WO1997002166A1

WO1997002166A1 - Antislip control hydraulic braking system with precharging pump

Info

Publication number: WO1997002166A1
Application number: PCT/EP1996/002877
Authority: WO
Inventors: Gottfried Dehio; Helmut Steffes; Marco Müller; Stefan A. Drumm
Original assignee: Itt Automotive Europe Gmbh
Priority date: 1995-07-05
Filing date: 1996-07-02
Publication date: 1997-01-23
Also published as: DE19523946A1; AU6516796A

Abstract

To precharge the self-priming return pump (17) of an antislip control braking system, for example at low temperatures, the invention proposes that a precharging pump (28) be situated between reservoir (22) and master cylinder (1) to deliver pressure medium into one or both of the feed connections (23, 24) to the master cylinder (1), said pressure medium reaching the suction side of the return pump (17) through the switching of an electromagnetic reversing valve (19) and an electromagnetic block valve (4). For normal braking a line fitted with an on-off valve (27) is provided between reservoir (22) and master cylinder (1). This on-off valve (27) is closed for purposes of precharging the return pump (17). The on-off valve (17) can be either an electromagnetically actuated valve or else a hydraulically actuated valve.

Description

Slip-controlled hydraulic brake system with charge pump

The present invention is based on a slip-controlled hydraulic brake system according to the preamble of claim 1. Such brake systems are known, for example, from DE 42 32 311 Cl and from DE 43 29 139 Cl. In both cases, these are brake systems which are suitable both for brake slip control and for automatic brake actuation. During a brake slip control, they operate according to the return feed principle. The two return pumps of the anti-lock control are used as pressure sources for the automatic activation of the wheel brakes. In order to support the suction of these return pumps, precharging cylinders designed in the manner of single-circuit master cylinders are provided, the trailing chambers of which are connected to a pressure outlet of the pedal-operated master cylinder. The pressure outputs of the precharge cylinders can be connected to the brake line of each brake circuit and to the suction side of its return pump by means of a control valve arrangement. When the wheel brakes are activated automatically, by switching the control valve arrangement, the pressure outputs of the return pumps are shut off against the pressure outputs of the precharge cylinders and the latter to the suction sides of the return pumps.

ORIGINAL DOCUMENTS pen connected. The precharge cylinders are both actuated by a common precharge pump, which acts on the piston surfaces of the precharge cylinder with their delivery pressure. The precharge pump is connected to the reservoir with its suction side. The pressure of the charging pump initially closes a seat valve, as in the case of a master cylinder, which blocks the connection from the pedal-operated master cylinder to the wheel brakes. By further displacement of a piston, a pressure is then built up in the brake line, which pressure is also available on the suction side of the return pump. The precharge cylinders of the two publications differ in that DE 42 32 311 Cl has two separate precharge cylinders, each with a drive pressure chamber, the drive pressure chambers being connected to the precharge pump via a common pressure line, while in DE 43 29 139 the two precharging cylinders have a common, centrally arranged drive pressure chamber which is connected to the pressure side of the precharging pump. As a result, the corresponding pistons of this precharging device move apart as soon as the precharging pump builds up pressure. Such arrangements have the advantage that there are closed static brake circuits in spite of a charge from the reservoir, ie that there is no possibility of exchanging pressure medium between the reservoir and static brake circuits except for the way through the central valves and sleeve seals of the main cylinder. The pressure side of the precharge pump is namely separated from the actual brake circuits by separating pistons. On the other hand, this requires a relatively complex design of the precharge cylinder, which drives up the price of such a brake system.

Therefore, the object of the present invention is to use a common pump for precharging the Return pumps to create a brake system according to the preamble of claim 1, in which two separate static brake circuits are retained in accordance with the statutory provisions and there is the possibility of precharging in an inexpensive manner while maintaining closed static brake circuits.

This object is achieved in conjunction with the characterizing features of claim 1. The principle of the present invention is to arrange the precharging pump above the master cylinder, so that the feature of a closed brake system is provided without further design measures. Such an arrangement of the precharge pump above the master cylinder is not limited to those brake systems in which precharging is required in both brake circuits, but can also be used for those brake systems in which only the return pump of a brake circuit has to be precharged .

If the precharging pump is functionally connected in parallel with the switching valve between the master cylinder and the container and thus a short circuit of the precharging pump is made possible as long as no pre-pressure is required, the precharging pump can convey pressure medium in a circuit without great energy loss. This has the advantage that the precharging pump can be started even before the need for a precharge and that only the switching valve has to be closed in order to provide the precharge of the precharging pump immediately. In this case, the precharge pump does not have to start up.

As long as the pressure in the wheel brakes is less than the pressure of the precharging pump, pressure medium can flow to the wheel brakes via the check valve even when the control valves are switched. The further pressure build-up takes place via the return pump. When the pressure builds up from zero, the special properties of the pumps complement each other ideally: the return pump is optimized for achieving high delivery pressures and can therefore only deliver a comparatively small volume flow. The precharge pump delivers a maximum volume flow at low pressures. This is particularly important when initiating an automatic braking process if the air clearances of the wheel brakes concerned must first be overcome.

If the return pumps are designed to be self-priming and there is no precharging, the pressure build-up in the lower pressure range takes considerably longer because of the relatively low volume delivery of these high-pressure pumps.

Another problem with self-priming pumps arises when the pressure medium has a particularly high viscosity due to low temperatures, so that a high flow resistance has to be overcome through the master cylinder, for the overcoming of which only the pressure on the liquid level of the storage container is overcome Atmospheric pressure is available.

By using a solenoid valve as a switching valve, the control of the valve can be designed as required, for example depending on the temperature, depending on the current driving situation, or the precharging pump can already be started when a possible need for an external brake is emerging.

If a hydraulically operated valve is used as the switching valve, electrical line connections can be saved. When using a hydraulic switching valve it is actuated, for example, by the delivery pressure of the precharge pump, so that no hydraulic control line is required.

A more detailed explanation of the idea of the invention will now be given with reference to the description of drawings in seven figures. It shows

1 shows a brake system according to the invention with an electromagnetically actuated switching valve, only the trailing space of the first brake circuit being precharged,

Fig. 2 is a precharging device to match

Brake system according to FIG. 1, two electromagnetically actuated switching valves being provided and precharging in both brake circuits,

3 shows a brake system according to the invention with two hydraulically operated switching valves,

Fig. 4 and Fig. 5 alternatives to the precharging device

3, wherein hydraulically actuated changeover valves are used,

6 and 7 constructive solutions for hydraulically operated switching valves according to FIGS. 3 to 5.

1 has two brake circuits I and II, which are constructed identically below the master cylinder 1. The following description of the brake circuit I thus applies analogously to the brake circuit II. The brake line 3 runs from the master cylinder 1 via an electromagnetically actuated, Isolation valve 4 open when de-energized and divided into two brake branches 5 and 6. Brake branch 5 leads via the electromagnetically actuated, de-energized inlet valve 7 to the wheel brake 8, while the brake branch 6 via an electromagnetically operated inlet valve 9, which is also open when de-energized Wheel brake 10 leads. A return line 12 or 14 leads from each of the two wheel brakes 8 and 10 to a low-pressure accumulator 15. The return lines 12 and 14 are each provided with an outlet valve 11 and 13, respectively, which are electromagnetically operated, normally closed 2/2 Directional valves are designed. The low-pressure accumulator 15 is connected to the suction side of a return pump 17 via a suction line 16, which will be referred to later as the second suction line. The first suction line 18 of the return pump 17 is connected to the brake line 3 between the master cylinder 1 and the isolation valve 4. The first suction line is provided with a changeover valve 19, which is an electromagnetically actuated, normally closed 2/2-way valve. The return pump 17 is connected with its pressure side via a pressure line 20 to the brake line 3 between the separating valve 4 on the one hand and the inlet valves 7 and 9 on the other hand.

The return pump 17 is designed to be self-priming, but has a pre-charging device above the master cylinder 1. When the master cylinder 1 is actuated by the brake pedal 21, the connection between the reservoir 22 and the wheel brakes is interrupted by the pressure chambers of the master cylinder 1. In such cases, the master cylinder pressure on the suction side of the return pump is available when the changeover valve 19 is actuated, so that preloading is not necessary. When the brake pedal 21 is not actuated, the connection between the reservoir 22 and the brake line 3 is opened through the master cylinder 1. The Master cylinder 1 has two container connections 23 and 24, which are assigned to two master cylinder connections 25 and 26 of the storage container. A switching valve 27 is inserted between the master cylinder connection 25 and the container connection 23, both of which belong to the brake circuit I, an electromagnetically operated 2/2-way valve which is opened when de-energized. The connecting line between the switching valve 27 and the container connection 23 is connected to the pressure side of a precharging pump 28. The suction side of the precharge pump 28 is connected to the reservoir 22. With this arrangement, the precharge pump 28 and the switching valve 27 are connected in parallel. This means that when the switching valve 27 is open, the pre-charge pump 28 only circulates pressure medium with little loss of power. In principle, it can run permanently and does not have to be started if necessary. If the switching valve 27 is then closed for the purpose of precharging, the delivery pressure of the precharging pump 28 is immediately available at the container connection 23 of the master cylinder. Together with the switching valve 27, the switching valve 19 and the separating valve 4 are advantageously also switched over. In this way, the delivery pressure of the precharge pump 28 passes through the master cylinder 1, the brake line 3 and the first suction line 18 directly to the suction side of the return pump 17. The check valve 4 is connected in parallel with a check valve 29, through which the precharge pressure gets directly into the wheel brakes 8 and 10, even if the isolating valve is closed for the purpose of automatic braking. This allows the brake clearance to be overcome quickly. As soon as the brakes are applied, the pressure in the wheel brakes increases to the precharge pressure. A further pressure build-up can then only take place with the aid of the return pump. A pressure recovery valve 30 is arranged parallel to the precharge pump and has an opening pressure of approximately 10 bar, at which the pressure side of the precharge pump 28 is connected to the reservoir 22. Optionally, this pressure relief valve 30 can also be replaced by a pressure limiting valve 31 parallel to the switching valve 27.

The brake system shown is preloaded via the overrun space of the first brake circuit. The first brake circuit is filled by the inflow of pressure medium, but the intermediate piston of the master cylinder is also displaced. The pre-charge pressure is also applied to the second brake circuit. If, on the other hand, one wants to fill the volume of both brake circuits, the arrangement shown in FIG. 2 can be used.

2 shows a precharging device, that is to say the part of the hydraulic circuit which is arranged above the master cylinder 1. The precharging device shown precharges both brake circuits I and II. For this reason, a first switching valve 27 is provided in the connection between the master cylinder connection 25 of the storage container 23 and the follow-up connection 23 of the master cylinder 1, while a further switch valve 31 is arranged in the connection between the master cylinder connection 26 and the follow-up connection 24 of the brake circuit II. In addition to a pressure relief valve 30, which is connected in parallel with the precharge pump 28, it is provided as a further safety device that the switching valves 27 and 31 check valves 32 and 33 1 are connected in parallel, which open from the reservoir 2 to the master cylinder 1. If the switching valves 27 and 31 should not open due to a fault, pressure medium from the reservoir 22 in the master cylinder 1 is still available for braking. In any case, it can Follow up pressure medium. Otherwise, for a brake system equipped with the precharging device according to FIG. 2, there is an analogous function to the brake system according to FIG. 1 with the difference that not only one brake circuit I but both brake circuits I and II are prefillable. The pressure medium volume delivered by the precharge pump 28 is divided via two check valves 34 and 35, which are located in the connection between the pressure side of the precharge pump and the individual container connections 23 and 24. These check valves 34 and 35 separate the two brake circuits, even when the brake pedal 21 is not actuated, during precharging by the precharge pump 28, since if there is a drop in pressure in one brake circuit, the check valves 34 and 35 of the other brake circuit overflow of pressure medium into the failed ones Brake circuit prevented. When the brake pedal 21 is actuated, the entire precharging device is decoupled from the rest of the brake system, so that two completely separate brake circuits are then present anyway.

3 is below the master cylinder

1 is constructed identically to the brake system according to FIG. 1. As in FIG. 2, both brake circuits I and II can also be prefilled with a common precharge pump 28. In contrast to FIG.

2, however, the two associated switching valves 36 and 37 can be actuated hydraulically by the delivery pressure of the precharging pump 28. These are 3/2-way valves that connect either the reservoir 22 or the pressure side of the precharge pump 28 to the master cylinder 1. In the normal case, the connection between the storage container 22 and the master cylinder 1 is opened. The preload pump 28 and the return pumps 17 and 38 are switched on to pre-charge the return pumps. The switching valves 36 and 37 are switched over by the delivery pressure of the precharge pump 28, so that check valves 39 and 40 become effective in the switching position. These correspond in their function the check valves 34 and 35 of Fig. 2, that is, that they provide for the brake circuit separation. Simultaneously with the switching of the switching valves 36 and 37, the isolating valves 4 and 41 and the switching valves 19 and 42 are switched electromagnetically, so that the pressure sides of the return pumps 17 and 38 are separated from the master cylinder 1 and the suction sides of the return pumps 17 and 38 can be supplied with the delivery pressure of the precharge pump 28. A leakage throttle 43 is provided to relieve the pressure on the switching valves 36 and 37.

The structural design of the switching valves 36 and 37 will be described later with reference to FIG. 6.

The precharging devices according to FIGS. 4 and 5 also have hydraulically actuated switching valves between the master cylinder and the storage container. 4 there is only one switching valve 43 which, in contrast to the switching valves 36 and 37 according to FIG. 3, is designed as a 2/2-way valve. Another difference is that the relief throttle according to FIG. 3 discharges pressure medium to the master cylinder and according to FIG. 4 to the reservoir. However, the function is identical to that shown in FIG. 3 with the valves 36 and 37. As shown in FIG. 4, the throttle 45, which connects the pressure side of the precharge pump 28 to the reservoir 22, can be connected to the Switch valve 43 form a structural unit.

FIG. 5 shows an arrangement similar to FIG. 3, but the method of illustration according to FIG. 4 was chosen and a throttle 46 was placed directly parallel to the switching valve 47 of the brake circuit I. The switching valve 48 of the brake circuit II does not require such a throttle, since both brake circuits are precharged by the same precharge pump 28, the pressure medium of which is already in the pressure medium via the throttle 46 container 22 can drain. In order to separate the brake circuits, two check valves 49 and 50 are also created here, as in FIG. 3. The precharging pumps 28 according to FIGS. 4 and 5 additionally have a pressure relief valve 30 as a safety device, which corresponds to that of FIG. 1.

6 shows a switching valve both as a construction drawing and as a schematic illustration, which is actuated hydraulically by the delivery pressure of the pump, but has no throttle connected in parallel. This means that such a valve can be used, for example, in the precharging device in FIG. 3 or in FIG. 5 as a switching valve for the brake circuit II. The switching valve 51 has three pressure medium connections 52, 53 and 54. The pressure medium connection 52 is connected to the pressure side of the return pump 28, the pressure medium connection 53 to the reservoir 23 and the pressure medium connection 54 to the main cylinder 1. In addition, the pressure side the pump 28 is connected to the master cylinder 1 via a check valve 55, this check valve 55 opening from the precharge pump 28 to the master cylinder 1. The switching valve 51 is conceivably simple. Eε has a sealed piston 56 which delimits a pump-side control chamber 57. On the pressure side of the precharge pump 28, the piston 56 is acted upon by a compression spring 58, which is supported in a housing-fixed manner. The piston 56 has an axial extension 59, on which a valve closing member 60 is molded.

This valve closing member 60 interacts with a valve seat 61, with which it can close the axially applied pressure medium connection 54. The pressure medium connection 53 is applied radially. The switching valve 51 is opened in the normal state by the force of the pressure spring 58, so that the pressure medium connection between the pressure medium connection 53 and the pressure medium connection 54 is free. However, if pressure is built up from the pressure side of the precharge pump 28, the piston 56 moves against the compression spring 58, so that the valve closing member 60 rests on the valve seat 61 and the connection between the pressure medium connections 53 and 54 is interrupted. If the precharge pump 28 continues to deliver pressure medium, it is supplied to the master cylinder 1 via the check valve 55 which is biased by a spring.

In contrast to the somewhat sketchy representation of FIG. 6, the circumstances in a “valve adapter” to be inserted between master cylinder 1 and storage container 22 are also taken into account in FIG. Finally, corresponding bores must also be placed in a housing. In addition to FIG. 6, FIG. 7 also has a throttle 62 arranged on the switching valve 61, as is also shown in FIG. 4 or in FIG. 5 on the switching valve 47, which is assigned to the brake circuit I. The switching valve 61 initially has a floating piston 63 on the pressure side of the precharge pump, which separates the pressure side of the precharge pump from the reservoir 22. In parallel, the throttle 62 is arranged, which virtually shorts the floating piston 63. The throttle 62 is formed by a cup-shaped metallic diaphragm, which has a small central opening. In the axial area of the pressure medium connection to the reservoir 22 there is a spherical closing member 64 which is displaced with the floating piston 63. This closing member 64 is acted upon by a compression spring 65 which is supported on the closing plug 66. This sealing plug 66 is secured with a snap ring 67 against falling out of the housing. The housing plug 66 has a valve seat 68 towards the closing member 64, through which an axial bore 69 is passed, which opens into a transverse bore 70 which is connected to a white teren transverse bore 71 is connected. This transverse bore 71 in the housing connects the switching valve 61 to the master cylinder 1 via a spring chamber of the check valve 72. The check valve 72 has a valve seat 73 fixed to the housing, through which a bore runs, which is connected to the pressure side of the precharge pump 28. It also has a housing plug seat 74 which is secured against falling out with a snap ring 75. This snap ring 75 supports the housing stopper 74 against a compression spring 76, which acts on the closing member 77 of the check valve 72 on its valve seat 73.

In the depressurized state, the check valve 77 is closed, as shown. The switching valve 61 is in its open position shown in the lower half of the axial section. When a delivery pressure is built up from the precharging pump 28, the floating piston 63 moves to the right and displaces the closing member 64 against the compression spring 65 toward the valve seat 68. As soon as the closing member 64 abuts the valve seat 68, the connection between the storage container 22 and the master cylinder 1 is interrupted. Then the delivery pressure of the precharge pump 28 acts on the closing member 77 of the check valve 72, whereby this is opened and the delivery pressure of the precharge pump 28 can propagate toward the master cylinder 1. A small leakage flow passes through the throttle point 62 and flows into the reservoir 22.

Claims

claims

Slip-controlled hydraulic brake system with a pedal-operated master cylinder (1), which is connected to at least one brake line (3) with at least one wheel brake (8, 10), with a separating valve (4) in the brake line, with a return pump (17) which is connected to the brake line (3) between the isolating valve (4) and the wheel brake (10) via a pressure line (20) and which is connected to the brake line (3) between the master cylinder (1) via a first, lockable suction line (18). and isolating valve (4) and via a second suction line (16) to a low pressure accumulator (15), which is connected to the wheel brake (8, 10) via a return line (12, 10), with an inlet valve (7, 9) in the brake line between the connection of the pressure line (20) and the wheel brake (8, 10), with an outlet valve (11, 13) in the return line (12, 14), with a reservoir (22) above the main cylinder - derε (1) is arranged and over at least a main zylinderansc ^'STATEMENTS (25,26) each with a tank port (23,24) of the master cylinder (1) is in communication, such as so¬ with a precharge pump (28), the angeεchlossen with its suction side to the storage vessel (22) is characterized in that a switching valve (27, 31, 36, 37, 43, 47, 48, 51, 62) and one are arranged in the connection between the master cylinder connection (25, 26) and the follow-up connection (23, 24) Charge pump (28) feeds pressure medium into the run-on connection (23, 24).

2. Brake system according to claim 1, characterized in that the precharging pump (28) is functionally connected in parallel with the switching valve (27, 31) and is hydraulically short-circuited when the switching valve is open.

3. Brake system according to claim 1, characterized in that when the precharge pump (28) is in operation, the first suction line (18) is opened and the isolating valve (4) is closed.

4. Brake system according to one of claims 1 to 3, characterized in that the return pump (17) is self-priming.

5. Brake system according to one of the preceding claims, characterized in that daε switching valve (27,31) is an electromagnetically actuated 2/2-way valve.

6. Brake system according to one of claims 1 to 4, characterized in that the switching valve (36,37,43,47,48,51,61) is a hydraulically operated valve.

7. Brake system according to claim 6, characterized in that the switching valve (36,37,43,47,48,51,61) is actuated by the delivery pressure of the precharging pump (28).