GB2525481A

GB2525481A - Braking device for a vehicle

Info

Publication number: GB2525481A
Application number: GB1503525.6A
Authority: GB
Inventors: Muthukumar Muthurengan
Original assignee: Daimler AG
Current assignee: Mercedes Benz Group AG
Priority date: 2015-03-03
Filing date: 2015-03-03
Publication date: 2015-10-28
Also published as: GB201503525D0

Abstract

A vehicle braking device 10 comprises a rotor (22, fig 1) connected to a propeller shaft (20, fig 1) of the vehicle in a rotationally fixed manner; a pump wheel 24 configured to pump a hydraulic fluid and a coupling device (26, fig 1) switchable between a coupling position in which the pump wheel 24 is connected to the rotor (22, fig 1), and at least one decoupling position in which the pump wheel 24 is decoupled from the rotor (22, fig 1); and a plurality of hydraulic shock absorbers 28a-c configured to be supplied with the hydraulic fluid by the pump wheel 24 in the coupling position thereby decelerating the propeller shaft (20, fig 1). The pump wheel 24 and the hydraulic shock absorbers 28a-c are preferably coupled via valve unit 38.

Description

Braking Device for a Vehicle The invention relates to a braking device for a vehicle, in particular a passenger vehicle or commercial vehicle.

Braking devices for vehicles are well-known from the general prior art. Such a conventional braking device comprises at least one brake disc or brake drum used to decelerate the vehicle. In order to decelerate the vehicle, at least one corresponding braking element such as a brake pad is moved into contact with the brake disc or brake drum so that the vehicle is decelerated by friction between the braking element and the brake disc or brake drum. Thus, excessive heat can result from said friction so that the braking device can overheat. Moreover, a particularly high number of brake pipes for guiding a brake fluid is necessary in a conventional braking device which is also referred to as a brake system. Thus, a conventional braking device has a high number of parts as well as a high weight and high costs.

Furthermore, US 5 285 872 A shows a hydraulic retarder for a vehicle, comprising a casing fixed to vehicle body members and unrotatable with respect thereto. The hydraulic retarder serves to decelerate the vehicle without moving to braking elements into contact with each other.

Moreover, US 5 351 795 A shows a vehicle transmission system, comprising a transmission having a power output shaft. The transmission system further comprises a retarder interconnected with said output shaft for selectively applying a braking torque thereto.

It is an object of the present invention to provide a braking device for a vehicle, wherein the number of parts, the costs and the weight of the braking device can be kept particularly low.

This object is solved by a braking device having the features of patent claim 1.

Advantageous embodiments with expedient developments of the invention are indicated in the other patent claims.

According to the present invention the braking device for a vehicle comprises a rotor connected to a propeller shaft of the vehicle in a rotationally fixed manner. For example, at least two wheels of the vehicle can be driven by the propeller shaft in such a way that torques can be provided by the propeller shaft, wherein the wheels can be driven by the provided torques since the wheels are connected to the propeller shaft.

The braking device further comprises a pump wheel configured to pump a hydraulic fluid of the braking system. In other words, the hydraulic fluid can be conveyed by the pump wheel. Moreover, the braking device comprises a coupling device which is switchable between at least one coupling position and at least one decoupling position. In the coupling position the pump wheel is connected to the rotor so that, in the coupling position, the pump wheel is driven via the rotor by the propeller shaft which is, for example, connected to said wheels. This means that torques can be transmitted from the wheels via the propeller shaft, the rotor, and the coupling device to the pump wheel which is driven by said torques in the coupling position. In the decoupling position the pump wheel is decoupled from the rotor so that the pump wheel cannot be driven by the rotor.

This means torques provided by the propeller shaft cannot be transmitted to the pump wheel via the coupling device.

Additionally, the braking device further comprises a plurality of hydraulic shock absorbers which are configured to be supplied with the hydraulic fluid by the pump wheel in the coupling position thereby decelerating the propeller shaft and, thus, the wheels so that the vehicle is decelerated by the braking device in the coupling position of the coupling device. In other words, in order to decelerate the vehicle, the coupling device is switched into the coupling position so that the pump wheel pumps or conveys hydraulic fluid to the shock absorbers. For example, the hydraulic fluid flows to push the shock absorbers in such a way that the propeller shaft and, thus, the wheels are decelerated via the rotor, the coupling device being in the coupling position and the pump wheel. The installation space required by the braking device according to the present invention can be kept particularly low since the braking device can be integrated in a transmission or gearbox end of the vehicle.

Moreover, the vehicle can be decelerated by means of the braking device according to the present invention without moving braking elements into contact with each other so that friction and, thus, waste heat can be avoided. Thereby, the risk of tire burst can be avoided since no heat is generated by braking elements in the vicinity of wheels of the vehicle. Moreover, the number of parts, the weight and the costs of the braking device according to the present invention can be kept particularly low in comparison with the conventional brake systems. Additionally, the vehicle can be decelerated with particularly low energy consumption. In other words, the braking device according to the present invention has a particularly low energy consumption in particular in comparison with air brake systems comprising at least one compressor for compressing air.

Since the vehicle can be decelerated without braking elements which are moved into contact with each other problems of conventional brake systems such as squealing noise, brake grabbing and other brake related issues can be avoided. This means the braking device according to the present invention can be used instead of conventional braking elements such as brake discs, brake drums and brake pads. Moreover, the braking system according to the present invention can be used instead of hydraulic retarders.

Further advantages, features, and details of the invention derive from the following description of a preferred embodiment as well as from the drawing. The features and feature combinations previously mentioned in the description as well as the features and feature combinations mentioned in the following description of the figures and/or shown in the figures alone can be employed not only in the respective indicated combination but also in any other combination or taken alone without leaving the scope of the invention.

The drawing shows in: Fig. 1 a schematic view of a braking device for a vehicle, the braking device comprising a rotor, a pump wheel, a coupling device, and a plurality of hydraulic shock absorbers configured to be pushed with hydraulic fluid by the pump wheel in a coupling position of the coupling device thereby decelerating a propeller shaft of the vehicle; and Fig. 2 a further schematic view of the braking device according to Fig. 1.

In the figures the same elements or elements having the same functions are indicated by the same reference signs.

Fig. 1 shows a braking device 10 for a vehicle such as a passenger vehicle, car, commercial vehicle or truck. The braking device 10 comprises an operating element in a form of a brake pedal 12 which is arranged in the interior 14 of the vehicle. The brake pedal 12 can be actuated and, thus, moved by the driver of the vehicle between two end positions El and E2 shown in Fig. 1. Moreover, the brake pedal 12 can be moved into several intermediate position between the end position El and E2 by the driver. By moving the brake pedal 12 from the end position El into one of said intermediate positions or the end position E2 a deceleration of the vehicle, i.e. a negative acceleration of the vehicle is effected by the driver.

The braking device 10 comprises at least one sensor 16 configured to detect the movement and, thus, respective positions of the brake pedal 12. For example, the sensor 16 is configured as a stroke sensor and provides at least one signal indicative of the detected movement or position respectively. Moreover, the braking device 10 comprises an electronic control unit ECU which is connected to the sensor 16 and configured to receive said signal.

The vehicle comprises at least one engine which is not shown in Fig. 2, the engine being configured to drive the vehicle. Moreover, the vehicle comprises a gearbox 18 which is also referred to as a transmission. Moreover, the vehicle comprises a propeller shaft 20 via which, for example, at least two wheels of the vehicle can be driven. In other words, the wheels can be driven by the engine via the propeller shaft 20 and the gearbox 18 since the propeller shaft 20 is drivable by the gearbox 18. In order to drive the vehicle the engine provides torques via an output shaft of the engine. The torques can be transmitted to the gearbox 18 and, via the gearbox 18, to the propeller shaft 2Oso that the propeller shaft 20 can be driven by the torques provided by the engine. Moreover, the propeller shaft 20 is connected to the wheels so that the propeller shaft 20 can provide torques which can be transmitted to the wheels which are driven by said torques provided by the propeller shaft 20. Furthermore, the propeller shaft 20 can be driven by the wheels since the wheels are connected to the propeller shaft 20. Thus, torques provided by the wheels can be transmitted from the wheels to the propeller shaft 20.

The braking device 10 comprises a rotor 22 which is arranged after or behind the gearbox 18. The rotor 22 is attached and, thus, connected to the propeller shaft 20 in a rotationally fixed manner so that the rotor 22 can be driven by the propeller shaft 20. In other words, torques provided by the propeller shaft 20 can be transmitted from the propeller shaft 20 to the rotor 22 so that the rotor 22 is driven by said torques provided by the propeller shaft 20.

The braking device 10 further comprises a pump wheel 24 which is also referred to as a turbine wheel, the pump wheel 24 being configured to pump a hydraulic fluid. The braking device 10 also comprises a coupling device 26 which is switchable between at least one coupling position and at least one decoupling position. For example, the coupling device 26 is configured as a clutch or a synchromesh gear assembly for engaging and disengaging the rotor 22 with the pump wheel 24. In other words, in the coupling position, the pump wheel 24 is connected to the rotor 22 so that the pump wheel 24 is driven or can be driven by the rotor 22 via the coupling device 26 being in its coupling position. In the decoupling position, the pump wheel 24 is decoupled from the rotor 22 so that the pump wheel 24 cannot be driven by the rotor 22. Thus, in the coupling position, torques provided by the propeller shaft 22 can be transmitted via the rotor 22 and the coupling device 26 to the pump wheel 24 so that the pump wheel 24 is driven by the propeller shaft and, thus, the wheels.

The braking device 10 also comprises a plurality or set of hydraulic shock absorbers 28 configured to be supplied with the hydraulic fluid by the pump wheel 24 in the coupling position thereby decelerating the propeller shaft 20 and, thus, the wheels so that the vehicle on the whole is decelerated by the braking device 10. This means the pump wheel 24 pumps or conveys the hydraulic fluid to the hydraulic shock absorbers 28 in the coupling position of the coupling device 26. Thereby, the hydraulic shock absorbers 28 are supplied with the hydraulic fluid, wherein the hydraulic fluid can flow to push at least one of the hydraulic shock absorbers 28. The hydraulic fluid flows to push at least one of the absorbers 28 in such a way that the pump wheel 24 and, thus, the rotor 22, the propeller shaft 20 and the wheels are decelerated by the hydraulic fluid and the shock absorbers 28 thereby decelerating or braking the vehicle.

As can be seen from Fig. 1, the electronic control unit ECU is connected to the shock absorbers 28, wherein the electronic control unit ECU is configured to receive the signal provided by the sensor 16. Moreover, the electronic control unit ECU is configured to control the supply of the shock absorbers 28 with the hydraulic fluid on the basis of the signal.

Fig. 2 shows the braking device 10 in more detail. As can be seen from Fig. 2, in the present case, the braking device 10 comprises three shock absorbers 28a-c which can be supplied with the pressurized hydraulic fluid by means of the pump wheel 24. For example, the hydraulic fluid is oil, in particular pressurized oil. As can be seen from Fig. 2, the turbine wheel (pump wheel 24) is arranged in a chamber 30 bounded by a casing 32, wherein the chamber 30 is fluidically connected to the shock absorbers 28a-c via at least one line 34. Thus, the hydraulic fluid pumped by the pump wheel 24 can flow from the chamber 30 through the line 34 to the shock absorbers 28a-c. The braking device 10 further comprises a pressure sensor 36 configured to detect a pressure of the hydraulic fluid in the line 34.

Moreover, the braking device 10 comprises a valve unit 38 having three valves 40a-c by means of which the supply of the shock absorbers 28a-c with the hydraulic fluid can be controlled. The electronic control unit ECU is connected to the valve unit 38 so that the electronic control unit ECU is configured to control the valve unit 38 and, thus, the valves 40a-c on the basis of the received signal indicative of the detected position of the brake pedal 12. Thus, the hydraulic shock absorbers 28a-c can be supplied with the hydraulic fluid on the basis of the position of the brake pedal 12 by means of the valve unit 38 and the electronic control unit ECU. Each of the hydraulic shock absorbers 28a-c is equipped with a pressure sensor 42a-c configured to detect a respective pressure of the hydraulic fluid. Moreover, each of the hydraulic shock absorbers 28a-c is equipped with a valve 44a-c via which the hydraulic fluid can flow away from the shock absorbers 28a-c.

Additionally, the braking device 10 comprises a large hydraulic reservoir 46 for storing the hydraulic fluid. A first pump 48 is provided, the first pump 48 being configured to pump the hydraulic fluid from the reservoir 46 to the pump wheel 24. Moreover, a second pump is provided, the second pump 50 being configured to pump or convey the hydraulic fluid from the shock absorbers 28 back to the reservoir 46 via a non-return valve 52. For this purpose the shock absorbers 28 are connected to the reservoir 46 by a line 54. A pressure sensor 57 is arranged in the line 54, the pressure sensor 57 being configured to detect a pressure of the hydraulic fluid in the line 54.

The pumps 48 and 50 form a pumping device configured to pump the hydraulic fluid from the reservoir 46 to the pump wheel 24 and from the hydraulic shock absorbers 28 back to the reservoir 46. The pump wheel 24 comprises a plurality of blades 56 and is, preferably, always surrounded by hydraulic fluid. For example, the pumps 48 and 50 are driven by the engine whenever it is required. For example, the pumps 48 and 50 are not driven constantly, but only during braking.

Preferably, the valves 48a-c and/or the valves 44a-c are electrically controllable valves such as solenoid valves which can be electrically controlled by the electronic control unit ECU. For example, the sensors 36 and 57 provide a respective pressure signal indicative of the respective detected pressure, wherein the pumps 48 and 50 are configured to receive said pressure signals. Thus, for example, the pumps 48 and 50 can be operated, in particular driven, on the basis of the received pressure signals.

When the driver of the vehicle presses, i.e. moves the brake pedal 12 out of the end position El into the end position E2 or one of the intermediate positions the coupling device 26 will be engaged, i.e. switched from the decoupling position into the coupling position so that the pump wheel 24 starts to rotate and pump the hydraulic fluid to the shock absorbers 28 (28a-c). Preferably, the coupling device 26 can be moved from the decoupling position in the coupling position with a very little travel of, for example, 5 millimeters, so that, after said travel, the pump wheel 24 is engaged with the rotor 22 via the coupling device 26 very tightly. On the basis of the position or movement of the brake pedal 12 the electronic control unit ECU decides how many of the shock absorber 28a-c are activated, i.e. which of the shock absorbers 28a-c is supplied with the hydraulic fluid.

This means the hydraulic shock absorbers 28a-c are supplied with the hydraulic fluid on the basis of the detected position of the brake pedal 12.

For example, when the driver moves the brake pedal 12 half its way towards the end position E2 the sensor 16 will output four Volts. For example, on the basis of this output the electronic control unit ECU calculates a deceleration of 0.4g. Thus, the electronic control unit ECU activates the valve 40a so that the hydraulic fluid will flow into the shock absorber 28a thereby effecting a stroke, in particular a full stroke, of the shock absorber 28a with a duration of 0.5 seconds. Moreover, the sensor 42a gives a respective feedback indicative of the detected pressure to the electronic control unit ECU. Then, the electronic control unit ECU opens the valves 40b and 44a and closes the valve 40a.

Hence, the hydraulic fluid in the first shock absorber 28a will be released through the valve 44a and hydraulic fluid cannot enter the first shock absorber 28a. Then, since the valve 40b is open, the hydraulic fluid will enter the second shock absorber 28b, so that the above mentioned process is repeated with respect to the shock absorbers 28b and 28c.

After that, for example, the hydraulic fluid can enter the first shock absorber 28a again.

The hydraulic fluid that has been used for pressing or moving the respective shock absorber 28a-c will be available in the line 54 which is a sink line. The hydraulic fluid is pumped by the second pump 50 through the line 54 back to the reservoir 46. Preferably, the set of shock absorbers 28 will be arranged circularly in a cylinder. For example, the shock absorber package depends on the gross vehicle weight (GVW) of the vehicle.

Alternatively or additionally, the selection of shock absorber also depends on the GVW.

For example, four shock absorbers can be used. Preferably, each shock absorber has a variable decelerating capacity. Moreover, it is possible that two valves are controlled by the electronic control unit ECU so as to allow two of the shock absorbers to work simultaneously while one or more other shock absorbers can work separately.

For example, each of the shock absorbers 28 conducts two strokes so that, if there are four shock absorbers, eight strokes are conducted for affecting a deceleration of, for example, 0.7g. Every shock absorber can be limited to individual deceleration, wherein one of the shock absorbers can be limited to O.2g, one of the shock absorbers can be limited to 0.lg, one of the shock absorbers can be limited to 0.3g etc. One by one, the shock absorbers 28 are used to achieve a maximum deceleration of the vehicle. For example, after four strokes a required deceleration of 0.35g is achieved. Preferably, there is one special last shock absorber with a high resistance which will be activated after the rotational speed of the respective wheel is below a predeterminable threshold value, wherein that last shock absorber will be activated so as to stop the wheel. For example, a parking braking also be set by using this one of the shock absorbers 28 by using mechanical locking mechanism.

List of reference signs braking device 12 brake pedal 14 interior 16 sensor 18 gearbox propeller shaft 22 rotor 24 pump wheel 26 coupling device 28 shock absorbers 28a-c shock absorber chamber 32 casing 34 line 36 pressure sensor 38 valve unit 40a-c valve 42a-c pressure sensor 44a-c valve 46 reservoir 48 pump pump 52 non-return valve 54 line 56 blade 57 pressure sensor El end position E2 end position ECU electronic control unit

Claims

Claims A braking device (10) for a vehicle, the braking device (10) comprising: -a rotor (22) connected to a propeller shaft (20) of the vehicle in a rotationally fixed manner; -a pump wheel (24) configured to pump a hydraulic fluid; -a coupling device (26) switchable between at least one coupling position in which the pump wheel (24) is connected to the rotor (22), and at least one decoupling position in which the pump wheel (24) is decoupled from the rotor (22); and -a plurality of hydraulic shock absorbers (28) configured to be supplied with the hydraulic fluid by the pump wheel (24) in the coupling position thereby decelerating the propeller shaft (20).
2. The braking device (10) according to claim 1, characterized in that the braking device (10) comprises at least one sensor (16) configured to detect a movement of a brake pedal (12) of the vehicle.
3. The braking device (10) according to claim 2, characterized in that the sensor (16) is configured to provide at least one signal indicative of the detected movement, wherein the braking device (10) comprises an electronic control unit (ECU) configured to receive the signal and switch the coupling device (26) between the positions on the basis of the signal.
4. The braking device (10) according to any one of the preceding claims, characterized in that the braking device (10) comprises a valve unit (38) configured to distribute the hydraulic fluid to the respective hydraulic shock absorbers (28).
5. The braking device (10) according to claims 3 and 4, characterized in that the electronic control unit (ECU) is configured to control the valve unit (38) on the basis of the signal.
6. The braking device (10) according to any one of the preceding claims, characterized in that the braking device (10) comprises a pumping device (48, 50) configured to pump the hydraulic fluid from a reservoir (46) to the pump wheel (24) and/or from the hydraulic shock absorbers (28) to the reservoir (46).
7. A vehicle comprising at least one braking device according to any one of the preceding claims.