DE102017222585B3 - Electronically slip-controllable vehicle brake system - Google Patents

Abstract

The invention relates to an electronic slip-controllable vehicle brake system (250) equipped with a piston pump (100). Piston pumps (100) have a pump piston (106) which can be driven for a stroke movement and delimits a working space (148) of the piston pump (100), this working space ( 148) is changed as a function of the direction of movement of the pump piston (106). A supply of the working chamber (148) with pressure medium is electronically controllable. An electronically controllable pressure medium supply allows influencing of the control times and of the flow cross section and thus a metering of the piston pump (100). inflowing volume of pressure medium. The pressure medium supply of a piston pump (100) is thereby adaptable to the current case of need.

Description

The invention relates to an electronically slip-controllable vehicle brake system according to the features of the preamble of claim 1.

A piston pump of an electronically slip-controllable vehicle brake system is known, for example from the DE 10 2014 221 097 A1 ,

This known piston pump has a pump piston, which is drivable by an external drive element to a lifting movement and slidably received in a pump cylinder. This pump cylinder defines, together with the pump piston, a working chamber which, depending on the direction of movement of the pump piston, cyclically reduces or increases its volume. The pump piston moves back and forth between two reversal positions and changes its direction of movement in the reversal positions. Furthermore, the piston pump has a pump inlet valve which controls an inflow of pressure medium from an inlet of the piston pump into the working space. If the volume of the working chamber narrows due to the corresponding direction of movement of the piston, the pump inlet valve is usually closed, so that the forwardly advancing piston compresses the pressure medium located in the working space.
In the reverse direction of movement of the pump piston, so when the volume of the working chamber increases, the pump inlet valve is open, so that due to the negative pressure generated by the outwardly aspirated pump piston new pressure fluid flows from the inlet into this working space.

Such piston pump are widely used in electronic slip-controllable vehicle brake systems to build a brake pressure in the brake circuits such vehicle brake systems and thus to apply the connected wheel brakes accordingly. The inlet valves of these piston pumps have hitherto been designed as mechanical, pressure-controlled check valves. Accordingly, they have a valve closing member actuated by the pressure in the working space against the restoring force of an inlet valve spring, which valve controls a valve seat formed at the transition into the working space.

Modern vehicle brake systems are increasingly perceiving comfort and safety functions and must therefore be able to perform different braking operations without the involvement of the driver. In particular, in safety functions, such as pedestrian protection, it is necessary that the piston pumps in the short term promote a relatively large volume of pressure medium under a relatively low pressure to operate the wheel brakes, while in comfort functions, such as the distance control relative
high brake pressures are to be provided at a relatively low pressure medium flow rate.

Physically limited by hydromechanically actuated pump inlet valves, this range of requirements is limited by the fact that neither the flow cross sections nor the timing of such pump inlet valves are sufficiently adaptable to the requirements of the respective braking processes. The explained requirements are contrary to the fact that known pump inlet valves are usually arranged space-saving manner on the pump piston and therefore limited in their mechanical dimensions. With the arrangement on the pump piston, the pump inlet valves follow the piston movement and are therefore also exposed to the occurring acceleration and deceleration forces, which in turn influences the self-adjusting timing. Finally, the pump inlet valves have a throttling effect due to their space limitation on the pressure medium flow, which may have a disadvantageous effect, especially at low pressure medium temperatures.

In the from the DE 197 00 806 B4 Known prior art are in the pressure medium connection of a master cylinder to a suction port of a piston pump, a switching valve for controlling the pressure medium connection and a piston pump upstream pump inlet valve (check valve of the piston pump) arranged. The pump inlet valve is designed as a hydromechanically controlled valve and is therefore not as claimed, electronically controlled.

After the brake circuit 1 the DE 10 2016 206 758 A1 is in the pressure fluid connections from the master cylinder to a suction port of the piston pump only one electronically controllable valve (high-pressure switching valve) is present. It therefore lacks a series connection of a switching valve and a pump inlet valve.

The same applies mutatis mutandis to the braking system after the single figure of DE 10 2014 222 573 A1 or after the 1 to 3 the DE 10 2014 200 670 A1 to.

At the piston pump after the DE 10 2014 221 097 A1 the pump inlet valve is again a hydromechanically actuated valve and not an electronically controllable valve.

The object of the present invention is to specify an electronically slip-controllable vehicle brake system in which a filling of the working space of the piston pump with pressure medium can be better controlled over time and the filling quantity can be made more precisely metered than in the known prior art.

The pressure medium delivery can thus be more precisely adapted to the requirements of the respective braking processes. Furthermore, the invention enables a simpler structural design for a piston pump and thus contributes to a saving of component costs and space.
Furthermore, the invention improves the operating noise of a piston pump.

Further advantages or advantageous developments of the invention will become apparent from the dependent claims and / or from the following description.

Electronically controllable solenoid valves, as well as piezoelectric valves for pressure control in slip-controlled vehicle brake systems have already proven themselves many times. The dynamics and the precision of the switching cycles that can be carried out with them are also suitable for controlling the pressure medium supply of a piston pump.

Electronically controllable pump inlet valves are particularly effective if the pressure medium connection controlled by them opens directly into the working chamber of the piston pump downstream of this pump inlet valve. By direct confluence it is understood in this context that the pressure medium connection is e.g. no branching cross connections and / or points at which the pressure medium flow is deflected. In fact, branching or deflection points act as flow resistances which can impair an exact control of the control times of the pump inlet valves and / or an exact metering of the supply of a piston pump with pressure medium via a control of the flow cross section of the pump inlet valves.

Electronically controllable pump inlet valves, which are arranged separately from the pump piston, offer the advantage that the pump piston is structurally simpler and more compact. As mentioned, this has beneficial effects on the cost and dimensions of a piston pump. In addition, larger flow cross sections can be displayed.

Electronically slip-controllable vehicle brake systems are usually equipped with so-called high-pressure switching valves in order to control a pressure medium connection between a driver-operable master cylinder and a suction side of a piston pump. This occurs, for example, when the pressure fluid released from the wheel brakes in the context of a brake pressure control should not be sufficient to convert a braking request specified by the driver into a corresponding brake pressure in a subsequent braking operation. It is proposed that in the future such a high-pressure switching valve takes over the function of the pump inlet valve and controls the pressure medium supply of the piston pump as needed. This has the advantage that no additional electronically controllable pump inlet valves must be used, but that in any case present in a slip-controllable vehicle brake system, this function can be transferred. Electronically slip-controllable vehicle brake systems according to the invention design can therefore be equipped with piston pumps, which manage without a pump inlet valve.

• 1 schematisch vereinfacht eine Kolbenpumpe im Längsschnitt und in
• 2 ein Hydraulikschaltplan einer elektronisch schlupfregelbaren Fahrzeugbremsanlage in zwei Ausführungsvarianten.

Embodiments of the invention are explained in detail in the following description and illustrated in the drawing. Shown is in

• 1 schematically simplifies a piston pump in longitudinal section and in
• 2 a hydraulic circuit diagram of an electronic slip-controllable vehicle brake system in two variants.

In the 1 shown piston pump 100 is in a stepped from outside to inside in their inner diameter pump intake 102 a pump housing 104 added. It includes a pump piston 106 , one of the pump intake 102 protruding front end of a drive element 108 is mechanically operated. In this drive element 108 it is, for example, one at the end face of the pump piston 106 adjacent and driven to a rotational movement cam or eccentric. The pump piston 106 performs a reciprocating stroke movement determined by the cam shape or eccentric shape and is in one of the pump housing 104 trained cylinder section 110 slidably received. A pump piston 106 enclosing sealing ring 112 with adjacently arranged support ring 114 seals a guide gap between the cylinder portion 110 of the pump housing 104 and the circumference of the pump piston 106 from.

An actuation of the pump piston 106 through the drive element 108 takes place against the force of a piston return spring 116 which is inside a filter sleeve 118 is arranged and with one of its two ends to a valve seat body 120 a pump outlet valve 122 and with her opposite second end on the facing end face of the pump piston 106 supported. The valve seat body 120 covers the open end of the filter sleeve 118 and serves this filter sleeve 118 at the same time as an axial support. Furthermore, the valve seat body 120 provided with a central passage opening. That forms on one of the pump piston 106 opposite side a valve seat 124 from that of a spherical valve closing member 126 is controlled. The latter is from a valve spring 128 against the valve seat 124 pressed. The valve spring 128 is to inside a receiving opening of a plug 130 taken, which the pump intake 102 of the pump housing 104 closes to the outside. The stopper 130 is with the pump housing 104 caulked and has circumferentially on a circumferential shoulder. With its to the inside of the pump intake 102 facing front surface lies the plug 130 flush with the valve seat body 120 Accordingly, and contributes to the stationary fixation of this valve seat body 120 inside the pump intake 102 at.

A pump outlet 132 in the form of a groove-shaped recess is on the valve seat body 120 facing front surface of the plug 130 intended. The pump outlet 132 thus runs between the valve seat body 120 and the stopper 130 transverse to a longitudinal axis of the pump intake 102 and opens on the circumference into a pressure medium discharging region of the pump intake 102 on.

At the height of the filter sleeve 118 is in the pump housing 104 a feed 134 available through the piston pump 100 Pressure medium is supplied. This feed 134 meets as an example at right angles to the peripheral surface of the filter sleeve 118 ,
He is from a pump inlet valve 136 controlled, which is exemplified as electronically controllable, normally closed, 2/2-way switching valve is executed. Accordingly, the pump inlet valve 136 by electronic control of an electronic control unit 138 from a normally closed basic position 140 in a passage position 142 switchable and returns after a withdrawal of this electronic control from the passage position 142 in its locked or home position 140 back. 1 shows the pump inlet valve 136 in the electronically controlled state, ie in its passage position 142 , As an electronically controllable actuator 144 for switching the inlet control valve 136 For example, a magnetic coil or a piezoelectric actuator can be used; to reset the pump inlet valve 136 is an elastic return element 146 , for example a spiral spring,
intended.

It is assumed that the filter sleeve 118 along its outer periphery is provided with apertures which are spanned by a filter fabric (not visible) through which pressure medium into the interior of the filter sleeve 118 can occur. The interior of the filter sleeve 118 is as mentioned by one of the end faces of the pump piston 106 limited and forms a working space 148 the piston pump 100 out.

This workroom 148 changed depending on the direction of movement of the pump piston 106 his volume. Moves the pump piston 106 for example, in the interior of the filter sleeve 118 on, takes the pump inlet valve 136 the blocking position, which increases the volume of the working space 148 the piston pump 100 successively reduced. Accordingly, the pressure on the workspace increases 148 contained pressure medium. Once the on the valve closing member 126 the pump outlet valve 122 acting compressive force is greater than that of the valve spring 128 applied closing force, lifts the valve closing member 126 from the valve seat 124 off, the pump outlet valve 122 opens and pressure fluid flows out of the workspace 148 to the pump outlet 132 down.

In the opposite direction of movement of the pump piston 106 So if the pump piston 106 from the filter sleeve 118 extends, is the electronically controllable pump inlet valve 136 from the control unit 138 energized and in his Durchlassstellung 142 switched so that pressure fluid from the inlet 134 through the filter sleeve 118 through into the workroom 148 the piston pump 100 can flow in. This pressure medium entry is made by closing the pump inlet valve 136 finished as soon as the pump piston 106 has reached its outer reversal point and reverses its direction of movement. The explained electronic control of the pump inlet valve 136 is from the electronic control unit 138 depending on the prevailing braking situation. This means that from the control unit 138 the time can be set at which an electronic control of the pump inlet valve 136 begins or ends. By appropriate timing of the drive signal can also be the opening duration of the pump inlet valve 136 be varied over a given period of time. Alternatively, instead of a switching valve, a proportional valve as a pump inlet valve 136 used, so a valve whose opening cross-section is variably adjustable by appropriate electronic control, can supply the piston pump 100 be further optimized with pressure medium and adapted to the brake case.

The 2 shows the structure of an electronic slip-controllable vehicle brake system 250 based a circuit diagram. Accordingly, this vehicle brake system 250 with a master cylinder 252 equipped by a driver via a with a brake booster 254 coupled brake pedal 256 is operated by muscle power. To the master cylinder 252 are two separate brake circuits 258 . 260 connected.

The brake circuits 258 and 260 are constructed differently to illustrate two embodiments of the invention, while in vehicle braking systems in the field, the brake circuits are usually constructed identical to each other.

Each of the brake circuits 258 . 260 to 2 supplies example two wheel brakes 262 with pressure medium under brake pressure. This brake pressure is from each one pressure generator 264 provided and each one, a wheel brake 262 assigned pressure modulation device adapted to the prevailing at the respective wheel slip conditions. This pressure modulation device comprises per wheel brake 262 a pressure inlet valve 266 which is upstream of the respective wheel brake 262 in the brake circuit 258 . 260 is arranged and a pressure relief valve 268 located downstream of the associated wheel brake 262 in the respective brake circuit 258 . 260 located. The pressure outlet valve 268 controls the cross section of a return 269 , by the pressure medium if necessary from the wheel brake 262 discharged and a low-pressure accumulator 270 is supplied. This low pressure accumulator 270 is with a suction connection 272 of the pressure generator 264 connected. Its pressure connection 274 opens upstream of the pressure inlet valve 266 in the brake circuit 258 . 260 one, being between the master cylinder 252 and the mouth of the pressure port 274 of the pressure generator 264 a separating valve 276 is arranged to a pressure medium connection from the master cylinder 252 to the wheel brakes 262 if necessary, interrupt. In addition, in a pressure medium connection 278 from the master cylinder 252 to the suction connection 272 of the pressure generator 264 a switching valve 280 arranged to also control this pressure medium connection.

In the brake circuit 258 is the pressure generator 264 According to the invention, an electronically controllable pump inlet valve 136 upstream. The latter is from the illustrated basic position 140 in the passage position 142 switchable. In the basic position 140 takes the pump inlet valve 136 the blocking position while it is in the passage position 142 the pressure generator 264 with the master cylinder 252 and the return 269 contacted. Pos. 144 designates the actuator of the pump inlet valve 136 , which against the force of the elastic return element 146 acts.

The two brake circuits after 2 differ insofar as that in the brake circuit shown on the right 260 no discrete electrically controlled pump inlet valve 136 is available. In this brake circuit 260 the control of the pressure medium supply of the pressure generator takes place 264 through the switching valve 280 , which in the pressure medium connection 278 from the master cylinder 252 to the suction connection 272 of the pressure generator 264 is arranged. This switching valve 280 is identical to the pump inlet valve 136 the brake circuit 258 is formed and accordingly with the aid of an electronically controllable actuator against the force of a return element of a blocking position in a passage position switchable. By electronic adjustment of the clock frequency in the control, the switching valve 280 be put in the position, the pressure medium supply of the pressure generator 264 to control electronically. The suction connection 272 of the pressure generator 264 is to directly with the switching valve 280 connected, ie between switching valve 280 and pressure generator 264 There is no separate inlet valve.

An electronic controllability of the pump inlet valve 136 in the brake circuit 258 or the switching valve 280 in the brake circuit 260 allows a very precise adjustment of the timing and the flow cross-section at the inlet of the pressure generator 264 to the respective present brake case. For example, if there is a brake case in which in a short time much volume of pressure fluid at one of the wheel brakes 262 the brake circuit 258 . 260 is required, it is based on an adapted thereto electronic control of the pump inlet valve 136 in brake circuit 258 or the switching valve 280 in brake circuit 260 at the earliest possible time, that is, when the pump piston 106 is located near or in its outer reversal point, as large a flow cross-section provided, so over the largest possible stroke range of the pump piston 106 from the piston pump 100 Pressure medium is recoverable.

If, however, a high pressure in one of the wheel brakes 262 needed, is only at a relatively late time, so when the pump piston 106 already approaching its inner reversal point, the pump inlet valve 136 in brake circuit 258 or the switching valve 280 in brake circuit 260 by a corresponding electronic control of the electronic control unit 138 opened and only releases a relatively small flow area.

Overall, the invention thus enables the Druckmitteversorgung a pressure generator 264 better adapted to the respective needs. This can be the pressure generator 264 Required drive power more effective control and unnecessary load on the pressurized components of the vehicle brake system 250 to decrease. Furthermore, this can be done by the pressure generator 264 reduce operating noise caused.

Claims (5)

An electronically slip-controllable vehicle brake system having an actuatable master cylinder (252) and a brake circuit (258) connected to the master brake cylinder (252) with a drivable piston pump (100), the piston pump (100) being provided with a pump piston (106) drivable for a stroke movement with a working space (148), which changes its volume depending on the direction of movement of the pump piston (106) and wherein a supply of the working space (148) with pressure medium is electronically controllable, characterized in that in a pressure fluid connection from the master cylinder (252) to a suction port the piston pump (100) a switching valve (280) for controlling the pressure medium connection and a piston pump (100) upstream of electronically controllable pump inlet valve (136) are arranged. Electronic slip-controllable vehicle brake system Claim 1 , characterized in that the pump inlet valve (136) is a solenoid valve, wherein a valve closing member is actuated by an actuator and having an electronically controllable solenoid. Electronic slip-controllable vehicle brake system Claim 1 , characterized in that the pump inlet valve (136) is a piezoelectric valve, wherein a valve closing member is actuated by an actuator and having an electronically controllable piezoelectric actuator. Electronically slip-controllable vehicle brake system according to one of Claims 1 . 2 or 3 , characterized in that the pressure medium connection downstream of the pump inlet valve (136) opens directly into the working space (148) of the piston pump (100). Electronically slip-controllable vehicle brake system according to one of Claims 1 to 4 , characterized in that the pump inlet valve (136) is arranged separately from the pump piston (106).

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