Brake system for a work machine

Abstract

The invention relates to a braking system for a machine. The braking system comprises at least a first brake (20), a second brake (22), a third brake (24), a fourth brake (26), a first brake pressure valve unit (40), a second brake pressure valve unit (42), a first pressure reservoir (28), a second pressure reservoir (30), an operating device (52), and a control device (50). The first brake pressure valve unit (40) and the second brake pressure valve unit (42) are configured to switch to pressure control via the operating device (52) in the event of an electrical control failure by the control device (50). The invention also relates to a machine with a first axle (10), a second axle (12), and the braking system.

Description

Technical area

[0001] The present invention relates to a braking system for a work machine. The present invention also relates to a work machine. State of the art

[0002] A braking system on off-road machinery is often operated with pneumatic or hydraulic pressure and controlled by valves. However, with valves controlled solely by pressure, implementing additional braking functions is very complex. In addition, the functional safety of braking systems is very important. For example, due to regulatory requirements, it is usually necessary to provide an auxiliary brake in addition to a regular service brake and to ensure the functionality of the braking system through redundancies. This can make the braking system very complex and expensive, and also require a lot of space in the off-road machinery. Electrical control of valves in the braking system of off-road machinery also makes it difficult to achieve sufficient functional safety.

[0003] US 2022 / 185274 A1 describes an intelligent braking system for a tractor. Description of the invention

[0004] The present invention relates to a braking system for a work machine. The braking system can be designed to decelerate the work machine while traveling. The braking system can be designed to hold the work machine at a standstill. The braking system can be designed to provide further braking functions. The work machine can be designed, for example, as an agricultural machine or a construction machine. An example of an agricultural machine is a tractor. The work machine can be designed as a tractor that can pull a trailer attached to it. The work machine can, for example, have a drive motor. The braking system can be designed to provide braking force by pressure. The pressure can, for example, be used to actuate respective brakes. The pressure can, for example, be provided hydraulically or pneumatically.In general, pressure for actuating brakes and alternatively or additionally for adjusting valves can be provided by a pressure change in a closed volume and alternatively or additionally by a flow velocity change in a line.

[0005] The braking system has at least a first brake, a second brake, a third brake, and a fourth brake. The first brake is assigned to a first side of a first axle of the work machine. The second brake is assigned to a second side of the first axle of the work machine, opposite the first side. The first brake and the second brake can be used, for example, to brake the first axle. In an alternative embodiment, the first and second brakes are combined in one brake, so that a (common) brake, for example arranged centrally, acts on both wheels of the first axle and brakes them. The third brake is assigned to a first side of a second axle of the work machine. The fourth brake is assigned to a second side of the second axle of the work machine, opposite the first side. The third brake and the fourth brake can be used, for example, to brake the second axle.In an alternative embodiment, the third and fourth brakes are combined into one brake, so that one brake, for example arranged centrally, acts on both wheels of the second axle and brakes them.

[0006] Generally speaking, a brake can brake the associated side of an axle, for example in order to decelerate one or more output elements located there. For example, a wheel can be arranged on each side of an axle as the output element. The first axle can be a rear axle, for example, and the second axle a front axle. At least the first axle can have a differential. Optionally, the second axle can also have a differential. For example, a left rear wheel can be braked with the first brake, a right rear wheel with the second brake, a left front wheel with the third brake, and a right front wheel with the fourth brake. A brake can, for example, have a piston, by means of which a friction element, such as a brake pad, is pressed against a friction element, such as a brake disc, which is connected in a rotationally fixed manner to the output element when the brake is applied.A brake can, for example, have a tri-stop cylinder. In the case of an alternative brake design, i.e., if only one brake is provided for the first axle and / or one brake for the second axle, the respective brake acts on both wheels of the respective axle, thus braking both wheels or the entire axle.

[0007] The braking system comprises a first brake pressure valve unit, a second brake pressure valve unit, a first pressure reservoir, a second pressure reservoir, an operating device, and a control device. A valve unit may have one or more valves that can be controlled to switch and actuate respective components connected to it. The control of valves and thus their adjustment can be achieved, for example, by means of a control pressure (i.e., pressure-controlled) or an electrical signal (i.e., electrically controlled). The valves of a valve unit can, for example, be housed together in a housing. An operating device can, for example, allow and detect a user input, such as a braking request, from a driver.The operating device can, for example, have an operating element, such as a pedal or a lever, whose actuation is detected by one or two sensors of the operating device and can be output to the control device as an electrical position signal. Actuation of the operating element can also generate a pressure that is, for example, proportional to its actuation. For example, a control pressure can be built up by pressing the pedal. The control pressure can be generated purely manually by the driver or amplified, for example, by a hydraulic booster.

[0008] The brakes can, for example, be actuated hydraulically or pneumatically. Accordingly, respective pressure reservoirs and / or valves can be designed hydraulically or pneumatically. Mixed forms are also possible, in which a valve is controlled pneumatically and the brakes are actuated hydraulically. A pressure reservoir can be a pressure accumulator. For example, a pressure reservoir can be designed as an accumulator. However, a pressure reservoir can also continuously generate pressure and thus function as a reservoir. For example, a pressure reservoir can have a compressor. For example, the braking system can have a pressure-generating device, such as a compressor or a pump. The pressure-generating device can be separate from the pressure reservoirs. Each pressure reservoir can have an associated pressure-generating device.A single pressure-generating device can also be provided, which supplies all pressure reservoirs together. In this case, for example, a multi-circuit valve can be provided, which is designed to prevent a pressure loss in one of the pressure reservoirs from also causing a pressure loss in other pressure reservoirs via the pressure-generating device. Two brake circuits can be provided by two pressure reservoirs. For example, individual components of the brake system can only be supplied with pressure from either the first pressure reservoir or the second pressure reservoir.

[0009] The control device can, for example, be designed to control respective electrically controllable valves of the braking system. The control device can generate control signals for respective valves depending on sensor signals and, alternatively or additionally, respective actuations of the operating device. The control device can, for example, have at least one microprocessor. The control device can be a vehicle ECU.

[0010] A pressure supply to the first and second brakes through the first pressure reservoir can be adjusted for their actuation by means of the first brake pressure valve unit. The first brake pressure valve unit is designed for electrical control and a redundant pressure control. For example, the first brake pressure valve unit can have one or more valves for the electrical adjustment of the pressure for actuating the first and second brakes, which valves can be adjusted by means of an electrical signal. In addition, the first brake pressure valve unit can have one or more valves for the pressure-controlled adjustment of the pressure for actuating the first and second brakes, which valves can be adjusted by means of fluid. The first pressure reservoir can be fluidically connected, for example, to the first brake and the second brake via the first brake pressure valve unit.The first brake pressure valve unit can be electrically controlled by the control device for pressure adjustment. In addition, if the electrical control fails, the first brake pressure valve unit can be pressure-controlled, for example, by the operating device.

[0011] A pressure supply to the third and fourth brakes through the second pressure reservoir can be adjusted for their actuation by means of the second brake pressure valve unit. The first brake pressure valve unit is designed for electrical control and a redundant pressure control. For example, the first brake pressure valve unit can have one or more valves for the electrical adjustment of the pressure for actuating the first and second brakes, which valves can be adjusted by means of an electrical signal. In addition, the first brake pressure valve unit can have one or more valves for the pressure-controlled adjustment of the pressure for actuating the first and second brakes, which valves can be adjusted by means of fluid. The second pressure reservoir can be fluidically connected, for example, to the third brake and the fourth brake via the second brake pressure valve unit.The second brake pressure valve unit can be electrically controlled by the control device for pressure adjustment. In addition, if the electrical control fails, the second brake pressure valve unit can be pressure-controlled, for example, by the operating device. The operating device is designed to detect an actuation position and transmit the detected actuation position to the control device. The operating device can be designed to detect the actuation position electronically and transmit the detected actuation position to the control device as an electrical signal.

[0012] The control device is designed to electrically control the first brake pressure valve unit and the second brake pressure valve unit, for example depending on the detected actuation position. For example, the control device can calculate the actuation pressures for the respective brakes depending on a characteristic map. The electrical control makes it easy to take additional sensor data and vehicle condition data into account. For example, a load can be taken into account and, alternatively or additionally, a slope gradient. Uneven brake force distribution can also be easily adjusted. For example, the control device can specify a stronger actuation for the brakes on the rear axle than for the brakes on the front axle.The control device can also calculate the deceleration of the work machine based on the detected actuation position of the control device and control the brakes accordingly. The two brake pressure valve units with separate pressure reservoirs provide two separate brake circuits, thus providing two redundant service brakes. If the braking system fails on the first or second axle, the remaining braking system on the other axle can still enable braking, thus acting as an auxiliary brake, for example.

[0013] The operating device is designed to provide a control pressure depending on the actuating position for the first brake pressure valve unit and the second brake pressure valve unit. Normally, the respective brakes are not actuated by this. The first brake pressure valve unit and the second brake pressure valve unit are designed to switch to pressure control by the operating device in the event of a failure of the electrical control by the control device. For example, the two brake pressure valve units can each have a valve that blocks pressure control as long as a corresponding control signal is sent from the control device to the brake pressure valve units. In the event of a fault, the control device can stop generating this control signal and thus pressure control can be enabled.Likewise, if the control device fails, for example, due to a short circuit, this control signal can no longer be sent, and the brake pressure valve units can switch to pressure control. When switching to pressure control, the electrical control can also be optionally disabled. With pressure control, for example, all brakes are applied equally, proportional to the actuation of the control element, and are alternatively or additionally controlled independently of other variables.

[0014] Redundant control of the brake pressure valve units protects the brake system against control unit failure. This eliminates the need for an expensive second control unit. Instead, simple mechanical redundancy can be provided through the pressure control system. This allows the brake system to provide the additional functions of an electric brake control system with minimal effort while still maintaining sufficient functional reliability with a small number of required components.

[0015] The braking system can also be designed for autonomous or remote control. The electrical control signal can then be easily used to control the braking.

[0016] According to the invention, the first brake pressure valve unit comprises a first pressure-controlled relay valve, a first inlet valve electrically controllable by the control device, a first outlet valve electrically controllable by the control device, and a first redundancy valve. The pressure supply to the first brake and the second brake via the relay valve can be electrically controllable by the control device using the first inlet valve and the first outlet valve. The first redundancy valve can be designed to enable pressure control of the first relay valve using the control pressure of the operating device in the event of a failure of the electrical control by the control device. Control redundancy for the first brake and the second brake can thus be provided using simple components.Alternatively or additionally, the second brake pressure valve unit comprises a second pressure-controlled relay valve, a second inlet valve electrically controllable by the control device, a second outlet valve electrically controllable by the control device, and a second redundancy valve. The pressure supply to the third brake and the fourth brake can be electrically controllable by the control device via the relay valve using the second inlet valve and the second outlet valve. The second redundancy valve can be configured to release pressure control of the second relay valve using the control pressure of the operating device in the event of a failure of the electrical control by the control device. Control redundancy for the third brake and the fourth brake can thus be provided using simple components.

[0017] For example, the first brake pressure valve unit and the second brake pressure valve unit can be designed identically. The brake system can then comprise a large number of identical parts. The brake pressure valve units can each have a pressure sensor configured to detect an actuation pressure of the proportional valve and transmit it electrically to the control device. This allows the control device to regulate the pressure supply, for example, by comparing a target actuation pressure and an actual actuation pressure.

[0018] The designation of the respective valves and their numbering can, for example, merely serve to identify them. For example, the second brake pressure valve unit can be free of any respective first valves. The inlet valves and the outlet valves can be identical. The first and, alternatively or additionally, the second inlet valve can be designed as a 2 / 2-way valve that is normally closed. The first and, alternatively or additionally, the second outlet valve can be designed as a 2 / 2-way valve that is normally closed. The first and, alternatively or additionally, the second redundancy valve can be designed as a 2 / 2-way valve that is normally open. The redundancy valve can also be electrically controllable by the control device. The relay valve can be designed as a proportional valve or as a two-position valve. The relay valve can allow the brakes to be applied particularly quickly.The relay valve can control the actual pressure supply to the brakes with a low control pressure. For example, the two brakes of an axle are directly connected to the assigned pressure reservoir via the assigned relay valve. A proportional valve, for example, can not only allow discrete switching positions but also allow a continuous transition of the valve opening.

[0019] In a further embodiment of the braking system, it can be provided that the braking system has a first ABS valve unit and a second ABS valve unit. An ABS valve unit can be an assembly that provides an anti-lock function on one side of an axle and thus to the output elements there. For example, if a locked left rear wheel is detected during braking, the first ABS valve unit can fully or partially open the first brake again. As soon as the left rear wheel then regains grip, the first ABS valve unit closes the first brake again. This can increase driving stability during deceleration and also reduce the distance required for braking. For example, the ABS valve unit can cause pulsed brake application.

[0020] The first ABS valve unit can be designed to modulate the pressure supply from the first brake through the first brake pressure valve unit. The second ABS valve unit can be designed to modulate the pressure supply from the second brake through the first brake pressure valve unit. The control device can be designed to control respective ABS valve units to provide a steering brake function. For example, when cornering, the control device can specifically actuate the inner of the first and second brakes and release the outer of the first and second brakes. The release can be effected, for example, via the associated ABS valve unit. This allows the steering brake function to be provided with little effort. For example, no ABS valve units are required on the second axle.

[0021] The control device can be configured to control respective ABS valve units to provide an ABS function on the associated axles. The control device can centrally control the ABS function or have associated microprocessors arranged in a housing of each ABS valve unit. A rotational speed sensor can be provided on each side of each axle or also on each wheel. The control device can be configured to control the respective ABS valve units depending on the respective detected rotational speeds, for example, to provide an ABS function. For example, the ABS valve unit is arranged in the connection between the first brake pressure valve unit and the respective associated brake. For example, the steering brake function is controlled manually by two pedals or levers of the operating device or automatically depending on a steering angle. The steering brake function can be an activatable mode.

[0022] In a further embodiment of the braking system, it can be provided that the braking system is free of additional ABS valve units. For example, the braking system may generally not have any additional ABS valve units on the second axle. This allows the braking system to be of low complexity and require little installation space.

[0023] In a further embodiment of the braking system, it can be provided that the control device is designed to control the second brake pressure valve unit to provide an ABS function on the second axle. For example, the pressure supply to the third brake and the fourth brake can be modulated jointly via the second brake pressure valve unit. As a result, if at least one of the two front wheels locks, the front axle can be released to increase driving stability. The third brake and the fourth brake can then be actuated jointly, for example in a pulsed manner, via the second brake pressure valve unit to provide a short braking distance. In this way, an ABS function can be provided at least for the second axle without additional components, which ABS function controls both brakes of the second axle jointly.For example, the braking system can have an ABS system with four sensors and three modulators, which is also known as 4S3M-ABS.

[0024] In a further embodiment of the braking system, it can be provided that the braking system has a third ABS valve unit and a fourth ABS valve unit. The third ABS valve unit can be configured to modulate the pressure supply from the third brake through the second brake pressure valve unit. The fourth ABS valve unit can be configured to modulate the pressure supply from the fourth brake through the second brake pressure valve unit. Thus, one ABS function can be provided per side of both axles. For example, the braking system can have no additional ABS valve units other than those mentioned here.

[0025] Alternatively, no ABS valve units may be provided on either axle. In this case, the control device can be configured to control the first brake pressure valve unit to provide an ABS function on the first axle and the second brake pressure valve unit to provide an ABS function on the second axle. This allows at least one axle-specific ABS function to be provided without additional components.

[0026] In a further embodiment of the braking system, the braking system can be provided with a parking brake valve unit. A pressure supply to the first and second brakes for their actuation can be electrically adjustable by the parking brake valve unit in order to provide a parking brake function. For example, a pressure supply can be interrupted so that the parking brake is activated. In the event of a pressure drop in a parking brake circuit, for example, a spring can actuate the first brake and the second brake. During driving, the pressure supply can be maintained in order to keep the parking brake function deactivated. A reverse function is also possible. The first brake and the second brake can have a separate actuation mechanism for the parking brake function, which can be pressurized regardless of whether the two brakes are actuated for deceleration while driving.For example, the first brake and the second brake can each have a Tristop cylinder, with a diaphragm part being pressurized by the first brake pressure valve unit and a spring part being pressurized by the parking brake valve unit. The braking system can have an associated pressure reservoir for the parking brake, which can be connected, for example, to the first and second brakes via the parking brake valve unit. This pressure reservoir can be separate from the first and second pressure reservoirs. This allows the parking brake to form a further, partially separate brake circuit independent of these pressure reservoirs. The parking brake can, for example, also be activated by the driver while driving. This allows the parking brake to also function as a type of auxiliary brake, for example. The control device is designed to electrically control the parking brake valve unit.For example, the parking brake can be actuated by actuating an associated control element of the control device, such as a button or a handbrake lever. The braking system is designed to keep the parking brake function deactivated by the control device in the event of a failure of the electrical control. For example, the parking brake valve unit and, alternatively or additionally, the control device are designed for this purpose. This can prevent the work machine from locking in the event of a failure of the electronics. Likewise, the control device can be designed to enable deactivation of the parking brake function in the event of a failure. For example, the parking brake function can be deactivated via the ignition and, alternatively or additionally, a further connection if the control device fails when the vehicle is parked and the parking brake function is activated.

[0027] In a further embodiment of the braking system, the parking brake valve unit can be provided with a pressure-controlled parking brake relay valve, a first parking brake valve that can be electrically controlled by the control device, and a second parking brake valve that is redundant thereto and can be electrically controlled by the control device. In addition, the parking brake valve unit can have a parking brake redundancy valve that is designed to release pressure from the parking brake relay valve in the event of a failure of the electrical control by the control device, so that the parking brake does not block the work machine in the event of a failure. The names and numbers can again be used for assignment here. The parking brake relay valve can, for example, be designed like relay valves of the brake pressure valve units. The two parking brake valves can, for example, be designed identically.The two parking brake valves can, for example, be designed as 3 / 2-way valves, which are normally in a closed or venting position. One position of the two parking brake valves can be electrically adjustable by the control device in order to actuate the parking brake relay valve. The parking brake relay valve can then, for example, be connected to the additional pressure reservoir. The two parking brake valves can, for example, each be connected to the additional pressure reservoir and the parking brake relay valve. The two parking brake valves are, for example, designed to connect a control line of the relay valve to a pressure reservoir, for example the additional pressure reservoir for the parking brake. The pressure supply to the first brake and the second brake can be electrically controllable by the control device via the parking brake relay valve using the two parking brake valves.This makes it possible to provide a fast-reacting and electrically controllable parking brake using simple means and a few components.

[0028] Alternatively or additionally, a pressure supply to the third and fourth brakes can be electrically adjustable for their actuation by the parking brake valve unit to provide the parking brake function. The pressure supply to the third brake and the fourth brake can be electrically controlled by the control device via the parking brake relay valve using the two parking brake valves.

[0029] The two parking brake valves can be connected to the relay valve via a valve, such as a check valve. For example, the valve can be designed to only allow the parking brake relay valve to be controlled by the parking brake valve with the higher or lower pressure. The braking system can have a pressure sensor. The pressure sensor can be designed to detect a pressure for pressurizing the first brake and the second brake in general and, alternatively or additionally, at least one output pressure at the parking brake relay valve. This can enable control of the parking brake and, alternatively or additionally, monitoring. The parking brake valve unit can be designed to co-actuate a service brake of a connected trailer.For example, an output line of the two parking brake valves or a control line of the parking brake relay valve can also be connected or connectable to a control line of the service brake of the connected trailer. This allows the respective brakes of the trailer to be actuated when the parking brake is applied. This means that the parking brake of the work machine is supported by the trailer. The parking brake valve unit can have a test valve to test-decouple the service brake and, alternatively or additionally, the parking brake of the connected trailer when the parking brake is applied. In its basic position, the test valve can be open. The test valve can be preloaded to the open state. When the test valve is closed, for example, the control of the trailer brakes by the parking brake valves of the work machine is suppressed.This allows the driver to test on a slope whether the brakes of the work machine alone can hold the work machine with the attached trailer.

[0030] In a further embodiment of the braking system, it can be provided that the braking system has a trailer brake valve unit. A pressure supply to respective brakes of a connected trailer can be electrically adjustable for their actuation by means of the trailer brake valve unit. In addition, the pressure supply to respective brakes of the connected trailer can be redundantly pressure-controlled for their actuation by means of the trailer brake valve unit. For example, the actuation pressure for the trailer brakes can be provided and adjustable by the parking brake valve unit. Alternatively or additionally, the operating device can be designed to also provide the actuation pressure for the trailer brake valve unit depending on the actuation position. The control device can be designed to electrically control the trailer brake valve unit.The trailer brake valve unit can be designed to switch to pressure control via the operating device in the event of a failure of the electrical control via the control device. The control of the brakes of the connected trailer can thus be protected against failure in the same way as the brakes for an axle on the tractor. Furthermore, the trailer brakes can be controlled using simple components. The trailer brake valve unit can, for example, be designed identically to the brake pressure valve units. In this case, many identical parts can be used. However, the trailer brake valve unit can also be designed differently. The trailer brake valve unit can be supplied with an additional pressure reservoir separate from the first pressure reservoir and the second pressure reservoir. In this case, operation of the brakes of the work machine can be safe in the event of a pressure loss in the trailer.

[0031] In a further embodiment of the braking system, it can be provided that the braking system has a third pressure reservoir. The pressure supply to the respective brakes of a connected trailer can be provided by the third pressure reservoir when they are actuated by means of the trailer brake valve unit. The pressure supply to the first brake and the second brake for their actuation by means of the parking brake valve unit or for keeping them open can be provided by the third pressure reservoir. The parking brake and the trailer brakes thus use the same pressure reservoir, which means that the number of pressure reservoirs can be kept low while maintaining high operational reliability. For example, the braking system has only three pressure reservoirs. The braking system can have a check valve designed to prevent a pressure loss in the first pressure reservoir when there is a pressure loss in the third pressure reservoir.For example, no pressure can be lost from the first brake and alternatively or additionally the second brake via the parking brake valve unit to the third pressure reservoir and alternatively or additionally via the trailer brake valve unit.

[0032] A second aspect relates to a work machine. The work machine has a first axle and a second axle. For example, a wheel can be arranged on each side of each axle, allowing the work machine to travel over a surface. The work machine has the braking system according to the first aspect. Respective advantages and further features can be gathered from the description of the first aspect, with embodiments of the first aspect also forming embodiments of the second aspect, and vice versa. The two axles can be braked by means of the braking system. A trailer can be coupled to the work machine.

[0033] A further aspect relates to a tractor combination comprising the work machine according to the second aspect with a trailer coupled thereto. The trailer has at least one brake, which is electrically and redundantly pressure-controlled by means of the braking system. Respective advantages and further features can be found in the description of the first aspect and the second aspect, wherein embodiments of the first and second aspects also form embodiments of the further aspect, and vice versa. Short description of the characters Fig. 1 schematically illustrates a braking system of a work machine. Fig. 2 schematically illustrates a brake pressure valve unit of the brake system according to Fig. 1. Detailed description of embodiments

[0034] Fig. 1 schematically illustrates a braking system of a work machine. The work machine has a first axle 10, which is designed as a rear axle, and a second axle 12, which is designed as a front axle. A wheel 14 is arranged on the opposite sides of each of the axles 10, 12. The braking system has a first brake 20, which is assigned to a first side of the first axle 10 and can thus brake the left rear wheel. The braking system has a second brake 22, which is assigned to a second side of the first axle 10, opposite the first side, and can thus brake the right rear wheel. The braking system has a third brake 24, which is assigned to a first side of the second axle 12 and can thus brake the left front wheel.The braking system has a fourth brake 26, which is assigned to a second side of the second axle 12, opposite the first side, and can thus brake the right front wheel. The braking system has a first pressure reservoir 28, which supplies the first brake 20 and the second brake 22 with pneumatic pressure for their actuation. The braking system has a second pressure reservoir 30, which supplies the third brake 24 and the fourth brake 26 with pneumatic pressure for their actuation. The braking system has a compressor 34, which is designed to pressurize the two pressure reservoirs 28, 30 and a third pressure reservoir 32.

[0035] The first pressure reservoir 28 is connectable to the first brake 20 and the second brake 22 via a first brake pressure valve unit 40. The second pressure reservoir 30 is connectable to the third brake 24 and the fourth brake 26 via a second brake pressure valve unit 42. The two axles 10, 12 are thus each braked by a separate brake circuit, whereby the work machine has a main brake and an auxiliary brake. The pressure supply to the respective brakes 20, 22, 24, 26 via the respective brake pressure valve unit 40, 42 can be adjusted electrically and redundantly via pressure control. The two brake pressure valve units 40, 42 can therefore be controlled both with an electrical signal and with a control pressure, thereby providing redundancy and enabling protection against the failure of a control device 50 of the braking system.

[0036] The brake system has an operating device 52. The operating device 52 has a pedal 54 as an operating element. Actuation of the pedal 54 is redundantly detected by two position sensors 56 of the operating device 52, and the detected actuation position is electrically transmitted to the control device 50. In addition, the operating device 52 is designed to provide a control pressure depending on the actuation position for the first brake pressure valve unit 40 and the second brake pressure valve unit 42. For this purpose, the operating device 52 has a valve 58 which adjusts the control pressure proportional to the actuation of the pedal 54. In the embodiment shown, the operating device 52 is supplied with pressure by the first pressure reservoir 28 in order to be able to provide the control pressure.A connection between the valve 58 and the first pressure reservoir 28 is arranged in a housing of the first brake pressure valve unit 40, which can be omitted or closed in the second brake pressure valve unit 42. In one embodiment, the operating device 52 can also be supplied alternatively or additionally from the second pressure reservoir 30. The connection to one of the two pressure reservoirs 28, 30 can also be provided outside the brake pressure valve units 40, 42. In one embodiment, the pressure generation for the control pressure can also be supported by a hydraulic booster. The control device 50 is designed to electrically control the first brake pressure valve unit 40 and the second brake pressure valve unit 42, wherein some valves of the two brake pressure valve units 40, 42 are electrically adjusted for this purpose.The first brake pressure valve unit 40 and the second brake pressure valve unit 42 are designed to switch to pressure control by the operating device 52 in the event of a failure of the electrical control by the control device 50. Then, some valves of the two brake pressure valve units 40, 42 are adjusted pneumatically instead of electrically. The valves of the two brake pressure valve units 40, 42 are described in more detail below.

[0037] Fig. Figure 2 illustrates the structure of the two brake pressure valve units 40, 42, which are identical in design. Fig.2, the brake system is only partially shown for the sake of simplicity. Therefore, the structure is described in general terms, which applies equally to the two brake pressure valve units 40, 42. Each of the two brake pressure valve units 40, 42 has a pressure-controlled relay valve 60, an inlet valve 62 electrically controllable by the control device 50, an outlet valve 64 electrically controllable by the control device 50, and a redundancy valve 66, which are housed together in a housing. Depending on its position, the relay valve 60 causes the two associated brakes 20, 22 or 24, 26 to be actuated. The inlet valve 62 and the outlet valve 64 are designed as 2 / 2-way valves that are normally closed. The inlet valve 62 and the outlet valve 64 can be adjusted by the electrical control in order to control the pressure control of the relay valve 60. The redundancy valve 66 is designed as a 2 / 2-way valve which is normally open.The control device 50 keeps the redundancy valve 66 closed during normal operation, whereby the pressure control via the operating device 52 and the control pressure provided by it do not act on the relay valve 60. If the control device 50 fails, for example due to a short circuit, the redundancy valve 66 then opens automatically, for example because it is spring-loaded towards its open position or normal position. The control pressure is then applied to the relay valve 60 and thus controls its position and thus the actuation of the two associated brakes 20, 22 or 24, 26. Each of the two brake pressure valve units 40, 42 has a pressure sensor 68, which is arranged on an output line of the relay valve 60, which is connected to the two associated brakes 20, 22 or 24, 26.The pressure sensor 68 can detect the pressure of the two associated brakes 20, 22 or 24, 26 and transmit it to the control device 50. This allows the actuation of the respective brakes 20, 22, 24, 26 to be controlled by the control device 50.

[0038] The braking system has a first ABS valve unit 70 and a second ABS valve unit 72. The first valve unit 70 is arranged in the connection from the first brake pressure valve unit 40 to the first brake 20. The second valve unit 72 is arranged in the connection from the first brake pressure valve unit 40 to the second brake 22. The first ABS valve unit 70 is designed to modulate the pressure supply from the first brake 20 through the first brake pressure valve unit 40. The second ABS valve unit 72 is designed to modulate the pressure supply from the second brake 22 through the first brake pressure valve unit 40. This provides a wheel-specific ABS function on the first axle 10. On the second axle 12, an ABS function is provided by the control device 50 and the second brake pressure valve unit 42.The control device 50 is designed to control the second brake pressure valve unit 42 to provide an ABS function on the second axle 12. The control device 50 is designed to control the two ABS valve units 70, 72 to provide the ABS function on the first axle 10 and the individual wheels 14 there. For this purpose, the braking system has a speed sensor 74 on each of the wheels 14, which detects a speed of the associated wheel 14 and transmits it to the control device 50. The control device 50 controls the ABS functions depending on the detected speeds.

[0039] The control device 50 is configured to control respective ABS valve units 70, 72 to provide a steering brake function. For example, during a right-hand bend, the first brake 20 is opened by the control device 50 via the first ABS valve unit 70, and the second brake 22 is closed by the control device 50 via the second ABS valve unit 72, while simultaneously applying pressure to the first brake 20 and the second brake 22 at the first brake pressure valve unit 40 is commanded by the control device 50. The steering brake function can thus be provided simply and with few components. In the embodiment shown, the front axle is not involved in the steering brake function.

[0040] The braking system includes a parking brake valve unit 80. The parking brake valve unit 80 is connected to the third pressure reservoir 32 for pressure supply. A pressure supply to the first brake 20 and the second brake 22 for their actuation is electrically adjustable by the parking brake valve unit 80 to provide a parking brake function. The first brake 20 and the second brake 22 each include a tri-stop cylinder. A diaphragm portion of the respective tri-stop cylinder is actuated by pressure from the first brake pressure valve unit 40. A spring portion of the respective tri-stop cylinder is pressurized via the parking brake valve unit 80 to keep the first brake 20 or the second brake 22 open. If this pressure is removed, the first brake 20 or the second brake 22 automatically adjust to their actuated position and thus prevent the parked and switched-off work machine from rolling away, regardless of a pressure supply.

[0041] The control device 50 is designed to electrically control the parking brake valve unit 80. The parking brake valve unit 80 is designed to keep the parking brake function deactivated in the event of a failure of the electrical control by the control device 50. The parking brake valve unit 80 has a pressure-controlled parking brake relay valve 82, a first parking brake valve 84 that can be electrically controlled by the control device 50, a redundant second parking brake valve 86 that can be electrically controlled by the control device 50, and a first test valve 106. The pressure supply to the first brake 20 and the second brake 22 for providing the parking brake function can be electrically controlled by the control device 50 via the parking brake relay valve 82 by means of the two parking brake valves 84, 86.A pressure sensor 88 is connected to the connection from the parking brake relay valve 82 to the first brake 20 and the second brake 22. This sensor detects a parking brake actuation pressure and transmits it to the control device 50. This allows the parking brake to be regulated and alternatively or additionally monitored. In the example shown, the state of the two brakes 20, 22 can thus be detected. The two parking brake valves 84, 86 are identical and designed as 2 / 3-way valves, which are normally in a position in which no control pressure is applied to the parking brake relay valve 82. The parking brake function is controlled via a parking brake lever 102 of the brake system, which is electrically connected to the control device 50 via a further control device 104.

[0042] A check valve 108 is arranged in a connection between the parking brake valve unit 80 and thus the two parking brake valves 84, 86 as well as the parking brake relay valve 82 and the third pressure reservoir 32. This prevents pressure loss to other parts of the brake system.

[0043] The braking system has a trailer brake valve unit 90. The trailer brake valve unit 90 is connected to the parking brake valve unit 80. When the parking brake is activated, the respective brakes of a connected trailer are also actuated. The trailer brake valve unit 90 is also supplied with pressure from the third pressure reservoir 32. The pressure supply to the respective brakes of a connected trailer through the third pressure reservoir 32 can be electrically and redundantly adjusted in a pressure-controlled manner for actuation by means of the trailer brake valve unit 90. The operating device 52 is designed to also provide the control pressure for the trailer brake valve unit 90 depending on the actuation position. The control device 50 is designed to electrically control the trailer brake valve unit 90.The trailer brake valve unit 90 is designed to switch to pressure control by the operating device 52 in the event of a failure of the electrical control by the control device 50. The trailer brake valve unit 90 has a first valve 92, which is designed as an electrically controllable 2 / 2-way valve with a normally open position. In series behind it, the trailer brake valve unit 90 has a second valve 94, which is designed as an electrically controllable 2 / 2-way valve with a normally open position. In addition, the trailer brake valve unit 90 has a third valve 96, which is designed as an electrically controllable 2 / 2-way valve with a normally closed position. These three valves 92, 94, 96 control a trailer relay valve 98, by means of which the actuation pressure for the trailer brakes can be provided.The trailer brake valve unit 90 also includes a pressure sensor 100, which detects the actuation pressure of the trailer's brakes and transmits it to the control device 50. This allows the actuation of the trailer's brakes to be controlled and monitored by the control device 50. Reference symbol 10 first axis 12 second axis 14 wheels 20 first brake 22 second brake 24 third brake 26 fourth brake 28 first pressure reservoir 30 second pressure reservoir 32 third pressure reservoir 34 Compressor 40 first brake pressure valve unit 42 second brake pressure valve unit 50 Control device 52 Operating device 54 Pedal 56 position sensors 58 Valve 60 relay valve 62 intake valve 64 exhaust valve 66 Redundancy valve 68, 88, 100 pressure sensor 70 first ABS valve unit 72 second ABS valve unit 74 Speed ​​sensor 80 Parking brake valve unit 82 Parking brake relay valve 84 first parking brake valve 86 second parking brake valve 90 Trailer brake valve unit 92 first valve trailer brake valve unit 94 second valve 96 third trailer brake valve unit 98 Trailer relay valve 102 Parking brake lever 104 additional control devices 106 Test valve 108 Check valve

Claims

[1] A braking system for a work machine, the braking system comprising at least a first brake (20), a second brake (22), a third brake (24), a fourth brake (26), a first brake pressure valve unit (40), a second brake pressure valve unit (42), a first pressure reservoir (28), a second pressure reservoir (30), an operating device (52), and a control device (50), the first brake (20) being assigned to a first side of a first axle (10) of the work machine, the second brake (22) being assigned to a second side of the first axle (10) of the work machine opposite the first side, the third brake (24) being assigned to a first side of a second axle (12) of the work machine, the fourth brake (26) being assigned to a second side of the second axle (12) of the work machine opposite the first side,wherein a pressure supply to the first brake (20) and the second brake (22) is adjustable through the first pressure reservoir (28) for actuation thereof by means of the first brake pressure valve unit (40), wherein the first brake pressure valve unit (40) is designed for electrical control and a pressure control redundant thereto, wherein a pressure supply to the third brake (24) and the fourth brake (26) is adjustable through the second pressure reservoir (30) for actuation thereof by means of the second brake pressure valve unit (42), wherein the second brake pressure valve unit (42) is designed for electrical control and a pressure control redundant thereto, wherein the operating device (52) is designed to detect an actuation position and to transmit the detected actuation position to the control device (50), wherein the operating device (52) is designed toto provide a control pressure as a function of the actuating position for the first brake pressure valve unit (40) and the second brake pressure valve unit (42), wherein the control device (50) is designed to electrically control the first brake pressure valve unit (40) and the second brake pressure valve unit (42) as a function of the transmitted actuating position, wherein the first brake pressure valve unit (40) and the second brake pressure valve unit (42) are designed to switch to the pressure control by the operating device (52) in the event of a failure of the electrical control by the control device (50), , characterized bythat the first brake pressure valve unit (40) has a first pressure-controlled relay valve (60), a first inlet valve (62) electrically controllable by the control device (50), a first outlet valve (64) electrically controllable by the control device (50), and a first redundancy valve (66), wherein the pressure supply to the first brake (20) and the second brake (22) via the first relay valve (60) is electrically controllable by the control device (50) by means of the first inlet valve (62) and the first outlet valve (64), wherein the first redundancy valve (66) is designed to release a pressure control of the first relay valve (60) by the actuating pressure of the operating device (52) in the event of a failure of the electrical control by the control device (50), and wherein the second brake pressure valve unit (42) has a second pressure-controlled relay valve (60), a first inlet valve (62) electrically controllable by the control device (50), second inlet valve (62),a second outlet valve (64) electrically controllable by the control device (50) and a second redundancy valve (66), wherein the pressure supply to the third brake (24) and the fourth brake (26) via the second relay valve (60) is electrically controllable by the control device (50) by means of the second inlet valve (62) and the second outlet valve (64), wherein the second redundancy valve (66) is designed to release pressure control of the second relay valve (60) by the control pressure of the operating device (52) in the event of failure of the electrical control by the control device (50). [2] Brake system according to claim 1, characterized byin that the braking system comprises a first ABS valve unit (70) and a second ABS valve unit (72), wherein the first ABS valve unit (70) is designed to modulate the pressure supply from the first brake (20) through the first brake pressure valve unit (40), wherein the second ABS valve unit (72) is designed to modulate the pressure supply from the second brake (22) through the first brake pressure valve unit (42), wherein the control device (50) is designed to control respective ABS valve units (70, 72) to provide a steering brake function. [3] Brake system according to claim 2, characterized by that the brake system is free of other ABS valve units (70,72). [4] Brake system according to claim 2 or 3, characterized by that the control device (50) is designed to control the second brake pressure valve unit (42) to provide an ABS function on the second axle (12). [5] Brake system according to claim 2, characterized by in that the brake system has a third ABS valve unit and a fourth ABS valve unit, wherein the third ABS valve unit is designed to modulate the pressure supply from the third brake (24) through the second brake pressure valve unit (42), wherein the fourth ABS valve unit is designed to modulate the pressure supply from the fourth brake (26) through the second brake pressure valve unit (42). [6] Brake system according to one of the preceding claims, characterized byin that the brake system has a parking brake valve unit (80), wherein a pressure supply to the first brake (20) and the second brake (22) for their actuation by the parking brake valve unit (80) is electrically adjustable in order to provide a parking brake function, wherein the control device (50) is designed to electrically control the parking brake valve unit (80), wherein the brake system is designed to keep the parking brake function deactivated in the event of a failure of the electrical control by the control device (50). [7] Brake system according to claim 6, characterized byin that the parking brake valve unit (80) has a pressure-controlled parking brake relay valve (82), a first parking brake valve (84) which can be controlled electrically by the control device (50), and a second parking brake valve (86) which is redundant thereto and can be controlled electrically by the control device (50), wherein the pressure supply to the first brake (20) and the second brake (22) via the parking brake relay valve (82) can be electrically controlled by the control device (50) by means of the two parking brake valves (84, 86). [8] Brake system according to one of the preceding claims, characterized byin that the braking system has a trailer brake valve unit (90), wherein a pressure supply to respective brakes of a connected trailer for their actuation by means of the trailer brake valve unit (90) can be adjusted electrically and redundantly in a pressure-controlled manner, wherein the operating device (52) is designed to also provide the control pressure for the trailer brake valve unit (90) as a function of the actuation position, wherein the control device (50) is designed to electrically control the trailer brake valve unit (90), wherein the trailer brake valve unit (90) is designed to switch to pressure control by the operating device (52) in the event of a failure of the electrical control by the control device (50). [9] Brake system according to claim 8 in its reference to claim 6 or 7, characterized byin that the braking system has a third pressure reservoir (32), wherein the pressure supply to respective brakes of a connected trailer when they are actuated by means of the trailer brake valve unit (90) is effected by the third pressure reservoir (32), wherein the pressure supply to the first brake (20) and the second brake (22) for their actuation by means of the parking brake valve unit (80) is effected by the third pressure reservoir (32), wherein the braking system has a check valve (108) which is designed to prevent a pressure loss of the first pressure reservoir (28) in the event of a pressure loss of the third pressure reservoir (32). [10] Work machine with a first axle (10), a second axle (12) and the braking system according to one of the preceding claims, wherein the two axles (10, 12) can be braked by means of the braking system.

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