JP2012031955A - Hydraulic control device for automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic control device for an automatic transmission that can improve the responsiveness and controllability of the automatic transmission while maintaining the operating efficiency thereof.SOLUTION: The hydraulic control device for an automatic transmission 1 includes: a hydraulic pressure chamber 5 which hydraulic pressure is supplied to and exhausted from, and is coupled with a rotator 4; a hydraulic pressure supply valve 7 for supplying hydraulic pressure to the hydraulic pressure chamber 5 from a hydraulic pressure source 11; a hydraulic pressure exhaust valve 8 for exhausting hydraulic pressure therefrom; and a hydraulic pressure circulation path 9 extending from the hydraulic pressure source 11 to the hydraulic pressure chamber 5, and which is configured to be firmly sealed from an external air while the hydraulic pressure exhaust valve 8 is closed. The hydraulic control device is provided with: an oil path provided along the rotational center of the hydraulic pressure chamber 5, and for supplying and exhausting hydraulic pressure to and from the hydraulic pressure chamber 5; an exhaust passage 9a communicated with the oil path 6 and provided above the axial center of the oil path 6 for air vent; and an air vent 12 for exhausting the air in hydraulic pressure from the exhaust passage 9a to the outside.

Description

  The present invention relates to a device for controlling oil pressure in an automatic transmission in which a gear ratio and transmission torque capacity change according to oil pressure, and more particularly to a hydraulic control device including a pressure increasing means for increasing the oil pressure and a pressure reducing means for reducing the pressure. Is.

  Conventionally, hydraulic pressure is used to change the gear ratio of an automatic transmission. For example, in the case of a stepped automatic transmission, a clutch is used to transmit torque by a gear train having a required gear ratio, and the hydraulic pressure provided in the clutch to obtain the engagement pressure of the clutch. The clutch piston is driven by supplying or discharging pressure oil to or from the chamber and changing the hydraulic pressure in the hydraulic chamber. The continuously variable automatic transmission is composed of an input rotation member, an output rotation member, and a power transmission member sandwiched between them, so as to obtain a clamping pressure for clamping the power transmission member or change a gear ratio. For this purpose, the pressure oil is supplied to or discharged from a hydraulic chamber provided in one or both of the input rotation member and the output rotation member, and the clamping pressure and the gear ratio are changed.

  Examples of the continuously variable transmission are described in Patent Documents 1 to 3. The inventions described in Patent Documents 1 to 3 relate to a belt-type continuously variable transmission, and include a pulley of an input rotation member, a pulley of an output rotation member, and a belt of a power transmission member. Each pulley is composed of a movable sheave and a fixed sheave. The movable sheave is provided with a hydraulic chamber. By supplying pressure oil to the hydraulic chamber, the movable sheave is moved toward the fixed sheave. By changing the wrapping radius for wrapping the belt and changing the gear ratio, or by changing the pressure oil in the hydraulic chamber of the movable sheave, the clamping pressure for clamping the belt between the pulleys is changed. In the apparatuses described in Patent Documents 1 and 2, each hydraulic chamber is provided with means for increasing the hydraulic pressure and means for reducing the pressure.

European Patent No. 0985855 International Publication No. 2010/021218 Pamphlet JP 07-98049 A

  In the devices described in Patent Documents 1 and 2 described above, the hydraulic path from the hydraulic source to the hydraulic chamber has a so-called hermetic structure including a valve interposed therein, and hydraulic pressure does not leak outside. It is configured as follows. Therefore, when the hydraulic pressure in the hydraulic chamber is increased, the target hydraulic pressure in the hydraulic chamber is supplied from the pressure increasing means, so that the hydraulic pressure corresponding to the supplied pressure oil can be obtained. Alternatively, the hydraulic pressure in the hydraulic chamber can be kept constant without operating the pressure increasing means. However, in the structure in which the valve and the oil passage are sealed, if air is mixed in the pressurized oil, the air is compressed when pressurized, so that the assumed hydraulic pressure may not be obtained. Alternatively, the hydraulic pressure is excessively increased to ensure a predetermined hydraulic pressure. As a result, the responsiveness and controllability as an automatic transmission may be reduced.

  Moreover, in the apparatus described in Patent Document 3, a bleed hole is formed in a part of the oil passage. Therefore, since air is discharged to the outside together with the pressure oil from the bleed hole, the amount of air mixed in the hydraulic chamber can be reduced. However, since the pressure oil is discharged at the same time as the air is discharged, the pressure increasing means is operated at any time in order to maintain or increase the hydraulic pressure, and the frequency of pressure increase as an automatic transmission increases, and the operating efficiency is increased. There is a possibility of reduction.

  The present invention has been made paying attention to the above technical problem, and provides a hydraulic control device for an automatic transmission capable of improving the response and controllability while maintaining the operation efficiency of the automatic transmission. It is for the purpose.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a hydraulic supply valve and a pressure oil, wherein a hydraulic chamber to which hydraulic pressure is supplied and discharged is connected to a rotating body, and pressure oil is supplied to the hydraulic chamber from a hydraulic source. A hydraulic control device for an automatic transmission, wherein a hydraulic circuit extending from the hydraulic source to the hydraulic chamber is sealed against outside air when the hydraulic discharge valve is closed. An oil passage for supplying or discharging pressure oil to the hydraulic chamber along the rotation center of the hydraulic chamber is provided, and a discharge passage for venting air communicating with the oil passage and extending above the axis is provided. An air venting means for discharging the air in the pressure oil from the discharge path to the outside is provided.

  According to a second aspect of the present invention, in the first aspect of the present invention, the actual hydraulic pressure change calculating means for calculating the hydraulic pressure change in the hydraulic chamber, the differential pressure between the input side and the output side of the hydraulic pressure supply valve, and the hydraulic pressure supply Estimated oil pressure change calculating means for estimating a change in oil pressure in the hydraulic chamber based on the opening of the opening provided in the valve, oil pressure change calculated by the actual oil pressure change calculating means, and the estimated oil pressure change calculating means And a hydraulic pressure change comparing means for comparing with the hydraulic pressure change calculated in the step, and when there is a difference in the hydraulic pressure by the hydraulic pressure change comparing means, the air in the pressure oil is discharged by the air bleeding means. A hydraulic control device for an automatic transmission characterized by being configured.

  According to a third aspect of the present invention, in the second aspect of the invention, the hydraulic oil is mixed into the pressure oil based on the difference between the hydraulic pressure change calculated by the actual hydraulic pressure change calculating means and the hydraulic pressure change calculated by the estimated hydraulic pressure change calculating means. Hydraulic control for an automatic transmission further comprising means for calculating an air amount, and means for calculating a time for discharging the air in the pressure oil by the air venting means according to the air amount Device.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, when the pressure oil in the hydraulic chamber is discharged by the hydraulic pressure discharge means, the air in the pressure oil is discharged by the air bleeding means. The hydraulic control apparatus for an automatic transmission is configured as described above.

  According to the first aspect of the present invention, the oil passage for supplying and discharging the pressure oil is formed in the axial center of the hydraulic chamber connected to the rotating body. Air mixed in the pressure oil in the room gathers near the shaft center due to the density difference. Therefore, air or pressurized oil containing a large amount of air can be effectively discharged from the oil passage connected to the hydraulic chamber to the outside of the hydraulic chamber. In addition, a discharge passage for releasing air is formed above the axis of the oil passage, and air release means for discharging the air in the pressure oil from the discharge passage to the outside is provided. Therefore, since the discharge path is formed at a location where the air flowing out from the oil path to the hydraulic circuit is likely to gather, the air can be efficiently discharged to the outside of the hydraulic control device.

  According to the second aspect of the present invention, the actual hydraulic pressure change in the hydraulic chamber is compared with the estimated hydraulic pressure change calculated based on the differential pressure before and after the hydraulic pressure supply valve and the opening of the output section. When there is a difference in oil pressure change, the air in the pressure oil is exhausted to the outside by the air venting means. Can be estimated. Further, it is possible to suppress the decrease in the responsiveness of the hydraulic control by estimating that air is mixed and discharging the air.

  Further, according to the invention of claim 3, the amount of air mixed into the hydraulic chamber is calculated from the difference between the actual change in hydraulic pressure and the estimated change in hydraulic pressure, and the air is released outside by the air venting means according to the amount of air. Since the discharge operation time is calculated, the amount of pressure oil that inevitably flows out simultaneously with air can be reduced. Further, when the air venting means is electrically controlled, power consumption for operating the air venting means can be reduced.

  And according to invention of Claim 4, when discharging | emitting the pressure oil of a hydraulic chamber by a hydraulic discharge means, since air is discharged | emitted by an air venting means, the flow of the pressure oil accompanying the pressure reduction of the hydraulic chamber can be utilized, Air can be discharged efficiently.

It is the schematic which shows the hydraulic control apparatus of the automatic transmission which concerns on this invention. It is a graph which shows the difference in the outflow amount of the pressure oil of the hydraulic control apparatus which concerns on this invention, and the conventional hydraulic control apparatus. It is a graph which shows the pressure responsiveness by the difference in the air mixing amount of pressure oil. It is a flowchart for demonstrating the 1st example of control by the hydraulic control apparatus of the automatic transmission which concerns on this invention. It is a flowchart for demonstrating the 2nd control example. FIG. 10 is a flowchart for explaining a third control example.

  The present invention relates to a hydraulic control device for an automatic transmission that changes a gear ratio, a transmission torque capacity, and the like by a change in pressure in a hydraulic chamber, and in particular, its oil passage or hydraulic circuit is cut off from the outside (outside air) or The present invention relates to a hydraulic control device for a sealed automatic transmission. An example of the configuration is shown in FIG. An automatic transmission 1 shown in FIG. 1 is a so-called belt-type continuously variable transmission comprising an input-side pulley 2, an output-side pulley 3, and a belt 4 wound around these pulleys 2 and 3 to transmit power. 1. Since these pulleys 2 and 3 have substantially the same configuration, FIG. 1 shows one pulley (input-side pulley 2). These pulleys 2 and 3 are composed of fixed sheaves 2a and 3a fixed in the axial direction and movable sheaves 2b and 3b movable in the axial direction. A hydraulic chamber 5 is formed on the so-called back side of the movable sheave 2b, and the movable sheave 2b is moved to change the gear ratio by increasing or decreasing the hydraulic pressure in the hydraulic chamber 5, or the belt 4 Is changed between the sheaves 2a and 2b (3a and 3b).

  The hydraulic chamber 5 is configured to be supplied with pressure oil from an oil passage 6 formed along the axis of the pulley 2 through an opening 6 a communicating with the hydraulic chamber 5. The oil passage 6 is connected to a hydraulic circuit 9 communicating with the pressure increasing valve 7 and the pressure reducing valve 8. The pressure increasing valve 7 and the pressure reducing valve can be an electromagnetic valve that is electrically controlled to open and close. Hereinafter, the electromagnetic valve will be described as an example. That is, the hydraulic circuit 9 is branched and connected to an oil passage 7 a output from the pressure increasing valve 7 and an oil passage 8 a input to the pressure reducing valve 8. Therefore, when the hydraulic pressure in the hydraulic chamber 5 is increased, the pressure oil is supplied to the hydraulic chamber 5 by the oil pump 11 which is a hydraulic source from the oil pan 10 in which the pressure increasing valve 7 is opened and the oil is accumulated, and the pressure is reduced. When the pressure is reduced by closing the valve 8, the pressure increasing valve 7 is closed and the pressure reducing valve 8 is opened to discharge the pressure oil in the hydraulic chamber 5. Each of these valves 7 and 8 is configured to have almost no leakage when the ports 7b and 8b are closed. That is, when one port 7b, 8b of each valve 7, 8 is closed, the pressure oil in the hydraulic circuit 9 does not flow out. FIG. 2 shows the difference in the amount of pressure oil flowing out between the hydraulic control device according to the present invention and the conventional hydraulic control device, particularly the spool valve hydraulic control device, and the solid line represents the hydraulic control device according to the present invention, The broken line shows the outflow amount of the conventional hydraulic control device. Accordingly, the entire hydraulic circuit including the hydraulic chamber 5 is configured so that pressure oil does not flow out. Further, each of the valves 7 and 8 shown in FIG. 1 is configured to open the port when energized, and the opening degree of the port changes according to the current.

  The hydraulic circuit 9 branches off at the same height as the axis of the pulley 2 in a normal use state or at a position higher than the axis. The branched hydraulic circuit 9a is connected to an air vent valve 12 for discharging air mixed in the pressure oil. The air vent valve 12 may be an electromagnetic valve that is electrically controlled to open and close, or may be a hydraulically driven valve that opens and closes by controlling other oil pressure. In the following description, an electromagnetic valve that is electrically controlled to open and close will be described as an example. That is, a so-called poppet valve that seals the opening by pressing a valve body connected to a magnetic body that obtains a driving force by electromagnetic force against a valve seat that is the opening is an example. Therefore, when the valves 7, 8, and 12 are closed, the pressure oil is not discharged to the outside (outside air), and the hydraulic pressure in the hydraulic chamber 5 can be maintained. On the other hand, when air is mixed in the pressure oil, the air vent valve 12 is opened to discharge the air. Further, the diameter of the opening 12b of the air bleeding valve 12 is set smaller than that of the opening 7b of the pressure increasing valve 7 so that the pressure can be adjusted even when the air bleeding valve 12 is opened when the pressure is increased. To do.

  By configuring the hydraulic circuit including the oil passage 6 formed in the pulley 2 as described above, the air in the pressure oil can be effectively discharged. Specifically, since the oil passage 6 formed in the pulley 2 rotates integrally with the pulley 2, the air in the hydraulic chamber 5 gathers in the vicinity of the rotation center due to the density difference from the pressure oil, and the air is oil It passes through the path 6 and flows to the hydraulic circuit 9. Since the hydraulic circuit 9 does not rotate, the air gathers upward and is supplied to the air vent valve 12 via the branched hydraulic circuit 9a. Therefore, by opening the air vent valve 12, air or pressurized oil containing a large amount of air can be discharged to the outside (outside air), so that the amount of air in the hydraulic chamber 5 is effectively reduced. be able to. As a result, the pressure responsiveness is improved as shown in FIG. 3, so that the slippage of the belt 4 can be suppressed or prevented. In addition, the solid line shown in FIG. 5 is the pressure oil in which air is not mixed, the one-dot chain line is the pressure oil in which a small amount of air is mixed, and the two-dot chain line is the pressure oil in which a large amount of air is mixed. Further, when it is determined that air is mixed in the pressure oil, the air vent valve 12 can be appropriately opened, so that the oil pump is not required or always discharged without discharging the pressure oil. 11 and the pressure booster 7 can be driven less frequently, and as a result, the fuel consumption of the entire vehicle can be reduced.

  Next, control of the air vent valve 12 will be described. FIG. 4 is a flowchart for explaining the first control example. This first control example is executed by an electronic control unit (ECU) (not shown) that controls the automatic transmission 1 shown in FIG. 1, and there is a possibility that air is mixed in or mixed in the hydraulic chamber 5. If it is determined whether or not there is an affirmative determination, the air vent valve 12 is operated to discharge air. Specifically, first, the actual hydraulic pressure in the hydraulic chamber 5 is detected or calculated (step S11). This detection and calculation is performed every predetermined time, and p (n−1) shown in step S11 is the hydraulic pressure detected immediately before p (n) shown in step S11. Then, a differential pressure is calculated from each hydraulic pressure detected in step S11 (step S12). That is, the actual hydraulic pressure change amount Δp of the hydraulic chamber 5 is calculated. Next, a predicted flow rate Q is calculated from a flow rate equation of an orifice (not shown) provided in the pressure increasing valve 7 (step S13). In the equation shown in step S13, C is the outflow coefficient, Φ (x) is the opening area of the orifice, Pin is the hydraulic pressure flowing into the orifice, Pout is the hydraulic pressure flowing out from the orifice, and ρ is the density of the pressure oil. Then, the estimated hydraulic pressure change amount ΔP is calculated based on the predicted flow rate Q calculated in step S13 (step S14). Specifically, the estimated hydraulic pressure change ΔP is calculated from the product of the predicted flow rate Q and the hydraulic rigidity α. Then, it is determined whether or not the hydraulic pressure change amount Δp calculated in step S12 is smaller than the estimated hydraulic pressure change amount ΔP calculated in step S14 (step S15). If a negative determination is made in step S15, that is, if the actual oil pressure change amount Δp is greater than or equal to the estimated oil pressure change amount ΔP, this control is once terminated. On the other hand, if a positive determination is made, a current is supplied to the air vent valve 12 (step S16). That is, the air vent valve 12 is opened. And it returns to step S11 and controls again according to the flowchart mentioned above. That is, this control is repeatedly executed until a negative determination is made in step S15, in other words, until the actual oil pressure change amount Δp becomes equal to or greater than the estimated oil pressure change amount ΔP.

  When the actual change amount Δp of the hydraulic chamber 5 is compared with the estimated change amount ΔP, and the actual change amount Δp of the actual hydraulic pressure is smaller than the estimated change amount ΔP of the hydraulic pressure, the pressure chamber 5 or the hydraulic chamber 5 There may be air inside. Therefore, in the above-described control example, when the actual change amount Δp of the hydraulic pressure is smaller than the estimated change amount ΔP of the hydraulic pressure, it is determined that air is mixed in the pressure oil or the hydraulic chamber 5 and the air removal is performed. The valve 12 is opened.

  By performing the above-described control, the amount of air mixed when there is a possibility that a large amount of air is mixed in the hydraulic chamber 5 due to the fact that the vehicle has not been operated for a long period of time, or the air while the vehicle is running Since the air can be appropriately discharged by the air vent valve 12 to the outside of the hydraulic chamber 5 (outside air), slippage of the belt 4 due to a delay in the hydraulic response of the hydraulic chamber 5 can be prevented. Can be prevented. Furthermore, since the hydraulic controllability can be improved, the optimum hydraulic pressure can be set with high accuracy, and as a result, the control efficiency can be improved and the fuel consumption of the vehicle can be improved. In the above-described control, the air pressure change amount ΔP is calculated from the hydraulic pressure of the pressure oil passing through the orifice to estimate the air mixing amount. Therefore, it is not necessary to provide an air amount measuring sensor, and the weight and cost can be reduced. Can be planned.

  Next, a second control example improved from the above-described control example will be described. In the first control example described above, the actual oil pressure change amount Δp is compared with the estimated oil pressure change amount ΔP, and the actual oil pressure change amount Δp is smaller than the estimated oil pressure change amount ΔP. The valve 12 is opened. The second control example, which is an improvement of the first control example, further calculates the valve opening time of the air bleeding valve 12. FIG. 5 shows a flowchart for explaining the second control example. In the flowchart shown in FIG. 5, steps S21 to S24 are the same as steps S11 to S14 in the first control example described above, and thus description thereof is omitted. Hereinafter, the control from step S25 will be described.

  It is determined whether or not a value obtained by subtracting the estimated hydraulic pressure change ΔP calculated in step S24 from the actual hydraulic pressure change Δp calculated in step S22 is a negative value (step S25). This determination is similar to step S15 in the first control example described above, and it is determined whether or not the actual oil pressure change amount Δp is smaller than the estimated oil pressure change amount ΔP. If a negative determination is made in step S25, that is, if the actual oil pressure change amount Δp is greater than or equal to the estimated oil pressure change amount ΔP, this control is terminated as it is. On the contrary, if a positive determination is made, the pressure oil is mixed from the deviation between the actual oil pressure change amount Δp and the estimated oil pressure change amount ΔP and a map prepared in advance by experiment or design. The air amount V is derived (step S26). Then, a time Δt for energizing the air vent valve 12 is calculated from the air amount V derived in step S26 and the predicted flow rate Q calculated in step S23 (step S27). Specifically, a value (energization time Δt) obtained by dividing the air amount V derived in step S26 by the predicted flow rate Q calculated in step S23 is calculated. Then, the air vent valve 12 is energized for the energization time Δt calculated in step S27 (step S28), and this control is temporarily terminated.

  In the second control example described above, since the time Δt for energizing the air vent valve 12 can be calculated in addition to the first control example, in addition to the effect of the first control example, the air vent valve The working time of 12 can be reduced. Therefore, power consumption stored in the vehicle can be reduced. Furthermore, since excessive outflow of pressure oil can be reduced, the efficiency of the hydraulic control device and the fuel consumption of the vehicle can be improved.

  Furthermore, another control example will be described. FIG. 6 is a flowchart for explaining another control example (third control example). In this third control example, when the volume change of the hydraulic chamber 5 occurs due to a shift, the air vent valve 12 is opened simultaneously with the volume change to discharge air to the outside. This will be specifically described below.

  First, Steps S31 to S35 in the third control example are the same as Steps S21 to S25 in the second control example described above, and thus description thereof is omitted. If a negative determination is made in step S35, this control is temporarily terminated as it is. On the other hand, if a positive determination is made, that is, if the difference between the actual oil pressure change amount Δp and the estimated oil pressure change amount ΔP is a negative value, it is determined whether there is an upshift command ( Step S36). This determination basically determines whether or not the volume of the hydraulic chamber 5 decreases due to a shift change. That is, it is determined whether there is a command for reducing the volume of the hydraulic chamber 5, that is, a command for reducing the hydraulic pressure. In other words, it is determined whether or not there is a command to open the pressure reducing valve 8. If a negative determination is made in step S36, the determination in step S36 is continued. Here, if a negative determination is made in step S36, the control in step S36 is continued again. However, this routine may be once ended and the process may be returned. On the other hand, if a positive determination is made, that is, in the example shown in the figure, if there is an upshift command, the air vent valve 12 is energized and opened, and this control is temporarily terminated.

  By reducing the volume of the hydraulic chamber 5 and opening the air vent valve 12 at the same time as in the third control example described above, the amount of pressure oil discharged from the pressure reducing valve 8 can be reduced. Control efficiency can be improved and fuel efficiency as a vehicle can be improved. Further, since air is easily pushed and discharged by the pressure oil pushed out due to the decrease in volume, the control response can be improved, and the time or frequency of opening the solenoid valves 8 and 12 can be reduced. The power consumption of the vehicle can be reduced.

  Each control example described above is repeatedly executed in an extremely short time. In each control example, each step of calculating the actual oil pressure change amount Δp and the estimated oil pressure change amount ΔP is not limited to the order described above. That is, the estimated oil pressure change amount ΔP may be calculated first, or may be calculated simultaneously with the actual oil pressure change amount Δp. Furthermore, each control example may be executed individually, or may be executed in parallel or simultaneously. Furthermore, the present invention is not limited to vehicles, and can be used for machines and devices in various fields such as ships, airplanes, and industrial machines. In each of the control examples described above, an air vent valve that is electrically controlled to open and close has been taken as an example. However, in short, it is sufficient that the air in the discharge path can be discharged to the outside. Thus, a hydraulic drive valve or the like may be used as the air bleeding means.

  DESCRIPTION OF SYMBOLS 1 ... Automatic transmission (belt type continuously variable transmission), 2 ... Pulley, 4 ... Belt, 5 ... Hydraulic chamber, 6 ... Oil passage, 7 ... Booster valve, 8 ... Pressure reducing valve, 9 ... Hydraulic circuit, 10 ... Oil Pan, 11 ... Oil pump, 12 ... Air venting valve.

Claims (4)

A hydraulic chamber to which hydraulic pressure is supplied and discharged is connected to the rotating body, and a hydraulic supply valve for supplying pressure oil from a hydraulic source and a hydraulic discharge valve for discharging pressure oil to the hydraulic chamber are provided. In the hydraulic control device of the automatic transmission, the hydraulic circuit leading to the hydraulic chamber is sealed against the outside air when the hydraulic discharge valve is closed,
An oil passage for supplying or discharging pressure oil to the hydraulic chamber is provided along the rotation center of the hydraulic chamber,
A discharge passage for venting air is provided which communicates with the oil passage and extends above the axis;
A hydraulic control device for an automatic transmission, characterized in that air venting means for discharging the air in the pressure oil to the outside from the discharge path is provided. An actual oil pressure change calculating means for calculating the oil pressure change in the oil pressure chamber;
Estimated hydraulic pressure change calculating means for estimating a change in hydraulic pressure in the hydraulic chamber based on a differential pressure between the input side and the output side of the hydraulic pressure supply valve and an opening of an opening provided in the hydraulic pressure supply valve;
A hydraulic pressure change comparing means for comparing the hydraulic pressure change calculated by the actual hydraulic pressure change calculating means with the hydraulic pressure change calculated by the estimated hydraulic pressure change calculating means;
2. The automatic transmission according to claim 1, wherein when there is a difference in oil pressure change by the oil pressure change comparing unit, the air in the pressure oil is discharged by the air bleeding unit. Hydraulic control device. Means for calculating the amount of air mixed into the pressure oil based on the difference between the oil pressure change calculated by the actual oil pressure change calculating means and the oil pressure change calculated by the estimated oil pressure change calculating means;
The hydraulic control device for an automatic transmission according to claim 2, further comprising means for calculating a time for discharging the air in the pressure oil by the air venting means according to the air amount.   4. The apparatus according to claim 1, wherein when the pressure oil in the hydraulic chamber is discharged by the hydraulic pressure discharge means, the air in the pressure oil is discharged by the air bleeding means. 5. A hydraulic control device for an automatic transmission according to 1.

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