor 30 is reduced, and the rotation speed of the impeller 35 is considerably high. In this state, if the acceleration is rapidly performed from the time point T0 in FIG. 3, the electronic control unit 40 sets the position of the housing movable portion 34 to a position where the tip clearance e is reduced and positions it by the feedback control. This positioning is performed with almost no time delay, and since the efficiency of the compressor 30, which has already reached a considerably high rotational speed, increases due to the decrease in the tip clearance e, the supercharging pressure is almost as shown by the broken line A1 in FIG. The engine output starts increasing without time delay and the engine output increases, resulting in a slight turbo lag. Then, when the positioning of the movable portion 34 of the housing by the feedback control is completed, the rise of the supercharging pressure is temporarily delayed.

However, since the exhaust gas amount increases due to the increase in the throttle opening and the increase in the efficiency of the compressor 30, and the rotational speed of the turbine 20 increases after some time delay, the supercharging pressure is indicated by the broken line A2 in FIG. As shown, it rises again and the engine power increases. Then, in the normal operating state, the electronic control unit 40 feedback-controls the axial position of the housing movable portion 34 so that the tip clearance e becomes a predetermined value according to the operating state of the engine, and the supercharged engine output is obtained. Is obtained. The supercharging pressure further increases when the throttle opening is widened, but when the supercharging pressure reaches the set value P1, the electronic control unit 40 feedback-controls the position of the housing movable portion 34 so that the tip clearance e increases. As a result, the boost pressure is maintained at the set value P1 and is prevented from becoming excessive.

On the other hand, in the above-mentioned conventional technique using the bypass control valve or the like, the rotational speed of the turbine 20 increases due to an increase in exhaust gas only due to an increase in the throttle opening, so that the starting point thereof is significantly larger than that of the present invention. Late,
The characteristics are as shown by the solid line B in FIG.

As described above, according to the present embodiment, the turbo lag is small because the supercharging is started with a slight time delay even when the acceleration is rapidly performed from the low throttle opening low rotation speed state. Compared with, turbo lag is greatly reduced. Further, since the supercharging pressure is controlled by feedback-controlling the position of the housing movable portion 34, the supercharging pressure control accuracy becomes high. Moreover, since the housing movable portion 34 is provided on the compressor 30 side, it is not necessary to use an expensive heat-resistant material or to consider thermal distortion, so that the manufacturing cost is slightly increased.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a supercharging pressure control device for a turbocharger according to the present invention.

FIG. 2 is a diagram showing characteristics of a turbocharger with respect to tip clearance.

FIG. 3 is a diagram comparing the characteristics of the supercharging pressure control devices of the present invention and the prior art.

[Explanation of symbols]

20 ... Turbine, 30 ... Compressor, 31 ... Compressor housing, 34 ... Housing movable part, 34b ... Inner surface, 35 ... Impeller, 35a ... Disk part, 35b ... Blade, 35c ... Other edge, 40 ... Electronic control device, 41 ...
Drive device (step motor), e ... Chip clearance.

Claims (1)

[Claims] 1. A turbine driven by exhaust energy of an engine, an impeller rotatingly driven by the turbine and a compressor housing, and a compressor for compressing air and supplying the compressed air to the engine. In a turbocharger supercharging pressure control device in which one side edge of the blade is cantilevered, an internal surface having a shape corresponding to the other end edge of the blade is provided and is axially movable coaxially with the impeller. A movable housing part supported by the compressor housing, and a movable part of the housing is axially moved through a driving device so that a tip clearance between the other end edge and an inner surface has a predetermined value according to an operating state of the engine. Therefore, an electronic control device for feedback-controlling the axial position of the movable part of the housing must be provided. Turbocharger characterized by.