Motor vehicles – With means responsive to speed of vehicle for maintaining...
Patent
1997-11-17
1999-11-09
Swann, J. J.
Motor vehicles
With means responsive to speed of vehicle for maintaining...
180178, 180179, 701 93, B60K 3100
Patent
active
059795824
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a device for regulating the speed of a motor vehicle provided with a braking device, comprising a control actuatable by the driver of the vehicle, with first means for setting a command value for a speed, a sensor for sensing the actual value of the speed and a processing unit connected to the engine throttle and to the braking device, said command value and actual value being fed into and compared in said processing unit, which is disposed to send signals to the throttle and/or brake device depending on the difference between said values, said processing unit being disposed when driving downhill to allow a maximum speed, which lies above the command value set by means of the first means.
SUMMARY OF INVENTION
Devices for controlling vehicle speed by controlling the throttle opening, so-called cruise controls, are generally known and are available in both passenger vehicles and trucks. They are capable of maintaining constant vehicle speed on a level road and when driving uphill, but allow the vehicle to exceed the set speed when driving downhill. An automatic brake control function has also recently been introduced, especially in heavy trucks and buses with so-called auxiliary brakes, e.g. retarders, exhaust brakes and decompression brakes. Different systems are known. In the simplest one, the driver sets the minimum speed with the ordinary cruise control and the maximum speed, i.e. the speed at which the auxiliary brake is activated, is set with a separate control. In another system, these functions are integrated in a single control, whereby a certain excess speed on the order of 5-10 km/h is allowed before the braking device is activated.
When driving on varying level and hilly roads with the integrated cruise control in the automatic position, the throttle opening will strive to maintain the set speed up to the crest of a hill and will activate the braking devices as soon as the allowed excess speed has been reached after the crest. This results in poor fuel economy because a portion of the kinetic energy of the vehicle on and immediately before the crest of the hill will be immediately braked off and not be used for driving the vehicle. An active driver can of course deactivate the cruise control just before the crest of the hill, so that it no longer strives to maintain or at least not increase the vehicle speed, utilizing the kinetic energy of the vehicle to carry it over the crest, and thereafter once again activate the cruise control to re-establish the brake function. Hitherto known cruise controls of the type in question do not, however, have controls and control functions which directly encourage such active operation.
The purpose of the present invention is in general to achieve a device of the type described by way of introduction, which has a control and control functions which are particularly suited for an active and economical method of operation.
This is achieved according to the invention by virtue of the fact that the cruise control has second means for setting to a first position, in which the processing unit controls both the throttle and the brake device to keep the vehicle speed constant, a second position, in which the processing unit only controls the throttle to keep a minimum speed which is the set command value, and a third position, in which the processing unit only controls the braking device to limit the maximum speed in relation to the set command value.
With the aid of the control according to the invention, the driver can simply shift between speed control, which regulates both the throttle opening and the brake, and regulating only one of these. If the vehicle is driven uphill followed more or less immediately by a downhill stretch, a driver who knows the road can shift the control from the first to the third position prior to the crest. After passing the crest of the hill, he will not need to shift the control, since the braking function is activated in the third position.
In a further developed, preferre
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Andersson Gosta
H.ang.kansson Nils Olof
AB Volvo
McClellan James S.
Swann J. J.
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