JPH08100682A - Exhaust brake device - Google Patents

Abstract

PURPOSE: To decrease a return time lag during release to the atmosphere by lowering invalid pressure to the strokes of pressure type actuators in order to reduce temporary black smoke during release of an exhaust brake. CONSTITUTION: A pressure reducing valve 22 is provided in a pressure passage 9 between an air tank 1 and a three-way solenoid valve 2. Setting pressure of its secondary side is a little higher than the working return pressure of pressure actuators 8a, 8b and 18. Thus, the range of invalid pressure of air supply pressure relative to the strokes of the pressure type actuators is improved and reduced, so that time lag during release to the atmosphere of the pressure type actuators can be shortened.

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 reducing black smoke temporarily generated when the exhaust brake is released.

[0002]

Exhaust brake devices are widely used as auxiliary brakes for foot brakes, especially in large vehicles such as trucks and buses equipped with diesel engines. In this device, the pressure in the exhaust pipe becomes high by closing the exhaust pipe of the internal combustion engine, and during the exhaust stroke, this pressure acts as a force to push the piston back, so a braking force acts on the vehicle. It will be.

FIG. 5 is a system diagram showing an outline of a conventional exhaust brake device. 1 is an air tank which is always maintained within a predetermined pressure range by an air compressor (not shown), 2 is an accelerator switch 3, an exhaust brake switch 4 and a clutch. A three-way solenoid valve that interlocks with ON / OFF of the switch 5, 6 is an exhaust brake valve that is provided in the exhaust passage 7 and opens and closes by the operation of the pressure actuator 8, and 9 is a pressure passage that guides air pressure to the pressure actuator 8. is there.

The operation of the exhaust brake device having the above-mentioned structure will be briefly described below. This device is used with engine braking when traveling on a long downhill,
When the driver turns on the exhaust brake switch 4 arranged at a proper position in the driver's cab as needed, the three-way solenoid valve 2 is actuated and the air pressure is supplied from the air tank 1 to the pressure type actuator 8. The pressure type actuator 8 which receives this air pressure closes the exhaust brake valve 6 which is normally open, and shuts off between the combustion chamber 10 and the atmosphere. As a result, when the piston 11 rises during the exhaust stroke, the pressure on the combustion chamber 10 side of the exhaust brake valve 6 increases, and this pressure acts as a force in a direction to push the piston 11 back, that is, an exhaust brake force for the vehicle. .

In this exhaust brake device, the clutch switch 5 or the accelerator switch 3 is turned off by the driver operating the clutch pedal or the accelerator pedal during operation of the exhaust brake. Therefore, the electric circuit is temporarily turned off, the three-way solenoid valve 2 is operated, and the air pressure supplied to the pressure type actuator 8 is released from the exhaust port 2a to the atmosphere, so that the exhaust brake valve 6 is opened. The exhaust brake is released. In the figure, reference numeral 12 is an exhaust valve, arrow 13 is exhaust, 14 is an exhaust brake operation indicator light, 15 is a fuse, and 16 is a battery.

Further, the exhaust brake device shown in FIG.
It is equipped with an intake silencer device that reduces intake noise generated when the exhaust brake is activated. This device is provided with a silencer valve 19 which is opened and closed by a pressure type actuator 18 in an intake passage 17, and is closed by an air pressure supplied through a three-way solenoid valve 2 when an exhaust brake is operated. . This device
Since the exhaust brake device and the three-way solenoid valve 2 are shared,
Its operation and release are almost the same as the exhaust brake device,
In the figure, 20 indicates an intake valve, and a white arrow 21 indicates intake.

The above-described intake silencer device is not necessarily installed side by side with the exhaust brake device.
The presence or absence thereof is appropriately selected by considering various conditions.

Further, in the conventional structure, as shown in FIG. 5, one three-way solenoid valve 2 controls the air pressure supply to the pressure actuator 8 for the exhaust brake and the pressure actuator 18 for the intake silencer. Although not shown in the figure, even in a model having a plurality of pressure actuators 8 for braking, one three-way solenoid valve 2 controls the air pressure supply to all the pressure actuators 8 and 18. Was configured.

[0009]

By the way, in recent social situations, the generation of black smoke from diesel engines has been a problem due to reasons such as environmental protection. It has been improved to a level that cannot be visually confirmed. However, for the large amount of black smoke that is temporarily emitted when the exhaust brake is released,
It has been overlooked because there are no special regulations and it is a temporary phenomenon, but in the future, it is desirable to improve the appearance of abnormal black smoke at an early stage.

The reason why black smoke is generated when the exhaust brake is released is not currently well understood. However, it is estimated as follows based on various experimental results.

That is, when the accelerator pedal is operated from the state where the butterfly valve used for the exhaust brake valve 6 and the silencer valve 19 is closed and the exhaust brake is operated, an exhaust brake release signal is generated and the three-way solenoid valve 2 is turned on. Activate. However, since there is a slight time lag between the operation of the accelerator pedal and the opening of the exhaust brake valve 6 and the silencer valve 19, the fuel injected into the combustion chamber 10 during this period is blocked because of the inflow of the intake air 21. It is considered that the gas is burned and the gas generated by this is discharged as black smoke. While the exhaust brake is operating, there is almost no fuel injection, but when the accelerator pedal is depressed, the rack moves and fuel injection is started.

For example, assuming that the time lag until the above-mentioned valve starts to open is 0.4 seconds, when the accelerator pedal is depressed at an engine speed of 1200 rpm, the engine needs to be 8 times before the valve starts to open. It will rotate. Therefore, it is considered that four times the engine displacement is combusted in a state where the air inflow is blocked (or a state close to the block), and this portion is considered to emit black smoke due to incomplete combustion.

Further, even in the model without the intake silencer device, the gas during the operation of the exhaust brake is accumulated around the combustion chamber, which is considered to be the cause of the generation of black smoke due to incomplete combustion or the like.

Therefore, in the present invention, in order to reduce the above-mentioned time lag until the valve starts to be opened, a pressure adjusting means is provided in the pressure passage between the air tank and the three-way solenoid valve to reduce the ineffective pressure with respect to the stroke so as to reduce the pressure. It is an object of the present invention to provide an exhaust brake device with a reduced time lag when released (returned).

[0015]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an exhaust brake valve provided in an exhaust passage and a pressure type actuator for driving the exhaust brake valve to open and close. And a pressure passage for supplying pressure to the same pressure type actuator, a three-way solenoid valve provided in the pressure passage, and a pressure adjusting means provided in the pressure passage. .

[0016]

According to the above-mentioned means, the pressure adjusting valve is provided between the air tank and the three-way solenoid valve, and the secondary side set pressure of the pressure adjusting valve is adjusted to a value slightly higher than the return operating pressure of the pressure type actuator. As a result, the reactive pressure range for the stroke of the pressure type actuator is improved and reduced.
For this reason, the time from the reception of the exhaust brake release signal to the start of the return operation of the pressure type actuator is shortened, and therefore the time lag until the opening of the valve is shortened as compared with the conventional case.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of an exhaust brake device according to the present invention will be described below with reference to FIG.

In this embodiment, two exhaust passages 7a,
7b are provided with exhaust brake valves 6a and 6b, respectively, and the valves 6a and 6b are provided with pressure type actuators 8a and 8b for opening and closing. Further, the intake passage 17 is provided with a silencer valve 19 constituting an intake silencer device and a pressure type actuator 18 for opening and closing the silencer valve 19.

Three pressure type actuators 8a, 8b,
All 18 are connected to the air tank 1 by a pressure passage 9, and the air pressure supply to each of these actuators is controlled by the passage switching operation of one three-way solenoid valve 2.
In addition, the pressure passage 9 between the air tank 1 and the three-way solenoid valve 2
Is provided with a pressure reducing valve 22 as a pressure adjusting means, and the secondary side air pressure passing through the pressure reducing valve is set to be slightly higher than the return operating pressure of the pressure type actuator.

The three-way solenoid valve 2 closes the pressure passage 9 when the exhaust brake is inactive (exhaust brake switch 4 is off), and the air pressure of the air tank 1 acts on each pressure type actuator 8a, 8b, 18. To prevent it. At this time, the exhaust port 2a of the three-way solenoid valve 2 opens each pressure type actuator 8a, 8b, 18 to the atmosphere. Further, the three-way solenoid valve 2 switches the pressure passage 9 to the communication state when the exhaust brake is operated (exhaust brake switch 4 is on), and the air pressure supplied from the air tank 1 is applied to the pressure type actuators 8a, 8b, 18 respectively. Let it work. As a result, the exhaust brake valves 6a and 6b and the silencer valve 19 are switched to the closed state, the exhaust brake device operates to generate a braking force, and the intake silencer device operates to reduce intake noise.

Now, a method for setting the pressure of the pressure reducing valve 22 will be described with reference to FIG. The general air tank 1 used in the exhaust brake device has a maximum of 8.5k depending on the setting of the internal pressure side governor operating pressure and the unloader operating pressure.
The internal pressure fluctuates within the range of g / cm ² to a minimum of 6.8 kg / cm ² . On the other hand, the pressure type actuators 8a, 8b, 1
The air cylinder used as No. 8 operates in the range from 0% of the cylinder stroke with an air cylinder internal pressure of 1.5 kg / cm ² to 100% of the cylinder stroke with an air cylinder internal pressure of 4.5 kg / cm ² , and therefore has conventionally been a return operation. The internal pressure of the air tank in the region higher than 4.5 kg / cm ^2, which is also the starting pressure, is the reactive pressure for the stroke (maximum 4 kg.
/ Cm ² ). Therefore, for example, the pressure reducing valve 22
If the set pressure is set to 5 kg / cm ² which is slightly higher than the return operation start pressure of the air cylinder, the reactive pressure for the stroke is reduced to 0.5 kg / cm ² . Therefore, when the exhaust brake is opened when the cylinder stroke is 100% when the exhaust brake valves 6a and 6b and the silencer valve 19 are closed, the air pressure is exhausted by an invalid pressure of 0.5 kg / cm ² and then the cylinder is exhausted. As the stroke begins to return, each valve will begin to open. For this reason, the cylinder return time lag (that is, the time lag until the start of valve opening) is shortened, and the amount of black smoke generated due to incomplete combustion during this time is reduced.

FIG. 3 shows the test results showing the relationship between the pressure reducing valve setting pressure and the cylinder return time, which is 8 k corresponding to the conventional example.
Comparing g / cm ² pressure regulation and 5 kg / cm ² pressure regulation,
A reduction of about 0.1 seconds is observed. It should be noted that the pressure reducing valve set pressure reduces the time lag as it approaches the return operating pressure of the air cylinder, but in reality it is necessary to determine the optimum value in consideration of the problem of error range and the like.

FIG. 4 shows the relationship between the smoke level and the above-mentioned time lag. If the smoke level corresponding to the conventional time lag is 100, the black smoke generation amount decreases as the time lag becomes smaller. I understand.
That is, if the engine speed is the same, the smaller the time lag, the lower the engine speed during that time, and the amount of gas discharged during incomplete combustion during this time is half the engine speed during the time lag. Expected to be equivalent to the amount multiplied.

In the embodiment shown in FIG. 1, two exhaust passages and one intake passage are shown, but various modifications are possible depending on the structure and size of the engine. For example, as shown in the conventional example of FIG. 5, it goes without saying that the configuration of the present invention can be applied not only when both the exhaust passage and the intake passage have one system, but also when both systems have two or more systems. Yes.

Although the intake silencer device is provided in the embodiment shown in FIG. 1, it goes without saying that the present invention can be applied without this device. However, without this device, since there is no time lag of the silencer valve, the reduction of black smoke is not as remarkable as in the above-mentioned embodiment.

The operating pressure of the device may be either positive pressure or negative pressure, for example, by changing the spring biasing direction of the pressure type actuator.

[0027]

According to the present invention described above, the return time lag of the pressure type actuator (time lag until the opening of the valve due to atmospheric release) that contributes to the reduction of black smoke when the exhaust brake is released is greatly improved, and the diesel engine is improved. It has a great effect on solving the black smoke problem.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of an exhaust brake device according to the present invention.

FIG. 2 is a diagram showing operating characteristics of a pressure type actuator (air cylinder).

FIG. 3 is a diagram showing an operation test result of a conventional actuator (air cylinder) for each set pressure of a pressure reducing valve.

FIG. 4 is a diagram showing a relationship between a smoke level and a time lag.

FIG. 5 is a system diagram showing a conventional exhaust brake device.

[Explanation of symbols]

 1 Air Tank 2 3-way Solenoid Valve 3 Accelerator Switch 4 Exhaust Brake Switch 5 Clutch Switch 6, 6a, 6b Exhaust Brake Valve 7, 7a, 7b Exhaust Passage 8, 8a, 8b, 18 Pressure Actuator 9 Pressure Passage 17 Intake Passage 19 Silencer Valve 22 Pressure reducing valve

Claims (1)

[Claims] 1. An exhaust brake valve provided in an exhaust passage, a pressure actuator for opening and closing the exhaust brake valve, a pressure passage for supplying a pressure to the pressure actuator, and a pressure passage provided in the pressure passage. An exhaust brake device comprising a three-way solenoid valve and pressure adjusting means provided in the pressure passage.