Drive unit with an engine and a retarder

Details Drive unit with an engine and a retarder Drive unit with an engine and a retarder

1997-04-24

2001-05-01

Nelli, Raymond A. (Department: 3402)

Internal-combustion engines

Engine speed regulator

Responsive to deceleration mode

Reexamination Certificate

active

06223718

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to drive units and in particular to such units having an engine, a retarder and a pump.
2. Description of Related Technology
Drive units having an engine, a retarder and a pump are known in the art. For example, such a drive unit is disclosed in DE 37 13 580 which discloses a retarder for circulating the coolant of a vehicle cooling unit which is disposed in the coolant circulation, both in normal traction operation as well as during retarder operation (i.e., a “water-pump retarder”). The retarder disclosed in DE 37 13 580 is controlled by a suitable valve arrangement in such a way that in case of need, the retarder also can perform braking work. During the “pumping” operation, the power uptake should be as low as possible, while the power uptake should be as high as possible during the retarder “braking” operation. The technical requirements are thus very contradictory. As a result, the “pumping” operation does not operate effectively enough as too much power is taken up (i.e., absorbed).
On the other hand, if the two functions of “pumping” and “braking” are separated structurally, by providing a separate pump in addition to a retarder, then, although the retarder and the pump can be designed in such a way that the functions will be fulfilled optimally, such a system has a high space requirement. This is disadvantageous because the space in vehicles is very limited, especially at the particular location where the pump and the retarder would need to be placed.
For the sake of completeness, the following publications also are disclosed herein:
The retarder disclosed in U.S. Pat. No. 3,720,372 is integrated with the driving engine, permanently attached to the crankshaft, and coolant of the cooling unit continuously flows through the retarder. The rotor of the retarder serves as a circulating pump instead of a special coolant pump. The purpose of this arrangement is to heat the coolant by the retarder in order to heat the passenger compartment. A control system disposed on the retarder serves the purpose of passing or distributing the coolant as a function of its temperature in a bypass line through the radiator.
A retarder also is disclosed in DE 33 01 560 (corresponds to U.S. Pat. No. 4,538,553) which is connected through a switchable coupling to the crankshaft of a driving engine and to the driving wheels of a vehicle. However, the task of the retarder is not the uptake and conversion of the high kinetic braking energy of the vehicle into heat. The retarder is operated exclusively as a heater, whereby the heating output is controlled with consideration of the available drive power. The coolant of the engine also is the operating fluid of the retarder.
A retarder disclosed in DE-AS 1 946 167 (corresponds to U.S. Pat. No. 3,650,358) is connected directly to the crankshaft of an internal combustion engine, the coolant of which also serves as an operating fluid for the retarder. An advantage of this mode of operation is that the heat produced evolves directly in the coolant introduced to the radiator and the heat exchanger between two fluids can be omitted.
EP 707 140 discloses a drive unit with an engine and a hydrodynamic retarder. In order to transport the coolant, a pump impeller is provided which is disposed axially to the rotor paddle wheel of the retarder.
In the retarders known in the art, a certain power loss occurs during non-braking operation. Namely, during non-braking operation, the retarder is filled with air in addition to a residue of the working medium of the retarder. This leads to ventilation losses.
SUMMARY OF THE INVENTION
It is an object of the invention to overcome one or more of the problems described above. It also is an object of the invention to provide a drive unit of the type described above in which ventilation losses are minimized and wherein the retarder operates optimally in the braking operation, that is, the braking behavior is constant and reproducible.
A drive unit according to the invention includes a hydrodynamic retarder having a rotor paddle wheel, a stator paddle wheel, and a housing surrounding the rotor and stator wheels. The unit includes a coolant cycle system for an internal combustion engine, the coolant for this coolant cycle also being a working medium of the retarder. The drive unit further includes a working medium container for the coolant which is connected to the coolant cycle system. A connecting pipe is disposed between the working medium container and a hydrodynamic center of the retarder. A valve is disposed in the connecting pipe.
Other objects and advantages of the invention will be apparent to those skilled in the art from the following detailed description taken in conjunction with the drawing and the appended claims.


REFERENCES:
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patent: 33 01 560 (1984-04-01), None
patent: 37 13 580 (1988-11-01), None
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patent: 1007421 (1965-10-01), None
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European Search Report of counterpart European Application 97 10 4907.7, Applicant: Voith Turbo GmbH & Co. KG.
Abstract of German Publication No. 2 150 115 obtained from Derwent World Patent Index.
Abstract of French Publication No. 2 383 053 obtained from Derwent World Patent Index.
Abstract of European Publication No. 0 707 140 obtained from Derwent World Patent Index.
Abstract of German Publication No. 37 13 580 obtained from Derwent World Patent Index.
European Search Report of counterpart European Application No. 96 10 6593.5, Applicant, Voith Turbo GmbH.

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