KR100504419B1 - Emergency hydraulic control for adjusting a constant clamping force ratio with regard to a continuously variable tranmission - Google Patents

Abstract

The present invention relates to an emergency hydraulic control device that adjusts a constant clamping force ratio for continuously variable transmissions, wherein the throttle valve supplies an open hydraulic pressure to supply the piston chambers 17 and 13 corresponding to the first and second axis adjustments, respectively. It is characterized in that it is mounted on the circuit. To control both first and second pressures, first and second valves 20 and 50 are used respectively, each of which is actuated through an electromagnetically controlled regulating valve 70 and 50 which opens in an emergency, and a regulating valve. Is connected via a diaphragm valve to the outlet of the second valve 60. The pressure level in the pressure means of the first piston is also limited by the pressure limiting valves 30, 30 ′. The outlet of the pressure limiting valves 30, 30 ′ is connected via a control line 24 to a control line arranged between the first regulating valve 50 and the second valve, the diaphragm valve 31 being a pressure limiting valve. It is mounted between the opening of the control line disposed at the outlet of 30 and 30 'and the leading end from the control valve 23 to the control line, the induction of the control line 23 from the inlet line to the first side control valve. Extend. The emergency hydraulic control unit guarantees a constant clamping force ratio even at low pumping forces and speeds. This prevents the shift ratio towards the overdrive at the start of the vehicle and allows the shift ratio to be adjusted towards "low" at the second departure.

Description

Emergency hydraulic control for adjusting a constant clamping force ratio with regard to a continuously variable tranmission}

The present invention relates to an emergency hydraulic control device according to the preamble of the independent claim.

Similar emergency hydraulic control devices are known from the unpublished German patent application DE 196 09 785 for CVT, which are electronically controlled. The CVT transmission, which is described therein, in particular in motor vehicles, has a control for emergency drive operation, which usually has a high shift in order to create desirable restart and start conditions in the event of failure of the electrical control device of the drive operation. Shift in proportions. In this control, the ratio of primary clamping force to secondary clamping force, in particular between the tensioning device and the conical plate pairs, remains constant over the intermediate shift range. In the intermediate shift range, the shift changes as required for the rotational moment of the output shaft. When a high rotational moment is required, a high shift is selected that allows starting in that state, while a low shift is set when a low rotational moment is required, for example when a propulsion moment appears. Means necessary for this are presented in the description of FIGS. 1 and 2.

1 is a hydraulic circuit diagram for adjusting a preselected clamping force ratio.

2 is a diagram of the clamping force ratio.

3 is a hydraulic circuit diagram with a throttle valve in a control line extending towards the primary valve, as in FIG.

4 is a hydraulic circuit diagram with two other diaphragm valves, as in FIG.

In the present invention, an emergency hydraulic control device is required to enable the continuously variable transmission to be used over the entire transmission range without the support of an active electro-hydraulic control device in normal driving operation. By means of the emergency hydraulic control device, a low range starting shift is set at the start of the vehicle, so that starting from a mountain or from a garage, for example, is possible. Similarly, at high travel speeds and low engine rotation moments, the emergency control must be set to shift in the "Overdrive" range. It is important here that the shift ratio does not drop completely to the "Overdrive" range during propulsion, for example during braking of the vehicle, and in the "low" direction immediately after a rapid increase in the speed of the vehicle engine with a new start or acceleration. Is controlled by.

In the emergency hydraulic control device of the present invention, the clamping force ratio is changed depending on the pump volume flow or the engine speed supplied. For that purpose, the open hydraulic circuit is equipped with at least one throttle valve to supply pressure to the respective piston spaces of the secondary and primary axial adjustments. The change in pressure with the volume flow regulated in the throttle valve changes the compressive force in the corresponding pair of cone plates-supported by other valves. Primary and secondary valves are used respectively for the adjustment of the primary and secondary pressures. Each valve is again controlled via a preliminary regulating valve which opens the electromagnetically actuated preliminary regulating valve in an emergency run operation, wherein the preliminary regulating valves are connected via the diaphragm valves, in particular to the outlet of the secondary valve. The pressure of the pressure medium in the primary piston space is further restricted via the primary pressure limiting valve. The outlet of this pressure limiting valve is connected via a control line with a control line lying between the primary preliminary control valve and the primary valve. At the same time, a diaphragm valve is provided between the point where the control line installed at the outlet of the pressure limiting valve merges into the control line exiting the control valve and the point at which the control line branches from the supply line toward the primary preliminary control valve.

This hydraulic circuit is particularly suitable for short engine speeds in which the limiting pressure of the primary pressure limiting valve is exceeded in propulsion operation, i.e. when the shift ratio moves in the "overdrive" direction, during an emergency driving operation by primary pressure rise. When increasing, it reacts. As a result, the pressure medium clogged for a short time in the control line between the diaphragm valve and the control inlet of the primary valve moves the primary valve to a return position where the pressure in the primary piston space escapes into the tank. Therefore, the shift of the continuously variable transmission is increased, thereby enabling new acceleration of the vehicle.

Other details of the invention are set forth in the dependent claims and the description of the drawings.

Embodiments of the present invention are shown in the form of hydraulic circuit diagrams in the drawings together with the prior art, and will be described in more detail with reference to the diagrams shown simplified and idealized in the following description of the drawings.

1 shows a cross section corresponding to the prior art in a hydraulic circuit diagram for hydraulic control of a drive side and an output side pressure cylinder of a continuously variable transmission. Known continuously variable transmission 10 comprises two pairs of conical plates, between which are arranged a transmission device 14, for example a propulsion link conveyor, a chain, a V-belt or the like. The two pairs of conical plates each consist of two conical plates 11, 12; 15 and 16, which are formed so as to be able to withstand each other hydraulically. The piston- and cylinder parts necessary for that are in particular integrated in at least part of the conical plate. The piston spaces surrounded by these parts are on the primary side of the piston space 13 and on the secondary side of the piston space 17. These spaces are provided with the necessary working pressure for it according to the adjustment of the shift. The primary pair of cone plates is, for example, driven by a vehicle engine, while the secondary pair of cone plates acts on the drive train of the vehicle.

In order to provide the clamping force required for the plate pairs 11, 12 and 15, 16, for example, a hydrostatic pump 7 driven by a vehicle engine draws hydraulic oil into two piston spaces 13 and 17. And the output side secondary pressure required in the embodiments described herein is greater than or equal to the required drive side primary pressure.

The pressure medium is supplied to the secondary piston space 17 via the operation line 102 and the secondary line 103 without intermediate connection of the valve. The secondary pressure is controlled by the secondary valve 60 and the additional valve 70. There is an operating line 111 between two valves 60 and 70. The diaphragm valve 77 is provided in front of the additional valve 70 in the operation line 111.

The secondary valve 60 is a pressure limiting valve that is remotely controlled. The additional valve 70 is an electromagnetically actuated pressure limiting valve, the outlet of which is configured to release pressure into the tank. The control line 71 of the additional valve 70 branches behind the diaphragm valve 77. It is further connected to a hydraulic accumulator 75.

The primary hydraulic pressure in the piston space 13 is regulated by a 3 / 3-constant valve 20. The primary valve 20, which is supplied pressure from the secondary operating line 103 via the operating line 104, is connected to the piston chamber 13 via the primary pressure line 105. The primary valve 20 has a control terminal 25 on the left side and a mechanical return spring 21 on the right side. A throttle valve 29 is placed in the operation line 104 extending to the inlet connection of the valve 20. The actuation line 106 branches from the primary pressure line 105. Operation line 106 extends into transmission lubricant line 121 via two pressure limiting valves 30 and 40. Into the actuation line 106, a return line 107 connected to the outlet of the primary valve 20 extends. Between this confluence point and the branch point of the return line 106 from the primary pressure line 105 lies a pressure limiting valve 30. The actuation line 106 intersects the actuation line 111 between the return line 107 and the pressure limiting valve 40.

The operation line 112 branches from the operation line 111. The actuation line extends from the electromagnetically actuated pressure limiting valve 50 to the tank. The pressure limiting valve 50 is an additional valve for the primary valve 20. The diaphragm valve 57 is provided in front of the valve 50. The control line 51 branches between the diaphragm valve 57 and the inflow connection of the additional valve 50, to which a hydraulic accumulator 55 is connected. The control line 23 extending to the control terminal 25 of the primary valve 20 is connected to the branching region.

A tank return line 125 is provided between the transmission lubricant line 121 and the tank. It passes, for example, into the operation line 101 in front of the pump 7. The tank return line 125 has a lubrication pressure valve 80. It is formed as a pressure limiting valve, which limits the lubrication pressure upwards.

In the event of failure of the control electronics, the electromagnets of the preliminary control valves 50 and 70 are no longer supplied with current. The preliminary adjustment valves 50 and 70 are opened. Pressure decreases in control lines 62 and 23. As a result, the secondary valve 60 sets the maximum limit pressure, while the primary valve 20 moves to the switching position 3. In the actuation line 106 the valve 30 opens upon exceeding a preset maximum primary pressure. The pressure medium is operated from the secondary line 103 to the operation line 104, the throttle valve 29, the primary valve 20, the primary pressure line 105, the primary pressure limiting valve 30, the pressure limiting valve ( Flowing through operation line 106 to 40, pressure medium is used for control of additional valves 50 and 70.

When the limiting pressures of the valves 60 and 30 are constant, the piston spaces 13 and 17 are set with a constant clamping force ratio Kp / Ks.

FIG. 2 includes a diagram showing the ratio of the clamping force Kp of the primary cylinder and the clamping force Ks of the secondary cylinder to the transmission ratio i of the transmission. The diagram shows the speed ratio ascending to the right. The maximum speed ratio, marked "low", is generally selected for the start of the vehicle, while the minimum speed ratio, marked "overdrive", corresponds to the longest course. Upper curve 1 over the full speed range dictates the ratio of clamping force required for rotational moment transfer in full load operation. Similarly, lower curve 2 over the entire shift range represents the clamping force ratio for the moment of rotation to be transmitted at approximately zero.

In FIG. 1, the clamping force ratio Kp / Ks adjusted according to the hydraulic circuit corresponds approximately to the center, horizontal line 3 in FIG. This makes it possible, for example, to adjust the shift between nearly "low" at start and almost "overdrive" at high speed propulsion operations, for example.

In Fig. 1, the hydraulic circuit has the disadvantage that it can manifest itself, especially at low engine speeds, at the start. If the valve 30 is opened after reaching a pre-determined primary limiting pressure, in some cases the entire volumetric flow transferred by the pump 1 will not cause the throttle valve 29 to open without the secondary valve 60 being opened. ), The primary valve 20 and the primary pressure limiting valve 30 are guided to the pressure limiting valve 40. Therefore, the clamping force ratio is determined by the pressure drop in the throttle valve 29 and the limiting pressure of the valve 30. As the secondary pressure drops, the clamping force ratio Kp / Ks increases. In other words, line 3 is moved in the direction of line 5. In line 5, the transmission shift is regulated in propulsion after "overdrive" and the shift in the "low" direction, known as a drawback at full load, is only minimal.

In order to ensure a constant clamping force ratio even at low revolutions of the vehicle engine, the outlet of the primary pressure limiting valve 30 ′ in the hydraulic circuit diagram according to FIG. 3 passes through the control line 24 to the primary preliminary regulating valve 50. It is connected to the control line 23 extending to. The control line 23 is provided with a diaphragm valve 31 between the confluence point of the control line 24 and the preliminary control valve 50. In addition, the return connection of the primary valve 20 is connected with the tank.

If the primary pressure exceeds the limiting pressure of the valve 30 'in the emergency run operation, the pressure medium flows into the tank via the pressure limiting valve 50 opened from the primary line 105. The pressure medium passes through a control line 106 ', a valve 30', a control line 24 and a control line 23 equipped with a diaphragm valve 31.

When the primary pressure limiting valve 30 'is sufficiently open and the pressure in the line 23 and the line 24 between the diaphragm valve 31 and the primary valve 20 rises in front of the diaphragm valve 31, 1 The slide of the difference valve 20 is moved to the switching position 1 against the force of the return spring 21. This causes the pressure of the primary pressure line 105 to escape directly into the tank. The pressure of the primary piston space 13 drops. The distance between the conical plates 11 and 12 becomes large. The transmission ratio of the transmission is adjusted in the direction of "low".

In the hydraulic circuit diagram according to FIG. 3, only a small pressure medium volume flow flows from the secondary line 103 through the throttle valve 29 and the primary valve 20 to the primary pressure line 105. 60 is already open even at small pump delivery rates or at low rotational speeds of the vehicle engine. Thus, a constant clamping force ratio K _p / K _s over a wide range of rotational speeds is implemented corresponding to horizontal line 3 of the K _p / K _s -diagram of FIG. 2.

Since only one small pressure medium volume flow here flows through the pressure limiting valve 30 ′, the valve can be designed smaller than the pressure limiting valve 30 of FIG. 1, which makes the emergency hydraulic control device more compact. It requires a small footprint.

To control the control pressure generated in the primary valve 20, one or two other throttle valves between the control terminal 25 and the confluence point of the control line 24 in lines 106 ′ and control line 23. Or diaphragm valves 32, 33 are provided (see FIG. 4). Diaphragm valve 32 in line 106 'is positioned before the valve-specific control line of primary pressure limiting valve 30'.

Claims (9)

As an emergency hydraulic control device for varying the hydraulic pressure in accordance with the shift in the first and second hydraulic cone plate axial adjustment of the continuously variable transmission 10, There is a pump 7 which directly supplies hydraulic pressure to the piston space 17 of at least a second axial adjustment, -There is at least one secondary valve (60) which limits the hydraulic pressure there, There is an electromagnetically actuated pressure limiting valve 70 connected behind the secondary valve 60 and remotely controlling it, the supply line of the valve 70 being equipped with a diaphragm valve 77 and a diaphragm valve 77 Behind) branched control line 62 for remote control of secondary valve 60, There is a constant direction valve 20 which is supplied from the supply line of the piston space 17, via which a pressure medium is supplied to the piston space 13 of the first axial adjustment, There is a throttle valve 29 mounted between the supply line of the piston space 17 and the constant direction valve 20, There is an electromagnetically actuated pressure limiting valve 50 connected behind the secondary valve 60 and hydraulically controlling the constant direction valve 20, wherein a diaphragm valve 57 is provided in the supply line of the valve 50. And a control line 23 branches behind the diaphragm valve 57 to control the constant direction valve 20, In an emergency hydraulic control device, there is a pressure limiting valve (30, 30 ') that limits the pressure in the supply line of the piston space (13), The outlet of the valve 30 'is connected to the control line 23 via the control line 24, A diaphragm valve 31 is provided between the point of confluence into the control line 23 of the control line 24 and the point where the control line 23 branches from the supply line 112 toward the pressure limiting valve 50. Emergency hydraulic control device, characterized in that. 2. The valve according to claim 1, wherein the constant direction valve 20 is a 3 / 3-way valve, the slide of which is fixed between the return spring 21 and the hydraulic actuating part with the control terminal 25, and the blocking intermediate position. Emergency hydraulic control device having a. 2. The emergency hydraulic control apparatus according to claim 1, wherein the pressure limiting valves (50 and 70) are opened in a state in which no current flows. 2. The emergency hydraulic control apparatus according to claim 1, wherein a hydraulic accumulator (55, 75) is connected to each control line (51, 71) of the pressure limiting valve (50, 70). 2. The emergency hydraulic control device according to claim 1, wherein the pressure of the pressure medium in the supply line to the pressure limiting valves (50 and 70) is limited by the auxiliary pressure valve (40). 6. The pressure limiting valve (80) is connected behind the auxiliary pressure valve (40) as a lubrication pressure valve, the lubricant line (121) branching before its inlet, and its pressure being introduced into the tank through the outlet. Emergency hydraulic control device, characterized in that the exit or supplied to the suction connection of the pump (7). 2. The emergency hydraulic control device according to claim 1, wherein the spring rate can be mechanically or electrically adjusted by at least part of the return spring of the spring loaded valves 20, 30, 40, 60, 80. . 2. The emergency hydraulic control apparatus according to claim 1, wherein at least one diaphragm valve (32) is in the actuation line (106 '). 2. The emergency hydraulic control device according to claim 1, characterized in that at least one diaphragm valve (33) is provided at the control line (23) between the confluence point of the control line (24) and the control terminal (25).