DE2419244C2 - Anti-lock device for braking systems of vehicles - Google Patents

Description

direction and thus in particular the relay valve only may have extremely short switching times.

In order to achieve these extremely short switching times, several constructive solutions are already available suggested. In particular, attempts have been made to determine the stroke paths that the pistons in the relay valves have to cover, to be shortened and is corresponding to the generic term of claim 1 Facility come. However, this anti-lock device tends to understeer therefore a high air consumption and can an undesirably rapid re-acceleration of the monitored Effect vehicle wheel.

The present invention has therefore set itself the task in an anti-lock device of the initially described type, in which the Umsehaltzeiten are already kept extremely small, a Function to avoid understeering with monitored pressure decrease and increase speeds to ensure.

This object is achieved according to the invention by what is specified in the characterizing part of claim 1 Features solved

From DE-AS 16 55 432 a control circuit for an anti-lock device with a first contact that closes at a certain wheel deceleration a second contact closing at a higher wheel deceleration and a third contact at one specific wheel acceleration, the closing contact is known. The first and third contact are immediate, the second contact is via one of the third Contact resettable flip-flop with one each Input of an OR gate connected. A fourth input of the OD'iR element is a timer Serving monoflip as well as an AND element controllable by the second and third contact is connected upstream of the The output of the OR gate controls an inlet solenoid valve and the output of the flip-flop controls an outlet solenoid valve a brake pressure.

The ZeitgKsd is used here to suppress the Effects of short opening times of the third contact, which are immediately due to the vibration its closing can follow. The known control circuit has no means for compensation undesirable understeering.

Further single rows and embodiments of the inventive concept are attached to the subclaims remove.

An exemplary embodiment of the subject matter of the invention is described below with reference to the drawing. It shows

F i g. 1 a-J schematic representation of a relay valve according to the invention with the anti-lock device,

Fig.2 an embodiment of the electronic Control for the solenoid valves,

3 shows a time diagram to explain the mode of operation of the electronic control according to FIG F i g. 2 and

4 shows a logical table to explain the mode of operation of the OR circuit in connection with the delay element.

According to FIG. 1, the relay valve 1 has a compressed air connection 2. to which a motor vehicle brake valve 3 is connected. this in turn from a compressed air tank 4 is supplied with compressed air via a line 5 and in dependent wedge «in the Pcdalweg compressed air in a connection 2 of the relay valve flow in liil.il.

The connection 2 leads via an inlet valve 6 with its valve seat 7 into a valve chamber 8 which has an opening 9 is connected to a wheel brake cylinder 10. The wheel brake cylinder 10 does not act on the brake of one shown vehicle wheel. A valve plate of the inlet valve 6 in the valve chamber 8 is provided with an im Relay valve 1 firmly clamped diaphragm piston 11 connected. An outlet 12 to the atmosphere is through a Outlet pipe 13 is formed which is fixed to a diaphragm piston 14 clamped in ίο relay valve 1 is connected and carries a valve seat 15 for a fixed valve plate 16. The outlet pipe 13 is guided through the wall of the relay valve 1 so that it can move airtight at 17

The membrane pistons 11 and 14 separate the valve chamber 8 within the relay valve 1 from the control chamber 18 which extends over it on both sides. This is connected to the connection 2 zr-n motor vehicle brake valve 3 via a nozzle 20 and the solenoid valve Fi, which is open in the unexcited state, with valve plate 21 and valve seat 22 and a pipe 19. The steering chamber 18 can also be connected to a subchamber 25 via the outlet solenoid valve E ₂ , which is closed in the de-energized state, with the associated valve plate 23 and valve seat 24. The subspace 25 is connected to the atmosphere via a nozzle 26. The valve plates 21 and 23 are held in their normal position by springs 27 and 28 when the solenoid valves E ₁ and E ₂ are not excited. The effect of the device is as follows: Ip the normal position, ie when driving, so when there is no braking, all parts take the in the F i g. I drawn standing. This means that the motor vehicle brake valve 3 does not conduct any compressed air via the connection 2 into the valve chamber 8 of the relay valve 1. The wheel brake cylinder 10 is vented via the outlet valve 15, 16 and the pipe 13 and the brake is released. When the motor vehicle brake valve 3 is actuated, a pressure level corresponding to the set brake level is passed into the valve chamber 8 and thus also into the wheel brake cylinder 10 via the inlet valve 6, 7. At the same time, compressed air enters the control chamber 18 via the pipe 19, the nozzle 20 and the open inlet valve 21, 22 of the solenoid valve E \ , whereby the inlet valve 6, 7 is opened even further by means of the diaphragm piston 11, while the outlet valve 15, 16 is closed because the pressure of the control chamber 18 on the diaphragm piston 14 in the closing direction of the outlet valve 15, 16 acts. The wheel brake cylinder 10 receives compressed air via the opening 9 and the brake is applied. so occurs a risk of locking, so the solenoid valves E, and E ₂ excited in more detail later manner explained. When the two solenoid valves E 1 and E 2 are excited, the inlet valve 21, 22 is closed and the outlet valve 23, 24 of the outlet solenoid valve E _{2 is} opened. No compressed air can then flow into the control chamber 18 from the motor vehicle brake valve 3 via the pipe 19. Instead, the control chamber 18 is vented via the now open valve 23,24 in the sub-chamber 25 and the nozzle nx üb 26> M with controlled speed in the atmosphere. As a result of the reduced pressure in the control chamber 18, the diaphragm pistons 11 and 14 move in the direction of the adjoining control chamber 18. In the process, the inlet valve 6, 7 is firmly closed and the outlet valve 15, 16 i "is opened. L) .; Pressure \ r. \ Vcntilnium 8 and thus; m wheel brake cylinder 10 is quickly lowered and the lock for the vehicle wheel in question is released.

In the transition from the pressure drop in the control room 18 to a HaIu phase mil accordingly Reduced pressure in the wheel brake cylinder 10 often causes an impairment which is caused by the reduction of the control pressure in the closed control chamber 18 with the outlet valve 15 still open, 16. Since the control room 18 has to be kept very small. with a small solenoid valve cross-section Switching / rushing is achieved by the closing stroke of the diaphragm piston 14 for the outlet valve 15, 16 < additional volume proportion relatively large, it occurs a corresponding pressure reduction in the control chamber 18 and the understeering affects the pressure in the Wheel brake cylinder strongly off. It can accept amounts between I and 2.4 cash. This not only requires a ■■ increased air consumption, but can also lead to an undesirable rapid during the normal control cycle Accelerate the vehicle wheel again.

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a logic circuit implemented in Fig 2 - is shown schematically. ^1. An electrical control circuit 31 - its structure is known in principle and is therefore not described here - is provided with two output connections ei and e>. If there is a risk of blocking, for example, stimulated by a speed sensor (not shown) connected to the endangered vehicle, it applies voltage to its output, while the output remains de-energized - The control circuit 31 changes the voltage supply at the outputs c \ and e_> to the value. After a certain stopping phase, during which the vehicle can reach a road section with better tire grip, the control circuit 31 switches both outputs ei and e > to end the anti-lock cycle.

According to FIG. 2 leads from output e, a line via a conventional delay element 29 (not shown in the internal structure) (with a delay time -> »fi - I ₂ according to FIG. 3) to an input of an OR element 30. The other input of the OR element Member 30 is connected to the output c _: parallel to the coil of the outlet solenoid valve E _2. The coil of the inlet solenoid valve E is connected to the output of the OR gate 30 ■ «>.

The effect of this arrangement can be seen from the diagram in FIG. 3 explained in more detail. On the abscissa the time is ι and the ordinate is the pressure p "18 in the control room and dashed the pressure p, in"applied><> valve chamber 8 and in the wheel 10th addition to the solenoid valves E, and E _2. During the normal braking process, the pressure increase takes place both in the control chamber and in the wheel brake cylinder 10 up to the point in time t \ ">" . If there is a risk of blocking, output e? the control circuit 31 at the time /, energized and the outlet solenoid valve E ₂ ",: rd directly, the inlet valve E, energized via the OR gate. The pressure drop in the control chamber 18 from the value P \ to the value I ' now takes place, at which point in time I ₂ the output e_> is switched off. Both solenoid valves Ei and E ₂ drop out. ie the inlet solenoid valve Ei opens and the outlet solenoid valve E ₂ closes. Compressed air therefore flows from port 2 into control chamber 18 and causes a pressure increase in it beginning at I _2. At the point in time f>, the output ei becomes live. The inlet solenoid valve Ei is only excited and closes _{at the time i t} after the time delay established by the delay element 29 between the times /> and ti. So the outlet valve 23, 2- \ in the solenoid valve E _{2 is} closed immediately at time t ₂ , while the inlet valve 21, 22 of the solenoid valve Ei opens briefly and the pressure in the control chamber increases to the value at a certain speed via the nozzle 20 pi increases. From now on, the time I ₁ , the pressure p "in the control chamber 18 remains almost constant, as can be seen from the solid curve ir. F i". 3! The pressure "in the wheel brake cylinder 10 decreases approximately between the times t \" and f) to this constant value pi: between times t ₂ and t \ , the outlet valve 15, 16 is closed and the diaphragm piston cannot subsequently cause any undesired pressure changes in the control chamber 18 at time fi.

In Fig. 4 is a logic table indicates which g for the electronic control circuit according F "i. 2 applies. It is c.-c voltage command at the outputs ei and C ₂ as well as the excitation of the solenoid valves Ei and E ₂ by the dual values 0 and L If the two outputs ei and e _{2 are} voltage bs, the solenoid valves Ei and E ₂ are also not energized. All values show 0, as can be seen in line 1 of the table. This state corresponds to the normal braking process between times 0 and Z. ₁ according to FIG. 3. If output C ₂ is now energized when there is a risk of the vehicle wheel locking, while output ei remains de-energized, solenoid valve E ₂ is first excited directly and Ei is also excited via the second input of OR element 30 , as explained in detail above. This state is shown in line 2 of the table, FIG. 4, in logical form and corresponds to the time interval / ι ... I ₂ in FIG. 3 in which the pressure drop in the control room 18 takes place from the value p \ to the smaller value p ₂ , last the output e _{2 is switched} off and the output ei is switched on. The outlet solenoid valve E ₂ suddenly closes the associated outlet valve 23, 24, while the inlet solenoid valve Ei is only excited after the small time difference ti - t ₂ and the associated inlet valve 21, 22 closes. This state is shown in the table, FIG. 4. Shown in line 3, in which the pressure p ″ in the control chamber 18 rises from P ₂ to the somewhat increased value p _3. This value is approximately retained in the control chamber and the risk of locking the accelerating vehicle wheel is eliminated.

After a certain period of time, the control circuit 31 also switches off the output ei and it becomes again the state according to line 1 in FIG. 4 reached.

For this purpose 2 sheets of drawings

Claims (3)

Patent claims: l _t Blockierschutzejnriehtung for compressed air operated brake systems of vehicles, in particular road vehicles, with a relay valve with a piston-limited, can be acted upon via a closed upon energization inlet solenoid valve from an arbitrarily applied brake gradual proportional control pressure and the response of the anti-lock device via a to open upon energization purge solenoid valve deflatable control chamber and with a Connection for a valve chamber having a brake cylinder, the pressurization of which is monitored by means of a limiting piston-controlled inlet and outlet valve, the inlet valve being installed in a connection to a pressure medium source and the control chamber preferably being limited by two separate limiting pistons designed as diaphragm pistons, of which the one is connected to a closure member of the inlet valve and the other to a closure member of the outlet valve without play, un d with an electrical control circuit each with an output connection for the excitation of one of the two solenoid valves, characterized in that an OR element (30) is connected upstream of the coil of the inlet solenoid valve (Ei) , its output with the coil and one input via a delay element (29) with the inlet solenoid valve (Ex) closed output connection (e \) of the control circuit (31) and its other input parallel to the coil of the unloading solenoid valve (E ₂ ) to the other output connection (ei) assigned to it of the control circuit (31) is connected so that if there is a risk of a vehicle wheel locking, the control circuit (31) initially applies the output fa), which is assigned to the exhaust solenoid valve (E ₂ ) , to voltage alone and thereby applies both the exhaust solenoid valve (E ₂ ) and the OR element ( 30) energizes the inlet solenoid valve (E ₁ ) , whereby the control chamber (18) in the relay valve M) is vented and the wheel brake cylinder (10) via the diaphragm piston-controlled outlet valve ntil (15, 16) is also vented, and that subsequently to terminate the venting of the wheel brake cylinder (10) the control circuit (31) changes the voltage supply of the two outputs (ei and e?), whereby both solenoid valves (Ei and E ₂ ) drop out and, for this purpose, delayed by the delay time (h - t ₂ ) of the delay element (29) so that the inlet solenoid valve (Et ) is re-energized via the delay element (29) and thus, after a brief opening, the compressed air supply to the control chamber (18) of the relay valve (i) locked again. 2. Device according to claim I, characterized in that from the input connection (2) in the relay valve (1) a channel (19) with a nozzle (20) branches off, which via the inlet valve (21, 22) of the inlet solenoid valve (E \) to Control chamber (18) leads. 3. Device according to claim I, characterized in that the outlet valve (23, 24) of the outlet solenoid valve ^ C ₂ ) connects the Stcucrkammer (18) with a subspace (25) which is connected to the atmosphere via a nozzle (26). ^St. The invention relates to an anti-blocking device for pneumatic brake systems of vehicles with the generic term of the claim I mentioned features. Such an anti-lock device is in the older German Patent 23 35 321 described and illustrated. In other, known relay valves for anti-lock devices, for example according to DE-OS 16 30 544, the inlet and outlet valve is combined m a double seat valve, in which a spring-loaded closure member in its closed position the passage from the pressure medium source into the with. blocks the valve chamber connected to the brake cylinder and at the same time serves as a valve seat for an axially movable hollow spindle via which the valve chamber can be emptied. The spindle is connected to a piston which separates the valve chamber from the control chamber in a pressure-tight manner. When pressure is applied to the control chamber and thus to the piston on the control chamber side, the spindle lifts from its valve seat surrounding the passage opening to the valve chamber while resting on the closure member, so that pressure medium from the pressure medium source flows through the valve chamber to the brake cylinder while simultaneously acting on the piston in the opposite direction to the control pressure can and thus the vehicle brake can be operated. If the anti-lock device speaks due to an excessive delay of the braked Vehicle wheels, whereby the control chamber in a known manner via the electropneumatic Ventii is suddenly emptied, causes the pending on the side facing away from the control chamber on the piston Brake cylinder pressure a movement of the piston and thus the spindle connected to it in Direction to Sieuerkammer, whereby initially the closure member under the action of the burdening it Put the spring back on its seat and then lift the hollow spindle from the lock to open a To cause the brake pressure to flow away. The anti-lock device is used to reduce air consumption when there is a short change in response times according to the already mentioned DE-OS 16 30 544 provided that when downshifting the Anti-lock device the inlet solenoid valve for the control chamber by means of an upstream of this Delay device lagging for closing the exhaust solenoid valve opens to a simultaneous one Exclude the open position of these two solenoid valves. To accelerate the pressure increase in the Control chamber, this is parallel to the inlet solenoid valve via a constantly open throttle point to the Control pressure source connected. This known blockage protection device however, does not have any means of correcting undesired understeering explained below on. In addition, with this anti-lock device there is no possibility for often required to keep a reduced brake pressure constant. As has recently been shown from experimental measurements, a road vehicle wheel from Time of occurrence of excessive deceleration to block already within one revolution, so that between a signal indicating excessive deceleration and the reduction in brake pressure only an extremely short period of time may elapse if the wheel is reliably prevented from locking shall be. This means that clic blocking protection