Patent Application
20230265936
This application claims priority under 35 U.S.C. § 119 from European Patent Application No. 22158477.4, filed on Feb. 24, 2022, and European Patent Application No. 22214446.1, filed on Dec. 19, 2022, the entire disclosures of which are herein expressly incorporated by reference.
The present application relates to a bi-stable valve assembly, which can for example be used in a parking brake system, in particular for commercial vehicles or utility vehicles.
Commercial vehicles and utility vehicles have a parking brake, in particular a parking brake of a trailer. Such brake is usually actuated by a parking brake actuator which has a spring, and the parking brake is actuated if the spring presses brake pads against the brake disc or blocks a drum of a drum brake. A release of the parking brake can be performed if pressurized air is introduced into the parking brake actuator, when the pressurized air is able to overcome the force of the spring, so that the spring is moved in its tensioned state, and the brake pads are moved away from the brake discs or drum of a drum brake are unblocked.
Bi-stable parking brake valves are known from prior art, in particular electrically actuated valves being adapted to connect a parking brake selectively to supply pressure or atmospheric pressure, in order to actuate or release the parking brake.
From prior art, document EP 3 150 450 A1 is known, disclosing a vehicle braking system comprising a supply line which is adapted to be connected to a supply of pressurized fluid, a pressurized fluid reservoir, a parking brake actuator assembly including a brake actuator having a spring brake chamber, a pilot operated emergency brake apply valve with an inlet which is connected to the pressurized fluid reservoir, an outlet which is connected to the spring brake chamber by a spring brake line, and a control inlet connected to an emergency braking control line. The emergency brake apply valve is movable in accordance with the pressure at its control inlet between a first position in which its inlet is connected to its outlet and a second position in which its inlet is closed and its outlet vents to a low pressure region.
The spring brake chamber is operable such that the supply of pressurized fluid to the spring brake chamber causes the brake actuator to move to a brake release position and the release of pressurized fluid from the spring brake chamber causes the brake actuator to move a brake apply position. Further, a pressure transducer is provided in the emergency braking control line, and when the supply line is pressurized, the pressure sensor is directly connected to the pressurized fluid reservoir.
Furthermore, document EP 2 207 260 A1 is known from prior art, in which the parking brake vale has a movable piston loaded by a spring, and the piston has two coaxial piston faces which delimit the first space and the second space. The first space, dependent on the position of the piston, can be impacted with the supply pressure, atmospheric pressure or a pressure level lying between these two pressures. The pressures can be fed to the outlet of the parking brake valve, and the second space can be connected by an electrically actuated valve, selectively to increase pressure or atmospheric pressure.
However, for such system, numerous electrically actuated relay valves or solenoid valves are required in order to control the parking brake valve and also the parking brake, which is regularly a spring brake. Such parking brake is furthermore not safe against malfunction or accidental actuation, caused by which a trailer might roll away. Furthermore, such system is not safe against emergency actuation, which could occur during driving and which would lead to the blocking of the wheels during driving.
It is hence a technical problem of the present application to provide a valve arrangement, in particular a parking brake valve, which is only pneumatically actuated, reduces space, wiring and solenoid valves. Another problem can be seen in an easy actuation of the valve arrangement, in particular parking brake valve, in particular when a trailer is coupled to a commercial vehicle or release from it.
The technical problem of the present application is solved by a valve arrangement according to the independent claims. Further advantageous embodiments of the present application are subject-matters of the dependent claims.
The valve arrangement according to the present invention comprises the following features:
A differential piston which comprises a first section and a second section, wherein the second section has a smaller diameter compared to the first section, but where there is a fluidic connection between the first section and the second section. Furthermore, the valve arrangement comprises a housing with a bore, in which the differential piston is adapted to move. The bore has at least two sections, wherein the first section corresponds to the diameter of the first section of the differential piston, and the second section corresponds to the diameter of the second section of the differential piston. A step is formed between the first section and the second section of the bore.
A first passage and a second passage are arranged and axially spaced within the bore, and a third passage is also arranged in or next to the second section of the bore. When the differential piston is in the first end position, the second section of the differential piston rests against the step, and a connection between the first passage and the second passage within the bore is provided.
When the differential piston is in the second end position, a connection of the first passage and the second passage within the bore is blocked.
If the connection of the first passage and the second passage within the bore is blocked, this is a so-called safe park position, if the valve is used in a parking brake system. When the differential piston is in the first end position and the connection of the first passage and the second passage is provided within the bore, said position can be used for the driving position if used in a parking brake system.
The first section with the bigger diameter is highly throttled as fluid can only be delivered to this part via a throttled fluidic connection, where the part with a smaller diameter is not throttled (as the third port is provided in the bore close to this section). If there is a short pressure impulse in the third passage, the piston is switched from the first end position to the second position due to the forces of the pressure on the differential piston, i.e. its second side. However, if the pressure impulse is long enough, the second section of the bore is filled with pressurized air by the throttled fluidic connection (through the differential piston), and the pressure will act on the first section of the differential piston, which however has a larger area compared to the second section. Hence, the piston moves to the first end position again.
The third passage has the function of a pilot port or control port, which can be controlled by only one solenoid valve, and only the switching time of the solenoid valve is decisive for the position into which the differential piston is moved. The advantage is that the only one solenoid valve is required to switch the piston from one position to the other position. Due to the necessity of only one solenoid valve, less wiring is necessary for the valve. It is used as a safety valve for a parking brake, such valve arrangement is more compact and less prone to malfunction (for example be defects of wiring, solenoid valves or other valves).
Preferably, there is an additional fourth passage arranged in the first section of the bore, which allows the insertion of pressurized fluid into the first section of the bore.
With such arrangement, the position of the differential piston can be pushed from the second end position to the first end position (independent of a pressure in the third passage), hence providing a connection of the first passage to the second passage within the bore.
When used in a parking brake system, such arrangement is used if a manual reset is desired, in particular if a trailer has to be moved. Furthermore, if no pressure signal from the third passage is available, the fourth passage can at least change the position of the differential piston from the second end position and the first end position.
Preferably, the differential piston further comprises a third section, wherein when the differential piston is in a first end position, the third section of the differential piston provides a connection of the passage and the second passage within the bore, and wherein, when the differential piston is in the second end position, the third section of the differential piston blocks a connection of the first passage and the second passage within the bore.
Such third section of the differential piston can be realized very easily, as the differential piston is a non-complex element. Further, the blocking and connecting of the connection between the first passage and the second passage is very easy and very safe.
Preferably, the third section of the differential piston has a smaller diameter compared to the first/second section of the differential piston and/or the first/second section of the bore (depending on whether the third section of the differential piston is arranged next to/within the first or second section of the differential piston).
There is a space within the bore not being blocked by a part of the differential piston, which can hence provide a connection of the first port and the second passage.
Again, such a solution is very easy and inexpensive to fabricate.
Alternatively, an axial groove is arranged in the third section of the differential piston. When the differential piston is in a first end position, the axial groove is arranged covering the first port and the second port, and the axial groove can establish a connection between the first port and the second port.
Preferably, the fourth passage is connected to a fourth port via a first check valve, which only allows a flow from the fourth port to the fourth passage.
Herein, it can be ensured that no pressurized air will leave the bore through the fourth passage, and it can be guaranteed that only pressurized air enters the fourth passage in one direction (i.e. towards the bore), that means only if the differential piston should be moved from the second end position to the first end position.
Preferably, the first port and the second port are connected outside of the bore by a second check valve, which only allows a flow of pressurized air from the second passage to the first passage. However, there is a bypass which is controlled by the position of the differential piston.
The valve can be used to disable the flow in one direction (between the first passage and the second passage), but flow in the other direction is possible through the bore if the differential piston is in the first end position. In other words: When the differential piston is in a first end position, a connection of the first port and the second port is provided within the bore. Hence, a bypass of the second check valve is enabled. In a second end position of the differential piston, said bypass is blocked, and a fluid can only flow from the second passage to the first passage, but not in the reverse direction.
Such a valve can switch into two positions (enabling connection of the first passage and the second passage in one flow direction, wherein flow in the other flow direction is always possible) with only one solenoid valve, which is very easy and cheap to implement. Wiring and control of a solenoid valve can be minimized. Such a valve is in particular useful for safety valves for a parking brake.
Preferably, the bore, the differential piston and the first check valve, optionally also the second check valve, are accommodated in a common housing.
This reduces the wiring necessities even more, and the first check valve does not need any more wiring, and furthermore, a very compact valve arrangement is possible.
Preferably, the fluidic connection between the first section and the second section of the differential piston is realized by a channel and/or a hollow pin through the differential piston.
More preferably, the channel and/or the hollow pin in the differential piston is or are the only fluidic connection between the first section and the second section of the bore, independent in which end position the differential piston is.
That means that fluid from the third passage, being connected to the a pilot/control port, cannot be lead to the first passage or the second passage. Hence, two different pressure levels can be realized within the valve, without interfering with each other.
Preferably, the diameter of the channel and/or a hollow pin in the differential piston 2 is below 5 mm, preferably below 3 mm, even more preferably below 1.5 mm, and/or the ratio of the width of the channel and/or hollow pin on the one hand and the diameter of the second section of the differential piston on the other hand is below 1:5, more preferably below 1:8, even more preferably below 1:10 and furthermore preferably below 1:20.
Hence, only a very small hole has to be drilled, easily realizing the throttling of air flowing to the second section of the bore which will then act against a second section of the differential piston.
Furthermore, the hollow pin has a throttle functionality-for example, an air pulse of larger than 0 m/s up to 10 m/s will push the differential piston from the first end position into the second end position, whereas an air pulse of 20 m/s or longer will push the differential piston from the second end position to the first end position. This is realized as at first, only the small side of the differential piston is pressurized, and with the pressure force of the pulse, the differential piston is moved to the second end position. However, if the air pulse is long enough, the pressure can equilibrate within the whole bore (through channel/hollow pin), as it will get through the hollow pin to the side where the larger area of the differential piston rests. As there is a larger area which can interact with the pressure, the differential piston will move back again to the first end position.
Preferably, a locking mechanism pre-tensioned by a spring is provided in the bore, and the locking mechanism is adapted to be releasably pressed against the differential piston.
Such locking is preferably done in the first end position, which may be used as the driving position if used in a parking brake system. Said locking means enables a clearer differentiation of situations of pulses of pressurized air through the third port—as a longer pulse of pressurized air is needed to move the differential piston from the second end position to the first end position compared to a state without a locking means—hence, there can be a clear differentiation with regard to the length of the air pulses, without two states interfering with each other.
Preferably, the pre-tensioning of the spring can be adjusted by a screw.
That enables the adjusting of the required durations of an air pulse for switching off the differential piston between its two end positions even more.
Preferably, the third passage is connected to the third port, through which fluid pulses of different ranges are insertable. Such fluid is a control port, which is connectable via an electronic brake system.
Preferably, the valve arrangement is integrally formed with an electronic brake control module.
Such embodiment is very easy to implement, and two housings are not needed in this case.
Preferably, the first section of the bore and the third passage are connected via an internal connection, wherein a third check valve is provided within an internal connection, only allowing the flow of air from the first section of the bore to the third passage, wherein the internal connection optionally leads through an internal pocket.
This allows the exhaust of air from the first section of the bore in order to equilibrate the pressures on both sides of the differential piston. The internal pocket increases the air volume in the first section of the bore, reduces pressure peaks there and allows a more robust operation even with short pressure signals through the third passage.
Preferably, a first port is connected to the first passage, and a second port is connected to the second passage. The ports allow the communication with other components, e.g. of a parking brake system.
Preferably, the first port is connected to a park and shunt valve, the second port is connected to an electronic brake module, and the third port is connected to a control port. Only one solenoid valve in the electronic brake module is necessary, and the state of the differential piston within the valve arrangement is only controlled by the duration of the air pulse by the third passage.
Preferably, a double-check valve is further provided, one side of the double-check valve is connected to the third port, and the other side of the double-check valve is connected to the second passage, and the second port is connected with either the second passage or the third port by the double-check valve. The second port is connected to the second passage of the pressure and the second passage is higher compared to the third port, and the second port is connected with the third port of the pressure and the third port is higher compared to the second passage.
That means, if the pressure in the second passage is decreasing too much (e.g. by a leak though which pressure can escape), this pressure signal may be overwritten if there is still a control signal in the third port. This signal would be provided continuously, not only as a short, pressurized air pulse. Hence, if used as a parking brake, the parking brake will not actuate during the trailer is driving.
Previously, the double-check valve is provided in the same housing as the differential piston.
Such a solution is very compact and easy to manufacture.
Preferably, the first port is connected to a park and shunt valve, the second port is connected to an electronic brake module, and the third port is connected to a control port. Only one solenoid valve in the electronic brake module is necessary, and the state of the differential piston within the valve arrangement is only controlled by the duration of the air pulse by the third passage.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.
In
The axial length of the first section 2a of the differential piston 2 is smaller compared to the first section 5a of the bore 5—so that the differential piston 2 can move within the bore 5.
Within the housing 4, a first port 12, a second port 13 and a third port 14 are visible. The first port 12 is connected to a first passage 6, the second port 13 is connected to a second passage 7, and the third port 14 is connected to a third passage 8.
The first passage 6 and the second passage 7 are connected with the second section 5b of the bore 5. In
In the first end position (not shown in
Furthermore, there is a second check valve 11 arranged between the first passage 6 and the second passage 7, however, it is only possible to open said second check valve 11 if the pressure in the second passage 7 is higher compared to the first passage 6.
Furthermore, an air pocket 20 is visible within the housing 4.
Furthermore, there is a first check valve 7, which is connected to the fourth passage 9. The fourth passage 9 is connected to the first section 5a, i.e. the section with the larger diameter of the bore 5.
On the other hand, the third passage 8 is connected to the second section 5b, which is the section with the smaller diameter of the bore 5—more precisely with its left end.
In the first check valve 10, air can only flow towards the fourth passage 9 and hence the first section 5a of the bore 5, but not in the other direction. The first check valve 10 is furthermore connected with the fourth port 15 (not shown in this embodiment).
The differential piston 2 is hollow—forming a channel 3a, which comprises a highly throttled hollow pin 3b. Hence, if a short pulse of air is inserted through the third passage 8, the differential piston 2 will move to the right side (second end position)—as depicted in
In
In
Herein, the first port 12 is connected to a park and shunt valve, and the second port 13
is connected to an electric brake module EBS. The third port 14 is connected to a control port, and the fourth port 15 is connected to a reset button 22. The first check valve 10 allows air pulses from the reset button 22 to the differential piston 2, which would move it to the first end position, which is the driving position. The double-check valve 19 decides which port (third port 14 or first port 12) is connected to the second port 13, leading to the EBS. If the pressure in the third port 14 is higher compared to the first port 12, the third port 14 and the second port 13 are connected—if the pressure in the first port 12 is higher compared to the third port 14, the first port 12 and the second port 13 are connected. If the pressure at the first port 12 is decreasing, the pressure at the second port 13 follows, as the second check valve 11 opens. In this case, the parking brake (emergency brake) of a trailer of a utility vehicle can be actuated, but depending on a software logic, it could be overridden. Such override is possible in case of an existing electric connection. If the pressure at the first port 12 is smaller than the pressure at the third port 14, the double-check valve 19 separates the first port 12 and the second port 13. At the same time, the third port 14 is connected with the second port 13 therefore the EBS system is pressurized by system pressure from e.g. a reservoir of the trailer. In this case, a short pressurized air pulse is used for switching to the safe park position, a longer signal is used for switching to the drive position, and a permanent signal is used for emergency override
The present invention is not limited to the above mentioned embodiments. The differential piston 2 can have more sections, as well as the bore 5.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 22158477.4 | Feb 2022 | EP | regional |
| 22214446.1 | Dec 2022 | EP | regional |
