JPH0143180B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Field of Application This invention is for controlling the hydraulic pressure applied to a hydraulic clutch in a hydraulic clutch type transmission installed in a self-propelled working vehicle such as a self-propelled agricultural vehicle or a construction vehicle. More specifically, a control piston that receives the tip of a hydraulic pressure setting spring and increases the strength of the hydraulic pressure setting spring by advancing the control piston is provided so as to be able to advance to a regulated position, and a control piston is provided behind the control piston. The present invention relates to a hydraulic control device equipped with a pressure regulating valve forming an oil chamber for applying hydraulic pressure from an oil supply circuit to a hydraulic clutch in a hydraulic clutch type transmission.

BACKGROUND ART A hydraulic control device configured as described above is known from, for example, Japanese Utility Model Application No. 52-98051. , was configured to act through a diaphragm.

Such a hydraulic control device operates when a switching valve that switches and controls the supply and discharge of hydraulic pressure to and from a hydraulic clutch in a hydraulic clutch type transmission is displaced from a neutral position to one working position or from one working position to another working position. The control piston is gradually advanced by the hydraulic action of the oil supply circuit via the above-mentioned throttle, and the strength of the pressure setting spring is gradually increased, so that the hydraulic pressure applied to the hydraulic clutch is gradually increased, and the hydraulic pressure is increased. To smoothly engage a clutch to smoothly start a vehicle or change vehicle speed, thereby improving the driver's feeling.

Problems to be Solved by the Invention This conventional system has several problems because the hydraulic pressure of the clutch oil supply circuit is applied to the back of the control piston in the pressure regulating valve through a throttle.

The first problem is that the rise characteristic of the oil pressure over time from the point of displacement of the switching valve is largely influenced by the oil temperature and the engine speed. In other words, the amount of oil that passes through the orifice that provides resistance to the flow of oil fluctuates greatly due to changes in oil viscosity due to oil temperature, and also changes in the amount of oil discharged from the pump due to changes in the hydraulic pump rotation speed based on changes in engine speed. The oil pressure rises rapidly when the oil temperature and engine speed are high, and the rise is slow when the oil temperature and engine speed are low. The rise characteristics of the oil pressure change over time as follows. Such characteristic fluctuations make it impossible to provide a constant and good feeling to the driver when starting the vehicle and changing gears.

The second problem is that it is impossible to perform a so-called shock shift in which the oil pressure is instantaneously raised to the relief pressure of the pressure regulating valve at the time of displacement of the switching valve. In other words, it is desirable to engage the hydraulic clutch in a buffering manner, but when scooping earth, sand, or compost from the ground using a bucket or fork attached to the front or rear of a self-propelled work vehicle, the vehicle must be engaged. If you don't move it like a dart, it won't be able to scoop it up properly, and if you change gears during heavy towing such as trenching or deep rotary work in the field, there is a risk that the vehicle will stop if you don't change gears instantaneously. Furthermore, when the vehicle itself or the work equipment towed by the vehicle is to escape from a wet field or muddy area, the vehicle must move forward in a dart-like manner. However, with the conventional one that uses a throttle, it is impossible to achieve the desired shock speed change in such a case.

The main object of the present invention is to provide a hydraulic control device having the structure described at the beginning, by eliminating the throttle that was conventionally inserted into the circuit for applying the hydraulic pressure of the clutch lubricating circuit behind the control piston of the pressure regulating valve. The above-mentioned two features of the conventional system enable smooth engagement.
There are two problems to be solved.

In order to achieve this main purpose, this invention
We propose the use of a pair of solenoid valves that control the supply and discharge of oil to the back of the control piston in a pressure regulating valve without using a throttle, but the accompanying purpose is to throttle such oil flow. Oil supply/discharge control without oil supply/discharge, in other words, because oil supply/discharge is performed quickly, it is difficult to accurately control the position of the control piston whose position is changed according to the oil supply/discharge. An object of the present invention is to provide a hydraulic control device which performs supply/discharge control of a hydraulic clutch so as to appropriately obtain hydraulic pressure change characteristics that achieve shock-free engagement of a hydraulic clutch.

Means for solving the problem In order to solve the problem of this invention, this invention is the first
As illustrated in the figure, a control piston 2 that receives the tip of the oil pressure setting spring 1 and increases the strength of the oil pressure setting spring 1 by advancing the control piston 2 is provided so as to be able to move forward to a regulated position. Behind is an oil chamber 5 for applying the oil pressure of the oil supply circuit 4 to the hydraulic clutches 3F ₁ , 3F ₂ , 3F ₃ , 3R in the hydraulic clutch type transmission.
The following technical measures were taken in a hydraulic control device equipped with a pressure regulating valve 6 formed with a pressure regulating valve 6.

That is, as illustrated in FIG. 1, the present invention first includes a first circuit 7 that connects the oil supply circuit 4 to the oil chamber 5 without using a throttle, and the oil chamber 5.
and a second circuit 9 that connects the oil tank 8 to the oil tank 8, and each of the first circuit 7 and the second circuit 9 is provided with a position for making each circuit conductive and a position for cutting off the circuit. The first solenoid valve 10A and the second
Technical measures such as inserting and installing a solenoid valve 10B will be taken.

Each solenoid valve 10A, 10B has a solenoid 11A,
11B (hereinafter, excitation is referred to as "on" and demagnetization is referred to as "off"), but in the illustrated example, the first solenoid valve 10A is turned off in the first circuit 7 by turning off the solenoid 11A. In the conductive state,
Further, the second solenoid valve 10B is configured to cut off the second circuit 9 when the solenoid 11B is turned off.

As usual, the pressure regulating valve 6 includes a valve body 14 that sets the hydraulic pressure corresponding to the strength of the spring 1 while relieving oil from the pump port 12 to the tank port 13 under the force of the hydraulic pressure setting spring 1. There is. The pump port 12 is connected to the oil supply circuit 4, and an oil passage hole 14a is formed in the valve body 14 for guiding the hydraulic pressure of the pump port 12 to the back of the valve body 14. In order to limit the amount of advance of the control piston 2, an annular step 15 is formed on the inner surface of the valve case.

Next, as illustrated in FIG. It is possible to set a control oil pressure (hydraulic pressure P ₁ , P ₂ shown in Fig. 5) lower than the oil pressure Pa) shown in Figs. 5 and 6, and output a second electric signal corresponding to the set control oil pressure. control hydraulic pressure setting means VRa ₁ , VRa ₂ , VRb ₁ , VRb ₂ ,
Hydraulic pressure comparison means 29A, 29B receive first and second electric signals from the above-mentioned oil pressure sensor and control oil pressure setting means, compare the values of both electric signals, and output a third electric signal according to the magnitude thereof. and a shift operation means 26 (eighth) for a hydraulic clutch type transmission.
a timer means 31 which outputs a fourth electrical signal for a set time when the above-mentioned oil pressure comparison means and timer means are operated; Solenoid valve displacement control circuits 32A, 32B, 33, TRa, which control the displacement of the second solenoid valves 10A, 10 in response to the third electric signal so that the control oil pressure is maintained;
TRb is provided.

In the illustrated example, the above-mentioned control oil pressure setting means sets variable resistors VRa 1 and VRa 2 designed to set the lower limits of the control oil pressures P ₁ and P ₂ and variable resistors designed to set the upper limits of the control oil pressures P ₁ and P ₂ as illustrated in FIG. It also consists of VRb ₁ and VRb ₂ . In addition, the above-mentioned solenoid valve displacement control circuits 32A, 32B, TRa, and TRb are as shown in the figure.
It is configured to include first and second transistors TRa and TRb that turn on the solenoids 11A and 11B of the first and second electromagnetic valves 10A and 10B by an on-action.

In FIG. 1, 16 is the aforementioned hydraulic clutch 3.
This is a power shift shaft on which F ₁ -3R is mounted, and this power shift shaft 16 is selectively rotated at variable speeds by selective engagement of each hydraulic clutch. In order to selectively supply the hydraulic oil discharged from the hydraulic pump 17 to the oil supply circuit 4 to the hydraulic clutches 3F ₁ -3R, in addition to the neutral position N, two operating positions F ₃ , R and F ₁ are required. , F ₂ are connected in series in the oil supply direction to the clutch. These electromagnetic switching valves 18A and 18B are solenoid 1.
By alternatively turning on 9F ₃ , 19R and 19F ₁ , 19F ₂ , the hydraulic clutch 3 is alternatively displaced to the operating position F ₁ , F ₂ , F ₃ , R, and any one of the hydraulic clutches 3
F ₁ , 3F ₂ , 3F ₃ , and 3R are selectively activated.

Operation When the electromagnetic switching valves 18A, 18B are moved to any operating position and the oil drain from the oil supply circuit 4 disappears, the solenoids 11A, 11 are activated as shown in FIG.
When B is turned off, oil is supplied from the oil supply circuit 4 to the oil chamber 5 via the first circuit 7, which causes the control piston 2 to move forward and set the oil pressure setting spring 1.
This will increase the strength of the Further, as shown in FIG. 3, the solenoid 11A is turned on to cause the first solenoid valve 7 to cut off the first circuit 7, and the solenoid 11B is turned on, so that the second solenoid valve 10B makes the second circuit 9 conductive. If this is the case, the oil is drained from the oil chamber 5, and if the control piston 2 is advanced beyond the most retracted position shown in FIG. As a result, the strength of the spring 1 is reduced. Further, as shown in FIG. 4, if the solenoid 11A is turned on and the first solenoid valve 10A shuts off the first circuit 7, and the solenoid 11B is turned off, the oil chamber 5 is connected to both the solenoid valves 10A and 10B. This blocks the control piston 2 and keeps the control piston 2 at a fixed position, so that the strength of the oil pressure setting spring 1 is kept constant.

FIG. 5 is a graph showing the control mode of the clutch working oil pressure P together with the oil pressure control signal in the embodiment described later, and the horizontal axis shows time t, and the vertical axis shows the clutch working oil pressure P. . The intersection point O between the horizontal and vertical axes is the point in time when the electromagnetic switching valves 18A and 18B are operated for displacement. Figure 5 a shows the time of departure;
Figure b shows the time of gear shifting. In each case, the control piston 2 is at its most forward position and the low control oil pressure P is smaller than the normal clutch working oil pressure Pa set by the pressure regulating valve 6. ₁ or _P2 for a certain period of time, during which time the hydraulic clutch is initially engaged, and then the normal operating oil pressure Pa is obtained.

Such change control of the oil pressure P is performed by the above-mentioned electric control mechanism shown in FIG. 2 as follows. That is, the above-described low control oil pressures P ₁ and P ₂ are set in the control oil pressure setting means VRa ₁ , VRa ₂ , VRb ₁ and VRb ₂ , and the oil pressure comparison means 29A and 29B are set to the oil pressure of the oil supply circuit 4 detected by the oil pressure sensor 20. The control oil pressure P ₁ or P ₂ set in the control oil pressure setting means VRa ₁ -VRb ₂ is compared, and the third electrical signals Sgu and Sgv described above are outputted as shown in FIG. On the other hand, the timer means 31 is connected to the speed change operation means 2.
6 (FIG. 8), when the hydraulic clutch type transmission is started or shifted, the fourth electric signal Sg ₁ or Sg ₂ is activated for a set time T ₁ or Sg 2 as shown in FIG. 2. Since only T ₂ is output, the third electrical signal
The electromagnetic valve displacement control circuits 32A, 32 operate when Sgu, Sgv and the fourth electric signals Sg ₁ , Sg ₂ are input.
B, 33, TRa, and TRb operate both electromagnetic valves 1 so that the low control oil pressure P ₁ or P ₂ is maintained only during time T ₁ or T ₂ when a starting operation or a gear change operation is performed.
Controls the displacement of 0A and 10B.

Therefore, the control mechanism shown in FIG.
is moved from the neutral position N to the working position 1, and from the moment when the oil pressure P is rapidly increased to the low control oil pressure _P1 at the positions of the two electromagnetic valves 10A and 10B shown in FIG. is placed in the hydraulic control position shown in Fig. 4, and the low control hydraulic pressure P ₁ is maintained for a certain period of time.
After time _T1 , both solenoid valves 10A and 10B are returned to the hydraulic control position shown in FIG. A certain normal working oil pressure Pa is then applied. Furthermore, during the gear shift shown in FIG.
After setting both solenoid valves 10A and 10B to the hydraulic control position shown in _FIG .
A, 10B are placed in the hydraulic control position shown in FIG. 4, and a low control oil pressure _P2 is maintained for a certain period of time. After time _T2 , both solenoid valves 10A, 10B are placed in the hydraulic control position shown in FIG. Obtain the normal working oil pressure Pa. In this way, by maintaining the low control oil pressure P ₁ or P ₂ , the hydraulic clutch can be initially engaged without any shock, and then the regular high oil pressure Pa can be applied to the hydraulic clutch, so the vehicle starts and shifts smoothly. It will be held in

The above-mentioned shock shift can be achieved by keeping both electromagnetic valves 10A, 10B at the hydraulic control position shown in FIG. 1 both when the vehicle starts and when the vehicle speed is changed. In other words, at that time, when the vehicle is starting, if either of the solenoid switching valves 18A or 18B is moved from the neutral position to the first operating position as shown in FIG. If the normal operating oil pressure Pa is quickly obtained and the gear is being changed, moving the electromagnetic switching valves 18A and 18B from one operating position to the other operating position will result in the following operation as shown in FIG. 6b.
Since one electromagnetic switching valve 18A or 18B passes through the neutral position N, there is a slight oil pressure drop,
Even if this occurs, the previously high normal working oil pressure Pa is substantially maintained. Therefore, in either case, the hydraulic clutch corresponding to the new position of the electromagnetic switching valves 18A, 18B quickly completes engagement.

In the illustrated example, for such a shock shift, in accordance with one embodiment of the present invention, a first electric signal Sgu, Sgv is provided in the solenoid valve displacement control circuit, independent of the third electric signals Sgu, Sgv from the hydraulic pressure comparing means 29A, 29B. and a manual switch SWa for displacing the second solenoid valves 10A and 10B to a position (the position shown in FIG. 1) where the first circuit 7 is rendered conductive and the second circuit 9 is shut off. SWb is provided.

Embodiment Valve and hydraulic circuit Valves 6, 10 provided in the illustrated embodiment
A, 10B, 18A, 18B and the hydraulic circuits are as described above with respect to FIG.

The aforementioned hydraulic clutches 3F ₁ , 3F ₂ , 3F ₃ , 3
R is designed to rotate the power shift shaft 16 in 1st forward speed, 2nd forward speed, 3rd forward speed, or 1st reverse speed R by its selective engagement, and correspondingly, the solenoid switching valves 18A and 18B rotate. The operating position F ₁ -R is the forward 1st speed position F ₁ and the forward 2nd speed position
F ₂ , 3rd forward speed position F ₃ , and 1st reverse speed position R.

Sensor In the illustrated embodiment, the sensors include the oil pressure sensor 20 and the rotary switch 21 shown in FIG.
and is provided.

As shown in FIG. 7, the oil pressure sensor 20 is screwed onto a sensor mounting portion 22 provided in the oil supply circuit 4 (FIG. 1), and is mounted on a diaphragm 23 that receives the oil pressure of the oil supply circuit 4. The structure is configured such that the oil pressure of the oil supply circuit 4 is detected by attaching the strain gauges Rg ₁ , Rg ₂ , Rg ₃ , and Rg ₄ to the resistance value change of the strain gauges Rg ₁ - Rg ₄ based on the change in the oil pressure. has been done. The four strain gauges are assembled into a bridge circuit as shown in FIG. 2 and inserted into the hydraulic control circuit shown in FIG.

Next, the rotary switch 21 shown in FIG. 8 is switched to the on side in order to alternatively turn on the solenoids 19F ₁ , 19F ₂ , 19F ₃ , 19R of the electromagnetic switching valves 18A, 18B shown in FIG. In addition to the contacts 25F ₁ , 25F ₂ , 25F _{3 ,} and 25R, the electromagnetic switching valves 18A and 18B are provided with a contact 25N that is switched to the on side when they are in the neutral position _. ,25F ₃ ,2
5R is a shift lever 26, which is the shift operation means for changing and controlling the positions of the electromagnetic switching valves 18A and 18B.
When the positions N, F ₁ , F ₂ , F ₃ , and R corresponding to the positions N, F ₁ , F ₂ , F ₃ , and R of A and 18B are operated, the switch is alternatively switched to the on side. lever 26
It is assumed that the switch is switched to the off side during the operation. The contacts 25N to 25R are connected in parallel and inserted into the operation detection and discrimination circuit shown in FIG.

Operation Detection and Discrimination Circuit The clutch hydraulic pressure is controlled each time the vehicle is started and the vehicle speed is changed, and as described above with reference to FIG. Because there is, the 8th
In order to detect the operation of the shift lever 26 shown in the figure and to determine whether it is a start operation or a gear change operation, an operation detection and discrimination circuit shown in FIG. 9 is provided.

In the circuit of FIG. 9, the five contacts of the rotary switch 21 are 25N, 25F ₁ , 25F ₂ , 25F ₃ ,
25R is inserted into five parallel circuits that ground the power source through resistors, and each of the five parallel circuits is connected to the primary side of the NAND gate 27. The circuit into which the contact 25N is inserted is also connected to the trigger signal input terminal of the monostable multivibrator 28. A relay that conducts current and turns on when the emitter-grounded NPN transistor _TR1 turns on to detect a starting operation.
LR is provided and multivibrator 28
The output terminal of is connected to the base of the transistor _TR1 .

In the circuit shown in FIG. 9, the shift lever 26 shown in FIG. 8 is in any position N, F ₁ , F ₂ , F ₃ ,
One of the contacts 25N, 25F ₁ , 2 placed in R
When 5F ₂ , 25F ₃ , 25R are on the on side
Since the primary side of the NAND gate 27 is at the L level, the secondary side of the NAND gate 27 is at the H level. When the shift lever 26 is operated, all the contacts 25N-25R are switched to the OFF side, and then the shift lever 26 is moved to the next position N.
By reaching F ₁ , F ₂ , F ₃ , R, another contact point 25
Since N, 25F ₁ , 25F ₂ , 25F ₃ , and 25R are switched to the on side, when the shift lever 26 is operated, the primary side of the NAND gate 27 is changed from the L level to the H level, and then becomes the L level again. Take. Therefore, when the shift lever 26 is operated, the NAND gate 27 outputs the operation detection signal Sgp as an L level pulse.

In addition, in the circuit shown in FIG. 9, when the shift lever 26 is in the neutral position N and the contact _25N1 is switched to the on side, the primary side of the multivibrator 28 is at the L level, and from this state the shift lever 26 is any operating position F ₁ , F ₂ , F ₃ ,
When it is operated to R and the contact 25N is switched to the OFF side, the primary side of the multivibrator 28 takes an H level, and this triggers the multivibrator 28, which is determined by the resistor R ₁ and the capacitor C ₁ . The start operation determination signal Sgq is output as a pulse with a time width Ta. Therefore, the transistor _TR1 is turned on for a time Ta, and the relay LR is turned on for the same time Ta.

Hydraulic Control Circuit FIG. 2 shows a hydraulic control circuit for controlling the clutch operating hydraulic pressure in accordance with the signals Sgp and Sgq output from the operation detection and discrimination circuit of FIG. 9. The solenoids 11A and 11B of the electromagnetic valves 10A and 10B shown in FIG.
It is built in so that it can be turned on by the ON operation of TRb.

In the circuit shown in FIG.
9B, and the output end of the oil pressure sensor 20 is connected via an amplifier 29 to the negative input end of the comparators 29A and 29B, respectively. The power supply voltage Vcc is inputted to the positive input terminal of each comparator 29A, 29B by appropriately lowering it using a variable resistor which is the control oil pressure setting means.
There are two such variable resistors for A and 29B.
VRa ₁ , VRa ₂ , VRb ₁ , VRb ₂ are provided, and one of these variable resistors VRa ₁ and VRb ₁ is connected to the other variable resistor VRa 2 , VRa ₂ through the relay LR.
VRb ₂ is connected to comparators 29A and 29A, respectively, via relay contact LRS, which is turned off when relay LR is turned on.
29B. Therefore, the voltage set by the variable resistors VRa ₁ and VRb ₁ during a starting operation, and the voltage set by the variable resistors VRa 2 and VRa ₂ during a gear shifting operation.
The voltage set by VRb ₂ will be input to comparators 29A and 29B, respectively.
Each of the first and second comparators 29A and 29B detects a voltage signal corresponding to the oil pressure of the oil supply circuit 4 (FIG. 1) detected by the oil pressure sensor 20 when the voltage signal corresponds to the variable resistance VRa ₁ , VRb ₁ or VRa. ₂ , H level signal when higher than the voltage set by VRb ₂
Performs Sgu and Sgv output. As shown in FIG. 10, the first comparator 29A sets the lower limit Pimin of the low oil pressure Pi to be controlled constant, and the second comparator 29B sets the upper limit Pimax of the low oil pressure Pi.
Each is to be set using a voltage conversion value.

The circuit shown in FIG. 2 also includes the circuit shown in FIG.
A monostable multivibrator 31, which is the timer means, is provided to input the operation detection signal Sgp of the NAND gate 27 to the trigger signal input terminal. Therefore, this multivibrator 31
is when the gear shift lever 26 (Fig. 8) is operated.
Operation detection signal Sgp output by NAND gate 27
is triggered, and outputs a voltage pulse with a certain time width. Of the resistors and capacitor _C2 for determining the time width of this voltage pulse, two resistors, Ra and Rb, are connected in parallel to each other.
The circuit in which the resistor Rb is inserted has the relay contact
LRS is inserted. Therefore, the relay
The time width of the above voltage pulse changes between the on state and off state of LR, and the relay contact
In the ON state of the relay LR where LRS is switched to the OFF side, a voltage pulse Sg ₁ with a time width T ₁ expressed by T ₁ ∝Ra・C ₂ ...(1) is generated, and the relay contact LRS is switched to the ON side.
When the LR is in the off state, a voltage pulse Sg ₂ with a time width T ₂ expressed as T ₂ ∝Ra·Rb/Ra+Rb·C ₂ (2) is output. As is clear from the above equations (1) and (2), T ₁ > T ₂ ...(3), and the multivibrator 28 in FIG. 9 detects the start operation and outputs the start operation determination signal Sgq. The pulse width T ₁ is set to be larger at the time.

The above-mentioned solenoid valve displacement control circuit has a first AND gate 32A which receives the output signals of the first comparator 29A and the multivibrator 31, and a first AND gate 32A which receives the output signals of the second comparator 29B and the multivibrator 31. A second AND gate 32B is provided, and the output terminal of the second AND gate 32B is connected to the base of the transistor TRb. Also, on the secondary side of the first AND gate 32A, there is another AND gate 3.
3 is provided, and each output signal of the first AND gate 32A and the second AND gate 32B is sent to the AND gate 33, and the second AND gate 3
The output signals of 2B are inverted by an inverter 34 and then inputted, and the output terminal of the AND gate 33 is connected to the base of the transistor TRa. Therefore the transistor
TRb is turned on when the signal Sgv and the signal Sg ₁ or Sg ₂ are input to the second AND gate 32B, and the second AND gate 32B outputs the H level signal Sgb. Further, in the transistor TRa, the signal Sgu and the signal Sg ₁ or Sg ₂ are input to the first AND gate 32A, and the first AND gate 32A outputs an H level signal, and the signal Sgv and the signal Sgv are input to the second AND gate 32B. When at least one of the signals Sg ₁ and Sg ₂ is not inputted and the output terminal of the second AND gate 32B is at the L level, the AND gate 33 is turned on by outputting the signal Sga at the H level.

Between AND gate 33 and transistor TRa and
An operating tool 35 is provided between the AND gate 32B and the transistor TRb, respectively, and is provided near the vehicle driver's seat.
Shock speed change switches SWa and SWb, which are the aforementioned manual switches, are inserted to ground the respective bases of transistors TRa and TRb when operated by . Therefore, when the shock shift switches SWa and SWb are operated, both transistors TRa and TRb are turned off regardless of the outputs of the AND gates 33 and 32B.

Effects of the Embodiment FIG. 11 shows the signals Sgp, Sgq, and
This is a time chart showing the output mode of Sg ₁ and Sg ₂ . An operation detection signal output as an L level voltage pulse from the NAND gate 27 shown in FIG.
Sgp is output only from the time when the shift lever 26 is operated until the time when the operation is completed, so it is extremely short-term. The voltage pulses Sg ₁ and Sg ₂ output by the multivibrator 31 shown in FIG.
As shown in (3), the time width T ₁ of the pulse Sg ₁ at the time of starting is larger than the time width T ₂ of the pulse Sg ₂ at the time of shifting. The start operation determination signal Sgq of the multivibrator 28 shown in FIG. 9 is set to have a relatively large time width Ta to control the change in the pulse widths T ₁ and T ₂ .

Depending on _{the variable resistors VRa 1 and VRb 1 for} setting the low control oil pressure at the time of starting for the first and second comparators 29A and 29B, the variable resistors for setting the low control oil pressure at the time of shifting VRa ₂ ,
The oil pressure is supposed to be set slightly higher than with VRb ₂ . Therefore, the low oil pressure Pi shown in FIG. 10 to be controlled is set slightly higher at the time of starting than at the time of shifting.

At the _time of starting the shift lever 26 shown in _{FIG .}
A signal Sg ₁ of T ₁ is output. Also, at this time, the first
Since the oil pressure of the oil supply circuit 4 shown in the figure is initially zero, both comparators 29A and 29B output a signal.
Sgu, Sgv output is not performed. Therefore, both transistors TRa and TRb are turned off, and solenoid valve 1
0A and 10B are held in the control positions shown in FIG. 1, and the clutch operating oil pressure P is maintained as shown in FIG.
first rises rapidly. A first comparator 29 sets the lower limit Pimin of the low oil pressure for which the clutch action oil pressure P is to be controlled as shown in FIG.
When the oil pressure set by A is exceeded, the comparator 29
A turns on and outputs the signal Sgu, and at this time the second comparator 29B is still in the off state and outputs the signal Sgu.
The second AND gate 32 does not perform Sgv output.
Since the output terminal of B is at the L level, the AND gate 33 outputs the signal Sga, and the transistor TRa is turned on. Therefore, the control positions of both electromagnetic valves 10A and 10B become as shown in FIG. 4, and the oil chamber 5 is blocked in the pressure regulating valve 6, so that the clutch operating oil pressure P remains constant at a low oil pressure. In this state, the oil pressure P due to oil leak etc.
If becomes lower than Pimin, the first comparator 2
Since the signal Sgu output from 9 disappears, the control positions of both electromagnetic valves 10A and 10B are switched to the positions shown in FIG. The upper limit of the oil pressure P set in the second comparator 29B by
When Pimax is exceeded, the comparator 29B turns on and outputs the signal Sgv, so the AND gate 33
As soon as the signal Sg ₁ output from
Signal Sg ₂ is output from AND gate 32B, transistor TRa is turned off, transistor TRb is turned on, and both solenoid valves 10A and 10B take the control position shown in FIG. 3, and the oil pressure P decreases to within the appropriate range. can get. As a result, the clutch operating oil pressure P is controlled to be constant at a low oil pressure _P1 as shown in FIG. 5a. Then, when time _T1 has elapsed from the start time of the start operation, the first and second AND gates 32A,
Both the output terminals of 32B become L level, both transistors TRa and TRb are turned off, and both solenoid valves 10A and 1
Since 0B takes the control position shown in FIG.
As shown in Figure a, the normal working oil pressure Pa is obtained when the oil pressure P suddenly rises and the control piston 2 of the pressure regulating valve 6 assumes the most advanced position, and after that, the pressure regulating valve 6 is relieved when the control piston 2 is in the most advanced state. Hydraulic while operating
Pa is maintained.

When shifting the shift lever 26 shown in FIG. 8 from one operating position to another operating position, the multivibrator 31 outputs a signal Sg ₂ with a time width T ₂ . Also, at this time, since the oil pressure of the oil supply circuit 4 shown in FIG. 1 was initially the normal working oil pressure Pa as shown in FIG. 5b, both comparators 2
Both 9A and 29B output signals Sgu and Sgv,
This causes the second AND gate 32B to
Since Sgb is output, transistor TRb is turned on. Therefore, first, both solenoid valves 10A, 10
The control position of B becomes as shown in FIG. 3, so that the clutch operating oil pressure P first decreases rapidly as shown in FIG. 5b. When the oil pressure P decreases to the upper limit Pimax set in the second comparator 29B,
The second comparator 29B turns off and the signal Sgv
Although the output is lost, the first comparator 29A continues to output the signal Sgu, so the transistor TRb is turned off, the transistor TRa is turned on, and both the solenoid valves 10A and 10B take the control position shown in FIG. , the clutch operating oil pressure P remains constant at a low oil pressure. In this state, the oil pressure P is controlled within the appropriate range as described for starting, so
The oil pressure is controlled to be constant at a low oil pressure _P2 as shown in FIG. 5b. As time T ₂ elapses, the oil pressure rapidly increases to the normal working oil pressure Pa, and thereafter the same oil pressure Pa is maintained, as described in the case of starting.

Since the clutch operating oil pressure P is maintained at the low oil pressure P ₁ or P ₂ for a certain period of time both when starting and when changing gears, each hydraulic clutch 3F ₁ , 3F ₂ , 3F shown in FIG. ₃ and 3R will be brought into normal operation after completing the initial engagement, and will be able to engage smoothly without any shocks. Low oil pressure P ₁ , which was to be maintained when starting, and low oil pressure, which was to be maintained when shifting.
By maintaining T ₁ which is slightly higher than P ₂ and for a longer period of time, it is possible to smoothly start the vehicle from a stopped state, which is inevitably heavier than when changing gears in which only the vehicle speed is changed. becomes.

In the above-mentioned shock shift, when starting or changing gears, if the shock shift switches SWa and SWb are operated using the operating tool 35 shown in FIG. 2 to turn off both transistors TRa and TRb, both solenoid valves 10A, 10B assumes the control position shown in FIG. 1, and when starting, the control piston 2 of the pressure regulating valve 6 rapidly advances from its most retracted position to its most forward position, resulting in a rapid rise in oil pressure P as shown in FIG. 6a. is obtained,
Further, during gear shifting, the control piston 2 is held substantially at the most forward position, so that the oil pressure P is maintained substantially at the normal operating oil pressure Pa as shown in FIG. 6b.

Effects of the Invention The hydraulic control device of the present invention having the above-mentioned structure supplies oil from the clutch oil supply circuit 4 to the oil chamber 5 behind the control piston 2 in the pressure regulating valve 6 using a first circuit that does not restrict the oil flow. 7, and by providing a first solenoid valve 10A that can intermittent the oil supply and a second solenoid valve 10B that can selectively drain oil from the oil chamber 5, these By intermittent supply of oil to the oil chamber 5 and intermittent drain of oil from the oil chamber 5 by the two electromagnetic valves 10A and 10B, the clutch operating hydraulic pressure is controlled to ensure smooth engagement of the hydraulic clutch as described above. This system eliminates the restriction that was provided in conventional hydraulic control devices of this type, so even if the oil temperature, engine speed, and therefore pump speed change, In addition to being able to control the hydraulic pressure applied to the hydraulic clutch as intended, it is also useful when scooping earth and sand from the ground with a bucket or fork, when towing heavily with a vehicle, when escaping from muddy or wet fields, etc. When it is necessary to start the vehicle like a dart or change gears, oil is rapidly supplied to the oil chamber 5 through the first solenoid valve 10A with the oil drain from the oil chamber 5 blocked by the second solenoid valve 10B. It is assumed that a so-called shock shift can be performed by allowing the air to flow into the air.

The hydraulic control device of the present invention also operates the hydraulic pressure setting means VRa ₁ , VRa ₂ ,
The clutch operating pressure detected by the hydraulic pressure sensor 20 and the control set in the hydraulic pressure setting means are used to maintain the low control hydraulic pressure set by VRb ₁ and VRb ₂ to obtain smooth engagement of the hydraulic clutch. Hydraulic pressure comparison means 29A, 29B
This is obtained by controlling the displacement of the solenoid valves 10A and 10B in accordance with the third electric signals Sgu and Sgv output by the comparison means, so that the pressure regulating valve 6 for setting the clutch working oil pressure is A pair of solenoid valves 10A, 10 that control the supply and discharge of oil to the rear of the control piston 2 without going through a throttle.
B, the position of the control piston 2, which determines the clutch action oil pressure, is accurately controlled to the desired position by the above-mentioned oil pressure feedback control, allowing for shock-free engagement of the hydraulic clutch. The hydraulic pressure change characteristics to be achieved should be obtained appropriately.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view and hydraulic circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram of an electric control circuit provided in the embodiment, and FIGS. Hydraulic circuit diagrams depicting the main parts of Figure 1 in different states, Figures 5a and b and Figures 6a and b are schematic graphs showing the operation of the same embodiment, and Figure 7 is a diagram showing the same implementation. FIG. 8 is a schematic mechanical diagram of a portion of the example; FIG. 9 is a circuit diagram of another electric control circuit provided in the example; FIG. 10 2 is an explanatory diagram showing an example of settings in the electric control circuit shown in FIG. 2, and FIG. 11 is a time chart illustrating the operation timing of circuit elements in the electric control circuit shown in FIGS. 2 and 9. DESCRIPTION OF SYMBOLS 1... Oil pressure setting spring, 2... Control piston, 3F ₁ , 3F ₂ , 3F ₃ , 3R... Hydraulic clutch, 4... Oil supply circuit, 5... Oil chamber, 6... Pressure regulating valve, 7... First circuit, 8...Oil tank, 9...
Second circuit, 10A...First solenoid valve, 10B...
...Second solenoid valve, 11A, 11B... Solenoid, 14... Valve body, 15... Annular step, 18A,
18B... Solenoid switching valve, 20... Oil pressure sensor,
21... Rotary switch, 26... Gear shift lever (shift operating means), 27... NAND gate, 28
...Monostable multivibrator, 29A, 29B
... Comparator (hydraulic comparison means), 31 ... Monostable multivibrator (timer means), 32
A, 32B...AND gate, 33...AND gate, 35...operation tool, TRa, TRb...transistor, VRa ₁ , VRa ₂ , VRb ₁ , VRb ₂ ...variable resistor (control hydraulic pressure setting means), SWa , SWb...Shock shift switch (manual switch).

Claims (1)

[Scope of Claims] 1. A control piston that receives the tip of a hydraulic pressure setting spring and increases the strength of the hydraulic pressure setting spring by advancing the control piston is provided so as to be able to advance to a regulated position, and a hydraulic clutch is provided behind the control piston. In a hydraulic control device that is equipped with a pressure regulating valve that forms an oil chamber for applying hydraulic pressure from an oil supply circuit to a hydraulic clutch in a hydraulic transmission, the oil supply circuit 4 is connected to the oil chamber 5 through a throttle. A first circuit 7 that connects the oil chamber 5 to the oil tank 8 and a second circuit 9 that connects the oil chamber 5 to the oil tank 8 are provided.
and a first solenoid valve 10A each having a position for making each circuit conductive and a position for cutting off each circuit.
and that a second solenoid valve 10B is inserted and installed, and B. A hydraulic pressure sensor 20 that detects the hydraulic pressure of the oil supply circuit 4 and generates a first electric signal, and a normal working hydraulic pressure set by the pressure regulating valve 6. control oil pressure setting means VRa ₁ , VRa ₂ , VRb ₁ , VRb ₂ that can set a lower control oil pressure than the control oil pressure and outputs a second electric signal corresponding to the set control oil pressure;
Hydraulic pressure comparison means 29A, 29B receive first and second electric signals from the above-mentioned oil pressure sensor and control oil pressure setting means, compare the values of both electric signals, and output a third electric signal according to the magnitude thereof.
, a timer means 31 that outputs a fourth electric signal for a set time when the shift operation means 26 for the hydraulic clutch type transmission is operated, and a third electric signal from the above-mentioned oil pressure comparison means and timer means.
and a solenoid valve displacement control circuit 32A that controls the displacement of the first and second solenoid valves 10A and 10B in response to the third electric signal so that the control oil pressure is maintained when the fourth electric signal is input. 32
A hydraulic control device for a hydraulic clutch type transmission, characterized in that B, 33, TRa, and TRb are provided. 2. The hydraulic control device according to claim 1, wherein the first and second electrical signals are input into the electromagnetic valve displacement control circuit independently of the third electrical signals from the hydraulic pressure comparison means 29A and 29B. Second solenoid valve 10
A hydraulic clutch type transmission, characterized in that manual switches SWa and SWb are provided to displace A and 10B to a position where the first circuit 7 is made conductive and the second circuit 9 is cut off. Hydraulic control device for.