Patent Application
20050269869
This application is based on German Patent Application 10 2004 027 508.4 filed Jun. 4, 2004, upon which priority is claimed.
1. Field of the Invention
The present invention relates to a hydraulic brake system for vehicles and to a method for influencing a brake system of this kind.
2. Description of the Prior Art
Hydraulic brake systems are known in various embodiments from the prior art. Often, such brake systems have additional regulating devices, such as ESP (electronic stability control) systems or TC (traction control) systems, for performing a driver-independent regulating intervention into the brake system in predetermined driving situations. In the known ESP systems a regulating intervention is effected, for instance such that, if it has been determined that a regulating intervention is necessary, a pump is operated in order to build up an appropriate pressure for a brake circuit and to perform appropriate regulating interventions at one wheel brake. In other words, in the known ESP systems, the pressure generation and the pressure application are done at the same instant. As a result, very stringent demands are made of the components of ESP systems, especially the drive motor, the pump elements, and the intake tract, and complicated damping provisions are made. The result is high costs for such ESP systems.
The hydraulic brake system of the invention has the advantage over the prior art of having a central pressure supply in the form of a pressure reservoir. The central pressure supply can be connected to a brake circuit and disconnected via a reservoir valve. According to the invention, pressure generation is separate from both a storage and a pressure application. According to the invention, a master cylinder is provided, which is actuatable via a brake pedal. A brake circuit connects the master cylinder to at least one wheel brake, and per wheel brake, there are preferably at least one inlet valve and one outlet valve. A pump is furthermore provided, which pumps hydraulic fluid from a return line into the central pressure reservoir. Moreover, there are one reservoir valve and one disconnection valve per brake circuit. The disconnection valve is disposed in the brake circuit between the master cylinder and one inlet valve, and the reservoir valve is located in a line that leads from the reservoir to the inlet valve.
The master cylinder preferably has a brake booster, in particular a vacuum brake booster. As a result, the central reservoir of the invention can be used exclusively for regulating interventions by the regulation system.
In another preferred feature of the invention, a connecting line is provided between the central reservoir and the master cylinder. This connecting line supplies a hydraulic brake booster. The boosting of the brake force of the driver is thus done by means of pressure from the central reservoir. This is especially advantageous, since in diesel-powered vehicles and in engines with direct gasoline injection, considerable additional expense for creating the vacuum has previously been required for a vacuum brake booster. This makes it possible also to eliminate the problem that occurs in the case of vacuum supply in the prior art because of the fact that the vacuum supply is dependent on the load state of the engine, and in direct-injection diesel and gasoline engines the vacuum cannot be generated with the aid of the engine; instead, a separate additional device must be provided. The invention therefore has major potential cost savings for the brake booster as well as especially great advantages if a brake system is combined with a regulating system, such as ESP, TCS, ABS, and so forth.
The hydraulic brake system preferably includes two brake circuits in an X-type brake circuit distribution. Alternatively, two brake circuits in an H-type brake circuit distribution can be used. The distribution of the brake circuits will be selected depending on the type of drive system (front-wheel drive, rear-wheel drive, all-wheel drive), and on the existing regulating devices.
To have additional safety in the event of a leak from an outlet valve of the brake circuit, a safety valve is preferably located in a return line of the brake circuit. The safety valve is preferably located in a return line that is common to all the brake circuits, and especially preferably the safety valve is located hydraulically upstream of the pump, which aspirates out of the return line.
Preferably, one volume-detecting device is provided for each brake circuit in the brake system; this volume-detecting device detects a volume of the hydraulic fluid flowing out via an outlet valve and also pumps it back from the reservoir into the brake circuit. As a result, the volume used during certain regulating interventions is returned again, thus counteracting sagging of the brake pedal. The volume-detecting device in particular also includes software algorithms for determining volume.
Preferably, the pressure in the central reservoir is between 100 and 250×105 Pa. Monitoring of the reservoir pressure is done by means of a pressure sensor, so that if the pressure undershoots a lower limit value, the pump is employed.
Preferably, a plurality of pumps for furnishing the reservoir pressure are connected parallel to one another. Especially preferably, the pumps are driven by a common drive mechanism. As a result, the costs can be reduced still further.
Magnet valves, which can be manufactured especially inexpensively, are preferably used as the valves.
In the method according to the invention for influencing a hydraulic brake system for a vehicle, having a central reservoir, the reservoir can be connected to and disconnected from an inlet valve of the brake circuit, via a reservoir valve. A master cylinder can be connected to an inlet valve of the brake circuit and disconnected from it via a disconnection valve. A regulating device determines a driver-independent regulating intervention into the brake system if predetermined parameters are met. If the regulating device determines that a regulating intervention must be performed, then the disconnection valve is instructed to interrupt the communication between the master cylinder and the inlet valve, and the reservoir valve is instructed to open the communication between the reservoir, in which hydraulic fluid that is under pressure is stored and the inlet valve so that a communication is established between the reservoir and the inlet valve of a brake circuit. As a result, the desired regulating intervention can be effected by means of the hydraulic fluid flowing out of the reservoir. Thus in the method of the invention, the pressure generation, which is effected by means of at least one pump, the pressure storage, and the pressure application are separate from one another.
In the method of the invention, boosting of a braking demand on the part of a driver is additionally effected by means of hydraulic fluid which is drawn from the central reservoir. As a result, a separate brake booster can be dispensed with.
The brake system of the invention is especially preferably employed in conjunction with ESP, TCS, and/or ABS systems. According to the invention, major cost reductions as well as improvements in performance and comfort can be attained for such systems. Compared with present electrohydraulic brake (EHB) systems, the invention makes a considerably improved emergency braking function possible.
The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of preferred embodiments, taken in conjunction with the drawings, in which:
As shown in
In the present exemplary embodiment, two brake circuits are provided, namely a first brake circuit 4 and a second brake circuit 5. The two brake circuits are disposed in a so-called X-type brake circuit arrangement, in which a right front wheel brake 23 (RF) and a left rear wheel brake 22 (LR) are disposed in the first brake circuit 4. A left front wheel brake 24 (LF) and a right rear wheel brake 25 (RR) are disposed in the second brake circuit 5.
In a known manner, for each wheel brake 22, 23, 24, 25, there are one inlet valve (IV) 14, 15, 16, 17 and one outlet valve (OV) 18, 19,20,21. The two brake circuits 4, 5 are united in a common return line 9, which leads to the supply container 3. A magnet valve 26 is also located in this common return line 9 and acts as a safety device, in the even that one of the outlet valves 18, 19, 20, 21 should leak.
As shown in
As can also be seen from
As also shown in
If a normal braking event is initiated by the driver via the brake pedal 2, the brake system is in the position shown in
A description now follows for if a regulating intervention, for instance in an ESP system, is performed in which individual wheel brakes are meant to be used differently. The pumps 7 by this time have already been in operation long enough that a predetermined pressure exists in the reservoir 6. The pressure is preferably from 100 to 250×105 Pa. If a regulating intervention of the ESP system is now to be performed, for instance at the first brake circuit 4, then the regulating device triggers the reservoir valve 10 and the disconnection valve 12 in such a way that the disconnection valve 12 moves to a closed state and the reservoir valve 10 changes to its opening state. As a result, the reservoir 6 communicates with the first brake circuit 4 downstream of the disconnection valve (see
The brake system of the invention thus has the advantage that pressure generation, pressure storage and pressure application can be separated from one another not only structurally but also chronologically. A common pressure supply for both brake circuits 4, 5 via the common central reservoir 6 is possible. The reservoir 6 may for instance be a gas pressure reservoir, or the like. As a result of the aforementioned separation, a sturdier and simpler construction with less likelihood of failure and producing less noise can be used for generating pressure, rather than the complicated pressure generating devices necessary in the prior art, which have to furnish the requisite operating pressure with a minimal response time.
As a result of the pressure application from the reservoir 6, a more-active pressure buildup with markedly enhanced dynamics can be done according to the invention. In other words, the response times for the regulating intervention can be shortened. Because of the use of simpler components, the brake system of the invention moreover not only has enhanced reliability but also a more-economical construction. In particular, regulating devices can be operated more reliably at extremely low temperatures, which has been problematic until now in the prior art. Another advantage of the brake system of the invention is that even if the regulating device fails, the full braking function can be maintained. To that end, the control of the pressure supply is designed to be simple and fail-safe, for instance separately from the control of the valves for the pressure modulation.
A brake system will now be described in conjunction with
The brake system in the second exemplary embodiment has essentially the same functions as in the first exemplary embodiment. Unlike the first exemplary embodiment, however, in the second exemplary embodiment a connecting line 31 is also provided between the reservoir 6 and the master cylinder 1 (see
Thus in the second exemplary embodiment, a hydraulic brake system is used which is supplied from the same reservoir 6 for the regulating intervention.
As a result, a brake booster of reduced structural size can be realized, and moreover the brake system can be used in vehicles independently of the type of engine. That is, in engines with direct diesel or gasoline injection, the additional expense for creating a vacuum for a brake booster can be dispensed with. This has major cost advantages, compared with the prior art. Otherwise, the brake system shown in
The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2004 027 508.4 | Jun 2004 | DE | national |
