JPS6071334A - Method of hydraulically driving wheel for car additionally - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides, in addition to the main drive wheels driven by the prime mover via a torque converter or gearing, the wheels of a vehicle part-time by means of a closed hydraulically actuated circuit. Regarding the method of additionally hydraulically driving the vehicle, more specifically, the hydraulic operating circuit includes a wheel motor which is supplied with operating fluid by a variable displacement pump, and a variable displacement pump which is directly driven by a prime mover. , a control pump, and wherein the working liquid flow or working liquid pressure is controlled by a switchable control pump flow.

Motor graders are used to carry out large-scale production operations. When excavating hard soil, work on upward slopes;
In other words, for any work on roadbeds that are difficult to tow,
It is important to utilize the entire weight of the machine as towing weight.

The front axle of this type of vehicle, ie a motor grader, carries approximately one-third of the total weight. Now, if the vehicle is equipped with all-wheel drive in addition to the rear main drive wheels, ie the front axle can be additionally driven, the forward force increases by up to 50%. To date, an additional drive of the other wheels has not been realized, which applies in particular only to motor graders, because of the special construction. In such vehicles, mechanical drive systems, for example due to flexible shafts, have a high constructional cost. Moreover, other working functions, such as plate mobility, should be maintained,
Furthermore, it is necessary to maintain the maximum steering angle, etc., and to obtain sufficient ground clearance for the front axle.

If a technical implementation could be realized that would allow additional drive of the front wheels at a small cost without reducing the functionality of a conventional motor grader, it would be a traffic-friendly implementation.

However, there is a basic problem of synchronizing the running speed of the main drive wheels with the running speed of the additionally drivable drive wheels.

It is already known to drive the drivable additional drive wheels of self-propelled working machines with a main drive wheel drive hydrostatically by means of a multi-speed transmission. This multi-stage transmission includes a hydro pump and a control pump each driven in proportion to the rotational speed of the vehicle main drive machine. This hydro pump provides a working fluid flow that can be supplied to the additional drive wheels. The control pump, which is designed as a constant-displacement pump, tensions its supply flow via the throttle and can influence the working liquid flow of the additional wheels by means of the pressure upstream of the throttle via the control device. . The structure of this control device is the same as that of a known automatic control device for a vehicle drive system in which the hydro pump is formed as a variable displacement pump. This variable displacement pump can increase the displacement by means of pressure upstream of one or more restrictors against the spring force, and can reduce the displacement by means of the actuating pressure in the additional drive (West Germany). National Patent No. 5035522).

In this type of device, the control pump flow is manually adjusted by a hydraulic valve in order to influence the drive of the additional wheels via a variable displacement pump. Therefore, it is not possible to achieve stable operating conditions of the additional drive wheels in different gears of the main drive wheels, especially over a wide rotational speed range.

The object of the invention is to provide a method for driving wheels that are selectively and additionally hydraulically driven in a vehicle in which the main drive wheels are driven by a prime mover via a torque converter or a gearing, and a device for implementing this method. It is to be. In this case, the rotational speed of the additionally driven wheels must be matched to the rotational speed of the main drive wheel.

This problem arises because, in the method described at the beginning, due to the superposition of the working liquid flow control, the working liquid pressure is dependent on the converter stage output speed and also on the ratio of the prime mover output speed to the gearing output speed. This problem is solved by adjusting according to a function that is appropriately set in advance.

In this case, the suitably preset function varies along steps of a step curve, or linearly or along a conic section. The form of the function is especially chosen to be the same as the converter or gearing output function.

When the main drive wheels are driven by an internal combustion engine via a torque converter or a gearing and optionally and additionally use an automatic control device for the working fluid flow of the driven wheels, a ratio generator is provided. The output speed of the prime mover and the output speed of the converter stage or gearing are applied to the input of the ratio generator of each stage or switching stage of the main drive wheels, and the ratio of the input values and the corresponding output value is determined as a ratio. given to the generator. Furthermore, a function generator is provided which generates a function value from a selectable predetermined function in dependence on the output value of the ratio generator. Furthermore, to complete the control circuit, the pressure changes in the actuating circuit are fed into the function generator as feedback.

Assuming that the known operating circuit for additionally driving the other wheels by means of a novel automatic control is operated constantly, for example an internal combustion engine directly driving the variable displacement pump and the control pump of the automatic control device at the same time. At a number of no-load operations, a steady pressure condition occurs in the operating circuit. that time,
The predetermined control angle of the two adjusting mechanisms that operate relative to each other with spring force corresponds to the working fluid flow rate supplied by the variable displacement pump. When the main drive wheels are activated, a ratio between the rotational speed of the internal combustion engine and the output rotational speed of the torque converter or gearing is generated in the ratio generator and, depending on this value and corresponding to a selectable predetermined function, Function values are generated within a function generator. The pressure value of the working circuit is compared with said function value in a function generator, and a positive deviation of the working circuit pressure with respect to this function value changes the control angle of the variable displacement pump in the direction of decreasing the working fluid volume. given to the pump with. If no positive deviation occurs, the function generator has no influence on the variable displacement pump. The operating state is already stable when, due to an increase in the rotational speed of the internal combustion engine, a higher pressure is created in the operating circuit than would be the case at the idle operating speed. However, no control via the function generator takes place until the pressure in the operating circuit changes after the rotational speed of the internal combustion engine has increased.

If the output value of the ratio generator changes further, another function value occurs in the function generator, provided that the selected function is the same, and after comparing it with the respective pressure in the working circuit with respect to the control deviation. and is given to this pump to adjust the control angle of the variable displacement pump. In principle, a predetermined amount of liquid is supplied in the working circuit through a variable passenger pump by means of a known automatic control that is dependent on the rotational speed of the internal combustion engine, so that the working pressure is adjusted accordingly; descend.

A selectable predetermined function produced by the function generator depending on the output value of the ratio generator may be represented by a hydraulic element. For example, a plurality of limit valves connected in parallel, one at a time, can be provided to generate a step-like function along a step curve. The respective overpressure flow of this restriction valve is controlled in order to adjust the control angle of the variable displacement pump so as to reduce the working liquid pressure by reducing the working liquid flow.
Supplied to variable displacement pump.

In a similar embodiment with known electronic components, the output values of the ratio generator can be fed to an electronic function generator. This output value corresponds to the measured rotational speed ratio and may itself be an electronic signal. The electronic function generator generates a value f (p
) with the respective detected function value. The electronic output signal of the function generator can be supplied to the variable displacement pump via a hydraulic actuator in order to change the control angle of the variable displacement pump.

The present invention will be explained in detail based on the figures.

Starting from a known traction drive and a known automatic control for selectively additionally driving the other wheels.

In Figure 1, the prime mover, especially the internal combustion engine, is at the converter stage 3.
The main drive wheels 4 of the vehicle are driven through the torque converter 2 including the torque converter 2 . At the same time, the variable displacement pump 5 and the control pump 6 are driven by the prime mover 1 via the shaft. Both pumps of the automatic control system operate in a closed hydraulically operated circuit. This actuating circuit supplies actuating fluid to the wheel motors 7.8, thereby rotating the additional driven wheels 9,10. A hydraulically actuated clutch 11, 12 is provided between the two wave drive wheels.

Furthermore, the wheel motor is equipped with two wheel motor pressure limiting valves 13.
14 ensures safety.

The automatic control device includes a fixed throttle 17, a variable throttle 18, and a pressure limiting valve 1 in its control circuit for adjusting the open-adjust element 15 and the close-adjust element 16 of the control angle of the variable displacement pump.
9 and % directional control valve 20. The overpressure valve 21 limits the control pressure in the control circuit to a constant, adjustable value. The operating circuit is supplied with liquid from the uniform liquid flow of the control pump 6 via the non-return valve 22, and the clutch 11, 12 can only be engaged by means of the solenoid valve 24 once the control circuit pressure has been reached. This also applies to the operational coupling of the additional drive wheels.

In the structure of Chichi, the working liquid flow control superimposed strands,
As a result, the working fluid pressure is selected as a function of the ratio of the output speeds of the prime mover, converter or transmission and is regulated in accordance with the course of the given function.

A ratio generator 25 is provided for this purpose.

The input 26.27 of this ratio generator has the measuring point 28°2
The output rotational speeds of the prime mover and the converter measured in step 9 are used as a force, and the output value 6o of this ratio generator 25 corresponds to the ratio of the input values. Furthermore, a function generator 31 is provided which, depending on the output value 30 of the ratio generator 25, generates a function value from a selectable function. Additionally, a value f(p) corresponding to the pressure in the operating circuit is fed back to line 52.
55 and is supplied to the function generator 31. A positive deviation of the working circuit pressure with respect to the function value that occurs will cause the output line 34% port valve 2o and the closed-adjustment to adjust the control angle of the variable displacement pump to reduce the working liquid volume. The variable displacement pump 6 is supplied via the element 16.

Just to be sure, other functions of the % boat valve 2o will be explained. Its function is to determine the direction of travel depending on the adjustment of the port valve. This port valve is switched to its respective position by magnetic forces. The % port valve 65 for the pressure value supplied from the operating circuit to the function generator is switched depending on the direction of travel.

S・r provided in the structural unit with the function generator 61
Border 36 provides a signal to switch solenoid valve 24.

Figure ff12 shows an example for displaying a function in a general linear form using a hydraulic element. In this case, technically identical parts are provided with the same reference symbols.

In the case of the illustrated circuit of the magnetically actuated X hydraulic valve 37, the pressure led from the actuating circuit via the line 32 is applied to the limiting valve 58, and in case of a positive deviation from the regulated pressure, it is applied as a control deviation. It is led to the variable displacement pump 5 via the output line 34. When the
guided by. In this case, the limit valve 68 and the other limit valve 39.4
The zero regulated pressure stages are selected to be consecutive, for example 250 bar, 150 bar and 100 bar.

In this case, a control pressure is generated at the throttle 41, which pressure is higher than the supply pressure that was present up to that time.

As mentioned above, the display of the selectable function can also be carried out by means of electronic elements known per se, and furthermore, the control deviation can be transmitted as an electronic output signal via the hydraulic actuator to the signal generator of the variable displacement pump. Ru.

[Brief explanation of the drawing]

FIG. 1 shows the basic hydraulic circuit for operating the method according to the invention and the device for carrying out the method, and FIG. 2 shows the hydraulic elements for presetting the selectable functions. FIG. 1... Original LVb machine 2... Torque converter 6... ° converter stage 4... Main drive wheel 5... Variable displacement pump 6... Control pump 7.8... Wheel motor 9. 10. Wheel motor 11.12...Clutch 13.14...Wheel motor pressure limiting valve 15...Open-adjusting element 16...Closed-adjusting element 17...Fixed throttle 18...Variable Throttle 19...Pressure limiting valve 20...5〈Botler 1! 21... Overpressure valve 22, 23... Check valve 24... Solenoid valve 25... Ratio generator 26.27... Input 28.29... Measurement point 30... Output value 31 ... Function generator 52.33 ... Pipe line 34 ... Output pipe line 55 ... % boat valve 36 ... Switch Otsu 7 ... % hydraulic valve 5B ... Limiting valve 59.40 ...Other restriction valves 41 ...Aperture agent Mitsuyoshi Ezaki Agent Mitsufumi Ezaki

Claims (1)

Claims: 1. In addition to the main drive wheels driven by the prime mover via a torque converter or gearing. A method of hydraulically driving a plurality of wheels of one vehicle part-time by using a closed hydraulic operating circuit,
The hydraulic operating circuit includes a wheel motor supplied with operating fluid by a variable displacement pump, a variable displacement pump directly driven by the prime mover, and a control pump,
In methods in which the working liquid flow or the working liquid pressure is controlled by a switchable control pump flow, the working liquid pressure is controlled by the superposition of the working liquid flow control to the output rotational speed of the converter stage (3) or the output rotational speed of the gearing. The method is characterized in that the adjustment is made according to a suitably predetermined function depending on the ratio of the output speed of the prime mover (1) to the number of rotations. 2. A method according to claim 1, characterized in that the function, which is suitably set in advance, varies along a plurality of steps of the step curve. 6. The method according to claim 1, characterized in that the appropriately preset function is linear. 4. The method according to claim 1, characterized in that the predetermined function is varied along a conic section. 5. Method according to claim 1, characterized in that the suitably predetermined function corresponds to a convergence output function or a gearing output function. 6 In addition to the main drive wheels which are driven by the prime mover via a torque converter and/or a pulley gear, the main wheels of a vehicle can be additionally operated part-time by means of a closed hydraulic actuation circuit. and a hydraulic operating circuit comprising a wheel motor supplied with operating fluid by a variable displacement pump, a variable displacement pump directly driven by a prime mover, and a control pump. , the working fluid flow or the working fluid pressure is controlled by a switchable control pump flow, and the superposition of the working fluid flow control allows the working fluid pressure to be adjusted to the output speed of the prime mover relative to the output speed of the converter stage or the output speed of the gearing. A device for carrying out a method which is adjusted according to a suitably predetermined function in dependence on the ratio of rotational speeds, the ratio generator (
25) is provided, and the output rotational speed of the prime mover (1) and the output rotational speed of the converter stage (5) or gearing or a similar value are determined for each converter stage or switching of the main drive wheel (4). A device, characterized in that the output values (3) of the ratio generator, applied to the inputs (26, 27) of the ratio generator for the stage, correspond to the ratio of the input values. Z function generator (51) is provided, and this function generator generates a function value from a suitably preset function depending on a given output value (3o) of the ratio generator (25). Device according to claim 6. 8. Device according to claim 7, characterized in that a value corresponding to the pressure in the operating circuit is given as feedback to the function generator (31). 9. The resulting function. Patent characterized in that a positive deviation of the pressure of the working circuit with respect to the value is applied to the variable displacement pump (6) in order to adjust the control angle of the variable displacement pump (6) in the direction of decreasing the working liquid volume. The device according to claim 8. 10 The device according to claim 9, characterized in that the function generator (3+) is a hydraulic element. 11 The numerical value generator (51) is a ratio generator. A plurality of restriction valves (3B. 39.40) are provided which are switched depending on the output value of the pump (25), the overpressure flow of each of which restricts the working liquid flow of the variable displacement pump (5) and thus A device according to claim 10, characterized in that it is supplied to the variable displacement pump in order to adjust the control angle of the pump in the direction of reducing the working fluid pressure.12. The device according to claim 9, characterized in that it is an electronic element and that the control deviation is provided via a hydraulic actuator to a variable displacement pump (5)K.13. 13. Device according to any one of claims 6 to 12, characterized in that it has a connected connector.