JPH0320511Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a compression work absorption type engine braking device, and aims at a rational and efficient engine braking device.

Freight vehicles equipped with relatively high-output diesel engines are known to incorporate exhaust braking devices and compression work absorption type engine braking devices to assist in braking force during loading.

The compression work absorption type engine braking device is
When the driver takes his foot off the access pedal while the vehicle is running, the fuel supply to the combustion chamber is stopped and the rotation of the drive wheels is actively suppressed by the resistance during the compression stroke of the piston. It is. this is,
Just before the end of the compression stroke, the high-pressure combustion chamber is communicated with the exhaust manifold side to discharge intake air, and in other words, the combustion chamber is communicated with the exhaust manifold side from near the end of the compression stroke of the piston to the middle of the expansion stroke.

By the way, in recent years, in order to increase the filling efficiency of air supply in the low rotational speed range of the engine, variable blade type nozzle vanes (guide vanes) that can change the area after the turbine nozzle in accordance with the engine rotational speed have been introduced. Hariable geometry turbo superchargers (hereinafter referred to as VG turbos) have come into use. In other words, in the low-speed range of the engine, the turbine speed is increased to provide sufficient supercharging, while in the high-speed range of the engine, the turbine nozzle opening area is expanded to prevent seizure due to overspeeding of the turbine. It's summery.

The purpose of the present invention is to provide a compression work-type engine braking device that can perform engine braking rationally and efficiently by utilizing the characteristics of this VG turbo.

The configuration of the engine braking device of the present invention that can achieve this purpose includes a turbo supercharger that can arbitrarily change the nozzle opening area of the turbine, and an exhaust brake provided in the exhaust passage downstream of the turbo supercharger. an exhaust brake switch for operating the exhaust brake device; and an exhaust brake switch for determining an engine brake state in which the exhaust brake switch is not operated, and for determining an engine brake state in which the exhaust brake switch is not operated, and for controlling the nozzle so that the nozzle opening area of the turbine is narrowed in the engine brake state. a control device for controlling the operation of the regulating means and stopping the supply of fuel to the combustion chamber of the engine; and the control device is provided such that both ends thereof can block an auxiliary exhaust passage communicating with the combustion chamber and the exhaust manifold. and an auxiliary exhaust valve whose operation is controlled by the auxiliary exhaust valve to open the auxiliary exhaust passage from near the end of the compression stroke of the piston of the engine to the expansion stroke during the engine braking.

Therefore, according to the present invention, when it is desired to apply engine braking, the supply of fuel to the combustion chamber is stopped, while the nozzle opening area of the turbine of the turbocharger is narrowed to rotate the turbine at high speed, thereby improving the filling efficiency of the intake air. Since the resistance is increased to increase the resistance during the compression stroke of the piston, the engine brake can be used efficiently. Furthermore, by narrowing down the nozzle opening area of the turbine, the pressure in the exhaust manifold increases and an exhaust brake effect can also be obtained. Furthermore, since the boost pressure increases due to supercharging, the pressure regulating lift of the exhaust valve during the intake stroke of the piston, which occurs in general engine braking, is less likely to occur. Moreover, when the accelerator pedal is pressed from a state of engine braking, acceleration is improved because the turbine is rotating at high speed, making it possible to improve accelerator response. Furthermore, by operating the exhaust brake switch, it is possible to switch between the braking force produced by the engine brake and the braking force produced by the exhaust brake.

The following is a first example showing the schematic structure of the main parts of an embodiment of the engine braking device according to the present invention.
2, which shows the opening timing of each valve, and FIG. 3, which shows the engine brake determination procedure.

As shown in FIG. 1, an exhaust manifold 13 communicates with the combustion chamber 12 of the engine via an exhaust valve 11.
Nozzle vanes 16 that blow exhaust gas to the turbine 15 of the VG turbo 14 are arranged radially at the outlet end of the VG turbo 14 . I'm starting to be able to do it. That is, by operating the nozzle adjustment means and changing the inclination angle of the nozzle vanes 16, the interval between adjacent nozzle vanes 16 (nozzle opening area) is changed, and the flow velocity of the exhaust gas passing therethrough can be freely changed.

Therefore, if the interval between the nozzle vanes 16 is narrowed to increase the flow velocity of the exhaust gas passing through the turbine 15, the VG
The turbine 15, which is coaxially integrated with the compressor 17 of the turbo 14, rotates at high speed and the intake manifold 18
By increasing the boost pressure of the air supply inside the engine and conversely widening the interval between the nozzle vanes 16 to reduce the flow velocity of the exhaust gas passing through the turbine 15, it is possible to prevent the turbine 15 from rotating at an abnormally high speed.

The operation of the above-mentioned nozzle adjustment means is controlled by a control device (not shown), and normally the distance between the nozzle vanes 16 is gradually changed in accordance with the engine speed. Specifically, as the engine speed increases, the interval between the nozzle vanes 16 increases, which prevents the VG turbo 14 from over-rotating in the high engine speed range and increases the effectiveness of the VG turbo 14 in the low engine speed range. We are trying to utilize it.

In addition to the exhaust manifold 13 partitioned off through the intake valve 19, the combustion chamber 12 has an auxiliary exhaust passage 20 communicating with the exhaust manifold through the auxiliary exhaust valve 21.
The auxiliary exhaust valve 21 is opened by the control device only when the engine brake is activated.

That is, as shown in FIG. 2, the intake valve 19 is open from just before the end of the exhaust stroke to just after the start of the compression stroke, while the exhaust valve 11 is open from just before the end of the expansion stroke to just after the start of the intake stroke. . The opening timings of these intake valves 19 and exhaust valves 11 remain the same as before, and they are always opened and closed at these timings while the engine is operating. However, the auxiliary exhaust valve 21 is operated by the valve driving means only during engine braking, when the operation of the fuel injection device (not shown) is stopped by the valve driving means (not shown), and the supply of fuel to the combustion chamber 12 is cut off. In this embodiment, the valve is set to open from near the end of the compression stroke of the piston 22 to the middle of the expansion stroke.

This determination of engine braking is made by the control device based on signals from the clutch switch 23, vehicle speed sensor 24, and accelerator switch 25, but in this embodiment, the VG Exhaust passage 2 on the downstream side of the turbo 14
Since an exhaust brake device (not shown) is incorporated in the engine 6, operation of the exhaust brake device or engine brake device can be selectively switched by turning on/off the exhaust brake switch 27. Therefore, if an exhaust brake device is not provided, the exhaust brake switch 27
It is possible to process the operation of the engine braking system without determining whether the engine brake is on or not.

Therefore, as shown in FIG. 3, the clutch (not shown) interposed between the engine and the transmission (not shown) is in a connected state in which the clutch switch 23 is turned off, and the detection from the vehicle speed sensor 24 is Based on the signal, the vehicle is running (vehicle speed V>
0), when the driver takes his foot off the accelerator pedal (not shown) and the accelerator switch 25 is turned off, and the exhaust brake switch 27 is not operated and is in the off state, the control device It is determined that the engine is in a braking state, and the nozzle adjusting means and valve driving means are operated, and the operation of the fuel injection device is stopped.

As a result, the opening degree of the nozzle vane 16 becomes smaller, the compressor 17 rotates at high speed together with the turbine 15, and high-pressure intake air is sent into the combustion chamber 12 during the intake stroke of the piston 22. becomes resistance,
It becomes possible to use highly efficient engine braking. Further, by turning the exhaust brake switch on/off depending on the driving condition of the vehicle, the driver can arbitrarily switch between the braking force of the exhaust brake device and the braking force of the engine brake device.

[Brief explanation of the drawing]

Fig. 1 is a mechanical conceptual diagram showing the general structure of the main parts of the engine braking device according to the present invention, Fig. 2 is a valve opening stroke diagram showing the opening/closing timing of the intake valve, exhaust valve, and auxiliary exhaust valve, respectively, and Fig. 3 2 is a flowchart showing a procedure for determining engine braking. Also, in the figure, 11 is an exhaust valve, 12 is a combustion chamber, 13 is an exhaust manifold, 14 is a VG turbo,
15 is a turbine, 16 is a nozzle vane, 17 is a compressor, 18 is an intake manifold, 19 is an intake valve, 20 is an auxiliary exhaust passage, 21 is an auxiliary exhaust valve, 2
2 is a piston, 23 is a clutch switch, 24 is a vehicle speed sensor, 25 is an accelerator switch, and 27 is an exhaust brake switch.

Claims (1)

[Scope of utility model registration request] A turbo supercharger that can arbitrarily change the nozzle opening area of the turbine, an exhaust brake device installed in the exhaust passage on the downstream side of this turbo supercharger, an exhaust brake switch that operates this exhaust brake device, and an exhaust brake switch that operates this exhaust brake device. Determining an engine braking state in which a brake switch is not operated, and controlling the operation of the nozzle adjusting means so that the nozzle opening area of the turbine is narrowed in this engine braking state, and supplying fuel to the combustion chamber of the engine. a control device for stopping a compression stroke of a piston of the engine during engine braking; An engine braking device comprising: an auxiliary exhaust valve that opens the auxiliary exhaust passage from near the end to the expansion stroke.