JPH11101139A - Engine braking device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display large braking force by providing a boost pressure control means executing boost pressure control in a different mode from the time of normal operation when an exhaust valve is opened in an engine braking device controlling opening/closing of the exhaust valve by supplying/discharging fluid pressure in an engine with a supercharger. SOLUTION: A brake unit 6 is provided at a top part of one exhaust valve 3a between two exhaust valves 3a, 3b opened/closed at normal valve timing by the rotation of a cam through a locker arm. The brake unit 6 is so constituted that a piston is pushed down by oil pressure when an operation switching valve 7 is opened at the 'ON' time of an engine brake switch so as to push down the exhaust valve 3a. When an engine brake is operated, a controller 8 judges the presence of load. At the loaded time, large braking force is required, so that target boost pressure is computed to heighten boost pressure at the loaded time compared to the unloaded time to control a waste gate valve 19 or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine brake device applied to an engine having a turbocharger.

[0002]

2. Description of the Related Art Recently, various engine brake devices have been proposed which increase an engine braking force by lifting an exhaust valve or a dedicated valve when an engine brake is used and releasing a compression pressure in a cylinder of the engine. ing. Of these, the normally open type engine brake system pushes the piston hydraulically to hold the valve in a slightly lifted position when the braking force needs to be increased, and compresses the cylinder from the cylinder throughout the entire cycle. I try to release the pressure. The present applicant has previously proposed such an engine brake device (Japanese Patent Application No. 9-12928).

[0003]

When the above-described engine brake device is applied to an engine having a supercharger (supercharged engine), the supercharging pressure may not match the required braking performance. There is a problem that it is not possible to obtain proper braking performance.

[0004]

SUMMARY OF THE INVENTION The present invention is applied to an engine having a supercharger, and controls the opening and closing of an exhaust valve by supplying and discharging fluid pressure. A supercharging pressure control means for executing the supercharging pressure control of the supercharger in a mode different from that during engine operation is provided.

According to this, when the engine brake is used, it is possible to execute a dedicated boost pressure control suitable for the engine brake,
As a result, the cylinder internal pressure is increased, and a large braking force can be obtained.

[0006] It is preferable that the control means executes the supercharging pressure control based on the load of the vehicle, and it is preferable that the control means executes the supercharging pressure control based on the speed of the vehicle.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an overall configuration diagram of an engine brake device according to the present invention. Although the engine 1 is provided with a turbocharger 2, since there are an exhaust bypass method and a variable nozzle vane method as a supercharging pressure control method of the turbocharger 2, these are described together here, and A and B are respectively described. The code is attached.

Hereinafter, a common configuration will be described. The engine 1 is provided with two exhaust valves 3a and 3b, which are connected by a valve bridge 4 and are opened / closed or lifted at a normal valve timing by a cam of a cam shaft via a rocker arm (not shown). I have.

The one exhaust valve 3a shown on the right side can be opened and closed regardless of the valve timing.
That is, a brake unit 6 is provided at the top of the exhaust valve 3a, and the brake unit 6 has a piston therein, and when the piston is pushed down by hydraulic pressure (fluid pressure), the exhaust valve 3a is pushed down to make a minute lift. It has become. The operation switching valve 7 supplies and discharges the hydraulic pressure to and from the brake unit 6. The operation switching valve 7 is switched based on a control signal from the controller 8 to execute the supply and discharge of the hydraulic pressure. The operation switching valve 7 is constantly supplied with hydraulic pressure from an oil pump of the engine, and the hydraulic pressure is supplied to the brake unit 6 when the operation switching valve 7 is turned on. Operation switching valve 7 is OFF
In this case, the hydraulic pressure supply is stopped, and the hydraulic pressure of the brake unit 6 is returned to the operation switching valve 7 and leaked to the outside.

The turbocharger 2 has a turbine 10 provided in the middle of an exhaust passage 9 and a compressor 12 provided in a middle of an intake passage 11. Are connected coaxially. The turbine 10 is driven to rotate by utilizing the energy of the exhaust gas in the exhaust passage 9 and rotates the compressor 12 at the same rotation speed. Thus, compressor 1
2 is driven to rotate, the compressor 12 draws in outside air through the air filter 14 and compresses it to a predetermined supercharging pressure.
The pressure is increased and sent to the intercooler 15. Then, the compressed air cooled by the intercooler 15 is sent to the engine 1. Power generated by engine 1 is clutch 1
6, transmitted to the drive wheels 17 via a transmission and the like.

Next, different configurations will be described. First, in the supercharging device using the exhaust bypass system indicated by A, a bypass passage 18 that bypasses the turbine 10 is provided in the exhaust passage 9 so that the opening of the bypass passage 18 is defined by the wastegate valve 19. Has become. The wastegate valve 19 distributes exhaust gas sent from the engine 1 to the turbine 10 side and the bypass side at a predetermined ratio. For example, if the bypass flow rate is small, a large amount of exhaust gas is sent to the turbine 10, and the turbine 10 and the compressor 12 are rotated at high speed, and the supercharging pressure is increased. The wastegate valve 19 is operated by an actuator, here a servomotor 20. The controller 8 sends a control signal to the servomotor 20 to execute the supercharging pressure control.

On the other hand, in the supercharging device using the variable nozzle vane system indicated by B, a variable nozzle vane 21 is provided at the turbine inlet of the exhaust passage 9, and by controlling the opening of the variable nozzle vane 21, the turbine is controlled. 1
The flow rate of the exhaust gas given to 0 is changed. That is, when the variable nozzle vane 21 is operated to the closing side, the inlet of the turbine 10 is throttled, the flow velocity increases, the turbine 10 and the compressor 12 rotate at high speed, and the supercharging pressure increases. The variable nozzle vane 21 is operated by an actuator, here an air cylinder 22. Air pressure controlled to a predetermined pressure is sent from the solenoid valve 23 to the air cylinder 22. High-pressure air is constantly supplied to the electromagnetic valve 23 from an air tank (not shown). The electromagnetic valve 23 appropriately reduces the high-pressure air based on a control signal from the controller 8 and sends the air to the air cylinder 22. As described above, the controller 8 performs the supercharging pressure control also in this case.

As is common again, here, the controller 8 is a control unit that also performs fuel control of the engine 1, receives various detection signals, information, and the like from various sensors, switches, and the like, and performs predetermined calculations and the like. The operation switching valve 7, the servo motor 20, or the solenoid valve 23 is controlled to execute engine brake control and supercharging pressure control. As the sensors, an engine speed sensor 24 for detecting the engine speed, a clutch sensor 25 for detecting the connection / disconnection of the clutch,
A vehicle speed sensor 26 for detecting the speed of the vehicle, a load sensor 27 for detecting the load of the vehicle, a supercharging pressure sensor 28 for detecting the supercharging pressure of the engine 1, and a water temperature sensor (not shown) for detecting the temperature of the engine coolant. Z) is provided. As switches, an engine brake switch (not shown) that is provided in the vehicle compartment and is turned on / off by a driver's manual operation, a clutch pedal switch (not shown) provided on a clutch pedal, and an accelerator pedal are provided. There is an accelerator pedal switch (not shown) and the like.

The controller 8 stores a map of the target supercharging pressure based on the engine speed and the engine load, and controls the servo motor 20 or the solenoid valve 23 according to the map as usual during normal engine operation. Execute the boost pressure control. However, when the supercharging pressure control is executed in the same mode as during normal engine operation when the engine brake device is operated, the maximum braking force cannot always be obtained.

Therefore, in this case, the supercharging pressure control is executed in a mode different from that during normal operation of the engine when the apparatus is operating, so that the maximum braking force can be obtained. That is, here, when the auxiliary brake is required, the supercharging pressure control is executed based on the dedicated map. This is performed by the controller 8, which forms the supercharging pressure control means of the present invention.

The supercharging pressure control method at this time will be described below. When the driver turns on the engine brake switch, the engine brake device starts operating, the controller 8 turns on the operation switching valve 7 and the brake unit 6
And the exhaust valve 3a is minutely lifted. This is performed only when the clutch is engaged, the accelerator pedal is returned, and the fuel is cut without fuel injection. If these three conditions are not satisfied, the device will not operate. Also, when these conditions are not satisfied during operation of the apparatus, the operation of the apparatus is stopped. Thus, these conditions are priority conditions for the operation of the device. The minute lift of the exhaust valve 3a is performed over the entire cycle of the engine.

On the other hand, there are other conditions for operating the device. This is shown in FIG. First the controller 8, the engine coolant temperature T _W and reads the engine speed N _E (step 101), the water temperature T _W is the set value T _W0 or more (step 102), the engine speed N _E is the set value N _E1 below ( Step 103), set value N _E2 (<N
_E1 ) Only at the time of the above (step 104), the device is operated. In step 102, it is determined whether or not the engine 1 has been warmed up. If the engine 1 has not been warmed up, the apparatus is not operated. In step 103, it is determined whether or not the engine 1 is overrun.
Do not operate the device if it is overrun. Further, in step 104, it is determined whether or not the engine 1 is in idling operation, and the apparatus is not operated during idling operation. Thus, these conditions are substantive conditions based on the engine operating state.

During operation of the device, the hydraulic pressure generated by the oil pump is supplied to the brake unit 6 as it is or after the pressure is reduced. Since the generated oil pressure increases with an increase in the engine speed, the lift amount of the exhaust valve 3a increases as the engine speed increases. In this case, the lift amount can be made variable, and a compression pressure suitable for the engine speed can be obtained to obtain suitable brake characteristics.

By the way, when such a device is operated, FIG.
The supercharging pressure control is executed according to the condition (1). First, the controller 8 determines the supercharging pressure P _C , the loaded load value R, and the vehicle speed value V
Is read (step 201). Then the live load value R is compared with a set value R _1, determines whether the load (step 202). The controller 8 is in two stores a map of the supercharging pressure P _C based on the vehicle speed value V in to those at the time of loading and that under no load. Therefore, in step 202, R <
R ₁ , that is, when it is determined that there is no loading, the target supercharging pressure P is calculated in accordance with the map at the time of non-loading (step 203), and the supercharging pressure control is performed so as to become the target supercharging pressure P (step 204). ). Similarly, in step 202, R ≧
If R ₁ , that is, loading is determined, the target supercharging pressure P is calculated according to the map at the time of loading (step 205), and the supercharging pressure control is executed so as to reach the target supercharging pressure P (step 206). Naturally, a large braking force is required at the time of loading, so that the supercharging pressure is increased at the time of loading as compared to at the time of no loading. As a result, the supercharging pressure control dedicated to the brake is executed, and the maximum engine braking force optimal for the vehicle driving state can be obtained. Incidentally, this control is performed when the current supercharge pressure P _C is within the range of the map.

Here, when the engine 1 is running at low to medium speeds, the braking force may be increased by using the exhaust brake together. However, in this case, the compression temperature rises due to the increase of the back pressure, and the frictional wear of the valve seat increases. There is a problem of an increase in emission of particulate matter due to fuel oil or the like. In this device, the temperature of the compressed air can be reduced by the intercooler 15, whereby the air temperature when passing through the valve seat can be reduced, and the durability of the valve seat can be improved. Also, the amount of discharged particulate matter can be reduced.

Next, each characteristic of the present apparatus will be described.
FIG. 4 shows a compression brake cycle curve, that is, a relationship between the in-cylinder pressure and the stroke volume when the engine speed is constant (a so-called PV diagram). The solid line indicates the case of the present invention, and the broken line indicates the case of a non-supercharged naturally aspirated engine. According to the present invention, since the supercharging pressure control is performed optimally when the exhaust valve 5 is lifted, the in-cylinder pressure can be increased, the diagram area can be increased, and a large compression braking force can be obtained. If the supercharging pressure is changed, the compression pressure changes and the diagram area increases or decreases. Therefore, in the case of the present invention, it is possible to obtain an optimal braking force according to the vehicle driving state.

FIG. 5 shows the compression brake performance characteristics, that is, the average frictional effective pressure with respect to the engine speed. The solid line indicates the case of the present invention, the broken line indicates the case of the naturally aspirated engine, and the dashed line indicates the simple engine braking force when the compression brake is not used. Note that the friction average effective pressure is with respect to the flywheel axis. As can be seen, in the present invention, the friction average effective pressure is higher in the whole rotation range than in the case of the naturally aspirated engine. The friction average effective pressure can be changed between the solid line and the broken line by changing the supercharging pressure. In the high rotation range, a braking force can be easily obtained due to an increase in mechanical loss and the like. Therefore, it is preferable to lower the effective pressure and reduce the amount of heat generated by compression and the amount of heat radiated by the radiator.

FIG. 6 shows the compression brake horsepower characteristic, that is, the flywheel shaft friction horsepower with respect to the engine speed. The solid line indicates the present invention, the broken line indicates the naturally aspirated engine, and the dashed line indicates the engine braking force. As can be seen, the compression brake horsepower is improved over the entire rotation range. The friction horsepower can be changed between the solid line and the broken line by changing the supercharging pressure.

FIG. 7 shows the compression brake braking force curve, that is, the braking force with respect to the vehicle speed. The solid line is the case of the present invention, the broken line is the case of the naturally aspirated engine, and the one-dot chain line a,
b and c show running resistance force, respectively. Here, the shift position of the vehicle is overdrive (high top), the load capacity of the vehicle is constant, and a, b, and c are a%, b%, and c% (a
<B <c) indicates the running resistance of the vehicle during downhill running. Again, it can be seen that the present invention can obtain a high braking force, but especially in a region where the gradient is large, the running resistance increases, and the braking force tends to be insufficient with a naturally aspirated engine, the present invention can obtain sufficient braking force. Demonstrate high practicality.

FIG. 8 shows the compression brake deceleration curve, that is, the deceleration with respect to the vehicle speed. Each diagram is for the present case, the solid line indicates the maximum load, the dashed line indicates the no load,
The dashed line indicates the drive wheel lock limit. Here, the road surface gradient is 0%, and the shift position of the vehicle is overdrive. Although not shown, in the case of the naturally aspirated engine, the deceleration did not exceed the drive wheel lock limit at the time of maximum loading and no loading. However, according to the present invention, the lock limit may be exceeded when the vehicle is not loaded because a high braking force is obtained. Even in such a case, since the braking force can be changed in the present invention, it is possible to adjust so as not to exceed the lock limit and to obtain the maximum braking force.

Note that the present invention can adopt other embodiments. For example, the exhaust valve may be an exhaust valve dedicated to a brake (so-called third valve), and the supercharging pressure control method is not limited to the above-described method.

[0028]

In summary, the present invention exerts an excellent effect that a supercharging pressure control dedicated to a brake can be executed and a maximum braking force optimal for a vehicle driving state can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an engine brake device according to the present invention.

FIG. 2 is a flowchart showing the contents of device operating conditions.

FIG. 3 is a flowchart showing the contents of supercharging pressure control.

FIG. 4 is a graph showing a compression brake cycle curve.

FIG. 5 is a graph showing compression brake performance characteristics.

FIG. 6 is a graph showing compression brake horsepower characteristics.

FIG. 7 is a graph showing a compression brake braking force curve.

FIG. 8 is a graph showing a compression brake deceleration curve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Supercharger 3a Exhaust valve 8 Controller R Loading load value V Vehicle speed value

Claims (3)

[Claims] 1. An engine brake device applied to an engine having a supercharger and controlling opening and closing of an exhaust valve by supply and discharge of fluid pressure, wherein when the exhaust valve is opened, the mode is different from that during normal engine operation. An engine brake device comprising a supercharging pressure control means for performing supercharging pressure control of a supercharger. 2. The engine brake device according to claim 1, wherein said control means executes supercharging pressure control based on a loaded load of the vehicle. 3. The engine brake device according to claim 1, wherein said control means executes supercharging pressure control based on a vehicle speed.