Patent Application
20110018338
The invention relates to a hydraulic brake system according to the preamble of claim 1, a pilot control assembly for a brake system of that type, according to claim 8, and a hydraulic brake system according to claim 12.
Heavy vehicles that are used in construction, agriculture, and forestry, and special vehicles must include brake systems that have a high level of operational reliability despite low operating forces, especially for use on difficult terrain. In vehicles of this type, power brake systems are used in which the braking force is not applied directly by the driver, but rather directly via a hydraulic accumulator or the like. Hydraulic external force systems and pneumatic external force systems are basically known, although hydraulic systems are often preferred since it is very easy to supply energy via hydraulic systems that are already present on the vehicle, and since hydraulic components, in particular the wheel brake cylinder, require less space than pneumatic components, they allow highly precise applications to be carried out due to the low hysteresis involved, and they ensure short response times even at low temperatures.
Hydraulic power brake systems of this type are described in data sheet RD 66 226/06.00 from Mannesmann Rexroth AG. According to that data sheet, in a 2-circuit power brake system, a pressure medium connection between the wheel brake cylinders of the particular brake circuit and one hydraulic accumulator in each case is controlled open via a power brake system valve that is actuated using a brake pedal. The hydraulic accumulator is charged via an accumulator charge valve by a pump that supplies the brake system with pressure medium with priority over the other loads as soon as the accumulator pressure drops below a limit value. When the power brake system is actuated, the pressure in the wheel brake cylinders is regulated in proportion to the actuating force of the pedal. In the case of fast-moving vehicles in particular, the aim is to provide the power brake systems with an ABS functionality. Since the wheel brake cylinders of hydraulic power brake systems of this type have a very large intake volume, ABS systems from the automotive industry may not be used since their valves are designed for the small intake volumes of these brakes. Although ABS solutions for pneumatic power brake systems are known, they require a great deal of installation space due to the low energy density of compressed air, and they have the disadvantages described above. Hydraulic solutions are therefore preferred.
Publication WO 92/03321 discloses a brake system comprising a hydraulic antilock braking and traction control device for a vehicle. In this brake system, a wheel brake is actuated using a main brake cylinder during normal operation. When antilock braking or traction control is actuated, the main brake cylinder is disconnected via a directional control valve, and an ABS or TCS device is connected. It comprises a pump, a hydraulic accumulator, and an actuating device, and then controls the wheel brake independently of the main brake cylinder. This solution has the disadvantage that e.g. during ABS- and/or traction control, it is not possible to access the brake pressure of the main cylinder, but only the pressure of the ABS or TCS device, which is generated by the pump.
US 2005/0242660 likewise shows an antilock device and a traction control device of a brake system for a vehicle. In that case, the brake system comprises two brake circuits, each of which includes a hydraulic accumulator, wherein the brake circuits can apply pressure medium to the brake cylinders of two wheels independently of each other and via manual actuation of a power brake system by a vehicle driver. Furthermore, the ABS and TCS devices include a wheel valve for one brake cylinder each, the wheel valve being capable of controlling open the connection of the brake cylinder to the assigned brake circuit or a central functional valve. The functional valve opens a pressure medium connection between the wheel valve and a tank, or between the wheel valve and a further hydraulic accumulator, wherein, in the case of the latter pressure medium connection, the brake cylinders can be supplied with pressure medium independently of a manual actuation of a power brake system. The disadvantage of this is that both brake circuits are connected to a common functional valve, and they can therefore be operated either in the antilock mode or the traction control mode, but the two cannot be operated in different modes. In addition, the power brake system and the ABS and TCS devices each include a hydraulic accumulator, thereby resulting in a high level of device complexity.
Publication DE 10 2006 020 890 shows a brake system for ABS-, TCS-, and/or ESP-control. It comprises a hydraulic block having substantially more electromagnetically switchable valves, a hydraulic accumulator, and a hydraulic pump for the hydraulic control of a wheel brake cylinder with or without actuation of a power brake system. The power brake system is supplied with pressure medium by an accumulator charge valve and hydraulic accumulators connected thereto. The disadvantage of this solution is that the brake system has a highly complex design since the hydraulic block and the power brake system each require a pressure medium supply in the form of a hydraulic pump and a hydraulic accumulator.
In contrast, the object of the present invention is to create a brake system that has a simple design and can be used in a flexible manner.
This object is solved by a hydraulic brake system having the features of claim 1, a pilot control assembly for a brake system of that type, which has the features of claim 8, and a hydraulic brake system having the features of claim 12.
According to the invention, a hydraulic brake system includes at least one manually actuated brake valve, via which it is possible to control open a pressure medium connection between at least one brake line, which has a pressure medium connection to a wheel brake cylinder, and a hydraulic accumulator. A wheel valve and a circuit valve are disposed in the pressure medium flow path between the wheel brake cylinder and the brake valve. The wheel brake cylinder can be controlled closed via the wheel valve, or it can be connected to the brake valve or a tank, and the wheel valve can be connected via the circuit valve to the hydraulic accumulator independently of the manual actuation of the brake valve. In this configuration, two brake circuits are provided, for example, and a circuit valve is assigned to each brake circuit.
This solution has the advantage that the brake circuits can be controlled independently of each other, and by the brake valve via the particular circuit valves. It is therefore made possible to control the brake circuits of a vehicle in a highly individualized manner, wherein e.g. a brake circuit can be operated in an ABS mode, and the other can be operated in an ESP mode, and the brake circuits can be supplied with either brake pressure from the brake valve or the hydraulic accumulator.
The circuit valve is preferably an electrically or hydraulically continually adjustable 3-port directional control valve, the valve spool of which can be displaced out of a spring-loaded neutral position in the direction of a blocking position and a working position. In the neutral position of the circuit valve, the pressure medium connection between the wheel valve and the brake valve is controlled open, and, in the working positions, the pressure medium connection between the wheel valve and the hydraulic accumulator is controlled open. This is a cost-effective standard valve.
According to another preferred embodiment, the circuit valve is an electrically or hydraulically adjustable 2-port directional control valve comprising a valve spool. The valve spool is switchable from a spring-loaded blocking position into a working position, wherein, in the working position, the pressure medium connection between the hydraulic accumulator and the wheel valve is controlled open. The circuit valve is therefore an extremely simple and cost-effectively designed directional control valve.
In addition to the circuit valve, which is designed as a 2-port directional control valve, a further circuit valve can be provided, which is designed as an electrically or hydraulically adjustable, 2-port directional control valve. A valve spool of the second circuit valve is advantageously switched from a spring-loaded working position into a blocking position, wherein, in the working position, the pressure medium connection between the brake valve and the wheel valve is controlled open.
The wheel valve, similar to the circuit valve, is an electrically or hydraulically continually adjustable 3-port directional control valve, the valve spool of which is displaceable from a spring-loaded neutral position in the direction of a blocking position and a working position, wherein in the spring-loaded neutral position, the connection between the wheel brake cylinder and the circuit valve is controlled open and, in the working positions, the connection between the wheel brake cylinder and the tank is controlled open.
According to further preferred embodiment, the wheel valve is a cost-effective, electrically or hydraulically switchable 2-port directional control valve comprising a valve spool. The valve spool is switchable from a spring-loaded working position into a blocking position, wherein, in the working position, the connection between the wheel brake cylinder and the circuit valve is controlled open.
To relieve brake pressure from a wheel brake cylinder, a further wheel valve, which is designed as an electrically or hydraulically switchable, 2-port directional control valve comprising a valve spool is disposed in the pressure medium connection between the wheel brake cylinder and the wheel valve. This valve spool is switchable from a spring-loaded blocking position into a working position, wherein, in the working position, the connection between the wheel brake cylinder and the tank is controlled open.
The wheel valves and circuit valves can be easily controlled electromagnetically e.g. using an ECU (electronic control unit) via signal lines, or hydraulically via a pilot control assembly, wherein the latter solution enables higher forces to be generated for controlling the valves.
The valve spool of the wheel valve can be acted upon in the direction of the spring-loaded neutral position by a pilot control pressure of the pilot control assembly and, in the opposite direction, by pressure in the wheel brake cylinder, and the circuit valve can be acted upon in the direction of the spring-loaded neutral position by the pressure in the brake line between the circuit valve and the wheel valve, and in the opposite direction by a pilot control pressure from the pilot control assembly, thereby enabling the wheel and circuit valves to be controlled very rapidly.
The pilot control assembly is designed e.g. with inlet valves and outlet valves that are assigned to each of two brake circuits. Using the outlet valve, a pressure medium connection between at least one of the wheel valves and the tank can be controlled open, and, using the inlet valve, at least one wheel valve can be connected via a switching valve of the pilot control assembly to the brake valve or a high pressure control valve of the pilot control assembly. The high pressure control valve advantageously has a pressure medium connection to the hydraulic accumulator, and a circuit valve can be connected between the pressure medium flow path of the inlet valves and the switching valve and the high pressure control valve. A pilot control assembly of that type has the advantage that it can be supplied with pressure medium by the hydraulic accumulator of the brake system, thereby eliminating the need for a separate pump or accumulator element, for instance.
The inlet valves, outlet valves, switching valve, and the high pressure control valve are electrically continually adjustable 2-port directional control valves, which can be displaced from a spring-loaded neutral position in the direction of a working position or blocking position, thereby resulting in a very simple design of the pilot control assembly.
Two brake circuits advantageously each include two wheel valves and one circuit valve, and the brake circuits can be controlled jointly using one brake valve using a manual foot brake.
According to a further advantageous embodiment of the brake circuits, each one includes a circuit valve, a brake valve, a wheel valve, and a wheel valve that can be assigned to both brake circuits. The assignable wheel valve can be connected via a sequence valve to the brake circuit having the lower pressure. A “Y” braking circuit, which is often used e.g. in tractors, is thereby made possible.
A preferred embodiment of the hydraulic brake system includes at least one manually actuated brake valve, via which a pressure medium connection can be controlled open between at least one brake line, which has a pressure medium connection to a wheel brake cylinder, and a hydraulic accumulator, wherein a wheel valve is disposed in the pressure medium flow path between the wheel brake cylinder and the brake valve, via which the wheel brake cylinder can be controlled closed or connected to the brake valve or a tank. An ECU is used to control the wheel valve and can also control the brake valve, e.g. using an actuating device, independently of the manual actuation. A brake system having a simple design is thereby made possible, using which e.g. ABS or ESP control takes place independently of the manual actuation of the brake valve.
Advantageously, the brake valve can be actuated hydraulically or electrically using an actuating device.
The brake valve is hydraulically actuated using a pilot valve or circuit valve. Using this, it is possible to connect or disconnect a pressure medium connection between the hydraulic accumulator and the brake valve. To relieve a pilot pressure that actuated the brake valve, the brake valve can be relieved to the tank via a further circuit valve. The two circuit valves are preferably cost-effective and robust, electrically or hydraulically switchable 2-port directional control valves.
The wheel valve can be an electrically or hydraulically continually adjustable standard 3-port directional control valve, the valve spool of which is displaceable from a spring-loaded neutral position in the direction of a blocking position and a working position, wherein in the spring-loaded neutral position, the connection between the wheel brake cylinder and the brake valve is controlled open and, in the working positions, the connection between the wheel brake cylinder and the tank is controlled open.
Two braking circuits preferably each have two wheel valves and can be controlled jointly using one brake valve.
It is also possible for two brake circuits to each have a brake valve, a wheel valve, and a wheel valve that can be assigned to both brake circuits. The assignable wheel valve can be connected via a sequence valve to the brake circuit having the lower pressure.
The sequence valve is e.g. an inverse directional control valve, and the wheel valve is a cardan brake valve, thereby making it possible to realize “steering braking” e.g. of a tractor.
Advantageous developments of the invention are the subject matter of the dependent claims.
Preferred embodiments are explained below in greater detail with reference to the schematic drawings. They show:
The basic design of brake valve 4, which is actuated via brake pedal 2, and accumulator charge valve 10, and the connection to hydraulic accumulators 6, 8 is described extensively in aforementioned data sheet RD 66 226/06.00, and therefore only the elements that are essential to the understanding of the invention will be described here; as for the rest, reference is made to the disclosure in said data sheet.
Accumulator charge valve 10 serves the purpose of holding a pressure level within certain limit values in the accumulator circuit. When hydraulic accumulators 6, 8 are being charged, pump 12 pumps pressure medium into an accumulator supply line 38 which is connected to the inlet of an inverse directional control valve 40. Its two outputs are connected via accumulator lines 42, 44 to accumulator ports S1 and S2 of brake valve 4. Hydraulic accumulators 6, 8 are connected to accumulator supply lines 42 and 44, respectively. When a default pressure is reached, a pressure medium connection to a load port is controlled open via accumulator charging valve 10, thereby making it possible to supply a secondary load, which is indicated in
Brake valve 4, or power brake valve, is a standard valve, e.g. of the type described in aforementioned data sheet RD 66 226/06.00, or in data sheet RD 66 146/10.03 from Bosch Rexroth AG. A brake valve 4 of this type includes aforementioned accumulator ports S1, S2, a tank port T, and brake ports BR1 and BR2 which are assigned to each brake circuit.
When brake pedal 2 is actuated, then, via brake valve 4, a pressure medium connection between accumulator ports S1, S2 and assigned output port BR1, BR2 is controlled open, thereby enabling brake pressure to build up in brake pressure lines 48, 50 which are connected to output ports BR1, BR2. Brake pressure lines 48, 50 are each connected to one pressure port KP of circuit valves 34, 36. Circuit valves 34, 36 furthermore each comprise an accumulator pressure port KS, wherein accumulator pressure port KS of circuit valve 34 is connected via a connecting line 51 to accumulator line 44, and accumulator pressure port KS of circuit valve 36 is connected via a connecting line 52 to accumulator line 42. Furthermore, circuit valves 34, 36 are connected via a respective outlet port KA to a wheel valve line 53, 54. Circuit valves 34, 36 are electrically continually adjustable 3-port directional control valves comprising a valve spool, which is preloaded by a spring 56 in a neutral position 0, working positions b and a blocking position a. In the direction of blocking position a and working position b, the valve spool of circuit valves 34, 36 can each be displaced against the force of spring 56 using an electromagnetic operating element 58 which is connected via an electrical signal line 60, 62 to ECU 14. In de-energized neutral position 0 of circuit valves 34, 36, outlet port KA is connected to pressure port KP, and accumulator pressure port KS is controlled closed, thereby establishing a pressure medium connection between brake pressure line 48, 50 and wheel valve line 53, 54 in each case. In blocking position a, all ports are controlled closed; in working positions b, wheel valve line 53, 54 is connected via outlet port KA to connecting line 51, 52, which is connected to accumulator pressure port KS, and outlet port KP is controlled closed.
Wheel valve lines 53, 54 each branch off into two supply lines 64, 66 and 68, 70, each of which is connected to a pressure port P of wheel valves 16 through 22, the design of which is described in greater detail below. Each wheel valve 16 through 22 has a brake port A which is connected via one brake line 72, 74, 76, 78 to assigned wheel brake cylinder 26, 28, 30, 32. Each wheel valve 16 through 22 also includes a tank port T which is connected to a tank 80. Wheel valves 16 through 22, similar to circuit valves 34, 36, are electromagnetically continually adjustable 3-port directional control valves comprising a valve spool that is preloaded in neutral position 0 using a spring 82, the valve spool being displaceable into working positions b and blocking position a against the acting direction of the spring force using an electrical operating element 84. Operating elements 84 of wheel valves 16, 18, 20 and 22 are each electrically connected via a signal line 86, 88, 90 or 92 to ECU 14. In de-energized, spring-preloaded neutral position 0 of wheel valve 16 through 22, brake port A has a pressure medium connection to pressure port P and, therefore wheel brake cylinders 26 through 32 have a pressure medium connection to lines 64 through 70. In blocking position a, brake-, pressure-, and tank ports A, P, T are controlled closed, and in working positions b, particular wheel brake cylinder 26 through 32 is connected, without pressure, via brake port A to tank port T, and pressure port P is closed.
Brake system 1 shown in
Wheel and circuit valves 16, 18, 20, 22, 34 and 36 are connected, as described above, via signal line 60, 62, 86, 88, 90 and 92, respectively, to ECU 14. ECU 14 is a central programmable control device that enables ABS-, TCS-, and/or ESP-control of brake system 1. The mode of operation of a control of that type has been known for some time from the prior art, and so means of controlling brake system 1 that are intended merely as examples will be explained below.
When braking is performed without an ABS-, TCS- and/or ESP-intervention of a vehicle equipped with brake system 1, wheel and circuit valves 16, 18, 20, 22, 34 and 36 are de-energized in their spring-loaded neutral position 0, as shown in
If the brake pressure specified by the vehicle driver using brake pedal 2 is too high and blocks one or more wheels of the vehicle, this brake pressure on the blocking wheels is relieved by controlling wheel valve 16, 18, 20 or 22 assigned to the blocking wheel in the direction of working positions b using ECU 14, thereby connecting corresponding wheel brake cylinder 26, 28, 30 and 32 to tank 80. When the blocking of one or more wheels has ended, corresponding wheel valve 16, 18, 20 or 22 is displaced once more in the direction of spring-loaded neutral position 0, and therefore corresponding wheel brake cylinder 26, 28, 30 or 32 is brought back into a pressure medium connection via brake valve 4 to hydraulic accumulators 6, 8, and is acted upon with brake pressure.
When control of brake system 1 is fully active (i.e. independently of the vehicle driver), circuit valves 34, 36 are controlled by the ECU into working positions b, thereby establishing the pressure medium connection of brake circuits 94, 96 to hydraulic accumulators 6, 8 independently of brake valve 4. It is also possible to displace only one of the two circuit valves 34, 36 in the direction of working position b. If e.g. pressure builds up in a single wheel brake cylinder 26 in brake circuit 94 shown on the left in
If the brake pressure specified by the vehicle driver using brake pedal 2 is not sufficient e.g. for ABS braking with subsequent ESP engagement, additional braking pressure is built up in brake circuits 94, 96 via hydraulic accumulator 6, 8 by switching circuit valves 34, 36 into working positions b.
If e.g. an interference occurs with the vehicle electrical system, brake circuits 94, 96 cannot be controlled using ECU 14, but normal braking function is still made possible by brake pedal 2 and brake valve 4.
The pressure medium supply corresponds to that of the embodiment shown in
Inverse directional control valve 106 has two input ports X, Y, each of which can be connected to a common output port Z. Input port X is connected to a valve line 112 which branches away from wheel valve line 53 upstream of wheel valve 16, and input port Y is connected accordingly to a valve line 114 that branches away from wheel valve line 54 upstream of wheel valve 22. Outlet port Z is connected to a supply line 115 which is connected to pressure port P of cardan brake valve 102. As mentioned above, cardan brake valve 102 corresponds to wheel valves 16, 22 and therefore has a working port A that has a pressure medium connection to wheel brake cylinder 104 via a brake line 116, and a tank port T. Furthermore, the valve spool of cardan brake valve 102 is displaceable from a spring-loaded neutral position 0, by energizing operating elements 84, in the direction of blocking position a and working position b, and furthermore cardan brake valve 104 can be controlled via signal line 117 via ECU 14. Inverse directional control valve 106 connects outlet port Z to respective inlet port X, Y at which the lower brake pressure exists, thereby establishing a pressure medium connection between cardan brake valve 102 and brake circuit 94, 96 having the lower brake pressure.
Brake valve 98 shown on the left in
The Y-branching of brake circuits 94, 96 shown in
Brake circuit 94 shown in
As also shown in
In addition to above-described circuit valve port VK and wheel ports VA1, VA2, pilot control assembly 118 also includes a brake pressure port VB which branches off from brake pressure line 48 via a pilot control brake line 132, a pilot control pressure port VP which is connected to hydraulic accumulator 6 via accumulator line 44, and a tank port T which is connected to tank 80. The design of pilot control assembly 118 is explained with reference to
Inlet valves 134, 136 are open in a neutral position 0, which is preloaded by a spring, and can be brought into a blocking position a by energizing a solenoid. In neutral position 0 of inlet valves 134, 136, a pressure line 150, which is connected to a pressure port EP of inlet valves 134, 136, has a pressure medium connection to an inlet line 146, 148, which is connected to an inlet port EA of inlet valves 134, 136, respectively. Inlet valves 146, 148 are connected via wheel ports VA1, VA2 to pilot control lines 124, 126 of wheel valves 16, 18 depicted in
An outlet line 152, 154, each of which is connected to a pressure port AP of outlet valves 138, 140, branches off from inlet line 146, 148, respectively. Outlet valves 138, 140 are closed by the spring in neutral position 0, and can be displaced in the direction of an open working position s by energizing the solenoid. In working positions s of outlet valves 138, 140, outlet lines 152, 154 are connected to tank port T and, therefore, tank 80 shown in
An outlet line 157 branches off from pressure line 150; outlet line 157 is connected to an outlet port UA of switching valve 142, and can be connected to brake pressure port VB via a pressure port UP of switching valve 142 with pressure line 160. As is the case with inlet valves 134, 136, the valve spool of switching valve 142 of switching valve 142 can be displaced from open, spring-loaded neutral position 0 in the direction of blocking position a by energizing the solenoid. Furthermore, an outlet line 158 that is connected to outlet port HA of high pressure control valve 144 branches off from pressure line 150. The valve spool of high pressure control valve 144 can be moved, by energizing the solenoid, from closed, spring-loaded neutral position 0 in the direction of open working position s, and establishes a pressure medium connection between outlet line 158 and a pressure line 162 connected to a pressure port HP of high pressure control valve 144, pressure line 162 being further connected to pilot control pressure port VP. Circuit valve port VK of pilot control assembly 118 likewise has a pressure medium connection to pressure line 150 via a pilot control line 163. A non-return valve 164 that is open toward pressure line 157 is assigned to switching valve 142 to relieve pressure more rapidly in outlet line 157.
The design of a pilot control assembly of that type is made possible e.g. via a simple modification of a hydraulic block from aforementioned publication DE 10 2006 020 890, which will be described briefly below. Instead of a hydraulic accumulator of the hydraulic block, which is usually present, tank port T of pilot control assembly 118 is formed. A non-return valve of the hydraulic block between an outlet valve and a return pump is omitted, and the connection is separated; a return pump and an electric motor are also omitted, for which circuit valve port VK of pilot control assembly 118 for circuit valve 34 shown in
The mode of operation of pilot control assembly 118 will be explained below with reference to
KV directly to pilot control line 122. The same applies for wheel valves 16, 18. They are likewise held in spring-loaded neutral position 0 since the brake pressure acts in both directions of displacement of the valves. In one direction the brake pressure acts via control lines 128, 130, and in the other direction it acts via pilot control lines 124, 126, wherein the brake pressure is switched through via switching valve 142 and inlet valves 134, 136 of pilot control assembly 118.
If circuit valve 34 should be controlled in the direction of working positions b for direct connection to hydraulic accumulator 6 within the scope of ABS-, TCS-, and/or ESP-control when brake valve 4 is not actuated, switching valve and high pressure control valve 142, 144, respectively, of pilot control valve 118 are energized, and switching valve 142 is moved into blocking position a, and high pressure control valve 144 is moved into working position s. The brake pressure from hydraulic accumulator 6 therefore reaches pilot control line 122 via high pressure control line 144 and displaces circuit valve 34 via blocking position a toward working positions b, thereby controlling open a pressure medium connection of accumulator pressure port KS of circuit valve 34 via accumulator line 120 to hydraulic accumulator 6, and brake circuit 94 can be supplied with pressure medium. Wheel valves 16, 18 are therefore connected via brake valve 4 or circuit valve 34 to hydraulic accumulator 6.
If brake pressure is reduced e.g. by ABS control of brake pressure cylinder 28, inlet and outlet valves 134, 138, respectively, are switched, thereby blocking the pressure medium connection between pressure line 150 and inlet line 146, and opening the pressure medium connection between outlet line 152 and tank line 156. Pilot control line 126, which is connected to wheel port VA1 of pilot control assembly 118, is relieved toward tank 80, and therefore the valve spool of wheel valve 18 is displaced by the brake pressure of brake line 74, which is present in signal line 130 in the direction of its position labelled “b”, and, in blocking position a, the pressure medium connections between ports A, P, T are initially blocked via the control edges. In working position b, the brake pressure in brake lie 74 is reduced via tank port T toward tank 80. Via fast-switching valves 134, 138 of pilot control assembly 118, which are designed to be sufficiently large for the low control oil volumetric flows that occur, wheel valve 18, which is designed to accommodate a large volumetric flow of pressure medium, may therefore be switched very rapidly to build brake pressure or reduce brake pressure; the desired brake pressure is regulated by activating valves 134, 90 in a suitable manner.
The above-described ABS-, TCS-, and/or ESP-control by hydraulic pilot control 118 shown in
Two further embodiments of brake system 1 are explained in
In contrast to the first embodiment shown in
By braking, independently of the manual actuation of brake pedal 2, brake pressure can be reduced in both brake circuits 94, 96 using brake valve 4 via the actuating device which is controlled by ECU 14. If e.g. only one wheel brake cylinder 26 should be acted upon with brake pressure, wheel valves 18, 20, and 22, which are assigned to the other wheel brake cylinders 28, 30, and 32, are controlled into blocking positions a and working positions b.
When different brake pressure requirements are placed on wheel brake cylinders 26, 28, 30 or 32, the highest required brake pressure is reduced via brake valve 4 in brake circuits 94, 96, and the brake pressure of wheel brake cylinders 26, 28, 30 or 32 having lower brake pressure demand is controlled using respective wheel valves 16, 18, 20, or 22.
A fifth embodiment of a schematic circuit diagram of hydraulic braking system 1 is shown in
Wheel valve lines 53, 54 are connected directly to brake ports BR1 and BR2, respectively, of brake valves 98, 100. Brake valve 98 is operatively connected to ECU 14 via a signal line 170, and brake valve 100 is operatively connected to ECU 14 via a signal line 172, and are actuated electrically or hydraulically using an actuating device as shown in
Wheel inlet valves 176 and 178 for wheel brake cylinders 26 and 28 each have a pressure port RP, which is connected to supply line 64 and 66, and a brake port RA which is connected to brake line 72 and 74. An outlet line 188 and 190, each of which is connected to a brake port RB of wheel outlet valve 180 and 182, respectively, branches off from inlet line 72, 74, respectively. Each of these has a tank port RT which is connected to a tank line 192 and 194, wherein tank lines 192, 194 lead into tank 80.
Wheel inlet valves and wheel outlet valves 176, 178 and 180, 182, respectively, are each designed as electromagnetically actuated 2/2 switching valves. A particular valve spool of wheel inlet valves 176, 178 is preloaded via spring 82 in a neutral position h, in which pressure port RP has a pressure medium connection with brake port RA. Using electrical operating element 84, the valve spool can be switched to blocking position i, in which pressure port RP and brake port RA are separated from each other.
A valve spool of wheel outlet valves 180 and 182 is preloaded via spring 82 in a neutral position j, in which brake port RB is separated from tank port RT, thereby blocking the pressure medium connection between wheel brake cylinder 26 and 28 to tank 80. Via operating element 84, the valve spool of wheel outlet valves 180 and 182 can be switched to working position k, in which the pressure medium connection between wheel brake cylinder 26 or 28 and tank 80 is open.
Operating elements 84 are electrically connected to ECU 14 via signal lines 196, 198, 200, 202.
First and second circuit vales 184 and 186 are each designed as electromagnetically actuated 2/2 switching valves, as are wheel inlet valves and wheel outlet valves 176, 178 and 180, 182.
First circuit valve 184, which is shown on the right in
Second circuit valve 186, which is shown on the left in
When braking is performed without an ABS-, ASR- and/or ESP-intervention of a vehicle equipped with brake system 1, wheel and circuit valves 176, 178, 180, 182, and 184, 186 are de-energized in their spring-loaded neutral position h, j, or n, l, as shown in
If the brake pressure specified by the vehicle driver using brake pedal 2 is too high and blocks one or more wheels of the vehicle, this brake pressure on the blocking wheels is relieved by switching wheel outlet valve 180 or 182, which is assigned to the blocking wheel, into working position k, and switching wheel inlet valve 176 and 178 to blocking position i using ECU 14, thereby connecting corresponding wheel brake cylinder 26 or 28 to tank 80. When the blocking of one or more wheels has ended, corresponding wheel inlet valves and wheel outlet valves 176, 180, and 178, 182 are displaced once more in the direction of spring-loaded neutral position h, j, and therefore corresponding wheel brake cylinder 26 or 28 is brought back into a pressure medium connection via brake valve 4 to hydraulic accumulator 6, and is acted upon with brake pressure.
When control of brake system 1 is fully active (i.e. independently of the vehicle driver), first and second circuit valves 184 and 186 are switched by ECU 14 into positions m and o, respectively, thereby establishing the pressure medium connection of brake circuit 94 to hydraulic accumulator 6 independently of brake valve 4. If e.g. pressure builds up in single wheel brake cylinder 26 shown on the left in the figure, the valve spool of wheel inlet valve 178, which is assigned to the other, right-hand wheel brake cylinder 28 in brake circuit 94, is switched into blocking position i, and therefore brake pressure from hydraulic accumulator 6 is applied only to wheel brake cylinder 26.
If different setpoint brake pressures of two wheel brake cylinders 26, 28 should be realized in brake circuit 94, wheel brake cylinder 26 having the higher brake pressure is controlled via circuit valves 184, 186, and wheel brake cylinder 28 having the lower brake pressure is controlled via assigned wheel inlet valves and wheel outlet valves 178, 182.
If the brake pressure specified by the vehicle driver using brake pedal 2 is not sufficient e.g. for ABS braking with subsequent ESP engagement, additional braking pressure is built up in brake circuit 94 via hydraulic accumulator 6 by switching circuit valves 184 and 186 into positions m and o, respectively.
The second brake circuit, which is not depicted in
First circuit valve 210, which is shown on the right in
A valve spool of first circuit valve 210 shown on the right in
A valve spool of second circuit valve 212 is preloaded via spring 82 in working position u, in which pilot control port V of brake valve 4 is connected to tank 80 via pilot control line 216, discharge line 218, and tank line 220. When the valve spool is displaced by operating element 84, which is connected to ECU 14 via a signal line 224, into a blocking position v, the pressure medium connection between pilot control port V and tank 80 is blocked by circuit valve 212.
For fully active control of brake system 1 depicted in
If brake valve 4 has been opened by circuit valves 210, 212, wheel brake cylinders 26 and 28 have a pressure medium connection with hydraulic accumulator 6 via wheel inlet valves 176 and 178.
If only one of the wheel brake cylinders 26 or 28 should be actuated, the other—as described with reference to FIG. 7—is connected to tank 80 via opened wheel outlet valve 180 or 182, and is separated from hydraulic accumulator 6 via closed wheel inlet valve 176 or 178.
If different brake pressure is required at wheel brake cylinders 26, 28, the activation of brake valve 4 is controlled in accordance with the requirement of wheel brake cylinder 26, 28 having the highest pressure, via circuit valves 210, 212. Wheel brake cylinder 26 or 28 having the lowest pressure is controlled via wheel outlet valve 180 and 182, and wheel inlet valve 176 and 178.
If circuit valves 210, 212 are de-energized, the pilot control pressure of the pilot control of brake valve 4 is relieved toward tank 80, and the brake valve is closed once more, except that it is also actuated using brake pedal 2. When brake valve 4 is closed, the brake pressure in wheel brake cylinders 26, 28 is relieved via brake valve 4 toward tank 80.
A schematic circuit diagram of brake valve 1 according to an eighth embodiment is shown in
The relieving of brake valve 1 corresponds approximately to the fifth embodiment shown in
Similar to the depiction shown in
First circuit valve 230 of the two other circuit valves 230, 232, which are assigned to second brake valve 100, is connected via accumulator line 234 to accumulator line 42, and via pilot control line 236 to pilot control port V of brake valve 100. Second circuit valve 232 has a pressure medium connection via discharge line 238 to pilot control line 236, and via tank line 240 to tank 80.
Brake valves 98 and 100 are controlled using circuit valves 210, 212 and 230, 232 in a manner corresponding to that for brake valve 4 having circuit valves 210, 212 depicted in
As an alternative, instead of circuit valves 210, 212 or 230, 232 depicted in
Wheel inlet valves 176, 178, 226, wheel outlet valves 180, 182, 222, and circuit valves 184, 186, 210, 212, 230, 232 are designed, in
A hydraulic brake system is disclosed that includes at least one brake valve which is manually actuated and via which it is possible to control open a pressure medium connection between at least one brake line, which has a pressure medium connection to a wheel brake cylinder, and a hydraulic accumulator. A wheel valve is disposed in the pressure medium flow path between the wheel brake cylinder and the brake valve, the wheel valve being controllable independently of the manual actuation of the brake valve via a circuit valve or an actuating device which actuates the brake valve. The brake system can include a plurality of brake circuits, to each of which a circuit valve is assigned. In addition, the wheel and brake valves are controlled electrically or pilot-controlled in a hydraulic manner.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2008 023 476.1 | May 2008 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/DE2009/000684 | 5/13/2009 | WO | 00 | 9/27/2010 |
