SE513641C2 - Compressed air level control device, especially for motor vehicles - Google Patents

Abstract

The vehicle is fitted with pneumatic suspension elements on each wheel and with a parking brake acting on each axle. The parking brake is lifted on one axle during manual adjustment of the suspension. This reduces mechanical stress. If the vehicle starts to roll, after release of one parking brake, the suspension adjustment is blocked and the full parking brake action is restored. The suspension control has sensors to monitor the actual spacing between the suspension and the vehicle and compare same with the selected values. The vehicle movement is detected by other sensors, which can include the ABS sensors.

Description

10 15 20 30 35 40 513 641 2 Forms of the invention are set forth in the dependent claims.

The invention has the advantage that the driver can leave the driver even on inclined surfaces. the cab to adjust the frame height using a scar actuator. He can thereby adjusting the vehicle's frame height at the site during loading without risk to the vehicle should come rolling.

The invention also has the advantage that the operation can be safer and more convenient.

An embodiment of the invention has the advantage that the risk of the vehicle starting rolling or sliding is greatly reduced even when slipping.

The invention will now be explained in more detail with reference to an embodiment pel.

The invention is based on an air-suspended vehicle whose frame is supported by the wheel axles via bellows. The pressures in the balloon axia that support the frame determine its level, by which is meant frame height above the wheel axles.

Furthermore, the air-suspended vehicle is equipped with electronic level control. In this purpose are set valves connected to the air bellows. When the set valves receive electric setting signals, they change the pressures in the associated air bellows by venting or venting these. Present values are determined by height sensors, which determine the present distances between the vehicle frame and the axles. The level of the frame is regulated by an electronic controller, which is supplied with a setpoint corresponding to the desired height for the distance. The regulator the current values from the height sensors are further added and affect the pressures in the air bellows with the help of the control valves.

In the event of a deviation from the setpoint, the electronic regulator changes the pressure in one certain air bellows in such a way that the present value of the distance from the sensor belonging to the bellows becomes equal to the setpoint. The electronic controller performs this level control for the individual air bellows. It is structured as a digital controller with fixed sampling inter- vall. At the times determined by the sampling intervals, the measured value is sampled from a height sensor and then applies to the next sampling time as the present value of the distance at the height sensor in question.

A vehicle with two wheel axles normally has four air bellows: an air bellows at the front axle left wheel, an air bellows at the right front axle, an air bellows at the left wheel of the rear axle and an air bellows at the right wheel of the rear axle. If instead pairs of air bellows are used at each In the present case, each rear wheel is equated with a single air bellows. Through that only three points are needed to define a flat surface in the room, it is sufficient to provide a total of only three height sensors for the four air bellows. Normally distributed the sensors with two sensors on the rear axle near the wheels on the right and left side and one sensor on the front axle approximately at the center of this.

All settings in the level controller are made using a remote control and can be made from inside or outside the cab.

The remote control is equipped with switches, which are connected to the electronic ka regulator through electrical wires. The desired height of the vehicle frame is selected using "raise" and pushbuttons designed as pushbuttons This process includes a certain amount of time (setting time) during which the change itself of the desired height is performed. During this time, the level controller's control function idle because the air bellows are inflated or deflated directly by pressing the buttons 10 15 20 25 30 40 513 641 3 when the desired height is set. After the end of the setting time, the control device returns Active. The electronic controller then electronically stores those under the manual one setting the set heights and use them as the setpoint at the continued the regulation. in The vehicle's two wheel axles, ie. the front axle and the rear axle, are equipped with their own parking brake. For this purpose, brake cylinders, at least one per axle, are fitted at both shoulders. When the brake function is on; active, they exercise a employability of wheel wheel brakes. g _;: _; ¿i ¿ Parking braking can be accomplished with spring brake cylinders of known type.

These can in a known manner be combined with a service brake part.

A spring brake cylinder is formed mainly by a brake release chamber which is bounded by one of an accumulator, veins loaded, with a piston rod connected fi spring accumulator mulator flask. g The parking brake is activated in a known manner by the brake release chamber drained by means of a handbrake valve operated by the driver. Accumulator spring pressure kraít acts via the accumulator spring piston on the piston rod, and is transmitted by this to the wheel brake.

By, as previously mentioned, separate parking brakes are used for both the wheel axles, both parking brake axles (front and rear axles) are operated when the handbrake the valve is set in its position for venting the brake release chamber.

However, if the desired height of the vehicle frame changes in the manner described above when the parking brake is effective braking effect is canceled on one of the two the wheel axles to allow a smoothing of the change due to the change in height. one in the wheelbase between the two_a_ag_l§rp_a and prevent the formation of stresses in vehicle frame. _ The braking effect can optionally be canceled on the front axle or rear axle. If it is revoked on the front axle it remains on the rear axle, and if it is suspended on the rear axle it remains On ffamaxel fl- [QQÄÅ The electronic controller cancels the braking effect by setting the using an electrically operated valve (usually a solenoid valve) again pressurizes the brake release chambers in the fi spring brake cylinders on the wheel axle where the brake the effect shall be canceled. As is well known in the art, the additional plug-in the valve device together with the other compressed air circuit devices for parking the brake. ~ - ~ - According to the invention, the cancellation of the braking effect on a wheel axle is maintained unconditionally. In the event of unfavorable ground, the vehicle will roll when the parking brake then acts on only one wheel axle due to its braking effect being canceled the other wheel axle. In such a sigzatignh, the braking effect is immediately restored to it wheel axle where it was just lifted. i _ _g_g_g_: By prioritizing the vehicle's safety precondition over all other factors is aware that certain tensions may also arise in the frame when the braking action is set.

The fact that the vehicle is starting to roll can be detected using the speed.

The electronic controller has access to the speed of the vehicle by 10 15 20 25 30 35 40 5 1 3 6 41 4 the output signal is usually denoted by C3 (other, manufacturer-dependent designations are for example B7, D3) from the tachograph (tachograph output).

The tachograph generates the signal C3 from the measured values from a sensor that senses the speed the number for a pole wheel fixed on the output shaft of the gearbox with normally 6 teeth.

The C3 signal is a standardized pulse width modulated signal that has been calibrated by adjustment, for example in a roller test bench. The pulse width modulation means that the C3 the signal sequence is formed by pulses and pulse gaps, both of which have fixed lengths. The electric The chronic pulse has an amplitude of about 8.5 V and a length that can be set fixed between about 1 ms and 5 ms. The length of the pulse shutters is determined by the set pulse length and the current speed of the network.

The speed of the vehicle is determined by examining three fl anchors in the C3 signal. The the first är appeal is the ascending fl appeal and the second fl appeal the descending fl appeal on a pulse in a C3 signal sequence. The time between the rising and falling fl anchor, ie. between the first and the second edge, the pulse length TH determines the pulse length. The third fl appeal, namely, the rising fl ank on the pulse in the next CS signal sequence, is used to determine the length of the pulse door according to the method that the time between the second and the third fl anke constitutes pulse length TL.

The value of the vehicle speed is obtained directly in km / h by sensing the fl anchors as above and insertion in the following formula: v = ___- T ” TH + TL -225 km / h At low vehicle speeds, for example if the vehicle starts to roll, follow the short first the pulse (as above, for example 5 ms) of a relatively very long pulse gap (more than 2 s at the specified pulse length and a speed of 0.5 km / h). However, the speed can time is not determined until the very long pulse door has been closed.

However, with the three-met method, it must also be possible to determine the speed of 0 km / h fast enough. For this reason, the length of the gap in the signal processing electronics is limited. roniken to a maximum time. When this time has elapsed without the pulse door having stopped, it is set vehicle speed to the value 0 km / h.

By setting this maximum time, the minimum speed is also determined as can be measured. At lower speeds, the vehicle can roll away slowly without a vehicle speed speed greater than 0 km / h is detected. Therefore, the known three-fl method is not used in the present case. In the invention, the examination of the C3 signal should instead be so lead as quickly as possible to a status indication with two possible states: they or not stationary.

The C3 signal is processed in the electronic controller in such a way that the state non-stationary is immediately indicated each time a positive fl ank (rising fl ank) on a pulse in the CS signal sequence appears. The status display is reset to the standstill state only when a predetermined minimum time has elapsed from the rising fl appeal in it recent C3 pulse without a new rising C3 fl ank has occurred.

This logic, even at the critical state of the standstill, ensures that the status is divisible to the uncritical state does not stand still for each new C3 pulse. 10 20 25 30 35 40 513 641 5 The examination of the C3 signal thus means that one of two states is determined: stationary or non-stationary. In the non-stationary state, the brake system is reset can immediately while remaining suspended in the standstill state.

In the described mode of use, the C3 signal is not used for an actual hash. determination but to detect if the vehicle is moving. If the vehicle moves, it rotates polhj ulet, whereby it travels one of the fixed geometric conditions determined road distance between two C3 pulses following each other. Other sensor signals that provide information about the vehicle's movements can also be used. instead of the signal G3 to determine the stationary and non-stationary states toothing. hrs Particularly suitable for this purpose is the ABS sensor signals from the wheels on the wheel axle. lama. The ABS sensors interact with each other on each wheel on the wheel axle attached to the pole wheel and thanks to the high gear ratio of the pole wheel (for example 100) both high resolution and large number range. By processing the measured values from the ABS sensors, it is thus possible to quickly and safely determine the non-stationary condition.

If the ABS sensors are used to determine the stationary and non-static conditions At standstill, the ABS sensors at the left and right wheels are preferably used on the wheel axle where the braking action is canceled in the manner described above.

Using these sensors to detect motion also has another advantage. If the vehicle is slipping due to slippery ground after the braking effect has been lifted on one the wheel axle receives an indication of the incipient sliding movement from the sensors on the wheels which may roll due to the brake caliper being lifted already at a first hint of sliding movement. By quickly restoring the brake lever on this wheel axle as a result of hint of sliding motion, it is usually possible to prevent the vehicle at all begins to slide noticeably on the slippery In this embodiment, the sensitivity for determining the stationary with is selected starting point from the geometric conditions of the vehicle. The wheels that are free to roll more, of course, also to rotate in the event of a change in the wheelbase which, according to the the description arises when the height changes. It is in the nature of the invention to rotational movements in the event of a change in wheelbase shall be permitted.

Thus, when determining the sensitivity, consideration must be given to the maximum wheelbase change caused by the change of elevation position. This wheelbase distance can calculated from the magnitude of the change in the set height and the geometry of the axle suspensions metric measurements. ”_ G In the same way as in the previously described processing of the C3 signal, read the signals from the ABS sensorsiši: i_ of pulses formed when the ABS sensors pole wheel rotates. _ "___ When determining the state of the standstill, a separate count is made during the setting the timing of the pulses from both Aëåfs sensors on the wheels that can roll freely. On so In this way, two count values are obtained, which for each sensor consist of the sum of the number of pulses fi ° am to the time considered. From the larger of the two count values, one is formed rolling path distance by using the count value and the sensor resolution to calculate (product formation) the distance of road that the affected wheels have moved towards the ground by scrolling. m * 10 15 513 641 6 As long as the rolled road distance is less than the above-described wheelbase road distance the condition is considered stationary. If, on the other hand, the rolled road section exceeds The wheelbase distance is a wheel movement that is no longer conditioned by a wheelbase change. ring. In this case, it can be assumed that the braked wheel axle has begun to slip, and the condition non-stationary is activated immediately. Braking action on the wheel axle whose brakes have been released is then also reset immediately in the manner previously described. g In newer vehicle types, the vehicle has an electronic data bus (usually a bus according to The CAN standard), which connects various electronic devices, such as controllers and sensors, with each other and transfer data between these devices.

If the vehicle has a data bus, it is advisable to transfer the measured values from the ABS the sensors to the electronic controller through the data bus. Thereby, they can sensors which already exists for the ABS control is used together to determine whether the vehicle is standing still in connection with a level control, whereby a duplication can be avoided. Through In this case, the data bus does not transmit the wheel speeds determined by the ABS control electronics. without the above-mentioned pole wheel pulses from the ABS sensors to the electronic one regulator. .

The connection via a data bus saves extra hardware costs and reduces fault susceptibility as the number of components becomes lower.

Claims (8)

10 15 20 25 30 513 641 7 Patent claims 1. A pressure-driven level control device, in particular for motor vehicles, having the following characteristics: - (a) the frame of the vehicle is supported in relation to the wheel suspension for two axles via air bellows, - (b) the height of the vehicle frame is determined by the a valve device, - d) a control device automatically keeps a set height for the vehicle frame constant regardless of the size of the load, - e) the set height can be changed with a manually operated device, - f) the control device is set to idle during the time a manual change of the set height is in progress, - g) if the parking brake is applied, its braking effect is canceled on one of the two wheel axles during the change in height and - h) maintained on the respective other wheel axle, characterized in that ~ - i) if the vehicle stands still, the braking effect is restored on the wheel axle where it was lifted. Device according to claim 1, characterized in that the set height constitutes a desired distance between the vehicle frame and the wheel axles, that the actual distances between the wheel axles and the vehicle frame are sensed by sensors, and that the control device is electronic and uses the desired distance. setpoint and the actual distances as actual value. Device according to Claim 2, characterized in that the electronic controller is a sampling controller with a fixed sampling time interval. Device according to Claim 2 or 3, characterized in that the non-stationary state is determined by a sensor signal which depicts the movement of the vehicle. Device according to claim 4, characterized in that the sensor signal is formed by the tachometer signal of the vehicle. Device according to Claim 5, characterized in that the non-stationary state is determined when the first rising fl anchor in the vehicle's tachometer signal occurs. Device according to Claim 4, characterized in that the sensor signal is formed from the data from the two ABS wheel sensors on the wheel axle whose braking action is canceled. Device according to claim 7, characterized in that the measured values from the wheel sensors are supplied to the electronic controller via the vehicle's data bus.