Electric Pneumatic Handbrake System

Abstract

The invention relates to an electro-pneumatic handbrake system (10) for a vehicle with a spring-loaded brake, the electro-pneumatic handbrake system comprising: a pneumatic relay valve (11); a bistable solenoid valve (12) for controlling the relay valve (11); and a control unit (46) for controlling the bistable solenoid valve (12), wherein an outlet of the relay valve (11) is connected to a port (18) for the spring-loaded brake, and wherein an inlet of the bistable solenoid valve (12) is arranged for connection to a line (22) carrying a supply pressure, the electro-pneumatic handbrake system (10) further comprising a self-locking switching valve having a control input, which is arranged in front of the inlet of the bistable solenoid valve (12), wherein a) the self-locking switching valve (13) can be moved from a blocking position to a flow-through position against the force of a restoring element when there is sufficient pressure at its control input, and b) an outlet of the self-locking switching valve (13) is connected to the inlet of the bistable solenoid valve (12), and c) the control input of the self-locking switching valve (13) is further connected to a signal line via which a signal pressure can be fed as a control pressure to the control input at least for a short time, and d) the self-locking switching valve (13) connects its outlet to its inlet in its flow-through position, and e) the self-locking switching valve (13) connects its outlet (25) to a bleed-off outlet in its blocking position.

Description

Technical Field

[0001] . The present invention relates to an electro - pneumatic handbrake system. In particular, the present invention is an electro - pneumatic handbrake system comprising: a pneumatic relay valve; a bistable solenoid valve for controlling the relay valve; and a control unit for controlling the bistable solenoid valve, wherein the outlet of the relay valve is connected to a port for a spring - loaded brake, and wherein the inlet of the bistable solenoid valve is arranged to be connected to a line carrying the supply pressure. Background Art

[0002] . Modern commercial vehicles have pneumatic braking equipment with an electronic braking system. The pneumatic braking equipment includes spring - loaded brakes that act as locking brakes. These spring - loaded brakes are also known as parking brakes. The parking brakes act by spring force and can be released by venting the spring brake cylinder or locked by bleeding it.

[0003] . The spring brake cylinder can be combined with the service brake cylinder so that the spring - loaded brake and the service brake act on the same brake piston. Appropriate construction measures can be taken to avoid mechanical overload of the brake piston caused by the superposition of braking forces from the service brake and the spring brake. If the service brake is applied when the parking brake is engaged, the spring brake cylinder is vented at the same time to avoid superposition of braking forces.

[0004] . The valves for regulating the brake pressure are electronically controlled via the electronic braking system. For safety reasons, pneumatic control of the valves for regulating the brake pressure is also provided.

[0005] . The parking brake is also electronically controlled. By actuating the solenoid valve, the venting or bleeding of the spring brake cylinder is regulated. For safety reasons, the solenoid valve must always adopt a unique switching position, which must be maintained in the event of a power failure. Therefore, the solenoid valve is implemented as a bistable solenoid valve.

[0006] . The bistable solenoid valve can be part of a subsystem herein named the electro - pneumatic handbrake system. The electrical part of the electro - pneumatic handbrake system can be a subsystem of the electronic braking system. The electro - pneumatic handbrake system can be provided with a dedicated electronic control unit. However, the dedicated electronic control unit can also be integrated in the brake control unit or another control unit.

[0007] . The pneumatic part of the electro - pneumatic handbrake system of a motor vehicle is usually connected to brake circuit III, while brake circuits I and II include the service brakes. Brake circuit III usually also supplies the supply pressure to the trailer.

[0008] .On the one hand, there are the brake circuits I and II, and on the other hand, the brake circuit III, which are connected to each other via a so-called bleedback function. If the pressure in one of the brake circuits I and II drops, the pressure in the brake circuit III also drops, so that the spring brake cylinder is automatically bled and the spring-loaded brake becomes effective. With the bleedback function, the vehicle operator can apply the service brake several times to activate the parking brake, thus releasing the pressure in the brake circuits I and II, especially when the engine is switched off or the generation of compressed air stops.

[0009] .If the previously described situation occurs during driving, the bistable solenoid valve is in its driving position. This means that even after the vehicle has stopped, once the pressure in the brake circuit III is high enough again, the spring brake cylinder is vented and the parking brake is released. If the vehicle is parked on an inclined surface, the vehicle may start to move. Depending on the surroundings, this can lead to dangerous situations, for example, in the following cases:

[0010] .The electrical system continues to malfunction or fail. The operator keeps the engine running so that compressed air continues to be supplied and the pressure in the brake circuit increases again.

[0011] .The operator has switched off the engine before reducing the pressure in the brake circuit III by applying the service brake and actuating the bleedback function. After some time, the operator restarts the engine in order to activate the ventilation in the cab. The pressure in the brake circuit increases again.

[0012] .The operator leaves the cab with the engine running in order to check the electro-pneumatic parking brake.

[0013] .The operator leaves the vehicle. The mechanic starts the engine to heat the cab.

[0014] .In all these cases, the vehicle may start to move because the parking brake is vented again. This results in an unintentional movement of the vehicle. The above cases are an incomplete list of examples. Other cases with a similar potential for danger are possible. In all cases, the cause is the still open position of the bistable solenoid valve in the electro-pneumatic parking brake system. Summary of the Invention

[0015] .The object of the present invention is to create a system by means of which the above-mentioned dangerous situations can be avoided.

[0016] .To achieve this object, an electro-pneumatic handbrake system is provided for a vehicle with a spring-loaded brake, the electro-pneumatic handbrake system having: a pneumatic relay valve; a bistable solenoid valve for controlling the relay valve; and a control unit for controlling the bistable solenoid valve, wherein the outlet of the relay valve is connected to a port for the spring-loaded brake, and wherein the inlet of the bistable solenoid valve is arranged for connection to a line carrying a ventilation pressure. In particular, a self-locking switching valve with a control input is provided in front of the inlet of the bistable solenoid valve, wherein

[0017] .a) when there is sufficient pressure at the control input of the self-locking switching valve, the self-locking switching valve can move from the blocking position to the flow-through position against the force of the restoring element, and

[0018] .b) the outlet of the self-locking switching valve is connected to the inlet of the bistable solenoid valve, and

[0019] .c) the control input of the self-locking switching valve is also connected to a signal line via which

[0020] a signal pressure can be fed as a control pressure to the control input at least for a short time, and

[0021] .d) the self-locking switching valve connects its outlet to its inlet in its flow-through position, and

[0022] .e) the self-locking switching valve connects its outlet to a bleed outlet in its blocking position, wherein the bleed outlet of the self-locking switching valve is connected to the bleed outlet of the bistable solenoid valve via a first bleed line and a second bleed line connected to the first bleed line.

[0023] .Thus, the self-locking switching valve is arranged upstream of the bistable solenoid valve. In this context,

[0024] "self-locking" means that in the flow-through position and with sufficient pressure at the inlet and / or outlet, the switching valve locks in its flow-through position independently of the pressure at the control input. After the switching valve has taken its blocking position, sufficient pressure must be present at the control input in order to move the switching valve back to the flow-through position. Once the flow-through position has been obtained, the pressure at the control input is reduced again. Then, the switching valve is independent of the pressure at the control input. Thus, the self-locking switching valve prevents the ventilation of the spring brake cylinder, even when the bistable solenoid valve is still in the flow-through position.

[0025] . The control input of the self-locking switching valve can be controlled in different ways. For example, the brake system line carrying the supply pressure can be connected via a line to the control input of the self-locking switching valve. This line is switched by a solenoid valve provided that electrical energy is available and / or the solenoid valve is controlled by a control unit. The activation of the solenoid valve via the control unit can be triggered by an auxiliary condition implemented in the software of the control unit or selectively triggered by the operator.

[0026] . In a further aspect of the invention, the self-locking switching valve can assume its blocking position once the pressure at its outlet drops below a limit value. The self-locking function of the switching valve here is associated with the pressure at the outlet of the switching valve. In particular, the limit value is 1.2 to 2.5 bar, preferably 1.5 bar.

[0027] . As a result, no dedicated bleed-off outlet is required. The two vent lines can also be different segments of a single bleed line.

[0028] . In a further aspect of the invention, the first bleed line can be provided with a throttle valve. This prevents sudden bleeding when changing from the flow-through position to the blocking position of the self-locking switching valve. In this way, feedback can also be avoided.

[0029] . In a further aspect of the invention, the first bleed line and the second bleed line can be connected via a third bleed line to the bleed-off outlet of a relay valve. In this way, a common bleed system can be utilized.

[0030] . In a further aspect of the invention, the third bleed line or the second bleed line can be connected to a bleeding device. This is particularly applicable when the first bleed line is equipped with a throttle valve.

[0031] . In a further aspect of the invention, the input of the self-locking switching valve can be connected to the input of the relay valve. This allows these two inputs to be connected to a common line carrying the ventilation pressure. The ventilation pressure preferably corresponds to the pressure in brake circuit III (which is also named the parking brake circuit) or to the supply pressure in the vehicle braking system.

[0032] . In a further aspect of the invention, the self-locking switching valve can be a 2-position 3-way valve. Such valves are well-known, widely used and economical.

[0033] . In a further aspect of the invention, the bistable solenoid valve can be a 2-position 3-way valve. This type of valve is also widely used and economical.

[0034] . In a further aspect of the invention, the outlet of the bistable solenoid valve can be connected to the control input of the relay valve.

[0035] .In a further aspect of the invention, the electromagnetic switching valve can switch between the outlet of the bistable solenoid valve and the control input of the relay valve, so that the switching valve can be switched from a flow-through position to a blocking position. The switching valve is preferably a 2 / 2-way valve. By using an electronic switching valve, the pressure applied to the control input of the relay valve can be modulated. In this case, the bistable solenoid valve is only indirectly connected to the control input of the relay valve, i.e., via an intermediate connection of the electromagnetic switching valve.

[0036] .In a further aspect of the invention, the electromagnetic switching valve without current supply can be in the flow-through position. The switching valve is monostable and assumes the flow-through position, for example, in the case of a power failure.

[0037] .In a further aspect of the invention, a shuttle valve can be connected between the outlet of the bistable solenoid valve and the control input of the relay valve, where

[0038] .a) the outlet of the shuttle valve is connected to the control input of the relay valve, and

[0039] .b) the first inlet of the shuttle valve is directly or indirectly connected to the outlet of the bistable solenoid valve, and

[0040] .c) the second inlet of the shuttle valve is connected to the pressure inlet carrying the service brake pressure.

[0041] .At this time, the shuttle valve serves as an overload protection for the service brake, which is also equipped with a spring-loaded brake cylinder. Via the shuttle valve, the spring-loaded brake cylinder is increasingly vented as the service brake pressure increases, thus avoiding mechanical overload of the brake piston and / or other brake parts.

[0042] .In a further aspect of the invention, the bleed outlet of the self-locking switching valve can be directly bled to the atmosphere. Additionally, a throttle valve can be provided in the self-locking switching valve in the region of the bleed outlet.

[0043] .The subject matter of the invention also lies in an electronic braking system, i.e., an electronic braking system for a vehicle with a spring-loaded brake, which has the described electro-pneumatic parking brake system. The electro-pneumatic parking brake system according to the invention is preferably used in combination with an electronic braking system.

[0044] .Finally, the subject matter of the invention also lies in a vehicle, which has a pneumatic braking device, a spring-loaded brake, and the described electronic braking system. Description of the Drawings

[0045] .Further features of the invention can be found in the remaining description and the claims. The advantageous exemplary embodiments of the invention are explained below with the aid of the drawings, wherein:

[0046] .Figure 1 The circuit diagram of an electro - pneumatic hand - brake system in the driving position is shown,

[0047] . Figure 2 The circuit diagram of Figure 1 is shown, but in the parking position,

[0048] . Figure 3 The circuit diagram of a slightly supplemented one as shown in Figure 1 is shown, in the failure position after the driving position. Detailed Description of the Invention

[0049] . Figure 1 The circuit diagram of an electro - pneumatic hand - brake system 10 for a vehicle (not shown) with a spring - loaded brake is shown. The hand - brake system 10 is preferably a subsystem of an electronic brake system for a pneumatic braking device. The vehicle is preferably a motor vehicle.

[0050] . Important components of the hand - brake system 10 are the pneumatic relay valve 11, the bistable solenoid valve 12, and the self - locking pneumatic switching valve 13.

[0051] . The relay valve 11 is connected via an inlet 14 to a line 15 carrying the supply pressure. Starting from the outlet 16 of the relay valve 11, a line 17 leads to a port 18 for a spring brake cylinder (not shown).

[0052] As the relay valve 11 is switched, the spring brake cylinder is ventilated or at least can be ventilated.

[0053] . The bistable solenoid valve 12 is preferably a 2 - position 3 - way valve and can be switched electromagnetically between the flow - through positions shown in Figure 1 and Figure 3 and the blocked position shown in Figure 2 . In the flow - through position, the inlet 19 and the outlet 20 are connected. In the blocked position, the outlet 20 is connected to the bleed outlet 21.

[0054] . A second line 22 carrying the supply pressure is indirectly connected to the inlet 19. The lines 15 and 22 carrying the supply pressure can be connected to each other via a junction point 23. The supply pressure preferably corresponds to the supply pressure in the brake circuit provided for the hand - brake system 10. This is also called the parking brake circuit. The lines 15, 22 are connected to ports (not shown) of the parking brake circuit.

[0055] . The self - locking, pneumatic switching valve 13 has an inlet 24, an outlet 25, a bleed outlet 26, and a control input 27 and is preferably implemented as a 2 - position 3 - way valve. In the flow - through position, the switching valve 13 connects the line 22 to the inlet 19 of the bistable solenoid valve 12. In the blocked position of the switching valve 13, the outlet 25 is switched to the bleed outlet 26, seeFigure 3 . As long as there is a pressure above the limit value at the outlet 25, the switching valve 13 remains in the flow-through position against the force of the restoring element and self-locks there. The limit value is approximately 1.2 to 2.5 bar, preferably 1.5 bar.

[0056] . The control input 27 is connected to the pipeline 28, which can be supplied with a control pressure at least for a short time in a manner not shown, thus having the function of a signal line. As the control pressure, for example, the reserve pressure can be fed into the pipeline 28 via a switchable valve (not shown) at a suitable point in time. The valve can be switched manually, pneumatically or electromagnetically, preferably by an operator or automatically under defined conditions.

[0057] . The pressure applied to the outlet 20 of the solenoid valve 12 feeds the control input 29 of the relay valve 11. As long as the solenoid valve 12 and the switching valve 13 are each in the flow-through position and there is a ventilation pressure in each of the pipelines 15, 22, the relay valve 11 is switched so that the spring brake cylinder is ventilated via the port 18.

[0058] . If there is no pressure at the control input 29, the outlet 16 of the relay valve is connected to its bleed outlet 30. Then, the spring brake cylinder is bled via the port 18 and the relay valve 11, thus ensuring that the parking brake is activated.

[0059] . To modulate the pressure between the bistable solenoid valve 12 and the relay valve 11, an electromagnetic switching valve 31 is provided, which is preferably a 2-position 2-way valve and is in the flow-through position without current supply, as shown in all three figures. By means of the electromagnetic switching valve 31, the ventilation of the spring brake cylinder can be controlled step by step. In the shown flow-through position, the inlet 32 and the outlet 33 of the switching valve 31 are connected to each other.

[0060] . Located between the electromagnetic switching valve 31 and the relay valve 11 here is a shuttle valve 34, also known as an OR valve, which has two inlets 35, 36 and one outlet 37. The inlet 35 is connected to the outlet 33 of the switching valve 31, and the outlet 37 is connected to the control input 29 of the relay valve 11. The other inlet 36 is connected via a pipeline 38 to the port 39, which is supplied with service brake pressure. When the service brake is actuated, the service brake pressure enters the handbrake system 10 via the port 39. The higher pressure applied to the inlets 35, 36 is fed to the control input 29 of the relay valve 11 via the shuttle valve 34 respectively. This allows the spring brake cylinder to be ventilated depending on the actuation of the service brake, thus preventing mechanical overload of the brake.

[0061] . In Figure 1 the shown drive position, all four valves 11, 12, 13, 31 are in the flow-through position. The spring-loaded brake cylinder is pressure-ventilated via the port 18.

[0062] . In the parking position according to Figure 2 , the bistable solenoid valve 12 is in the blocked position, while the switching valve 13 and the switching valve 31 are preferably in the flow-through position. Due to the blocked position of the solenoid valve 12, the pressure at the outlet 20 is reduced via the bleed outlet 21. For this purpose, the bleed outlet 21 is connected to the bleed device 43 via the bleed line 40 and a further bleed line 41, 42. The bleed line 41 extends upward to the bleed outlet 30 of the relay valve 11 so that the bleed device 43 is also connected to the bleed outlet 30.

[0063] . The bleed outlet 26 of the self-locking switching valve 13 is connected to the bleed line 40 and / or the bleed line 41 via the bleed line 44. This also creates a connection from the bleed outlet 26 of the self-locking switching valve 13 to the bleed device 43.

[0064] . The bleed line 44 here is provided with a throttle valve 45. Thus, when the outlet 25 is bled via the bleed outlet 26 in the blocked position of the switching valve 13, the pressure in the bleed line 44 adjacent to the switching valve 13 is higher than the pressure in the bleed line 41.

[0065] . In another embodiment (not shown), the bleed outlet 26 leads to the atmosphere. The line 44 does not exist. The throttle valve can be integrated in the switching valve 13 so that the pressure at the outlet 25 does not drop too much during bleeding.

[0066] . In Figure 3 , a control unit (ECU) 46 is additionally shown. This is either specific to the handbrake system 10 or is a component of the brake control unit (not shown) or another electronic control unit in the associated vehicle. The control unit 46 here is used to control the functions of the bistable solenoid valve 12 and the electromagnetic switching valve 31. According to Figure 3 's switch state, it proceeds from the following situations:

[0067] . The handbrake system 10 is in the drive position, as shown in Figure 1 . The solenoid valve 12 and the switching valves 13, 31 are in the flow-through position. The operator has been informed that the electronic braking system has failed or that the electronic braking system has a complete or partial malfunction. Due to the malfunction, the parking brake can no longer be actively applied. For safety reasons, in such a case, the operator should use the service brake to stop the vehicle and then apply the service brake several times to reduce the pressure in the service brake circuit so that the bleed function also reduces the pressure in the parking brake circuit. This will bleed the spring brake cylinder.

[0068] . There is also a pressure drop in the region of the outlet 25 of the self-locking switching valve 13. This causes the switching valve 13 to move from its flow-through position to as shown in Figure 3The blocked position shown in [figure]. There is also no pressure at the control input 27 because the pressure is only fed into the line 28 upon manual or automatic actuation depending on specific conditions. This means that the handbrake system cannot automatically vent the spring brake cylinder and thus release the parking brake once sufficient supply pressure is available again. Instead, a pressure pulse at the control input 27 via the line 28 is first required to vent the parking brake cylinder again.

[0069] . In the handbrake system 10, the self-locking switching valve 13 has the function of a safety device when the above situation occurs. The accidental release of the parking brake caused by restarting the engine in the case of a corresponding accumulation of supply pressure is avoided. The parking brake remains activated until the control input 27 is activated by pressure via the line 28, in particular by intentional manual intervention or automatically under defined conditions.

[0070] . The control unit 46 is connected to the handbrake lever (not shown) for the operator. When the handbrake lever is actuated, the control unit 46 receives a command to activate or deactivate the parking brake.

[0071] . List of reference numerals (part of the description)

[0072] . 10 Electro-pneumatic handbrake system

[0073] . 11 Relay valve

[0074] . 12 Bistable solenoid valve

[0075] . 13 Self-locking switching valve

[0076] . 14 Relay valve inlet

[0077] . 15 Line

[0078] . 16 Relay valve outlet

[0079] . 17 Line

[0080] . 18 Port

[0081] . 19 Solenoid valve inlet

[0082] . 20 Solenoid valve outlet

[0083] . 21 Solenoid valve bleed outlet

[0084] . 22 Line

[0085] . 23 Junction point

[0086] . 24 Self-locking switching valve inlet

[0087] . 25 Self-locking switching valve outlet

[0088] .26 Self - retaining switching valve air release outlet

[0089] .27 Self - retaining switching valve control input terminal

[0090] .28 Pipeline

[0091] .29 Relay valve control input terminal

[0092] .30 Relay valve air release outlet

[0093] .31 Electromagnetic switching valve

[0094] .32 Self - retaining switching valve inlet

[0095] .33 Self - retaining switching valve outlet

[0096] .34 Shuttle valve

[0097] .35 Shuttle valve inlet

[0098] .36 Shuttle valve inlet

[0099] .37 Shuttle valve outlet

[0100] .38 Pipeline

[0101] .39 Port

[0102] .40 Air release pipeline

[0103] .41 Air release pipeline

[0104] .42 Air release pipeline

[0105] .43 Air release device

[0106] .44 Air release pipeline

[0107] .45 Throttle valve

[0108] .46 Control unit

Claims

1. An electro-pneumatic handbrake system (10) for a vehicle having a spring-loaded brake, The electric pneumatic handbrake system includes: a pneumatic relay valve (11); a bistable solenoid valve (12) for controlling the relay valve (11); and a control unit (46) for controlling the bistable solenoid valve (12), wherein an outlet of the relay valve (11) is connected to a port (18) for the spring-loaded brake, and wherein an inlet (19) of the bistable solenoid valve (12) is arranged to be connected to a line (22) carrying a venting pressure, and wherein a self-locking switching valve (13) having a control input (27) is provided in front of the inlet (19) of the bistable solenoid valve (12), wherein a) when there is sufficient pressure at the control input (27) of the self-locking switching valve (13), the self-locking switching valve (13) can move from a blocking position to a flow-through position against the force of a restoring element, b) an outlet of the self-locking switching valve (13) is connected to the inlet (19) of the bistable solenoid valve (12), c) the control input (27) of the self-locking switching valve (13) is also connected to a signal line (28) via which a signal pressure can be fed as a control pressure to the control input (27) at least for a short time, d) the self-locking switching valve (13) connects its outlet (25) to its inlet (24) in its flow-through position, and e) the self-locking switching valve (13) connects its outlet (25) to a venting outlet (26) in its blocking position, and characterized in that the venting outlet (26) of the self-locking switching valve (13) is connected to a venting outlet (21) of the bistable solenoid valve (12) via a first venting line (44) and a second venting line (40) connected to the first venting line.

2. The system according to claim 1, wherein Once the pressure at the outlet (25) of the self-locking switching valve (13) drops below a limit value, the self-locking switching valve (13) assumes its blocking position.

3. The system according to claim 1, characterized in that, The first venting line (44) is provided with a throttle valve (45).

4. The system according to any one of claims 1 to 3, characterized in that The first venting line (44) and the second venting line (40) are connected to a venting outlet (30) of the relay valve (11) via a third venting line (41).

5. The system according to claim 4, characterized in that, The third venting line (41) or the second venting line (40) is connected to a venting device (43).

6. The system according to any one of claims 1 to 3, characterized in that, An inlet (24) of the self-locking switching valve (13) is connected to an inlet (14) of the relay valve (11).

7. The system according to any one of claims 1 to 3, characterized in that The self-locking switching valve (13) is a 2-position 3-way shuttle valve.

8. The system according to any one of claims 1 to 3, characterized in that, The bistable solenoid valve (12) is a 2-position 3-way valve.

9. The system according to any one of claims 1 to 3, characterized in that, An outlet (20) of the bistable solenoid valve (12) is connected to a control input (29) of the relay valve (11).

10. The system according to claim 9, wherein, An electromagnetic switching valve (31) is connected between the outlet (20) of the bistable solenoid valve (12) and the control input (29) of the relay valve (11), and the switching valve (31) can be switched from a flow-through position to a blocking position.

11. The system according to claim 10, wherein The electromagnetic switching valve (31) is in the flow-through position when no current is supplied.

12. The system according to claim 9, wherein The shuttle valve (34) is connected between the outlet (20) of the bistable solenoid valve (12) and the control input (29) of the relay valve (11), wherein a) the outlet (37) of the shuttle valve (34) is connected to the control input (29) of the relay valve (11), and b) the first inlet (35) of the shuttle valve (34) is directly or indirectly connected to the outlet (20) of the bistable solenoid valve (12), and c) the second inlet (36) of the shuttle valve (34) is connected to a pressure inlet (39) carrying the service brake pressure.

13. The system according to any one of claims 1 to 3, characterized in that, The bleed outlet (26) of the self-locking switching valve (13) bleeds directly to the atmosphere.

14. An electronic braking system for a vehicle having spring-loaded brakes, the electronic braking system having an electro-pneumatic parking brake system (10) according to any one of claims 1 to 13.

15. A vehicle having pneumatic braking equipment, spring-loaded brakes, and an electronic braking system according to claim 14.

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