Fluid-pressure and analogous brake systems – Multiple fluid-receiving devices – Multiple motors
Reexamination Certificate
1998-09-09
2001-03-27
Graham, Matthew C. (Department: 3613)
Fluid-pressure and analogous brake systems
Multiple fluid-receiving devices
Multiple motors
C303S003000, C303S118100
Reexamination Certificate
active
06206481
ABSTRACT:
PRIOR ART
EP 0 110 119 A1, FIG. 4 and EP 0 547 407 A1 have disclosed a relay valve whose control chamber can be controlled with control pressures conveyed from two control circuits of an electronically controlled compressed air brake system for motor vehicles. The relay valve is connected to at least one brake cylinder of the vehicle. The two control pressures can be generated with an actuation of the braking power transmitter, a control pressure in an electrical part of the braking power transmitter and a control pressure in a pneumatic part. Each control pressure can take the place of the other. However, since the control pressure generated in the electrical part of the braking power transmitter should be the leading one, in the presence of this control pressure, the other control pressure generated in the pneumatic part of the braking power transmitter is held back by means of a reversing valve disposed upstream of the control chamber of the relay valve. However, if the control pressure generated in the electrical part of the braking power transmitter fails, then the other control pressure comes into play in the control chamber of the relay valve by means of reversing the valve. The compressed air brake system therefore maintains its functioning capacity when there is a failure of this kind.
Conventional compressed air brake systems of motor vehicles have two control circuits of a service brake system that are separate from each other, of which one control circuit is associated with the front axle of the vehicle and one control circuit is associated with the rear axle. Pulling vehicles of vehicle combinations are furthermore equipped with a trailer control valve for actuating a trailer brake system. The trailer control valve that constitutes a relay valve has two control chambers each of which is respectively connected to a control circuit of the service brake system for the purpose of a parallel redundancy. Another control chamber of the trailer control valve is connected to an auxiliary brake system of the pulling vehicle. The trailer brake system can be actuated by means of introducing pressure into the control chambers of the trailer control valve, which are connected to the control circuits of the service brake system. The control circuit associated with the rear axle of the pulling vehicle is the leading one. In addition, the trailer control valve can be switched over for braking purposes by means of a pressure decrease in the control chamber associated with the auxiliary brake system.
Electronically controlled compressed air brake systems of pulling vehicles are equipped with a trailer control module, according to DE 42 26 697 C1, which has a trailer control valve with two control chambers associated with the control circuits of the service brake system. Since the leading control circuit is an electrically operating one, solenoid valves are provided in the upper part of the valve housing, with which control air withdrawn from a compressed air reservoir can be introduced into the associated control chamber for an actuation of a trailer brake system. In the event of a failure of the electrical control circuit, the second, pneumatic control circuit comes into play for the introduction of control air into the second control chamber of the trailer control valve. Whereas the electrical control circuit thus functions alone and with a high degree of functional reliability in the control of the trailer brake system, a second control chamber is kept in reserve in the trailer control valve and only needs to be used in the unlikely event of a failure. Furthermore, in the known trailer control valve, measures are taken to keep a control piston disposed in the second control chamber mobile so that it is functional in the event of a failure of the electrical control circuit. Viewed on the whole, measures that are relatively costly in terms of construction are taken in order to maintain the function of the trailer control valve, for an unlikely defect of the electrical control circuit.
ADVANTAGES OF THE INVENTION
The trailer control module according to the invention has an advantage over the prior art that the structural costs are reduced considerably by means of eliminating the second control chamber with its control piston. Nevertheless, it is assured, however, that in any case, a control piston is available, independent of which control circuit a control pressure is used from. In addition, the directional control valves of an extremely simple design that are inserted into a corresponding circuit arrangement are sufficient in order to generate a control pressure in the electrical control circuit using the compressed air reservoir associated with the auxiliary brake system and to modulate this control pressure, for example as a function of load or brake slip.
Advantageous improvements and updates of the trailer control module are possible by means of the measures taken hereinafter.
In the improvement of the invention disclosed herein, simple means are used to achieve the fact that in the event of a failure of the electrical control circuit, the control pressure of the pneumatic control circuit can come into play on the one control piston.
Finally, the measure disclosed herein produces a component in which the electrical and mechanical means are united that are required for directly controlling the one control piston.
REFERENCES:
patent: 4616881 (1986-10-01), Muller et al.
patent: 4919492 (1990-04-01), Samuelson et al.
patent: 5443306 (1995-08-01), Broome
patent: 3921 078 A1 (1991-01-01), None
patent: 4226697 C1 (1993-09-01), None
patent: 0110119 A1 (1984-06-01), None
patent: 0547407 A1 (1993-06-01), None
patent: WO 91/08934 (1991-06-01), None
patent: 40 5330415 (1993-12-01), None
Kaisers Olaf
Schaffert Eberhard
Graham Matthew C.
Greigg Edwin E.
Greigg Ronald E.
Knorr-Bremse
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