JPS60182316A - Control device of variable displacement turbocharger - Google Patents

Abstract

PURPOSE:To obtain the predetermined supercharging pressure so as to promote an increase of engine torque, by actuating a bypass valve of exhaust gas so as to be closed when the supercharging pressure is controlled by a variable displacement means in a variable displacement turbocharger. CONSTITUTION:A control mechanism 9, actuating a bypass valve in an exhaust- gas bypass mechanism 8 to be closed when a nozzle of a variable displacement mechanism 7 operates opening, maintains the bypass valve to be closed even if the pressure of exhaust gas rises in the upstream of the nozzle. A turbine 5 is rotated at a high speed because the whole quantity of exhaust gas is allowed to flow in the turbine, and its coaxial compressor 6 causes the pressure of intake air to rise to a specified supercharging pressure. The control mechanism 9, if the supercharging pressure exceeds the specified value by increasing an engine speed, actuates the bypass valve to be opened, preventing an engine equipment from damage due to a supercharge.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for a variable displacement turbocharger, and in particular to an improvement of a variable displacement turbocharger ↑l for an automobile engine having an exhaust bypass mechanism.

[Prior Art] Automotive turbocharged engines generally use exhaust energy to supercharge intake air to improve engine torque. An exhaust bypass mechanism is provided to prevent the exhaust gas from rising above the specified value J, and an actuator to which the supercharging pressure is guided opens a bypass valve (swing type thrust gate valve) to bypass the exhaust gas.

On the other hand, a turbocharger equipped with a variable capacity mechanism has been proposed in order to improve performance over a wide range of areas, and by changing the opening degree of a flap valve-type nozzle or a ring-shaped nozzle installed at the turbine inlet, it is possible to improve the performance at all engine speeds. An attempt is made to improve the supercharging pressure (see Japanese Utility Model Application Publication No. 53-50310).

In other words, a variable displacement turbocharger closes the nozzle when the volume is low (low engine speed range) and, conversely, opens the nozzle when the volume is high (high engine speed range). The purpose of this system is to exhibit performance that is suited to the number of rotations used by the engine, thereby achieving a predetermined supercharging pressure.

However, in such a conventional variable displacement turbocharger, when the nozzle is closed to increase boost pressure in the low engine speed range, the exhaust pressure at the turbine inlet rises in the initial stage, causing the predetermined supercharging pressure to rise. There is a problem in that the bypass valve opens before the boost pressure is reached and the boost pressure does not rise to the specified value, resulting in a drop in engine torque.

The reason for this is as follows.

In other words, in order to increase the engine boost pressure, an appropriate pressure difference is required before and after the talbin nozzle, and the turbine obtains its velocity energy from this pressure difference, which rotates the coaxial compressor at high speed and increases the boost pressure. You can get it. in this way,
Since the engine exhaust pressure at the target stage has risen and then the opening is adjusted to the next nozzle opening, the bypass valve upstream of the nozzle is affected by this exhaust pressure. .

Therefore, in the conventional bypass valve, the balance between the supercharging pressure of the actuator that operates the bypass valve and the built-in valve is disrupted by the above-mentioned increase in exhaust pressure, and the valve opens and bypasses the exhaust gas.

As a result, the supercharging pressure drops below the specified value, ie, a so-called slump occurs, resulting in a problem that the torque also decreases.

[Purpose of the Invention] This invention was made by focusing on such conventional problems.It is an object of the present invention to prevent the supercharging pressure of a variable capacity turbocharger from sagging, thereby improving engine torque. The purpose is to

[Structure of the Invention] In order to achieve the above object, the present invention includes a variable displacement mechanism that changes the flow characteristics of a turbine by operating a nozzle, and an exhaust bypass structure that bypasses the turbine and allows exhaust gas to flow through a bypass valve. and a control mechanism that closes the bypass valve when the nozzle is activated.

[Function] When the nozzle of the variable displacement mechanism is operating, the control gI
Since the Im mechanism prevents the bypass valve of the exhaust bypass mechanism from closing, the bypass valve maintains its closed operation even if the exhaust pressure upstream of the nozzle increases. Therefore, the entire amount of exhaust gas flows to the turbine, which rotates at high speed and raises the intake air 3- to a specified supercharging pressure by the coaxial compressor. This prevents a drop in supercharging pressure and, in turn, a drop in torque. When the engine speed eventually rises and the supercharging pressure exceeds a specified value, the bypass valve opens as usual to prevent damage to engine equipment due to overcharging.

[Example] The present invention will be described below based on the drawings. 1 to 4 are diagrams showing an embodiment of the present invention.

First, the overall configuration will be explained with reference to FIG. The engine 1 obtains intake air from the intake pipe 2 and sends the exhaust gas after the engine has finished operating to the exhaust pipe 3.
released into the atmosphere.

The turbocharger 174 includes a turbine 5 and a compressor 6 coaxially, and also includes a variable capacity 1]f47 and an exhaust bypass mechanism 8 at the exhaust inlet of the turbine 5, and these are controlled by a control mechanism 9. There is.

In the second awakening stage 3 concrete example, the intake air is 70 meters 1
It is metered at 1), pressurized by the compressor 6, becomes supercharging pressure 1) at the output r+, is controlled by the throttle valve 12, and is sucked into the engine 1.

Exhaust gas passes from the engine 1 through the exhaust pipe 3, and on the way, it gives energy to the turbine 5 via the nozzle 13 of the variable displacement mechanism 7 before being discharged.

As shown in FIG. 3, the nozzle 13 rotates about a shaft 14 and has a throat 15 having a variable area, corresponding to the exhaust gas entering a spiral scroll 16.

Again in figure M2, the shaft 14 of the nozzle 13 is connected to the lever 17.
and is connected to the diaphragm 20 of the actuator 19 via the rod 18 .

The actuator 19 is provided with a conduit 27 that guides the outlet pressure of the compressor 6 of the intake pipe 2, that is, the supercharging pressure PL],
A throttle 22 is provided in the middle of the pipe, and a relief conduit 23 is branched downstream of the throttle 22, and the other end is connected to the inlet side of the compressor 6. In addition, a spring 24 is installed in the atmospheric chamber 27 of the actuator 19 so that it is directed in Z=1 direction toward the boost pressure Pb.

A solenoid valve 25 is provided in the relief conduit 23 and is duty-controlled by a control unit 26.

The exhaust bypass mechanism 8 has a bypass valve 31 installed in a swing type manner at the entrance of the bypass passage 3o (]1-1-), and is operated by an actuator 34 using a bell crank 32 and an 11-end 33.
The diaphragm 35 is connected to the diaphragm 35. The direflame 35 is urged in the opposite direction of the cut 33 by a spring 36 provided in the atmospheric chamber 28. Further, a conduit 37 for introducing supercharging pressure Pb is connected to the actuator 34, but the pressure outlet is upstream of the electromagnetic valve 25, preferably, as shown in FIG. Then, from the intake port 38 of the intake pipe 2, move to a position 30 where a predetermined pipe line resistance (1 point) is increased.

The actuators 19, 34 and solenoid valve 25 described above.
The four pipes 21, 37, etc. constitute the control mechanism 9 in FIG.

A boost pressure sensor 1t-41 and an emergency relief valve 42 are attached to the intake pipe 2 to detect the boost pressure (intake pipe pressure at the outlet of the air vent) Pb.

Control l ~ roll unit j ~ 26 is mainly microbe [
It is composed of a microcomputer consisting of a setter, a memory, and an interface. The rotational speed No. is received from the throttle valve opening sensor 1 44 with the throttle valve opening as a human input signal -C. Among these signals, the analog signal is input as a digital signal via an A/1) converter. The memory stores programs that control the microprocessor and various data necessary for calculations executed by the microprocessor, and also temporarily stores data imported from the outside. Microbe [1 Setza calculates the fuel N injection amount, injection timing, ignition signal, etc. according to the program and generates an injection signal S1 appropriate for the operating condition.
, outputs the ignition signal Sp, calculates the duty value of the electromagnetic valve 25, and outputs the control signal DM.

Next, the operation of the above embodiment will be explained.

First, the deco eye value DM of the solenoid valve 25 is determined by flowcharts 1 through 1 in FIG. In the figure, []1 to P7 indicate each step of the flowchart (.

At Pl, the engine speed NO and the A/D conversion value of the intake air flow IQa are input, and at P2, the air flow rate per engine revolution is calculated. 1] In step 3, a predetermined duty value is looked up for the engine rotational speed and the air flow f3-rp per rotation. In this table, the dividing points of Ne and -p are finite, and the basic duty value Dv is determined by performing number proportional interpolation calculation on the numerical values between the dividing points.

Roughly speaking, in P4, it is determined whether the basic duty value DM that has been looked up is between the upper limit value D0 and the lower limit value DL in order to prevent the operation delay time of the solenoid valve and the malfunction of the calculation units 1 to 1. ) P if larger than U
Fix DM to the upper limit value with b. Then, the basic duty value pM looked up in P7 is stored, and in accordance with the value in this memory, a timer measuring section (not shown) performs decouty reduction on the solenoid valve, and the result is transmitted to the solenoid valve via the I10 interface. Determine.

Next, the actual operation will be explained with reference to FIGS. 5, 6, and 7.

In FIG. 5, the horizontal axis represents the engine rotational speed Ne, and the vertical axis represents the air flow m T'p per engine rotation. As shown in the figure, the operating line with the throttle valve fully open becomes line F, and the point where the nozzle is fully open and the supercharging pressure is 1"1) 71' specified value, for example, mercury column 375 m/m, becomes the specified value with 81-1 also fully open. The point becomes BU, and the area C between this area is an area where the nozzle opening degree changes (the opening operation increases as the nozzle opens in the direction of the arrow).

Further, the exhaust bypass valve operates in the region between A and the fully open operating line] 3, which are determined before and after the point 3u.

In the above diagram, write the duty values of the solenoid valves with respect to Ne, Tp, and provide them as a table.

This table is predetermined to determine the control leverage value for each engine speed and air flow rate so as to obtain the maximum boost pressure allowed by the engine characteristics and durability and reliability.

FIG. 6 does not show the relationship between the solenoid valve duty value, the actuator positive pressure, and the opening degrees of the nozzle and bypass valve.

The opening degree of the C area of the front) is the C line, and the duty value is the F line (1
00 to 50), the opening degree of the C region is in the range of d line, and the f coating value is in the range of G (50 to O).

That is, in FIG. 2, when the duty value to the solenoid valve 25 is increased, the opening time of the solenoid valve 25 becomes longer, the positive pressure of the actuator 19 decreases, and the force of the spring 24 becomes overwhelming and the nozzle 13 is fully opened. shall be. On the other hand, as the leverage value decreases, the positive pressure increases and the nozzle 13 is fully opened via the iron 18.

During this nozzle operating range F (FIG. 6), the bypass valve is fully open as indicated by dl. Then, the bypass valve gradually listens like d2 and d3.

Figure 7 is a graph showing how the pressure in the conduit to the actuator is lowered (R) depending on the conduit head and each element when the duty values are O%, 50%, and 100%. It decreases almost linearly to the position of
When the duty value is close to O, there is no flow and the positive pressure to the actuator does not escape, so there is almost no decrease.

Therefore, in the operating range (C) of the nozzle 13, the pressure in the conduit 21 decreases due to the on/off operation of the solenoid valve 25, and is applied to the actuator 34 of the bypass valve 31. ,meanwhile,
The force of the spring 28 can cause the bypass valve 31 to close via the l"1 rod 33, and the premature start of opening of the bypass valve 31 due to an increase in exhaust pressure can be easily delayed. .

Thus, the control pressure of the bypass valve 31 is the starting pressure Po
However, since it has decreased by 1 (), it will be kept fully open during this period, and when it reaches Po, it will open to d2.

In addition, in region 1-1, although the actuator positive pressure does not change, the opening operation continues in d3, but this is due to an increase in the bypass flow rate and an increase in the differential pressure before and after the valve. : In this range, no inconvenience occurs because the nozzle control is outside the opening/closing operation range where the nozzle remains fully open.

Figure 8 shows the change in exhaust pressure with respect to the engine speed. It becomes a state of passing. Since the outside of the K range is the operating range of the bypass valve, when the exhaust pressure rises at the X portion of the transient line C, this pressure is applied to the bypass valve, and conventionally the boost pressure increases as shown by the dotted line Y in Figure 9. This causes so-called sagging.

However, in the embodiment of the present invention, the bypass valve 31 is closed by the control mechanism 9 such as the electromagnetic valve 25 and the actuator 34 during the nozzle opening/closing operation, so that the solid line Z in FIG.
As shown in the figure, the boost pressure rises sharply and the slump that occurs in the conventional system disappears. As a result, engine torque is improved,
Good performance can be achieved by opening and closing the nozzle.

The embodiment further includes, as the actuating pressure of the actuator,
When the supercharging pressure is leveled off, the nozzle or bypass valve is opened to try to lower it, which is convenient because the filtering supply pressure is used to control the supercharging pressure.

Another embodiment is shown in FIG. 10. This embodiment is different from that in FIG.
A three-way solenoid valve 45 is installed in the conduit 37 to the tank 34, and is controlled by the control unit 26.
- The difference is that lζ is made as follows.

When the three-way solenoid valve/15 is energized, the conduit 47 of the mouthpiece T-tube 34 communicates with the atmosphere port 46, and when not energized, the conduit 47 communicates with the conduit 21 of the nozzle-side acticoator 19.

In this example, for the activation start pressure po of the bypass valve,
If the duty value of the solenoid valve 25 is set close to 100%, but sufficient margin pressure 1 is not secured until the nozzle opens, the positive pressure of the bypass valve actuator 34 is further lowered to close it. It needs to work and is effective in that case.

According to this embodiment, the bypass valve 31 can be reliably closed by issuing a command from the control unit 26 at the same time as the nozzle operation, energizing the three-way solenoid valve 45, and lowering the pressure of the actuator 34 to atmospheric pressure. .

This is often necessary when the area of the aperture 22 is increased in order to improve the transient characteristics of the nozzle acticoator 19. In particular, when the nozzle opening is narrowed to a small degree, the exhaust pressure of the turbine increases temporarily, and when the engine accelerates, the exhaust pressure increases before the engine starts to increase. This makes it easier for the bypass valve to open.

Therefore, it is necessary to actually close the large differential pressure CMi as in the first embodiment.

[Effects of the Invention] As stated above, the present invention has a structure in which the supercharging pressure is controlled by the variable volume means of the variable volume turbocharger, and the exhaust bypass valve is closed. Since the structure is such that the bypass valve closes even if the turbine pressure is TR, it is possible to TR to the predetermined supercharging pressure, and the effect is that it is possible to increase the engine Herk per unit. is obtained.

In addition, other embodiments can reliably close the bypass valve.
Therefore, there is no need to worry about supercharging pressure sagging. .

Note that the present invention can be applied even if a vacuum is used as the control pressure of the acticoator, and can also be applied in the same way when the bypass valve is used for decoding control.

[Brief explanation of the drawing]

FIG. 1 is an overall view of an embodiment of the present invention, FIG. 2 is a specific configuration diagram of FIG. 1, and FIG. 3 is a sectional view showing the angular displacement mechanism.
FIG. 4 is a flowchart of the control signal program in FIG. 2, FIG. 5 is an explanatory diagram of the table, FIG. Figure 8 shows the engine exhaust pressure performance diagram when the nozzle is operating.
FIG. 9 is a supercharging pressure performance diagram, and FIG. 10 is a specific configuration diagram of another embodiment. (Explanation of symbols representing main parts of the drawing) 1... Engine 2... Intake pipe 3... Exhaust pipe 4... Tarpot 17-Gear 5-
...Turbine 6...Compressor 7...Variable displacement ff1ll structure 8...Exhaust bypass mechanism 9...
Control line drawing 13... Nozzle 19... Actuator 25... Solenoid valve 26... Control unit 30... Bypass passage 31... Bypass valve 1
5- 34... Acticoator 45... Three-way solenoid valve agent Patent attorney Yasu Miyoshi 17- = 16- Figure 7 A-1 Figure 8 Engine rotation speed- Figure 9-, 51- mju gobo engine concave a

Claims (1)

[Claims] A variable capacity mechanism that varies the flow rate characteristics of the turbine by operating a nozzle, an exhaust bypass mechanism that bypasses the turbine and allows exhaust to flow through a bypass valve, and a control mechanism that closes the bypass valve when the nozzle is operated. Control device for variable displacement turbocharger.