DE3308082A1 - Trailer control valve - Google Patents

Abstract

A trailer control valve is proposed, which is provided with a double seat valve for introducing a brake pressure into a trailer brake line (17). The double seat valve (10) lies in a pressure reversal chamber (13), in which the particular pressure introduced into the trailer brake line (17) prevails. The pressure reversal chamber (13) is defined by a reaction piston (11), which ensures the ability for graduated braking. <??>On the rear side of the reaction piston (11) a counter-pressure chamber (14) is arranged, which is connected to the pressure reversal chamber (13) by way of a duct connection (32, 33). In this duct connection (32, 33) is a pressure limiting valve (34). The pressure limiting valve (34) facilitates soft, sensitive, and highly responsive release of the trailer brakes. <IMAGE>

Description

R. 18390

17 · 1 - 1983 He / Wl

ROBERT BOSCH GMBH, 7OOO Stuttgart 1

Trailer control valve
State of the art

The invention is based on a trailer control valve according to the preamble of the main claim. Such a trailer control valve is known (U.S. Patent 3,275,381).

In this known trailer control valve, the reaction piston delimits a chamber with its rear side, which is connected to Outside air is connected. It is therefore not possible to influence the feedback piston from behind.

Advantages of the invention

The trailer control valve with the characterizing features of the main claim has the advantage that the reaction piston can be biased from its rear side in such a way that the braking pressure for the trailer is changed without affecting the controllability of the brake pressure in the case of brake pressure corrections, such as when there is a change of the applied pressure occur, is affected.

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drawing

An exemplary embodiment of the invention is shown in the drawing shown, namely, Figure 1 shows a section through the trailer control valve and Figure 2 shows a diagram of the Pressure curve.

Description of the embodiment

A two-circuit trailer control valve has a housing 1 in which two relay pistons 2 and 3 are arranged one behind the other. Above each piston 2 or 3 there is a working chamber h or 5j which is connected to a service brake circuit I or II via a lateral connection 6 or 7.

In this way, the two relay pistons 2 and 3 are effective connected in series. The front (3) has an outlet valve seat 9 on an axial shoulder 8 of a double seat valve 10. The axial extension 8 extends through a partition 15 fixed to the housing and a reaction piston 11 j the coaxial to the two relay pistons 2 and 3 are arranged. The feedback piston 11 has a shoulder 12 with which it is attached to a shoulder 13 of the relay piston 3 can create. Between the partition 15 and the reaction piston 11 is a counter-pressure chamber 1U, the meaning of which will be explained later.

The other side of the reaction piston 11 delimits a pressure change chamber 10 'in which the double seat valve 10 is arranged is. This pressure change chamber 10 'has a lateral Terminal 16 to which a trailer brake line 17 is connected. On their, the feedback piston 11

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On the opposite side, the partition 15 delimits an outside air chamber 18, which via a radial channel 19 in the piston axial shoulder 8 and an adjoining, the exhaust valve seat 9 penetrating axial channel 20 has connection to the outside air.

A storage chamber 21, which has a connection 23 connected to a storage line 22, is located under the pressure change chamber 10 ′. Towards the pressure change chamber 10 'it is limited by a piston 2k which carries an inlet valve seat 25 of the double seat valve 10. A sleeve 26 is attached to the piston 2k , which on the one hand forms a guide for a closing body 27 of the double seat valve 10, but on the other hand extends through a housing wall 28 and carries a further relay piston 29 of the trailer control valve at its end. The sleeve 26 and the closing body 27 are axially pierced for the passage of outside air.

The relay piston 29 separates a working chamber 30 from an outside air chamber 31, which is connected via a check valve 31 ' has to the outside. The working chamber 30 is connected to a parking brake device and protrudes a port 30 'usually under supply pressure. To switch the double seat valve 10 in the braking direction is the The supply pressure is released from the working chamber 30.

Both the pressure change chamber 10 'and the counter-pressure chamber Ik are connected to one another via a channel connection 32 and 33. This channel connection 32 and 33 is made through lateral wall openings in the trailer control valve. In the channel connection 32, 33 a pressure relief valve 3k is used, which has a double seat

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■ valve 35 and a piston 36 connected to the inner seat of the double seat valve 35. Behind the piston 36 is an outer air chamber 37> which is connected to the external air chamber 18 via a channel 38th In the chamber 37 a spring 39 acting on the piston 35 is arranged, which tends to hold the piston with its valve seat in a position in which the valve seat holds a closing body Uo of the double seat valve 35 away from its other valve seat. The preload of the spring 39 and thus the pressure at which the pressure limiting valve 3 switches over can be changed by means of an adjusting screw hl.

Mode of action
Driving position

In the driving position, the chamber 21 is under pressure via the supply connection 23 and the chamber 30 via the connection 30 '(control line for the parking brake valve), which pressure is the same in both chambers. The two relay pistons 2 and 3 are in their upper position. The supply air keeps the closing body 27 on the inlet valve seat 25 · The chambers 18, 13, 1 hour and 37 are vented via the chamber 31st

Braking with the service brake

When braking via the service brake circuits, the respective controlled pressure prevails in the working chambers k and 5. The relay pistons 2 and 3 have the same effective area and are therefore equal. If the system is intact and the control pressures are the same, relay piston 3 moves downwards

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(the relay piston 2 is pressurized on both Piston sides switched off), first closes the vent with the outlet seat 9 and then pushes the Valve closing body 27 away from its inlet seat 25.

Supply air now flows out of the chamber 21 into the pressure change chamber 10 'and from there into the trailer brake line 17 · The trailer is braked.

When the compressed air flows into the pressure change chamber 10 ', compressed air simultaneously flows through the channel 33, the still open pressure limiting valve 3 ^ · and the channel 32 into the counter-pressure chamber 1h. The pressure introduced into the trailer brake line 17 thus acts both on the underside of the piston and on the upper side of the piston of the feedback piston 11 and initially holds it in the position shown. The pressure increase in the back pressure chamber 1 -U- is determined by the pressure relief valve 3 ^. The height of the pressure increase can be varied via the adjustable spring force of the spring 39 by means of the screw kl. The pressure limiting valve 3 ^ closes its inlet seat with the closing body kO when the forces between the spring force of the spring 39 and the air force on the piston 36 are in equilibrium.

If the pressure in the pressure change chamber 10 'continues to rise then outweighs the air force on the piston underside of the reaction piston 11 and moves it upwards until it is on Relay piston 3 comes to a stop with its shoulder 12.

In the diagram according to FIG. 2, an inflection point A is shown, which is reached when the pressure relief valve 3k is switched over. The location of the kink point of the characteristic

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shows the set lead. The reaction force of the controlled in the pressure change chamber 10 ' Pressure now counteracts the control pressure on relay pistons 2 and 3 via feedback piston 1 1. Feedback piston 11 and relay pistons 2 and 3 move above the knee point 1 as a "package" when the pressure changes or at. Such switchover points with short-term downshift are labeled B and C in the diagram the resulting, only very slight response delay is due to the smallness of the pressure deviations from the straight line recognize. Has. an equilibrium of forces is established, the inlet seat 13 is closed again in the partial braking position. In this middle position there are supply and trailer brake valves til and venting blocked from one another. In full braking position, the relay piston 2 or 3 holds the valve closing body 27 of the double seat valve 10 is open.

If the control pressure drops, there is an equilibrium of forces disturbed, and feedback piston 11 and relay piston 2 and are raised. Via the open exhaust valve seat 9, the pressure in the pressure change chamber 10 'is then reduced to the level of the control pressure that is now present.

Braking with the parking brake valve

When braking via the parking brake valve, the pressure is completely or partially lowered in the chamber 30 and the double seat valve 10 is then also switched in the braking direction.

The advantages of the trailer control valve described are the possibility of external

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change of the preload of the spring 39 by means of the adjusting screw Ii 1 adjustable lead or recovery of the trailer brake pressure, without the controllability of the brake pressure during brake corrections (change of the controlled Pressure) is adversely affected.

Or in other words: in the event of a pressure reduction in the course of the course During the increase in brake pressure, the double relay piston 2, 3 follows immediately because the reaction force above the feedback piston 11 immediately to double Relay piston 2, 3 works. The double seat valve 10 is therefore brought to its new setting without any delay.

It is of course also possible to use the pressure for the counterpressure, which is preferably monitored by a pressure limiting valve chamber Ά not from the pressure change chamber 10 'but from from another chamber of the trailer control valve or even from another pressure source.

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Claims (10)

R. 18390 17-1 - 1983 He / Wl ROBERT BOSCH GMBH, TOOO Stuttgart 1 Expectations \ 1.j Trailer control valve for pressure medium brake systems, in particular dual-circuit pressure medium brake systems on wagon trains, the trailer brake line of which can be vented and deflated in stages depending on the brake pressure in at least one brake circuit of the towing vehicle service brake, the control valve having at least one axially displaceable relay piston, which on the one hand can be acted upon by the brake pressure of the service brake circuit and, on the other hand, by the pressure prevailing in a pressure change chamber, fed into the trailer brake line and which carries a valve seat that works together with a double valve body, as well as a feedback piston which is subject to the pressure in the pressure change chamber and which, depending on the level of the pressure in the pressure change chamber counteracts the pressure in the service brake circuit, characterized in that a counter-pressure chamber {lh) is formed on the back of the reaction piston (11) and that the pressure in this counter-pressure chamber (1U) depends on a Vo return pressure is. 2. Trailer control valve according to claim 1, characterized characterized in that the pressure in the back pressure chamber (1U) can be monitored by a pressure limiting valve (3 * 0 is . - 2 - R. 18390 3. Trailer control valve according to claim 2, characterized in that the default pressure is the pressure in the pressure change chamber and that between the pressure change chamber (10 ') and the back pressure chamber (1 h ) there is a channel connection (32, 33) into which the pressure relief valve (3h) is inserted. k. Trailer control valve according to one of Claims 1 to 3, characterized in that the counter-pressure chamber (^ k)
on the side opposite the reaction piston (11)
is limited by a fixed housing wall (15). 5. Trailer control valve according to one of Claims 1 to U, characterized in that the pressure at which the pressure limiting valve (3 * 0 interrupts the connection to the counterpressure chamber (1 k )), preferably via an adjusting screw
(kO) is adjustable. 6. Trailer control valve according to one of claims 1 to 5, characterized in that the in the back pressure chamber (1 k ) only pressure acting on the reaction piston (11)
is of pneumatic origin. 7. Trailer control valve according to one of claims 3 to 6, characterized in that the pressure relief valve
(3M is integrated into a housing (1) of the trailer control valve and that the channel connection (32, 33) between
the pressure change chamber (10 ') and the counter pressure chamber (lh) is made by lateral storage openings in the trailer control valve. 330808; - 3 - R. 18390 8. Trailer control valve according to one of claims 2 to 7, characterized in that the pressure relief valve (3 * 0 is designed as a double-seat valve (35) -'. 9. Trailer control valve according to one of claims 2 to 8, characterized in that an outside air chamber (37) in the pressure relief valve (3 ^ +) via a channel connection (Channel 38) to a control valve-outside air chamber (13) which is constantly connected to outside air. 10. Trailer control valve with a coaxial outside air connection monitored by a check valve according to claim 9s, characterized in that the pressure-limiting valve external air chamber (37) to an outside air connection monitored by the check valve (31) connected.