DE4122643C2 - Hydraulic brake system with an anti-lock and traction control system for motor vehicles - Google Patents

Description

State of the art

The invention relates to a hydraulic brake system with an anti-lock and Traction control system for motor vehicles.

Such a brake system is known from DE 38 16 073 A1. In this brake system, a brake line leads one Brake circuit operated by a pedal master brake cylinder with pressure medium reservoir to a wheel brake. In the The brake line is a shut-off valve on the master cylinder side and a brake pressure modulation valve on the wheel brake side arranged. A high pressure pump stands with its suction side on the one hand via this valve with the wheel brake and on the other hand via a suction line with the pressure medium Storage container in connection. Located in the intake pipe a shut-off valve with a spring-operated open position. It is from that in the brake line between the Master cylinder and the shut-off valve prevailing pressure switchable. The pump is on the pressure side Delivery line, in which there is a damper chamber and Throttle point to the brake line between the Shut-off valve and the valve for brake pressure modulation connected. With the damper chamber and the throttle point should the pulsation of the pumped Pressure medium can be reduced.

In this known brake system takes place in the normal Brake operation, the pressure control in the wheel brake always  through the brake line. In anti-lock control mode Pressure medium from the wheel brake throttled by means of the pump released into the brake line. in the Traction control mode leads the throttle in the Pump delivery line, however, to an undesirable delayed pressure build-up in the wheel brake.

DE 38 42 370 A1 describes an anti-lock brake system known in the brake line leading to a wheel brake a shut-off valve is located downstream of a master brake cylinder, a throttle and a valve for brake pressure modulation are located. The throttle point leads to a reduced Pressure build-up speed with brake pressure control in the Wheel brake.

Furthermore, a brake system has already been proposed according to DE 40 34 113 A1, which has not been published beforehand, where there is a Master brake cylinder and a wheel brake a brake line extends in the downstream of the master cylinder Shut-off valve and a valve arrangement for Brake pressure modulation are arranged. A high pressure pump is on the one hand on this valve arrangement and on the other hand with an intake line to the brake line between the master brake cylinder and the shut-off valve connected. There is a in the suction line spring-operated shut-off valve. Is on the pressure side the pump via a delivery line with a damper chamber and a choke with the brake line between the Shutoff valve and the valve assembly connected.

With this brake system, this takes place in the intake pipe arranged shut-off valve only at Traction control operation its open position. At one triggered by the driver in this operating mode Braking can therefore be caused by the pressure medium for a short time Intake line and the pump in the brake line to build up of brake pressure flow into the wheel brake. As soon as that  Control unit of the brake system, however, the braking request of the Driver has recognized, it breaks the Traction control operation and switches that Shut-off valve in the brake line in the open position and the shut-off valve in the intake line in the Locked position. Pressure fluid can now flow through the brake line be moved from the master cylinder to the wheel brake.

Object and advantages of the invention

The invention is based, in Traction control the dynamics of the Improve brake pressure build-up without the comfort of To affect the braking system.

The hydraulic brake system according to the invention with the Features of the main claim has the following advantages:

In traction control mode is a very fast Pressure build-up in the wheel brake possible because of the High pressure pump pumped pressure medium without overcoming the Throttle point is fed into the brake line. in the Anti-lock control mode becomes the comfort of the brake system improved because the throttle point in the brake line Pressure build-up speed for brake pressure in the wheel brake decreased in the pressure build-up phase, which is advantageous the noise development and the pedal reaction affects. This remains despite relocation of the throttle point their pulsation-reducing effect in pressure build-up phases receive. It is also a major advantage that despite the arrangement of the throttle in the brake line from Driver-triggered, immediate braking is given: There the shut-off valve in the intake line also in normal Braking takes its open position, can Brake pressure medium through the intake line below Overcoming the pump-side check valves and the High pressure pump through the delivery line and the brake line flow instantly into the wheel brake.  

The measures listed in the subclaims provide for partial further training and improvements in the main claim specified braking system possible.

With the design of the brake system specified in claim 3 the advantage of fast in the brake circuit developed above Brake release bypassing the throttle point in the brake line receive.

The further development of the brake system characterized in claim 4 relates to the so-called K division of the brake circuit, d. H. the Both wheel brakes of the brake circuit are diagonally opposite Assigned vehicle wheels, with the second wheel brake in addition to that normal braking operation only anti-lock control operation possible is. It will also be the above mentioned in this training Advantages in anti-lock control mode on the second wheel brake of the Brake circuit achieved.

With the design of the brake system characterized in claim 5 is an instantaneous build-up of brakes for quick brake release pressure in the second wheel brake possible.

The further development of the brake system disclosed in claim 6 closes the variant of the so-called TT division of the brake circuit, d. H. the two wheel brakes of the brake circuit are two wheels of the assigned to the same vehicle axle. This also means that second wheel brake, on the anti-lock and traction control rule operation is possible, these operating conditions and the advantages associated with fast brake loops achieved.  

drawing

Two embodiments of the invention are explained in more detail in the following description with reference to circuit diagrams of a hydraulic brake system for motor vehicles. In the drawings Fig. 1 is a circuit diagram of a brake system with diagonal brake circuit allotment, and Fig. 2 is a circuit diagram of a brake system layout with achsweiser brake circuit.

Description of the embodiments

The hydraulic brake system 10 shown in FIG. 1 as the first exemplary embodiment has two brake circuits I and II. The brake circuits I and II have the so-called K division, ie two diagonally opposite wheels of the vehicle are connected to each brake circuit. In addition, the brake system 10 is equipped with an anti-lock and traction control device 11 .

The brake system 10 has a master brake cylinder 15 which can be actuated by a brake pedal 14 and has a pressure medium reservoir 16 attached to it. A first brake line 17 of the brake circuit I starts from the master brake cylinder 15 . The brake line 17 leads to a first wheel brake 18 , which is assigned to the driven left front wheel (not shown) of the vehicle, for example. A second brake line 19 of the brake circuit I is connected to a second wheel brake 20 , which is assigned to the right rear wheel, not shown. The brake circuit II has a first brake line 21 , to which a wheel brake 22 associated with the right, driven front wheel (not shown) of the vehicle is connected. A second brake line 23 of the brake circuit II leads to a wheel brake 24 assigned to the left rear wheel (likewise not shown) of the vehicle. Since the two brake circuits I and II are equipped identically, only the brake circuit I is described in detail below.

Starting from the master brake cylinder 15, there is a first shut-off valve 27 in the first brake line 17 . This is designed as a 2/2-way valve with a spring-operated passage position 27 a and an electromagnetically switchable blocking position 27 b. The first shut-off valve 27 is bypassed by a first bypass line 28 with a first check valve 29 , which opens from the master brake cylinder 15 to the wheel brake 18 . A first throttle point 30 is located in the first brake line 17 between the shut-off valve 27 with the bypass line 28 and the wheel brake 18 .

The first wheel brake 18 of the brake circuit I is assigned a first valve arrangement 33 for brake pressure modulation. The valve assembly 33 has a 2/2-way valve inlet valve 34 with a spring-operated passage position 34 a and an electro-magnetically switchable blocking position 34 b. The inlet valve 34 is bypassed by a second bypass line 35 with a second check valve 36 , which has a passage direction from the wheel brake 18 to the master cylinder 15 . The second bypass line 35 is connected to the brake line 17 on the master cylinder side between the first shut-off valve 27 and the first throttle point 30 . The other end of the bypass line 35 is connected to the brake line 17 between the inlet valve 34 of the first valve assembly 33 and the wheel brake 18 .

A return line 39 with an outlet valve 40 of the first valve arrangement 33 extends from the first brake line 17 between the inlet valve 34 and the wheel brake 18 . The outlet valve 40 is designed as a 2/2-way valve with a spring-actuated blocking position 40 a and an electromagnetically switchable passage position 40 b. The return line 39 is connected to the suction side of a high-pressure pump 41 , which can be driven by an electric drive motor 42 . A pressure medium storage chamber 43 is connected to the return line 39 . Also connected on the pump side to the return line 39 is a suction line 44 connected to the master brake cylinder 15 or the pressure medium reservoir 16 . Between the connection of the pressure medium storage chamber 43 and the connection of the suction line 44 to the return line 39 there is a third return check valve 45 , which opens from the wheel brake 18 to the high pressure pump 41 and serves as a vacuum protection valve. From the pressure side of the high-pressure pump 41 , a delivery line 46 with a damper chamber 47 extends between the first throttle point 30 and the inlet valve 34 of the first valve arrangement 33 and opens into the first brake line 17 .

The high-pressure pump 41 is formed as a self-priming piston pump, ie it has a piston 49 which can be moved longitudinally against spring force and on which an eccentric 50 which can be driven by the drive motor 42 acts. On the suction side, the pump 41 has a spring-loaded check valve 51 with an opening pressure of about 0.2 bar; On the pressure side, the pump is assigned a spring-loaded check valve 52 with an opening pressure of approximately 5 bar.

In the intake line 44 , which is indirectly connected via the second brake line 19 of the brake circuit I between the master cylinder 15 and the first shut-off valve 27 to the first brake line 17 , there is a second shut-off valve 54 . This is designed as a 2/2-way valve with spring-operated passage position 54 a and electromagnetically switchable blocking position 54 b.

The second wheel brake 20 of the brake circuit I is also assigned a valve arrangement 55 with an inlet valve 56 lying in the second brake line 19 . The inlet valve 56 of this second valve arrangement 55 is designed as a 2/2-way valve with a spring-operated passage position 56 a and an electromagnetically switchable blocking position 56 b. The inlet valve 56 has an effective in the passage position 56 a, second throttle point 57th This can be arranged inside or outside of the inlet valve 56 and consist of a cross-sectional constriction of the second brake line 19 or of a plurality of series-constricted cross-sectional constrictions of larger diameter. The inlet valve 56 with throttle point 57 is bypassed by a third bypass line 58 , in which a check valve 59 opening from the second wheel brake 20 to the master brake cylinder 15 is arranged. From the second brake pipe 19 passes between the inlet valve 56 and the wheel brake 20, a return line branch 60, which opens out between the exhaust valve 40 of the first valve arrangement 33 and the high-pressure pump 41 in the return line. 39 In the return line branch 60 , an outlet valve 61 of the second valve assembly 55 is arranged. The outlet valve 61 is designed as a 2/2-way valve with spring-operated blocking position 61 a and electromagnetically switchable passage position 61 b. Finally, the brake circuit I with an outgoing from the first brake line 17 between the first shut-off valve 27 and the first throttle point 30 is provided over flow line 64 , which opens into the intake line 44 between the master brake cylinder 15 and the second shut-off valve 54 . In the overflow line 64 , a pressure relief valve 65 is arranged with the flow direction from the first brake line 17 to the intake line 44 .

The anti-lock and traction control device 11 of the brake system 10 also includes an electronic control unit 68 , which monitors the rotational behavior of the vehicle wheels (not shown) by means of speed sensors 69 , 70 , 71 , 72 and, according to predetermined control algorithms in anti-lock and drive control mode, the various valves of the brake system and the Drive motor 42 switches.

The multi-circuit brake system 10 has the following functions, which are described on the basis of the brake circuit I:

When braking is triggered by the driver of the vehicle, during which the valves of the brake system 10 assume the position shown, by actuating the master brake cylinder 15, pressure medium quantities in the brake lines 17 , 19 are shifted while overcoming the throttle positions 30 and 57 and in the wheel brakes 18 , 20 brake pressure generated. If a quick increase in brake pressure is desired by the driver, the brake pressure is transferred to the wheel brake 18 because of the throttling effect of the first throttle point 30 through the intake line 44 and by overcoming the pump-side check valves 51 and 52 through the high-pressure pump 41 and through the delivery line 46 in the brake line 17 . The hydraulic brake system 10 therefore has fast braking dynamics. When releasing the brake, in which the driver reduces the foot force on the brake pedal 14 , the pressure medium quantities flow from the wheel brakes 18 , 20 through the brake lines 17 , 19 back to the master brake cylinder 15 . If the driver reduces his foot power very quickly, the pressure medium from the first wheel brake 18 can bypass the first throttle point 30 in the first brake line 17 through the second bypass line 35 and the pressure medium from the second wheel brake 20 bypassing the second throttle point 57 in the inlet valve 56 of the second valve arrangement 55 flow back to the master brake cylinder 15 through the third bypass line 58 . During such normal braking operation, the electronic control unit 68 monitors the rotational behavior of all driving tool wheels on the basis of the signals from the speed sensors 69 to 72 . If, due to certain braking conditions, a high rate of pressure increase in the wheel brake 18 is to be excluded, this can be brought about by switching the second shut-off valve 54 into the blocking position 54 b triggered by the control unit 68 . The pressure medium must then make its way through the first brake line 17 with the throttle point 30 arranged therein, which results in a smaller pressure build-up gradient.

If, for example, such a braking threatens to block the driven vehicle wheel assigned to the first wheel brake 18 , the control unit 68 switches the first valve arrangement 33 into the switching position for pressure reduction, ie the inlet valve 34 in the first brake line 17 becomes the blocking position 34 b and that Exhaust valve 40 in the return line 39 is switched to the open position 40 b. Pressure medium can now flow out of the wheel brake 18 through the return line 39 into the pressure medium storage chamber 43 , so that the brake pressure in the wheel brake 18 drops. At the same time, the second shut-off valve 54 in the intake line 44 is switched into the blocking position 54 b by the control device 68 and the drive motor 42 of the high-pressure pump 41 is started. The high-pressure pump 41 conveys pressure medium from the wheel brake 18 and from the storage chamber 43 through the delivery line 46 and the first brake line 17 back to the master brake cylinder 15 . According to the control algorithms stored in the control unit 68, phases for pressure reduction and pressure build-up in the wheel brake 18 are connected to phases of the pressure reduction until the driven vehicle wheel shows stable turning behavior. In this case, the inlet valve 34 and the outlet valve 40 of the first valve arrangement 33 are switched into the blocking position 34 b and 40 a when the pressure is maintained. When pressure builds up, the outlet valve 40 assumes its blocking position 40 a, while the inlet valve 34 is switched into the passage position 34 a. Pressure medium can now flow on the way from the actuated master brake cylinder 15 through the first brake line 17 to the first wheel brake 18 . The first throttle point 30 in the brake line 17 causes a reduction in Druckaufbaufeschwin speed, which leads to a reduced noise when switching the inlet valve 34 and a reduced reaction on the brake pedal 14 . At the end of such an anti-lock control operation, the control unit 68 switches off the drive motor 42 of the high pressure pump 41 . Likewise, the second shut-off valve 54 in the intake line 44 is switched to the open position 54 a. Such anti-lock control operation is possible in a corresponding manner on all wheel brakes 18 , 20 , 22 , 24 of brake system 10 .

On the other hand, if the vehicle wheel assigned to the wheel brake 18 is subjected to impermissibly large drive slip when starting and accelerating the vehicle, this is also recognized by the control unit 68 on the basis of the signals from the speed sensors 69 to 72 . The control unit 68 switches the first shut-off valve 27 into the blocking position 27 b and sets the drive motor 42 of the high-pressure pump 41 into operation. At the same time, the inlet valve 56 of the second valve arrangement 55 in the second brake line 19 is switched into the blocking position 56 b. The remaining valves of the brake system 10 remain in the position shown. The high pressure pump 41 now sucks pressure medium from the pressure medium reservoir 16 through the master brake cylinder 15 and the intake line 44 . The pump 41 conveys the pressure medium through the delivery line 46 into the first brake line 17 and generates brake pressure in the wheel brake 18 . This brake pressure build-up is unrestricted and therefore takes place in a desired manner with high Druckan increase speed. In accordance with the specified control algorithms, further phases for pressure maintenance and pressure reduction also follow in the traction control mode at pressure build-up phases, in which the first valve arrangement 33 assigned to the wheel brake 18 assumes the switching positions already mentioned in the case of anti-lock control operation. In such a traction control operation provided by the pump 41 , not removed from the wheel brake 18, pressure medium is discharged through the overflow line 64 and the pressure relief valve 65 into the intake line 44 . The above-described traction control operation is also possible in the same way on the wheel brake 22 of the brake circuit II.

The second embodiment shown in Fig. 2 relates to a hydraulic brake system with TT division of the brake circuits I and II, ie the brake circuit I is the driven rear axle of the brake circuit II assigned to the non-driven front axle of the vehicle. For the following description of this brake system, the same reference numbers are used for the elements known from FIG. 1.

The brake circuit I of the hydraulic brake system 10 according to FIG. 2 has an anti-lock and traction control device 11 with which control operation in the brake circuit I and in the brake circuit II control operation, in the brake circuit I additionally traction control is also possible. In the following, reference is only made to the brake circuit I associated with the invention.

The brake circuit I, with which the wheel brakes 18 , 20 assigned to the driven rear wheels of the vehicle can be actuated, is largely identical to the brake circuit I of the first exemplary embodiment. The brake circuit I of the second exemplary embodiment differs from the first in that the second brake line 19 assigned to the wheel brake 20 extends from the first brake line 17 between the throttle point 30 arranged therein and the inlet valve 34 of the first valve arrangement 33 . On the other hand, the inlet valve 56 of the second valve arrangement 55 bypassing the third bypass line 58 with the check valve 59 on the master cylinder side of the second check valve 36 is connected to the second bypass line 35 . Furthermore, the inlet valve 56 of the second valve arrangement 55 is not assigned a throttle point, because the throttle point 30 arranged in the first brake line 17 influences the pressure increase speed of the brake pressure in both wheel brakes 18 , 20 . On both wheel brakes 18 , 20 of the brake circuit I, the same modes of operation are possible, as described for example in connection with the brake circuit I in the first embodiment.

Claims (6)

1. Hydraulic brake system ( 10 ) with an anti-lock and traction control device ( 11 ) for motor vehicles with the following features:

• - Brake master cylinder ( 15 ) which can be actuated by a pedal leads a brake line ( 17 ) of a brake circuit (I) to a wheel brake ( 18 ),
• - The wheel brake ( 18 ) is assigned a valve arrangement ( 33 ) for brake pressure modulation with an inlet valve ( 34 ) arranged in the brake line ( 17 ),
• - In the brake line ( 17 ) a first shut-off valve ( 27 ) is arranged on the master cylinder side, which assumes its locked position ( 27 b) in traction control mode,
• - A high-pressure pump ( 41 ) designed as a piston pump and equipped with a suction-side check valve ( 51 ) and a pressure-side check valve ( 52 ) is provided with an intake line ( 44 ) between the master brake cylinder ( 15 ) and the first shut-off valve ( 27 ) and with a delivery line ( 46 ) connected to the brake line ( 17 ) between the first shut-off valve ( 27 ) and the inlet valve ( 34 ),
• - In the intake line ( 44 ), a second shut-off valve ( 54 ) is arranged, which has a shut-off position ( 54 b) and a passage position ( 54 a), which the shut-off valve ( 54 ) assumes outside the anti-lock control mode,
• - The high pressure pump ( 41 ) is on the pressure side in the delivery line ( 46 ) arranged damper chamber ( 47 ) and in the brake line ( 17 ) between the first shut-off valve ( 27 ) and the connection of the delivery line ( 46 ) to the brake line ( 17 ) Throttling point ( 30 ) downstream.

2. Hydraulic brake system according to claim 1, characterized in that the second shut-off valve ( 54 ) in the intake line ( 44 ) is designed as a 2/2-way valve which assumes its open position ( 54 a) by spring actuation. 3. Hydraulic brake system according to claim 1, characterized in that the inlet valve ( 34 ) of the valve arrangement ( 33 ) for brake pressure modulation is bypassed by a bypass line ( 35 ) which on the one hand between the first shut-off valve ( 27 ) and the throttle point ( 30 ) and on the other hand is connected to the brake line ( 17 ) between the inlet valve ( 34 ) and the wheel brake ( 18 ), and that a check valve ( 36 ) opening from the wheel brake ( 18 ) to the master brake cylinder ( 15 ) is arranged in the bypass line ( 35 ). 4. Hydraulic brake system according to claim 1, characterized in that from the brake line ( 17 ) between the master cylinder ( 15 ) and the first shut-off valve ( 27 ) leads to a second wheel brake ( 20 ) of the brake circuit (I) second brake line ( 19 ) starts, in which an inlet valve ( 56 ) of a second valve arrangement ( 55 ) for brake pressure modulation in the second wheel brake ( 20 ) and a second throttle point ( 57 ) are arranged. 5. Hydraulic brake system according to claim 4, characterized in that the inlet valve ( 56 ) of the second valve arrangement ( 55 ) and the second throttle point ( 57 ) are bypassed by a bypass line ( 58 ) in which one of the second wheel brake ( 20 ) Master brake cylinder ( 15 ) opening check valve ( 59 ) is arranged. 6. Hydraulic brake system according to claim 3, characterized in that from the brake line ( 17 ) between the throttle point arranged therein ( 30 ) and the inlet valve ( 34 ) of the valve arrangement ( 33 ) for brake pressure modulation to a second wheel brake ( 20 ) of the brake circuit ( I) leading second brake line ( 19 ), in which an inlet valve ( 56 ) of a second valve arrangement ( 55 ) for brake pressure modulation in the second wheel brake ( 20 ) is arranged, and that a bypass line ( 58 ) bypassing this inlet valve ( 56 ) with to the master brake cylinder ( 15 ) opening check valve ( 59 ) is connected to the bypass line ( 35 ) of the inlet valve ( 34 ) of the first valve arrangement ( 33 ) ( Fig. 2).