GB2069610A

GB2069610A - Vacuum pump

Info

Publication number: GB2069610A
Application number: GB8104129A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1980-02-14
Filing date: 1981-02-11
Publication date: 1981-08-26
Also published as: DE3005436A1; JPS56132493A

Abstract

The pump is driven by a Diesel engine 19 and may be a rotary one of the sliding-vane type, lubricating oil being drawn from the engine's sump 20 through a line 17 and a bore 16 in the pump's housing 1 into a chamber(s) 14,15 within the pumps e.g. at the side(s) of the pump's rotor 3, whereat the pressure is approximately 50% of the vacuum pressure produced in a suction line 23 by the pump. The line 23 may be connected to a tank 24 of a vacuum booster brake system. <IMAGE>

Description

SPECIFICATION Vacuum pump The invention relates to vacuum pumps.

Vacuum pumps are necessary for diesel engine driven vehicles in which a negative pressure is used as a servo force, for example, for servo-assisted braking. Since a negative pressure is not available in the intake pipe of a diesel engine, the necessary servo vacuum must be generated by means of a separate pump. A vacuum pump for this purpose is known from German Offenlegungsschrift No.

2,653,675.

In the construction according to German Offenlegungsschrift No. 2,653,675, the pump is only indirectly driven by the internal combustion engine, namely, via the dynamo (or generator). On the one hand, this has the advantage that, because of the higher speed of rotation of the generator, the vacuum pump may be of correspondingly smaller construction; on the other hand, a separate drive to the pump is unnecessary.

A pump which has proved particularly advantageous for the above-mentioned application is one of the rotary-sliding type of construction. In order to minimise the amount of leakage and frictional stress in such a pump, it is known, from German Patent Specification No. 679,998, to mix the pumped medium, namely air, with oil acting as a sealing and lubricating means.

In known types of construction the pressurised-oil circuit of the internal combustion engine is directly connected to the inner chamber of the pump. This has the disadvantage that, in the event of this connection being ruptured, the supply of oil to the internal combustion engine is interrupted, and the internal combustion engine suffers severe damage or is even completely wrecked.

The invention resides in a vacuum pump for a vehicle provided with a diesel internal combustion engine, which vacuum pump is provided with an oil suction line connected to an oil sump of the internal combustion engine to maintain a flow of oil which serves as a sealing and lubricating means for the pump.

This has the advantage that, in the event of rupture of the connecting line between the internal combustion engine and the vaccum pump the supply of oil to the internal combuston engine is not affected. The internal combustion engine is thus in any case protected, even though the pump may be damaged.

The invention is further described by way of example, with reference to the drawings, in which: Figure 1 is a cross-section of a rotary sliding-vane pump, Figure 2 is a cross-section along the line ll-ll in Fig. 1, and Figure 3 is a flow diagram showing the connection of the vacuum pump to the internal combustion engine.

A vacuum pump has a housing 1, provided with a bore 2 in which an eccentrically jour nalled rotor 3 rotates. Four vanes 4, whose outer edges sweep along the wall of the bore 2, are inserted in the rotor 3 The rotor is also provided with four bores 9 for the purpose of weight reduction. The bore 2 has two ports 5 and 6 which are formed by cavities in part of the periphery of the bore 2. One port 5 is the larger of the two and is in communication with an inlet connection 7 controlled by a non-return valve 7'; the other port 6 is smaller and is connected to an outlet connection 8.

In the cross-sectional view of Fig. 2, the rotor 3 is shown together with two of the weight-reducing bores 9. The rotor 3 has two planar surfaces 10 and 11, which rotate in the housing 1, together with the rotor, with only a small side clearance. Each of these two planar surfaces 10 and 11 has a respective recess 12, 13, which defines a respective chamber 14, 1 5. When the pump is operating, a negative pressure corresponding to approximately half the system vacuum exists in the chambers 14, 15.

In the region of the chambers 14 and 15, the housing 1 has a bore 1 6 which forms a connection for a suction line 1 7. A throttle 1 8 and a non-return valve 25 are inserted in this suction line 1 7 close to the pump. As is evident from Fig. 3, the suction line 1 7 is connected to the diesel internal combustion engine 1 9 in the region of its oil sump 20.

The outlet connection 8 of the pump is connected via a delivery line 21 to a cylinder head 22 of the diesel internal combustion engine 19, and the inlet connection 7 is connected via a line 23 to a vacuum tank 24, whose purpose is to store the vacuum servo power. The housing 1 of the vacuum pump is attached, in a manner which is not shown, to a housing of a dynamo (or generator) from which the pump is driven. The speed of rotation of the vacuum pump corresponds to that of the generator and is consequently greater than the speed of the diesel internal combustion engine.

On the rotation of the rotor 3, the vanes 4 perform a radial movement and sweep along the inner wall of the bore 2. The sizes of the chambers defined by the bore 2, the rotor 3 and the vanes 4 are thereby varied. The pumping action of the pump is thereby produced, the pump generating in the system a negative pressure which is stored in the tank 24. The negative pressure serves as servo power for a vacuum booster brake for vehicles provided with a diesel internal combustion engine. The non-return valve 7' prevents oil from reaching the brake booster.

When the pump is in operation, a negative pressure corresponding to approximately half the system vacuum, that is, half the difference between the vacuum in the tank and atmospheric pressure, is established in the chambers 14 and 15. This partial vacuum causes oil to be drawn from the oil sump 20 via the throttle 18 and the non-return valve 25. In the vacuum pump, the oil serves to overcome sealing and lubrication problems. The excess oil then leaves the pump at the outlet 8 and is returned via the delivery line 21 to the internal combustion engine 1 9. There it enters the cylinder head 22 and is returned via an inner chamber of the internal combustion engine to the oil sump 20.

If, in this system. the suction line 1 7 should be ruptured, the vacuum pump operates without lubrication and is soon wrecked. In such an event, however, the pressurised-oil supply to the internal combustion engine remains intact, so that the internal combustion engine is protected against damage.

The non-return valve 25 prevents the reverse flow of oil from the suction line 1 7 to the oil sump 20 after the pump is switched off, and ensures that the necessary oil is available when the pump is started up.

Claims

1. A vacuum pump for a vehicle provided with a diesel internal combustion engine, which vacuum pump is provided with an oil suction line connected to an oil sump of the internal combustion engine to maintain a flow of oil which serves as a sealing and lubricating means for the pump.

2. A vacuum pump according to claim 1, in which a non-return valve which closes in a direction towards the oil sump is contained in the suction line near to the vacuum pump.

3. A vacuum pump according to claim 1 or 2, in which the suction line contains a throttle.

4. A vacuum pump according to claim 1, 2 or 3, in which the suction line is connected to a chamber of the pump.

5. A vacuum pump according to claim 4, which has a rotor which serves to define the pump working chamber, and in which the suction line is connected to a further chamber of the pump defined by the rotor, in which further chamber there prevails approximately half the negative pressure generated by the pump in operation.

6. A vacuum pump according to any of claims 1 to 5, in which an outlet or discharge connection of the vacuum pump is connected to an inner chamber of the engine.

7. A vacuum pump according to claim 6, in which the outlet or discharge connection is connected via the cylinder head of the internal combustion engine to the oil pump.

8. A vacuum pump according to any of claims ] to 7, in which a non-return valve which opens in a direction towards the pump, is inserted at the inlet or suction connection of the vacuum pump.

9. A vacuum pump constructed and adapted to operate substantially as herein described with reference to and as illustrated in the drawings.