JPS61135834A - Hydraulic driven car speed control device - Google Patents

Abstract

PURPOSE:To allow accelerating and decelerating feelings to be acquired as required by enabling the extent of a follow up action time for an output signal against a car speed command signal, to be changed based on the fast or slow operating speed of a car speed set up means. CONSTITUTION:A hydraulic transmission 10 includes a variable displacement hydraulic pump 11 and a variable displacement hydraulic motor 12. These are connected together with hydraulic pipes 13g and 13b. A shaft 11a of the hydraulic pump 11 is connected with the output shaft 1a of an engine and is rotated by the engine 1. And shaft 12a of the hydraulic motor 12 is connected with a driving wheel of wheels. A pump swash plate servo device 14 controls the direction of delivery of hydraulic oil and the rate of flow of the hydraulic pump 11. A motor swash plate servo device 15 is for controlling a suction flow rate of hydraulic oil to the hydraulic motor 12 allowing the tilt angle of the swash plate 12b to be controlled base on a motor capacity change signal from a control circuit 20.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vehicle speed control system for a hydraulically driven vehicle having a hydraulic transmission.

[Conventional technology]

A hydraulic transmission in a hydraulically driven vehicle such as a tractor or grader has a variable displacement hydraulic pump (swash plate pump) driven by the engine on the engine side, and a variable displacement hydraulic pump (swash plate pump) on the drive shaft side that drives the wheels or tracks of the vehicle. It has a variable displacement hydraulic motor (swash plate motor), and transmits the driving force of the engine to the wheels or tracks by guiding the hydraulic oil discharged from the swash plate pump to the swash plate motor via hydraulic piping, By controlling the inclination angles of the swash plates of the hydraulic pump and the hydraulic motor, the discharge amount of the hydraulic pump and the suction amount of the hydraulic motor per revolution of the engine are adjusted, and the speed is changed.

The vehicle speed of such a hydraulically driven vehicle is set by the amount of operation of the vehicle speed setting lever and the brake pedal, and the speed of change is determined by the speed of the mechanical actuator that controls the actual speed change or the response speed of the control device in response to changes in the vehicle speed setting lever. The rate was determined by Cζ.

[Problem that the invention seeks to solve]

Therefore, in a system with good responsiveness, if the vehicle speed setting lever is operated rapidly, a large shift shock will occur due to sudden gear changes, and in a system with less shock, sudden shifts will not be possible, resulting in poor steering sensation. Ta.

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a vehicle speed control system for a hydraulically driven vehicle that can achieve desired acceleration/deceleration according to the operations of an operator.

[Means for solving problems]

According to the present invention, a vehicle speed command signal is formed in response to each operation of the vehicle speed setting means and the brake operating means, and when this signal is applied to at least one of the hydraulic pump and the hydraulic motor of the hydraulic transmission, the volume is changed. Vehicle speed control method for hydraulically driven vehicles that is output as one of the signals for +c
b, the vehicle speed command signal is input, and the degree of temporal follow-up of the output signal with respect to the input signal is changed in accordance with the speed of operation of the vehicle speed setting means, etc.

[Effect]

Since the degree of temporal follow-up of the output signal to the vehicle speed command signal (input signal) is changed depending on the speed at which the vehicle speed setting means is operated, etc., the intention of the operator is more reflected in the vehicle speed command signal, and the desired acceleration/deceleration is achieved. You can feel it.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment of a drive system to which a vehicle speed control method for a hydraulically driven vehicle according to the present invention is applied. In the figure, a hydraulic transmission 10 is provided with a variable displacement hydraulic pump (hereinafter simply referred to as a hydraulic pump) 11 and a variable displacement hydraulic motor (hereinafter simply referred to as a hydraulic motor) 12, which are connected by hydraulic pipes 13a and 13b. The shaft 11a of the hydraulic pump 11 is connected to the output shaft 1a of the engine 1, and is rotationally driven by the engine 1. A shaft 12a of the hydraulic motor 12 is connected to a drive wheel of a vehicle (not shown), and is configured to rotationally drive the drive wheel.

Generally, variable displacement hydraulic pumps are suitable for applications where the output shaft torque is constant, and variable displacement hydraulic motors are suitable for applications where the output is constant; however, in this embodiment, the hydraulic pump 11. Both hydraulic motors 12 are of variable displacement type, and have the characteristics of both. Moreover, both the hydraulic pump ll and the hydraulic motor 12 have swash plates 11b and 12b.
The pump is a variable displacement pump and a variable displacement motor that change the displacement by changing the inclination angle of the pump.

The pump swash plate servo device 14 controls the discharge direction and discharge amount of hydraulic fluid from the hydraulic pump 11, and the control device 2
The direction and angle of inclination of the swash plate 11b are controlled by changing the polarity and magnitude of the pump capacity change signal SP from 0 to 0. The hydraulic pump 11 discharges an operating wave with a direction and flow rate depending on the direction and angle of inclination of the swash plate 11b. In addition, hydraulic pump 1
1 discharges hydraulic oil into the hydraulic pipe 13a@ when moving forward,
When traveling in reverse, the direction of inclination of the swash plate 11b is controlled so that the oil is discharged to the side of the hydraulic pipe 13b. The motor swash plate servo device 15 is for controlling the amount of hydraulic fluid sucked into the hydraulic motor 12, and receives a motor capacity change signal S from the control device 20.
The inclination angle of the swash plate 12b of the hydraulic motor 12 is controlled according to m. The rotational direction and torque of the hydraulic motor 120 change depending on the direction and amount of inflowing hydraulic oil (suction amount). Therefore, by controlling the discharge amount of the hydraulic pump 11 and the suction amount of the hydraulic motor 12, it is possible to control the speed change of the transformer shifter 10.

The control circuit 20 includes a potentiometer 24. which generates a signal corresponding to the position of a vehicle speed setting lever 21 for setting the speed of the vehicle. A potentiometer 25 generates a signal corresponding to the position of the brake pedal 22, a potentiometer 27 generates a signal corresponding to the position of the throttle lever 23, and an engine rotation sensor generates a pulse signal corresponding to the rotation speed of the engine 1. A pump capacity change signal sr inputs various signals of 26, performs calculations described later from these signals, and controls the capacities of the hydraulic pump 11 and the hydraulic motor 12.
and generates the motor capacity change signal Sm.Next, the control circuit 20 will be explained with reference to the block diagram shown in FIG. This control circuit 20 includes a potentiometer 2
Vehicle speed control calculation circuit 3 to which signals are applied from 4 and 25
0, an automatic shift calculation circuit 40 to which signals are applied from an engine rotation sensor 26 and a potentiometer 27, a servo drive circuit 50, and the like.

The vehicle speed control calculation circuit 30 includes an absolute value circuit 31, a forward/reverse motion discrimination circuit 32, a vehicle speed pattern generation circuit 33, a modulation circuit 34, a vehicle state detection circuit 33, etc.
In response to the operation of the vehicle speed setting lever 21 and the brake pedal 22, an automatic shift suppression signal V and a secondary forward/reverse switching signal KFiL2 are output, which suppress the maximum value of an automatic shift signal v2, which will be described later.

The potentiometer 24 applies a signal corresponding to the operating position of the vehicle speed setting lever 21 to the absolute value circuit 31 and the forward/reverse motion discrimination circuit 32 . Note that the input signal is a voltage S when the lever 21 is at the highest forward speed position.

This is a signal that has a voltage of -8o when the vehicle is at the maximum reverse speed position and a voltage of O when it is at the neutral position.

The absolute value circuit 31 takes the absolute value of the input signal and applies that signal to the vehicle speed pattern generation circuit 33 and the vehicle state detection circuit 35 as a lever stroke signal SL. The forward/reverse motion discrimination circuit 32 discriminates the polarity of the input signal, and when it is positive, it becomes ``1'', and when it is negative, it becomes -1''. Add to 35.

The potentiometer 25 sends a brake signal SB corresponding to the amount of depression of the brake pedal 22 to a vehicle speed pattern generation circuit 33.
and vehicle condition detection circuit 35). The brake signal sB is a signal that has a voltage So when the brake pedal 22 is at the neutral position N and a voltage O when the brake pedal 22 is at the maximum depression position F.

The vehicle speed pattern generation circuit 33 generates a lever stroke signal s.
It has various pattern functions for L and brake signal SR, which can be appropriately selected according to a state signal applied from a vehicle state detection circuit 35, which will be described later. The speed command signal Sl) is converted.

Here, the specific operation of the vehicle speed pattern generation circuit 33 will be explained together with the description of the vehicle state detection circuit 35.

In addition to the lever stroke signal sL, the next forward/backward command signal KFRI, and the brake signal SB, the vehicle state detection circuit 35 receives a primary actual vehicle speed command signal S1 output from the vehicle speed pattern generation circuit 33, and a primary actual vehicle speed command signal S1 output from the mode rate circuit 34. A secondary actual vehicle speed command signal S, a secondary forward/reverse command signal KFR2, and a voltage signal vNl corresponding to the engine rotation speed output from the automatic shift calculation circuit 400 frequency-voltage converter 41 are input. .

The vehicle state detection circuit 35 detects various states of the vehicle from these input signals, such as acceleration/deceleration by only operating the vehicle speed setting lever, acceleration/deceleration by only the brake pedal 22, acceleration/deceleration by a combination of both, and further determines the vehicle speed setting. A state in which parameters include forward/reverse switching by lever operation alone, forward/reverse switching by both combinations, commanded direction of travel, actual direction of travel, amount of operation of the vehicle speed setting lever 21 and brake pedal 22, and each operation speed (slowness or speed of operation). and outputs status signals indicating these states to the vehicle speed pattern generation circuit 33 for vehicle speed pattern selection. Output to circuit 34.

Next, the patterns selected by the vehicle speed pattern generation circuit 33 for each vehicle state will be explained.

(1) Pattern when only the vehicle speed setting lever 21 is operated The primary actual vehicle speed command signal S is generated according to the pattern shown in the graph of FIG. 3 in response to the input of the lever stroke signal sL.
1, that is, 81- to 1・(SL-f)+e (r≦SL≦h)S
, = to -(sL-h)+r (h<sL≦So)
Output. Note that normally Ks<Kz, which facilitates adjustment of vehicle speed at low speeds.

In addition, the lever stroke signal sL becomes h within a preset time (for example, 0.6 seconds; the time during which the secondary actual vehicle speed command signal S2 does not exceed point f by the modulation lane 21 circuit 34, which will be described later).
If the operation is performed beyond the point C, as shown by the two-dot chain line in FIG. Improves operability over the entire area by setting a constant slope up to the point.

C) Pattern when only the brake pedal 22 is operated When the vehicle speed setting lever 21 is fixed at the highest speed position and only the brake pedal 22 is operated, the graph in FIG. 4 shows the pattern for the input of the brake signal SB. According to the pattern, the primary actual vehicle speed command signal S1, that is, S1=' is 3(SB-i)+m (i≦SB≦S's
) Sl=4(SB-J)+l (J≦SB<
1) Output S1=KSSIl<k≦SBj). In general, there is a relationship of 4>Kg>Ks, which improves the speed adjustability at the beginning of the pedal stroke and the slow speed controllability immediately before stopping. Further, k is the point at which the primary actual vehicle speed command signal S1 becomes O, but by setting k > 0, it is possible to add some margin to the depression side, and the play amount D (=8°-8' o) is provided. Further, the inclination may be changed in the A direction or the B direction in the coffin 4 in accordance with the speed of depression.

(3) Patterns when the vehicle speed setting lever 21 and the brake pedal 22 are operated in combination When the combination operation is performed, two modes of patterns are generated using a signal corresponding to the actual vehicle speed. Here, the actual vehicle speed equivalent signal is a signal obtained by multiplying the secondary actual vehicle speed command signal S output from the modulation circuit 34 by a voltage signal vNE corresponding to the engine speed, and further multiplying by an appropriate gain. be.

When the signal corresponding to the actual vehicle speed is in the high speed range ξ
The final output is obtained by multiplying the primary actual vehicle speed command signal corresponding to the lever stroke signal sL exceeding the point h in FIG. 3 by the primary actual vehicle speed command signal corresponding to the brake signal S in FIG. 4. This allows the feeling of a decrease in vehicle speed due to braking to match the actual vehicle speed.

(iυ When the actual vehicle speed equivalent signal is in the low speed range or when the lever stroke signal sL is below point h, the characteristics from the primary actual vehicle speed command signal corresponding to the lever stroke signal sL1 to the brake signal sB (
The two-dot chain line graph (So-st) in FIG. 4 is subtracted to obtain the final output. This improves instantaneous stopping at low speeds (the feeling of stopping instantly when braking). On the right, if the result of subtraction is a negative command, the limiter will cut it off.

The modulation circuit 34 uses a state signal applied from the vehicle state detection circuit 35 to determine the temporal followability of the secondary actual vehicle speed command signal S1, which is an output signal for the primary actual vehicle speed command signal S input from the vehicle speed pattern generation circuit 33. The primary forward/reverse command signal KFRI is input to the forward/reverse discrimination circuit 32Th.
This is to adjust the change timing of the secondary forward/reverse command signal KFR□, which is an output signal for the motor.

Here, the specific operation of the modinilate circuit 34 will be explained.

(1) Primary actual vehicle speed command signal S input when accelerating with vehicle speed setting lever 21! When both the current output secondary actual vehicle speed command signal S and the output signal S are at least 0 point or at most d point in FIG. 5, the output signal follows the input signal ζζ at a constant rate over time. That is, if the secondary actual vehicle speed command signal S3 is C at a certain point in time t=Q, and the -th actual vehicle speed command signal S1 is S·(100%''), then the secondary actual vehicle speed command signal S is t. =0.4, which matches the primary actual vehicle speed command signal S1.Furthermore, if the secondary actual vehicle speed command signal S at t=Q is equal to or higher than C or the primary actual vehicle speed command signal does not reach 8., - After a delay time corresponding to the difference between the next actual vehicle speed command signal S! and the secondary actual vehicle speed command signal S8 tciiIi
j are in agreement. - The same applies to the case where the next actual vehicle speed command signal S1 is equal to or less than d.

A primary actual vehicle speed command signal S1 and a secondary actual vehicle speed command signal S,
When there is a relationship lζ other than the above, the secondary actual vehicle speed command signal S8 is given by the following arithmetic expression.

dS.

--to @ (81-8t) ”・(1)t Here, K is a constant selected based on the required acceleration feeling,
Depending on the speed of operation of the vehicle speed setting lever 21, iζ is changed as follows.

Operation amount: ni = large medium; ni 0 = medium slow; KG = small (2 deceleration by the vehicle speed setting lever 21 - the next actual vehicle speed command signal S1 and the secondary actual vehicle speed command signal S2 are both 6th
Below point e in the figure, the secondary actual vehicle speed command signal S3 follows at a constant rate with respect to time, and its function is the same as during acceleration shown in FIG. However, the set value of the zero point and the rate of change with respect to time are distinguished from those during acceleration.

On the other hand, the -th actual vehicle speed command signal 5ltd and the secondary actual vehicle speed command signal S! When the relationship is other than the above, the secondary actual vehicle speed command signal S2 is given by the following arithmetic expression.

dS intention""K1(S+-8g)...C2)t Here, Kl is a constant selected based on the required deceleration feeling,
Depending on the speed of operation of the vehicle speed setting lever 21, the speed is changed as follows.

Operating amount: +1" during large operation; Kl Maro, Medium, Loose, 2, K1: Small (3) When the amount of deceleration brake operation by the brake pedal 22 is within the vicinity of the depression end (90% of the total stroke), follow the above formula However, K is fixed at a large level. When the amount of brake operation exceeds the vicinity of the dark end, the secondary actual vehicle speed command signal follows the primary actual vehicle speed command signal without delay.

(4) 1° change timing in the secondary forward/reverse command signal when switching forward/reverse The secondary forward/reverse command signal KFR□ is the secondary actual vehicle speed command signal S
! At the timing when becomes 0, -next forward/forward command signal KFR
Follow □ without delay. Secondary actual vehicle speed command signal 8m
is maintained at the current value without being influenced by the primary forward/backward command signal KFR□ except when the position is O.

(5) Deceleration when switching forward/backward (operate only vehicle speed setting lever 21) Secondary forward/backward command signal KFR2 and − next forward/backward command signal,
When □ does not match and the secondary actual vehicle speed command signal S1 is not O, it is uniquely determined by the secondary actual vehicle speed command signal S- and the primary actual vehicle speed command signal Sl according to the relationship shown in the graph of FIG. Reduce the secondary actual vehicle speed command signal S according to the rate of change,
Secondary actual vehicle speed command signal S! When becomes 0, the secondary forward/reverse command signal KFR2 is changed as described above, and thereafter the vehicle is accelerated according to case (1).

(6) Deceleration when switching forward/backward (combined operation of vehicle speed setting lever 21 and brake pedal 22) The case where the brake pedal 22 is operated during the deceleration operation in the above case G) is the result of 7 in the vehicle reduction in Figure 7. Eliminate the reduction part,
At the same time as the deceleration rate is set to 6, brake pedal 2 is decelerated.
The reduction rate is increased by 6 according to the depression amount number ζ of 2. When the amount of depression of the brake pedal 22 reaches or exceeds the vicinity of the depression end, the output is set to 0 at that point.

This operation normally allows driving with very little shock when switching forward or backward, and can also be used in conjunction with the brake pedal 22 to perform a sudden stop.

Fig. 8<8) to (d) are the −th actual vehicle speed command signal S, respectively.
1. This is a signal waveform diagram showing an example of the next track reverse command signal KFRI, the secondary actual vehicle speed command signal S, and the command signal KFR2. Then, switch from forward/backward with a sudden change from high speed forward to high speed reverse, then suddenly from high speed reverse to low speed, then slowly from low speed to speed O, and finally from speed 0 to forward speed. Temporal followability of the secondary actual vehicle speed command signal S3 with respect to the above-mentioned secondary actual vehicle speed command signal S1 and timing of change of the secondary forward/reverse command signal KFR2 with respect to the primary forward/reverse command signal KFR□ when suddenly operating to high speed, etc. It shows about.

In this way, the moderator circuit 34 outputs the -th actual vehicle speed command signal Sl and the primary forward/backward movement according to the state signal applied from the vehicle state detection circuit 35 according to the current vehicle state, the type and amount of operation, the operation speed, etc. O The secondary actual vehicle speed command signal S2 output from the modulation circuit 34 is a negative input of the adder 36. A secondary forward/backward command signal KFR2 is applied to the servo drive circuit 50.

A signal S corresponding to the maximum speed command signal is added to the positive input of the adder 36, and the adder 36 adds these two manual forces to produce an automatic shift suppression signal v (=S).

-88).

On the other hand, the automatic speed change calculation circuit 40 uses the frequency-voltage converter 4
1, an adder 42, a damper 43, and a PID compensation circuit 44, and forms a shift signal v8 based on signals from an engine rotation sensor 26 and a potentiometer 27.

The engine rotation sensor 26 applies a pulse signal with a number of pulses corresponding to the number of rotations of the engine 1 to a frequency-voltage converter 4, and the frequency-voltage converter 41 converts the input pulse signal into a voltage signal vNε corresponding to the number of pulses. and is added to the positive input of the adder 42. Note that the signal VNI has a voltage of 11.58 when the engine speed is 2300 rpm, for example.
・This is the signal.

The potentiometer 27 outputs a signal vrg corresponding to the operating position of the throttle lever 23. For example, when the lever 23 is at a position that commands an engine speed of 210 Orpm, the signal VTR becomes a signal with a voltage of 10.5 So. This signal VTII is applied to the negative input of adder 42. Further, So is added to the other positive input of the adder 42, and the adder 42 adds these three human forces and outputs the sum signal v1, vt=Se+vNE-V7i to the clamper 43.

When the input signal Vl is 80 or more, the clamper 43
, when it is less than 0, it is limited to 0, and this signal is used as PID
It is output as an automatic speed change signal V via the compensation circuit 44. The PID compensation circuit 44 is provided to prevent engine rotation and vehicle speed from becoming unstable during automatic gear shifting.

This automatic speed change signal V is applied to the positive input of the adder 51. The negative input of the adder 51 is the vehicle speed control calculation circuit 30 power 1.
The adder 51 adds the two human forces and outputs a signal Vm (=Vt-V) as the final shift signal.

The servo drive circuit 50 controls the discharge direction and discharge amount of the hydraulic pump 11 of the transmission 10 and the suction amount of the hydraulic motor 12, and adjusts the pump amount so that the speed ratio corresponds to the speed change signal v3 added from the adder 51. A change signal Sp and a motor capacity speed change signal Sm are output. Further, this servo drive circuit 50 determines the polarity of the pump capacity change signal Sp in accordance with the polarity of the secondary forward/backward command signal KI'R2. The pump capacity change signal Sp is applied to the coils 52a and 52b of the solenoid valve 52 that operates the pump swash plate servo device 14, and the motor capacity change signal Sm is applied to the coil 53a of the solenoid valve 53 that operates the motor swash plate servo device 15. It will be done.

Therefore, the pump swash plate servo device 4 and the motor swash plate servo device 15 control the inclination angle of the swash plate according to the signals sp and sm, thereby controlling the discharge amount of the hydraulic pump 11 and the hydraulic motor 12.
, and controls the transmission 10 to change its speed.

Note that the vehicle speed pattern generation circuit 33 and the modulation circuit 34 are not limited to the above-mentioned embodiment 1ζ, and various configurations are possible, and the point is that the operator's will (particularly the speed at which the vehicle speed setting lever 21 is operated) determines the speed of the vehicle speed command signal. Any device that forms a signal so as to reflect the base ζ may be used.

〔Effect of the invention〕

As explained above, according to the present invention, desired acceleration/deceleration can be performed according to the operation of the operator, and the maneuverability of the vehicle can be improved.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a drive system to which a vehicle speed control system for a hydraulically driven vehicle according to the present invention is applied, and FIG. 2 is a block diagram showing an embodiment of a control circuit according to the present invention. The right side of Figure 3 and Figure 4 are graphs used to explain the vehicle speed pattern generation circuit according to the present invention, and Figures 5, 6, and 7 are graphs used to explain the modulate circuit according to the present invention, respectively. The graphs used in Figures 8 (a) to 8 (d) are signal waveform diagrams showing the outputs of various parts of the circuit of Figure 2 used to explain the present invention. DESCRIPTION OF SYMBOLS 1... Engine, 10... Hydraulic transmission, 11... Variable capacity hydraulic pump, 12... Variable capacity hydraulic motor, 14... Pump swash plate servo device, 15
-Motor swash plate servo device, 20.-Control circuit, 21.
・Vehicle speed setting lever, 22・-brake pedal, 23・・
- Throttle lever, 24, 25, 27... Potentiometer, 26... Engine rotation sensor, 30... Vehicle speed control calculation circuit, 33... Vehicle speed pattern generation circuit, 3
4...modulation circuit, 35-vehicle state detection circuit,
40... Automatic speed change calculation circuit, 50... Servo drive circuit.

Claims (4)

[Claims] (1) One of the signals for forming a vehicle speed command signal in response to each operation of the vehicle speed setting means and the brake operating means, and using this signal to change the displacement volume of at least one of the hydraulic pump and the hydraulic motor of the hydraulic transmission. In the vehicle speed control method for a hydraulically driven vehicle, the vehicle speed command signal is inputted, and the degree of temporal tracking of the output signal with respect to the input signal is changed according to the speed of operation of the vehicle speed setting means. A vehicle speed control system for hydraulically driven vehicles. (2) One of the signals for forming a vehicle speed command signal in response to each operation of the vehicle speed setting means and the brake operating means, and using this signal to change the displacement volume of at least one of the hydraulic pump and the hydraulic motor of the hydraulic transmission. In a vehicle speed control method for a hydraulically driven vehicle, the vehicle speed command signal is inputted, and the speed of operation of the vehicle speed setting means, each operation position of the vehicle speed setting means and the brake operation means, and the current output are determined. A vehicle speed control method for a hydraulically driven vehicle, characterized in that the degree of temporal follow-up of an output signal to the input signal is changed in accordance with a vehicle speed command signal. (3) One of the signals for forming a vehicle speed command signal in response to each operation of the vehicle speed setting means and the brake operating means, and using this signal to change the displacement volume of at least one of the hydraulic pump and the hydraulic motor of the hydraulic transmission. In a vehicle speed control method for a hydraulically driven vehicle, the vehicle speed command signal is inputted, the function of the output signal with respect to the input signal is changed according to the operating state of the vehicle speed setting means and the brake operation means, and the 1. A vehicle speed control method for a hydraulically driven vehicle, characterized in that an output signal is input, and the degree of temporal follow-up of the output signal to the input signal is changed in accordance with the speed of operation of the vehicle speed setting means. (4) Each operation state of the vehicle speed setting means and the brake operating means includes an operation type indicating that only the vehicle speed setting means is being operated, only the brake operating means is being operated, and these means are being operated simultaneously, and the vehicle speed setting means the speed of operation,
Claim (3), which is determined by a combination of each operation position of the vehicle speed setting means and the brake operation means and an actual vehicle speed equivalent signal or a signal indicating whether the actual vehicle speed is a high speed range or a low speed range. Vehicle speed control method for hydraulically driven vehicles.