WO2008078005A1

WO2008078005A1 - Device for the hydraulic control of a parking brake

Info

Publication number: WO2008078005A1
Application number: PCT/FR2006/002723
Authority: WO
Inventors: Christian Rollin
Original assignee: Renault Trucks
Priority date: 2006-12-13
Filing date: 2006-12-13
Publication date: 2008-07-03

Abstract

The invention relates to a device for the hydraulic control of a parking brake (1) of a motor vehicle, comprising at least one brake actuator (2) provided with elastic means for bringing brake means into an activation position. Said device also comprises a hydraulic accumulator (5) that can form a water reserve, and a solenoid valve (6) controlled by control means which authorise or interrupt a flow of pressurised liquid from the accumulator (5) to the brake actuator (2) in order to exert a force on the elastic means, or not, such that the brake means are deactivated or activated. Said device enables a range of road vehicles to be fitted with actuators comprising elastic means and to benefit from the related advantages, especially, but not exclusively, vans which do not normally comprise such actuators in as much as this type of vehicle does not have a pneumatic braking system.

Description

Hydraulic parking brake control device

The present invention relates to a parking brake control device for, in particular, a light industrial vehicle.

State of the art

Every motor vehicle is equipped with a so-called service braking system which makes it possible to slow down and possibly stop the vehicle running.

Every motor vehicle is also equipped with a so-called parking or parking braking system which makes it possible to mechanically maintain the immobility of the vehicle, even when the vehicle is parked on an inclined plane. The parking brake system generally has a stand-alone control distinct from that of the service braking system.

In the case of industrial vehicles of the heavy truck type, the braking system can be powered pneumatically. Thus, braking actuators which are linked to each wheel of the vehicle are controlled by compressed air. On this type of vehicle, certain braking actuators that act generally on the rear axles of the vehicle may incorporate springs that hold tight braking means (disk or drum); the pneumatic pressure is then used to loosen the braking means so as to allow the vehicle to taxi. This arrangement makes that when the engine of the vehicle is stopped, the vehicle is then in parking brake configuration; the engine stop of the vehicle causes a failure of the pneumatic supply so that the park brake actuators are tightened and maintain the immobility of the vehicle. This type of braking system has the advantage of immobilizing the vehicle as soon as its engine is cut and regardless of any action of the driver.

However, many vehicles, including small commercial vehicles, lack a pneumatic service braking system. These vehicles are then equipped with a hydraulic braking system; a pressurized liquid, usually oil, is transmitted from a master cylinder to brake actuators. With regard to immobilization of the parked vehicle, it can be provided a parking brake system which incorporates a mechanical control, usually cable, and which acts on an axle, usually rear. A lever or pedal allows the driver to operate the parking brake. In some cases, the mechanical control can be actuated by an electric motor, which allows, for example, to automate the activation of the parking brake. However, in such a system, the disengaging requires that the vehicle engine is en route to provide electricity, or requires to intervene directly on the mechanical control, which is generally impractical. It therefore appears that, for a vehicle having a pneumatic braking system equipped with a parking actuator which is resiliently biased towards its parking position, the activation of a park actuator can be carried out passively. ; this can occur, for example, in the event of a break in the compressed air supply of the main braking system. Contrary to this, a vehicle having a hydraulic service brake system and a mechanically controlled parking brake system requires a positive action on the mechanical parking control (either via an electric motor or by the intermediate of a manual control organ) for the parking to be carried out.

It therefore appears that some parking brake systems are not entirely satisfactory.

Presentation of the invention

An object of the invention is to provide a parking brake device for a vehicle without pneumatic equipment which is nevertheless capable of integrating one or more braking actuators with elastic means for activating braking means. Another object of the invention is to propose a parking brake device for a vehicle without pneumatic equipment which is nevertheless capable of integrating one or more braking actuators with elastic means for activating braking means and which authorizes at least one disengaging in the absence of motor action. The invention relates to a hydraulic parking brake control device of a motor vehicle comprising at least one actuator braking device having resilient means biasing braking means into the activation position; the device further comprises a hydraulic accumulator capable of constituting a hydraulic reserve, and a solenoid valve controlled by control means, allowing or interrupting a flow of pressurized liquid from the accumulator to the braking actuator to exercise or not an action. on the elastic means so that the braking means are deactivated or are activated.

The invention therefore proposes to replace the traditional mechanical cable parking brake control by a hydraulic disengagement control whose hydraulic energy necessary for unloading is stored in a hydraulic accumulator.

The fact of having hydraulic energy then makes it possible to equip a vehicle with one or more brake actuators embodying elastic means for activating the braking means (disc or drum). This is important on a safety plan since it makes it possible to equip vehicles such as, for example, light trucks with this type of actuators which have the characteristic of automatically activating the braking means when the counter-support action hydraulic stops on the elastic means. In other words, this means that, thanks to the invention, it is possible to equip a vehicle which is devoid of pneumatic equipment, with a braking actuator which is in the tight position in the absence of stress. This means that, when the engine is off, in the absence of action and, in particular, in the absence of action on the part of a vehicle operator, it can be provided that the parking brake is, by default, activated.

It should be noted another advantage that results from the presence of an accumulator for storing hydraulic energy. This arrangement makes it possible to offer a possibility of disengaging even when the engine of the vehicle is cut; indeed, to the extent that pressurized liquid is stored in the accumulator, the park brake circuit keeps a disengaging capacity because the pressurized liquid can be used to oppose the elastic means present in the actuator. This disengaging capacity is certainly limited by the capacity of the battery but may be useful for example when a vehicle is out of engine and it must nevertheless move the vehicle. In this case, the control device according to the invention allows at least a number of déparcages. In concrete terms, the accumulator may be connected to hydraulic means for pressurizing a liquid driven by an internal combustion engine of the vehicle.

Although it can be envisaged that the accumulator is connected to dedicated hydraulic pressurizing means, in a preferred embodiment, the accumulator can be connected to a hydraulic steering assistance circuit of the vehicle.

In practice, a distributor can be arranged between the hydraulic steering assistance circuit and the accumulator for diverting to the accumulator a fraction of the pressurized fluid of the hydraulic power steering circuit until the volume and or the liquid pressure reaches a predetermined value in the accumulator.

According to practical arrangements, the distributor may present:

(i) an input connected to the hydraulic power steering system of the vehicle,

(ii) an output connected to the accumulator,

(iii) an exit returning to the steering assistance hydraulic circuit,

(iv) a pilot port connected to a tapping performs the parking brake control device.

To prevent a backflow of hydraulic fluid to the hydraulic steering assistance circuit, a non-return valve can be interposed between the accumulator and the distributor.

In one embodiment, the solenoid control control means includes a control unit that can convert an action on a controller to an electrical signal.

It can be provided that the control member belongs to the group including in particular:

- a control lever, - a control pedal,

a device for monitoring the presence of an operator.

In practice, the braking means may comprise a plate acting on a disk or a jaw acting on a drum.

It may be noted that the hydraulic steering assistance circuit may have a liquid reservoir and a pump supplying a steering box. Brief description of the figures

For a good understanding, the invention is described with reference to Figures 1 and 2 ci attached schematically showing, by way of non-limiting examples, two embodiments of a parking brake control device according thereto.

Detailed description of the invention

As shown in the figures, the park brake control device comprises a parking brake actuator 2 which comprises a rod 3. This parking brake actuator may or may not be attached to a service brake actuator, which may be hydraulically controlled. The rod 3 is connected to braking means which are not shown in the drawing; it may be a wafer likely to pinch a disc, in the case of disc brake, or jaws that come to press against a drum, in the case of drum brake.

The figures represent only one actuator 2 but, in practice, two axle brake actuators 2 may be provided so that each actuator acts on a wheel.

As shown schematically in the figures, the actuator 2 has the particularity of having an elastic element such as, for example, a spring 4 which exerts its elastic action on the rod 3. Thus, when the spring 4 is not upset , the rod 3 is held in the extended position and the braking means are activated.

In the case of vehicles equipped with air-operated brakes such as, for example, trucks or buses, when the driver of the vehicle disables park braking, compressed air comes to oppose the action of the vehicle. spring 4 so that the rod 3 loosens the braking means.

However, many road vehicles such as, for example, light trucks are generally not equipped with pneumatic compressors so that this type of vehicle can not generally be equipped with actuators elastically actuated braking. As shown in FIG. 1, in one embodiment of the invention, it is provided that the actuator 2 can be fed with a liquid under pressure to control the movement of the rod 3 by opposing the action of the spring 4. For this, it is delimited in the actuator 2 a variable volume control chamber, a wall is formed by a piston which is integral in displacement of the rod 3. By introducing a fluid under pressure in said chamber control, it can solicit the rod 3 to a disengaged position, enconta elastic means.

It is expected that the actuator 2 is connected to a hydraulic accumulator 5, which constitutes a hydraulic reserve capable of supplying liquid under pressure on instantaneous calls. A solenoid valve 6 is interposed between the hydraulic accumulator 5 and the actuator 2. More precisely, the solenoid valve 6 is, for example, an electrically controlled 3/2 distributor which hydraulically connects the actuator 2 to the accumulator 5. either to a hydraulic reservoir 10. The solenoid valve 6 is electrically connected to a control unit 8 which conventionally can integrate, for example, a microprocessor with an input / output interface, a ROM memory and a RAM memory. The control unit 8 can be connected to a control member such as for example a lever 9, a pedal or a switch on which a driver can act to park the vehicle. It will be seen later that the control unit 8 can be connected to other control elements, and it is also possible for the control unit 8 to be connected to an internal communication network of the vehicle such as a network. CAN-bus ".

When the driver wants the vehicle to be unplugged, it acts on the control member (lever 9, pedal, switch) present in the vehicle. The control unit 8 sends a signal to the solenoid valve 6 so that it becomes a pass between the accumulator 5 and the actuator 2; the pressurized liquid that is stored in the accumulator 5 can then feed the control chamber of the actuator 2 and push the spring 4. Conversely, when the driver wants the vehicle to be parked, it acts on the organ control (lever 9, pedal, switch). The control unit 8 sends a signal to the solenoid valve 6 so that it interrupts the fluid communication between the accumulator 5 and the actuator 2 and, instead, to put the actuator 2 in communication with the reservoir 10 The actuator 2 is no longer supplied with liquid under pressure; the liquid previously contained in the control chamber can then to escape to the hydraulic reservoir 10, and therefore the action on the spring 4 ceases. The spring 4 then pushes the rod 3 which activates the braking means of the vehicle. The vehicle is parked. The park control could also result from a decision of the control unit 8 selected from among several possibilities of predetermined action, according to various operating parameters of the vehicle and / or the presence or absence of the driver.

A first aspect of the invention therefore relates to a control device for a parking actuator 2 comprising a hydraulic accumulator placed in series with a solenoid valve 6. The hydraulic accumulator 5 behaves like a reserve of liquid under pressure which can, depending on the position of the solenoid valve 6, supply the actuator 2 with pressurized liquid which opposes the elastic element which keeps the braking means activated. A second aspect of the invention lies in the hydraulic fluid supply under pressure of the accumulator 5. It could be envisaged to supply the battery 5 with a dedicated hydraulic pump. The addition of an additional hydraulic pump may be incompatible with a vehicle architecture that has to deal with the integration of many components or subsets. Moreover, the drive of an additional pump can be a consumer of engine power.

For this reason, in a second aspect of the invention, it may be envisaged to hydraulically connect the parking brake control device to a hydraulic steering assistance circuit. Usually, a hydraulic steering assistance circuit has a reservoir 10 of liquid and, downstream thereof, a pump 11. In the embodiment shown schematically in Figure 1, the pump 11 supplies a housing direction 12 which is itself connected by means known per se to a steering wheel. The interfacing between the parking brake control device and the hydraulic steering assistance circuit which will supply the pressurized liquid necessary for the disengagement of the braking means may be devolved on a distributor 14. The dispenser 14 may preferably be a 3/2 hydraulic distributor with hydraulic control. The distributor 14 has: (i) an input 14a connected to the output of the steering gear 12, (ii) an output 14b connected to the parking brake controller; an anti-return valve 16 is interposed, just at the exit 14b, between the accumulator and the distributor.

(iii) an outlet 14c which returns to the reservoir 10. The distributor 14 also has a pilot orifice 14d.

According to the command sent to the pilot orifice 14d, the distributor 14 can be either passing towards the parking brake control device or passing towards the reservoir 10.

In the illustrated example, the control of the distributor 14 is done hydraulically by a stitching made on the pipe connecting the accumulator 5 to the solenoid valve 6, therefore depending on the liquid pressure in the accumulator 5. The The control of the distributor 14 is as follows: when the liquid pressure in the accumulator is lower than a determined threshold pressure, the distributor 14 directs a portion of the pressurized liquid of the hydraulic steering assistance circuit towards the device parking brake control; when the pressure of the liquid in the parking brake device (ie in the accumulator) reaches the predetermined threshold, the distributor 14 then switches from its position in which the pressurized liquid is directed towards the parking brake control device to its position in which the pressurized liquid is directed back to the reservoir 10.

The operation of the parking brake control device powered by the hydraulic steering assistance circuit is as follows.

When starting the engine of the vehicle, the pump 11 which is mechanically connected to the engine, is actuated and, therefore, supplies liquid (for example oil) under pressure to the steering box 12 and the distributor 14.

The distributor 14 is in its initial state, that is to say that it is passing towards the parking brake control device, so that the liquid of the hydraulic steering assistance circuit passes through the anti-slip valve. back 16 and feeds the accumulator 5. When the pressure in the parking brake control device reaches a predetermined value, the distributor 14 switches the flow of the liquid to the output 14c. This switching is performed hydraulically by the liquid which activates the pilot orifice 14d, when the pressure exceeds the predetermined value.

The pressure value that triggers the switching of the distribution is essentially functions of the dimensional characteristics of the accumulator 5 and the actuator or actuators 2. It is important that the liquid be stored in the accumulator 5 under a pressure sufficient to oppose the action of the spring 4 of the actuator 2. The parking brake control device is then armed to be able to control the disengagement of the actuator 2.

In the case where a driver wishes to disassemble the vehicle, it acts on the control which is connected to the control unit 8; it then transmits an electrical signal to the solenoid valve 6 to make it pass to the actuator 2; the liquid under pressure is allowed to enter the actuator 2 and can then oppose the action of the spring 4; this allows the retraction of the rod 3 which loosens the braking means.

Conversely, in the case where a driver wants to park the vehicle, it acts on the control 9 which is connected to the control unit 8; this then transmits an electrical signal to the solenoid valve 6 to isolate the actuator 2 of the accumulator 5; the actuator 2 is no longer supplied with pressurized liquid, which can flow towards the reservoir 10; so that the action of the spring 4 is no longer upset and thus pushes the rod 3 which clamps the braking means. Figure 2 illustrates an alternative embodiment of the invention in which the distributor 14 is disposed between the pump 11 and the housing 12 of the hydraulic steering assistance circuit.

The invention thus provides a parking brake control device that makes it possible to use an actuator with elastic means of the spring type, which is a guarantee of safety insofar as this type of actuator activates the braking means when the The vehicle engine is shut down and the hydraulic pump 11 is thus stopped. The disengagement of this type of actuator is made possible by deflecting a portion of the pressurized liquid of the power steering circuit. The hydraulic fluid puncture performed on the steering assistance hydraulics takes place essentially at the start of the vehicle engine and thus does not interfere with the general operation of the steering.

Thus, thanks to the invention, the use of resilient spring-type actuators is not reserved for vehicles having a compressed air production system. It may also be noted that the parking brake device also offers the additional advantage of allowing disengagement when the vehicle engine is shut down. This is made possible by the accumulator 5 which keeps a quantity of liquid under pressure even when the engine of the vehicle is cut and therefore when the hydraulic pump is also stopped. This may be useful, for example, when the vehicle is experiencing engine failure; in this case, it remains possible to unpair the vehicle through the reserve of liquid under pressure that is present in the accumulator 5. This unleashing is certainly not unlimited and is conditioned by the capacity of the accumulator .

Naturally, the invention is not limited to the embodiments described by way of non-limiting examples, but on the contrary embraces all the embodiments thereof.

Thus, it is possible that the parking brake is activated by means other than the lever 9.

It can thus be envisaged that the control unit is controlled by an electrical contactor which can be, for example, by an electric switch which detects a lack of weight on a driver's seat. In the case of a household refuse collection vehicle, such an electric switch could, for example, be placed at the level of the steps where the operators are placed so that when they are busy collecting garbage and therefore, are not on the vehicle, parking braking is then activated.

The invention thus opens up the possibility of equipping actuators with elastic means with the advantages which result therefrom, a whole range of road vehicles, in particular but not exclusively light trucks, which are normally lacking in so far as this type of vehicle does not possess no pneumatic braking circuit.

Claims

Hydraulic parking brake control device (1) for a motor vehicle, characterized in that the device comprises: at least one braking actuator (2) having resilient means urging braking means in the activation position ,: a hydraulic accumulator (5) capable of constituting a hydraulic reserve, and a solenoid valve (6) controlled by control means, allowing or interrupting a flow of liquid under pressure from the accumulator (5) to the actuator (2). ) for braking to exert or not an action on the elastic means so that the braking means are deactivated or activated.

2. Device according to claim 1, characterized in that the accumulator (5) is connected to hydraulic means for pressurizing a liquid driven by an internal combustion engine of the vehicle.

3. Device according to claim 2, characterized in that the accumulator (5) is connected to a hydraulic steering assistance system of the vehicle.

4. Device according to claim 3, characterized in that a distributor (14) is arranged between the hydraulic steering assistance circuit and the accumulator (5) for diverting to the accumulator (5) a fraction of liquid under the steering assist hydraulic circuit pressure until the pressurized liquid reaches a predetermined value in the accumulator.

5. Device according to claim 4, characterized in that the distributor (14) has:

(i) an inlet (14a) connected to the hydraulic steering assistance circuit of the vehicle,

(ii) an outlet (14b) connected to the accumulator (5),

(iii) an outlet (14c) returning to the steering assistance hydraulic circuit,

(iv) a pilot orifice (14d) connected to a stitching made on the parking brake control device.

6. Device according to claim 5, characterized in that a nonreturn valve (16) is interposed between the accumulator (5) and the distributor (14).

7. Device according to one of claims 1 to 6, characterized in that the solenoid valve control means (6) comprise a control unit (8) which can convert an action on an actuator into an electrical signal.

8. Device according to claim 7, characterized in that the control member belongs to the group comprising in particular

- a control lever, - a control pedal,

a device for monitoring the presence of an operator.

9. Device according to one of claims 1 to 8, characterized in that the braking means comprises a plate acting on a disk or a jaw acting on a drum.

10. Device according to one of claims 3 to 9, characterized in that the hydraulic steering assistance circuit has a reservoir (10) of liquid and a pump (11) supplying a steering box (12).