JPH052816B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for a variable displacement turbocharger, and particularly to an improvement of a variable displacement turbocharger 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. In this case, supercharging pressure (positive pressure) is specified to prevent engine damage. An exhaust bypass mechanism is provided to prevent the pressure from rising above the specified value, and the actuator to which the supercharging pressure is guided opens the bypass valve (swing type wastegate valve) to bypass the exhaust gas.

On the other hand, a turbocharger equipped with a variable displacement mechanism was proposed in order to improve performance over a wide range.
Flap valve type nozzle installed at the turbine inlet,
Alternatively, the opening degree of the ring-shaped nozzle is changed to improve the boost pressure at all engine speeds (see Utility Model Application Publication No. 53-50310, shown in Figures 1 to 4). Variable displacement turbocharger has low displacement,
(low engine speed range), the nozzle is closed, and conversely, high capacity (high engine speed range), the nozzle is opened, and so on.
The purpose is to exhibit performance that is appropriate for each engine rotational speed, thereby obtaining a predetermined supercharging pressure.

However, in such conventional variable displacement turbochargers, when the nozzle is closed to increase the boost pressure in the low engine speed range, the exhaust pressure at the turbine inlet rises in the initial stage, and the predetermined supercharge is reached. 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 decrease 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 turbine nozzle.The turbine obtains its velocity energy from this pressure difference, and the compressor coaxial with it is rotated at high speed to increase the boost pressure. You can get it. In this way, since the engine exhaust pressure at the turbine inlet has increased 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 system, the balance between the supercharging pressure of the actuator that operates it and the built-in spring 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] The present invention was devised in view of such conventional problems, and it prevents the supercharging pressure from sagging when the variable displacement mechanism is activated, and also removes the exhaust bypass from the variable displacement mechanism operating area. An object of the present invention is to provide an internal combustion engine with a variable capacity feeder that can control smooth connection to a mechanism operating region.

[Summary of the Invention] In order to achieve this object, the present invention provides a variable capacity mechanism that controls the exhaust capacity to the turbine by changing the passage area of the exhaust inlet of the turbine housing, and a variable capacity mechanism that controls the exhaust capacity to the turbine in the low engine speed range. a first driving means configured with a diaphragm constituting a drive unit that drives the variable capacity mechanism and a spring that presses the diaphragm so that the variable capacity mechanism is minimized, and a first drive means that is provided independently of the variable capacity mechanism and bypasses the turbine an exhaust bypass mechanism that controls an exhaust flow rate to the turbine; and a drive section that drives the exhaust bypass mechanism so as to start driving the exhaust bypass mechanism immediately before the exhaust capacity by the variable capacity mechanism reaches a maximum. a diaphragm constituting the diaphragm and a second driving means having a spring that presses the diaphragm, a common pipe line that applies supercharging pressure to both said drive means, and one end communicating with the common pipe line and the other end connected to each driving means. a control valve that controls the operation of both of the drive means by releasing the boost pressure of a boost pressure line consisting of individual pipes to the atmosphere; The configuration includes a control device that controls the.

[Example] Hereinafter, an example of the present invention will be described in detail based on FIGS. 5 to 9.

FIG. 5 is an overall configuration diagram showing an outline of an internal combustion engine with a variable capacity supercharger. According to this, an intake pipe 3 and an exhaust pipe 5 are connected to the engine body 1. A throttle valve 7 is provided in the intake pipe 3 near the engine main body 1, and further upstream thereof (engine main body 1
(on the opposite side) there is a relief valve 9 and an air flow meter 1.
1 is provided. A compressor wheel 13 is disposed in the intake pipe 3 between the air flow meter 11 and the relief valve 9, and a turbine wheel 15 is disposed in the exhaust pipe 5. Further, the compressor wheel 13 and the turbine wheel 15 are interlocked and connected through a connecting shaft 17 to constitute a supercharger main body 19.

In the exhaust pipe 5 upstream of the turbine wheel 15,
A variable capacity mechanism 21 that changes the capacity of exhaust gas flowing into the turbine wheel 15 is provided. As shown in FIG.
A flap valve 27 for changing the flow path area of the inlet portion 25a is swingably attached to the turbine housing 23 by a shaft 29. Furthermore, as shown in FIG. 5, a rod 33 is connected to this shaft 29 via an arm 31 so as to be movable in the vertical direction. This variable capacity mechanism 2
1 is the arm 3 when the rod 33 moves upward.
1, the shaft 29 and the flap valve 27 are respectively
The structure is such that the flow path area of the inlet portion 25a becomes larger by swinging counterclockwise in the figure.

The lower end of the rod 33 is connected to a diaphragm 37 of an actuator 35, which is a first driving means.
This diaphragm 37 causes the actuator 35 to
Inside is an atmospheric pressure chamber 39 on the upper side and a positive pressure chamber 4 on the lower side.
It is divided into 1 and 1.

The diaphragm 37 is biased toward the positive pressure chamber 41 by a spring 43 loaded within the atmospheric pressure chamber 39 . Further, the positive pressure chamber 41 and the intake pipe 3 near the compressor wheel 13, that is, the compressor outlet 45, are connected at one end to a common pipe line 48 in which an orifice 47 is disposed and to the common pipe line 48, and at the other end to the actuator 35. The boost pressure, that is, the control pressure of the actuator 35 is introduced into the positive pressure chamber 41 . Further, the compressor inlet 51 in the intake pipe 3 on the side of the air flow meter 11 of the compressor wheel 13 and the individual pipe line 49 are communicated through a pipe line 53, and a control unit 55 which is a control device to be described later is connected to the compressor inlet 51 and the individual pipe line 49. , OFF ratio control The conduit 53 is controlled by so-called duty control.
A solenoid valve 57 is provided as a control valve for opening and closing. When this solenoid valve 57 is in the ON state, it opens the pipe 53 and releases the supercharging pressure to the atmosphere, and when it is in the OFF state, the pipe 53 is opened and the supercharging pressure is released to the atmosphere.
Block 3.

By controlling the solenoid valve 57 to turn on, the control pressure of the actuator 35 decreases, and the actuator 35
The variable capacity mechanism 21 is driven by the spring force of the spring 43 so that the exhaust capacity is minimized in the low rotation range.

Furthermore, an exhaust bypass mechanism 61 having an exhaust bypass passage 59 that bypasses the turbine wheel 15 is disposed in the exhaust pipe 5 between the engine body 1 and the variable capacity mechanism 21 . The exhaust bypass mechanism 61 has a rod 67 connected to an exhaust bypass valve 63 for opening and closing the exhaust bypass passage 59 via a link mechanism 65. That is, Rod 67
5, the exhaust bypass valve 63 moves in the direction of opening the exhaust bypass passage 59. Furthermore, the lower end of the rod 67
This diaphragm 71 divides the inside of the actuator 69 into an atmospheric pressure chamber 73 on its upper side and a positive pressure chamber 75 on its lower side. In this atmospheric pressure chamber 73, there is a diaphragm 7.
A spring 77 is loaded to bias 1 toward the positive pressure chamber 75 side. Furthermore, this positive pressure chamber 75 communicates with the common pipe line 48 via an individual pipe line 79 which is connected to the common pipe line 48 at one end and to the actuator 69 at the other end, and the control pressure of the actuator 69 is introduced. be done. Therefore, like the positive pressure chamber 41 of the actuator 35, this positive pressure chamber 75 is in communication with the compressor outlet 45, so that the pressure of the compressor 45 controlled by the operation of the solenoid valve 57 can be transferred to the positive pressure chamber 75. In other words, supercharging pressure is applied.

The actuator 69 is connected to the solenoid valve 57.
The spring constant of the spring 77 is set so that the exhaust bypass mechanism 61 starts to be driven immediately before the exhaust capacity by the variable capacity mechanism 21 reaches its maximum with respect to the actuator control pressure by ON/OFF control.

The common pipeline 48 and the individual pipelines 49 and 79 constitute a boost pressure pipeline, and the solenoid valve 57 opens and closes the pipeline 53 to control the boost pressure in the boost pressure pipeline. The actuator control pressure is released to the atmosphere to control the operation of both actuators 35 and 69.

Further, the throttle valve 7 has a throttle valve opening detection means 81 for detecting the opening of the throttle valve 7, and the engine body 1 has a rotation speed detection means 83 for detecting the engine rotation speed Ne and a knock detection means 81 for detecting the opening of the throttle valve 7. Means 85 are provided respectively. Signals from each of these detection means 81, 83, and 85 are input to the control unit 55. In addition, the air flow rate Q _A measured by the air flow meter 11
The information is also input to the control unit 55.

This control unit 55 mainly consists of a microcomputer consisting of a microprocessor, memory, and interface.
Each of the detection means 81, 8 is connected to this interface.
3, 85 and the air flow meter 11 are input. Among these signals, analog signals are input as digital signals via an A/D converter (not shown). The memory stores programs for controlling the microprocessor and various data necessary for operations executed by the microprocessor, and also temporarily stores data imported from outside. The microprocessor calculates the fuel injection amount, injection timing, ignition timing, etc. according to the above program and outputs an injection signal S I and an ignition signal SP appropriate for the operating condition, and also outputs an injection signal S I and an ignition signal SP suitable for the operating condition, and also outputs an injection signal S _I and an ignition signal _SP suitable for the operating condition, and also outputs an injection signal S I and an ignition signal SP suitable for the operating condition. It calculates the duty value of 57 and outputs the control signal S _C from the interface. The control unit 55 functions as a control device that controls the variable capacity mechanism 21 and the exhaust bypass mechanism 61 via the solenoid valve 57.

Next, the action will be explained.

First, when the internal combustion engine starts operating, exhaust gas discharged from the engine main body 1 reaches the turbine wheel 15 via the exhaust pipe 5, and the supercharger main body 19 starts operating. By increasing the pressure at the compressor outlet 45 where the supercharger main body 19 operates, that is, the supercharging pressure actuator control pressure, the pressure is increased to each actuator 35,
The pressure in the positive pressure chambers 41 and 75 of 69 also increases. The control unit 55, to which each signal is input from the air flow meter 11, the throttle valve opening detection means 81, the rotation speed detection means 83, and the knock detection means 85, performs duty control on the solenoid valve 57 to By adjusting the pressure in the positive pressure chambers 41 and 75, the control unit 55, which is a control device, controls the variable capacity mechanism 21 via the solenoid valve 57.
and the exhaust bypass mechanism 61 in relation to each other.

For example, when the duty ratio is small, in other words, the OFF state of the solenoid valve 57 is long,
When the ON state is short, the cutoff time for the pipe line 53 becomes long, and the pressure in each positive pressure chamber 41, 75 increases. When the pressure in each positive pressure chamber 41, 75 increases in this way, the diaphragm 37, 71 causes the spring 4
3 and 77, and as the rod 33 on the variable capacity mechanism 21 side rises, the arm 31, the shaft 29 in FIG. 6, and the flap valve 27 swing counterclockwise in FIG. and scroll 25
The flow path area of the inlet portion 25a is increased. Also,
When the rod 67 on the exhaust bypass mechanism 61 side rises, the exhaust bypass valve 63 opens the exhaust bypass passage 59 via the link mechanism 65, thereby reducing the exhaust capacity to the turbine wheel 15. The opening timing and opening amount of the flap valve 27 of the variable capacity mechanism 21 and the exhaust bypass valve 63 of the exhaust bypass mechanism 61 are determined by the pressure at the compressor outlet 45, that is, the supercharging pressure, depending on each operating state. Determined by duty control for the solenoid valve 57 after control calculations are performed by the control unit 55 to which signals from the air flow meter 11, throttle valve opening detection means 81, rotation speed detection means 83, and knock detection means 85 are input. be done. Therefore,
Since boost pressure is always maintained at the optimum level, torque is improved over the entire operating range.

Next, the control calculations of the control unit 55 will be explained based on the flowchart shown in FIG. In the figure, P ₁ to _{P 7} indicate each step of the flowchart.

For example, this control calculation is performed once per engine revolution.
It is executed once every time or at a certain period of time. First, when the program starts, the JOB control section determines the JOB execution procedure, and then the solenoid valve 5
A duty value calculation routine of No. 7 is executed.
In this calculation routine, first, in step _P1 , the A/D converted values of the engine rotation speed Ne and intake air flow rate _QA are input, and in the next step _P2 , the air flow rate T _P to the engine per engine rotation is calculated. be done. Furthermore, in the next step _P3 , a predetermined basic duty value D _M is looked up for the engine speed Ne and the air flow rate T _P per engine revolution.

In this control table, the division points of the engine speed Ne and the air flow rate per engine revolution T _P are finite, so by performing comparative interpolation calculations for values other than these division points, the basic duty value D _M is determined.

Further, the duty value of the solenoid valve 57 is provided with an upper limit Du and a lower limit _DL , as shown in FIG.
This is to prevent malfunctions caused by 0% and 100% overlap in the on-duty time calculation section in the control unit 55, and the basic duty value that has been looked up is
It is determined in the next step _P4 whether _DM is between the upper limit Du and the lower limit _DL . Then, when the basic duty value D _M is larger than the upper limit Du, the basic duty value D _M is set to the upper limit Du in step _P5 .
If the basic duty value _DM is smaller than the lower limit _DL , the basic duty value _DM is set to the lower limit _DL in step _P6 .

In this way, the basic duty value _DM that has been looked up is stored in the memory of the control unit 55 in the next step _P7 , and furthermore, in accordance with the value stored in this memory, a timer measuring section (not shown) controls the solenoid valve. 57 is calculated, and the calculated value is sent to the solenoid valve 57 via the interface of the control unit 55.

Next, the actual control table will be explained based on Fig. 8. Here, the horizontal axis shows the engine speed Ne.
The air flow rate T _P per engine revolution is plotted on the vertical axis, and the operating line when the throttle valve 7 is fully open is E.
The line in FIG. 6 where the flap valve 27 is fully closed (minimum throat area) with respect to the inlet portion 25a of the scroll 25 and the pressure at the compressor outlet 45, that is, the supercharging pressure, reaches a specified value, for example, 375 mmHg of mercury column, is B _L. Yes, and the flap valve 27 is fully open (maximum throat area) and the boost pressure is at the specified value, for example, mercury column.
The line at 375mmHg is Bu. This line B _L and line Bu
The area F between the two is the area where the opening degree of the flap valve 27 changes, and the flap valve 27 increases the flow path area of the inlet portion 25a of the scroll 25 as it moves in the direction of the arrow in the figure. It will open and operate.

In addition, the exhaust bypass valve 63 begins to open from line G shown by a broken line, which is set just before the line Bu where the flap valve 27 is fully opened, and when the throttle valve 7 is fully opened, the operating line E
It operates in the region H between. That is, between the operating range F of the variable capacity mechanism 21 and the operating range H of the exhaust bypass mechanism 61, there is a slight overlap J where these two overlap. In this embodiment, a table containing the control values of the F section and a table containing the control values of the H section with respect to the engine rotational speed Ne and the air flow rate T _P per engine rotation are provided in one table. This table value is set at the engine speed to achieve the maximum boost pressure allowed by engine characteristics, durability, reliability, etc.
Ne and the air flow rate T _P per engine revolution are predetermined.

FIG. 9 shows the duty value of the solenoid valve 57, the control pressure of the actuator 35 for driving the variable capacity mechanism, and the actuator 69 for driving the exhaust bypass mechanism, that is, the respective pressures in the positive pressure chambers 41 and 75, and the opening of the flap valve 27. The solid line shows the relationship between the duty value and the actuator control pressure, the solid line shows the duty value and the flap valve opening, and the broken line shows the relationship between the duty value and the opening of the exhaust bypass valve 63. represents the relationship between The range of duty K in the figure corresponds to the duty value used in section F of FIG. 9, while the range of duty L corresponds to the duty value used in section H of FIG. Note that a and b in the figure indicate the actuator use control pressure for driving the exhaust bypass mechanism and the actuator use control pressure for driving the variable displacement mechanism, respectively.

As can be seen from FIG. 9, by selecting the spring constants of the springs 43 and 77 of the actuators 35 and 69 in accordance with the control pressure used by the actuators, the flap valve 27 and the exhaust bypass valve 63 can be operated. The operation can be performed smoothly and in a coordinated manner. In this case, each spring 4
The spring constants 3 and 77 are selected so that the exhaust bypass valve 63 begins to open immediately before the flap valve 27 fully opens, and the operating ranges F and H of the two have an overlapping portion J. Therefore, even if there are variations in the operating characteristics of the variable capacity mechanism 21 and the exhaust bypass mechanism 61 due to individual differences, that is, variations in the shape of the scroll 25 and variations in the characteristics of the springs 43 and 77, the overlap portion J can compensate for this. Therefore, when controlling the switching from the variable capacity mechanism 21 to the exhaust bypass mechanism 61, due to the delay in the operation of the exhaust bypass mechanism 61, even though the variable capacity mechanism 21 is displaced to the maximum exhaust capacity position, the exhaust bypass mechanism 61 is still activated. It is possible to reliably prevent a situation in which the valve continues to close and not start operation, that is, a situation in which the supercharging pressure suddenly increases beyond the set value. Furthermore, since both the independently provided variable capacity mechanism 21 and the exhaust bypass mechanism 61 are controlled via a single common pipe line 48 and a single solenoid valve 57, the operating characteristics of the two mechanisms can be adjusted. Timing can be controlled with high precision. The opening of the exhaust bypass mechanism 61 is reliably restricted in the operating range of the variable capacity mechanism 21.

In this way, it is possible to prevent the supercharging pressure from sagging.

Furthermore, since the pressure at the compressor outlet 45, that is, the supercharging pressure, is used as the actuator drive pressure, when this supercharging pressure attempts to increase, the solenoid valve 5
Since the actuator control pressure increases even with the same duty value of 7, both or one of the flap valve 27 and the exhaust bypass valve 63 tries to open.
There will be so-called feedback.

By adjusting the duty value for operating the solenoid valve 57 based on this feedback, desired boost pressure characteristics can be obtained.

Effects of the Invention As described above, according to the present invention, the variable capacity mechanism that controls the exhaust capacity to the turbine by changing the passage area of the exhaust inlet of the turbine housing is configured such that the exhaust capacity is minimized in the low engine speed range. In this way, a first driving means is provided with a spring that presses a diaphragm and a die-throwing diaphragm that constitute a drive unit that drives the variable capacity mechanism, and the turbine is bypassed immediately before the exhaust capacity by the variable capacity mechanism reaches its maximum. a second driving means for setting a diaphragm and a spring that presses the diaphragm, which constitute a driving section that drives the exhaust bypass mechanism, so as to start driving the exhaust bypass mechanism that controls the exhaust capacity to the turbine by What is
It is controlled based on the engine speed and air flow rate using the control pressure (supercharging pressure) controlled by the control valve as the driving source, and as a result, the capacity of the variable capacity mechanism changes from the minimum state to the increasing direction, and the capacity increases. The operation of the variable capacity mechanism and the exhaust bypass mechanism can be smoothly linked, such that the operation of the exhaust bypass mechanism is started just before the amount reaches the maximum, and the exhaust bypass amount changes in an increasing direction.

Moreover, in this case, the drive elements such as springs and diaphragms that set the operation of each drive means start driving the exhaust bypass mechanism just before the exhaust capacity by the variable capacity mechanism reaches its maximum, and the operating ranges of the two overlap each other. Therefore, even if there are variations in the operating characteristics of the variable capacity mechanism and exhaust bypass mechanism due to individual differences, such as variations in the shape of the turbine housing or variations in spring characteristics, the overlap part will absorb this. However, when controlling the switching from the variable capacity mechanism to the exhaust bypass mechanism, due to the delay in the operation of the bypass mechanism, even though the variable capacity mechanism is displaced to the position of maximum exhaust capacity, the bypass mechanism still remains closed and does not start operating. Such a situation, that is, a sudden increase in supercharging pressure exceeding a set value, can be reliably prevented. In addition, since both the independently provided variable capacity mechanism and bypass mechanism are controlled via a single common pipeline and a single control valve, the operating characteristics and timing of the two mechanisms can be controlled with precision. can do.

[Brief explanation of the drawing]

Figures 1 to 4 relate to conventional examples, with Figure 1 being a sectional view of the variable capacity mechanism, Figure 2 being a block diagram showing the control for the variable capacity mechanism in Figure 1, and Figure 3 being the position of each accelerator rack. 4 is an explanatory diagram showing the relationship between the engine rotation speed and the opening degree of the movable member during acceleration, and FIGS. 5 to 9 are explanatory diagrams showing the relationship between the engine rotation speed and the opening degree of the movable member during acceleration 5 is an overall configuration diagram, FIG. 6 is a sectional view of a scroll portion equipped with a flap valve, FIG. 7 is a flowchart, and FIG. 8 is an engine diagram for explaining a control table. An explanatory diagram showing the relationship between the rotation speed and the air flow rate per engine revolution, Fig. 9 shows the relationship between the duty ratio for controlling the solenoid valve, the actuator control pressure, the flap valve opening degree, and the exhaust bypass valve opening degree. It is an explanatory diagram showing a relationship. Explanation of symbols representing main parts of the drawings, 15...
Turbine wheel (turbine), 21... variable capacity mechanism, 27... flap valve, 23... turbine housing, 35... actuator (first drive means),
37...Diaphragm, 43...Spring, 48...
Common pipe line (supercharging pressure pipe line), 49, 79...Individual pipe line (supercharging pressure pipe line), 61...Exhaust bypass mechanism, 63...
Exhaust bypass valve, 55...control unit (control device), 57...electromagnetic valve (control valve), 69...actuator (second driving means), 71...diaphragm, 77...spring.

Claims (1)

[Claims] 1. A variable capacity mechanism that controls the exhaust capacity to the turbine by changing the passage area of the exhaust inlet of the turbine housing, and a drive unit that drives the variable capacity mechanism so that the exhaust capacity is minimized in a low engine speed range. a first driving means configured with a diaphragm and a spring that presses the diaphragm, and an exhaust bypass mechanism that is provided independently of the variable capacity mechanism and controls the exhaust flow rate to the turbine by bypassing the turbine. , a second diaphragm and a spring that presses the diaphragm forming a drive unit that drives the exhaust bypass mechanism are set so that the exhaust bypass mechanism starts driving immediately before the exhaust capacity by the variable capacity mechanism reaches a maximum; The supercharging pressure of a supercharging pressure conduit consisting of a driving means, a common conduit that applies supercharging pressure to both said driving means, and an individual conduit whose one end communicates with the common conduit and whose other end is connected to each of the driving means. A variable capacity variable capacity device characterized by comprising a control valve that is open to the atmosphere and controls the operation of both of the drive means, and a control device that controls the control valve based on engine rotation speed and air flow rate to the engine. Internal combustion engine with supercharger.