KR102270702B1 - Hydrostatic Mechanical Transmission - Google Patents

Abstract

The present invention relates to a hydrostatic mechanical transmission, and more particularly, to a release clutch holding time calculated in consideration of the operating characteristics of a release clutch and a joint clutch when gear shifting in an auxiliary transmission part of a hydrostatic mechanical transmission. By waiting for the release clutch to be released, the present invention relates to a hydrostatic mechanical transmission capable of improving shift quality by suppressing shift shock and the like in the auxiliary transmission unit.
In the present invention, the auxiliary transmission unit 300 having a plurality of clutches 310 driven by the on-off valve 320; _{The release clutch delay time (t stroke _d} ) for the release clutch is calculated in consideration of the operating characteristics of the release clutch and the joint clutch selected from among the plurality of clutches 310 , and after joining to the joint clutch is started, the release a control unit 400 that waits for the clutch delay time (t _{stroke _d} ) and releases the release clutch by driving the on-off valve 320; Disclosed is a hydrostatic mechanical transmission (10), characterized in that it comprises a.

Description

Hydrostatic Mechanical Transmission

The present invention relates to a hydrostatic mechanical transmission, and more specifically, to select a release clutch and a joint clutch in consideration of the torque transmitted through the auxiliary transmission when performing gear shifting in the auxiliary transmission of the hydrostatic mechanical transmission. After that, by waiting for the release clutch holding time calculated in consideration of the operating characteristics of the release clutch and the bonding clutch to release the release clutch, the shift quality can be improved by suppressing shift shock in the auxiliary transmission unit. It relates to a hydraulic mechanical transmission.

In the agricultural work vehicle 1 such as a tractor shown in FIG. 1 , a manual transmission having advantages such as a simple structure, a low price, and high efficiency has been widely used in the prior art. However, in the manual transmission, there is an inconvenience in that the driver has to stop the tractor and manually operate the shift using the clutch pedal and gear lever for shifting. In order to overcome this, a power shift transmission and a continuously variable transmission (CVT) are used. has been proposed Although the power shift transmission uses a number of clutch packs and electronic control systems for automatic shifting, the problem still remains that the clutch pedal must be operated in order for the driver to select the shift lever. On the other hand, the continuously variable transmission (CVT) is attracting attention as a next-generation transmission for agricultural work vehicles because it can solve various problems of the above conventional transmissions.

Among various types of continuously variable transmissions, a hydro-static transmission (HST) has advantages of high power transmission and high durability, while low efficiency and noise problems are pointed out as major drawbacks. As an alternative to overcome this problem, a hydro-mechanical transmission (HMT) may be considered. A hydrostatic mechanical transmission (HMT) is composed of a hydro-static unit (HSU) and a planetary gear set having a clutch and a brake to provide not only auxiliary transmission but also continuously variable transmission function. The hydrostatic mechanical transmission (HMT) can be widely applied to agricultural vehicles such as tractors because it has a wider gear ratio and higher efficiency than the hydrostatic transmission (HST).

However, in the hydrostatic mechanical transmission (HMT), since the sub-shift is theoretically performed when the speeds of the joint clutch and the release clutch are synchronized, a smooth gear shift can be performed without a torque shock, but in an actual system, the clutch speed is controlled. It is not easy to shift smoothly due to the speed difference between the joining and releasing clutches that may occur due to the non-linear characteristics of hydraulic valves such as on-off valves used to As a result, there may be a problem of deterioration of shift quality, and furthermore, a problem of deterioration of durability of the clutch due to slip that may occur during shifting of the clutch.

In this regard, a technology for controlling clutch slip by using an electronic proportional control valve has been proposed in order to achieve smooth shift quality in a passenger car, etc., but when the electronic proportional control valve is used, the product cost is greatly increased.

Accordingly, there is a continuing demand for a hydrostatic mechanical transmission capable of realizing high shift quality by effectively suppressing shift shock caused by power cut while preventing an increase in production cost due to an electronic proportional control valve, etc. No proper solution has been proposed.

Republic of Korea Patent Registration No. 10-1401104

The present invention has been devised to solve the above problems, and the moment that occurs when the operation of the bonded clutch and the release clutch by the hydraulic system is not properly controlled during the clutch replacement in the auxiliary transmission part of the hydrostatic mechanical transmission (HMT). An object of the present invention is to provide a hydrostatic mechanical transmission capable of effectively improving the problem of deterioration of shift quality due to shift shock caused by excessive torque interruption.

In addition, another object of the present invention is a hydrostatic mechanical shift that can effectively suppress the problem of deterioration of the durability of the clutch due to clutch slip, etc. caused by the clutch slippage caused by the clutch not being properly controlled in the auxiliary transmission part of the hydrostatic mechanical transmission (HMT). The purpose is to provide a device.

Other detailed objects of the present invention will be clearly grasped and understood by experts or researchers in the technical field through the specific contents described below.

The hydrostatic mechanical transmission 10 according to an embodiment of the present invention for solving the above problems is a sub-transmission unit 300 having a plurality of clutches 310 driven by an on-off valve 320 . ; _{The release clutch delay time (t stroke _d} ) for the release clutch is calculated in consideration of the operating characteristics of the release clutch and the joint clutch selected from among the plurality of clutches 310 , and after joining to the joint clutch is started, the release Waiting for the clutch delay time (t _{stroke _d} ), the control unit 400 for driving the on-off valve 320 to release the release clutch; characterized in that it is configured to include.

Here, the control unit 400 controls the driving time of the bonding clutch (= the time taken from the start of bonding of the bonding clutch to the completion of bonding) and the driving time of the release clutch (= of the release clutch). The release clutch delay time (t _{stroke _d} ) may be calculated _{in consideration of the difference (=t delay} ) of the time taken from the time when the release is started to the time when the release is completed).

At this time, the control unit 400, the release clutch delay time in consideration of the _{time (= t d_off} ) required from when the release command for the release clutch is applied until the time when the release operation for the release clutch is actually started (= t d_off ) (t _{stroke _d} ) can be calculated.

Furthermore, the control unit 400, the release clutch delay time in consideration of the _{time (= t zero} ) required for the static hydraulic unit 100 stroke to start changing the direction until the pressure of the release clutch becomes 0 (= t zero) (t _{stroke_d} ) can be calculated.

In the hydrostatic mechanical transmission 10 according to an embodiment of the present invention, the release clutch and the joint clutch are selected in consideration of the torque transmitted through the auxiliary transmission unit 300, and then the operating characteristics of the release clutch and the joint clutch are determined. By waiting for the release clutch holding time calculated in consideration of the release clutch to release the release clutch, it is possible not only to suppress shift shocks in the sub transmission unit 300 , and thus improve shift quality, but also to further improve the shift quality of the sub transmission unit 300 . It is possible to effectively suppress deterioration in durability of the clutch 310 due to slip of the clutch 310 that may occur in the .

1 is a side view of a conventional agricultural work vehicle 1 .
2 is a view for explaining the configuration of a conventional hydrostatic mechanical transmission 10.
3 is a graph showing a speed ratio with respect to an auxiliary transmission in a conventional agricultural work vehicle 1 .
4 is a block diagram of a static fusion mechanical transmission 10 according to an embodiment of the present invention.
5 is an explanatory diagram for explaining the operation of the sub-transmission unit 300 of the static fusion mechanical transmission 10 according to an embodiment of the present invention and an equivalent model thereof.
6 is a graph showing simulation results for the bonding clutch and the releasing clutch in the electrostatic coalescence mechanical transmission 10 according to an embodiment of the present invention.
7 is a graph of experimental values for the 1st to 2nd gear shift in the static coalescing mechanical transmission 10 according to an embodiment of the present invention.
8 is an experimental value graph showing the results of sub-transmission in the static fusion mechanical transmission 10 according to an embodiment of the present invention.
9 is a graph of experimental values during acceleration in the hydrostatic fusion mechanical transmission 10 according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, in adding reference numerals to the components of each drawing, it should be noted that the same components are given the same reference numerals as much as possible even though they are indicated on different drawings. In addition, in describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, preferred embodiments of the present invention will be described below, but the technical spirit of the present invention is not limited thereto or may be practiced by those skilled in the art, of course.

First, with reference to FIGS. 2 and 3, the configuration and operation of the conventional hydrostatic mechanical transmission 10 are briefly examined, and then the hydrostatic mechanical transmission 10 according to an embodiment of the present invention is more Describe in detail.

First, in FIG. 2 , the configuration of a conventional hydrostatic mechanical transmission 10 used in an agricultural work vehicle 1 such as a tractor is exemplified. As can be seen in FIG. 1 , in general, a hydrostatic mechanical transmission (HMT) 10 includes a hydrostatic unit (HSU, Hydro-Static Unit) 100, a combined planetary gear set 200 and It may be configured to include a sub-transmission unit 300 . The hydrostatic unit 100 is equipped with a continuously variable transmission (CVT) function capable of changing a speed ratio between an engine speed and a wheel speed. In addition, the compound planetary gear set 200 is composed of two planetary gears. At this time, each planet gear is connected by a pinion gear and a carrier. In addition, as can be seen in FIG. 2 , carriers C1 and C2 are connected to CL1 (clutch 1) and CL3 (clutch 3) of the sub transmission, and the second sun gear (indicated by S2) is connected to CL2 (clutch 2) and connected to CL4 (clutch 4). In the sub-transmission unit 300 , the shift is performed at a point in time when the speed of the bonding clutch and the speed of the release clutch are the same. In the hydrostatic mechanical transmission 10 , the auxiliary transmission 300 may provide an extended speed range to the driver.

In general, clutch slip in the sub transmission unit 300 in the hydrostatic mechanical transmission 10 occurs during shifting of the release clutch and the joint clutch, and improper slip may cause torque shock and clutch wear. have. On the other hand, in an automatic transmission in a passenger car or the like, an electronic proportional control valve is also used to control clutch slip. However, in the present invention, in consideration of cost and control problems, the hydrostatic mechanical transmission 10 is implemented using the on-off valve 320 instead of the electronic proportional control valve.

In addition, the output of the sub transmission unit 300 is connected to the forward clutch (FOR) and the reverse clutch (REV), and accordingly, the moving direction of the agricultural work vehicle 1 such as a tractor is the forward clutch (FOR) and the reverse clutch (REV) subject to change.

Next, in FIG. 3 , a graph of the speed ratio at the auxiliary transmission in the conventional agricultural work vehicle 1 is exemplified. More specifically, the range of the speed ratio (SR, speed ratio) for each sub-transmission gear is shown in FIG. 3 . The speed ratio SR may be defined as the ratio of the wheel speed ω _{wh to the engine speed ω e .} In Fig. 3, each line shows the range of the speed ratio in each gear (1st to 4th gear). More specifically, when the engine is turned on, it starts in first gear, with the i _stroke (= ω _m / ω _p = rotation speed of HSU motor / rotation speed of HSU pump) starts from 0.87, and wheel speed ω _wh = 0 (point (A) of FIG. 3 ). This makes it possible to ignite the engine without an engine clutch or torque converter. If the engine speed is maintained, the wheel speed increases as the _{i stroke decreases.} In the auxiliary transmission unit 300, the auxiliary transmission is performed at the intersection point between each line. For example, 1st gear ↔ 2nd gear subshift is made at a speed ratio (SR) of 0.0171 (point (B) in FIG. 3). At this time, theoretically, since the sub-shift is made at the point where the speed difference between the 1st and 2nd clutch discs is 0, smooth shifting is possible without torque shock. However, if the i- _stroke is not accurately implemented during the actual sub-shift, the clutch The speed difference between the disc and the plate causes a torque shock, which deteriorates the shift quality.

4 illustrates a configuration diagram of a static fusion mechanical transmission 10 according to an embodiment of the present invention. As can be seen in FIG. 4 , the hydrostatic combined mechanical transmission 10 according to an embodiment of the present invention includes a static hydraulic unit 100 , a compound planetary gear set 200 , an auxiliary transmission unit 300 and a control unit ( 400) may be included.

More specifically, in the hydrostatic mechanical transmission 10 according to an embodiment of the present invention, the auxiliary transmission unit 300 includes a plurality of clutches 310 driven by an on-off valve 320 to be configured. _{In this case, the control unit 400 calculates the release clutch delay time (t stroke _d} ) for the release clutch in consideration of the operating characteristics of the release clutch and the bonding clutch selected from among the plurality of clutches 310 , and the _{Waiting for the release clutch delay time (t stroke _d} ) after joining to the joining clutch is started, by driving the on-off valve 320 to release the release clutch, torque is disconnected between the release clutch and the joining clutch to suppress shift shock and the like in the sub transmission unit 300 and improve shift quality, and furthermore, due to slip of the clutch 310 that may appear in the sub transmission unit 300 , It is possible to effectively suppress deterioration in durability of the clutch 310 .

In this case, the control unit 400 may select a release clutch to be released and a joint clutch to be joined from among the plurality of clutches 310 in consideration of the first torque transmitted through the auxiliary transmission unit 300 .

For example, in FIG. 3 , when the driver starts the agricultural work vehicle 1 such as a tractor, the speed ratio SR increases by driving CL1 (clutch 1) in the first gear to the first-second gear shift point. In this case, the control unit 400 may select CL1 (clutch 1) as an off-going clutch and select CL2 (clutch 2) as an on-coming clutch. Next, in consideration of the operation characteristics when the release clutch CL1 (clutch 1) is released and the operation characteristics when the joint clutch CL2 (clutch 2) is joined, the torque disconnection does not occur when the release clutch and the joint clutch are shifted. By delaying the operation of the release clutch CL1 (clutch 1), it is possible to prevent torque disconnection due to the shift operation between the release clutch and the joining clutch.

More specifically, in the control unit 400, the driving time of the bonding clutch (= the time taken from the start of bonding of the bonding clutch to the completion of bonding) and the driving time of the release clutch (= the release clutch) _{After calculating the delay time (t stroke _d} ) of the release clutch in consideration of the difference _{(= t delay} ) of the time taken from the time when the release is started to the time when the release is completed), the joining to the joining clutch is started After waiting for the release clutch delay time (t _{stroke _d} ), the release clutch may be released.

Furthermore, the control unit 400, after the release command for the release clutch is applied _{, also considers the time (=t d_off} ) required until the release operation for the release clutch is actually started in consideration of the release clutch delay time (t _{stroke _d} ) can also be calculated.

In addition, the control unit 400 delays the release clutch in consideration of the _{time (= t zero} ) required until the pressure of the release clutch becomes 0 when the stroke of the hydrostatic unit 100 starts to change direction It is also possible to calculate the time (t _{stroke _d ).}

In addition, the control unit 400 _{maintains a constant swash plate angle with respect to the release clutch for the calculated release clutch delay time (t stroke _d} ), and then releases the release clutch, so that the auxiliary transmission unit 300 Not only can the quality of shifting be improved by suppressing shift shock, etc., but also the deterioration of durability of the clutch 310 due to slip of the clutch 310 that may appear in the auxiliary transmission unit 300 is effectively suppressed. be able to do

Hereinafter, the configuration and operation of the hydrostatic mechanical transmission 10 according to an embodiment of the present invention will be described in more detail with reference to the drawings.

5 shows an explanatory diagram for explaining the operation of the sub-transmission unit 300 of the electrostatic coalescence mechanical transmission 10 according to an embodiment of the present invention and an equivalent model (AMESim model) therefor. As described above with reference to FIG. 2 , the electrostatically combined mechanical transmission 10 according to an embodiment of the present invention may include an auxiliary transmission unit 300 including four clutches CL1-CL4. In addition, as can be seen in FIG. 5( a ), more specifically, the sub-transmission unit 300 may include a clutch 310 , an on-off valve 320 and a relief valve 330 , in which case the The clutch 310 includes a piston 311, a plate 312, a disk 313, a return spring 314, a rubber ring 315 and a check ball 316. may be included.

Referring to FIG. 5 , the hydraulic oil flow in the auxiliary transmission unit 300 is supplied from the oil pump (Flow from the pump), and in this case, the relief valve 330 maintains a constant line pressure by the oil. . Subsequently, when a bonding command signal for the clutch 310 is applied by the controller 400 , the on-off valve 320 is opened and oil flows into the piston 311 of the clutch 310 . Accordingly, when the pressure of the introduced oil becomes greater than the force of the return spring 314 , the piston 311 of the clutch 310 starts to move, and the rubber installed between the plate 312 and the disk 313 . It comes into contact with the ring (rubber ring) (315). The rubber ring 315 serves to maintain a gap between the plate 312 and the disk 313 when the clutch 310 is released. In this case, each rubber ring 315 of FIG. 5 may be modeled as a spring and a damper. The check ball 316 of the piston 311 is provided to prevent the centrifugal force effect of the oil when the clutch 310 is released.

Next, in order to analyze the characteristics of the electrostatically combined mechanical transmission 10 according to an embodiment of the present invention, as shown in FIG. 5(b) , the AMESim model is used for the joining and releasing operations of the clutch 310. simulation was performed. 6 shows a simulation result graph for the operating characteristics of an on-coming clutch and an off-going clutch. In the case of the junction clutch, when the clutch junction signal is applied at time P (t = 0.1 sec), the on-off valve 320 starts to open, and as can be seen in FIG. 6(a), the clutch pressure ( clutch pressure) begins to increase until time Q (t = 0.3 s). In this case, in the P-Q region, the pressure characteristic of the clutch 310 may be determined according to the volume of the clutch 310 and the reaction force of the return spring 314 and the rubber ring 315 . In this simulation, a non-linear stiffness model is used for the rubber ring 315 . Further, as can be seen in Fig. 6(b), the clutch clearance of the joint clutch decreases in the P-Q region and reaches 0 mm at the intersection point Q. Also, after the crossing point Q, the clutch pressure starts to increase again to a line pressure of 20 bar.

In the case of the release clutch, as can be seen in FIG. 6(a'), the clutch pressure decreases exponentially while the clutch release signal is applied.

From the simulation results of FIG. 6 , it can be confirmed that the operating characteristics of the coupling clutch are very different from the operating characteristics of the release clutch due to the stiffness of the return spring 314 and the rubber ring 315 . At this time, due to the different pressure response operation characteristics as described above, a torque break and a torque shock between the release clutch and the coupling clutch may be induced. More specifically, in order to analyze the influence of the different pressure response operating characteristics of the release clutch and the coupling clutch, an experiment was performed on an up shift from the first gear to the second gear.

7 shows a sub-shift experiment result of up-shifting from the first gear to the second gear using the on-off valve 320 . 1st - 2nd sub shift signal was applied at t = 0 sec when _{i stroke = -0.72.} During sub-transmission, the stroke of the hydrostatic unit (HSU) _{is maintained at i stroke} = -0.72, and at this time, the speeds of the joining clutch CL2 and the release clutch CL1 become the same (refer to FIG. 3). It can be seen from FIG. 7(a) that the pressure of the release clutch CL1 and the pressure of the bonding clutch CL2 show a similar reaction to the simulation result of FIG. 6 . However, as shown in FIG. 7(b) , it can be seen that torque interruption and torque shock may occur during the shift. The causes of such torque disconnection and torque shock can be analyzed for each area as follows.

As can be seen in Figure 7 (b), the output torque (HMT output torque) of the hydrostatic mechanical transmission 10 is reduced according to the release clutch (CL1) pressure. Since the output torque of the electrostatic fusion mechanical transmission 10 is 0 in the R-S region, it can be seen that the torque break occurs in the R-S region. In addition, as can be seen in FIG. 7( c ), the output speed (HMT output speed) of the hydrostatic fusion mechanical transmission 10 decreases as the output torque decreases.

At this time, when the bonding clutch CL2 reaches the kissing point S, the output torque of the electrostatically coupled mechanical transmission 10 starts to increase (torque transmitted by the bonding clutch increases). Subsequently, the output torque of the electrostatically coupled mechanical transmission 10 increases rapidly, indicating that torque shock may occur in the SV region, which causes the plate 312 of the clutch 310 to have a large vehicle inertia during slipping. This is because it is linked with the output shaft affected by Unlike the simulation result of FIG. 7 , the pressure of the bonding clutch CL2 does not increase after the bonding point S (see FIG. 7(a) ), because the line pressure is not recovered in the S-V region. In addition, after the V point, the bonding clutch CL2 pressure increases according to the line pressure. The line pressure decreases when oil flows into the joining clutch CL2 (Q-S region). The reason that the line pressure is not recovered in the SV region is that a constant flow rate is required to fill the flow rate of another hydraulic circuit for lubrication and cooling ('Hydraulic circuit A' in Fig. 5), which is not considered in this simulation. Because.

From the above experimental results, it was confirmed that the pressure response of the on-off valve 320 had different time delays of 0.02 seconds for the release clutch and 0.07 seconds for the bonding clutch, respectively. At this time, the reason why the time delay of the bonding clutch is greater than the time delay of the release clutch may be attributed to the oil filling time in the piston 311 required for the operation of the bonding clutch.

7(b) and 7(c) show that oscillation may occur after the bonding clutch CL2 is completely bonded at the W point. The oscillation is caused by a relatively large change in inertial torque of the drive train of the electrostatically coupled mechanical transmission 10 immediately after the torque impact.

In particular, the torque shock seen in FIG. 7 deteriorates the shift quality, that is, the driving comfort of the driver. On the other hand, in an automatic transmission of a passenger car, torque shock was suppressed by clutch slip control using an electromagnetic proportional control valve. However, in the case of using the proportional control valve as described above, it may cause an increase in manufacturing cost, and furthermore, accurate control of the clutch pressure is required. On the other hand, since the agricultural work vehicle 1 such as a tractor does not require shift quality to the level of a passenger car, by using an on-off valve, it is possible to significantly reduce manufacturing cost while effectively suppressing torque shock. As can be seen from the experimental results of FIG. 7 , the torque shock occurs immediately after the torque is disconnected. This is because the release clutch CL1 is released before the bonding of the bonding clutch CL2. Accordingly, it can be seen that if the release clutch CL1 can be released by waiting for an appropriate timing, the torque shock can be effectively prevented.

In contrast, in the electrostatic fusion mechanical transmission 10 according to an embodiment of the present invention, a control algorithm for delaying the release timing of the release clutch is used to prevent torque disconnection. The basic concept of the control algorithm according to the present invention is to control to maintain the sum of the clutch torques of the release clutch CL1 and the joint clutch CL2 while the sub-shift is performed.

In this case, in general, the clutch torque TCL may be expressed by Equation 1 as follows.

[Equation 1]

,

,

In this case, N is the number of disks 313 of the clutch 310 and μ is the friction coefficient. In addition, R _eff represents the effective radius of the disk 313 , and A _pis represents the area of the piston 311 .

At this time, while the sub-transmission is made, the output torque of the hydrostatically coupled mechanical transmission 10 may be expressed as the sum of the torques of the release clutch and the joint clutch as shown in Equation 2 below.

[Equation 2]

,

,

Here, T _out represents the output of the static fusion mechanical transmission 10 .

At this time, the clutch torque changes according to the clutch pressure. As mentioned above, under the assumption that the clutch pressure changes exponentially, the torque T _{CL _off} of the release clutch may be expressed by Equation 3 as follows.

[Equation 3]

,

,

Here, a_dis is a time constant, P _l is the maximum line pressure when the clutch 310 is fully connected, t _{d_off} is the delay time of the release clutch pressure, and t _delay is the delay of the release clutch to be calculated in the present invention. It's time.

In addition, the torque (T _{CL _on} ) of the joint clutch may also be expressed using an exponential function as in Equation 4 below.

[Equation 4]

Here, a_eng is a time constant, and t _{d_on} is a delay time of the bonding clutch pressure. It can be seen from FIG. 7 that the clutch torque is 0 regardless of the pressure of the junction clutch CL2 up to the junction point S. In the SV region, the bonding clutch CL2 pressure maintains an almost constant value _{of P SV .} Accordingly, Equation 4 can be applied only to the VW region. In the present invention, the torque (T _{CL _on} ) of the bonding clutch can be calculated using Equation 4 for a constant pressure value in the SV region and the VW region.

_{In addition, by using the output (T out} ) of the electrostatic fusion mechanical transmission 10 of Equation 2, it is possible to calculate _{the time delay (t delay} ) for the release clutch at a given load torque (T _{out ).}

8 shows the performance improvement by the sub-shift control algorithm using the time delay of the release clutch according to an embodiment of the present invention. A sub-transmission experiment from 1st to 2nd gear was performed for load torque T _{out = 100Nm and 300Nm.} During sub-shifting, the hydrostatic unit (HSU) stroke was _{maintained at i stroke} = -0.72, which means that the speed of the release clutch and the joint clutch are the same. _{The time delay in the release clutch was calculated for the case of t delay} = 0.11 sec and 0.19 sec for load torques of 100 Nm and 300 Nm, respectively, using Equation (2).

As can be seen from the experimental results of FIG. 8 , the output torque of the electrostatic fusion mechanical transmission 10 was maintained at target load torques of 100 Nm and 300 Nm without torque interruption and torque shock. Even when some torque oscillations appeared, the magnitude of the torque oscillations was much smaller than in the case of the prior art. Accordingly, it was confirmed that the output speed of the oil-repellent mechanical transmission 10 was maintained at a constant speed with respect to both load torques.

However, it can be seen from the experimental results that the pressure of the release clutch CL1 shows a slightly different result from the expected value. That is, the release clutch (CL1) pressure is _{expected to start to decrease at the time point Q after the time delay t delay} + t _{d_off} from the release command signal, but in contrast to this, in FIG. 8(a), the pressure decreases after the time point P along the line pressure. You can see that you are starting to This is because the line pressure decreases due to insufficient oil flow when oil flows to the bonding clutch CL2. The release clutch (CL1) pressure starts to decrease at the point Q, is separated from the line pressure, and decreases exponentially. Despite the initial pressure reduction in the PQ region, since the T _out value calculated in Equation 2 is sufficient to transmit the given load torque, the output torque of the static fusion mechanical transmission 10 ( FIG. 8( b )) is It is maintained at a value similar to the target load torque.

In the case of the pressure of the release clutch CL1 and the bonding clutch CL2, a similar response is shown at a load torque of 300 Nm (Fig. 8(a')). In addition, the output torque (FIG. 8(b')) of the electrostatic fusion mechanical transmission 10 is maintained at a level of 300 Nm without torque interruption or torque shock.

Previously, the sub-transmission experiment was performed with respect to the case where the _{constant hydraulic unit (HSU) stroke was maintained at a constant i stroke} = -0.72 for the sub-transmission from the first gear to the second gear. However, in an actual environment, as can be seen in FIG. 3 , the hydrostatic unit (HSU) stroke must change direction immediately after sub-shifting. If the hydrostatic unit (HSU) stroke control is performed without considering the sub-shift time, it may cause a large torque variation. Therefore, in the present invention, the constant hydraulic unit (HSU) stroke is constantly maintained during sub-shift by applying a method that additionally considers the constant hydraulic unit (HSU) stroke duration control. At this time, the constant hydraulic unit (HSU) stroke duration (t _{stroke _d} ) may be determined as in Equation 5 below.

[Equation 5]

In this case, t _delay and t _{d_off} are the time delays of the pressure of the release clutch and the on-off valve 320 described above, and t _zero is the pressure zero time of the release clutch. At this time, the pressure zero time of the release clutch may be defined as the time when the release clutch pressure becomes zero, and more specifically, the pressure zero time is in the fully released state of the release clutch when the stroke starts to change the direction immediately after the sub-shift. The time required to reach If the pressure zero time is not secured, clutch slip may occur and torque fluctuation may be caused. The pressure zero time may be obtained through an experiment (see FIG. 7 ).

9 exemplifies an experimental result graph to evaluate the performance of the sub-shift control algorithm using the delay of the release clutch according to an embodiment of the present invention. More specifically, in FIG. 9 , the experimental results performed while the _{tractor starts in a stationary state (v tractor} = 0 kph) and increases to v tractor = 15 kph for 15 seconds are shown. In the experiment, the input speed (traction motor) of the electrostatic fusion mechanical transmission 10 was maintained at 1600 rpm, and a constant load torque of 120 Nm was applied using a dynamo motor.

It can be seen from FIG. 9(A) that _{a slight delay occurs whenever the tractor speed is increased to v tractor} = 15 kph and a sub-shift occurs. Until the tractor speed _{reached a value of v tractor} = 15 kph and the hydrostatic unit (HSU) stroke followed the command stroke, the hydrostatic fusion mechanical transmission 10 output torque varied between 170 and 180 Nm. When the tractor speed _{reached v tractor} = 15 kph, the output torque of the electrostatic mechanical transmission 10 decreased to a given load torque of about 120 Nm and maintained the required load torque. During the acceleration time of 15 seconds, the output torque of the electrostatic fusion mechanical transmission 10 was higher than the required torque required to satisfy the acceleration of the large tractor inertia. 9(B) shows the time response for t = 6 to 11 seconds. From Fig. 9(c'), the hydrostatic unit (HSU) stroke is a _{constant value during the auxiliary transmission i stroke} = -0.72 for the 1st->2nd gear and i _stroke = 0.03 for the 2nd->3rd shift. can be seen to be maintained. _{The duration (t stroke _d} ) of the hydrostatic unit (HSU) stroke (FIG. 9(c')) is 0.42 sec and 0.46 sec for the 1st->2nd and 2nd->3rd gears, respectively, in Equation 5 was obtained from t _delay was calculated using Equation 2 for the target load torque.

From the experimental results of FIG. 9 , the sub-shift control algorithm in the hydrostatic combined mechanical transmission 10 according to an embodiment of the present invention uses the on-off valve 320 to achieve satisfactory shifting performance without torque interruption and torque shock. It can be confirmed that it is possible to provide

The above description is merely illustrative of the technical idea of the present invention, and those of ordinary skill in the art to which the present invention pertains may make various modifications, changes, and substitutions within the scope not departing from the essential characteristics of the present invention. It will be possible. Therefore, the embodiments disclosed in the present invention and the accompanying drawings are for explanation rather than limiting the technical spirit of the present invention, and the scope of the technical spirit of the present invention is not limited by these embodiments and the accompanying drawings. . The protection scope of the present invention should be interpreted by the claims below, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

(1) : Agricultural work vehicle (2) : Vehicle body
(10): hydrostatic mechanical transmission (100): hydrostatic unit
(200): compound planetary gear set (300): auxiliary transmission
(310): Clutch (311): Piston
(312): plate (313): disc
(314): return spring (315): rubber ring
(316): check ball (320): on-off valve
(330): relief valve (400): control unit

Claims (4)

an auxiliary transmission unit 300 having a plurality of clutches 310 driven by an on-off valve 320 ;
_{The release clutch delay time (t stroke_d} ) for the release clutch is calculated in consideration of the operating characteristics of the release clutch and the joint clutch selected from among the plurality of clutches 310 , and after joining to the joint clutch is started, the release clutch a control unit 400 that waits for a delay time t _{stroke_d} and releases the release clutch by driving the on-off valve 320;
It consists of
The control unit 400,
The driving time of the bonding clutch (= the time taken from the start of bonding of the bonding clutch to the completion of bonding) and the driving time of the release clutch (= the release is completed from the starting point of the release of the release clutch A hydrostatic mechanical transmission (10), characterized in that the release clutch delay time (t _{stroke_d} ) is calculated in consideration of the difference (= t _{delay) of the time taken until the} delete According to claim 1,
The control unit 400,
_Calculating the release clutch delay time (t _{stroke _d} ) in consideration of the time (= t d_off ) required from the time the release command for the release clutch is applied until the time when the release operation for the release clutch is actually started (= t d_off ) A hydrostatic mechanical transmission (10), characterized in that. According to claim 1,
The control unit 400,
It is characterized in that the release clutch delay time (t _{stroke_d} ) is calculated _{in consideration of the time (= t zero} ) required until the pressure of the release clutch becomes 0 after the stroke of the hydrostatic unit 100 starts to change direction A hydrostatic mechanical transmission (10).

Images