JPH025047Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a brake device for a vehicle.

Large vehicles such as trucks and tractors have a large dead weight and a large cargo weight when loaded.
Naturally, the brake load when trying to stop or when going downhill is also large. Therefore, if the service brake is used excessively, there is a risk of burnout or premature wear of the friction shoes and pads. For this reason, auxiliary brake devices that utilize the mechanical characteristics of the engine itself have been proposed for the purpose of supplementing the regular brake. One is the so-called exhaust brake device, which blocks the exhaust pipe of the engine and causes the piston to perform exhaust work to produce a braking effect when the vehicle is running under engine braking. The valve or a third valve provided separately from the normal intake valve and exhaust valve is opened near the compression top dead center of the piston when the vehicle is running under engine braking, and the compressed air inside the cylinder is released outside the cylinder. This is an engine braking device designed to discharge gas. In the latter brake device, the compressed air discharged not only when using the exhaust valve but also when using the third valve,
The pressurized air is normally discharged into the exhaust pipe via a pressurized air discharge passage that joins the exhaust port in the cylinder head or joins the exhaust manifold downstream of the exhaust port. On the other hand, the main purpose of improving engine output and fuel efficiency by recovering a part of engine exhaust gas retained by the engine is to use exhaust gas turbines and turbines that are driven by engine exhaust gases. As a result, turbochargers, which consist of a compressor that is driven and compresses the intake air of the engine, have come to be widely used. The present invention relates to an improvement of a brake system for a vehicle equipped with an engine brake system having the above-mentioned exhaust brake system that absorbs exhaust work and an exhaust valve or third valve that absorbs compression work.

Now, in this type of brake system, when the engine is running under engine braking and the engine speed is high, the number of times the piston is discharged during the exhaust stroke naturally increases, and the compressed air at the top dead center of the compression stroke increases. is released into the exhaust pipe the same number of times, so when the exhaust pipe is blocked by the exhaust brake valve, the pressure in the exhaust pipe may rise excessively. In this case, the pressure difference between the negative pressure inside the cylinder that occurs during the intake stroke of the piston and the high positive pressure inside the exhaust pipe overcomes the valve spring that normally biases the exhaust valve in the closing direction, and the valve drive mechanism Regardless of this, there is a risk that the exhaust valve may open and close on its own. If the exhaust valve opens and closes by itself, the severe impact when the valve closes will damage the valve seat, causing problems with engine durability, and in extreme cases, the push rod cup and ball may separate. Failure to do so may result in serious malfunction. In order to avoid such problems, for example, a notch is provided in a part of the exhaust brake valve so that the exhaust valve does not open and close automatically even when the engine rotates at high speed, which can occur when the vehicle is running under engine brake. Although it is necessary to limit its full closing, in this case, there is a disadvantage that the exhaust gas is not sufficiently blocked when the engine rotates at low speed, and the exhaust braking effect is reduced.

The present invention has been devised in view of the above, and includes a third valve or exhaust valve provided separately from the normal intake valve and exhaust valve in one or more cylinders of a vehicle engine when the vehicle is running under engine braking. The engine is configured to open near the top dead center of the piston's compression stroke to exhaust the compressed air in the cylinder, and is provided with an exhaust brake valve in the exhaust pipe of the engine to control the passage area of the exhaust pipe, When the engine is running under engine braking, the exhaust brake valve is almost fully closed in the low engine speed range, and the exhaust brake valve is partially opened in the high engine speed range to reduce the pressure in the exhaust pipe to the engine. The gist of this invention is a brake device for a vehicle, characterized in that it is configured to maintain a pressure below that at which an exhaust valve self-opens and closes.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Reference numeral 10 in the figure is a cylinder head of a multi-cylinder diesel engine of a vehicle (not shown), and only a single cylinder is shown in the figure for simplicity. 12 is a cylinder block (including the cylinder liner, of course), 14 is a piston, and 16 is a connecting rod. Above cylinder head 1
0 has an intake port 18 and an exhaust port 2.
0 is provided, and an intake valve 24 and an exhaust valve 26 are provided between each of these ports and the cylinder 22. Furthermore, the cylinder head 10 is provided with a third valve 28 for all or some of the cylinders of the engine.
A pressurized air discharge passage 30, which is opened and closed by the third valve, is connected to the exhaust port 20 within the cylinder head 10. 32, 34 and 36
is a valve spring that normally biases the intake valve 24, the exhaust valve 26, and the third valve 28 in the closing direction. The third valve 28 has a plunger 38 at its top, which is slidably fitted into the pressure oil cylinder 40. The pressure oil cylinders 40 are connected to an oil pump 44 via a distribution valve 42 that supplies pressure oil to each pressure oil cylinder 40 near the compression top dead center of the cylinder, which is equipped with a third valve 28. 42
is controlled by a first control box 46 which detects that the vehicle is in the braking state and instructs the distribution valve. 48 is an exhaust gas turbine 50 driven by engine exhaust gas.
and compressor 5 connected to the same gas turbine.
A known turbocharger consisting of:
The exhaust gas turbine 50 is connected to the exhaust port 20 of each cylinder of the engine via an exhaust pipe 54, and similarly the pressurized air outlet of the compressor 52 is connected to the exhaust port 20 of each cylinder of the engine through an exhaust pipe 54.
It is connected to the intake port 18 via an intake pipe 56. Reference numeral 58 denotes an exhaust brake valve disposed within the exhaust pipe 54, which is shown as a butterfly valve in the illustrated embodiment, but may of course be a slide valve or a rotary valve. 60 is a pneumatic actuator operatively connected to the exhaust brake valve 58 to open and close the valve; 62 is a control valve that supplies and discharges operating compressed air to the actuator 60; and 64 is connected to the control valve 62. compressed air tank. 66 is a second control box that controls the operation of the control valve 62,
The actuator 60 detects that the vehicle is running under engine braking and opens the control valve 62.
The actuator 6 is activated via the control valve 62 by detecting the engine rotation speed at that time.
0 stroke amount, that is, the opening degree of the exhaust brake valve 58.

The first and second control boxes 46
and 66, one means for detecting that the vehicle is in an engine braking state is as follows:
An electric circuit is known in which an accelerator switch, a clutch switch, and, if desired, a manually operated switch are connected in series to a power source, such as an on-vehicle battery. Also, as a device for detecting the rotational speed of an engine, a device consisting of a radial protrusion fixed to an arbitrary shaft such as a camshaft that rotates in conjunction with the crankshaft, and an electromagnetic coil placed opposite the protrusion is well known. and is widely used in practice.

In the above device, when the vehicle is running under engine braking and the engine speed is low, the control valve 62 is operated in response to a command from the second control box 66 to supply compressed air from the compressed air tank 64. is supplied to the actuator 60, and the exhaust brake valve 58 is substantially fully closed as shown by the dotted line in the figure. Therefore, the exhaust pipe 54 of the engine is sufficiently blocked, the exhaust work of the piston 14 is large, and a sufficient exhaust braking effect is produced. On the other hand, even if the vehicle is running under engine braking, if the engine speed at that time is higher than a predetermined speed, the actuator 60 operates in the same manner according to the command from the second control box 66. Its stroke is limited, and the exhaust brake valve 58 is held at a partially opened degree, which is slightly more open than fully closed. On the other hand, when the vehicle is running under engine braking regardless of the engine speed, the distribution valve 42 is operated by a command from the first control box 46, and the piston of each cylinder equipped with the third valve 28 is activated. When the compression reaches near the top dead center, pressure oil is supplied from the pump 44 to the pressure oil cylinder 40 and the plunger 38 is pushed down. This overcomes the valve spring 36 and opens the third valve 28.
Compressed air within the cylinder 22 is discharged from the pressurized air discharge passage 30 through the exhaust port 20 into the exhaust pipe 54.

Therefore, if the exhaust brake valve 58 is substantially fully closed while the engine is running under engine braking and the engine speed is high, the number of exhaust gases by the piston 14 will naturally increase in proportion to the engine speed, and at the same time the third Naturally, the number of times the compressed air is discharged from the valve 28 is also large, so the pressure in the exhaust pipe 54 increases rapidly. Therefore, when the engine speed exceeds a certain limit, the opening force of the exhaust valve 26 due to the pressure difference between the negative pressure inside the cylinder 22 generated during the intake stroke and the high positive pressure inside the exhaust pipe 54 is applied to the valve spring 34. Overcoming the valve closing force of The cup and ball of the push rod may even separate, but according to the device of the present invention, when the engine speed is high, the exhaust brake valve 58 is not fully closed, and the exhaust brake valve 58 is not fully closed. Since the opening degree is controlled such that the pressure below the limit pressure that causes the self-opening and closing of the exhaust valve 26 is maintained in the exhaust pipe 54, problems caused by the self-opening and closing of the exhaust valve can be reliably prevented. and,
If the engine speed drops as a result of engine braking and exhaust braking, the second
In response to the command from the control box 66, the actuator 60 further moves to a full stroke via the control valve 62, and the exhaust brake valve 58 is substantially fully closed, thereby providing a sufficient exhaust brake effect.

Furthermore, in the preferred embodiment of the present invention, that is, in the case of a turbocharged engine, the partial opening of the exhaust brake valve 58 causes a part of the compressed air in the exhaust pipe 54 to pass through the exhaust brake valve 58 and be exhausted. Acting on the gas turbine 50, the compressor 52
is driven, and the intake pressure supplied into the cylinder 22 through the intake pipe 56 increases. For this reason, the compression work in the compression stroke of the piston 14 increases,
This results in the advantage that the engine braking effect is further increased.

Note that in the above embodiment, the actuator 6
Although a pneumatic actuator is shown as an example, it is clear that an electric or electro-mechanical actuator, such as a reversible motor and a screw/nut type drive device, may be used instead. Furthermore, in the above embodiment, since the engine rotation speed and the pressure in the exhaust pipe 54 are approximately proportional, the engine rotation speed is introduced into the second control box 66 as a control factor, but the pressure in the exhaust pipe 54 is Alternatively, the displacement of the bellows may be directly detected by, for example, a bellows, and the displacement of the bellows may be introduced into the control box 66 as an electrical or mechanical quantity signal. Furthermore, it is clear that the portions of the first and second control boxes 46, 66 that detect the engine braking state of the vehicle can be shared. Note that the driving means for the third valve 28 is not limited to the illustrated structure;
Of course, it is also possible to easily adopt a cam drive similar to the intake and exhaust valves, and even if the exhaust valve 26 is opened near the top dead center of the compression stroke in place of the third valve 28, the same effect as in the above embodiment can be achieved. The same effect can be obtained.

As described above, the brake system for a vehicle according to the present invention includes a third valve or exhaust valve provided separately from the normal intake valve and exhaust valve in one or more cylinders of the vehicle engine. During engine braking, the exhaust brake valve is configured to open near the top dead center of the piston's compression stroke to exhaust the compressed air in the cylinder, and is installed in the exhaust pipe of the engine to control the passage area of the exhaust pipe. When the vehicle is running under engine braking, the exhaust brake valve is substantially fully closed in the low engine speed range, and the exhaust brake valve is partially opened in the high engine speed range to reduce the amount of air in the exhaust pipe. The exhaust brake valve is characterized by being configured to maintain the pressure below the pressure at which the exhaust valve of the engine self-opens and closes, and when the vehicle is running under engine braking, the exhaust brake valve and the third valve work to achieve an effective This is extremely advantageous because it generates a braking effect and controls the opening degree of the exhaust brake valve according to the engine speed to reliably prevent damage to the engine.

[Brief explanation of the drawing]

The accompanying drawings are schematic layout diagrams showing one embodiment of the present invention. 10...Cylinder head, 12...Cylinder block, 14...Piston, 24...Intake valve, 2
6... Exhaust valve, 28... Third valve, 38... Plunger, 40... Pressure oil cylinder, 42... Pressure oil distribution valve, 46... First control box, 48...
...Turbocharger, 54...Exhaust pipe, 58...
Exhaust brake valve, 60...actuator, 62
...Control valve, 66...Second control box.

Claims (1)

[Scope of utility model registration request] A third valve or exhaust valve provided separately from the normal intake valve and exhaust valve in one or more cylinders of the vehicle engine, when the vehicle is running under engine braking,
The structure is configured to open near the top dead center of the piston's compression stroke to exhaust the compressed air in the cylinder, and an exhaust brake valve is provided in the exhaust pipe of the engine to control the passage area of the exhaust pipe. During engine braking, the exhaust brake valve is almost fully closed in the low engine speed range, and the exhaust brake valve is partially opened in the high engine speed range to reduce the pressure in the exhaust pipe to the engine exhaust. 1. A brake device for a vehicle, characterized in that the valve is configured to maintain a pressure below that at which self-opening and closing occurs.