JPH0953470A - Exhaust brake device of diesel engine with turbocharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the braking force in a medium low speed rotation region while avoiding the abnormal behavior which is a matter of concern in a high speed rotation region. SOLUTION: An exhaust brake valve 4 is disposed in an exhaust passage 2 on the downstream side of a turbine 3a of a turbocharger 3. A waste gate valve 6 is disposed in an exhaust by-pass passage 5 extending from an exhaust passage 3 on the upstream side of the turbine 3a to the exhaust passage 2 on the downstream side of the exhaust brake valve 4. A controller 14 controls the opening and closing of the exhaust brake valve 4 and the waste gate valve 6 in response to the operating condition of an engine, whereby while the closing degree of the exhaust passage 2 when the exhaust brake is operated in the medium low speed rotation region of the engine 1 is made high, the closing degree of the exhaust passage 2 when the exhaust brake is operated in the high speed rotation region of the engine is made low.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust brake device for a turbocharged diesel engine, and more particularly,
The present invention relates to an exhaust brake device capable of increasing a braking force in a normal rotation range.

[0002]

2. Description of the Related Art When applying an exhaust brake device to a diesel engine equipped with a turbocharger, the conventional brake system shown in FIG.
As shown in FIG. 3, the turbine 3a of the turbocharger 3 is provided in the exhaust passage 2 of the diesel engine 1, and the exhaust brake valve 4 is provided in the exhaust passage 2 downstream of the turbine 3a. Then, the exhaust passage 2 upstream of the turbine 3a
The downstream end of the exhaust bypass passage 5 branched from the above is joined to the exhaust passage 2 upstream of the exhaust brake valve 4 downstream of the turbine 3a, and then the waste gate valve 6 is attached to the exhaust bypass passage 5.

Reference numeral 7 is a controller, 8 is an air tank, 9 is an electromagnetic valve for controlling the exhaust brake, 10 is an air cylinder provided as an actuator of the exhaust brake valve 4, 11
Is an intake passage provided with the compressor 3b of the turbocharger 3, 12 is a boost pressure sensor, 13 is a pressure reducing valve, 14 is a solenoid valve for controlling a waste gate valve, and 15 is an air tank 8 via the pressure reducing valve 13 and the solenoid valve 14. It is a connected diaphragm actuator that opens and closes the waste gate valve 6.

The controller 7 outputs the rotation signal, load signal and boost pressure sensor 1 of the diesel engine 1 output from a rotation sensor and a load sensor (not shown).
2 is supplied as control information, and the exhaust brake valve 4 and the waste gate valve 6 are controlled to open and close based on these control information.

In such a conventional exhaust brake device, when the exhaust brake valve 4 is closed based on the control signal output from the controller 7, the exhaust passage 2 is opened.
Is closed and the pressure in the exhaust port rises, so that the effectiveness of engine braking is increased and braking force is obtained. Moreover, the magnitude of such a braking force increases as the pressure in the exhaust port increases, and the pressure in the exhaust port increases as the rotational speed of the diesel engine 1 increases. Becomes larger as the degree of sealing of the exhaust passage 2 by the exhaust brake valve 4 becomes higher.

Therefore, in the case where the degree of sealing of the exhaust passage 2 by the exhaust brake valve 4 is increased in order to increase the braking force in the medium-low speed rotation range which is the normal rotation range of the diesel engine 1, it is shown by a chain line in FIG. As described above, the pressure in the exhaust port in the high-speed rotation range may become higher than the abnormal behavior limit of the exhaust valve, which may cause abnormal vibration of the exhaust valve. Further, when the degree of sealing of the exhaust passage 2 by the exhaust brake valve 4 is lowered in order to keep the pressure in the exhaust port at the time of operation of the exhaust brake during operation in the high speed range below the abnormal behavior limit of the exhaust valve, As indicated by the chain double-dashed line, the pressure in the exhaust port in the medium to low speed rotation range was also low, and there was the problem that sufficient braking force could not be obtained.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to avoid the abnormal behavior of the exhaust valve, which is a concern in the high speed rotation range, and to increase the braking force in the middle and low speed rotation range. An object of the present invention is to provide an exhaust brake device for a diesel engine with a turbocharger that can be used.

[0008]

In order to solve the above problems, the present invention provides an exhaust brake valve in an exhaust passage downstream of a turbine of a turbocharger while branching from an exhaust passage upstream of the turbine. An exhaust bypass passage is provided that joins the exhaust passage downstream of the valve. A waste gate valve is attached to the exhaust bypass passage, and a controller for opening / closing the exhaust brake valve and the waste gate valve in response to an operating state of the diesel engine is provided.

According to the present invention, a first bypass passage branched from an exhaust passage upstream of the turbine and joined to an exhaust passage downstream of the exhaust brake valve, and a first bypass passage branched from the exhaust passage upstream of the turbine and downstream of the turbine. The exhaust bypass passage is configured by a second bypass passage that joins the exhaust passage upstream of the exhaust brake valve, and a waste gate valve is provided in each of the bypass passages.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a first embodiment of an exhaust brake device for a diesel engine with a turbocharger according to the present invention.
It is a system diagram which shows embodiment. The parts having the same functions as those of the conventional example shown in FIG. 7 are designated by the same reference numerals.

In FIG. 1, an exhaust brake valve 4 is provided in an exhaust passage 2 downstream of a turbine 3a of a turbocharger 3.
Is provided. Further, an exhaust bypass passage 5 that branches from the exhaust passage 2 upstream of the turbine 3a and joins the exhaust passage 2 downstream of the exhaust brake valve 4 is provided, and a waste gate valve 6 is attached to the exhaust bypass passage 5.

Reference numeral 7 is a controller, 8 is an air tank, 9 is an electromagnetic valve for controlling the exhaust brake, 10 is an air cylinder provided as an actuator of the exhaust brake valve 4, 11
Is an intake passage provided with the compressor 3b of the turbocharger 3, 12 is a boost pressure sensor, 13 is a pressure reducing valve, 14 is a solenoid valve for controlling a waste gate valve, and 15 is an air tank 8 via the pressure reducing valve 13 and the solenoid valve 14. It is a connected diaphragm actuator that opens and closes the waste gate valve 6.

The controller 7 outputs the rotation signal, load signal and boost pressure sensor 1 of the diesel engine 1 output from a rotation sensor and a load sensor (not shown).
2 is supplied as control information, and the exhaust brake valve 4 and the waste gate valve 6 are controlled to open and close based on these control information.

In the exhaust brake device for a turbocharged diesel engine having the above-described structure, when the diesel engine 1 is operating in a normal state, the controller 7 keeps the exhaust brake valve 4 open. While preventing the exhaust pressure from rising, the waste gate valve 6 is kept closed and the entire amount of exhaust gas is supplied to the turbine 3a, whereby the turbocharger 3 is operated and the conventionally known supercharging action is performed.

When the diesel engine 1 is operated in the high speed rotation range and the boost pressure becomes higher than a predetermined value when performing such supercharging action, the waste gate valve is output by the control signal output from the controller 7. By opening 6 to bypass the exhaust gas, the flow rate of the exhaust gas supplied to the turbine 3a is corrected to be reduced, and the boost pressure is prevented from rising more than necessary.

On the other hand, when the exhaust brake operating signal is output from the controller 7 during the operation of the exhaust brake, the solenoid valve 14 maintains the valve closed state and keeps the wastegate valve 6 closed, but the solenoid valve 9 operates. Open and air tank 8
Is supplied to the air cylinder 10 to close the exhaust brake valve 4. Then, the exhaust passage 2 is closed and the pressure in the exhaust port rises, so that the effectiveness of engine braking is increased and a predetermined braking force is obtained.

By the way, the magnitude of the braking force thus obtained increases as the pressure in the exhaust port increases. Further, the pressure in the exhaust port rises as the rotational speed of the diesel engine 1 increases, and the rate of rise at this time increases as the degree of sealing of the exhaust passage 2 by the exhaust brake valve 4 increases.

Therefore, if the exhaust hole provided in the exhaust brake valve 4 is made small in order to increase the braking force obtained in this way and the degree of sealing of the exhaust passage 2 is increased, the diesel engine 1 is in the normal rotation range. It is possible to increase the braking force in the low speed rotation range. However, in this case, the pressure in the exhaust port becomes higher than the abnormal behavior limit of the exhaust valve in the high speed rotation region where the flow rate of the exhaust gas increases, which may cause abnormal vibration of the exhaust valve.

However, when the diesel engine 1 is operated in the high speed rotation range as described above, the solenoid valve 1
A control signal for opening the valve 4 is output from the controller 7. Then, the solenoid valve 14 is operated to supply the air in the air tank 8 to the diaphragm actuator 15. Therefore, when the diesel engine 1 is operating in the high-speed rotation range when the exhaust brake is operated, the waste gate valve 6 is opened as shown by the chain double-dashed line in FIG. be opened.

When the exhaust bypass passage 5 is opened in this manner, the exhaust gas upstream of the turbine 3a is bypassed to the downstream side of the exhaust brake valve 4 through the exhaust bypass passage 5, so that the exhaust passage 2 is closed. The decrease in pressure suppresses the increase in the pressure in the exhaust port, and abnormal behavior of the exhaust valve is prevented.

As described above, according to the present embodiment, the degree of increase in the pressure in the exhaust port in the medium and low speed rotation range is increased by increasing the degree of sealing of the exhaust passage 2 by the exhaust brake valve 4 as shown in FIG. Although the brake force can be increased to obtain a sufficient braking force, the waste gate valve 6 is opened during the operation of the exhaust brake in the high-speed rotation range where the flow rate of exhaust gas is large, and the pressure in the exhaust port is abnormal. Since the rise can be avoided, the abnormal behavior of the exhaust valve, which has been a concern during the operation of the exhaust brake in the high speed rotation range, is prevented.

FIG. 2 is a characteristic diagram showing the relationship between the engine speed and the pressure in the exhaust port. In the figure, a thin solid line shows an ideal change in the pressure in the exhaust port, and a thick solid line shows the characteristic of the pressure in the exhaust port according to the above embodiment.

That is, the exhaust bypass passage 5 and the waste gate valve 6, which are conventionally provided to prevent the boost pressure of the turbocharger 3 from abnormally increasing,
In the present embodiment, the sealing degree of the exhaust passage 2 during the operation of the exhaust brake can be substantially changed by effectively utilizing the control of the pressure in the exhaust port during the operation of the exhaust brake. This is to avoid the abnormal increase in pressure inside the exhaust port. Therefore, according to the present embodiment, although the effect of the exhaust brake can be enhanced in the medium and low speed rotation range where the flow rate of the exhaust gas is relatively small, there is a concern during the operation of the exhaust brake in the high speed rotation range. Since it is possible to avoid an abnormal rise in the pressure inside the exhaust port, it is possible to prevent abnormal behavior of the exhaust valve.

FIG. 3 is a system diagram showing a second embodiment of the exhaust brake device for a turbocharged diesel engine according to the present invention. In this embodiment, an electromagnetic valve 16 is provided to switch and supply boost pressure supplied from the intake passage 11 downstream of the compressor 3b and air supplied from the air tank 8 to the diaphragm actuator 15.

When the exhaust brake is operated while the diesel engine 1 is operating in the low speed rotation range, the waste gate valve 6 is kept closed to increase the rate of increase in pressure in the exhaust port, Engine 1
By supplying boost pressure to the diaphragm actuator 15 when the engine is operating in the medium speed rotation range, the waste gate valve 6 is half-opened when the boost pressure becomes high, and the increase rate of the pressure in the exhaust port is corrected to decrease. I am trying.

Further, when the exhaust brake is operating while the diesel engine 1 is operating in the high speed rotation range, air is supplied to the diaphragm actuator 15 to fully open the wastegate valve 6 and bypass the turbine 3a. By increasing the flow rate of, the reduction correction rate of the pressure in the exhaust port is increased so that the pressure in the exhaust port does not exceed the abnormal behavior limit of the exhaust valve.

Therefore, according to the present embodiment, since the fluctuation of the pressure in the exhaust port due to the opening / closing operation of the wastegate valve 6 can be reduced as shown in FIG. 4, the operation of the wastegate valve 6 is performed. It is possible to prevent a sudden change in the effect of the exhaust brake that accompanies the change.

In the second embodiment described above, the opening of the waste gate valve 6 provided in the exhaust bypass passage 5 is changed stepwise. For example, the return spring of the diaphragm actuator 15 has a nonlinear characteristic. It is composed of a spring, and the opening of the wastegate valve 6 is changed steplessly by utilizing the balance action of this spring and the exhaust pressure acting on the wastegate valve 6, or a plurality of wastegate valves are installed side by side. It is also possible to change the opening degree of the exhaust bypass passage 5 stepwise or continuously.

FIG. 5 is a system diagram showing a third embodiment of an exhaust brake device for a turbocharged diesel engine according to the present invention. In this embodiment, the first bypass passage 5a is branched from the exhaust passage 2 upstream of the turbine 3a and merges with the exhaust passage 2 downstream of the exhaust brake valve 4, and the first bypass passage 5a is branched from the exhaust passage 2 upstream of the turbine 3a. A second bypass passage 5 that joins the exhaust passage 2 downstream of the turbine 3a and upstream of the exhaust brake valve 4.
The exhaust bypass passage is formed by b. The configuration is different from the above-described embodiments in that the upstream ends of the bypass passages 5a and 5b can be opened and closed by the waste gate valve 6, respectively.

Also in this embodiment, when the exhaust brake operates while the diesel engine 1 is operating in the medium to low speed rotation range, the diesel engine 1 keeps the waste gate valve 6 closed while the diesel engine 1 operates in the high speed rotation range. The waste gate valve 6 is opened during the operation of the exhaust brake in the state of being operated in the above condition, and the waste gate valve 6 and the exhaust brake valve 4 are controlled by the controller 7. Is substantially the same as

Therefore, in the present embodiment as well, when the exhaust brake is operating while the diesel engine 1 is operating in the medium to low speed rotation range, the exhaust brake valve 4 and the waste brake valve 4 and the waste brake valve 4 are controlled based on the control signal output from the controller 7. Since the gate valves 6 are both closed to close the exhaust passage 2, the pressure in the exhaust port rises, the effectiveness of engine braking increases, and a predetermined braking force is obtained.

Further, when the exhaust brake is operating while the diesel engine 1 is operating in the high speed rotation range, the waste gate valve 6 is opened as shown by the chain double-dashed line in FIG. The bypass passages 5a and 5b are opened.

However, even when the waste gate valve 6 is opened in this way, the first bypass passage 5a is also formed.
Only makes a bypass connection between the upstream and downstream of the exhaust brake valve 4, and the second bypass passage 5b does not act as a bypass. For this reason, the degree of sealing of the exhaust passage 2 does not lower more than necessary when the exhaust brake operates, and the effect of the exhaust brake is secured.

That is, the effectiveness of the exhaust brake depends on the degree of sealing of the exhaust passage 2 by the exhaust brake valve 4, and by reducing the escape hole provided in the exhaust brake valve 4, exhaust gas in the low speed rotation range is exhausted. As described above, the braking force can be increased. The cross-sectional area of the exhaust bypass passage is determined by the performance of the turbocharger. Therefore, when the exhaust bypass passage is opened during the operation of the exhaust brake while the diesel engine 1 is operating in the high speed rotation range to avoid an abnormal rise in the pressure in the exhaust port, the bypass flow rate of the exhaust gas is increased. There is a case where the exhaust brake becomes more effective than necessary and the effect of the exhaust brake is not always sufficiently high.

However, as in the third embodiment, the first bypass passage 5a bypassing the turbine 3a and the exhaust brake valve 4 and the second bypass passage 5b bypassing only the turbine 3a and not the exhaust brake valve 4 are exhausted. When the bypass passage is configured, the exhaust brake operates even when the total cross-sectional area of both bypass passages 5a and 5b is determined based on the performance of the turbocharger to prevent the boost pressure from rising excessively. Since the flow rate of exhaust gas bypassed at times can be limited to a necessary minimum, a sufficient braking force can be obtained.

Since the braking force at this time is determined by the cross-sectional area of the first bypass passage 5a, the characteristics of the diesel engine 1 and the turbocharger 3,
In addition, the cross-sectional area ratio of the bypass passages 5a and 5b may be set according to the size of the relief hole provided in the exhaust brake valve 4.

In each of the above-described embodiments, the actuator of the exhaust brake valve 4 is composed of the air cylinder 10 and the actuator of the waste gate valve 6 is composed of the diaphragm actuator 15. It is not limited.

Further, in the above embodiment, during normal operation without operating the exhaust brake, the controller 7 determines the optimum boost pressure based on various control information represented by the number of revolutions of the diesel engine 1, load and boost pressure. The control valve 14, which is calculated to realize this optimum boost pressure,
16 is controlled by the controller 7 to control the opening and closing of the waste gate valve 6. However, by supplying boost pressure to the diaphragm actuator 15, for example, the opening degree of the waste gate valve 6 is changed to optimize the boost pressure. It can also be controlled.

[0039]

As is apparent from the above description, according to the present invention, both the exhaust brake valve and the waste gate valve are closed when the exhaust brake is operated in the medium and low speed rotation range which is the normal rotation range of the diesel engine. While increasing the airtightness of the exhaust passage, when the exhaust brake operates in the high speed range of the diesel engine, the wastegate valve is opened to lower the airtightness of the exhaust passage and reduce the pressure in the exhaust port. Since the rise can be suppressed, the effectiveness of the exhaust brake is enhanced in the medium to low speed rotation range where the flow rate of exhaust gas is relatively small, while avoiding an abnormal rise in the pressure in the exhaust port in the high speed rotation range. It is possible to prevent abnormal behavior of the valve.

[Brief description of drawings]

FIG. 1 is a system diagram showing a first embodiment of an exhaust brake device for a turbocharged diesel engine according to the present invention.

FIG. 2 is a characteristic diagram showing the relationship between the engine speed and the pressure in the exhaust port according to the embodiment shown in FIG.

FIG. 3 is a system diagram showing a second embodiment of an exhaust brake device for a turbocharged diesel engine according to the present invention.

FIG. 4 is a characteristic diagram showing the relationship between the engine speed and the pressure in the exhaust port according to the embodiment shown in FIG.

FIG. 5 is a system diagram showing a third embodiment of an exhaust brake device for a turbocharged diesel engine according to the present invention.

6 is a characteristic diagram showing the relationship between the engine speed and the pressure in the exhaust port according to the embodiment shown in FIG.

FIG. 7 is a system diagram showing a conventional example of an exhaust brake device for a turbocharged diesel engine.

8 is a characteristic diagram showing the relationship between the engine speed and the pressure in the exhaust port according to the conventional example shown in FIG.

[Explanation of symbols]

 1 Diesel Engine 2 Exhaust Passage 3 Turbocharger 3a Turbine 3b Compressor 4 Exhaust Brake Valve 5 Exhaust Bypass Passage 5a First Bypass Passage 5b Second Bypass Passage 6 Wastegate Valve 7 Controller 8 Air Tank 9, 14, 16 Solenoid Valve 10 Air Cylinder 11 Intake passage 12 Boost pressure sensor 13 Pressure reducing valve 15 Diaphragm actuator

Claims (2)

[Claims] 1. An exhaust brake device for a turbocharged diesel engine having a wastegate valve, the exhaust brake valve being provided in an exhaust passage downstream of a turbine of the turbocharger, and branched from an exhaust passage upstream of the turbine. And an exhaust bypass passage that joins the exhaust passage downstream of the exhaust brake valve, a wastegate valve provided in the exhaust bypass passage, and opening / closing control of the exhaust brake valve and the wastegate valve in response to the operating state of the diesel engine. Exhaust brake system for turbocharged diesel engines equipped with a controller that 2. A first bypass passage branched from an exhaust passage upstream of the turbine and joined to an exhaust passage downstream of the exhaust brake valve, and an exhaust brake valve branched from an exhaust passage upstream of the turbine and downstream of the turbine. The exhaust gas of a diesel engine with a turbocharger according to claim 1, wherein an exhaust bypass passage is constituted by a second bypass passage that joins with an exhaust passage at a more upstream side, and waste gate valves are provided in both bypass passages. Brake device.