JPS624265B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic brake system for tractors and trailer-coupled vehicles, and more particularly to a trailer control relay valve used in such a hydraulic brake system.

Conventional fluid brake systems for tractors and trailer-coupled vehicles include a fluid brake system on the tractor side, including a fluid tank and a brake valve, connected to a fluid brake system on the trailer side via a service line and an emergency line. is known, and air is usually used as the working fluid.

An example of a hydraulic brake system for such a tractor and a trailer-coupled vehicle will be explained with reference to FIG. Dual brake valve 10 connected to air tank 6 and rear air tank 8
When the dual brake valve 10 is actuated, the air in the front air tank 6 is directly supplied to the front brake, and the air in the rear air tank 8 is sent to the rear and trailer relay valve 12 to actuate it and pass through this valve. air in the rear air tank 8 is supplied to the rear brake chamber 14.

On the other hand, the trailer-side fluid brake device 4 is connected to the rear and trailer relay valves 1 through the service line 16 and emergency line 18, respectively.
2 and the rear air tank 8, and the trailer air tank 22 is connected to the trailer air tank 22 through the relay emergency valve 20.
The air inside is supplied to the brake chamber 24 of the trailer.

That is, the relay emergency valve 20 normally supplies air to the trailer air tank 22 through the emergency line 18, and when the relay valve 12 is activated by the operation of the dual brake valve 10, air is sent through the service line 16. Activated by the signal pressure, Torura air tank 22
This air is supplied to the brake chamber 24 to operate as a relay valve.

However, if the connection between the tractor and trailer becomes separated due to an unexpected accident, emergency line 1
8 is damaged, in response to its communication with the atmosphere, air in the trailer air tank 22 is automatically supplied to the brake chamber 24 to automatically apply the brakes to the trailer.

Therefore, the above-mentioned conventional hydraulic brake system in a tractor-trailer coupled vehicle is designed to prevent the tractor and trailer from being disconnected due to an unexpected accident.
In the event that the emergency line 18 is damaged, the brakes are automatically applied to the trailer, so this is an extremely safe system. However, if the service line 16 is damaged, the relay emergency valve 20 will not operate at all, and the brake valve 1 will not operate on the tractor side.
There was a problem that even if the driver operated 0, the brakes would not be applied to the trailer at all, resulting in a dangerous situation.

In the conventional fluid brake system described above, the relay valve 12 is used for both the rear brake chamber and the trailer, but there are also systems in which separate relay valves are provided for each, and even in this case, as described above, Similarly, when the service line is damaged, no brakes are applied to the trailer.

Therefore, an object of the present invention is to provide a tractor and a trailer-coupled vehicle in which a fluid brake device on the tractor side including a fluid tank and a brake valve is connected to a fluid brake device on the trailer side via a service line and an emergency line. To provide a trailer control relay valve in a fluid brake system, which can act to automatically apply brakes to the trailer by operating the tractor's brakes even if the trailer's service line is damaged. .

In order to achieve the above object, the present invention provides a tractor and trailer connection in which a fluid brake device on the tractor side including a fluid tank and a brake valve is connected to a fluid brake device on the trailer side via a service line and an emergency line. A trailer control relay valve in a fluid brake system of a vehicle, the relay valve having a first inlet port connected to an outlet of the brake valve, a second inlet port connected to an outlet of the fluid tank, and the service line. a first outlet port connected to the brake valve, a second outlet port connected to the emergency line, an exhaust port communicating with the atmosphere, and a brake valve supplied from the brake valve through the first inlet port. a piston type actuator actuated in response to the pressure of a pressurized fluid; and a piston type actuator actuated in response to the pressure of a pressurized fluid; the first outlet port in communication with the exhaust port and the second inlet port in communication with the second inlet port;
a normal inoperative position communicating with the outlet port of the
a first actuated position that interrupts communication between the first outlet port and the exhaust port and causes the second inlet port to also communicate with the first outlet port; a valve assembly device movable between a second actuation position for blocking communication with a second outlet port and communicating the second outlet port with the exhaust port; has an outer piston that is reciprocably housed in a housing, and an inner piston that is coaxially housed in the outer piston so that it can reciprocate, and the working chambers of the outer piston and the inner piston are both arranged in the housing. the first inlet port and their back pressure chambers both communicate with said first inlet port.
The piston-type actuating device is configured to actuate the outer piston in response to the pressure of the pressurized fluid when there is no fluid leakage to the first outlet port via the service line. which engages the valve assembly to move the valve assembly from the non-actuated position to the first operative position and thereby fills the back pressure chamber and the first outlet port with the pressurized fluid. When a pressure of approximately the same magnitude as the pressure is generated and there is a fluid leak, both the outer piston and the inner piston actuate in response to the pressure of the pressurized fluid, and the inner piston engages the valve assembly device. the trailer, wherein the valve assembly is configured to move the valve assembly device from the inoperative position to the second operative position and thereby reduce the pressure at the second outlet port. Provides control relay valves.

Next, a preferred embodiment of the trailer control relay valve of the present invention will be described with reference to the drawings.

FIG. 2 shows an overall schematic diagram of a hydraulic brake system for a tractor and a trailer-coupled vehicle including the trailer control relay valve of the present invention, in which the same members as those shown in FIG. 1 are given the same reference numerals. The trailer control relay valve of the present invention is designated by the reference numeral 30. A trailer control relay valve 30 is connected to the brake valve 10 via a first inlet port 32 and a second inlet port 34.
to the rear air tank 8 via a first outlet port 36 , to the service line 16 via a first outlet port 36 , and to the emergency line 18 via a second outlet port 38 .

Details of the trailer control relay valve 30 are shown in FIG. 3 and FIG.
In addition to ports 6 and 38, an exhaust port 40 that communicates with the atmosphere
has. The relay valve 30 is broadly divided into a piston-type actuator 46 that operates in response to the pressure of pressurized fluid or air supplied from the brake valve 10 through the first inlet port 32; a first valve arrangement 42 and a second valve arrangement 44 which are operated to place the second inlet port 34, the first and second outlet ports 36, 38, and the exhaust port 40 in communication with each other in a predetermined manner; It consists of a valve assembly.

The piston-type actuator 46 includes dual pistons 78 and 80 that reciprocate within the housing 56 and actuation chambers 82 and 84 that communicate with the first inlet port 32.
Back pressure chambers 52, 8 communicating with first outlet port 36
8, and the double pistons 78, 80 are selectively driven by the differential pressure between the introduced air pressure and the pressure in the back pressure chambers 52, 88 in the working chambers 82, 84. ing. Details of this piston-type actuating device will be described later.

The first valve device 42 is connected to the second inlet port 3
4 and an intermediate chamber 48 communicating with the second outlet port 38.
a first seat valve 50 provided between the intermediate chamber 48 and the piston-type actuating device 46 for opening and closing them;
The second seat valve 54 is provided between the back pressure chamber 52 and the back pressure chamber 52 and opens and closes the second seat valve 54. The first seat valve 50 includes a first valve seat 58 provided on the inner wall of the housing 56 and a first valve body 62 provided on a valve stem 60 movably mounted on the housing 56.
Similarly, the second seat valve 54 consists of a second valve seat 64 provided on the inner wall of the housing 56 and a second valve body 66 provided on the valve stem 60. The two valve bodies 62 and 66 are integrally formed as shown, and the integral valve body is normally pressed to maintain the first seat valve 50 in the open position and the second seat valve 54 in the closed position. A spring 68 is provided to do this.

In the normal non-operating position shown in FIG. 3, the first valve device 42 has a first seated valve 50 in a closed position, a second seated valve 54 in a closed position,
Therefore, the second inlet port 34 is communicated with the second outlet port 38, both of which are disconnected from the back pressure chamber 52, and the outer piston 78 of the piston-type actuator 46 is actuated to open the valve as will be described later. When the stem 60 is moved slightly against the force of the spring 68, the second seated valve 54 is also in the open position and the first valve arrangement 42 is moved into the second inlet port 3.
When the inner piston 80 of the piston device 46 is driven and the valve stem 60 is further moved as described later, the first seat valve 50 closes.
The first valve device 42 assumes a second operative position that isolates communication between the second inlet port 34 and the second outlet port 38 and communicates the second outlet port 38 with the back pressure chamber 52 .

The valve stem 60 is a piston-type actuating device 4
The exhaust port 40 is formed as a through hole in the valve stem 60 and opens into the back pressure chamber 52 at the inner end 70 of the through hole valve stem.

A second valve device 44 is provided between the through hole 40 and the back pressure chamber 52 and opens and closes them.
is a seated valve, and the inner end 70 of the valve stem 60
a valve body 72 formed to surround the opening of the through hole 40 and an outer piston 78 of the piston device 46.
and a valve seat 76 provided at a position facing the valve body 72 on the back pressure chamber side.

In the normal non-operating position, the second valve device 44 is in an open position where the valve body 72 and valve seat 76 of the third seat valve are separated by a predetermined distance, as shown in FIG. 52 is communicated with the exhaust port 40, and only when the outer piston 78 of the piston-type actuating device 46 is driven as will be described later, the third seat valve closes to the closed position, and the back pressure chamber 52
Communication between the exhaust port 40 and the exhaust port 40 is cut off. Note that the other inner piston 8 of the piston type actuating device 46
0 is activated, the second valve device 44 is held in the open position, as will be described below, and this condition is shown in FIG.

The piston-type actuating device 46 has an outer piston 78 that is reciprocatably housed in a housing 56 and an inner piston 80 that is coaxially housed within the outer piston 78 so that it can reciprocate. The working chamber 82 communicates with the first inlet port 32 and is connected to the working chamber 84 of the inner piston 80.
communicates with the working chamber 82 of the outer piston 78 via a hole 86 formed in the outer piston 78. The back pressure chamber 52 of the outer piston 78 communicates with the first outlet port 36, and the back pressure chamber 88 of the inner piston 80 communicates with the hole formed in the outer piston 78.
It communicates with the back pressure chamber 52 of the outer piston 78 via 90. Further, the outer piston 78 and the inner piston 80 are each provided with a return spring 9.
2 and 94 are arranged to urge these pistons in a direction opposite to the driving direction by the pressure of the air introduced into the working chambers 82 and 84 through the first inlet port 32.

Inner piston 80 has an integral guide shaft 96 that extends coaxially beyond its working face and back surface and thus extends coaxially to the valve stem and is guided by outer piston 78 . A through hole 98 is formed. Tip portion 100 of the guide shaft 96 on the back side of the inner piston 80
is exposed to the back pressure chamber 52 of the outer piston 78, and the through hole 98 of the guide shaft 96 is always communicated with the through hole of the valve stem 60, that is, the exhaust port 40.

Further, the tip portion 100 of the guide shaft 96 is connected to the valve stem 60 when the inner piston 80 is driven.
The valve element 72 of the third seat valve 44 and the valve seat 76 are prevented from engaging with each other.

Further, the distal end portion 102 of the guide shaft 96 has a slit 1 so as to maintain communication between the through hole 40 of the valve stem 60 and the back pressure chamber 52 of the outer piston 78 when engaged with the inner end 70 of the valve stem 60.
02 is formed.

The relationship between the effective areas of the working surface 79 and the back surface 74 of the outer piston 78 is such that when the pressure inside the back pressure chamber 52 becomes greater than the pressure of the air introduced into the working chamber 82, the outer piston 78 moves in the direction of drive by the air pressure. It is now being pushed back in the opposite direction. Further, the relationship between the effective area of the inner piston's working surface 83 and the rear surface 85 is such that a predetermined pressure difference between the working chamber 82 and the back pressure chamber 52 that starts driving the outer piston 78 is relatively larger than the pressure difference between the working chamber 82 and the back pressure chamber 52. The inner piston 80 is driven only when the pressure is generated between the inner piston 80 and the back pressure chamber 88.

Therefore, when air is introduced through the first inlet port 32, the outer piston 78 is first driven, and then the back pressure chamber 52 of the outer piston 78 is driven.
The inner piston 80 is driven only when the pressure rise is insufficient and the pressure difference between the working chamber 84 and the back pressure chamber 88 of the inner piston becomes large enough to reach the predetermined pressure difference.

Furthermore, the movement stroke of the outer piston 78 is
The distance between the valve body 72 of the third seated valve 44 and the valve seat 76 in the normal open position shown in FIG. The upper and lower stoppers are set so that the distance is smaller than the sum of the intervals of 104 and 10
It is regulated by 6.

Furthermore, the movement stroke of the inner piston 80 is determined by the distance between the valve body 72 and the valve seat 76 of the third seat valve 44 in the normal open position shown in FIG. Valve seat 58
It is restricted only by the upper stopper 108 so that the distance is at least larger than the sum of the distances minus the travel stroke of the outer piston 78 described above.

Therefore, as is clear from the above description, the valve assembly 42 of the trailer control relay valve 30,
44 indicates that when air is not supplied to the first inlet port 32, i.e., in the non-actuated position, the first valve device 42 and the second valve device 44 are respectively in the non-actuated position described above and shown in FIG. and in the open position, thus communicating the second inlet port 34 with the second outlet port 38 and the first outlet port 36 with the exhaust port 40;
When air is introduced through the inlet port 32 of the
Due to the above-mentioned effective area relationship, the outer piston 78 is first driven, and due to the above-mentioned movement stroke relationship, the valve stem 60 is moved by the spring 68 while pressing the valve seat 76 of the third seat valve 44 against the valve 72. The valve 66 of the second seated valve 54 is moved away from its seat 64 by pushing against the force. The first valve arrangement 42 is thus moved to the previously described first operative position and the second valve arrangement 44 is moved to the closed position, thus closing these valve assemblies 42, 44.
assumes a first operative position that interrupts communication between first outlet port 36 and exhaust port 40 and also communicates second inlet port 34 with first outlet port 36 . At this time, if the pressure inside the back pressure chamber 52 rises and becomes larger than the pressure of the air introduced into the working chamber 82 of the outer piston 78, the effective area between the working surface and the back surface of the outer piston described above will increase. Due to this relationship, the outer piston is pushed back against the driving force of the air, and the third seat valve 44 is again in the open position, and the second seat valve 54 is in the closed position, and the pressure in the back pressure chamber 52 is reduced. Ru. Back pressure chamber 52
When the pressure of the air is reduced and becomes smaller than the pressure of the air introduced into the working chamber 82 of the outer piston 78, the outer piston 78 is driven again, the third seat valve 44 is closed, and the second seat valve 5 is closed.
4 is opened and the pressure in the back pressure chamber 52 increases again.
By repeating this, the pressure within the back pressure chamber 52, ie, the pressure at the first outlet port 36, is maintained at approximately the same pressure as the pressure of the air introduced into the working chamber 82 of the outer piston 78.

Further, in the above operation, the first outlet port 36
When there is air leakage through the service line and the pressure in the back pressure chamber 52 does not rise, the inner piston 80 is activated following the drive of the outer piston 78 due to the above-mentioned relationship between the working surface and the effective area of the back surface of the inner piston 80. is driven, and the inner end portion 100 of the inner piston 96 engages with the inner end 70 of the valve stem 60 to push down the valve stem 60 due to the relationship of the operating strokes of the outer piston 78 and the inner piston 80 described above. valve 4
While separating the fourth valve body 72 from the valve seat 76 and maintaining communication between the exhaust port 40 and the back pressure chamber 52 via the slit 102, the valve body 62 of the first seat valve 50 and the valve seat 58 are engaged. Match. This state is shown in FIG. That is, the second valve device 44 moves the first valve device 42 to the aforementioned first operating position while maintaining the open position. Thus, the valve assemblies 42, 44 assume a second operative position that isolates communication between the second inlet port 34 and the second outlet port 38 and communicates the second outlet port 38 with the exhaust port 40. The pressure in the emergence line connected to the second outlet port 38 is therefore reduced.

Note that the codes 110, 112, 114, 116, 1
18 is a seal.

To explain the operation of the fluid brake system of the tractor and trailer-coupled vehicle shown in FIG. Actuation of the brake valve 10 of the brake system 2 introduces air through the inlet port 32, and in response to the pressure of the air, the outer piston 78 of the piston-type actuator 46 is actuated to close the valve assembly 42 as described above. , 44 to the first operating position and the first
The communication between the outlet port 36 and the exhaust port 40 is cut off, and the second inlet port 34 is also communicated with the first outlet port 36. Therefore, air from the air tank 8 flows from the inlet port 34 to the first outlet port 36.
is sent to the service line 16 via. Further, at this time, as described above, the pressure is maintained at approximately the same pressure as the pressure of the air from the brake valve 10 introduced into the working chamber 82. Therefore, the relay emergency valve 20 supplies air at this pressure from the trailer air tank 22 to the brake chamber 24 to apply the brakes to the trailer, in the same way as when air is supplied through the relay valve 12.

On the other hand, when the service line 16 is damaged and there is an air leak, the pressure inside the back pressure chamber 52 does not increase even if the brake valve 10 is operated, and both the outer piston 78 and the inner piston 80 of the piston type actuating device 46 described above do not increase. Actuation of the valve assembly 42 , 44 establishes a second operative position in which the second inlet port 34 and the second outlet port 38 are disconnected from each other and the second outlet port 38 is in communication with the exhaust port 40 . Then, the emergent line 18 is communicated with the exhaust port 40. Therefore, the emergency line 18 is in communication with the atmosphere as if it were damaged, and the relay emergency valve 20
As in the case where the emergency line 18 is damaged, the air in the trailer air tank 22 is sent to the brake chamber 24 to apply the brakes to the trailer.

Note that in a normal state in which the trailer control relay valve 30 does not operate the brake valve 10 and the service line 16 is not damaged, the valve assemblies 42 and 44 connect the first outlet port 36 to the exhaust port, as described above. 40 and the second inlet port 34 to the second outlet port 38, the service line 16 is evacuated and the emergency line 18 is in communication with the air tank 8, and the service line 16 is in communication with the air tank 8. The original functions of the emergency line 16, the emergency line 18, and the relay emergency valve 20 are not affected in any way.

FIG. 5 shows another example of use in which the trailer control relay valve 30 of the present invention is incorporated into a hydraulic brake system for a tractor and trailer-coupled vehicle. As mentioned above, the trailer control relay valve 30 is
During normal operation without any damage to the service line 16, the back pressure chamber 52 and the first outlet port 3
It functions as a relay valve by maintaining the pressure in the brake valve 6 at approximately the same pressure as the pressure of the air from the brake valve 10 introduced into the working chamber 82. The usage example shown in FIG. 5 focuses on making effective use of the function of the trailer control relay valve 10, and uses the rear relay valve 1 shown in FIG. 2 in the hydraulic brake device 2 on the tractor side.
2 is omitted, and instead, the rear brake chamber 14 is connected to the first outlet port 36 of the trailer control relay valve 10, so that the relay valve 10 also functions as a relay valve for the trailer and for the rear of the tractor. It is something. By doing so, the configuration of the hydraulic brake device 2 on the tractor side becomes simple, and the price of the hydraulic brake system for a tractor and trailer-coupled vehicle can be made not so different from that of conventional systems.

Therefore, according to the relay valve for trailer control of the present invention, since it is equipped with the above-mentioned piston type actuating device and valve assembly, the fluid brake device on the tractor side including the fluid tank and the brake valve can be connected to the service line and emergency In hydraulic brake systems for tractors and trailer-coupled vehicles that are connected to a hydraulic brake system on the trailer side via a line, the brakes on the trailer are usually applied quickly in response to the operation of the brake system brake valve on the tractor side. It acts as a relay valve that can act as a relay valve, and does not affect the original function of the emergency line in any way.In the event that the service line is damaged and air leaks, the brake valve of the brake system on the tractor side will operate to stop the trailer. Therefore, it is possible to provide an extremely safe brake device that can act to apply a brake even when the vehicle is in use.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a conventional hydraulic brake system for a tractor and trailer-coupled vehicle, and FIG. 2 is a schematic diagram of a similar tractor and trailer-coupled vehicle incorporating a preferred embodiment of the trailer control relay valve of the present invention. 1 is a schematic diagram of a fluid brake system,
FIG. 3 is a detailed sectional view of the trailer control relay valve shown in FIG. 2, and FIG. 4 is a sectional view similar to FIG. 3 showing the operating positions of each member when the service line is damaged. It is. FIG. 5 is a schematic view showing another usage example in which the trailer control relay valve of the present invention is incorporated into a hydraulic brake system of a tractor and trailer-coupled vehicle. In the figure, 2...Fluid brake device on the tractor side.
4...Fluid brake device on the trailer side. 6,8...
...air tank. 10...Brake valve. 16...
...service line. 18...Emazien line.
30...Relay valve for trailer control. 32...
First inlet port. 34...Second inlet port.
36...First exit port. 38...Second exit port. 40...Exhaust port. 42...first valve device. 44...Second valve device. 46...
Piston type actuator. 50...first seat valve.
52... Back pressure chamber. 54...Second seat valve. 60
...Valve stem. 78...Outer piston. 8
0...Inner piston. 96...Guide shaft. 10
2...Slit.

Claims (1)

[Claims] 1. A fluid brake for a tractor and a trailer-coupled vehicle, in which a fluid brake device on the tractor side, including a fluid tank and a brake valve, is connected to a fluid brake device on the trailer side via a service line and an emergency line. A trailer control relay valve in the system, the first inlet port being connected to the outlet of the brake valve, the second inlet port being connected to the outlet of the fluid tank, and the second inlet port being connected to the service line. a first outlet port; a second outlet port connected to the emergency line; an exhaust port communicating with the atmosphere; and pressurized fluid supplied from the brake valve through the first inlet port. a piston-type actuator actuated in response to the pressure of the piston-type actuator; provided with respect to the second inlet port, the first and second outlet ports, and the exhaust port; a normal inoperative position communicating the first outlet port with the exhaust port and communicating the second inlet port with the second outlet port; a first actuation position that interrupts communication between the port and the exhaust port and also communicates the second inlet port with the first outlet port; and the second inlet port and the second outlet port. and a valve assembly movable between a second actuated position that isolates the second outlet port from communication with the exhaust port and communicates the second outlet port with the exhaust port, the piston-type actuator being disposed within the housing. An outer piston housed in a reciprocating manner,
and an inner piston housed in the outer piston so as to be able to reciprocate coaxially therein, the working chambers of the outer piston and the inner piston both communicating with the first inlet port, and the back pressure chambers thereof both communicating with the first inlet port. The piston-type actuator is in communication with the first outlet port, and the piston-type actuator is responsive to the pressure of the pressurized fluid when the first outlet port is free of fluid leakage through the service line. Actuation of a piston causes it to engage the valve assembly, thereby moving the valve assembly from the inactive position to the first operative position and thereby applying the pressure to the back pressure chamber and the first outlet port. A pressure of approximately the same magnitude as the pressure of the pressurized fluid is generated, and when there is a fluid leak, both the outer piston and the inner piston actuate in response to the pressure of the pressurized fluid, and the inner piston moves toward the valve assembly. engaging the device moves the valve assembly device from the inactive position to the second operative position and is configured to reduce the pressure at the second outlet port. Relay valve for trailer control. 2. The valve assembly device has an inoperative position in which the second inlet port communicates only with the second outlet port, and a first position in which the second inlet port also communicates with the first outlet port. movement between an actuated position and a second actuated position that interrupts communication between the second inlet port and the second outlet port and communicates the second outlet port with the first outlet port; a first valve device that obtains a first valve device;
a second valve device movable between a normally open position that communicates the outlet port of the valve with the exhaust port and a closed position that blocks communication between the first outlet port and the exhaust port; The piston-type actuating device moves the second valve device to the closed position when the first valve device is moved to the first actuating position; The relay valve for trailer control according to claim 1, wherein both valve devices are controlled in conjunction so that the second valve device is held in the normal open position when moving to the operating position. . 3. The trailer control relay valve according to claim 1 or 2, wherein the first and second valve devices are seat valves movable coaxially with the piston type actuating device. 4. Movement of the first valve device to the first operating position is effected by the outer piston;
The effective area of the working surface and back surface of the outer piston is such that when the pressure in the back pressure chamber becomes greater than the pressure of the pressurized fluid introduced into the working chamber, the outer piston moves in the opposite direction to the driving direction of the pressurized fluid. Claim 3 in a relationship where it is pushed back
Relay valve for trailer control as described in section. 5. Movement of the first valve device to the second operating position is effected by the inner piston;
The effective area of the working surface and back surface of the inner piston is such that a predetermined pressure difference between the working chamber of the inner piston and the back pressure chamber is relatively larger than the pressure difference between the working chamber and the back pressure chamber that starts driving the outer piston. 5. The trailer control relay valve according to claim 4, wherein the inner piston is driven only when the inner piston is moved between the inner piston and the inner piston. 6. The first valve device includes a first seat valve provided between the second inlet port and an intermediate chamber communicating with the second outlet port to open and close them; a second seat valve provided between the piston and the back pressure chamber to open and close them; and a spring that normally holds the first seat valve in the open position and the second seat valve in the closed position. A trailer control relay valve according to claim 3, 4, or 5. 7 The first and second seat valves each have a
comprising first and second valve seats provided on an inner wall of the housing, and first and second valve bodies on a valve stem movably mounted on the housing,
The valve stem is coaxial with the outer piston and the inner piston so that when the outer piston and the inner piston are driven, they are pushed and moved to move the valve body against the force of the spring. 7. The trailer control relay valve according to claim 6, wherein the trailer control relay valve is arranged as follows. 8. The valve stem is formed with a through hole that provides the exhaust port, the through hole opens into the back pressure chamber of the outer piston at the inner end of the valve stem, and the second valve device The trailer control relay valve according to claim 7, which is a third seat valve that opens and closes the through hole and the back pressure chamber of the outer piston. 9 The third seat valve includes a valve body formed at the inner end of the valve stem so as to surround the opening of the through hole, and a valve provided at a position opposite to the valve body on the back surface of the outer piston. 9. The trailer control relay valve according to claim 8, wherein the relay valve has a seat, and the valve body is normally spaced apart from the valve seat. 10 The inner piston has an integral guide shaft that coaxially extends beyond the front and rear surfaces thereof and is guided by the outer piston, and the guide shaft is formed with a through hole, and the guide shaft The rear end portion of the valve stem is exposed to the back pressure chamber of the outer piston so that the through hole communicates with the through hole of the valve stem, and the guide shaft is connected to the inner piston when the inner piston is driven. Claim 9, wherein the tip has a size sufficient to engage the inner end of the valve stem and prevent engagement between the valve body and the valve seat of the third seat valve. Relay valve for trailer control. 11. A slit is formed at the tip of the guide shaft so that communication between the through hole of the valve stem and the back pressure chamber of the outer piston can be maintained when the guide shaft engages with the inner end of the valve stem. A trailer control relay valve according to item 10. 12 The movement stroke of the outer piston is:
It is larger than the distance between the valve body and the valve seat of the third seated valve in the normal open position, and is larger than the sum of this distance and the distance between the valve body and the valve seat of the first seated valve in the normal open position. Small claim 9,
The trailer control relay valve according to item 10 or 11. 13 The movement stroke of the inner piston is:
The movement stroke of the outer piston is determined from the sum of the distance between the valve body and the valve seat of the third seat valve in the normal open position and the distance between the valve body and the valve seat of the first seat valve in the normal open position. 13. The trailer control relay valve of claim 12, wherein the relay valve is at least greater than the subtracted value.