Motor vehicles – Steering gear – With fluid power assist
Reexamination Certificate
1998-09-14
2001-02-06
Swann, J. J. (Department: 3611)
Motor vehicles
Steering gear
With fluid power assist
C180S442000
Reexamination Certificate
active
06182786
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a hydraulic steering device, having a housing in which an inner control slider and an outer control slider are arranged so that they are rotatable relative to one another and which together are arranged as alterable flow path means between a supply connection arrangement and a working connection arrangement.
Such a steering device is known, for example, from DE 43 42 933 A1.
In steering devices of that kind, the supply connection arrangement generally comprises a pump connection and a tank connection. The working connection arrangement generally comprises two working connections. Depending on which of the two working connections is acted upon by pressure, a connected steering motor is moved in one or the other direction.
In most cases the inner control slider is moved by means of a steering handwheel, that is, is rotated with respect to the outer control slider. In this case a flow path between the pump connection and the corresponding working connection, and between the other working connection and the tank connection is unblocked with more or less throttling. Hydraulic fluid therefore flows from the pump by way of the steering motor to the tank again. At the same time, the hydraulic fluid actuates a measuring motor which rotates the outer control slider relative to the inner control slider and thus brings both control sliders into their original aligned position again in which the flow path is closed.
In some cases it is desirable to be able to steer a vehicle that is equipped with such a steering device not only from a driver position using the steering handwheel, but also, for example, in the case of self-propelled working machines, from several positions.
This has primarily been achieved until now by mounting a drive motor on the steering handwheel shaft, which motor, when suitably actuated, takes on the function of the human hand as drive means for that hand wheel shaft. Additional installation space is required for that motor, however.
SUMMARY OF THE INVENTION
The invention is based on the problem of providing a remote control facility of simple construction for the steering device.
In a hydraulic steering device of the kind mentioned in the introduction, that problem is solved in that each control slider is connected to a driving slider, and between the two driving sliders there is created at least one pressure chamber which is acted upon by fluid under pressure, and a change in volume of the pressure chamber effects a relative displacement of the two control sliders.
The customary point of application, namely the steering handwheel shaft, for a remote steering device is therefore abandoned. The remote control now acts directly on the two control sliders and can there effect a relative displacement of the two control sliders. The corresponding generation of torque is effected simply by the pressure loading and the resultant expansion of a pressure chamber, which is formed between the two driving sliders, so that additional external motors can be omitted. The direct intervention in the kinematics of the two control sliders not only enables, as was previously the case, the inner control slider to rotate with respect to the housing, in which case the outer control slider then had to be tracked after it (if the outer control slider was driven the inner control slider had to be tracked); in addition, a relative displacement of the two control sliders in the housing can be effected directly, so that in some cases a movement of the steering handwheel, with the endangering of operating personnel resulting therefrom, can be completely avoided. Moreover, with this kind of remote control other control principles can be pursued. For example, the customary measuring motor can be omitted. Returning of the two control sliders towards their starting position can likewise be effected by the driving sliders, if the associated control signals are made available in a different manner.
In that case is it especially preferred for at least one control slider to be formed in one piece with the driving slider associated with it. This simplifies the construction. The one-piece construction of driving slider and control slider means that additional fixing elements are no longer needed.
In an advantageous construction, provision is made for the two driving sliders to be arranged concentrically with respect to one another, the pressure chamber being arranged in an annular gap between the two driving sliders and each driving slider having a projection protruding into the annular gap and bearing against the other driving slider, which projection bounds the pressure chamber circumferentially. In this construction the increase in volume, which is effected for example, when fluid under pressure is admitted to the pressure chamber, directly causes a torque and thus a rotation of the two sliders relative to one another. No further measures are required. The size of the projections, that is, the amount they extend radially and axially, determines the available pressure application surface, which in turn, together with the pressure in the pressure chamber, defines the torque generated. Even with a relatively small annular gap, the torque required for displacing the two control sliders relative to one another can nevertheless be produced.
It is also preferred for the projections to be rounded at their free end. The free end is the end of the projections with which they lie against the respective other driving slider. This rounding reduces wear and to a certain extent improves the options available for sealing.
Preferably, each projection serves as a boundary for two pressure chambers. The possibility of being able to actuate the steering device in both directions is improved with two pressure chambers. The restoring forces are easier to apply.
Preferably, more than two pressure chambers are provided. The number of projections, and thus the number of surfaces that are available to receive pressure, also increases accordingly. In this manner, the torque can be multiplied without particular difficulties. From the point of view of the space required, in most cases it is also possible to accommodate more than two pressure chambers, because the relative displacement of the two control sliders is mostly merely less than 20° and the pressure chambers do not need to be very much bigger than that.
Preferably, an even number of pressure chambers is provided. The effect of the driving sliders in the two steering directions can thus be made uniform.
Advantageously, the fluid under pressure comes from the same pressure source as the hydraulic fluid used for the steering device. An additional pressure source is not therefore needed. The hydraulic fluid is generally available at the necessary pressure anyway. Since only a comparatively small amount of hydraulic fluid is used to operate the driving sliders, an economical operation can be achieved in this manner.
Advantageously, a control device is arranged between each pressure chamber and the pressure source. The pressure in the individual pressure chambers can then be set at will to a specific value, so that the desired relative rotation of the two driving sliders and the relative rotation of the two control sliders resulting therefrom can be effected.
The control device preferably has pulse-controlled electromagnetic valves. Using the pulse-controlled electromagnetic valves the desired pressure can be set with relatively few problems by means of the pulse duty factor. The pulse duty factor is the ratio of the open time of an electromagnetic valve to the time of a complete period, that is, the sum of the open and the closed time.
It is also an advantage that the pressure chambers are divided into two pressure chamber groups, and that for each pressure chamber group an electromagnetic valve is provided in series with a throttle, the pressure chamber group being connected to a tapping-point between the electromagnetic valve and the throttle. Because the pressure chambers are uniformly combined to form a pressure chamber
Cuff Michael
Danfoss Fluid Power A/S
Lee Mann Smith McWilliams Sweeney & Ohlson
Swann J. J.
LandOfFree
Hydraulic steering device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydraulic steering device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydraulic steering device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2609462