CONTROL- AND OPERATING SYSTEM, IN PARTICULAR FOR A HYDRAULIC ACTUATOR OF A FOLDING ROOF OF A VEHICLE

Abstract: Control and operating system comprising a hydraulic cylinder (1) for moving a load (2). The piston (3) bounds a working chamber (4) which, if fed with oil, moves the load connected to the piston against the force of gravity. The working chamber (4) is connected to a pump (7) through a line (6) in which a non-return valve (10) and an electromagnetic control valve (12) are accommodated. When not energized, the working chamber (4) is connected to a reservoir (9), and when energized to the pump (7). The control unit is designed in such a way that in the "holding" position of the control button - the control valve (12) is energized continuously for a first period, and in a subsequent, second period is energized and not energized intermittently. As a result of this, the load is lowered stepwise during the second period.

Description: Control- and operatingsystem, in particular for a hydraulic actuator of a folding roof of a vehicle. The invention relates to a control and operating system according to the preamble of claim 1. Such a system is known from German Offenlegungs- schrift DE 38 26 789. By means of the control and operating system described in this publication hydraulic cylinders which serve to move various parts of the foldable roof unit are controlled by means of electro-magnetically operated spring-return 3/2 control valves. In the fully opened and the fully closed position of the foldable roof unit the control valves concerned are not energized, so that the hydraulic system is pressureless in that case. In order to make it possible to hold the foldable roof unit in an intermediate position, which position lies between the fully opened and the fully closed position of the foldable roof unit, the known system provides for a "holding condition", in which a downward movement of parts of the foldable roof unit under the influence of gravity is prevented. In this position the pump of the hydraulic system is switched off, and a "holding function" is obtained by maintaining energization of the electromagnetic control valves belonging to the working chambers of the cylinders which produce a movement of one or more parts of the foldable roof unit against the force of gravity. In the case of the known system a non-return valve placed between such a working chamber and the pump in that case prevents hydraulic fluid from flowing out of the working chamber concerned, with the result that the parts of the foldable roof unit operated by the cylinder concerned are held in place in a stationary position. The problem is that the electromagnetic control valves used for these systems may be energized continuously only for a limited period, because otherwise the electrical part of these control valves can become damaged through overheating. That is why it is proposed in the abovementioned publication that the control unit should be wo.--™,, . . . provided with a time switch which stops energization after a specific period has elapsed. The result of this is that the part of the foldable roof unit which has been "held" by the control valve concerned until then will begin to move 5 under the influence of gravity. This downward movement can be slowed down in a known manner by taking additional measures such as placing a throttle element in the line to the reservoir or by incorporating other decelerating systems, such as friction couplings, in the foldable roof 10 mechanism. In the case of some roofs of stiff fabric material the downward movement is slowed down to some extent by the resistance of the fabric to folding. However, in the case of foldable roofs with relatively heavy and rigid roof parts in particular, the downward movement will 15 be very rapid unless it is deliberately slowed down. This can lead to injury to the passengers in the vehicle, or in any case to a shock reaction. The object of the present invention is therefore to propose measures which make it possible in a simple manner 20 to end the holding function safely, in particular without adaptation of the hydraulic set-up of the known operating and control system. This object is achieved by providing a control and operating system according to the preamble of claim 1, 25 which is characterized in that the electric control unit is designed in such a way that in the condition of the control element for holding the foldable roof unit in an intermediate position said control unit supplies a signal to the electromagnetic control valve during a first period, 30 by means of which the control valve is constantly energized during this first period, and in a subseguent, second period supplies a signal to the electromagnetic control valve, by means of which the control valve is intermittently energized and not energized such that the 35 part of the foldable roof unit which is movable by the hydraulic piston-cylinder unit executes a downward movement under the influence of gravity in a stepwise manner during the second period. In the system described in DE 38 26 789 the measure according to the invention can be achieved by adapting the program stored in the microprocessor of the control unit 15. In particular, it is advantageous that the hydraulic set-up need not undergo any change in order to realize the inventive idea. The first period, in which the control valve concerned remains energized continuously, can be selected for so long that the holding function need not be broken off for a duration which is considered normal in practice for said holding function. During the second period, the period of time during which the control valve concerned is not energized in each case can be selected in such a way that a stepwise, and in particular slow downward movement of the corresponding part of the foldable roof unit occurs. This is safe for the passengers and any bystanders present. In particular, it is found that, due to the inertia of the parts of the roof, it is hardly noticeable that the downward movement is taking place in a stepwise manner. Another advantage of the invention is that the battery of the vehicle, which supplies the energy for keeping the control valve energized, can be saved, since the holding function can now be completed safely. Apart from the application described above for foldable roof units, the exclusive right applied for also relates to the use of the inventive idea in other similar situations, this being described in claim 4. The invention will now be explained in greater detail with reference to the part of an electro-hydraulic circuit diagram shown in the single figure of the drawing. In the drawing double-acting hydraulic cylinder 1 serves to open and close cover 2 of a foldable roof unit (not shown) of a motor car. Such a cover 2 is generally used for covering the opened-up roof, which is accommodated in a compartment at the back of the car. Piston 3 of the cylinder 1 forms two working chambers 4 and 5 with variable volume in the cylinder 1. As can be seen clearly, supplying hydraulic fluid to the working chamber 4 leads to the cover 2 moving upwards. The working chamber 4 is connected by way of a line 6 to a pump 7. The pump 7 can suck in hydraulic fluid by way of line 8 from reservoir 9 and supply it to the working chamber 4. The line 6 contains a non-return valve 10, which prevents flow from the working chamber 4 to the pump 7, but allows it to pass in the opposite direction. An electro- magnetically operated 3/2 valve 12 with spring return mechanism is accommodated in the line 6 between the non¬ return valve 10 and the connection to the working chamber 4. The valve 12 is driven by an electric control unit 14, which is connected by way of a signal line 15 to the valve 12. The control unit 14 comprises a control button 16, which can be operated by the driver of the motor car. The button 16 has three positions I, II and III. So long as the driver holds the button 16 in position I, the control unit 14 makes the foldable roof of the car open, and in position III makes it close. When the button 16 is released, it assumes position II. If the button is in position II and the foldable roof is not in the fully opened or the fully closed position, the control unit 14 produces a "holding function". This means that, for example, when the cover 2 is in the position shown in the drawing, hydraulic fluid is prevented from flowing out of the working chamber 4 into the reservoir 9 and the cover 2 is prevented from folding down unimpeded under the influence of its own weight. For this purpose, the control unit 14 according to the invention is designed in such a way that while the holding function is switched on for a first period, which can be for a number of minutes in practice, the valve 12 is kept energized. The non-return valve 10 prevents hydraulic fluid from flowing out of the working chamber 4, with the result that the cover is held up. In a variant which is not shown the non-return function can be integrated in the valve 12, so that it is possible to dispense with the non-return valve 10 placed separately in the line 6. As already stated, the electromagnetically operated valves used in this field do not permit unlimited energization, because overheating can then occur. The present invention therefore ensures that before any overheating can occur, the continuous energization during the first period is followed by an intermittent energization for a second period. In said second period the signal delivered by the control unit 14 by way of the line 15 to the valve 12 is such that the valve 12 is alternately energized and not energized. The result of this is that during each phase of the valve 12 not being energized hydraulic fluid can flow out of the working chamber 4 into the reservoir 9. The cover 2 will consequently move downwards in a stepwise manner under the influence of its own weight. Through a suitable selection of the duration of being energized and not energized, the downward movement can be given any desired course. For instance, the movement can be slow at first and can speed up slightly on approaching the end position. Determining the desired movement course is very simple if the control unit comprises a microprocessor, because all that is then necessary is the input of a suitable program. The duration of the second period is preferably chosen to be so long that the cover can reach its end position from each initial position. It is clear that the holding function described here with reference to the cover 2 can also be achieved for other parts of a foldable roof unit.

Claims: C L A I M S 1. Control and operating system, comprising a hydraulic piston-cylinder unit (1) for moving a part (2) of a foldable roof unit of a vehicle, in particular for moving a foldable roof and/or a rear cover part of the foldable roof and/or a cover (2) which covers the foldable roof in the fully opened position and for opening and storing the foldable roof is temporarily opened and closed again respectively, in which the piston (3) bounds a variable working chamber (4) in the cylinder (1), which working chamber, if fed with hydraulic fluid, moves a part (2) of the foldable roof unit connected to the piston (3) against the force of gravity, and which working chamber (4) is connected through a line (6) to a pump (7) for supplying hydraulic fluid to said working chamber, while in the line (6) between the pump (7) and the working chamber (4) an element with non-return function (10), which blocks flow in the direction from the working chamber (4) towards the pump (7) , and an electromagnetically operated control valve (12) are accommodated, which control valve when not energized connects the working chamber (4) to a pressureless reservoir (9) for hydraulic fluid, and when energized connects the working chamber (4) to the pump (7) , and the system also comprises an electric control unit (14), which is connected through a signal line (15) to the electromagnetic control valve, which control unit has a control element (16) with conditions for opening (I) , closing (III) and holding (II) in an intermediate position of the foldable roof unit, while for holding the foldable roof unit in an intermediate position the electromagnetic control valve is energized, with the result that the element with non-return function (10) prevents hydraulic fluid from flowing out of the working chamber (4) concerned, characterized in that the electric control unit (4) is designed in such a way that in the condition (II) of the control element (16) for holding the foldable roof unit in an intermediate position said control unit supplies a signal to the electromagnetic control valve (12) during a first period, by means of which the control valve is con¬ stantly energized during this first period, and in a subsequent, second period supplies a signal to the electromagnetic control valve (12) , by means of which the control valve is intermittently energized and not ener¬ gized, such that the part (2) of the foldable roof unit which is movable by the hydraulic piston-cylinder unit (1) executes a downward movement under the influence of gravity in a stepwise manner during the second period. 2. Control and operating system according to claim 1, in which the element with non-return function is a non¬ return valve (10) which is placed in the line between the pump (7) and the electromagnetically operated control valve (12). 3. Control and operating system according to claim 1, in which the element with non-return function is a non¬ return element which is integrated in the electromag¬ netically operated control valve. 4. Control and operating system, comprising a hydraulic piston-cylinder unit (1) for moving a load (2), in which the piston (3) bounds a variable working chamber (4) in the cylinder (1) , which working chamber, if fed with hydraulic fluid, moves the load (2) connected to the piston (3) against the force of gravity, and which working chamber (4) is connected through a line (6) to a pump (7) for supplying hydraulic fluid to said working chamber, while in the line (6) between the pump (7) and the working chamber (4) an element with non-return function (10) , which blocks flow in the direction from the working chamber (4) towards the pump (7) , and an electromagnetically operated control valve (12) are accommodated, which control valve when not energized connects the working chamber (4) to a pressureless reservoir (9) for hydraulic fluid, and when energized connects the working chamber (4) to the pump (7) , and the system also comprises an electric control unit (14) , which is connected through a signal line (15) to the electromagnetic control valve, which control unit has a control element (16) with conditions for raising (I) , lowering (III) and holding (II) in an intermediate position of the load (2) , while for holding the load in an intermediate position the electromagnetic control valve is energized, with the result that the element with non-return function (10) prevents hydraulic fluid from flowing out of the working chamber (4) concerned, characterized in that the electric control unit (14) is designed in such a way that in condition (II) of the control element (16) for holding the load in an intermediate position said control unit supplies a signal to the electromagnetic control valve (12) during a first period, by means of which the control valve is constantly energized during this first period, and in a subsequent, second period supplies a signal to the electromagnetic control valve (12), by means of which the control valve is intermittently energized and not energized, in such a way that the load which is movable by the hydraulic piston-cylinder unit (1) executes a downward movement under the influence of gravity in a stepwise manner during the second period.

Inventors: MENTINK LAURENTIUS ANDREAS GER, WIND ROELOF JAN, MENTINK, LAURENTIUS, ANDREAS, GERARDUS, WIND, ROELOF, JAN
Applicants: APPLIED POWER INC, MENTINK LAURENTIUS ANDREAS GER, WIND ROELOF JAN, APPLIED POWER INC., MENTINK, LAURENTIUS, ANDREAS, GERARDUS, WIND, ROELOF, JAN
Application year: 1996
Main classification: B60J7
IPC codes: B60J7