SU347219A1 - HYDRAULIC DEVICE FOR CONTROLLING THE FRICTIONAL SWITCHING ELEMENTS OF THE TRANSFERED TRANSMISSION BOXES OF SELF-PROPELLED MACHINES - Google Patents

Description

FIELD: transport engineering.

Basically auth. St. No. 2,25713 describes a hydraulic device for controlling the frictional gear shift elements of stepped gearboxes of self-propelled machines, mainly tractors, containing a selector mechanism for supplying the working fluid from its source to the power cylinders of the friction elements, and a hydraulic accumulator connected via valves to the pipeline, telling the selector mechanism with the power cylinder of the lockable friction element. In the case of gears without breaking the flow of power in the transmission, the known device for controlling the friction elements allows for optimum overlapping gears when the engine is fully loaded. At the same time, when connected to the hydraulic accumulator of the power cylinder of the friction element to be activated, the pressure necessary to transmit the engine torque when it is fully loaded is established in it. However, when the engine load decreases, i.e., with its partial loads, the actual safety factor of the friction element to be activated increases, which leads to jerks in the transmission when shifting gears, worsens the driver's working conditions.

The aim of the invention is to increase the smoothness of switching of the friction elements at partial engine loads.

This is achieved by having a controlled choke connected to the engine load sensor in the channel, which communicates the selector mechanism with the source of supply of the working fluid under pressure.

Pa figs. 1 schematically shows the proposed device; in fig. 2 are graphs of the change in pressure of the working fluid in the power cylinders of the switching friction elements.

The device comprises a pump 1, an overflow valve 2, a controlled throttle 3 connected to an engine load sensor, for example, a fuel supply actuator 4, a selector mechanism 5, hydraulic power cylinders 6-9 for activating friction elements, a hydraulic accumulator 10, a group of valves 11 through which a hydraulic accumulator is connected between the power cylinders and the selector mechanism. The hydraulic accumulator consists of an elastic element 12 and a squash 13.

lindrov, in which the pressure of the working fluid is currently higher than in other power cylinders, and at the same time to disconnect from the hydraulic accumulator of all other power cylinders: Three valves 17, 18, 19 are placed in the three valves 14, 15, 16. the ends of the valves 14 and 16 are four power cylinder 6-9. Valves 14 and 16 are connected to valve 15, and the latter is connected to the working cavity of hydraulic accumulator 10.

The selector mechanism 5 has a channel 20 permanently connected to the discharge line 21, as well as a drain channel 22 permanently connected to the drain. The injection line 21 connects the pump / to the selector mechanism 5.

A controllable choke 3 installed in the discharge line in front of the selector mechanism allows the passage area of the channel to be changed, through which the working fluid is supplied from the pump to the selector mechanism.

The drive control of the throttle 3 comprises a tractor 23, a lever 24 and a depth of 25 with an offset spring 26. Pedal 25 is connected to the fuel supply drive. Cran-27 serves for emergency shutdown of hydraulic accumulator W.

Before shifting gears, for example, the power cylinder 8 is turned on. At the same time, the working fluid from the pump enters through valve 2. choke 3, line 21 and selector mechanism 5 to the power cylinder 8, the piston of which compresses the package of friction discs. As a result, the friction element of the power cylinder 8 transmits the torque from the leading parts to the driven ones. The remaining three power cylinders are communicated through the channel 22 of the selector mechanism 5 with the drain, i.e. their friction elements are turned off. In addition, the working fluid under pressure is supplied to the lower end of the valve 16, moving the spool 19 up and filling the valve 16. Next, the working fluid fills the valve 15, moving the spool 18 with fluid pressure to the left, and the working cavity of the hydraulic accumulator 10, compressing its elastic element . At the same time the access of the working fluid to the other three cylinders is blocked by spools 18 and 19.

To turn on, for example, the ram 7, the driver, using the selector mechanism, rotates the valve counterclockwise, stops supplying the fluid to the ram 8, communicating with the drain, and opens the feed of the working fluid to the ram 7, disconnecting it from the draining. The injection line 21 is connected to an unfilled power cylinder 7, therefore, the pressure in the power cylinder 8 communicates with the drain. After a slight decrease in pressure, the hydraulic accumulator 10 is discharged. In this case, the working fluid from the working cavity of the hydraulic accumulator 10 through valves 15 and 16, the main cylinder 8 and the drain channel 22 is directed to the drain. The pressure in the power cylinder 8 is at the same time less than the maximum, but sufficient for the operation of the friction element without slipping.

As soon as the power cylinder 7 is filled and the pressure in it becomes higher than in the power cylinder 8, the valve 18 valve 15 under the action of the pressure difference moves from the left to the extreme right position and turns off the power cylinder 8 from the hydraulic accumulator 10, i.e. turns off power cylinder 8 at that moment when power cylinder 7 is already

partially included. The power cylinder 7 of the friction element is then connected to the hydraulic accumulator 10. The hydraulic accumulator is discharged again. Similarly, the remaining switchings are performed.

The gearshift process depends on the throttle bore 3, which is determined by the position of the pedal 25 of the engine fuel supply.

The change in pressure at the inlet to the power cylinders during a gear shift for the case when the flow area in throttle 3 is fully open is shown in FIG. 2a At the beginning of the switch when / ti begins to fill, for example, the ram 7. The filling continues from 4 to 4 (see section line AB). At the end of the filling, the pressure of the working fluid in the actuated ram 7 quickly increases (see section LINE B – B), i.e., the engaging clutch begins to transmit a torque.

The discharge period of the hydraulic accumulator corresponds to the section GD. At t tz

valves 11 are actuated, and the hydroaccumulator is switched from the switched cylinder to the switched cylinder. The pressure in the power cylinder off quickly decreases (see the section of the line D-E). The pressure in the included power cylinder continues to increase (see the section of the line BF), but more slowly than in the section B – B, since this causes the discharging of the hydraulic accumulator. The pressure in the section GD is enough for

ensuring tractor movement without reducing speed when working with maximum loads. In section В-Ж there is a change in the speed of the tractor, respectively, of the gear to be engaged. When working with large loads, it flows quite smoothly.

FIG. 26 shows the graphs of the pressure change of the working fluid when shifting gears with a reduced flow area.

throttle 3. Throttling of the discharge line leads to a decrease in oil consumption when filling the included power cylinder. Therefore, the time interval ti-1-2 more than. Accordingly, uveakkumultora 10. Subsequent charging of the hydraulic accumulator (see section of line BF) proceeds slowly, as the oil supply to the hydraulic accumulator is reduced due to throttling of the discharge line by the throttle 3. The pressure of the fluid at the inlet to the actuated cylinder 7 at the start of charging the hydraulic accumulator 10 (point B) is smaller than in FIG. 2a (point B) due to a more complete discharge of the hydraulic accumulator, as well as due to a decrease in the pressure difference in the line between points L and B. The decrease in the pressure difference between the a b points is explained by a decrease in the charge for the hydraulic accumulator Torah.

Reducing the initial pressure (point B) and slowing down the filling of the hydraulic accumulator provides a smooth increase in the torque transmitted by the friction clutch. The first switching option (with an open throttle) is advisable to use when operating the tractor with large loads, for example, on tillage.

When driving without a load on a hook (or with a small load), the second switching option (with a closed throttle) is used without causing excessive slip of the clutches, which allows to increase the switching smoothness due to a smoother change in pressure of the working fluid in the power cylinders of the friction clutches.

Subject matter

A hydraulic device for controlling the friction gear elements of speed gearboxes of self-propelled machines, mainly tractors, according to the author. St. 225713, characterized in that, in order to smooth out the switching of the friction elements at partial engine loads, a controlled throttle connected to the engine load sensor is installed in the channel, which selects the selector mechanism with the source of supply of working fluid pressure.

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