JP3298452B2 - Engine auxiliary brake device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auxiliary engine braking device for obtaining a braking force by controlling the operation of engine valves such as an intake valve and an exhaust valve of an engine.

[0002]

2. Description of the Related Art Conventionally, as one of engine braking devices for heavy vehicles such as trucks and buses, an exhaust valve is opened near a top dead center of a compression stroke that is different from a normal exhaust timing to increase the pressure in a cylinder. 2. Description of the Related Art A compression-pressure-released engine auxiliary brake device (engine auxiliary brake device) that obtains a braking force by releasing an applied pressure to an exhaust system side to cause an engine to perform a negative work has been put to practical use.

This compression-release type engine auxiliary brake system stops the supply of fuel and an exhaust valve based on an operation start command (for example, a switch provided in a driver's seat is turned on and an accelerator pedal is turned off). Is opened not only in the exhaust stroke but also near the top dead center of the compression stroke. That is, in the intake stroke, the intake valve is opened as usual to take in the intake air into the cylinder, and in the compression stroke, the piston rises to near the top dead center and the exhaust valve is opened when the pressure in the cylinder is increased. And discharge the compressed air to the exhaust system.

Further, by closing the exhaust valve after discharging the compressed air, the inside of the cylinder is closed during the expansion stroke, and the force for pushing down the piston is reduced as compared with the expansion stroke during normal operation. As a result, a negative force is applied to the engine so as not to lower the vehicle, so that the pump is operated as a negative work to obtain the braking force of the vehicle.

[0005] Further, such a compression-pressure-release type engine auxiliary brake device has a rotation angle of the engine crankshaft of 7 degrees.
One pump operation is performed at 20 degrees,
Japanese Patent Laid-Open No. 2275/1990
Japanese Patent Application Laid-Open No. 09-0909 discloses a rotation angle 72 of a crankshaft of an engine.
A technique of performing two pump operations at 0 degrees is disclosed.

According to this publication, intake is performed by opening an intake valve during an intake stroke of a four-cycle engine, an exhaust valve is opened near a top dead center of a compression stroke, and a first pump operation is performed. . The ignition at the compression top dead center is not performed. Further, in the expansion stroke of the four-stroke engine, the intake valve is opened again to take in the intake air, and in the exhaust stroke of the four-stroke engine, the air taken into the cylinder is compressed. Is opened to perform the second pump operation.

As a result, a larger braking force can be generated as compared with a compression-pressure-release type engine auxiliary brake device that performs one pump operation at a rotation angle of 720 degrees of the crankshaft of the engine. Further, in this conventional technique, the exhaust valve is further opened from the bottom dead center immediately after the intake valve is closed, so that the air once discharged to the exhaust system is re-inhaled, and the amount of intake air into the cylinder is increased. By increasing the compression work of the piston, the negative work performed by the engine when the exhaust valve is opened near the top dead center can be increased.

[0008]

However, in the case of the above-mentioned prior art, since the exhaust valve starts to open from the bottom dead center, the piston is in the compression stroke, and air from the exhaust system is released due to the upward movement of the piston. Not only is it difficult for the air to flow backward, but also the air sucked from the intake side may be exhausted to the exhaust side, and the amount of air in the cylinder cannot be obtained as expected.

In the above-mentioned prior art, since the exhaust valve is opened after the intake valve is completely closed, the flow of air in the cylinder when the exhaust valve is opened is stagnant. Immediately after this, the upward movement of the piston causes the flow of air in the cylinder to be rather pushed upwards of the cylinder, making it difficult to re-enter air from the exhaust system. The present invention has been made in view of such a problem, and an engine capable of increasing the amount of negative work performed by an engine by efficiently increasing an intake air amount and obtaining a large braking force. It is intended to provide an auxiliary brake device.

[0010]

[SUMMARY OF To this end, the engine auxiliary brake system of the present invention according to claim 1, when Jo Tokoro operation
The operation of the exhaust communication means starts just before the top dead center of the piston,
After passing the top dead center, the operation of the exhaust communication means ends and
The intake valve opens . And the piston reaches the bottom dead center
Previously, the intake valve closed and the opening period of the intake valve and the
The operation of the exhaust communication means starts to overlap,
The operation of the exhaust communication means ends after passing through the bottom dead center of the piston.
You . At the time of starting the operation of the exhaust communication means just before the top dead center of the piston, the piston is moving in the direction of the bottom dead center, the inside of the cylinder is in a reduced pressure state, and the flow of air is formed from the cylinder head toward the top surface of the piston. In addition, the air from the exhaust side easily flows backward, and the amount of air in the cylinder can be efficiently increased. Also, before the intake valve closes,
Since the operation of the exhaust communication means starts again, the exhaust communication means
At the start of operation, the intake air from the intake side
Air flow is formed in the downward direction,
The air flows more easily backwards, and the amount of air in the cylinder is reduced
It can be increased well.

[0011]

Further, the engine auxiliary brake system of the present invention of claim 2, wherein, when a predetermined operation, said intake valves and exhaust
A series of operations of the air communication means is one rotation of the crankshaft.
Since it is executed every time, it becomes possible to perform the pump operation twice at a rotation angle of 720 degrees of the crankshaft of the engine, and it is possible to generate a large braking force.

According to a third aspect of the present invention, there is provided an engine auxiliary brake device according to the present invention, wherein a turbocharger turbine is disposed downstream of a throttle device provided in an exhaust system, and the throttle device is operated in a throttle direction during a predetermined operation. To increase the backflow from the exhaust passage due to the increase in exhaust pulsation and exhaust pressure,
An increase in the amount of air passing through the turbocharger can be suppressed, and a turbocharger having a capacity appropriate for normal operation can be mounted.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an engine auxiliary brake device according to an embodiment of the present invention. FIG. 1 shows a four-cycle diesel engine (hereinafter simply referred to as an engine) 1 to which the present device is applied. FIG. 2 is a schematic cross-sectional view showing an arbitrary one cylinder of the engine 1.

As shown in FIG. 1, the engine 1 includes a compression-pressure-release type engine auxiliary brake 100 having a variable valve timing mechanism for switching the opening timing of intake valves (not shown) and exhaust valves 8, 8. And a turbocharger 102 for supercharging the intake air by the exhaust pressure. On the upstream side of the exhaust turbine 121 of the turbocharger 102, a variable nozzle 1 as a throttle means for narrowing the flow of exhaust gas is provided.
51 is provided to reduce the flow rate of the fluid discharged from the exhaust valves 8 as exhaust communication means. 1A shown in FIG. 1 is a combustion chamber of the engine.

Hereinafter, the turbocharger 102 will be described in detail.
An exhaust turbine 121 interposed in an exhaust passage 103 of the engine and rotating by receiving exhaust energy of exhaust gas, and an exhaust turbine 121 interposed in an intake passage 104 of the engine 1
And an intake compressor 122 that rotates by the rotational force of the compressor to compress intake air (intake).

The exhaust turbine 121 and the intake compressor 122 are coaxially connected by a turbine shaft 123, and the intake compressor 122 rotates at a rotational speed corresponding to the rotational speed of the exhaust turbine 121. By the way, the opening degree of the variable nozzle 151 is controlled by the actuator 152,
Further, the operation of the actuator 152 is controlled based on an operation control signal from the controller 23 constituting the variable exhaust means.

Although the opening of the variable nozzle 151 is configured to be changed in a stepwise manner, it may be configured to be able to be changed continuously in addition to this. Also,
As shown in FIG. 1, the controller 23 receives, as constituent means, rotation number information of the engine 1, rotation information of the exhaust turbine 121, opening degree information of the variable nozzle 151, vehicle speed information, and the like. From these information, during normal running, the opening of the variable nozzle 151 is controlled in the normal running mode.

Referring to FIG. 2, the hydraulic oil supply passage 40 is connected to the oil pan 25, and the hydraulic oil in the oil pan 25 is pumped. 24 is supplied to the compression-pressure release type engine auxiliary brake 100. A solenoid valve 26 is provided on the downstream side of the pump 24. By controlling the solenoid valve 26 to be turned on, the supply state of the operating oil of the compression-pressure-release type engine auxiliary brake 100 is controlled. If the operating oil is not supplied, the oil pan 25 drains.

A controller 23 is connected to the solenoid valve 26, and the operating state of the solenoid valve 26 is controlled by the controller 23. Various sensors such as an accelerator switch and a brake switch (not shown) are connected to the controller 23 so that driving operation information of the driver is input.

In this embodiment, after the engine auxiliary brake switch (not shown) is turned on, the driver returns the accelerator pedal to perform a deceleration operation (predetermined operation of the engine).
6 is controlled to be on so that hydraulic oil is supplied to the compression-pressure releasing engine auxiliary brake 100. At other times, the solenoid valve 26 is off.

Therefore, when the driver performs a deceleration operation, the operation mode of the engine 1 is switched from the normal operation mode to the engine auxiliary brake operation mode, and the compression-pressure releasing engine brake 100, which is a variable valve timing mechanism, is operated. . In this case, the fuel injection from the injector 17 is stopped.

Since the engine auxiliary brake device according to one embodiment of the present invention is configured as described above, during normal operation of the engine 1, the opening of the variable nozzle 151 of the turbocharger 102 is controlled by the controller 23 during normal running. The mode is controlled so that the solenoid valve 26 of the compression-release engine brake 100 is turned off. As a result, the intake valve and the exhaust valve 8 are driven at valve timings suitable for normal operation of the engine, and the engine 1
Is operated normally.

On the other hand, when the driver performs the deceleration operation by returning the accelerator pedal after the engine auxiliary brake switch is turned on at the time of the predetermined operation of the engine, the solenoid valve 26 of the compression pressure release type engine brake 100 is controlled by the controller 23. Is turned on based on this control signal, and the intake and exhaust valves 8, 8 are driven at the timing for engine auxiliary braking. At the same time, the opening degree of the variable nozzle 151 of the turbocharger 102 is reduced by a predetermined amount by the controller 23, and the exhaust passage 10
Acts as an aperture of 3.

FIG. 3 shows the characteristics of the valve lift when the intake valve and the exhaust valve 8, 8 are driven at the engine auxiliary brake timing. The intake valve is a piston 70
Begins to open after passing through the top dead center (crankshaft rotation angle = 0 degrees), and closes before the bottom dead center (crankshaft rotation angle = 180 degrees). In addition, just before the intake valve closes just before the bottom dead center, the exhaust valves 8 and 8 start to open.
0 passes through the bottom dead center, the exhaust valves 8 and 8 close, and the piston 7
With the rise of 0, the air in the cylinder 1A is compressed.
As a result, a large force acts on the piston 70 in a direction that hinders the rotation of the engine 1.

When the piston 70 rises to the vicinity of the top dead center (crankshaft rotation angle = 360 degrees), the exhaust valves 8, 8 are opened again, and the compressed air is discharged to the exhaust passage 103. By repeatedly performing the above operation at every 360 ° rotation angle of the crankshaft, a large engine braking force can be continuously obtained. That is, the intake valve normally opens once at 720 degrees of the crankshaft, but in the present embodiment, the valve opens twice at 720 degrees, so that twice the cycle is generated.

The engine auxiliary brake device as one embodiment of the present invention operates as described above, and has various functions and effects. That is, before the piston 70 is at the bottom dead center, the air in the intake passage 104 is taken in, the pressure in the cylinder 1A is low, the pressure is in the decompression direction, and the piston 70 moves in the bottom dead center direction. Inside, the flow of air in the cylinder 1A is formed from the cylinder head side to the top surface side of the piston 70.
At this time, by opening the exhaust valves 8, 8, the exhaust passage 103 is opened.
The inside air rides on the air flow inside the cylinder 1A, and the backflow is promoted.

Immediately before the intake valve closes, the exhaust valves 8, 8 are closed.
(I.e., by overlapping the opening periods of the intake valves and the exhaust valves 8, 8), the inertial force of the intake air flow introduced from the intake passage 104 acts.
The backflow of the air from the exhaust passage 103 is promoted. Further, in this predetermined operation state, since the variable nozzle 151 is controlled to be in a throttled state and acts as a flow path resistance, the pressure wave of the high-pressure air in the exhaust passage 103 is once generated downstream of the exhaust passage 103. When the piston 70 reaches the vicinity of the bottom dead center, the pressure wave reflected by the variable nozzle 151 reaches the vicinity of the exhaust valves 8 again.

Thus, when the exhaust valves 8, 8 are opened at the timing of the engine auxiliary brake, the pulsation of the exhaust promotes the backflow of the high-pressure air in the exhaust passage 103 into the cylinder 1A, so that a large amount of the air flows. Air to cylinder 1A
Can be taken in, increasing the volumetric efficiency. Thus, the amount of air flowing into the cylinder 1A is greatly increased, and the engine 1 performs a negative work of compressing the air in the cylinder, thereby operating the engine 1 as a pump. Energy can be efficiently absorbed and a large braking force can be obtained.

FIG. 4 is a view showing the intake air amount and the exhaust air amount when the engine auxiliary brake 100 is operated. As shown in FIG. In a short period, the air in the cylinder 1A is rapidly discharged. In the overlap period immediately after the piston 70 passes through the top dead center and the intake valve opens,
Air escapes from the exhaust valves 8 and 8 to the intake valve side for a moment, and then air is sucked from the intake valve as the piston 70 descends (indicated by A in the figure).

When the exhaust valves 8 and 8 are lifted near the bottom dead center of the piston 70, as described above, the air flows backward from the exhaust passage 103 due to the exhaust pulsation due to the throttle operation of the variable nozzle 151 and the increase in the exhaust pressure. Cylinder 1A
Flows into. Assuming that the amount of intake air at this time is B, the amount of intake air flowing into the cylinder 1A per rotation of the crankshaft is A + B, and a large amount of air can be sucked into the cylinder 1A. The ratio of the amount of intake air from the intake valve to the amount of intake air from the exhaust valves 8, 8 is, for example, about 60:40.

In the engine 1 with the turbocharger 102 as in the present embodiment, it is particularly effective to drive the intake valves and the exhaust valves 8, 8 at the timing for engine auxiliary braking and to throttle the variable nozzle 151. It is. This is because in normal operation, the intake valve is opened only once at a crankshaft rotation angle of 720 degrees, whereas when the engine auxiliary brake device is activated, a two-stroke cycle (at a crankshaft rotation angle of 720 degrees) is performed. 2), the amount of intake air flowing through the intake passage 104 is increased, and the compressor 12 of the turbocharger 102 is opened.
It is necessary to increase the capacity of the second capacitor. That is, in the turbocharger 102 adapted to the intake air amount during the normal operation, the capacity is insufficient, and the allowable rotation speed of the turbocharger is exceeded. However, if the compressor 122 having a larger capacity than necessary is present in the intake passage 104 during normal operation, the supercharging effect during acceleration is reduced.

Therefore, due to the exhaust pulsation and the increase in exhaust pressure caused by the restriction of the variable nozzle 151, the backflow from the exhaust passage 103 when the exhaust valves 8, 8 are opened before the bottom dead center is increased, and Supplementing the shortage of the intake air to be supplied, ensuring the effect of the engine auxiliary brake, maintaining the supercharging effect at the normal time, and keeping the rotation speed of the exhaust turbine 121 below the allowable rotation speed due to the decrease in the exhaust flow rate. be able to. As a result, the turbocharger 102 having an appropriate capacity (size) can be mounted in the normal operation, and one turbocharger 102 can sufficiently perform both the normal operation and the predetermined operation (when the engine auxiliary brake device is operating). There is an advantage that it can be used for

In the above-described embodiment, the compression-pressure release type engine auxiliary brake 100 is operated by a two-stroke cycle in which one cycle is completed at a rotation angle of 360 ° of the crankshaft. The engine auxiliary brake 100 may be operated by a four-stroke cycle in which one cycle ends at a time.

Further, the engine auxiliary brake device of the present invention adjusts the valve timing of the upper intake valve and the exhaust valve 8,
Any of various variable valve mechanisms including a well-known variable valve mechanism may be used as long as the valve timing can be changed as described above. Further, the throttle means is not limited to the above-described variable nozzle 151 of the turbocharger 102, but may have another configuration as long as it reduces the flow velocity of the fluid flowing through the exhaust passage 103.

[0036]

As described above in detail, according to the engine auxiliary brake device of the first aspect of the present invention, during the predetermined operation, the operation of the exhaust communication means just before the top dead center of the piston.
And after the passage of the top dead center, the operation of the exhaust communication means is started.
The operation is terminated and the intake valve is opened, and the piston is
Before reaching the bottom dead center, close the intake valve and
The exhaust communication is overlapped with the opening period of the intake valve.
The operation of the means is started, and after passing through the bottom dead center of the piston,
With the configuration of terminating the operation of the exhaust communication means,
At the start of the operation of the exhaust communication means just before the top dead center of the ston , the piston is moving in the direction of the bottom dead center. It is said that air from the exhaust side easily flows backward, the amount of air in the cylinder can be efficiently increased, and thereby the absorption horsepower of the engine auxiliary brake device can be increased to obtain a large braking force. There are advantages. Before the intake valve closes
Then, the operation of the exhaust communication means is restarted.
Intake air from the intake system at the start of the communication means
Due to the inertia of the flow, the backflow of air from the exhaust passage is
To increase the air volume in the cylinder efficiently.
There is an advantage that can be.

[0037]

The engine auxiliary brake device according to the second aspect of the present invention provides the above-described intake valve and exhaust communication means.
A series of operations is performed for each revolution of the crankshaft.
Therefore, it is possible to perform the pump operation twice at a rotation angle of 720 degrees of the crankshaft of the engine, and there is an advantage that a large braking force can be generated.

According to a third aspect of the present invention, there is provided the engine auxiliary brake device, wherein a turbocharger turbine is disposed downstream of the throttle means provided in the exhaust system, and the throttle means is operated in the throttle direction during a predetermined operation. Therefore, due to the increase in the exhaust pulsation and the exhaust pressure, the backflow from the exhaust passage is increased, the increase in the flow rate passing through the turbocharger is suppressed, and it is possible to install a turbocharger having a capacity appropriate for normal operation. There is an advantage.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an entire configuration of an engine auxiliary brake device as one embodiment of the present invention.

FIG. 2 is a schematic diagram showing a configuration of a control system in an engine auxiliary brake device as one embodiment of the present invention.

FIG. 3 is a diagram showing valve timing characteristics in the engine auxiliary brake device as one embodiment of the present invention.

FIG. 4 is a diagram showing characteristics of an intake air amount and an exhaust air amount in the engine auxiliary brake device as one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 1A Combustion chamber 23 Controller constituting variable exhaust means 24 Pump 25 Oil pan 26 Solenoid valve 40 Hydraulic oil supply path 70 Piston 100 Compression pressure release type engine auxiliary brake 102 Turbocharger 103 Exhaust passage (exhaust system) 104 Intake passage ( Intake system) 105 Exhaust throttle means 121 Exhaust turbine 122 Intake compressor 123 Turbine shaft 151 Variable nozzle

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI F02B 37/22 F02D 9/06 C F02D 9/06 H F02B 37/12 301N (56) References JP-A-63-25330 (JP) , A) JP-A-6-2520 (JP, A) JP-A-2-227509 (JP, A) JP-A-8-270425 (JP, A) JP-A 60-36506 (JP, U) JP-A 64-49638 (JP, U) Japanese Utility Model Showa 61-159639 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 13/04 F01L 13/06

Claims (3)

(57) [Claims] It includes a 1. A combustion chamber of the engine and the exhaust communicating means capable communicates between the exhaust system and an intake valve capable of communicating between the intake system and combustion chamber of the engine, given the engine An engine auxiliary brake device for operating the exhaust communication means near a compression top dead center of a piston during operation, wherein the exhaust communication is performed just before the top dead center of the piston during the predetermined operation.
Start the operation of the means, and after passing the top dead center,
Ending the operation of the stage and opening the intake valve,
Close the intake valve before the piston reaches the bottom dead center
So that it overlaps with the opening period of the intake valve
The operation of the exhaust communication means is started, and the bottom dead center of the piston is
An auxiliary engine braking device, wherein the operation of the exhaust communication means is terminated after the passage . 2. The method according to claim 1 , wherein said intake valve and said exhaust valve are provided during said predetermined operation.
A series of operations of the communication means is performed every rotation of the crankshaft.
Characterized in that it is configured to be executed on
The engine auxiliary brake device according to claim 1. 3. Throttling means for restricting the flow of said exhaust gas to said exhaust system.
And a turbocharger turbine downstream of the throttle means.
Further provided so that the throttle means operates in the throttle direction during the predetermined operation.
Characterized in that it is configured, an engine auxiliary brake device according to claim 1 or 2, wherein.